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Title: Elements of the Theory and Practice of Chymistry, 5th ed.
Author: Macquer, Pierre Joseph
Language: English
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    ELEMENTS

    OF THE

    THEORY AND PRACTICE

    OF

    CHYMISTRY·


    Translated from the FRENCH of

    M. MACQUER,

    Member of the Royal Academy of Sciences, and Professor
    of Medicine in the University of PARIS.


    The FIFTH EDITION.


    EDINBURGH:

    Printed for ALEXANDER DONALDSON; and sold at his
    Shop, No. 48, East Corner of St. Paul's Church-Yard,
    London; and at Edinburgh.

    M. DCC. LXXVII.



THE AUTHOR's PREFACE.


An hundred and fifty years are scarce elapsed since the clouds of
prejudice, which had long overspread the world, began to clear up,
and men were convinced, by cultivating the Sciences, and attending
to Nature, that no fanciful hypotheses would ever lead them to the
true causes of those various phenomena that incessantly and every
where meet the observer's eye; but that the narrow limits of the
human understanding confine the course of our researches to one
single path; namely, that of Experiment, or the Use of our Senses.
Yet, in this short period, Natural Philosophy hath risen to a high
pitch of improvement, and may with truth be said to have made much
greater advances towards perfection, since the experimental method was
introduced, than in the many ages before.

This is true with regard to every branch of Natural Philosophy; but
more particularly with regard to Chymistry. Though this Science cannot
be said to have ever existed without experiments, yet it laboured under
the same disadvantages with the rest; because those who studied it made
all their experiments with a view to confirm their own Hypotheses, and
in consequence of principles which had no foundation whatever, but in
their wild imaginations.

Hence arose that enormous heap, that incongruous jumble of facts, which
some time ago constituted all the knowledge of Chymists. Most of them,
and especially those who assumed the pompous title of Alchymists,
were persuaded that all the Metals were no other than Nature's rude
unfinished essays towards making Gold; which, by means of due coction
in the bowels of the earth, advanced gradually towards maturity, till
at last they were perfectly converted into that beautiful and precious
Metal.

On this principle, which, if not demonstrably false, is at least
utterly destitute of proof, and unsupported by a single observation,
they attempted to finish what Nature had begun, by procuring to the
imperfect Metals this much desired coction. To attain it they made
an infinite number of experiments and trials; which all conspired to
detect the falsity of their system, and to satisfy men of sense, that
the methods they employed were very far from answering the purpose.

However, as facts always promote the knowledge of Nature, it happened
that those experiments, though quite useless with regard to the end for
which they were originally made, proved the occasion of several curious
discoveries.

These lucky consequences of their mistaken labours raised the courage
of the Chymists, or rather Alchymists, who looked upon every such
instance of success as a new step towards the Grand Work, and greatly
increased the fond opinion they entertained of themselves, and of
their Art, which, on that account, they set up very high above all
other Sciences. Nay, they carried this notion of superiority so far,
as to hold the rest of mankind unworthy, or incapable, of rising to
such sublime knowledge. In consequence thereof Chymistry became an
occult and mysterious Science; its expressions were all tropes and
figures, its phrases metaphorical, and its axioms so many enigmas: in
short, an obscure unintelligible jargon is the justest character of the
Alchymistic Language.

Thus, by endeavouring to conceal their secrets, those gentlemen
rendered their Art useless to mankind, and brought it into deserved
contempt. But at length the genius of true philosophy prevailed in
Chymistry, as well as in the other Sciences. Some great men arose, who
had generosity enough to think their knowledge no otherways valuable
than as it proved of service to Society. They did their utmost to
introduce both the knowledge and the practice of many important
secrets, till then of no use; they drew aside the veil which hid the
charms of Chymistry; and that Science emerging from the profound
obscurity, in which it had for many ages lain concealed, gained the
admiration of the world as soon as it appeared in open day. Several
societies of ingenious men were formed in the most learned countries
of Europe, who vied with one another in their labours to execute the
noble scheme, and assisted each other by mutually communicating their
discoveries. Chymistry made the most rapid progress, enriching and
perfecting the Arts derived from, or depending on it. In a word, it
put on a new face, and became truly worthy of the title of Science;
founding its principles and its processes on solid experiments, and on
just consequences deduced from them.

Since that time the Art is become so extensive, by the numerous
discoveries which Chymists have already made, and are daily making,
that large volumes are required to contain a complete Treatise on the
subject. In short, Chymistry may now, in some degree, be compared
to Geometry: each of these Sciences takes in a most ample field of
inquiry, which every day enlarges very considerably; from each are
derived several Arts, not only useful but even necessary to Society;
each hath its Axioms and its undeniable principles, either demonstrated
from internal evidence, or founded on constant experience; so that
the one, as well as the other, may be reduced to certain fundamental
truths, on which all the rest are built. These fundamental truths
connected together, and laid down with order and precision, form what
we call the Elements of a Science. It is well known that there are
many such works relating to Geometry, but it is not so with regard to
Chymistry; there being very few books which treat of this Science in an
Elementary manner.

Yet it must be owned, that performances of this kind are exceedingly
useful. Many who have a relish for the Sciences, but have not leisure
to read elaborate Works which treat of them minutely, are glad to meet
with a book from which, without sacrificing too much of their time,
or neglecting their ordinary business, they may obtain a taste or
just notion of a Science that is not their principal study. Those who
incline to go farther, and learn more, may, by reading an elementary
tract, be enabled to understand Authors, who, as they commonly write
only for proficients in the Art, are obscure and hardly intelligible
to mere beginners. Nay, I presume to say, that an Elementary Treatise
of Chymistry may prove a very useful book, even to those who have made
some progress in the Science: for as it contains only the fundamental
propositions, and indeed is an abstract of the whole Art, it may help
them to recollect the most important parts of what they have read in
many different works, and fix in their memoirs the most essential
truths, which might else be either confounded with others, or entirely
forgot. And these are the motives which determined me to compose the
Work which I now offer to the Public.

The general Plan on which I proceed is to suppose my Reader an absolute
Novice in Chymistry; to lead him from the most simple truths, and such
as imply the lowest degree of knowledge, to such as are more complex,
and require a greater acquaintance with Nature. This order, which I
have laid down for my rule, hath obliged me to begin with examining
the most simple substances that we know, and which we consider as the
elements whereof others are composed; as, by knowing the properties of
these elementary parts, we are naturally led to those of their several
combinations; and, on the other hand, in order to know the properties
of compound bodies, it is necessary we should be first acquainted with
the properties of their principles. The same reason induced me, when
enquiring into the properties of one substance, to take no notice of
those which relate to any other substance not treated of before. For
example: as I treat of Acids before Metals, I say nothing under the
head of those Acids concerning their power of dissolving metals; that I
defer till I come to the subject of Metals: and thus I avoid speaking
prematurely of a substance with which I suppose my Reader wholly
unacquainted. And this method I was so much the more easily induced to
follow, that I know of no Chymical book written on the same Plan.

After discoursing of Elements in general, I treat next of such
substances as are immediately composed of them, and are, next to them,
the most simple: such are all saline substances. This head comprehends
mineral Acids, fixed Alkalis, and their several combinations; the
volatile sulphureous spirit, sulphur, phosphorus, and the Neutral salts
which have an earth or fixed Alkali for their basis: those which have
for their basis either a volatile Alkali, or some metallic substance,
are referred, according to my general Plan, to the heads under which I
treat of those substances.

Metallic substances are scarcely more compounded than the saline;
which induces me to consider them next. I begin with those which are
the most simple, or at least seem to be so; because their principles,
being very strongly connected together, are separated with the greatest
difficulty: such are the Metals properly so called; namely, Gold,
Silver, Copper, Iron, Tin, and Lead. After these come the Semi-metals
in order; to wit, Regulus of Antimony, Zinc, Bismuth, and Regulus of
Arsenic. Mercury being a doubtful substance, which some Chymists rank
with the Metals, and others with the Semi-metals, because it actually
possesses certain properties in common with each, I have treated of it
in a separate Chapter, which stands between the Metals and Semi-metals.

I next proceed to examine the several sorts of Oils, whether Vegetable,
which are divided into fat, essential, and empyreumatic; or Animal, and
Mineral Oils.

By examining these substances we obtain ideas of all the principles
which enter into the composition of Vegetable and Animal bodies; that
is, of those substances that are capable of fermentation: this enables
me to treat of fermentation in general; of its three different degrees
or kinds, the spirituous, acetous, and putrid; and of the products
of those fermentations, ardent spirits, acids analogous to those of
vegetables and animals, and volatile alkalis.

The order in which I treat of all those substances being different from
that in which they are obtained from compound bodies, I give, in a
distinct Chapter, a general idea of Chymical Decomposition, with a view
to shew the order in which they are separated, from the several bodies
in the composition whereof they are found. This brings them a second
time under review, and gives me an opportunity of distinguishing those
which exist naturally in compound bodies, from those which are only the
result of a new combination of some of their principles produced by the
fire.

The succeeding Chapter explains the late Mr Geoffroy's Table of
Affinities; which I take to be of great use at the end of an Elementary
tract like this, as it collects into one point of view the most
essential and fundamental doctrines which are dispersed through the
work.

I conclude with an account of the Construction of such Vessels and
Furnaces as are usually employed in Chymistry.

In this Part I say nothing of any manual operations, or the several
ways of performing Chymical processes; reserving these particulars for
my Treatise of Practical Chymistry, to which this must be considered as
an Introduction.



CONTENTS.


  Elements of the THEORY of CHYMISTRY.

  CHAP. I.

  _Of the Principles of Bodies_           Page        1

  Sect. 1. Of Air                                     2

  Sect. 2. Of Water                                    3

  Sect. 3. Of Earth                                    4

  Sect. 4. Of Fire                                     5

  Sect. 5. Of the Phlogiston                           7

  CHAP. II. _A general View of the Relations or
  Affinities between Bodies_                           9

  CHAP. III.  _Of Saline Substances in general_       11

  Sect. 1. Of Acids                                   12

  Sect. 2. Of Alkalis                                 14

  Sect. 3. Of Neutral Salts                           15

  CHAP. IV.  _Of the Several Sorts of Saline Substances._

  Sect. 1. Of the Universal Acid                      18

  Sect. 2. Of the Nitrous Acid                        22

  Sect. 3. Of the Marine Acid                         25

  CHAP. V. _Of Lime_                                  29

  CHAP. VI. _Of Metallic Substances in general_       34

  CHAP. VII.  _Of Metals_                             37

  Sect. 1. Of Gold                                   _ib._

  Sect. 2. Of Silver                                  39

  Sect. 3. Of Copper                                  44

  Sect. 4. Of Iron                                    47

  Sect. 5. Of Tin                                     52

  Sect. 6. Of Lead                                    53

  CHAP. VIII.  _Of Quick-Silver_                      58

  CHAP. IX.  _Of the Semi-Metals._

  Sect. 1. Of Regulus of Antimony                     62

  Sect. 2. Of Bismuth                                 69

  Sect. 3. Of Zinc                                    70

  Sect. 4. Of Regulus of Arsenic                      72

  CHAP. X.  _Of Oil in general_                       76

  Sect. 1. Of Charcoal                                77

  Sect. 2. Of Soap                                    78

  CHAP. XI. _Of the Several Sorts of Oils._

  Sect. 1. Of Mineral Oils                            79

  Sect. 2. Of Vegetable Oils                          80

  Sect. 3. Of Animal Oils                             82

  CHAP. XII.  _Of Fermentation in general_            83

  CHAP. XIII.  _Of the Spirituous Fermentation_       84

  CHAP. XIV. _Of the Acetous Fermentation_            90

  Sect. 1. Of Vinegar                                 91

  Sect. 2. Of Tartar                                  93

  CHAP. XV. _Of the Putrid Fermentation, or
  Putrefaction_                                       96

  CHAP. XVI. _A general View of Chymical
  Decomposition_                                     101

  Sect. 1. The Analysis of Vegetable Substances      102

  Emulsions                                          104

  Sect. 2. The Analysis of Animal Substances         106

  Sect. 3. The Analysis of Mineral Substances        108

  Of the Pyrites                                     110

  Of Ores                                            112

  CHAP. XVII. _Explanation of the Table of
  Affinities_                                        119

  CHAP. XVIII.  _The Theory of Constructing the
  Vessels most commonly used in Chymistry_           126

  CHAP. XIX.  _The Theory of Constructing the
  Furnaces most commonly used in Chymistry_          133

  _Of Lutes_                                         147


  Elements of the PRACTICE of CHYMISTRY.

  Introduction                                       153

  PART I.  OF MINERALS.

  SECTION  I.
  Operations performed on Saline Mineral Substances.

  CHAP. I.  _Of the Vitriolic Acid._

  1. PROCESS. To extract Vitriol from the Pyrites    159

  2. To extract Sulphur from the Pyrites, and
  other Sulphureous Minerals                         162

  3. To extract Alum from aluminous Minerals         165

  4. To extract the Vitriolic Acid from Copperas
  or Green Vitriol                                   170

  5. To decompose Sulphur, and extract its Acid, by
  burning it                                         174

  6. To concentrate the Vitriolic Acid               176

  7. To decompound Vitriolated Tartar by means of the
  Phlogiston; or to compose Sulphur by combining the
  Vitriolic Acid with the Phlogiston                 179

  CHAP. II.  _Of the Nitrous Acid._

  1. PROCESS. To Extract Nitre out of Nitrous Earths
  and Stones. The Purification of Salt-Petre. Mother
  of Nitre. Magnesia                                 181

  2. To decompose Nitre by means of the Phlogiston.
  Nitre fixed by Charcoal. _Clyssus_ of Nitre.
  _Sal Polychrestum_                                 186

  3. To decompose Nitre by means of the Vitriolic Acid.
  The Smoking Spirit of Nitre. _Sal de duobus._ The
  Purification of Spirit of Nitre                    191

  CHAP. III. _Of the Marine Acid._

  1. PROCESS. To extract Sea-salt from Sea-water, and
  from Brine-springs. Epsom Salt                      195

  2. Experiments concerning the Decomposition of Sea-salt
  by means of the Phlogiston. Kunckel's Phosphorus    197

  3. To decompose Sea-salt by means of the Vitriolic Acid.
  Glauber's Salt. The Purification and Concentration
  of Spirit of Salt                                   211

  4. To decompose Sea-salt by means of the Nitrous Acid.
  _Aqua regis._ Quadrangular Nitre                    217

  CHAP. IV.  _Of Borax._                              218


  SECTION  II.

  Of Operations on Minerals.

  CHAP. I. _Of Gold._

  1. PROCESS. To separate Gold, by Amalgamation
  with Mercury, from the Earths and Stones with which
  it is found mixed                                   223

  2. To dissolve Gold in _Aqua Regis_, and by that means
  separate it from Silver. _Aurum Fulminans._ _Aurum
  Fulminans_ reduced                                  227

  3. To dissolve Gold by Liver of Sulphur             232

  4. To separate Gold from all other Metalline substances
  by means of Antimony                                233

  CHAP. II. _Of Silver._

  1. PROCESS. To separate Silver from its Ore, by means
  of Scorification with Lead                          238

  2. The refining of Silver by the Cupel              243

  3. To purify Silver by Nitre                        248

  4. To dissolve Silver in _Aqua Fortis_, and thereby separate
  it from every other Metalline substance. The Purification
  of _Aqua Fortis_. Silver precipitated by Copper     250

  5. To separate Silver from the Nitrous Acid by
  Distillation. Crystals of Silver.
  The Infernal Stone                                  254

  6. To separate Silver from the Nitrous Acid by
  Precipitation. _Luna Cornea._ _Luna Cornea_ reduced 256

  7. To dissolve Silver, and separate it from Gold, by
  Cementation                                         258

  CHAP. III. _Of Copper._

  1. PROCESS. To separate Copper from its Ore         262

  2. To purify Black Copper, and render it malleable  264

  3. To deprive Copper of its Phlogiston by
  Calcination                                         266

  4. To resuscitate the Calx of Copper, and reduce it
  to Metal, by restoring its Phlogiston               267

  5. To dissolve Copper in the Mineral Acids          268

  CHAP. IV. _Of Iron._

  1. PROCESS. To separate Iron from its Ore           270

  2. To render Pig-iron and brittle Iron malleable    273

  3. To convert Iron into Steel                       274

  4. The Calcination of Iron. Sundry Saffrons of Mars 276

  5. Iron dissolved by the mineral Acids              277

  CHAP V. _Of Tin._

  1. PROCESS. To extract Tin from its Ore             279

  2. The Calcination of Tin                           280

  3. The Dissolution of Tin by Acids                  284

  CHAP. VI. _Of Lead._

  1. PROCESS. To extract Lead from its Ore            286

  2. To separate Lead from Copper                     289

  3. The Calcination of Lead                          292

  4. To prepare Glass of Lead                         293

  5. Lead dissolved by the Nitrous Acid               295

  CHAP. VII. _Of Mercury._

  1. PROCESS. To extract Mercury from its Ore, or to
  revivify it from Cinabar                            298

  2. To give Mercury, by the action of Fire, the
  appearance of a Metalline Calx                      301

  3. To dissolve Mercury in the Vitriolic Acid. Turbith
  Mineral                                             302

  4. To combine Mercury with Sulphur. Æthiop's
  Mineral                                             304

  5. To sublime the Combination of Mercury and Sulphur
  into Cinabar                                        306

  6. To dissolve Mercury in the Nitrous Acid. Sundry
  Mercurial Precipitates                              307

  7. To combine Mercury with the Acid of Sea-salt.
  Corrosive Sublimate                                 308

  8. Sweet Sublimate                                  312

  9. The Panacea of Mercury                           314


  SECTION  III.

  Of Operations on the Semi-Metals.

  CHAP. I. _Of Antimony._

  1. PROCESS. To separate Antimony from its Ore       315

  2. The common Regulus of Antimony                   316

  3. Regulus of Antimony precipitated by Metals       318

  4. The Calcination of Antimony                      321

  5. Calx of Antimony reduced to a Regulus            323

  6. Antimony calcined with Nitre. Liver of Antimony.
  _Crocus Metallorum_                                 325

  7. Another Calcination of Antimony with Nitre.
  Diaphoretic Antimony. _Materia Perlata_.
  _Clyssus_ of Antimony                               326

  8. Calx of Antimony vitrified                       330

  9. Kermes Mineral                                   331

  10. Regulus of Antimony dissolved in the Mineral
  Acids                                               335

  11. Regulus of Antimony combined with the Acid of
  Sea-salt Butter of Antimony. Cinabar of Antimony    338

  12. Butter of Antimony decompounded by means of
  Water only. _Pulvis Algaroth_, or _Mercurius Vitæ_.
  The Philosophic Spirit of Vitriol                   342

  13. Bezoar Mineral.  The Bezoartic Spirit of Nitre  343

  14. Flowers of Antimony                             347

  15. Regulus of Antimony converted into Flowers      348

  CHAP. II.  _Of Bismuth._

  1. PROCESS. To extract Bismuth from its Ore         350

  2. Bismuth dissolved by Acids. Magistery of Bismuth.
  Sympathetic Ink                                     352

  CHAP. III. _Of Zinc._

  1. PROCESS. To extract Zinc from its Ore, or
  Calamine                                            357

  2. To sublime Zinc into Flowers                     359

  3. To combine Zinc with Copper. Brass. Prince's
  Metal, &c.                                          361

  4. Zinc dissolved in the Mineral Acids              365

  CHAP. IV.  _Of Arsenic._

  1. PROCESS. To extract Arsenic from its matrix.
  Zafre or Smalt                                      367

  2. To separate Arsenic from Sulphur                 371

  3. To give Arsenic the Metalline Form. Regulus of
  Arsenic                                             374

  4. To distil the Nitrous Acid by the interposition
  of Arsenic. Blue _Aqua Fortis_. A new Neutral Salt
  of Arsenic                                          377

  5. To alkalizate Nitre by Arsenic                   379


  PART II.  OF VEGETABLES.

  SECTION I. Operations on unfermented Vegetables.

  CHAP. I. _Of the Substances obtained from
  Vegetables by Expression only._

  1. PROCESS. To express and depurate the juice of a
  Plant, containing its Essential Salt. The
  crystallization of that Salt                        383

  2. To draw the Oils out of Kernels, Seeds, and Fruits,
  by Expression                                       386

  3. To draw the Essential Oils of certain Fruits by
  Expression                                          387

  CHAP. II.  _Of the Substances obtained from
  Vegetables by Triture._

  1. PROCESS. To make the Extract of a Plant by
  Trituration                                         389

  2. To extract from Seeds and Kernels, by
  Trituration, the matter of Emulsions                392

  CHAP. III.  _Of Operations on Fat Oils._

  1. PROCESS. To attenuate Fat Oils, and change their
  nature, by exposing them to the action of fire, and
  distilling them                                     395

  2. To combine Fat Oils with Acids. The decomposition
  of this combination                                 398

  3. To combine Fat Oils with Fixed Alkalis. Hard and
  Soft Soap. The decomposition of Soap                400

  4. To combine Fat Oils with Sulphur                 405

  5. To combine Fat Oils with Lead, and the Calces of
  Lead. The Basis of Plasters. The decomposition of
  this combination                                    406

  CHAP. IV. _Of the substances obtained from Vegetables with
  a degree of heat not exceeding that of boiling water._

  1. PROCESS. To obtain from Plants, by distilling them
  with the mean degree of heat between freezing and
  boiling water, a liquor impregnated with their
  Principle of Odour                                  408

  2. To extract the Fat Oils of Plants by Decoction in
  boiling water. Cacao-Butter                         410

  3. To extract the Essential Oils of Plants by
  Distillation with the heat of boiling water.
  Distilled Water                                     412

  4. To extract the Essential Oils of Plants by
  distillation _per descensum_                        418

  5. Infusions, Decoctions, and Extracts of Plants    419

  CHAP. V. _Of Operations on Essential Oils._

  1. PROCESS. The Rectification of Essential Oils     422

  2. To fire Oils by combining them with highly
  concentrated Acids: instanced in Oil of Turpentine  426

  3. To combine Essential Oils with mineral Sulphur.
  Balsam of Sulphur. This composition decompounded    434

  4. To combine Essential Oils with Fixed Alkalis.
  Starkey's Soap                                      438

  CHAP. VI. _Of the Substances obtained from Vegetables
  by means of a graduated heat, from that of boiling
  water, to the strongest that can be applied to them
  in close vessels._

  1. PROCESS. To analyze vegetable substances that
  yield neither a Fat nor an Essential Oil: instanced
  in Guaiacum-Wood                                    440

  2. To analyze a vegetable substance which yields the
  same principles as are obtained from Animal matters:
  instanced in Mustard-seed                           445

  CHAP. VII. _Of the Substances obtained from
  Vegetables by Combustion._

  1. PROCESS. To procure a Fixed, Caustic, Alkaline
  Salt from a vegetable substance, by burning it in
  the open air                                        448

  2. To procure the Fixed Salt of a Plant, by burning
  it after the manner of Tachenius                    453

  3. To render Fixed Alkalis very Caustic by means of
  Lime. The Caustic Stone                             455

  4. The Analysis of Soot                             457

  CHAP. VIII. _The Analyses of some particular
  substances belonging to the Vegetable Kingdom._

  1. PROCESS. Analysis of the Native Balsams: instanced
  in Turpentine                                       460

  2. The Analysis of Resins: instanced in Benjamin.
  The Flowers and Oil of Benjamin                     463

  Reflections on the Nature and Properties of Camphor 465

  3. The Analysis of Bitumens: instanced in Amber.
  The Volatile Salt and Oil of Amber                  467

  4. The Analysis of Bee's Wax, and such Oily Compounds
  as are analogous to it                              472

  5. The Saccharine juices of Plants analyzed: instanced
  in Honey                                            474

  6. Gummy substances analyzed: instanced in Gum
  Arabic                                              476

  SECTION II.  Of Operations on Fermented Vegetable
  Substances.

  CHAP. I. _Of the Product of Spirituous Fermentation._

  1. PROCESS. To make Wine of Vegetable Substances
  that are susceptible of Spirituous Fermentation     478

  2. To draw an Ardent Spirit from substances that have
  undergone the Spirituous Fermentation. The Analysis
  of Wine                                             482

  3. To dephlegmate Spirit of Wine by the means of
  Fixed Alkalis. Spirit of Wine analyzed              486

  CHAP. II. _Spirit of Wine combined with different
  Substances._

  1. PROCESS. To combine Spirit of Wine with the Vitriolic
  Acid. This combination decompounded. Rabel's
  Water. Æther. Sweet Oil of Vitriol. Hoffman's
  Anodyne Mineral Liquor                              492

  2. Spirit of Wine combined with Spirit of Nitre.
  Sweet Spirit of Nitre                               503

  3. Spirit of Wine combined with the Acid of Sea-salt.
  Dulcified Spirit of Salt                            508

  4. Oils, or Oily matters, that are soluble in Spirit of
  Wine, separated from Vegetables, and dissolved, by
  means of that Menstruum. Tinctures; Elixirs;
  Varnishes. Aromatic Strong Waters                   510

  CHAP. III. _Of Tartar._

  1. PROCESS. Tartar analyzed by distillation. The Spirit,
  Oil, and Alkaline Salt of Tartar                    514

  2. The depuration of Tartar. Cream and Crystals of
  Tartar                                              517

  CHAP. IV. _Crystal of Tartar combined with several
  substances._

  1. PROCESS. Crystal of Tartar combined with Absorbent
  Earths. Soluble Tartars                             519

  2. Crystal of Tartar combined with Fixed Alkalis. The
  Vegetable Salt. Saignette's Salt. The decomposition
  of Soluble Tartar                                   524

  3. Crystal of Tartar combined with Iron. Chalybeated
  Tartar. Tincture of Steel with Tartar. Soluble
  Chalybeated Tartar                                  528

  4. Crystal of Tartar combined with the reguline
  part of Antimony. Stibiated or Emetic Tartar        534

  CHAP. V. _Of the Product of Acetous Fermentation._

  1. PROCESS. Substances susceptible of the Acetous
  Fermentation turned into Vinegar                    536

  2. To concentrate Vinegar by Frost                  540

  3. Vinegar analyzed by distillation                 542

  CHAP. VI. _The Acid of Vinegar combined with
  different Substances._

  1. PROCESS. The Acid of Vinegar combined with Alkaline
  Substances. Foliated Salt of Tartar, or Regenerated
  Tartar. Decomposition of that Salt                  547

  2. The Acid of Vinegar combined with Copper. Verdegris.
  Crystals of Copper. This combination decompounded.
  Spirit of Verdegris                                 550

  3. The Acid of Vinegar combined with Lead. Ceruse.
  Salt or Sugar of Lead. This combination
  decompounded                                        552

  CHAP. VII. _Of the Putrid Fermentation of Vegetable Substances._

  1. PROCESS. The Putrefaction of Vegetables          557

  2. Putrefied Vegetable substances analyzed          559


  PART III. Of Operations on Animal Substances.

  CHAP. I.  _Of Milk._

  1. PROCESS. Milk separated into Butter, Curd, and
  Whey: instanced in Cow's Milk                       562

  2. Butter analyzed by distillation                  566

  3. The Curd of Milk analyzed by distillation        569

  4. Whey analyzed                                    571

  CHAP. II. _Of the Substances which compose an Animal Body._

  1. PROCESS. Blood analyzed: instanced in Bullock's
  Blood                                               574

  2. Flesh analyzed: instanced in Beef                580

  3. Bones analyzed: instanced in Ox-bones            583

  4. Animal Fat analyzed: instanced in Mutton-Suet    584

  5. Eggs analyzed: instanced in Pullet's Eggs        586

  CHAP. III. _Of Animal Excrements._

  1. PROCESS. Dung analyzed: instanced in Human Excrement.
  Mr. Homberg's Phosphorus                            588

  2. Human Urine analyzed                             596

  CHAP. IV. _Of Volatile Alkalis._

  1. PROCESS. Volatile Alkalis rectified and
  depurated                                           599

  2. Volatile Alkalis combined with Acids. Sundry
  Ammoniacal Salts.  Sal Ammoniac                     602

  3. Sal Ammoniac decompounded by Acids               607

  4. Sal Ammoniac decompounded by Fixed Alkalis.
  Volatile Salt. The Febrifuge of Sylvius             608

  5. Sal Ammoniac decompounded by Absorbent Earths
  and Lime. Volatile Spirit of Sal Ammoniac. Fixed
  Sal Ammoniac. Oil of Lime                           611

  6. Volatile Alkalis combined with oily matters.
  A Volatile Oily Aromatic Salt                       616


[Illustration: Decorative Scroll]



  ELEMENTS
  OF THE
  THEORY OF CHYMISTRY.



CHAP. I.

_Of the_ PRINCIPLES _of_ BODIES.


The object and principal end of Chymistry, is to separate the different
substances that enter into the composition of bodies; to examine
each of them apart; to discover their properties and relations;
to decompose, if possible, those very substances; to compare them
together, and combine them with others; to re-unite them again into one
body, so as to reproduce the original compound with all its properties;
or even to produce new compounds that never existed among the works of
nature, from mixtures of other matters differently combined.

But this Analysis, or Decomposition, of bodies is finite; we being
unable to carry it beyond a certain limit. In whatever way we attempt
to go further, we are always stopped by substances in which we can
produce no change, which will not admit of being resolved into others,
and which stand as so many firm barriers obstructing our progress.

To these substances we may, in my opinion, give the title of Principles
or Elements: at least, with regard to us, they are really such. Of this
sort the principal are Earth, Water, Air, and Fire. For though there
is ground to believe that these are not the primary component parts,
or the most simple elements, of matter; yet, as we know by experience,
that our senses cannot possibly discover the principles of which they
are composed, it seems more reasonable to fix upon them, and consider
them as simple homogeneous bodies, and the principles of the rest, than
to fatigue our minds with vain conjectures about the parts or elements
of which they may consist; seeing there is no criterion by which we
can know whether we have hit upon the truth, or whether the notions we
have formed are mere fancies. We shall therefore consider these four
substances as the principles or elements of all the various compounds
which nature presents to our inquiries: because, of all those we have
as yet discovered, they are in fact the most simple; and because all
our decompositions, all our experiments on other bodies, plainly prove
that they are at last resolvable into these primary parts.

These principles do not enter in the same proportion into all bodies:
there are even some mixts in the composition of which this or that
particular principle is not to be found. Thus Air and Water seem
to be wholly excluded from the texture of Metals; at least all the
experiments that have hitherto been made on them seem to confirm this
opinion.

The substances composed immediately of these _first_ Elements we
shall call _secondary_ Principles; because in reality their several
combinations with each other, the interchangeable coalitions that take
place between them, constitute the different natures of all other
bodies; which, as they result from the union both of primary and
secondary principles, are properly entitled to the name of Compounds or
Mixts.

Before we enter upon the examination of Compound Substances, it is
necessary to consider with some attention the most Simple ones, or our
four first principles, in order to discover their chief properties.


SECTION I.

_Of_ AIR.

Air is that Fluid which we constantly breathe, and which surrounds the
whole surface of the terrestrial globe. Being heavy, like all other
bodies, it penetrates into all places that are not either absolutely
inaccessible, or filled with some other body heavier than itself.
Its principal property is to be susceptible of condensation and
rarefaction; so that the very same quantity of Air may occupy a much
greater, or a much smaller space, according to the different state it
is in. Heat and cold, or, if you will, the presence and the absence
of the particles of Fire, are the most usual causes, and indeed
the measures, of its condensation and rarefaction: for if a certain
quantity of Air be heated, its bulk enlarges in proportion to the
degree of heat applied to it; the consequence of which is, that the
same space now contains fewer particles of Air than it did before. Cold
again produces just the opposite effect.

On this property which Air has, of being condensed and rarefied by
heat, its elasticity or springiness chiefly depends. For if Air were
forced by condensation into a less compass than it took up before, and
then exposed to a very considerable degree of cold, it would remain
quite inactive, without exerting such an effort as it usually makes
against the compressing body. On the other hand, the elasticity of
heated Air arises only from hence, that being rarefied by the action of
Fire, it requires much more space than it occupied before.

Air enters into the composition of many substances, especially
vegetable and animal bodies: for by analysing most of them such a
considerable quantity thereof is extricated, that some naturalists
have suspected it to be altogether destitute of elasticity when thus
combined with the other principles in the composition of bodies.
According to them, the efficacy of the elastic power of the Air is so
prodigious, and its force when compressed so excessive, that it is
not possible the other component parts of bodies should be able to
confine so much of it, in that state of compression which it must needs
undergo, if retaining its elasticity it were pent up among them.

However that be, this elastic property of the Air produces the most
singular and important phenomena, observable in the resolution and
composition of bodies.


SECTION II.

_Of_ WATER.

Water is a thing so well known, that it is almost needless to attempt
giving a general idea of it here. Every one knows that it is a
transparent, insipid substance, and usually fluid. I say it is usually
so; for being exposed to a certain degree of cold it becomes solid:
solidity therefore seems to be its most natural state.

Water exposed to the Fire grows hot; but only to a limited degree,
beyond which its heat never rises, be the force of Fire applied to it
ever so violent: it is known to have acquired this degree of heat by
its boiling up with great tumult. Water cannot be made hotter, because
it is volatile, and incapable of enduring the heat, without being
evaporated and entirely dissipated.

If such a violent and sudden heat be applied to Water, as will not
allow it time to exhale gently in vapours, as when, for instance,
a small quantity thereof is thrown upon a metal in fusion, it is
dissipated at once with vast impetuosity, producing a most terrible and
dangerous explosion. This surprising effect may be deduced from the
instantaneous dilatation of the parts of the Water itself, or rather
of the Air it contains. Moreover, Water enters into the texture of
many bodies, both compounds and secondary principles; but, like Air,
it seems to be excluded from the composition of all metals and most
minerals. For although an immense quantity of Water exists in the
bowels of the Earth, moistening all its contents, it cannot be thence
inferred, that it is one of the principles of minerals. It is only
interposed between their parts; for they may be entirely divested of
it, without any sort of decomposition: indeed it is not capable of an
intimate connection with them.


SECTION III.

_Of_ EARTH.

We observed that the two principles above treated of are volatile; that
is, the action of Fire separates them from the bodies they help to
compose, carrying them quite off, and dissipating them. That of which
we are now to speak, namely Earth, is fixed, and, when it is absolutely
pure, resists the utmost force of Fire. So that, whatever remains of
a body, after it hath been exposed to the power of the fiercest Fire,
must be considered as containing nearly all its earthy principle,
and consisting chiefly thereof. I qualify my expression thus for two
reasons: the first is, because it often happens, that this remainder
does not actually contain all the Earth which existed originally in
the mixt body decomposed by Fire; since it will afterwards appear that
Earth, though in its own nature fixed, may be rendered volatile by
being intimately united with other substances which are so; and that,
in fact, it is common enough for part of the Earth of a body to be thus
volatilized by its other principles: the second is, that what remains
after the calcination of a body is not generally its earth in perfect
purity, but combined with some of its other principles, which, though
volatile in their own natures, have been fixed by the union contracted
between it and them. We shall, in the sequel, produce some examples to
illustrate this theory.

Earth, therefore, properly so called, is a fixed principle, which is
permanent in the Fire. There is reason to think it very difficult, if
not impossible, to obtain the earthy principle entirely free from every
other substance: for after our utmost endeavours to purify them, the
Earths we obtain from different compounds are found to have different
properties, according to the different bodies from which they are
procured; or else, if those Earths be pure, we must allow them to be
essentially different, seeing they have different properties.

Earth, in general, with regard to its properties, may be distributed
into _fusible_, and _unfusible_; that is, into Earth that is capable
of melting or becoming fluid in the Fire, and Earth that constantly
remains in a solid form, never melting in the strongest degree of heat
to which we can expose it.

The former is also called _vitrifiable_, and the second _unvitrifiable_
Earth; because, when Earth is melted by the force of Fire, it becomes
what we call _Glass_, which is nothing but the parts of Earth brought
into nearer contact, and more closely united by the means of fusion.
Perhaps the Earth, which we look upon as incapable of vitrification,
might be fused if we could apply to it a sufficient degree of heat.
It is at least certain, that some Earths, or stones, which separately
resist the force of Fire, so that they cannot be melted, become
fusible when mixed together. Experience convinced Mr. du Hamel that
lime-stone and slate are of this kind. It is however undoubtedly true,
that one Earth differs from another in its degree of fusibility: and
this gives ground to believe, that there may be a species of Earth
absolutely unvitrifiable in its nature, which, being mixed in different
proportions with fusible Earths, renders them difficult to melt.

Whatever may be in this, as there are Earths which we are absolutely
unable to vitrify, that is a sufficient reason for our division of
them. Unvitrifiable Earths seem to be porous, for they imbibe Water;
whence they have also got the name of _Absorbent Earths_.


SECTION IV.

_Of_ FIRE.

The Matter of the Sun, or of Light, the Phlogiston, Fire, the
Sulphureous Principle, the Inflammable Matter, are all of them names
by which the Element of Fire is usually denoted. But it should seem,
that an accurate distinction hath not yet been made between the
different states in which it exists; that is, between the phenomena of
Fire actually existing as a principle in the composition of bodies, and
those which it exhibits when existing separately and in its natural
state: nor have proper distinct appellations been assigned to it in
those different circumstances. In the latter state we may properly give
it the names of Fire, Matter of the Sun, of Light, and of Heat; and
may consider it as a substance composed of infinitely small particles,
continually agitated by a most rapid motion, and, of consequence,
essentially fluid.

This substance, of which the sun may be called the general reservoir,
seems to flow incessantly from that source, diffusing itself over the
world, and through all the bodies we know; but not as a principle, or
essential part of them, since they may be deprived thereof, at least
in a great measure, without suffering any decomposition. The greatest
change produced on them, by its presence or its absence, is the
rendering them fluid or solid: so that all other bodies may be deemed
naturally solid; Fire alone essentially fluid, and the principle of
fluidity in others. This being presupposed, Air itself might become
solid, if it could be entirely deprived of the Fire it contains; as
bodies of most difficult fusion become fluid, when penetrated by a
sufficient quantity of the particles of Fire.

One of the chief properties of this pure Fire is to penetrate easily
into all bodies, and to diffuse itself among them with a sort of
uniformity and equality: for if a heated body be contiguous to a cold
one, the former communicates to the latter all its excess of heat,
cooling in exact proportion as the other warms, till both come to have
the very same degree of heat. Heat, however, is naturally communicable
soonest to the upper parts of a body; and consequently, when a body
cools, the under parts become soonest cold. It hath been observed, for
instance, that the lower extremity of a heated body, freely suspended
in the air, grows cold sooner than the upper; and that, when a bar of
iron is red-hot at one end, and cold at the other, the cold end is much
sooner heated by placing the bar so that the hot end may be undermost,
than, when that end is turned uppermost. The levity of the matter of
Fire, and the vicinity of the Earth, may possibly be the causes of this
phenomenon.

Another property of Fire is to dilate all bodies into which it
penetrates. This hath already been shewn with regard to Air and Water;
and it produces the same effect on Earth.

Fire is the most powerful agent we can employ to decompose bodies; and
the greatest degree of heat producible by man, is that excited by the
rays of the sun collected in the focus of a large burning-glass.


SECTION V.

_Of the_ PHLOGISTON.

From what hath been said concerning the nature of Fire, it is
evidently impossible for us to fix and confine it in any body. Yet the
phenomena attending the combustion of inflammable bodies shew, that
they really contain the matter of Fire as a constituent principle.
By what mechanism then is this fluid, which is so subtle, so active,
so difficult to confine, so capable of penetrating into every other
substance in nature; how comes it, I say, to be so fixed as to make
a component part of the most solid bodies? It is no easy matter to
give a satisfactory answer to this question. But, without pretending
to guess the cause of the phenomenon, let us rest contented with the
certainty of the fact, the knowledge of which will undoubtedly procure
us considerable advantages. Let us therefore examine the properties of
Fire thus fixed, and become a principle of bodies. To this substance,
in order to distinguish it from pure and unfixed Fire, the Chymists
have assigned the peculiar title of the _Phlogiston_, which indeed is
no other than a Greek word for the Inflammable Matter; by which latter
name, as well as by that of the Sulphureous Principle, it is also
sometimes called. It differs from elementary Fire in the following
particulars. 1. When united to a body, it communicates to it neither
heat nor light. 2. It produces no change in its state, whether of
solidity or fluidity; so that a solid body does not become fluid by
the accession of the Phlogiston, and _vice versa_; the solid bodies to
which it is joined being only rendered thereby more apt to be fused by
the force of the culinary fire. 3. We can convey it from the body with
which it is joined into another body, so that it shall enter into the
composition thereof, and remain fixed in it.

On this occasion both these bodies, that which is deprived of the
Phlogiston and that which receives it, undergo very considerable
alterations; and it is this last circumstance, in particular, that
obliges us to distinguish the Phlogiston from pure Fire, and to
consider it as the element of Fire combined with some other substance,
which serves it as a basis for constituting a kind of secondary
principle. For if there were no difference between them, we should be
able to introduce and fix pure Fire itself, wherever we can introduce
and fix the Phlogiston: yet this is what we can by no means do, as will
appear from experiments to be afterwards produced.

Hitherto, Chymists have never been able to obtain the Phlogiston quite
pure, and free from every other substance: for there are but two ways
of separating it from a body of which it makes a part; to wit, either
by applying some other body with which it may unite the moment it
quits the former; or else by calcining and burning the compound from
which you desire to sever it. In the former case it is evident that we
do not get the Phlogiston by itself, because it only passes from one
combination into another; and in the latter, it is entirely dissipated
in the decomposition, so that no part of it can possibly be secured.

The inflammability of a body is an infallible sign that it contains
a Phlogiston; but from a body's not being inflammable, it cannot be
inferred that it contains none; for experiments have demonstrated that
certain metals abound with it, which yet are by no means inflammable.

We have now delivered what is most necessary to be known concerning the
principles of bodies in general. They have many other qualities besides
those above-mentioned; but we cannot properly take notice of them
here, because they presuppose an acquaintance with some other things
relating to bodies, of which we have hitherto said nothing; intending
to treat of them in the sequel as occasion shall offer. We shall only
observe in this place, that when animal and vegetable matters are
burnt, in such a manner as to hinder them from flaming, some part
of the Phlogiston contained in them unites intimately with their
most fixed earthy parts, and with them forms a compound, that can be
consumed only by making it red-hot in the open air, where it sparkles
and wastes away, without emitting any flame. This compound is called
a _Coal_. We shall inquire into the properties of this Coal under the
head of Oils: at present it suffices that we know in general what it
is, and that it readily communicates to other bodies the Phlogiston it
contains.



CHAP. II.

_A general View of the Relations or Affinities between Bodies._


Before we can reduce compound Bodies to the first principles above
pointed out, we obtain, by analysing them, certain substances which
are indeed more simple than the bodies they helped to compose, yet are
themselves composed of our primary principles. They are therefore at
one and the same time both principles and compounds; for which reason
we shall, as was before said, call them by the name of Secondary
Principles. Saline and oily matters chiefly constitute this class. But
before we enter upon an examination of their properties, it is fit we
lay before the reader a general view of what Chymists understand by
the Relations or Affinities of Bodies; because it is necessary to know
these, in order to a distinct conception of the different combinations
we are to treat of.

All the experiments hitherto made concur with daily observation to
prove, that different bodies, whether principles or compounds, have
such a mutual Conformity, Relation, Affinity, or Attraction, if you
will call it so, as disposes some of them to join and unite together,
while they are incapable of contracting any union with others. This
effect, whatever be its cause, will enable us to account for, and
connect together, all the phenomena that Chymistry produces. The nature
of this universal affection of matter is distinctly laid down in the
following propositions.

First, If any substance hath any Affinity or conformity with another,
the two will unite together, and form one compound.

Secondly, It may be laid down as a general rule, that all similar
substances have an Affinity with each other, and are consequently
disposed to unite; as water with water, earth with earth, _&c._

Thirdly, Substances that unite together lose some of their separate
properties; and the compounds resulting from their union partake of the
properties of those substances which serve as their principles.

Fourthly, The simpler any substances are, the more perceptible and
considerable are their Affinities: whence it follows, that the less
bodies are compounded, the more difficult it is to analyse them; that
is, to separate from each other the principles of which they consist.

Fifthly, If a body consist of two substances, and to this compound
be presented a third substance, that has no Affinity at all with one
of the two primary substances aforesaid, but has a greater Affinity
with the other than those two substances have with each other, there
will ensue a decomposition, and a new union; that is, the third
substance will separate the two compounding substances from each other,
coalesce with that which has an Affinity with it, form therewith a
new combination, and disengage the other, which will then be left at
liberty, and such as it was before it had contracted any union.

Sixthly, It happens sometimes that when a third substance is presented
to a body consisting of two substances, no decomposition follows;
but the two compounding substances, without quitting each other,
unite with the substance presented to them, and form a combination of
three principles: and this comes to pass when that third substance
has an equal, or nearly equal, Affinity with each of the compounding
substances. The same thing may also happen even when the third
substance hath no Affinity but with one of the compounding substances
only. To produce such an effect, it is sufficient that one of the
two compounding substances have to the third body a Relation equal,
or nearly equal, to that which it has to the other compounding
substance with which it is already combined. Thence it follows, that
two substances, which, when apart from all others, are incapable
of contracting any union, may be rendered capable of incorporating
together in some measure, and becoming parts of the same compound, by
combining with a third substance with which each of them has an equal
Affinity.

Seventhly, A body, which of itself cannot decompose a compound
consisting of two substances, because, as we just now said, they have
a greater affinity with each other than it has with either of them,
becomes nevertheless capable of separating the two by uniting with
one of them, when it is itself combined with another body, having a
degree of Affinity with that one, sufficient to compensate its own want
thereof. In that case there are two Affinities, and thence ensues a
double decomposition and a double combination.

These fundamental truths, from which we shall deduce an explanation
of all the phenomena in Chymistry, will be confirmed and illustrated
by applying them, as we shall do, to the several cases, of which our
design in this treatise obliges us to give a circumstantial account.



CHAP. III.

_Of Saline Substances in general._


If a particle of water be intimately united with a particle of earth,
the result will be a new compound, which, according to our third
proposition of Affinities, will partake of the properties of earth
and of water; and this combination principally forms what is called
a _Saline Substance_. Consequently every Saline Substance must have
an affinity with earth and with water, and be capable of uniting with
both or either of them, whether they be separate or mixed together:
and accordingly this property characterizes all Salts, or Saline
Substances, in general.

Water being volatile and Earth fixed, Salts in general are less
volatile than the former, and less fixed than the latter; that is,
fire, which cannot volatilize and carry off pure earth, is capable of
rarefying and volatilizing a Saline Substance; but then this requires a
greater degree of heat than is necessary for producing the same effects
on pure water.

There are several sorts of Salts, differing from one another, in
respect either of the quantity, or the quality of the earth in their
composition; or, lastly, they differ on account of some additional
principles, which not being combined with them in sufficient quantity
to hinder their Saline properties from appearing, permit them to retain
the name of Salts, though they render them very different from the
simplest Saline Substances.

It is easy to infer, from what has been said of Salts in general, that
some of them must be more, some less, fixed or volatile than others,
and some more, some less, disposed to unite with water, with earth,
or with particular sorts of earth, according to the nature or the
proportion of their principles.

Before we proceed further, it is proper just to mention the principle
reasons, which induce us to think that every Saline Substance is
actually a combination of earth and water, as we supposed at our
entering on this subject. The first is, the conformity Salts have
with earth and water, or the properties they possess in common with
both. Of these properties we shall treat fully, as occasion offers to
consider them, in examining the several sorts of Salts. The second
is, that all Salts may be actually resolved into earth and water by
sundry processes; particularly by repeated dissolution in water,
evaporation, desiccation, and calcination. Indeed the Chymists have
not yet been able to procure a Saline Substance, by combining earth
and water together. This favours a suspicion, that, besides these
two, there is some other principle in the composition of salts, which
escapes our researches, because we cannot preserve it when we decompose
them; but it is sufficient to our purpose, that water and earth are
demonstrably amongst the real principles of Saline Substances, and that
no experiment hath ever shewn us any other.


SECTION I.

_Of_ ACIDS.

Of all Saline Substances, the simplest is that called an _Acid_, on
account of its taste; which is like that of verjuice, sorrel, vinegar,
and other sour things, which, for the same reason, are also called
Acids. By this peculiar taste are Acids chiefly known. They have
moreover the property of turning all the blue and violet colours of
vegetables red, which distinguishes them from all other salts.

The form, under which Acids most commonly appear, is that of a
transparent liquor; though solidity is rather their natural state.
This is owing to their affinity with water; which is so great, that,
when they contain but just as much of it as is necessary to constitute
them Salts, and consequently have a solid form, they rapidly unite
therewith the moment they come into contact with it: and as the air
is always loaded with moisture and aqueous vapours, its contact alone
is sufficient to liquify them; because they unite with its humidity,
imbibe it greedily, and by that means become fluid. We therefore say,
they attract the moisture of the air. This change of a salt from a
solid to a fluid state, by the sole contact of the air, is also called
_Deliquium_; so that when a salt changes in this manner from a solid
into a fluid form, it is said to run _per deliquium_. Acids being the
simplest species of Saline bodies, their affinities with different
substances are stronger than those of any other sort of salt with
the same substances; which is agreeable to our fourth proposition
concerning Affinities.

Acids in general have a great affinity with earths: that with which
they most readily unite is the unvitrifiable earth to which we gave the
name of absorbent earth. They seem, not to act at all upon vitrifiable
earths, such as sand; nor yet upon some other kinds of earths, at least
while they are in their natural state. Yet the nature of these earths
may be in some measure changed, by making them red-hot in the fire,
and then quenching them suddenly in cold water: for, by repeating this
often, they are brought nearer to the nature of absorbent earths, and
rendered capable of uniting with Acids.

When an acid liquor is mixed with an absorbent earth, for instance with
chalk, these two substances instantly rush into union, with so much
impetuosity, especially if the acid liquor be as much dephlegmated,
or contain as little water, as may be, that a great ebullition is
immediately produced, attended with considerable hissing, heat, and
vapours, which rise the very instant of their conjunction.

From the combination of an acid with an absorbent earth there arises
a new compound, which some Chymists have called _Sal Salsum_; because
the Acid by uniting with the earth loses its sour taste, and acquires
another not unlike that of the common sea-salt used in our kitchens;
yet varying according to the different sorts of Acids and earths
combined together. The Acid at the same time loses its property of
turning vegetable blues and violet colours red.

If we inquire what is become of its propensity to unite with water, we
shall find that the earth, which of itself is not soluble in water,
hath, by its union with the Acid, acquired a facility of dissolving
therein; so that our _Sal Salsum_ is soluble in water. But, on the
other hand, the Acid hath, by its union with the earth, lost part of
the affinity it had with water; so that if a _Sal Salsum_ be dried,
and freed of all superfluous humidity, it will remain, in that dry
solid form, instead of attracting the moisture of the air, and running
_per deliquium_, as the Acid would do if it were pure and unmixed
with earth. However, this general rule admits of some exceptions; and
we shall have occasion in another place to take notice of certain
combinations of Acids with earths, which still continue to attract the
moisture of the air, though not so strongly as a pure Acid.

ACIDS have likewise a great affinity with the Phlogiston. When we come
to treat of each Acid in particular, we shall examine the combinations
of each with the Phlogiston: they differ so widely from one another,
and many of them are so little known, that we cannot at present give
any general idea of them.


SECTION II.

_Of_ ALKALIS.

Alkalis are Saline combinations, in which there is a greater proportion
of earth than in Acids. The principal arguments that may be adduced
to prove this fact are these: First; if they be treated in the manner
proposed above for analyzing Saline Substances, we obtain from them
a much greater quantity of earth than we do from Acids. Secondly; by
combining certain Acids with certain earths we can produce Alkalis; or
at least such saline compounds as greatly resemble them. Our third and
last argument is drawn from the properties of those Alkalis which, when
pure and unadulterated with any other principle, have less affinity
with water than Acids have, and are also more fixed, resisting the
utmost force of fire. On this account it is that they have obtained the
title of _Fixed_, as well as to distinguish them from another species
of Alkali, to be considered hereafter, which is impure and volatile.

Though fixed Alkalis, when dry, sustain the utmost violence of fire
without flying off in vapours, it is remarkable that, being boiled with
water in an open vessel, considerable quantities of them rise with the
steam: an effect which must be attributed to the great affinity between
these two substances, by means whereof water communicates some part of
its volatility to the fixed salt.

Alkalis freed of their superfluous humidity by calcination attract the
moisture of the air, but not so strongly as Acids: so that it is easier
to procure and preserve them in a solid form.

They flow in the fire, and are then capable of uniting with vitrifiable
earths, and of forming therewith true glass, which, however, will
partake of their properties, if they be used in sufficient quantity.

As they melt more readily than vitrifiable earth, they facilitate its
fusion; so that a weaker fire will reduce it to glass, when a fixed
Alkali is joined with it, than will melt it without that addition.

Alkalis are known by their taste, which is acrid and fiery; and by the
properties they possess of turning vegetable blues and violet colours
green; particularly syrop of violets.

Their affinity with acids is greater than that of absorbent earths; and
hence it comes to pass, that if an Alkali be presented to a combination
of an Acid with an absorbent earth, the earth will be separated from
the Acid by the Alkali, and a new union between the Acid and the Alkali
will take place. This is both an instance and a proof of our fifth
proposition concerning Affinities.

If a pure Alkali be presented to a pure Acid, they rush together with
violence, and produce the same phenomena as were observed in the
union of an absorbent earth with an Acid; but in a greater and more
remarkable degree.

Fixed Alkalis may in general be divided into two sorts: one of these
hath all the above-recited properties; but the other possesses some
that are peculiar to itself. We shall consider this latter sort more
particularly under the head of Sea-Salt.


SECTION III.

_Of_ NEUTRAL SALTS.

The Acid and the Alkali thus uniting mutually rob each other of their
characteristic properties; so that the compound resulting from their
union produces no change in the blue colours of vegetables, and
has a taste which is neither sour nor acrid, but saltish. A saline
combination of this kind is for that reason named _Sal Salsum_, _Sal
Medium_, of a _Neutral Salt_. Such combinations are also called by the
plain general name of _Salts_.

It must be observed that, in order to make these Salts perfectly
Neutral, it is necessary that neither of the two saline principles
of which they are compounded be predominant over the other; for in
that case they will have the properties of the prevailing principle.
The reason is this: neither of these saline substances can unite with
the other but in a limited proportion, beyond which there can be no
further coalition between them. The action by which this perfect union
is accomplished is termed _Saturation_; and the instant when such
proportions of the two saline substances are mixed together, that the
one is incorporated with as much of the other as it can possibly take
up, is called the _Point of Saturation_. All this is equally applicable
to the combination of an Acid with an absorbent earth.

The combination is known to be perfect, that is, the Point of
Saturation is known to be obtained, when, after repeated affusions of
an Acid in small quantities to an Alkali, or an absorbent earth, we
find those phenomena cease, which in such cases constantly attend the
conflict of union, as we said above, namely, ebullition, hissing, _&c._
and we may be assured the Saturation is complete when the new compound
hath neither an acid nor an acrid taste, nor in the least changes the
blue colours of vegetables.

Neutral salts have not so great an affinity with water as either Acids
or Alkalis have; because they are more compounded: for we observed
before, that the affinities of the most compounded bodies are generally
weaker than those of the most simple. In consequence hereof few Neutral
Salts, when dried, attract the moisture of the air; and those that do,
attract it more slowly, and in less quantity, than either Acids or
Alkalis do.

All Neutral Salts are soluble in water; but more or less readily, and
in a greater or smaller quantity, according to the nature of their
component principles.

Water made boiling hot dissolves a greater quantity of those salts
which do not attract the moisture of the air, than when it is cold;
and indeed it must be boiling hot to take up as much of them as it
is capable of dissolving: but as for those which run in the air, the
difference, if there be any, is imperceptible.

Some Neutral Salts have the property of shooting into crystals, and
others have it not.

The nature of Crystallization is this: Water cannot dissolve, nor keep
in solution, more than a determinate quantity of any particular Salt:
when therefore such a quantity of water is evaporated from the solution
of a Salt capable of crystallization, that the remainder contains just
as much Salt as it can dissolve, then by continuing the evaporation
the Salt gradually recovers its solid form, and concretes into several
little transparent masses called Crystals. These crystals have regular
figures, all differing from one another according to the species of
salt of which they are formed. Different methods of evaporating saline
solutions have different effects on the figure and regularity of the
crystals; and each particular sort of salt requires a peculiar method
of evaporation to make its crystals perfectly regular.

A solution of salt designed for crystallization is usually evaporated
by means of fire to a pellicle; that is, till the Salt begin to
concrete; which is perceived by a kind of thin dark skin that gathers
on the surface of the liquor, and is formed of the crystallized
particles of Salt. When this pellicle appears the solution is suffered
to cool, and the crystals form therein faster or slower, according to
the sort of salt in hand. If the evaporation be carried on briskly to
perfect dryness, no crystals will be formed, and only an irregular mass
of salt will be obtained.

The reasons why no crystals appear when the evaporation is hastily
performed, and carried on to dryness, are, first, that the particles
of salt, being always in motion while the solution is hot, have not
time to exert their mutual affinities, and to unite together as
crystallization requires: Secondly, that a certain quantity of water
enters into the very composition of crystals; which is therefore
absolutely necessary to their formation, and in a greater or smaller
proportion according to the nature of the Salt[1].

  [1] Those who have the curiosity to see a more particular account
  of the Crystallization of Neutral Salts, may read Mr. _Rouelle_'s
  excellent Memoir on that subject, among those of the Academy of
  Sciences for 1744.

If these crystallized salts be exposed to the fire, they first part
with that moisture which is not necessary to a saline concretion, and
which they retained only by means of their crystallization: afterwards
they begin to flow, but with different degrees of fusibility.

It must be observed, that certain salts melt as soon as they are
exposed to the fire; namely, those which retain a great deal of water
in crystallizing. But this fluor which they so readily acquire must be
carefully distinguished from actual fusion: for it is owing only to
their superfluous humidity, which heat renders capable of dissolving
and liquifying them; so that when it is evaporated the Salt ceases to
be fluid, and requires a much greater degree of fire to bring it into
real fusion.

The Neutral Salts that do not crystallize may, indeed, be dried by
evaporating the water which keeps them fluid; but by becoming solid
they acquire no regular form; they again attract the moisture of
the air, and are thereby melted into a liquor. These may be called
_Liquescent Salts_.

Most of the Neutral Salts, that consist of an Acid joined with a fixed
Alkali, or with an absorbent earth, are themselves fixed and resist
the force of fire; yet several of them, if they be dissolved in water,
and the solution boiled and evaporated, fly off along with the steams.



CHAP. IV.

_Of the several Sorts of Saline Substances._


SECTION I.

_Of the_ UNIVERSAL ACID.

The Universal Acid is so called, because it is in fact the Acid which
is most universally diffused through all nature, in waters, in the
atmosphere, and in the bowels of the earth. But it is seldom pure;
being almost always combined with some other substance. That from which
we obtain it with most ease, and in the greatest quantity, is Vitriol,
a mineral which we shall consider afterwards: and this is the reason
why it is called the _Vitriolic Acid_; the name by which it is best
known.

When the Vitriolic Acid contains but little phlegm, yet enough to give
it a fluid form, it is called _Oil of Vitriol_, on account of a certain
unctuosity belonging to it. In truth this name is very improperly
bestowed on it; for we shall afterwards see that, bating this
unctuousness, it has none of the properties of oils. But this is not
the only impropriety in names that we shall have occasion to censure.

If the Vitriolic Acid contain much water, it is then called _Spirit of
Vitriol_. When it does not contain enough to render it fluid, and so is
in a solid form, it is named the _Icy Oil of Vitriol_.

When Oil of Vitriol highly concentrated is mixed with water, they rush
into union with such impetuosity, that, the moment they touch each
other, there arises a hissing noise, like that of red-hot iron plunged
in cold water, together with a very considerable degree of heat,
proportioned to the degree to which the Acid was concentrated.

If, instead of mixing this concentrated Acid with water, you only
leave it exposed to the air for some time, it attracts the moisture
thereof, and imbibes it most greedily. Both its bulk and its weight are
increased by this accession; and if it be under an icy form, that is,
if it be concreted, the phlegm thus acquired will soon resolve it into
a fluid.

The addition of water renders the Vitriolic Acid, and indeed all other
Acids, weaker in one sense; which is, that when they are very aqueous
they leave on the tongue a much fainter taste of acidity, and are less
active in the solution of some particular bodies: but that occasions
no change in the strength of their affinities, but in some cases
rather enables them to dissolve several substances, which, when well
dephlegmated, they are not capable of attacking.

The Vitriolic Acid combined to the point of saturation with a
particular absorbent earth, the nature of which is not yet well known,
forms a Neutral Salt that crystallizes. This Salt is called _Alum_, and
the figure of its crystals is that of an octahedron, or solid of eight
sides. These octahedra are triangular pyramids, the angles of which are
so cut off that four of the surfaces are hexagons, and the other four
triangles.

There are several sorts of Alum, which differ according to the earths
combined with the Vitriolic Acid. Alum dissolves easily in water, and
in crystallization retains a considerable quantity of it; which is the
reason that being exposed to the fire it readily melts, swelling and
puffing up as its superfluous moisture exhales. When that is quite
evaporated, the remainder is called _Burnt Alum_, and is very difficult
to fuse. The Acid of the Alum is partly dissipated by this calcination.
Its taste is saltish, with a degree of roughness and astringency.

The Vitriolic Acid combined with certain earths forms a kind of
Neutral Salt called _Selenites_, which crystallizes in different forms
according to the nature of its earth. There are numberless springs
of water infected with dissolved Selenites; but when this Salt is
once crystallized, it is exceeding difficult to dissolve it in water
a second time. For that purpose a very great quantity of water is
necessary, and moreover it must boil; for as it cools most of the
dissolved Selenites takes a solid form, and falls in a powder to the
bottom of the vessel.

If an Alkali be presented to the Selenites, or to Alum, these
Salts, according to the principles we have laid down, will be
thereby decomposed; that is, the Acid will quit the earths, and join
the Alkali, with which it hath a greater affinity. And from this
conjunction of the Vitriolic Acid with a fixed Alkali there results
another sort of Neutral Salt, which is called _Arcanum duplicatum_,
_Sal de duobus_, and _Vitriolated Tartar_, because one of the fixed
Alkalis most in use is called Salt of Tartar.

Vitriolated Tartar is almost as hard to dissolve in water as the
Selenites. It shoots into eight-sided crystals, having the apices of
the pyramids pretty obtuse. Its taste is saltish, inclining to bitter;
and it decrepitates on burning coals. It requires a very great degree
of fire to make it flow.

The Vitriolic Acid is capable of uniting with the Phlogiston, or rather
it has a greater affinity with it than with any other body: whence
it follows, that all compounds, of which it makes a part, may be
decomposed by means of the Phlogiston.

From the conjunction of the Vitriolic Acid with the Phlogiston arises
a compound called _Mineral Sulphur_, because it is found perfectly
formed in the bowels of the earth. It is also called _Sulphur vivum_,
or simply _Sulphur_.

Sulphur is absolutely insoluble in water, and incapable of contracting
any sort of union with it. It melts with a very moderate degree of
heat, and sublimes in fine light downy tufts called _Flowers of
Sulphur_. By being thus sublimed, it suffers no decomposition, let
the operation be repeated ever so often; so that Sublimed Sulphur, or
Flower of Sulphur, hath exactly the same properties as Sulphur that has
never been sublimed.

If Sulphur be exposed to a brisk heat in the open air, it takes fire,
burns, and is wholly consumed. This deflagration of Sulphur is the
only means we have of decomposing it, in order to obtain its Acid in
purity. The Phlogiston is destroyed by the flame, and the Acid exhales
in vapours: these vapours collected have all the properties of the
Vitriolic Acid, and differ from it only as they still retain some
portion of the Phlogiston; which, however, soon quits them of its own
accord, if the free access of the common air be not precluded.

The portion of Phlogiston retained by the Acid of Sulphur is much more
considerable when that mineral is burnt gradually and slowly: in that
case the vapours which rise from it have such a penetrating odour,
that they instantaneously suffocate any person who draws in a certain
quantity of them with his breath. These vapours constitute what is
called the _Volatile Spirit of Sulphur_. There is reason to think this
portion of Phlogiston which the Acid retains is combined therewith in a
manner different from that in which these two are united in the Sulphur
itself; for, as has just been observed, nothing but actual burning is
capable of separating the Vitriolic Acid and the Phlogiston, which by
their union form Sulphur; whereas in the Volatile Spirit of Sulphur
they separate spontaneously when exposed to the open air; that is, the
Phlogiston flies off and leaves the Acid, which then becomes in every
respect similar to the Vitriolic Acid.

That the Volatile Spirit of Sulphur is a compound, as we have asserted
it to be, appears evidently from hence, that whenever the Vitriolic
Acid touches any substance containing the Phlogiston, provided that
Phlogiston be disengaged or opened to a certain degree, a Volatile
Spirit of Sulphur is infallibly and immediately generated. This Spirit
hath all the properties of Acids, but considerably weakened, and of
course less perceptible. It unites with absorbent earths or fixed
Alkalis; and with them forms Neutral Salts; but when combined therewith
it may be separated from them by the Vitriolic Acid, and indeed by
any of the mineral Acids, because its affinities are weaker. Sulphur
hath the property of uniting with absorbent earths, but not near so
intimately as with fixed Alkalis.

If equal parts of Sulphur and an Alkali be melted together, they
incorporate with each other; and from their conjunction proceeds a
compound of a most unpleasant smell, much like that of rotten eggs,
and of a red colour nearly resembling that of an animal liver, which
has occasioned it to bear the name of _Hepar Sulphuris_, or _Liver of
Sulphur_.

In this composition the fixed Alkali communicates to the Sulphur the
property of dissolving in water: and hence it comes that Liver of
Sulphur may be made as well when the Alkali is dissolved by water into
a fluid, as when it is fused by the action of fire.

Sulphur has less affinity than any Acid with the fixed Alkalis: and
therefore Liver of Sulphur may be decompounded by any Acid whatever;
which will unite with the fixed Alkali, form therewith a Neutral Salt,
and separate the Sulphur.

If Liver of Sulphur be dissolved in water, and an Acid poured thereon,
the liquor, which was transparent before, instantly turns to an opaque
white; because the Sulphur, being forced to quit its union with the
Alkali, loses at the same time the property of dissolving in water, and
appears again in its own opaque form. The liquor thus made white by the
Sulphur is called _Milk of Sulphur_.

If this liquor be suffered to stand still for some time, the particles
of Sulphur, now most minutely divided, gradually approach each other,
unite, and fall insensibly to the bottom of the vessel; and then the
liquor recovers its transparency. The Sulphur thus deposited on the
bottom of the vessel is called the _Magistery_ or _Precipitate of
Sulphur_. The names of Magistery and Precipitate are also given to all
substances whatever, that are separated from another by this method;
which is the reason that we use the expression of precipitating one
substance by another, to signify the separating one of them by means of
the other.


SECTION II.

_Of the_ NITROUS ACID.

It is not certainly known what constitutes the difference between the
Nitrous Acid and the Vitriolic Acid, with regard to the constituent
principles of each. The most probable opinion is, that the Nitrous Acid
is no other than the Vitriolic Acid combined with a certain quantity of
Phlogiston by the means of putrefaction. If it be so, the Phlogiston
must be united with the Universal Acid in another manner than it is in
sulphur, and in its volatile spirit: for the Nitrous Acid differs from
them both in its properties. What gives ground for this opinion is,
that the Nitrous Acid is never found but in earths and stones which
have been impregnated with matters subject to putrefaction, and which
therefore must contain the Phlogiston. For it is necessary just to
observe here, though it be not yet proper to enter particularly into
the subject, that all substances susceptible of putrefaction really
contain the Phlogiston.

The Nitrous Acid combined with certain absorbent earths, such as chalk,
marle, boles, forms Neutral Salts which do not crystallize; and which,
after being dried, run in the air _per deliquium_.

All those Neutral Salts which consist of the Nitrous Acid joined to an
earth, may be decomposed by a fixed Alkali, with which the Acid unites,
and deserts the earth; and from this union of the Nitrous Acid with a
fixed Alkali results a new Neutral Salt which is called _Nitre_, or
_Salt-peter_. This latter name signifies the _Salt of Stone_; and,
in fact, Nitre is extracted from the stones and plaster, in which it
forms, by boiling them in water saturated with a fixed Alkali.

Nitre shoots in long crystals adhering sideways to each other; it has
a saltish taste, which produces a sensation of cold on the tongue.

This Salt easily dissolves in water; which, when boiling hot, takes up
still a greater quantity thereof.

It flows with a pretty moderate degree of heat, and continues fixed
therein; but being urged by a brisk fire, and in the open air, it lets
go some part of its Acid, and indeed flies off itself in part.

The most remarkable property of Nitre, and that which characterizes it,
is its fulmination or explosion; the nature of which is as follows:

When Nitre touches any substance containing a Phlogiston, and actually
ignited, that is, actually on fire, it bursts out into a flame, burns,
and is decompounded with much noise.

In this deflagration the Acid is dissipated, and totally separated from
the Alkali, which now remains by itself.

Indeed the Acid, at least the greatest part of it, is by this means
quite destroyed. The Alkali which is left when Nitre is decompounded
by deflagration, is called in general _Fixed Nitre_, and, more
particularly, Nitre fixed by such and such a substance as was used
in the operation. But if Nitre be deflagrated with an inflammable
substance containing the vitriolic Acid, as sulphur, for instance,
the fixed Salt produced by the deflagration is not a pure Alkali, but
retains a good deal of the vitriolic Acid, and, by combining therewith,
hath now formed a neutral Salt.

Hitherto Chymists have been at a loss for the reason why Nitre flames,
and is decompounded in the manner above-mentioned, when it comes in
contact with a Phlogiston properly circumstanced. For my part, I
conjecture it to be for the same reason that vitriolated tartar is
also decompounded by the addition of a Phlogiston; _viz._ the Nitrous
Acid, having a greater affinity with the Phlogiston than with the
fixed Alkali, naturally quits the latter to join with the former, and
so produces a kind of sulphur, differing probably from the common
sulphur, formed by the vitriolic Acid, in that it is combustible to
such a degree, as to take fire and be consumed in the very moment of
its production; so that it is impossible to prevent its being thus
destroyed, and consequently impossible to save it. In support of this
opinion let it be considered, that the concurrence of the Phlogiston
is absolutely necessary to produce this deflagration, and that the
matter of pure fire is altogether incapable of effecting it: for though
Nitre be exposed to the most violent degree of fire, even that in the
focus of the most powerful burning-glass, it will not flame; nor will
that effect ever happen till the Nitre be brought into contact with a
Phlogiston properly so called, that is, the matter of fire existing
as a principle of some body; and it is moreover necessary that this
Phlogiston be actually on fire, and agitated with the igneous motion,
or else that the Nitre itself be red hot, and so penetrated with fire
as to kindle any inflammable matter that touches it.

This experiment, among others, helps to shew the distinction that ought
to be made between pure elementary fire, and fire become a principle of
bodies, to which we have given the name of Phlogiston.

Before we leave this subject, we shall observe, that Nitre deflagrates
only with such substances as contain the Phlogiston in its simplest and
purest form; such as charcoal, sulphur, and the metalline substances;
and that, though it will not deflagrate without the addition of some
combustible matter, it is nevertheless the only known body that will
burn, and make other combustibles burn with it, in close vessels,
without the admission of fresh air.

The Nitrous Acid hath not so great an affinity with earths and Alkalis
as the vitriolic Acid hath with the same substances; whence it follows
that the vitriolic Acid decomposes all neutral salts arising from
a combination of the Nitrous Acid with an earth or an Alkali. The
vitriolic Acids expells the Nitrous Acid, unites with the substance
which served it for a basis, and therewith forms a neutral salt, which
is an Alum, a Selenites, or a vitriolated Tartar, according to the
nature of that basis.

The Nitrous Acid, when thus separated from its basis by the vitriolic
Acid, is named _Spirit of Nitre_, or _Aqua Fortis_. If it be
dephlegmated, or contain but little superfluous water, it exhales in
reddish vapours; these vapours, being condensed and collected, form
a liquor of a brownish yellow, that incessantly emits vapours of the
same colour, and of a pungent disagreeable smell. These characters have
procured it the names of _Smoaking Spirit of Nitre_, and _Yellow Aqua
Fortis_. This property in the Nitrous Acid, of exhaling in vapours,
shews it to be less fixed than the vitriolic Acid; for the latter,
though ever so thoroughly dephlegmated, never yields any vapours, nor
has it any smell.


SECTION III.

_Of the_ ACID OF SEA-SALT.

The Acid of Sea-salt is so called because it is in fact obtained from
such Sea-salt as is used in our kitchens. It is not certainly known
in what this Acid differs from the vitriolic and the nitrous, with
regard to its constituent parts. Several of the ablest Chymists, such
as Becher and Stahl, are of opinion that the Marine Acid is no other
than the Universal Acid united to a particular principle which they
call a Mercurial Earth. Concerning this earth we shall have occasion
to say more, when we come to treat of metallic substances: but in the
mean time it must be owned, that the truth of this opinion is so far
from being proved by a sufficient number of experiments, that the
very existence of such a mercurial earth is not yet well established;
and therefore, that we may not exceed the bounds of our knowledge,
we shall content ourselves with delivering here the properties which
characterize the Acid in question, and by which it is distinguished
from the two others considered above.

When it is combined with absorbent earths, such as lime and chalk,
it forms a neutral salt that does not crystallize, and, when dried,
attracts the moisture of the air. If the absorbent earth be not fully
saturated with the Marine Acid, the salt thereby formed has the
properties of a fixed Alkali: and this is what made us say, when we
were on the subject of those salts, that they might be imitated by
combining an earth with an Acid. The Marine Acid, like the rest, hath
not so great an affinity with earths as with fixed Alkalis.

When it is combined with the latter, it forms a neutral salt which
shoots into cubical crystals. This salt is inclined to grow moist in
the air, and is consequently one of those which water dissolves in
equal quantities, at least as to sense, whether it be boiling hot or
quite cold.

The affinity of this Acid with Alkalis and absorbent Earths is not
so great as that of the vitriolic and nitrous Acids with the same
substances: whence it follows, that, when combined therewith, it may be
separated from them by either of those Acids.

The Acid of Sea-salt, thus disengaged from the substance which served
it for a basis, is called _Spirit of Salt_. When it contains but little
phlegm it is of a lemon colour, and continually emits many white, very
dense, and very elastic vapours; on which account it is named the
_Smoaking Spirit of Salt_. Its smell is not disagreeable, nor much
unlike that of saffron; but extremely quick and suffocating when it
smokes.

The Acid of Sea-salt, like the other two, seems to have a greater
affinity with the Phlogiston, than with fixed Alkalis. We are led
to this opinion by a very curious operation, which gives ground to
think that Sea-salt may be decomposed by the proper application of a
substance containing the Phlogiston.

From the Marine Acid combined with a Phlogiston results a kind
of Sulphur, differing from the common sort in many respects; but
particularly in this property, that it takes fire of itself upon
being exposed to the open air. This combination is called _English
Phosphorus_, _Phosphorus of Urine_, because it is generally prepared
from urine; or, only _Phosphorus_.

This combination of the Marine Acid with a Phlogiston is not easily
effected; because it requires a difficult operation in appropriated
vessels. For these reasons it does not always succeed; and Phosphorus
is so scarce and dear, that hitherto Chymists have not been able to
make on it the experiments necessary to discover all its properties. If
Phosphorus be suffered to burn away in the air, a small quantity of an
acid liquor may be obtained from it, which seems to be spirit of salt,
but either altered, or combined with some adventitious matter; for it
has several properties that are not to be found in the pure Marine
Acid; such as, leaving a fixed fusible substance behind it when exposed
to a strong fire, and being easily combined with the Phlogiston so as
to reproduce a Phosphorus.

Phosphorus resembles sulphur in several of its properties: it is
soluble in oils; it melts with a gentle heat; it is very combustible;
it burns without producing soot; and its flame is vivid and bluish.

From what has been said of the union of the Acid of Sea-salt with a
fixed Alkali, and of the neutral salt resulting therefrom, it may
be concluded that this neutral salt is no other than the common
kitchen-salt. But it must be observed, that the fixed Alkali, which is
the natural basis of the common salt obtained from sea-water, is of a
sort somewhat differing from fixed Alkalis in general, and hath certain
properties peculiar to itself. For,

1. The basis of Sea-salt differs from other fixed Alkalis in this, that
it crystallizes like a neutral salt.

2. It does not grow moist in the air; on the contrary, when exposed
to the air, it loses part of the water that united with it in
crystallization, by which means its crystals lose their transparency,
become, as it were, mealy, and fall into a fine flour.

3. When combined with the vitriolic Acid to the point of saturation,
it forms a neutral salt differing from vitriolated tartar, first,
in the figure of its crystals, which are oblong six-sided solids;
secondly, in its quantity of water, which in crystallization unites
therewith in a much greater proportion than with vitriolated tartar;
whence it follows, that this salt dissolves in water more readily than
vitriolated tartar; thirdly, in that it flows with a very moderate
degree of heat, whereas vitriolated tartar requires a very fierce one.

If the Acid of Sea-salt be separated from its basis by means of the
vitriolic Acid, it is easy to see that, when the operation is finished,
the salt we have been speaking of must be the result. A famous Chymist,
named Glauber, was the first who extracted the Spirit of Salt in
this manner, examined the neutral salt resulting from his process,
and, finding it to have some singular properties, called it his _Sal
mirabile_, or wonderful Salt: on this account it is still called
Glauber's _Sal mirabile_, or plainly _Glauber's Salt_.

4. When the basis of Sea-salt is combined with the nitrous Acid to
the point of saturation, there results a neutral salt, or a sort of
nitre, differing from the common nitre, first, in that it attracts
the moisture of the air pretty strongly; and this makes it difficult
to crystallize; secondly, in the figure of its crystals, which are
parallelopipeds; and this has procured it the name of _Quadrangular
Nitre_.

Common salt, or the neutral salt formed by combining the Marine Acid
with this particular sort of fixed Alkali, has a taste well known to
every body. The figure of its crystals is exactly cubical. It grows
moist in the air, and, when exposed to the fire, it bursts, before it
melts, into many little fragments, with a crackling noise; which is
called the _Decrepitation_ of Sea-salt.

That neutral salt mentioned above, which is formed by combining the
Marine Acid with a common fixed Alkali, and called _Sal febrifugum
Sylvii_, hath also this property.

India furnishes us with a saline substance, known by the name of
_Borax_, which flows very easily, and then takes the form of glass. It
is of great use in facilitating the fusion of metallic substances. It
possesses some of the properties of fixed Alkalis, which has induced
certain Chymists to represent it, through mistake, as a pure fixed
Alkali.

By mixing borax with the vitriolic Acid, Mr. Homberg obtained from
it a salt, which sublimes in a certain degree of heat, whenever such
a mixture is made. This salt has very singular properties; but its
nature is not yet thoroughly understood. It dissolves in water with
great difficulty; it is not volatile, though it rises by sublimation
from the borax. According to Mr. Rouelle's observation, it rises then
only by means of the water which carries it up: for, when once made,
it abides the fiercest fire, flows and vitrifies just as borax does:
provided care be taken to free it previously from moisture by drying
it properly. Mr. Homberg called it _Sedative Salt_, on account of its
medical effects. The sedative salt hath the appearance, and some of the
properties, of a neutral salt; for it shoots into crystals, and does
not change the colour of violets; but it acts the part of an Acid with
regard to Alkalis, uniting with them to the point of saturation, and
thereby forming a true neutral salt. It also acts, like the Acid of
vitriol on all neutral salts; that is, it discharges the Acid of such
as have not the vitriolic Acid in their composition.

Since Mr. Homberg's time it hath been discovered, that a sedative salt
may be made either with the nitrous or with the marine Acid; and that
sublimation is not necessary to extract it from the borax, but that it
may be obtained by crystallization only. For this latter discovery we
are indebted to Mr. Geoffry, as we are to Mr. Lemery for the former.

Since that time M. Baron d'Henouville, an able Chymist, hath shewn that
a sedative salt may be obtained by the means of vegetable Acids; and
hath lately demonstrated, in some excellent papers published in the
collection of Memoirs written by the correspondents of the Academy of
Sciences, that the sedative salt exists actually and perfectly in the
borax, and that it is not produced by mixing Acids with that saline
substance, as it seems all the Chymists before him imagined. This he
proves convincingly from his analysis of borax, (which thereby appears
to be nothing else but the sedative salt united with that fixed Alkali
which is the basis of Sea-salt) and from his regenerating the same
borax by uniting together that Alkali and the sedative salt: a proof
the most complete that can possibly be produced in natural philosophy,
and equivalent to demonstration itself.

In order to finish what remains to be said upon the several sorts of
saline substances, we should now speak of the Acids obtained from
vegetables and animals, and also of the volatile Alkalis: but, seeing
these saline substances differ from those of which we have already
treated, only as they are variously altered by the unions they have
contracted with certain principles of vegetables and animals, of which
nothing has been yet said, it is proper to defer being particular
concerning them, till we have explained those principles.



CHAP. V.

_Of_ LIME.


Any substance whatever, that has been roasted a considerable time in
a strong fire without melting, is commonly called a _Calx_. Stones
and metals are the principal subjects that have the property of being
converted into _Calces_. We shall treat of Metalline _Calces_ in a
subsequent chapter, and in this confine ourselves to the _Calx_ of
_Stone_, known by the name of _Lime_.

In treating of earths in general we observed that they may be divided
into two principal kinds; one of which actually and properly flows when
exposed to the action of fire, and turns to glass; whence it is called
a _fusible_ or _vitrifiable_ earth; the other resists the utmost force
of fire, and is therefore said to be an _unfusible_ or _unvitrifiable_
earth. The latter is also not uncommonly called _calcinable_ earth;
though sundry sorts of unfusible earths are incapable of acquiring by
the action of fire all the qualities of _calcined_ earth, or _Lime_
properly so called: such earths are particularly distinguished by the
denomination of _refractory_ earths.

As the different sorts of stones are nothing more than compounds of
different earths, they have the same properties with the earths of
which they are composed, and may, like them, be divided into fusible
or vitrifiable, and unfusible or calcinable. The fusible stones are
generally denoted by the name of _Flints_; the calcinable stones,
again, are the several sorts of marbles, cretaceous stones, those
commonly called free-stones, _&c._ some of which, as they make the best
Lime, are, by way of eminence, called _Lime-stones_. Sea-shells, also,
and stones that abound with fossile shells, are capable of being burnt
to Lime.

All these substances, being exposed, for a longer or shorter time, as
the nature of each requires, to the violent action of fire, are said to
be _calcined_. By calcination they lose a considerable part of their
weight, acquire a white colour, and become friable though ever so solid
before; as, for instance, the very hardest marbles. These substances,
when thus calcined, take the name of _Quick Lime_.

Water penetrates Quick Lime, and rushes into it with vast activity.
If a lump of newly calcined Lime be thrown into water, it instantly
excites almost as great a noise, ebullition, and smoke, as would be
produced by a piece of red-hot iron; with such a degree of heat too,
that, if the Lime be in due proportion to the water, it will set fire
to combustible bodies; as hath unfortunately happened to vessels laden
with Quick Lime, on their springing a small leak.

As soon as Quick Lime is put into water, it swells, and falls asunder
into an infinite number of minute particles: in a word, it is in a
manner dissolved by the water, which forms therewith a sort of white
paste called _Slacked Lime_.

If the quantity of water be considerable enough for the Lime to form
with it a white liquor, this liquor is called _Lac Calcis_; which,
being left some time to settle, grows clear and transparent, the Lime
which was suspended therein, and occasioned its opacity, subsiding to
the bottom of the vessel. Then there forms on the surface of the liquor
a crystalline pellicle, somewhat opaque and dark-coloured, which being
skimmed off is reproduced from time to time. This matter is called
_Cremor Calcis_.

Slacked Lime gradually grows dry, and takes the form of a solid body,
but full of cracks and destitute of firmness. The event is different
when you mix it up, while yet a paste, with a certain quantity of
uncalcined stony matter, such as sand, for example: then it takes
the name of _Mortar_, and gradually acquires, as it grows drier and
older, a hardness equal to that of the best stones. This is a very
singular property of Lime, nor is it easy to account for it: but it is
a beneficial one; for every body knows the use of Mortar in building.

Quick Lime attracts the moisture of the air, in the same manner as
concentrated acids, and dry fixed alkalis; but not in such quantities
as to render it fluid: it only falls into extremely small particles,
takes the form of a fine powder, and the title of _Lime slacked in the
air_.

Lime once slacked, however dry it may afterwards appear, always
retains a large portion of the water it had imbibed; which cannot be
separated from it again but by means of a violent calcination. Being so
recalcined it returns to be Quick Lime, recovering all its properties.

Besides this great affinity of Quick Lime with water, which discovers
a saline character, it has several other saline properties, to be
afterwards examined, much resembling those of fixed alkalis. In
Chymistry it acts very nearly as those salts do, and may be considered
as holding the middle rank between a pure absorbent earth and a fixed
alkali: and this hath induced many Chymists to think that Lime contains
a true salt, to which all the properties it possesses in common with
salts may be attributed.

But as the chymical examination of this subject hath long been
neglected, the existence of a saline substance in Lime hath been long
doubtful. Mr. du Fay, author of some excellent chymical experiments,
was one of the first who obtained a salt from Lime, by lixiviating
it with a great deal of water, which he afterwards evaporated. But
the quantity of salt he obtained by that means was very small; nor
was it of an alkaline nature, as one would think it should have been,
considering the properties of Lime. Mr. du Fay did not carry his
experiments on this subject any further, probably for want of time; nor
did he determine of what nature the salt was.

Mr. Malouin had the curiosity to examine this salt of Lime, and
soon found that it was nothing else but what was above called
_Cremor Calcis_. He found, moreover, that, by mixing a fixed alkali
with lime-water, a vitriolated tartar was formed; that, by mixing
therewith an alkali like the basis of sea-salt, a Glauber's salt was
produced; and, lastly, by combining lime with a substance abounding
in phlogiston, he obtained a true sulphur. These very ingenious
experiments prove to a demonstration, that the vitriolic acid
constitutes the salt of Lime: for, as hath been shewn, no other acid is
capable of forming such combinations. On the other hand, Mr. Malouin,
having forced the vitriolic acid of this salt to combine with a
phlogiston, found its basis to be earthy, and analogous to that of the
selenites: whence he concluded, that the salt of Lime is a true neutral
salt, of the same kind as the selenites. Mr. Malouin tells us he found
several other salts in Lime. But as none of them was a fixed alkali,
and as all the saline properties of Lime have an affinity with those of
that kind of salt, there is great reason to think that all those salts
are foreign to Lime, and that their union with it is merely accidental.

I myself have made several experiments in order to get some insight
into the saline nature of Lime, and shall here produce the result
with all possible conciseness. I took several stones of different
kinds, some of which produced by calcination a very strong Lime, and
others but a very weak one. These I impregnated with different saline
substances, acids, alkalis, and neutrals, and then exposed them all
to the same degree of fire, which was a pretty strong one, and long
enough continued to have made very good Lime of stones the most
difficult to calcine. The consequence was, that, in the first place,
those stones which naturally made but a weak Lime were not, by this
process, converted into a stronger Lime; and, moreover, that none of
these stones, even such as would naturally have produced the most
active Lime, had acquired the properties of Lime. These experiments I
varied many ways, employing different proportions of saline matters,
and almost every possible degree of fire, and constantly observed,
after calcination, that all those stones were so much the farther from
the nature of Lime, as they had been combined with larger doses of
salts. Among those which were impregnated with the greatest proportion
of salts, and had suffered the greatest violence of fire, I observed
some that had begun to flow, and were in a manner vitrified. Now, as
the same subject cannot be, at one and the same time, in the state
of glass and of Lime too; as a body cannot approach to one of these
states but in proportion as it recedes from the other; and as salts in
general dispose those bodies to fusion and vitrification which are in
themselves the most averse to either, I concluded from my experiments,
that the saline substances I used, had, by acting as fluxes upon the
stones, prevented their calcination; that consequently we may suspect
there is no saline matter in the composition of Lime, as Lime; and that
Lime does not owe its saline and alkaline properties to any salt; or at
least that, if it does owe those properties to a salt, such salt must
be naturally and originally combined with the matter of the stone in
so just a proportion, that it is impossible to increase the quantity
thereof without prejudicing the Lime, and depriving it in some measure
of its virtue. This theory agrees perfectly with the illustrious
Stahl's opinion; for he thinks, as we observed in discoursing of salts
in general, that every saline substance is but an earth combined in
a certain manner with water. This notion he applies to Lime, and
says, that fire only subtilizes and attenuates the earthy matter, and
thereby renders it capable of uniting with water in such a manner, that
the result of their combination shall be a substance having saline
properties; and that Lime accordingly never acquires these properties
till it be combined with water.

I have dwelt longer on the Salt of Lime than I shall on any other
particular; because the subject, though in itself of great importance,
has hitherto been but little attended to, and because the experiments
here recited are entirely new.

Lime unites with all acids, and in conjunction with them exhibits
various phenomena.

The vitriolic acid poured upon Lime dissolves it with effervescence and
heat. From this mixture there exhales a great quantity of vapours, in
smell and colour perfectly like those of sea-salt; from which, however,
they are found to be very different when collected into a liquor. From
this combination of the vitriolic acid with Lime arises a neutral salt,
which shoots into crystals, and is of the same kind with the selenetic
salt obtained from Lime by Mr. Malouin.

The nitrous acid poured upon Lime dissolves it in like manner with
effervescence and heat: but the solution is transparent, and therein
differs from the former, which is opaque. From this mixture there
arises a neutral salt, which does not crystallize, and has withal
the very singular property of being volatile, and rising wholly by
distillation in a liquid form. This phenomenon is so much the more
remarkable, as Lime, the basis of this salt, is one of the most fixed
bodies known in Chymistry.

With the acid of sea-salt Lime forms also a singular sort of salt,
which greedily imbibes the moisture of the air. We shall have occasion
to take further notice of it in another place.

These experiments made on Lime with acids are likewise quite new. We
are indebted for them to Mr. Du Hamel of the Academy of Sciences, whose
admirable Memoirs on several subjects shew his extensive knowledge in
all parts of Natural Philosophy.

Lime applied to fixed alkalis adds considerably to their caustic
quality, and makes them more penetrating and active. An alkaline
lixivium in which Lime hath been boiled, being evaporated to dryness,
forms a very caustic substance, which flows in the fire much more
easily, attracts and retains moisture much more strongly, than fixed
alkalis that have not been so treated. An alkali thus acuated by Lime
is called the _Caustic Stone_, or _Potential Cautery_; because it is
employed by surgeons to produce eschars on the skin and cauterize it.



CHAP. VI.

_Of Metallic Substances in general._


Metallic Substances are heavy, glittering, opaque, fusible bodies. They
consist chiefly of a vitrifiable earth united with the phlogiston.

Several Chymists insist on a third principle in these bodies, and have
given it the name of _Mercurial Earth_; which, according to Becher and
Stahl, is the very same that being combined with the vitriolic acid
forms and characterizes the acid of sea-salt. The existence of this
principle hath not yet been demonstrated by any decisive experiment;
but we shall shew that there are pretty strong reasons for admitting it.

We shall begin with mentioning the experiments which prove Metallic
Substances to consist of a vitrifiable earth united with the
phlogiston. The first is this: if they be calcined in such a manner
as to have no communication with any inflammable matter, they will be
spoiled of all their properties, and reduced to an earth or calx, that
has neither the splendour nor the ductility of a metal, and in a strong
fire turns to an actual glass, instead of flowing like a metal.

The second is, that the calx or the glass resulting from a metal thus
decomposed, recovers all its metalline properties by being fused in
immediate contact with an inflammable substance, capable of restoring
the phlogiston of which calcination had deprived it.

On this occasion we must observe, that Chymists have not yet been
able, by adding the phlogiston, to give the properties of metals to
all sorts of vitrifiable earths indiscriminately; but to such only as
originally made a part of some metallic body. For example, a compound
cannot be made with the phlogiston and sand that shall have the least
resemblance of a metal: and this is what seems to point out the reality
of a third principle, as necessary to form the metalline combination.
This principle may probably remain united with the vitrifiable earth
of a metallic substance, when reduced to a glass; whence it follows,
that such vitrified metals require only the addition of a phlogiston to
enable them to appear again in their pristine form.

It may be inferred from another experiment, that the calx and the glass
of a metal are not its pure vitrifiable earth, properly so called: for
by repeated or long-continued calcinations, such a calx or glass may
be rendered incapable of ever resuming the metalline form, in whatever
manner the phlogiston be afterwards applied to it; so that by this
means it is brought into the condition of a pure vitrifiable earth,
absolutely free from any mixture. Those Chymists who patronize the
Mercurial earth, produce many other proofs of the existence of that
principle in Metallic Substances; but they would be misplaced in an
elementary treatise like this.

When by adding the phlogiston to a metallic glass we restore it to the
form of a metal, we are said to _reduce_, _resuscitate_, or _revivify_
that metal.

Metallic Substances are of different kinds, and are divided into
_Metals_ and _Semi-metals_.

Those are called Metals which, besides their metalline splendour
and appearance, are also malleable; that is, have the property of
stretching under the hammer, and by that means of being wrought into
different forms without breaking.

Those which have only the metalline splendour and appearance, without
malleability, are called Semi-metals.

Metals are also further subdivided into two sorts; _viz._ _Perfect_ and
_Imperfect_ Metals.

The Perfect Metals are those which suffer no damage or change whatever
by the most violent and most lasting action of fire.

The Imperfect Metals are those which by the force of fire, may be
deprived of their phlogiston, and consequently of their metalline form.

When but a moderate degree of fire is employed to deprive a Metal of
its phlogiston, the metal is said to be _calcined_; and then it appears
in the form of a powdered earth, which is called a _Calx_: and this
metalline calx being exposed to a more violent degree of fire melts and
turns to glass.

Metallic Substances have an affinity with acids: but not equally with
all; that is, every Metallic Substance is not capable of uniting and
joining with every acid.

When an acid unites with a Metallic Substance there commonly arises
an ebullition, attended with a kind of hissing noise and fuming
exhalations. By degrees, as the union becomes more perfect, the
particles of the metal combining with the acid become invisible: this
is termed _Dissolution_; and when a metalline mass thus appears in an
acid, the metal is said to be _dissolved_ by that acid. It is proper
to observe, that acids act upon Metalline Substances, in one respect,
just as they do upon alkalis and absorbent earths: for an acid cannot
take up above such a certain proportion thereof as is sufficient to
saturate it, to destroy several of its properties, and weaken others.
For example, when an acid is combined with a metal to the point of
saturation, it loses its taste, does not turn the blue colour of a
vegetable red, and its affinity with water is considerably impaired. On
the other hand, Metalline Substances, which when pure are incapable of
uniting with water, by being joined with an acid acquire the property
of dissolving in water. These combinations of Metalline Substances with
acids form different sorts of neutral salts; some of which have the
property of shooting into crystals, while others have it not: most of
them, when thoroughly dried, attract the moisture of the air.

The affinity which Metalline Substances have with acids is less than
that which absorbent earths and fixed alkalis have with the same
acids; so that all metalline salts may be decompounded by one of these
substances, which will unite with the acid, and precipitate the metal.

Metalline Substances thus separated from an acid solvent are called
_Magisteries_ and _Precipitates_ of metals. None of these precipitates,
except those of the perfect metals, retain the metalline form: most of
their phlogiston hath been destroyed by the solution and precipitation,
and must be restored before they can recover their properties. In
short, they are nearly in the same state with Metalline Substances
deprived of their phlogiston by calcination; and accordingly such a
precipitate is called a _Calx_.

A metalline calx prepared in this manner loses a greater or a less
portion of its phlogiston, the more or less effectually and thoroughly
the Metalline Substance, of which it made a part, was dissolved by the
acid.

Metallic Substances have affinities with each other which differ
according to their different kinds: but this is not universal; for some
of them are incapable of any sort of union with some others.

It must be observed, that Metallic Substances will not unite, except
they be both in a similar state; that is, both in a Metalline form, or
both in the form of a Glass; for a Metalline Substance retaining its
phlogiston cannot contract an union with any metallic glass, even its
own.



CHAP. VII.

_Of_ METALS.


There are six Metals, of which two are Perfect and four Imperfect. The
perfect Metals are Gold and Silver; the others are Copper, Tin, Lead,
and Iron. Some Chymists admit a seventh Metal, to wit, Quick-silver:
but as it is not malleable, it has been generally considered as a
metallic body of a particular kind. We shall soon have occasion to
examine it more minutely.

The ancient Chymists, or rather the Alchymists, who fancied a certain
relation or analogy between Metals and the Heavenly Bodies, bestowed
on the seven Metals, reckoning Quick-silver one of them, the names of
the seven Planets of the Ancients, according to the affinity which
they imagined they observed between those several bodies. Thus Gold
was called _Sol_, Silver _Luna_, Copper _Venus_, Tin _Jupiter_, Lead
_Saturn_, Iron _Mars_, and Quick-silver _Mercury_. Though these names
were assigned for reasons merely chimerical, yet they still keep their
ground; so that it is not uncommon to find the Metals called by the
names, and denoted by the characters, of the Planets, in the writings
even of the best Chymists. Metals are the heaviest bodies known in
nature.


SECTION I.

_Of_ GOLD.

Gold is the heaviest of all Metals. The arts of wire-drawing and
gold-beating shew its wonderful ductility. The greatest violence
of fire is not able to produce any alteration in it. Indeed Mr.
Homberg, a famous Chymist, pretended that he had made this metal fume,
and even vitrified it, by exposing it to the focus of one of the
best burning-glasses, known by the name of the Lens of the _Palais
Royal_: but, there are very good reasons for calling in question the
experiments he made on this occasion, or rather for thinking that he
was quite mistaken. For,

1. No man hath since been able to vitrify Gold, though several good
Experimenters have assiduously tried to effect it, by exposing it to
the focus of the same lens, and of other burning-glasses still stronger.

2. It hath been observed, that though Gold, when exposed to the focus
of those glasses, did indeed emit some vapours and decrease in weight;
yet, those vapours being carefully collected on a piece of paper,
proved to be true Gold, in no degree vitrified, and which consequently
had suffered no change but that of being carried away by the violence
of the heat, its nature not being in the least altered.

3. The small portion of vitrified matter, which was formed on the arm
that supported the Gold in Mr. Homberg's experiment, may have come
either from the arm itself, or rather from some heterogeneous particles
contained in the Gold; for it is almost impossible to have it perfectly
pure.

4. Neither Mr. Homberg, nor any that have repeated his experiment, ever
reduced this pretended glass of Gold by restoring its Phlogiston, as is
done with other metallic glasses.

5. To render the experiment decisive, the whole mass of Gold employed
ought to have been vitrified; which was not the case.

Nevertheless, I do not pretend that this metal is in its own nature
absolutely indestructible, and unvitrifiable: but there is reason to
think that no body hath hitherto found the means of producing those
effects on it, probably for want of a sufficient degree of fire; at
least the point is very doubtful.

Gold cannot be dissolved by any pure acid: but if the acid of nitre be
mixed with the acid of sea-salt, there results a compound acid liquor,
with which it has so great an affinity that it is capable of being
perfectly dissolved thereby. The Chymists have called this solvent
_Aqua Regis_, on account of its being the only acid that can dissolve
Gold, which they consider as the King of Metals. The solution of gold
is of a beautiful orange colour.

If Gold dissolved in _aqua regis_ be precipitated by an alkali or an
absorbent earth, the precipitate gently dried, and then exposed to a
certain degree of heat, is instantly dispersed into the air, with a
most violent explosion and noise: Gold thus precipitated is therefore
called _Aurum Fulminans_. But if the precipitated Gold be carefully
washed in plenty of water, so as to clear it of all the adhering saline
particles, it will not fulminate, but may be melted in a crucible
without any additament, and will then appear in its usual form. The
acid of vitriol being poured on _aurum fulminans_ likewise deprives it
of its fulminating quality.

Gold does not begin to flow till it be red-hot like a live coal. Though
it be the most malleable and most ductile of all metals, it has the
singular property of losing its ductility more easily than any of them:
even the fumes of charcoal are sufficient to deprive it thereof, if
they come in contact with it while it is in fusion.

The malleability of this metal, and indeed of all the rest, is also
considerably diminished by exposing it suddenly to cold when it is
red-hot; for example, by quenching it in water, or even barely exposing
it to the cold air.

The way to restore ductility to gold, when lost by its coming in
contact with the vapour of coals, and in general to any metal rendered
less malleable by being suddenly cooled, is to heat it again, to keep
it red hot a considerable time, and then to let it cool very slowly
and gradually; this operation frequently repeated will by degrees much
increase the malleability of a metal.

Pure sulphur hath no effect on Gold; but being combined with an alkali
into a _hepar sulphuris_, it unites therewith very readily. Nay, so
intimate is their union, that the Gold, by means thereof, becomes
soluble in water; and this new compound of Gold and liver of sulphur,
being dissolved in water, will pass through the pores of brown paper
without suffering any decomposition; which does not happen, at least in
such a manifest degree, to other metallic substances dissolved by liver
of sulphur.

_Aurum fulminans_, mixed and melted with flower of sulphur, loses its
fulminating quality: which arises from hence, that on this occasion
the sulphur burns, and its acid, which is the same with the vitriolic,
being thereby set at liberty becomes capable of acting upon the Gold as
a vitriolic acid would; which, as was said above, deprives the Gold of
its fulminating quality.


SECTION II.

_Of_ SILVER.

Next to Gold, Silver is the most perfect metal. Like Gold it resists
the utmost violence of fire, even that in the focus of a burning-glass.
However, it holds only the second place among metals; because it is
lighter than Gold by almost one half; is also somewhat less ductile;
and, lastly, because it is acted upon by a greater number of solvents.

Yet Silver hath one advantage over gold, namely that of being a little
harder; which makes it also more sonorous.

This metal, like Gold, begins to flow when it is so thoroughly
penetrated by the fire as to appear ignited like a live coal.

While this metal is in fusion, the immediate contact of the vapour
of burning coals deprives it almost entirely of its malleability, in
the same manner as we observed happens to Gold: but both these metals
easily recover that property by being melted with nitre.

The nitrous acid is the true solvent of Silver, and being somewhat
dephlegmated will very readily and easily take up a quantity of Silver
equal in weight to itself.

Silver thus combined with the nitrous acid forms a metallic salt which
shoots into crystals, called by the name of _Lunar Crystals_, or
_Crystals of Silver_.

These crystals are most violently caustic: applied to the skin they
quickly affect it much as a live coal would; they produce a blackish
eschar, corroding and entirely destroying the parts they touch.
Surgeons use them to eat away the proud fungous flesh of ulcers. As
Silver united with the nitrous acid hath the property of blackening all
animal substances, a solution of this metallic salt is employed to dye
hair, or other animal matters, of a beautiful and durable black.

These crystals flow with a very moderate heat, and even before they
grow red. Being thus melted they form a blackish mass; and in this
form they are used by Surgeons, under the title of _Lapis Infernalis_,
_Infernal Stone_, or _Lunar Caustic._

Silver is also dissolved by the vitriolic acid: but then the acid must
be concentrated, and in quantity double the weight of the Silver; nor
will the solution succeed without a considerable degree of heat.

Spirit of salt and _aqua regis_, as well as the other acids, are
incapable of dissolving this metal; at least in the ordinary way.

Though Silver be not soluble in the acid of sea-salt, nor easily in the
acid of vitriol, as hath just been observed, it doth not follow that
it hath but a weak affinity with the latter, and none at all with the
former: on the contrary, it appears from experiment that it hath with
these two acids a much greater affinity than with the acid of nitre:
which is singular enough, considering the facility with which this
last acid dissolves it.

The experiment which proves the fact, is this. To a solution of Silver
in the nitrous acid, add the acid either of vitriol or of sea-salt, and
the Silver will instantly quit its nitrous solvent to join with the
superadded acid.

Silver thus united with the vitriolic or the marine acid is less
soluble in water than when combined with the nitrous acid; and for
this reason it is, that when either of these two acids is added to
a solution of Silver, the liquor immediately becomes white, and a
precipitate is formed, which is no other than the Silver united with
the precipitating acid. If the precipitation be effected by the
vitriolic acid, the precipitate will disappear upon adding a sufficient
quantity of water, because there will then be water enough to dissolve
it. But the case is not the same when the precipitation is made by the
marine acid; for Silver combined therewith is scarce soluble in water.

This Precipitate of Silver, procured by means of the marine acid,
is very easily fused, and when fused changes to a substance in some
measure transparent and flexible, which hath occasioned it to be called
by the name of _Luna Cornea_. If it be proposed to decompound this
_luna cornea_, that is, to separate the marine acid from the Silver
with which it is united, the _luna cornea_ must be melted along with
fatty and absorbent matters, with which the acid will unite, and leave
the metal exceeding pure.

It must be observed, that if, instead of the marine acid, sea-salt
in substance be added to a solution of Silver in the nitrous acid, a
Precipitate is also produced, which by fusion appears to be a true
_luna cornea_. The reason is, that the sea-salt is decomposed by the
nitrous acid, which seizes its basis, as having a greater affinity
therewith than its own acid hath; and this acid being consequently
disengaged and set at liberty unites with the Silver, which, as has
been shewn, has a greater affinity with it than with the nitrous acid.
This is an instance of decomposition effected by means of one of those
double affinities mentioned by us in our seventh proposition concerning
Affinities.

From what hath been already said it is clear, that all these
combinations of Silver with acids may be decompounded by absorbent
earths and by fixed alkalis; it being a general law with regard to all
metallic substances. We shall not therefore repeat this observation
when we come to treat of the other metals; unless some particular
occasion require it.

With regard to Silver I must take notice that, when separated by these
means from the acids in which it was dissolved, it requires nothing
but simple fusion to restore it to its usual form; because it does
not, any more than Gold, lose its Phlogiston by those solutions and
precipitations.

Silver unites with sulphur in fusion. If this metal be only made
red-hot in a crucible, and sulphur be then added, it immediately flows;
the sulphur acting as a flux to it. Silver thus united with sulphur
forms a mass that may be cut, is half malleable, and hath nearly the
colour and consistence of Lead. If this sulphurated Silver be kept a
long time in fusion, and in a great degree of heat, the sulphur flies
off and leaves the Silver pure. But if the sulphur be evaporated by a
violent heat, it carries off with it part of the Silver.

Silver unites and mixes perfectly with Gold in fusion. The two metals
thus mixed form a compound with properties partaking of both.

Metallurgists have hitherto sought in vain for a perfectly good and
easy method of separating these two metals by the _dry way_ only: (this
term is used to signify all operations performed by fusion): but they
are conveniently enough parted by the _moist way_, that is, by acid
solvents. This method is founded on the above-mentioned properties of
Gold and Silver with respect to acids. It hath been shewn that _aqua
regis_ only will dissolve Gold; that Silver, on the contrary, is not
soluble by _aqua regis_, and that its proper solvent is the acid of
nitre; consequently, when Gold and Silver are mixed together, if the
compound mass be put into _aqua fortis_, this acid will take up all the
Silver, without dissolving a particle of the Gold, which will therefore
remain pure; and by this means the desired separation is effected. This
method, which is commonly made use of by Goldsmiths, and in Mints, is
called the _Parting Assay_.

It is plain, that if _aqua regis_ were employed instead of _aqua
fortis_, the separation would be equally effected; and that the only
difference between this process and the former would consist in this,
that now the Gold would be dissolved, and the Silver remain pure. But
the operation by _aqua fortis_ is preferable; because _aqua regis_
does take up a little Silver, whereas _aqua fortis_ hath not the least
effect on Gold.

It must be observed, that, when Gold and Silver are mixed together in
equal parts, they cannot be parted by the means of _aqua fortis_. To
enable the _aqua fortis_ to act duly on the Silver, this metal must
be, at least, in a triple proportion to the Gold. If it be in a less
proportion, you must either employ _aqua regis_ to make the separation,
or, if you prefer the use of _aqua fortis_, melt the metalline mass,
and add as much Silver as is necessary to make up the proportion
above-mentioned: and hence this Process is called _Quartation_.

This effect, which is pretty singular, probably arises from hence, that
when the Gold exceeds or even equals the Silver in quantity, the parts
of both being intimately united, the former are capable of coating over
the latter, and covering them so as to defend them from the action of
the _aqua fortis_; which is not the case when there is thrice as much
Silver as Gold.

There is one thing more to be taken notice of with regard to this
process; which is, that perfectly pure _aqua fortis_ is rarely to be
met with, for two reasons; first, it is difficult in making it wholly
to prevent the rising of the medium employed to disengage the nitrous
acid; that is, a little of the vitriolic acid will mix with the vapours
of the _aqua fortis_: secondly, unless the salt-petre be very well
purified it will always hold some small portion of sea-salt, the acid
of which, we know, is very readily set loose by the vitriolic acid,
and consequently rises together with the vapours of the _aqua fortis_.
It is easy to see that _aqua fortis_ mixed either with the one or the
other is not proper for the Parting Process; because, as has just been
said, the vitriolic and the marine acid equally precipitate Silver
dissolved in the nitrous acid; by which means, when they are united
with that acid, they weaken its action upon the Silver, and hinder the
dissolution. Add, that _aqua fortis_ adulterated with a mixture of
spirit of salt becomes an _aqua regis_, and consequently is rendered
capable of dissolving Gold, in proportion as its action upon Silver is
diminished.

In order to remedy this inconvenience, and free _aqua fortis_ from
the vitriolic or marine acid with which it is tainted, Silver must
be dissolved therein: by degrees as the metal dissolves, those
heterogeneous acids lay hold of it, and precipitate with it in the form
of a white powder, as we observed before. This precipitate being wholly
fallen, the liquor grows clear; after which, if it be found capable of
dissolving more silver, without turning milky, it may be depended on as
a perfectly pure _aqua fortis_. Then filtre it, dissolve more Silver
in it, as long as it will take up any, and you will have a solution
of Silver in a very pure _aqua fortis_. By means of this solution may
other _aqua fortis_ be purified: for pour a few drops thereof into
a very impure _aqua fortis_, and immediately the vitriolic or marine
acid, with which that _aqua fortis_ is contaminated, will join the
Silver and fall therewith to the bottom. When the solution of Silver,
prepared as above, does not in the least affect the transparency of
the _aqua fortis_, it is then very pure, and fit for the purposes of
Quartation.

This operation of purifying _aqua fortis_ by a solution of Silver is
called the _Precipitation_ of _Aqua Fortis_, and _aqua fortis_ thus
purified is called _Precipitated Aqua Fortis_.

When Silver is dissolved in _aqua fortis_ it may be separated
therefrom, as hath been shewn, by absorbent earths and fixed alkalis.

We shall see by and by that there are other means of effecting this:
but whatever way it be separated from its solvent it recovers its
metalline form, as Gold does, by being simply fused without any
additament.


SECTION III.

_Of_ COPPER.

Of all the imperfect metals Copper comes the nearest to Gold and
Silver. Its natural colour is a deep-red yellow. It resists a very
violent degree of fire for a considerable time; but losing its
phlogiston at last, it changes its metalline form for that of a calx,
or a pure reddish earth. This calx is hardly, if at all, reducible to
glass, without the addition of something to promote its fusion; all
that the fiercest heat can do being only to render it soft. Copper,
even while it retains its metalline form, and is very pure, requires a
considerable degree of fire to melt it, and does not begin to flow till
long after it is red-hot. When in fusion, it communicates a greenish
colour to the flame of the coals.

This metal is inferior to Silver in point of gravity; nor is its
ductility so great, though it be pretty considerable: but, on the
other hand, it exceeds that metal in hardness. It unites readily with
Gold and Silver; nor does it greatly lessen their beauty when added to
them in a small quantity: nay, it even procures them some advantages;
such as making them harder, and less subject to lose their ductility,
of which those metals are often liable to be deprived, by the mixture
of the smallest heterogeneous particle. This may probably arise from
hence, that the ductility of Copper has the peculiarity of resisting
most of those causes which rob the perfect metals of theirs.

The property, which other metalline substances have in common with
Copper, of losing the phlogiston by calcining and then vitrifying,
furnishes us with a method of separating them from Gold and Silver,
when they are combined therewith. Nothing more is required than to
expose the mass compounded of the perfect metals and other metalline
substances to a degree of heat sufficient to calcine whatever is not
either Gold or Silver. It is evident, that, by this means, these two
metals will be obtained as pure as is possible; for, as hath already
been said, no metalline calx or glass is capable of uniting with metals
possessed of their phlogiston. On this principle is formed the whole
business of refining Gold and Silver.

When the perfect metals have no other alloy but Copper, as this metal
is not to be calcined or vitrified without great difficulty, which is
increased by its union with the unvitrifiable metals, it is easy to see
that it is almost impossible to separate them without adding something
to facilitate the vitrification of the Copper. Such metals as have the
property of turning easily to glass are very fit for this purpose; and
it is necessary to add a certain quantity thereof, when Gold or Silver
is to be purified from the alloy of Copper. We shall have occasion to
be more particular on this subject when we come to treat of Lead.

Copper is soluble in all the acids, to which it communicates a green
colour, and sometimes a blue. Even the neutral salts, and water itself,
act upon this metal. With regard to water indeed, as the procuring
it absolutely pure and free from any saline mixture is next to an
impossibility, it remains a question whether the effect it produces on
Copper be not owing to certain saline particles contained in it. It is
this great facility of being dissolved that renders Copper so subject
to rust; which is nothing else but some parts of its surface corroded
by saline particles contained in the surrounding air and water.

The rust of Copper is always green or blue, or of a colour between
these two. Internally used it is very noxious, being a real poison, as
are all the solutions of this metal made by any acid whatever. The blue
colour which Copper constantly assumes, when corroded by any saline
substance, is a sure sign by which it may be discovered wherever it
exists, even in a very small quantity.

Copper dissolved in the vitriolic acid forms a kind of metalline salt,
which shoots into rhomboidal crystals of a most beautiful blue colour.
These crystals are called _Blue Vitriol_, or _Vitriol of Copper_. They
are sometimes found ready formed in the bowels of the earth; and may
be artificially made by dissolving Copper in the vitriolic acid; but
the solution will not succeed unless the acid be well dephlegmated.
The taste of this vitriol is saltish and astringent. It retains a
considerable quantity of water in crystallizing, on which account it is
easily rendered fluid by fire.

It must be observed, that, when it is exposed to a certain degree of
heat, in order to free it of its humidity, a great part of its acid
flies off at the same time: and hence it is that, after calcination,
there remains only a kind of earth, or metalline calx, of a red colour,
which contains but very little acid. This earth cannot be brought to
flow but with the greatest difficulty.

A solution of Copper in the nitrous acid forms a salt which does not
crystallize, but, when dried, powerfully attracts the moisture of the
air. The same thing happens when it is dissolved in the spirit of salt,
or in _aqua regis_.

If the Copper thus dissolved by any of these acids be precipitated
by an earth or an alkali, it retains nearly the colour it had in the
solution: but these precipitates are scarce any thing more than the
earth of Copper, or Copper deprived of most of its phlogiston; so that
if they were exposed to a violent fire, without any additament, a great
part of them would be converted into an earth that could never be
reduced to a metalline form. Therefore, when we intend to reduce these
precipitates to Copper, it is necessary to add a certain quantity of a
substance capable of restoring to them the phlogiston they have lost.

The substance which hath been found fittest for such reductions is
charcoal-dust; because charcoal is nothing but a phlogiston closely
combined with an earth, which renders it exceedingly fixed, and capable
of resisting a violent force of fire. But as charcoal will not melt,
and consequently is capable of preventing rather than forwarding the
flux of a metalline calx or glass, which nevertheless is essentially
necessary to complete the reduction, it hath been contrived to mix
it, or any other substance containing the phlogiston, with such fixed
alkalis as easily flow, and are fit to promote the flux of other
bodies. These mixtures are called _Reducing Fluxes_; because the
general name of _Fluxes_ is given to all salts or mixtures of salts,
which facilitate fusion.

If Sulphur be applied to Copper made perfectly red-hot, the metal
immediately runs; and these two substances uniting form a new compound
much more fusible than pure Copper.

This compound is destroyed by the sole force of fire, for two reasons:
the first is, that, sulphur being volatile, the fire is capable
of subliming a great part of it, especially when it is in a great
proportion to the Copper with which it is joined; the second is, that
the portion of sulphur which remains, being more intimately united with
the Copper, though it be rendered less combustible by that union, is
nevertheless burnt and consumed in time. Copper being combined with
sulphur, and together with it exposed to the force of fire, is found
to be partly changed into a blue vitriol; because the vitriolic acid,
being disengaged by burning the sulphur, is by that means qualified to
dissolve the Copper. The affinity of Copper with sulphur is greater
than that of Silver.

This metal, as well as the other imperfect metals and the semi-metals,
being mingled with nitre and exposed to the fire, is decomposed and
calcined much sooner than by itself; because the phlogiston which it
contains occasions the deflagration of the nitre, and consequently
the two substances mutually decompose each other. There are certain
metalline substances whose phlogiston is so abundant, and so weakly
connected with their earth, that when they are thus treated with nitre,
there arises immediately a detonation, accompanied with flame, and as
violent as if sulphur or charcoal-dust had been employed; so that in a
moment the metalline substance loses its phlogiston, and is calcined.
The nitre, after these detonations, always assumes an alkaline
character.


SECTION IV.

_Of_ IRON.

Iron is lighter and less ductile than Copper; but it is much harder,
and of more difficult fusion.

It is the only body that has the property of being attracted by the
magnet, which therefore serves to discover it wherever it is. But it
must be observed, that it hath this property only when in its metalline
state, and loses it when converted to an earth or calx. Hence very few
Iron-ores are attracted by the load-stone: because, for the most part,
they are only sorts of earths, which require a phlogiston to be added
before they can be brought to the form of true Iron.

When Iron hath undergone no other preparation but the fusion which is
necessary to smelt it from its ore, it is usually quite brittle, and
flies to pieces under the hammer: which arises in some measure from its
containing a certain portion of unmetallic earth interposed between its
parts. This we call _Pig Iron_.

By melting this a second time it is rendered purer, and more free from
heterogeneous matters: but still, as its proper parts are probably not
brought sufficiently near, or closely enough united, till the Iron hath
undergone some further preparation besides that of fusion, it seldom
hath any degree of malleability.

The way to give it this property is to make it just red-hot, and then
hammer it for some time in all directions; to the end that its parts
may be properly united, incorporated, and welded together, and that
the heterogeneous matters which keep them asunder may be separated.
Iron made by this means as malleable as possible we call _Bar Iron_, or
_Forged Iron_.

Bar Iron is still harder to fuse than Pig Iron: to make it flow
requires the utmost force of fire.

Iron has the property of imbibing a greater quantity of phlogiston
than is necessary to give it the metalline form. It may be made to
take in this super-abundant phlogiston two ways: the first is by fusing
it again with matters that contain the phlogiston; the second is, by
encompassing it with a quantity of such matters, charcoal-dust, for
instance, and then exposing it so encompassed, for a certain time, to
a degree of fire barely sufficient to keep it red-hot. This second
method, whereby one substance is incorporated with another by means
of fire, but without fusing either of them, is in general called
_Cementation_.

Iron thus impregnated with an additional quantity of phlogiston is
called _Steel_. The hardness of Steel may be considerably augmented by
_tempering_ it; that is, by making it red-hot, and suddenly quenching
it in some cold liquor. The hotter the metal, and the colder the
liquor in which it is quenched, the harder will the Steel be. By this
means tools are made, such as files and sheers, capable of cutting
and dividing the hardest bodies, as glass, pebbles, and Iron itself.
The colour of Steel is darker than that of Iron, and the facets which
appear on breaking it are smaller. It is also less ductile and more
brittle, especially when tempered.

As Iron may be impregnated with an additional quantity of phlogiston,
and thereby converted into Steel, so may Steel be again deprived
of that super-abundant phlogiston, and brought back to the condition
of Iron. This is effected by cementing it with poor earths, such
as calcined bones and chalk. By the same operation Steel may be
_untempered_; nay, it will lose the hardness it had acquired by
tempering, if it be but made red-hot, and left to cool gradually. As
Iron and Steel differ only in the respects we have here taken notice
of, their properties being in all other respects the same, what follows
is equally applicable to both.

Iron being exposed to the action of fire for some time, especially when
divided into small particles, such as filings, is calcined and loses
its phlogiston. By this means it turns to a kind of reddish yellow
earth, which, on account of its colour, is called _Crocus Martis_, or
_Saffron of Mars_.

This calx of Iron has the singular property of flowing in the fire
with somewhat less difficulty than Iron itself; whereas every other
metalline calx flows with less ease than the metal that produced it. It
has moreover the remarkable property of uniting with the phlogiston,
and of being reduced to Iron without fusion; requiring for that purpose
only to be made red-hot.

Iron may be incorporated with Silver, and even with Gold, by means of
certain operations. Under the article of Lead we shall see how it may
be separated from these metals.

The acids produce on it much the same effects as on Copper; every one
of them acts upon it. Certain neutral salts, alkalis, and even water
itself, are capable of dissolving it; and hence it is also very subject
to rust. The vitriolic acid dissolves it with the greater ease: but
the circumstances which attend the solution thereof are different from
those with which the same Acid dissolves Copper: for, 1. whereas the
vitriolic acid must be concentrated to dissolve Copper, it must on
the contrary be diluted with water to dissolve Iron, which it will
not touch when well dephlegmated. 2. The vapours which rise in this
dissolution are inflammable; so that if it be made in a small-necked
bottle, and the flame of a candle be applied to the mouth thereof, the
vapours in the bottle take fire with such rapidity as to produce a
considerable explosion.

This solution is of a beautiful green colour; and from this union of
the vitriolic acid with Iron there results a neutral metalline salt,
which has the property of shooting into crystals of a rhomboidal
figure, and a green colour. These crystals are called _Green Vitriol_,
_Vitriol of Mars_, and _Copperas_.

Green Vitriol hath a saltish and astringent taste. As it retains a
great deal of water in crystallizing, it quickly flows by the action
of fire: but this fluidity is owing to its water only, and is not a
real fusion; for, as soon as its moisture is evaporated, it resumes a
solid form. Its green transparent colour is now changed into an opaque
white: and, if the calcination be continued, its acid also exhales and
is dissipated in vapours; and as it loses that, it turns gradually to
a yellow colour, which comes so much the nearer to a red the longer
the calcination is continued, or the higher the force of the fire is
raised; which being driven to the utmost, what remains is of a very
deep red. This remainder is nothing but the body of the Iron, which
having lost its phlogiston is now no more than an earth, nearly of the
same nature with that which is left after calcining the metal itself.

Green Vitriol dissolved in water spontaneously lets fall a yellowish
earthy sediment. If this solution be defecated by filtration, it still
continues to deposite some of the same substance, till the vitriol be
wholly decomposed. This sediment is nothing but the earth of Iron,
which is then called _Ochre_.

The nitrous acid dissolves Iron with great ease. This solution is of a
yellow colour, inclining more or less to a russet, or dark-brown, as it
is more or less saturated with Iron. Iron dissolved by this acid, also,
falls spontaneously in a kind of calx, which is incapable of being
dissolved a second time; for the nitrous acid will not act upon Iron
that has lost its phlogiston. This solution does not crystallize, and
if evaporated to dryness attracts the moisture of the air.

Spirit of salt likewise dissolves Iron, and this solution is green. The
vapours which rise during the dissolution are inflammable, like those
which ascend when this metal is attacked by the vitriolic acid. _Aqua
regis_ makes a solution of Iron, which is of a yellow colour.

Iron hath a greater affinity than either Silver or Copper with the
nitrous and vitriolic acids: so that if iron be presented to a solution
of either in one of these two acids, the dissolved metal will be
precipitated; because the acid quits it for the Iron, with which it has
a greater affinity.

On this occasion it must be observed, that if a solution of Copper in
the vitriolic acid be precipitated by means of Iron, the precipitate
has the form and splendour of a metal, and does not require the
addition of a phlogiston to reduce it to true Copper; which is not the
case, as has been shewn, when the precipitation is effected by earths
or alkaline salts.

The colour of this metalline precipitate hath deceived several persons,
who being unacquainted with such phenomena, and with the nature of blue
vitriol, imagined that Iron was transmuted into Copper, when they saw
a bit of Iron laid in a solution of that vitriol become, in form and
external appearance, exactly like Copper: whereas the surface only of
the Iron was crusted over with the particles of Copper contained in the
vitriol, which had gradually fallen upon and adhered to the Iron, as
they were precipitated out of the solution.

Among the solvents of Iron we mentioned fixed alkalis; and that they
have such a power is proved by the following phenomenon. If a large
proportion of alkaline salts be suddenly mixed with a solution of Iron
in an acid, no precipitation ensues, and the liquor remains clear and
pellucid; or if at first it look a little turbid, that appearance lasts
but a moment, and the liquor presently recovers its transparency.
The reason is, that the quantity of alkali is more than sufficient
to saturate all the acid of the solution, and the super-abundant
portion thereof, meeting with the Iron already finely divided by the
acid, dissolves it with ease as fast as it falls, and so prevents
its muddying the liquor. To evince that this is so in fact, let the
alkali be applied in a quantity that is not sufficient, or but barely
sufficient, to saturate the acid, and the Iron will then precipitate
like any other metal.

Water also acts upon Iron; and therefore Iron exposed to moisture grows
rusty. If iron-filings be exposed to the dew, they turn wholly to a
rust, which is called _Crocus Martis Aperiens_.

Iron exposed to the fire together with nitre makes it detonate pretty
briskly, sets it in a flame, and decomposes it with rapidity.

This metal hath a greater affinity than any other metalline substance
with sulphur; on which account it is successfully used to precipitate
and separate all metalline substances combined with sulphur.

Sulphur uniting with Iron communicates to it such a degree of
fusibility, that if a mass of this metal heated red-hot be rubbed with
a bit of sulphur, it incessantly runs into as perfect a fusion as a
metal exposed to the focus of a large burning-glass.


SECTION V.

_Of_ TIN.

Tin is the lightest of all metals. Though it yields easily to the
impression of hard bodies, it has but little ductility. Being bent
backwards and forwards it makes a small crackling noise. It flows with
a very moderate degree of fire, and long before it comes to be red-hot.
When it is in fusion, its surface soon grows dusty, and there forms
upon it a thin dark-coloured dusty pellicle, which is no other than a
part of the Tin that has lost its phlogiston, or a calx of Tin. The
metal thus calcined easily recovers its metalline form on the addition
of a phlogiston. If the calx of Tin be urged by a strong fire it grows
white, but the greatest violence of heat will not fuse it; which makes
some Chymists consider it as a calcinable or absorbent earth, rather
than a vitrifiable one. Yet it turns to glass, in some sort, when mixed
with any other substance that vitrifies easily. However, it always
produces an imperfect glass only, which is not at all transparent, but
of an opaque white. The calx of Tin thus vitrified is called _Enamel_.
Enamels are made of several colours by the addition of this or that
metalline calx.

Tin unites easily with all the metals; but it destroys the ductility
and malleability of every one of them, Lead excepted. Nay, it possesses
this property of making metals brittle in such an eminent degree, that
the very vapour of it, when in fusion, is capable of producing this
effect. Moreover, which is very singular, the most ductile metals, even
Gold and Silver, are those on which it works this change with the most
ease, and in the greatest degree. It has also the property of making
Silver mixed with it flow over a very small fire.

It adheres to, and in some measure incorporates with, the surface of
Copper and of Iron; whence arose the practice of coating over those
metals with Tin. Tin plates are no other than thin plates of Iron
tinned over.

If to twenty parts of Tin one part of Copper be added, this alloy
renders it much more solid, and the mixed mass continues tolerably
ductile.

If, on the contrary, to one part of Tin ten parts of Copper be added,
together with a little Zink, a semi-metal to be considered hereafter,
from this combination there results a metalline compound which is hard,
brittle, and very sonorous; so that it is used for casting bells: this
composition is called _Bronze_ and _Bell-metal_.

Tin hath an affinity with the vitriolic, nitrous, and marine acids. All
of them attack and corrode it; yet none of them is able to dissolve
it without great difficulty: so that if a clear solution thereof be
desired, particular methods must be employed for that purpose; for the
acids do but in a manner calcine it, and convert it to a kind of white
calx or precipitate. The solvent which has the greatest power over it
is _aqua regis_, which has even a greater affinity therewith than with
Gold itself; whence it follows, that Gold dissolved in _aqua regis_
may be precipitated by means of Tin; but then the _aqua regis_ must be
weakened. Gold thus precipitated by Tin is of a most beautiful colour,
and is used for a red in enameling and painting on porcelain, as also
to give a red colour to artificial gems. If the _aqua regis_ be not
lowered, the precipitate will not have the purple colour.

Tin hath the property of giving a great lustre to all red colours
in general; on which account it is used by the dyers for striking a
beautiful scarlet, and tin vessels are employed in making fine syrup
of violets. Water does not act upon this metal, as it does upon Iron
and Copper; for which reason it is not subject to rust: nevertheless,
when it is exposed to the air, its surface soon loses its polish and
splendour.

Tin mixed with nitre and exposed to the fire deflagrates with it, makes
it detonate, and is immediately converted to a _refractory calx_: for
so all substances are called which are incapable of fusion.

Tin readily unites with sulphur, and with it becomes a brittle and
friable mass.


SECTION VI.

_Of_ LEAD.

Next to Gold and Mercury Lead is the heaviest of all metalline
substances, but in hardness is exceeded by every one of them. Of all
metals also it melts the easiest except Tin. While it is in fusion
there gathers incessantly on its surface, as on that of Tin, a blackish
dusty pellicle, which is nothing but a calx of Lead.

This calx further calcined by a moderate fire, the flame being
reverberated on it, soon grows white. If the calcination be continued
it becomes yellow, and at last of a beautiful red. In this state it
is called _Minium_, and is used as a pigment. _Minium_ is not easily
made, and the operation succeeds well in large manufactures only.

To convert Lead into _Litharge_, which is the metal in a manner half
vitrified, you need only keep it melted by a pretty strong fire; for
then as its surface gradually calcines, it tends more and more to
fusion and vitrification.

All these preparations of Lead are greatly disposed to perfect fusion
and vitrification, and for that purpose require but a moderate degree
of fire; the calx or earth of Lead being of all metalline earths that
which vitrifies the most easily.

Lead hath not only the property of turning into glass with the greatest
facility, but it hath also that of promoting greatly the vitrification
of all the other imperfect metals; and, when it is actually vitrified,
procures the ready fusion of all earths and stones in general, even
those which are refractory, that is, which could not be fused without
its help.

Glass of Lead, besides its great fusibility, hath also the singular
property of being so subtile and active as to corrode and penetrate the
crucibles in which it is melted, unless they be of an earth that is
exceeding hard, compact, and withal very refractory: for Glass of Lead
being one of the most powerful fluxes that we know, if the earth of
the crucible in which it is melted be in the smallest degree fusible,
it will be immediately vitrified; especially if there be any metallic
matter in its composition.

The great activity of Glass of Lead may be weakened by joining it with
other vitrifiable matters: but unless these be added in a very great
proportion, it will still remain powerful enough to penetrate common
earths, and carry off the matters combined with it.

On these properties of Lead, and of the Glass of Lead, depends the
whole business of refining Gold and Silver. It hath been shewn, that as
these two metals are indestructible by fire, and the only ones which
have that advantage, they may be separated from the imperfect metals,
when mixed therewith, by exposing the compound to a degree of fire
sufficiently strong to vitrify the latter; which, when once converted
into glass, can no longer remain united with any metal that has its
metalline form. But it is very difficult to procure this vitrification
of the imperfect metals, when united with Gold and Silver; nay, it
is in a manner impossible to vitrify them entirely, for two reasons:
first, because most of them are naturally very difficult to vitrify;
secondly, because the union they have contracted with the perfect
metals defends them, in a manner, from the action of the fire, and that
so much the more effectually as the proportion of the perfect metals
is greater; which being indestructible, and in some sort coating over
those with which they are alloyed, serve them as a preservative and
impenetrable shield against the utmost violence of fire.

It is therefore clear, that a great deal of labour may be saved, and
that Gold and Silver may be refined to a much greater degree of purity
than can otherwise be obtained, if to a mixture of these metals with
Copper, for instance, or any other imperfect metal be added a certain
quantity of Lead. For the Lead, by its known property, will infallibly
produce the desired vitrification; and as it likewise increases
the proportion of the imperfect metals, and so lessens that of the
perfect metals, in the mass, it evidently deprives the former of a
part of their guard, and so effects a more complete vitrification. In
conclusion, as the Glass of Lead hath the property of running through
the crucible, and carrying with it the matters which it has vitrified,
it follows, that, when the vitrification of the imperfect metals is
effected by its means, all those vitrified matters together penetrate
the vessel containing the fused metalline mass, disappear, and leave
only the Gold and Silver perfectly pure, and freed, as far as is
possible, from all admixture of heterogeneous parts.

The better to promote the separation of such parts it is usual to
employ, in this process, a particular sort of small crucibles, made of
the ashes of calcined bones, which are exceedingly porous and easily
pervaded. They are called _cupels_, on account of their figure, which
is that of a wide-mouthed cup: and from hence the operation takes its
name; for when we refine Gold and Silver in this manner we are said
to _cupel_ those metals. It is easy to perceive that the more Lead is
added the more accurately will the Gold and Silver be refined; and
that so much the more Lead ought to be added as the perfect metals are
alloyed with a greater proportion of the imperfect. This is the most
severe trial to which a perfect metal can be put; and consequently any
metal that stands it may be fairly considered as such.

In order to denote the fineness of Gold, it is supposed to be divided
into twenty-four parts called _carats_; and Gold which is quite pure
and free from all alloy is said to be twenty-four _carats fine_; that
which contains 1/24 part of alloy is called Gold of twenty-three
carats; that which contains 2/24 of alloy is but twenty-two carats; and
so on. Silver again is supposed to be divided into twelve parts only,
which are called _penny-weights_: so that when absolutely pure it is
said to be twelve _penny-weights fine_; when it contains 1/12 of alloy,
it is then called eleven penny-weights fine; when it contains 2/12 of
alloy, it is called ten penny-weights fine, and so on.

In treating of Copper we promised to shew, under the article of Lead,
how to separate it from Iron. The process is founded on that property
of Lead which renders it incapable of mixing and uniting with Iron,
though it readily dissolves all other metalline substances. Therefore,
if you have a mass compounded of Copper and Iron, it must be fused
with a certain quantity of Lead, and then the Copper, having a greater
affinity with Lead than with Iron, will desert the latter and join the
former, which being incapable of any union with Iron, as was said, will
wholly exclude it from the new compound. The next point is to separate
the Lead from the Copper; which is done by exposing the mass compounded
of these two metals to a degree of fire strong enough to deprive the
Lead of its metalline form, but too weak to have the same effect on
the Copper: and this may be done; since, of all the imperfect metals,
Lead is, next to Tin, the easiest to be calcined, and Copper on the
contrary resists the greatest force of fire longest, without losing its
metalline form. Now what we gain by this exchange, viz. by separating
Copper from Iron and uniting it with Lead, consists in this, that as
Lead is calcined with less fire than Iron, the Copper is less exposed
to be destroyed: for it must be observed that, however moderate the
fire be, it is hardly possible to prevent a certain quantity thereof
from being calcined in the operation.

Lead melted with a third part of Tin forms a compound, which being
exposed to a fire capable of making it thoroughly red-hot, swells,
puffs up, seems in some sort to take fire, and is presently calcined.
These two metals mixed together are much sooner calcined than either of
them separately.

Both Lead and Tin are in some measure affected by water, and by a moist
air; but they are both much less subject than Iron or Copper to be
corroded by these solvents, and of course are much less liable to rust.

The vitriolic acid acts upon and dissolves Lead, much in the same
manner as it doth Silver.

The nitrous acid dissolves this metal with much ease, and in great
quantities; and from this solution a small portion of Mercury may
be obtained. On this subject see our _Elements of the Practice of
Chymistry_.

When this solution of Lead is diluted with a good deal of water, the
Lead precipitates in the form of a white powder; which happens because
the acid is rendered too weak to keep the Lead dissolved.

If this solution of Lead be evaporated to a certain degree, it shoots
into crystals formed like regular pyramids with square bases. These
crystals are of a yellowish colour, and a saccharine taste: they do not
easily dissolve in water. This nitrous metalline salt has the singular
property of detonating in a crucible, without any additament, or the
contact of any other inflammable substance. This property it derives
from the great quantity of phlogiston contained in, and but loosely
connected with, the Lead which is one of its principles.

If spirit of salt, or even sea-salt in substance, be added to a
solution of Lead in the nitrous acid, a white precipitate immediately
falls; which is no other than the Lead united with the marine acid.
This precipitate is extremely like the precipitate of Silver made in
the same manner, and that being called _Luna cornea_ hath occasioned
this to be named _Plumbum corneum_. Like the _luna cornea_ it is
very fusible, and being melted hardens like it into a kind of horny
substance: it is volatile, and may be reduced by means of inflammable
matters combined with alkalis. But it differs from the _luna cornea_
in this chiefly, that it dissolves easily in water; whereas the _luna
cornea_, on the contrary, dissolves therein with great difficulty, and
in a very small quantity.

As this precipitation of Lead from its solution in spirit of nitre is
procured by the marine acid, Lead is thereby proved to have a greater
affinity with the latter acid than with the former. Yet, if you attempt
to dissolve Lead directly by the acid of sea-salt, the solution is
not so easily effected as by the spirit of nitre, and it is always
imperfect; for it wants one of the conditions essential to every
solution in a liquor, namely transparency.

If Lead be boiled for a long time in a lixivium of fixed alkali, part
of it will be dissolved.

Sulphur renders this metal refractory and scarce fusible; and the
mass they form when united together is friable. Hence it appears that
sulphur acts upon Lead much in the same manner as upon Tin; that is, it
renders both these metals less fusible, which are naturally the most
fusible of any, while it exceedingly facilitates the fusion of Silver,
Copper, and Iron, metals which of themselves flow with the greatest
difficulty.



CHAP. VIII.

_Of_ QUICK-SILVER.


We treat of Quick-silver in a chapter apart, because this metallic
substance cannot be classed with the metals properly so called, and
yet has some properties which will not allow us to confound it with
the semi-metals. The reason why Quick-silver, by the Chymists commonly
called Mercury, is not reputed a metal, is, that it wants one of the
essential properties thereof, to wit, malleability. When it is pure
and unadulterated with any mixture, it is always fluid, and of course
unmalleable. But as, on the other hand, it eminently possesses the
opacity, the splendour, and, above all, the gravity of a metal, being
next to Gold the heaviest of all bodies, it may be considered as a true
metal, differing from the rest no otherwise than by being constantly in
fusion; which we may suppose arises from its aptness to flow with such
a small degree of heat, that be there ever so little warmth on earth,
there is still more than enough to keep Mercury in fusion; which would
become solid and malleable if it were possible to apply to it a degree
of cold considerable enough for that purpose. These properties will not
allow us to confound it with the semi-metals. Add, that we are not yet
assured by any undoubted experiment that it can be wholly deprived of
its phlogiston, as the imperfect metals may. Indeed we cannot apply the
force of fire to it as could be wished: for it is so volatile that it
flies off and exhales in vapours, with a much less degree of fire than
is necessary to make it red-hot. The vapours of Mercury thus raised by
the action of fire, being collected and united in a certain quantity,
appear to be no other than true Mercury, retaining every one of its
properties; and no experiment hath ever been able to shew the least
change thus produced in its nature.

If Mercury be exposed to the greatest heat that it can bear without
sublimation, and continued in it for several months, or even a whole
year together, it turns to a red powder, which the Chymists call
_Mercurius Præcipitatus per se_. But, to succeed in this operation, it
is absolutely necessary that the heat be such as is above-specified;
for this metallic substance may remain exposed to a weaker heat for
a considerable number of years, without undergoing any sensible
alteration.

Some Chymists fancied, that by this operation they had fixed Mercury
and changed its nature; but without any reason: for if the Mercury
thus seemingly transmuted be exposed to a somewhat stronger degree of
fire, it sublimes and exhales in vapours as usual; and those vapours
collected are nothing else but running Mercury, which has recovered all
its properties without the help of any additament.

Mercury has the property of dissolving all the metals, Iron only
excepted. But it is a condition absolutely necessary to the success of
such dissolution, that the metalline substances be possessed of their
phlogiston; for if they be calcined, Mercury cannot touch them: and
hence it follows, that Mercury doth not unite with substances that are
purely earthy. Such a combination of a metal with Mercury is called an
_Amalgam_. Trituration alone is sufficient to effect it; however, a
proper degree of heat also is of use.

Mercury amalgamated with a metal gives it a consistence more or less
soft, and even fluid, according to the greater or smaller proportion of
Mercury employed. All amalgams are softened by heat, and hardened by
cold.

Mercury is very volatile; vastly more so than the most unfixed metals;
moreover, the union it contracts with any metal is not sufficiently
intimate to entitle the new compound resulting from that union to all
the properties of the two substances united: at least with regard to
their degree of fixity and volatility. From all which it follows, that
the best and surest method of separating it from metals dissolved by
it, is to expose the amalgam to a degree of heat sufficient to make
all the Quick-silver rise and evaporate; after which the metal remains
in the form of a powder, and being fused recovers its malleability.
If it be thought proper to save the Quick-silver, the operation must
be performed in close vessels, which will confine and collect the
mercurial vapours. This operation is most frequently employed to
separate Gold and Silver from the several sorts of earths and sands
with which they are mixed in the ore; because these two metals, Gold
especially, are of sufficient value to compensate the loss of Mercury,
which is inevitable in this process: besides, as they very readily
amalgamate with it, this way of separating them from every thing
unmetallic is very facile and commodious.

Mercury is dissolved by acids; but with circumstances peculiar to each
particular sort of acid.

The vitriolic acid, concentrated and made boiling hot, seizes on
it, and presently reduces it to a kind of white powder, which turns
yellow by the affusion of water, but does not dissolve in it; it is
called _Turbith Mineral_. However, the vitriolic acid on this occasion
unites with a great part of the Mercury, in such a manner that the
compound is soluble in water. For if to the water which was used to
wash the Turbith a fixed alkali be added, there falls instantly a
russet-coloured precipitate, which is no other than Mercury separated
from the vitriolic acid by the intervention of the alkali.

This dissolution of Mercury by the vitriolic acid is accompanied with
a very remarkable phenomenon; which is, that the acid contracts a
strong smell of volatile spirit of sulphur: a notable proof that part
of the phlogiston of the Mercury hath united therewith. And yet, if the
Mercury be separated by means of a fixed alkali, it does not appear to
have suffered any alteration. Turbith mineral is not so volatile as
pure Mercury.

The nitrous acid dissolves Mercury with ease. The solution is limpid
and transparent, and as it grows cold shoots into crystals, which are a
nitrous mercurial salt.

If this solution be evaporated to dryness, the Mercury remains
impregnated with a little of the acid, under the form of a red powder,
which hath obtained the names of _Red Precipitate_, and _Arcanum
Corallinum_. This Precipitate, as well as Turbith, is less volatile
than pure Mercury.

If this solution of Mercury be mixed with a solution of Copper, made
likewise in the nitrous acid, and the mixture evaporated to dryness,
there will remain a green powder called _Green Precipitate_. These
precipitates are caustic and corrosive; and are used as such in surgery.

Though Mercury be dissolved more easily and completely by the nitrous
acid than by the vitriolic, yet it has a greater affinity with the
latter than with the former: for if a vitriolic acid be poured into
a solution of Mercury in spirit of nitre, the Mercury will quit the
latter acid in which it was dissolved, and join the other which was
added. The same thing happens when the marine acid is employed instead
of the vitriolic.

Mercury combined with spirit of salt forms a singular body; a metalline
salt which shoots into long crystals, pointed like daggers. This
salt is volatile, and sublimes easily without decomposition. It is
moreover the most violent of all the corrosives hitherto discovered
by Chymistry. It is called _Corrosive Sublimate_, because it must
absolutely be sublimed to make the combination perfect. There are
several ways of doing this: but the operation will never fail, if the
Mercury be rarefied into vapours, and meet with the marine acid in a
similar state.

Corrosive Sublimate is dissolved by water, but in very small quantities
only. It is decompounded by fixed alkalis, which precipitate the
Mercury in a reddish yellow powder, called, on account of its colour,
_Yellow Precipitate_.

If Corrosive Sublimate be mixed with tin, and the compound distilled,
a liquor comes over which continually emits abundance of dense fumes,
and, from the name of its inventor, is called the _Smoking Liquor
of Libavius_. This liquor is no other than the tin combined with
the marine acid of the Corrosive Sublimate, which therefore it hath
actually decompounded: whence it follows, that this acid hath a greater
affinity with tin than with Mercury.

The marine acid in Corrosive Sublimate is not quite saturated with
Mercury; but is capable of taking up a much greater quantity thereof.
For if Corrosive Sublimate be mixed with fresh Mercury, and sublimed
a second time, another compound will be produced containing much more
Mercury, and less acrimonious; for which reason it is named _Sweet
Sublimate of Mercury_, _Mercurius dulcis_, _Aquila alba_. This compound
may be taken internally, and is purgative or emetic according to the
dose administered. It may be rendered still more gentle by repeated
sublimations, and then it takes the title of _Panacea Mercurialis_.
No way hath hitherto been found to dissolve Mercury in _aqua regis_
without great difficulty, and even then it is but imperfectly dissolved.

Mercury unites easily and intimately with sulphur. If these two
substances be only rubbed together in a gentle heat, or even without
any heat, they will contract an union, though but an incomplete one.
This combination takes the form of a black powder, which has procured
it the name of _Æthiops Mineral_.

If a more intimate and perfect union be desired, this compound must be
exposed to a stronger heat; and then a red ponderous substance will
be sublimed, appearing like a mass of shining needles: this is the
combination desired, and is called _Cinabar_. In this form chiefly
is Mercury found in the bowels of the earth. Cinabar finely levigated
acquires a much brighter red colour, and is known to painters by the
name of _Vermilion_.

Cinabar rises wholly by sublimation, without suffering any
decomposition; because the two substances of which it consists, _viz._
Mercury and Sulphur, are both volatile.

Though Mercury unites and combines very well with sulphur, as hath
been said, yet it hath less affinity with that mineral than any other
metal, Gold only excepted: whence it follows, that any of the other
metals will decompound Cinabar, by uniting with its sulphur, and so
setting the Mercury at liberty to appear in its usual form. Mercury
thus separated from sulphur is esteemed the purest, and bears the name
of _Mercury revivified from Cinabar_.

Iron is generally used in this operation, preferably to the other
metals, because among them all it has the greatest affinity with
sulphur, and is the only one that has none with Mercury.

Cinabar may also be decompounded by means of fixed alkalis; the
affinity of these salts with sulphur being generally greater than that
of any metalline substance whatever.



CHAP. IX.

_Of the_ SEMI-METALS.


SECTION I.

_Of_ REGULUS OF ANTIMONY.

Regulus of Antimony is a metallic substance of a pretty bright white
colour. It has the splendour, opacity, and gravity of a metal: but it
is quite unmalleable, and crumbles to dust, instead of yielding or
stretching, under the hammer; on which account it is classed with the
Semi-metals.

It begins to flow as soon as it is moderately red; but, like the other
Semi-metals, it cannot stand a violent degree of fire; being thereby
dissipated into smoke and white vapours, which adhere to such cold
bodies as they meet with, and so are collected into a kind of _farina_
called _Flowers of Antimony_.

If Regulus of Antimony, instead of being exposed to a strong fire, be
only heated so moderately that it shall not even melt, it will calcine,
lose its phlogiston, and take the form of a greyish powder destitute of
all splendour: this powder is called _Calx of Antimony_.

This calx is not volatile like the Regulus, but will endure a very
violent fire; and being exposed thereto will flow, and turn to a glass
of the yellowish colour of a hyacinth.

It is to be observed, that the more the Regulus is deprived of its
phlogiston by continued calcination, the more refractory is the calx
obtained from it. The glass thereof has also so much the less colour,
and comes the nearer to common glass.

The calx and the Glass of Antimony will recover their metalline form,
like every other Calx and Glass of a metal, if reduced by restoring to
them their lost phlogiston. Yet if the calcination be carried too far,
their reduction will become much more difficult, and a much smaller
quantity of Regulus will be resuscitated.

Regulus of Antimony is capable of dissolving the metals: but its
affinities with them are various, and differ according to the following
order. It affects Iron the most powerfully, next Copper, then Tin,
Lead, and Silver. It promotes the fusion of metals, but makes them all
brittle and unmalleable.

It will not amalgamate with Mercury; and though by certain processes,
particularly the addition of water and continued trituration, a sort
of union between these two substances may be produced, yet it is but
apparent and momentary; for, being left to themselves and undisturbed,
they quickly disunite and separate[2].

  [2] M. Malouin, however, hath found a way to unite these two metallic
  substances: but then he does it by the interposition of sulphur; that
  is, he combines crude Antimony with Mercury. This combination is
  brought about in the same way that Æthiops Mineral is made; _viz._
  either by fusion, or by trituration only without fire. It resembles
  the common Æthiops, and M. Malouin calls it _Æthiops of Antimony_. He
  observed that Mercury unites with Antimony much more intimately, by
  melting, than by rubbing them together.

The vitriolic acid, assisted by heat, and even by distillation,
dissolves Regulus of Antimony. The nitrous acid likewise attacks it:
but the solution can by no art be made clear and limpid: so that the
Regulus is only calcined, in a manner, by this acid.

The marine acid dissolves it well enough; but then it must be
exceedingly concentrated, and applied in a peculiar manner, and
especially by distillation. One of the best methods of procuring a
perfect union between the acid of sea-salt and Regulus of Antimony, is
to pulverize the latter, mix it with corrosive sublimate, and distil
the whole. There rises in the operation a white matter, thick, and
scarce fluid, which is no other than the Regulus of Antimony united
and combined with the acid of sea-salt. This compound is extremely
corrosive, and is called _Butter of Antimony_.

It is plain that the corrosive sublimate is here decompounded; that the
Mercury is revivified, and that the acid which was combined therewith
hath quitted it to join the Regulus of Antimony, with which its
affinity is greater. This Butter of Antimony by repeated distillations
acquires a considerable degree of fluidity and limpidness.

If the acid of nitre be mixed with Butter of Antimony, and the whole
distilled, there rises an acid liquor, or a sort of _aqua regis_, which
still retains some of the dissolved Regulus, and is called _Bezoardic
Spirit of Nitre_. After the distillation there remains a white matter,
from which fresh spirit of nitre is again abstracted, and which being
then washed with water is called _Bezoar Mineral_. This Bezoar Mineral
is neither so volatile nor so caustic as Butter of Antimony; because
the nitrous acid hath not the property of volatilizing metallic
substances, as the marine acid does, and because it remains much more
intimately combined with the reguline part.

If Butter of Antimony be mixed with water, the liquor immediately
becomes turbid and milky, and a precipitate falls, which is nothing
but the metallic matter partly separated from its acid, which is too
much weakened by the addition of water to keep it dissolved. Yet this
precipitate still retains a good deal of acid; for which reason it
continues to be a violent emetic, and in some degree corrosive. It hath
therefore been very improperly called _Mercurius Vitæ_.

The proper solvent of Regulus of Antimony is _aqua regis_; by means
whereof a clear and limpid solution of this Semi-metal may be obtained.

Regulus of Antimony mixed with nitre, and projected into a red-hot
crucible, sets the nitre in a flame, and makes it detonate. As it
produces this effect by means of its phlogiston, it must needs at
the same time be calcined, and lose its metallic properties, which
accordingly happens, and when the nitre is in a triple proportion to
the Regulus, the latter is so perfectly calcined as to leave only a
white powder, which is fused with great difficulty, and then turns to a
faintly coloured glass, not very different from common glass, and which
is not reducible to a Regulus by the addition of inflammable matter;
at least it yields but a very small quantity thereof. If less nitre be
used, the calx is not so white; the glass it produces is more like a
metalline glass, and is more easily reduced. The calx of the Regulus
thus prepared by nitre is called, on account of the medicinal virtue
ascribed to it, _Diaphoretic Antimony_, or _Diaphoretic Mineral_.

Nitre always becomes an alkali by deflagration, and in the present
case retains part of the calx, which it even renders soluble in water.
This calx may be separated from the alkali, if an acid be employed to
precipitate it; and then it is called _Materia Perlata_. This pearly
matter is a calx of Antimony, so completely deprived of its phlogiston
as to be altogether incapable of reduction to a Regulus.

Regulus of Antimony readily joins and unites with sulphur, forming
therewith a compound which has a very faint metallic splendour.
This compound appears like a mass of long needles adhering together
laterally; and under this form it is usually found in the ore, or at
least when only separated by fusion from the stones and earthy matters
with which the ore is mixed. It is called _Crude Antimony_.

Antimony flows with a moderate heat, and becomes even more fluid than
other metallic substances. The action of fire dissipates or consumes
the sulphur it contains, and its phlogiston also, so as to convert it
into a calx and a glass, as it does the Regulus.

_Aqua regis_, which we observed to be the proper solvent of the
Regulus, being poured on Antimony, attacks and dissolves the reguline
part, but touches not the sulphur; in consequence whereof it decomposes
the Antimony, and separates its sulphur from its Regulus.

There are several other ways of effecting this decomposition, and
obtaining the reguline part of Antimony by itself: they consist either
in destroying the sulphureous part of the Antimony by combustion, or in
melting the Antimony with some substance which has a greater affinity
than its reguline part with sulphur. Most metals are very fit for this
latter purpose: for though the Regulus has a considerable affinity with
sulphur, yet all the metals, except Gold and Mercury, have a greater.

If therefore Iron, Copper, Lead, Silver, or Tin, be melted with
Antimony, the metal employed will unite with the sulphur, and separate
it from the Regulus.

It must be observed, that, as these metals have some affinity with the
Regulus of Antimony, the Regulus will be joined in the operation by
some of the metal employed as a _Precipitant_, (so those substances
are called which serve as the means of separating two bodies from each
other); and therefore the Regulus procured in this manner will not be
absolutely pure: on this account care is taken to distinguish each by
adding the name of the metal employed in its precipitation; and thence
come these titles, _Martial Regulus of Antimony_, or only _Martial
Regulus_, _Regulus Veneris_; and so of the rest.

Antimony is employed with advantage to separate Gold from all the
other metals with which it may be alloyed. It has been shewn, that all
the metals have a greater affinity than the reguline part of Antimony
with sulphur, Gold only excepted; which is incapable of contracting
any union therewith: and therefore, if a mass compounded of Gold and
several other metals be melted with Antimony, every thing in that
mass which is not Gold will unite with the sulphur of the Antimony.
This union occasions two separations, to wit, that of the sulphur
of the Antimony from its reguline part, and that of the Gold from
the metals with which it was adulterated; and from the whole two new
compounds arise; namely, a combination of the metals with the sulphur,
which being lightest rises to the surface in fusion; and a metalline
mass, formed of the Gold and the reguline part of the Antimony united
together, which being much the heaviest sinks to the bottom. There is
no difficulty in parting the Gold from the Regulus of Antimony with
which it is alloyed: for the metalline mass needs only be exposed to a
degree of fire capable of dissipating into vapours all the Semi-metal
it contains; which being very volatile, the operation is much easier,
and more expeditiously finished, than if the metals with which the Gold
was debased were to be vitrified on the cupel; without taking into the
account, that, if Silver were one of them, recourse must needs be had
to the process of quartation after that of the cupel.

If equal parts of nitre and Antimony be mixed together, and the mixture
exposed to the action of fire, a violent detonation ensues; the nitre
deflagrating consumes the sulphur of the Antimony, and even a part of
its phlogiston. After the detonation there remains a greyish matter
which contains fixed nitre, vitriolated tartar, and the reguline part
of the Antimony in some measure deprived of its phlogiston, and half
vitrified by the action of the fire, which is considerably increased by
the deflagration. This matter is called _Liver of Antimony_.

If, instead of equal parts of nitre and Antimony, two parts of the
former be used to one of the latter, then the reguline part loses much
more of its phlogiston, and remains in the form of a yellowish powder.

Again, if three parts of nitre be taken to one of Antimony, the Regulus
is thereby entirely robbed of its phlogiston, and converted to a white
calx, which bears the name of _Diaphoretic Antimony_, or _Diaphoretic
Mineral_. The pearly matter may be precipitated by pouring an acid
on the saline substances which here remain after the detonation, in
the same manner as we shewed above was to be done with regard to the
Regulus.

In the two last operations, where the nitre is in a double or triple
proportion to the Antimony, the reguline part is found after the
detonation to be converted into a calx, and not into a half-vitrified
matter, which we have seen is the effect when equal parts only of nitre
and Antimony are used. The reason of this difference is, that in these
two cases the reguline part, being wholly, or almost wholly, deprived
of its phlogiston, becomes, as was observed, more difficult to fuse,
and consequently cannot begin to vitrify in the same degree of heat
as that which hath not lost so much of its phlogiston. If, instead of
performing the operation with equal parts of nitre and Antimony alone,
a portion of some substance which abounds with phlogiston be added, in
that case the sulphur only of the Antimony will be consumed, and the
Regulus will remain united with its phlogiston and separated from its
sulphur.

The Regulus prepared in this manner is absolutely pure, because no
metalline substance being employed, none can mix with and adulterate
it. It is called _Regulus of Antimony per se_, or only _Regulus of
Antimony_.

It is true indeed that in this operation much of the reguline part
unavoidably loses its phlogiston and is calcined, and consequently
a much smaller quantity of Regulus is obtained than when metalline
precipitants are employed: but this loss is easily repaired, if it be
thought proper, by restoring to the calcined part its lost phlogiston.

Antimony melted with two parts of fixed alkali yields no Regulus,
but is entirely dissolved by the salt, and forms with it a mass of a
reddish yellow colour.

The reason why no precipitate is produced on this occasion is, that the
alkali uniting with the sulphur of the Antimony forms therewith the
combination called Liver of Sulphur, which by its nature is qualified
to keep the reguline part dissolved. This mass formed by the union of
the Antimony with the alkali is soluble in water. If any acid whatever
be dropt into this solution, there falls a precipitate of a reddish
yellow colour; because the acid unites with the alkali, and forces it
to quit the matters with which it was combined. This precipitate is
called _Golden Sulphur of Antimony_.

As in the operation for preparing _Regulus of Antimony per se_, some of
the nitre is, by the inflammable matters added thereto, turned to an
alkali, this alkali seizes on part of the Antimony, and therewith forms
a compound like that just described. Hence it comes, that if the scoria
formed in this process be dissolved in water, and an acid dropped into
the solution, a true golden sulphur of Antimony is thereby separated.

This union of Antimony with an alkali may also be brought about by the
humid way; that is, by making use of an alkali resolved into a liquor,
and boiling the mineral in it. The alkaline liquor, in proportion as
it acts upon the Antimony, gradually becomes reddish and turbid. If
left to settle and cool when well saturated therewith, it gradually
deposites the Antimony it had taken up, which precipitates in the form
of a red powder; and this precipitate is the celebrated remedy known
by the name of _Kermes Mineral_. It is plain that the kermes is nearly
the same thing with the golden sulphur: yet it differs from it in some
respects; and especially in this, that being taken inwardly it operates
much more gently than the golden sulphur, which is a violent emetic.
Nitre fixed by charcoal, and resolved into a liquor, is the only alkali
employed in preparing the kermes.

It was shewn above, that Regulus of Antimony mixed and distilled with
corrosive sublimate decompounds it, disengages the Mercury, and joining
itself to the marine acid forms therewith a new combination, called
Butter of Antimony. If the same operation be performed with crude
Antimony instead of its Regulus, the same effects are produced: but
then the Antimony itself is also decomposed; that is, the reguline
part is separated from the sulphur, which being set free unites with
the Mercury, now also at liberty, and these two together form a true
cinabar, called _Cinabar of Antimony_.


SECTION II.

_Of_ BISMUTH.

Bismuth, known also by the name of Tin-glass, is a semi-metal, having
almost the same appearance as Regulus of Antimony; yet it has a
more dusky cast, inclining somewhat to red, and even presents some
changeable streaks, especially after lying long in the air.

When exposed to the fire it melts long before it is red, and
consequently with less heat than Regulus of Antimony, which does not
flow, as was shewn above, till it begin to be red-hot. It becomes
volatile, like all the other semi-metals, when acted on by a violent
fire: being kept in fusion by a proper degree of heat it loses its
phlogiston with its metallic form, and turns to a powder or a calx; and
that again is converted into glass by the continued action of fire. The
calx and glass of Bismuth may be reduced, like any other metallic calx,
by restoring their phlogiston.

Bismuth mixes with all the metals in fusion, and even facilitates the
fusion of such as do not otherwise flow readily. It whitens them by its
union, and destroys their malleability.

It amalgamates with Mercury, if they be rubbed together with the
addition of water: yet after some time these two metalline substances
desert each other, and the Bismuth appears again in the form of a
powder. Hence it is plain, that the union it contracts with Mercury is
not perfect; and yet it has the singular property of attenuating Lead,
and altering it in such a manner that it afterwards amalgamates with
Mercury much more perfectly, so as even to pass with it through shamoy
leather without any separation. The Bismuth employed in making this
amalgama afterwards separates from it spontaneously, as usual; but the
Lead still continues united with the Mercury, and always retains the
property thus acquired.

The vitriolic acid does not dissolve Bismuth: its proper solvent is the
nitrous acid, which dissolves it with violence, and abundance of fumes.

Bismuth dissolved in the nitrous acid is precipitated not only by
alkalis, but even by the bare addition of water. This precipitate is
extremely white, and known by the name of _Magistery of Bismuth_.

The acid of sea-salt and _aqua regis_ likewise act upon Bismuth, but
with less violence.

This semi-metal does not sensibly deflagrate with nitre; yet it is
quickly deprived of its phlogiston, and turned into a vitrifiable calx,
when exposed with it to the action of fire.

It readily unites with sulphur in fusion, and forms therewith a
compound which appears to consist of needles adhering laterally to each
other.

It may be separated from the sulphur with which is combined, by only
exposing it to the fire, without any additament; for the sulphur is
either consumed or sublimed, and leaves the Bismuth behind.


SECTION III.

_Of_ ZINC.

Zinc to appearance differs but little from Bismuth, and has even been
confounded with it by several authors. Nevertheless, besides that it
has something of a blueish cast, and is harder than Bismuth, it differs
from it essentially in its properties, as will presently be shewn.
These two metallic substances scarce resemble each other in any thing,
but the qualities common to all semi-metals.

Zinc melts the moment it grows red in the fire, and then also begins
to turn to a calx, which, like any other metallic calx, may be reduced
by means of the phlogiston: but if the fire be considerably increased,
it sublimes, flames, and burns like an oily matter; which is a proof
of the great quantity of phlogiston in its composition. At the same
time abundance of flowers rise from it in the form of white flakes,
flying about in the air like very light bodies; and into this form
may the whole substance of the Zinc be converted. Several names have
been given to these flowers, such as Pompholyx, Philosophic Wool.
They are supposed to be no other than the Zinc itself deprived of its
phlogiston; yet no body has hitherto been able to resuscitate them
in the form of Zinc, by restoring their phlogiston according to the
methods used in the reduction of metals. Though they rise in the air
with very great ease while the Zinc is calcining, yet when once formed
they are very fixed; for they withstand the utmost violence of fire,
and are capable of being vitrified, especially if joined with a fixed
alkali. They are soluble in acids.

Zinc unites with all metalline substances, except Bismuth. It has
this singular property, that being mixed with Copper, even in a
considerable quantity, such as a fourth part, it does not greatly
lessen the ductility thereof, and at the same time communicates to it
a very beautiful colour not unlike that of Gold: on which account the
composition is frequently made, and produces what is called _Brass_.
This metal melts much more easily than Copper alone, because of the
Zinc with which it is alloyed. If it be exposed to a great degree of
heat, the Zinc which it contains takes fire, and sublimes in white
flowers, just as when it is pure.

It is to be observed, that Brass is ductile only while it is cold, and
not then, unless the Zinc used in making it was very pure; otherwise
the composition will prove but a _Tombac_ or _Prince's Metal_, having
very little malleability.

Zinc is very volatile, and carries off with it any metallic substance
with which it is fused, making a kind of sublimate thereof. In the
furnaces where they smelt ores containing Zinc, the matter thus
sublimed is called _Cadmia Fornacum_, to distinguish it from the
native _Cadmia_ called also _Calamine_, or _Lapis Calaminaris_; which,
properly speaking, is an ore of Zinc, containing a great deal of that
semi-metal, together with some Iron, and a stony substance. The name of
_Cadmia Fornacum_ is not appropriated solely to the metallic sublimates
procured by means of Zinc, but is given in general to all the metallic
sublimates found in smelting houses.

If a violent and sudden heat be applied to Zinc, it sublimes in its
metalline form; there not being time for it to burn and be resolved
into flowers.

This semi-metal is soluble in all the acids, but especially in spirit
of nitre, which attacks and dissolves it with very great violence.

Zinc has a greater affinity than iron or copper with the vitriolic
acid; and therefore it decompounds the green and blue vitriols,
precipitating those two metals by uniting with the vitriolic acid, with
which it forms a metallic salt, or vitriol, called _White Vitriol_, or
_Vitriol of Zinc_.

Nitre mixed with Zinc, and projected into a red-hot crucible, detonates
with violence, and during the detonation there rises a great quantity
of white flowers, like those which appear when it is calcined by itself.

Sulphur has no power over Zinc. Even liver of sulphur, which dissolves
all other metallic substances, contracts no union with this semi-metal.

Messrs. Hellot and Malouin have bestowed a great deal of pains on this
semi-metal. An account of their experiments is to be found in the
Memoirs of the Academy of Sciences.


SECTION IV.

_Of_ REGULUS OF ARSENIC.

Regulus of Arsenic is the most volatile of all the semi-metals. A very
moderate heat makes it wholly evaporate, and fly off in fumes; on which
account it cannot be brought to fusion, nor can any considerable masses
thereof be obtained. It has a metallic colour, somewhat resembling
Lead; but it soon loses its splendour when exposed to the air.

It unites readily enough with metallic substances, having the same
affinities with them as Regulus of Antimony hath. It makes them
brittle, and unmalleable. It hath also the property of rendering them
volatile, and greatly facilitates their scorification.

It very easily parts with its phlogiston and its metallic form. When
exposed to the fire it rises in a kind of shining crystalline calx,
which, on that account, looks more like a saline matter than a metallic
calx. To this calx or these flowers are given the names of _White
Arsenic_, _Crystalline Arsenic_, and most commonly plain _Arsenic_.

The properties of this substance are very singular, and extremely
different from those of any other metallic calx. Hitherto it hath been
but little examined; and this led me to make some attempts towards
discovering its nature, which may be seen in the Memoirs of the Academy
of Sciences.

Arsenic differs from every other metalline calx, first, in being
volatile; whereas the calces of all other metallic substances, not
excepting those of the most volatile semi-metals, such as Regulus of
Antimony and Zinc, are exceeding fixed; and, secondly, in having a
saline character, which is not found in any other metalline calx.

The saline character of Arsenic appears, first, from its being soluble
in water; secondly, from its corrosive quality, which makes it one
of the most violent poisons: a quality from which the other metallic
substances are free, when they are not combined with some saline
matter. Regulus of Antimony must however be excepted. But then the
best Chymists agree that this semi-metal is either nearly of the same
nature with Arsenic, or contains a portion thereof in its composition:
besides, its noxious qualities never discover themselves so plainly
as when it is combined with some acid. Lastly, Arsenic acts just like
the vitriolic acid upon nitre; that is, it decompounds that neutral
salt, by expelling its acid from its alkaline basis, of which it takes
possession, and therewith forms a new saline compound.

This combination is a species of salt that is perfectly neutral. When
the operation is performed in a close vessel, the salt shoots into
crystals in the form of right-angled quadrangular prisms, terminated at
each extremity by pyramids that are also quadrangular and right angled;
some of which however, instead of ending in a point, are obtuse as if
truncated. The consequence is different when the operation is performed
in an open vessel; for then nothing is obtained but an alkaline salt
impregnated with Arsenic, which cannot be crystallized.

The cause of this different effect is, that, when the Arsenic is once
engaged in the alkaline basis of the nitre, it can never be separated
from it by the utmost force of fire, so long as it is kept in a close
vessel; whereas, if you expose it to the fire without that precaution,
it readily separates from it. This property of arsenic was never before
observed by any Chymist, and therefore this our new species of Neutral
arsenical salt was absolutely unknown till lately.

This new salt possesses many singular properties, the chief of which
are these. First, it cannot be decompounded by the intervention of
any acid, even the strongest acid of vitriol; and this, joined to its
property of expelling the nitrous acid from its basis, shews that it
has a very great affinity with fixed alkalis.

Secondly, this very salt, on which pure acids have no effect, is
decompounded with the greatest ease by acids united with metallic
substances. The reason of this phenomenon is curious, and furnishes us
with an instance of what we advanced concerning double affinities.

If to a resolution of any metallic substance whatever, made by any acid
whatever, (except that of Mercury by the marine acid, and that of Gold
by _aqua regis_), a certain quantity of our New Salt dissolved in water
be added, the metallic substance is instantaneously separated from the
acid in which it was dissolved, and falls to the bottom of the liquor.

All metallic precipitates obtained in this manner are found to be a
combination of the metal with Arsenic; whence it necessarily follows
that the new Neutral Salt is by this means decompounded, its arsenical
part uniting with the metallic substance, and its alkaline basis with
the acid in which that substance was dissolved.

The affinities of these several bodies must be considered as operating
on this occasion in the following manner: The acids which tend to
decompound the Neutral Salt of Arsenic, by virtue of their affinity
with its alkaline basis, are not able to accomplish it, because this
affinity is powerfully counteracted by that which the Arsenic has with
the same alkaline basis, and which is equal or even superior to theirs.
But if these acids happen to be united with a substance which naturally
has a very great affinity with the arsenical part of the Neutral Salt,
then, the two parts of which this Salt consists being drawn different
ways by two several affinities tending to separate them from each
other, the Salt will undergo a decomposition, which could not have been
effected without the help of this second affinity. Now, as metallic
substances have a great affinity with Arsenic, it is not surprising
that the Neutral Salt of Arsenic, which cannot be decompounded by a
pure acid, should nevertheless yield to an acid combined with a metal.
The decomposition of this Salt, therefore, and the precipitation which
of course it produces in metallic solutions, are brought about by the
means of a double affinity; namely, that of the acid with the alkaline
basis of the Neutral Salt, and that of the metal with the arsenical
part of that salt.

Arsenic has not the same effect on sea-salt as on nitre, and cannot
expel its acid: a very singular phenomenon, for which it is hard to
assign a reason; for the nitrous acid is known to have a greater
affinity than the marine acid with alkalis, and even with the basis of
sea-salt itself.

Yet Arsenic may be combined with the basis of sea-salt, and a Neutral
Salt thereby obtained, like that which results from the decomposition
of nitre by Arsenic: but for that purpose a quadrangular nitre must be
first prepared, and Arsenic applied thereto as to common nitre.

The Salt produced by uniting Arsenic with the basis of sea-salt very
much resembles the Neutral Salt of Arsenic above treated of as well in
the figure of its crystals as in its several properties.

Arsenic presents another singular phenomenon, both with the alkali of
nitre and with that of sea-salt; which is, that if it be combined with
these salts in a fluid state, it forms with them a saline compound,
quite different from the Neutral Salts of Arsenic which result from the
decomposition of nitrous salts.

This saline compound, which I call _Liver of Arsenic_, takes up a
much greater quantity of Arsenic than is necessary for the perfect
saturation of the alkali. It has the appearance of a glue, which
is so much the thicker the more Arsenic it contains. Its smell is
disagreeable; it attracts the moisture of the air, and does not
crystallize; it is easily decompounded by any acid whatever, which
precipitates the Arsenic and unites with the alkali. Lastly, the
effects it produces on metallic solutions are different from those of
our neutral arsenical salts. But the bounds which I have set myself
in this treatise will not allow me to be more particular. Such as
have the curiosity to inquire further into the subject may consult my
Dissertations on Arsenic, published among the Memoirs of the Academy of
Sciences.

Arsenic is easily reduced to a Regulus. It need only be mixed with any
matter containing the phlogiston, and by the help of a moderate heat a
true Regulus will sublime. This Regulus, as was said, is very volatile,
and calcines with the greatest ease; which is the reason why it cannot
be obtained but in small quantities, and also why, in order to obtain
masses of it, some have thought of adding thereto some metal with which
it has a great affinity, such as Copper or Iron; because, by joining
with the metal, it is partly fixed and restrained from flying off. But
it is plain the Regulus obtained by this means is not pure, as it must
partake considerably of the metal employed.

Arsenic readily unites with sulphur, and rises with it in a yellow
compound, called _Orpiment_.

Sulphur cannot be separated from Arsenic but by the intervention of two
bodies only; to wit, a fixed alkali and Mercury.

The property which Mercury possesses of separating sulphur from Arsenic
is founded on this, that these two metallic substances are incapable
of contracting any union; whereas, though most of the other metals and
semi-metals have a greater affinity with sulphur than Mercury hath, as
was shewn in treating of the decomposition of Cinabar, nevertheless
they are all unable to decompound Orpiment; because some of them have
as great an affinity with Arsenic as with sulphur; others have no
affinity with either; and lastly, sulphur hath as great an affinity
with Arsenic as with any of them.

It must be observed that, if fixed alkalis be employed to purify
Arsenic in this manner, no more must be used than is necessary to
absorb the sulphur or the phlogiston, of which also it is their nature
to deprive Arsenic; for otherwise, as it has been shewn that Arsenic
readily unites with alkalis, they would absorb a considerable quantity
thereof.



CHAP. X.

_Of_ OIL _in general_.


Oil is an unctuous body, which burns and consumes with flame and smoke,
and is not soluble in water. It consists of the phlogiston united with
water by means of an acid. There is, moreover, in its composition a
certain proportion of earth, more or less, according to each several
sort of Oil.

The inflammability of Oil evidently proves that it contains the
phlogiston. That an acid is one of its constituent principles many
experiments demonstrate, of which these are the chief: If certain Oils
be long triturated with an alkaline salt, and the alkali afterwards
dissolved in water, crystals of a true neutral salt will be produced:
some metals, and particularly Copper, are corroded and rusted by Oils,
just as they are by acids: again, acid crystals are found in some Oils
that have been long kept. This acid in Oil serves undoubtedly to unite
its phlogiston with its water; because these two substances having no
affinity with each other cannot be united without the intervention of
such a medium as an acid, which has an affinity with both. As to the
existence of water in Oils, it appears plainly when they are decomposed
by repeated distillations, especially after mixing them with absorbent
earths. Lastly, when an Oil is destroyed by burning, a certain quantity
of earth is constantly left behind.

We are very sure that the above-mentioned principles enter into the
composition of Oils; for they may be obtained from every one of them:
but it is not absolutely certain that they consist of these only, and
that they do not contain some other principle which may escape our
notice in decomposing them; for hitherto it doth not appear, by any
experiment we can depend on, that Oil was ever produced by combining
together the principles here specified: yet such redintegrations are
the only means we have of satisfying ourselves that we know all the
principles which constitute a body.

Oils exposed to the fire in close vessels pass over almost wholly from
the containing vessel into any other applied to receive them. There
remains, however, a small quantity of black matter, which is extremely
fixed, and continues unalterable as long as it hath no communication
with the external air, be the force of the fire ever so violent. This
matter is no other than part of the phlogiston of the Oil united
with its most fixed and grossest earth; and this is what we called
_Charcoal_, or plainly a _Coal_.


SECTION I.

_Of_ CHARCOAL.

When Oil happens to be united to much earth, as it is in vegetable and
animal bodies, it leaves a considerable quantity of _Coal_ or charred
matter.

This Coal, exposed to the fire in the open air, burns and wastes,
but without blazing like other combustible matters: there appears
only a small blueish flame, but not the least smoke. Most commonly
it only glows and sparkles, and so gradually falls into ashes, which
are nothing but the earth of the body, combined with an alkaline salt
in burning. This alkaline salt may be separated from the earth, by
lixiviating the ashes with water, which dissolves all the salt, and
leaves the earth quite pure.

Charcoal is unalterable and indestructible by any other body but fire;
whence it follows, that when it is not actually kindled and ignited,
the most powerful agents, such as the acids, though ever so strong and
concentrated, have not the least effect on it.

The case is otherwise when it is lighted, that is, when its phlogiston
begins to separate from its earth; for then the pure acid of vitriol
being joined therewith, contracts an instantaneous union with its
phlogiston, and evaporates in a volatile sulphureous spirit. If the
vitriolic acid, instead of being applied quite pure, be first clogged
with some basis, especially an alkaline one, it quits that basis,
enters into a more intimate union with the phlogiston of the burning
Coal, and so forms an actual sulphur, with which the alkali now unites
and forms a hepar.

The pure acid of sea-salt hath not been observed to act in the least
upon Charcoal, especially when it is not on fire. But when this acid
is incorporated with an alkaline or metallic basis, and combined
according to a peculiar process with burning Charcoal, it in like
manner quits its basis, unites with the phlogiston, and therewith forms
a phosphorus, of which we have already taken notice.

Nor has the pure nitrous acid any effect on a charred Coal, even when
ignited: and so far is it from being able to kindle a cold one, that
when poured on a live one, it extinguishes it like water. But when
this acid is united with a basis, it quits it rapidly as soon as it
touches a burning coal, and rushes violently into an union with the
phlogiston thereof. From this union there probably arises, as we said
before, a kind of sulphur or phosphorus, which is so inflammable as to
be destroyed by the fire the very moment it is generated.

The acids of nitre and vitriol act upon Oils; but very differently,
according to the quantity of phlegm they contain. If they be weakened
with much water, they have no effect at all upon Oils; if they contain
little water, or be dephlegmated to a certain degree, they dissolve
them with heat, and with them form compounds of a thick consistence.
Acids, thus combined in a considerable proportion with Oils, render
them soluble in water.


SECTION II.

_Of_ SOAP.

Alkalis also have the same property. When an Oil is combined with an
acid or an alkali in such a manner, that the compound resulting from
their union is soluble in water; such a compound may in general be
called a _Soap_. Soap itself hath the property of rendering fat bodies
in some measure soluble in water; on which account it is very useful
for scouring or cleansing any thing greasy.

Oily and saline substances, combined together, observe the same general
rules as all other combinations; that is, they mutually communicate
the properties belonging to each: thus Oils, which naturally are not
soluble in water, acquire, by their union with saline matters, the
property of dissolving therein; and salts lose, by their conjunction
with Oils, part of their natural tendency to incorporate with water;
so that, while they serve to constitute soap, they do not, as before,
attract the moisture of the air, _&c._ and, in like manner, as they are
not inflammable, they considerably lessen the inflammability of the
Oils combined with them.

Acid Soaps are decompounded by alkalis, as alkaline Soaps are by acids,
according to the general rules of affinities.

The acids of nitre and vitriol, when highly concentrated, dissolve
Oils with such violence as to heat them, make them black, burn them,
and even set them on fire. How sea-salt affects Oils is not yet
sufficiently ascertained.

All Oils have the property of dissolving sulphur; which is not at all
surprising, seeing each of its component principles hath an affinity
with Oil.

It is also a property common to all Oils to become more fluid, subtile,
light, and limpid, the oftener they are distilled. On the contrary,
by being incorporated with saline substances they acquire a greater
consistence, and sometimes form compounds that are most solid.



CHAP. XI.

_Of the several Sorts of_ OILS.


Oils are distinguished by the substances from which they are drawn: and
as Oils are extracted from minerals, from vegetables, and from animals,
there are of course Mineral, Vegetable, and Animal Oils.


SECTION I.

_Of_ MINERAL OILS.

In the bowels of the earth we find but one sort of Oil, called
_Petroleum_: its smell is strong and not disagreeable, and its colour
sometimes more sometimes less yellow. There are certain mineral
substances which yield by distillation a great deal of Oil very like
Petroleum. This sort of substance is called a _Bitumen_, and is,
indeed, nothing but an Oil rendered consistent and solid by being
combined with an acid; as appears from hence, that by uniting Petroleum
with the acid of vitriol we can produce an artificial Bitumen very like
the native.


SECTION II.

_Of_ VEGETABLE OILS.

Vegetable substances yield a very great quantity and variety of oils:
for there is not a plant, or part of a plant, that does not contain one
or more sorts thereof, generally peculiar to itself, and different from
all others.

By expression only, that is, by bruising and squeezing vegetable
substances, particularly certain fruits and seeds, a sort of oil is
obtained which has scarce any smell or taste. Oils of this sort are
very mild and unctuous; and, because in this respect they resemble
animal fat more than the rest do, they are called _Fat Oils_.

These Oils, being exposed to the air for some time, sooner or latter
grow thick, acquire an acrid taste, and a strong disagreeable smell.
Some of them congeal with the smallest degree of cold. This sort of
Oil is well adapted to dissolve those preparations of Lead called
Litharge and Minium, with which they form a thick tenacious substance,
that is used for the basis of almost all plasters. They also dissolve
Lead in its metalline form; but not so easily as the sorts of calx
above-mentioned; probably because its body is not so much opened, nor
its parts so divided.

By expression alone we also procure from certain vegetable substances
another sort of Oil, which is thin, limpid, volatile, of a pungent
taste, and retains the smell of the vegetable that yielded it; on which
account it is called an _Essential Oil_. Of this there are several
sorts, differing from one another, like the Fat Oils, according to the
subjects from which they are obtained.

We must observe, that it is very difficult, or rather in most
cases impossible, to force from the greatest part of vegetables,
by expression only, all the essential Oil they contain. For this
purpose therefore recourse must be had to fire: a gentle heat, not
exceeding that of boiling water, will extract all the essential Oils
of vegetables; and this is the most usual and most convenient way of
procuring them.

The fat Oils cannot be obtained by the same method: these being much
less volatile than the essential Oils, require a much greater degree of
heat to raise them; which nevertheless they cannot bear without being
much spoiled and entirely changed in their nature, as shall presently
be shewn. All Oils, therefore, which rise with the heat of boiling
water, and such alone, should be called Essential Oils.

Essential Oils, in a longer or shorter time, according to the nature
of each, lose the fragrant smell they had when newly distilled, and
acquire another, which is strong, rancid, and much less agreeable: they
also lose their tenuity, becoming thick and viscid; and in this state
they greatly resemble those substances abounding in Oil which flow from
certain trees, and which are called _Balsams_ or _Resins_, according as
they are less or more consistent.

Balsams and Resins are not soluble in water. But there are other Oily
compounds which likewise run from trees; and, though not unlike Resins,
are however soluble in water. These are called _Gums_; and their
property of dissolving in water arises from their containing more water
and more salt than Resins have; or at least their saline parts are less
clogged and more disengaged.

Balsams and Resins distilled with the heat of boiling water yield
great quantities of a limpid, subtile, odoriferous, and, in one word,
essential Oil. In the still there remains a substance thicker and more
consistent than the Balsam or Resin was before distillation. The same
thing happens to essential Oils which by length of time have acquired
a consistence and are grown resinous. If they be re-distilled, they
recover their former tenuity, leaving behind them a remainder thicker
and more resinous than they themselves were. This second distillation
is called the _Rectification_ of an Oil.

It must be observed, that an essential Oil, combined with an acid
strong enough to dissolve it, immediately becomes as thick and
resinous, in consequence of this union, as if it had been long exposed
to the air: which proves the consistence an Oil acquires by long
keeping to be owing to this, that its lightest and less acid parts
being evaporated, the proportion of its acid to the remainder is so
increased, that it produces therein the same change, as an additional
acid mixed with the Oil would have wrought before the evaporation.

This also shews us, that Balsams and Resins are only essential Oils
combined with a great proportion of acid, and thereby thickened.

If vegetable substances, from which no more essential Oil can be drawn
by the heat of boiling water, be exposed to a stronger heat, they yield
an additional quantity of Oil; but it is thicker and heavier than the
essential Oil. These Oils are black, and have a very disagreeable burnt
smell, which hath made them be called _Fetid_ or _Empyreumatic_ Oils.
They are moreover very acrid.

It must be observed, that, if a vegetable substance be exposed to a
degree of heat greater than that of boiling water, before the fat or
the essential Oil is extracted from it, an empyreumatic Oil only will
then be obtained; because both the fat and essential Oils, when exposed
to the force of fire, are thereby burnt, rendered acrid, acquire a
smell of the fire, and, in a word, become truly empyreumatic. There
is ground to think, that an empyreumatic Oil is nothing else but an
essential or fat Oil burnt and spoiled by the fire, and that no other
Oil besides these two exists naturally in vegetables.

Empyreumatic Oils, distilled and rectified several times by a gentle
heat, acquire by every distillation a greater degree of tenuity,
lightness, and limpidity. By this means also they lose something of
their disagreeable odour; so that they gradually come nearer and
nearer to the nature of essential Oils: and if the rectifications be
often enough repeated, ten or twelve times for instance, they become
perfectly like those Oils; except that their smell will never be
so agreeable, nor like that of the substances from which they were
obtained.

Fat Oils may also be brought by the same means to resemble essential
Oils: but neither essential nor empyreumatic Oils are capable of
acquiring the properties of fat Oils.


SECTION III.

_Of_ ANIMAL OILS.

Distillation procures us considerable quantities of Oil from all
the parts of animal bodies, and especially from their fat. This Oil
at first is not very fluid, and is extremely fetid: but by many
rectifications it gradually acquires a great degree of clearness
and tenuity, and at the same time loses much of its disagreeable
odour. Animal Oils, thus rendered thin and fluid by a great number of
rectifications, have the reputation of being an excellent medicine, and
a specific in the epilepsy.



CHAP. XII.

_Of_ FERMENTATION _in general_.


By Fermentation is meant an intestine motion, which, arising
spontaneously among the insensible parts of a body, produces a new
disposition and a different combination of those parts.

To excite a Fermentation in a mixt body, it is necessary, first, that
there be in the composition of that mixt a certain proportion of
watery, saline, oily, and earthy parts: but this proportion is not
yet sufficiently ascertained. Secondly, it is requisite that the body
to be fermented be placed in a certain degree of temperate heat: for
much cold obstructs fermentation; and too much heat decomposes bodies.
Lastly, the concurrence of the air is also necessary to fermentation.

All vegetable and animal substances are susceptible of Fermentation,
because all of them contain in a due proportion the principles above
specified. However, many of them want the proper quantity of water, and
cannot ferment while they remain in such a state of dryness. But it is
easy to supply that defect, and so render them very apt to ferment.

With respect to minerals properly so called, (that is, excluding such
vegetable and animal substances as may have lain long buried in the
earth), they are not subject to any Fermentation; at least, that our
senses can perceive.

There are three sorts of Fermentation, distinguished from one another
by their several productions. The first produces wines and spirituous
liquors; for which reason it is called the _Vinous_ or _Spirituous
Fermentation_: the result of the second is an acid liquor; and
therefore it is called the _Acetous Fermentation_: and the third
generates an alkaline salt; which, however, differs from the alkaline
salts hitherto treated of, in this respect chiefly, that, instead of
being fixed, it is extremely volatile: this last sort takes the name
of the _Putrid_ or _Putrefactive Fermentation_. We shall now consider
these three sorts of Fermentation and their effects a little more
particularly.

These three sorts of Fermentation may take place successively in the
same subject; which proves them to be only three different degrees of
fermentation, all proceeding from one and the same cause, rather than
three distinct fermentations. These degrees of fermentation always
follow the order in which we have here placed them.



CHAP. XIII.

_Of the_ SPIRITUOUS FERMENTATION.


The juices of almost all fruits, all saccharine vegetable matters,
all farinaceous seeds and grains of every kind, being diluted with
a sufficient quantity of water, are proper subjects of Spirituous
Fermentation. If such liquors be exposed, in vessels slightly stopped,
to a moderate degree of heat, they begin in some time to grow turbid;
there arises insensibly a small commotion among their parts, attended
with a hissing noise; this by little and little increases, till the
grosser parts appear, like little seeds or grains, moving to and
fro, agitated among themselves, and thrown up to the surface. At the
same time some air bubbles rise, and the liquor acquires a pungent,
penetrating smell, occasioned by the very subtile vapours which exhale
from it.

These vapours have never yet been collected, in order to examine their
nature; and they are known only by their noxious effects. They are so
actively pernicious, that if a man comes rashly into a close place,
where large quantities of liquors are fermenting, he suddenly drops
down and expires, as if he were knocked on the head.

When these several phenomena, begin to go off, it is proper to stop
the fermentation, if a very spirituous liquor be required: for if it
be suffered to continue longer, the liquor will become acid, and from
thence proceed to its last stage, that is, to putrefaction. This is
done by stopping the containing vessels very close, and removing them
into a cooler place. Then the impurities precipitate, and settling at
the bottom leave the liquor clear and transparent: and now the palate
discovers that the sweet saccharine taste it had before fermentation is
changed to an agreeable pungency, which is not acid.

Liquors thus fermented are in general called _Wines_: for though in
common life that word properly signifies the fermented juice of grapes
only, and particular names are given to the fermented juices of other
vegetable substances; as that obtained from Apples is called _Cyder_;
that made from malt is called _Beer_: yet in Chymistry it is of use to
have one general term denoting every liquor that has undergone this
first degree of fermentation.

By distillation we draw from Wine an inflammable liquor, of a yellowish
white colour, light, and of a penetrating, pleasant smell. This
liquor is the truly spirituous part of the wine, and the product
of fermentation. That which comes off in the first distillation is
commonly loaded with much phlegm and some oily parts, from which it may
be afterwards freed. In this state it goes by the name of _Brandy_; but
when freed from these heterogeneous matters by repeated distillations,
it becomes still clearer, lighter, more fragrant, and much more
inflammable, and then is called _Spirit of Wine_, and _Rectified
Spirit of Wine_, or an _Ardent Spirit_, if considerably purified. The
properties which distinguish an Ardent Spirit from all other substances
are its being inflammable; its burning and consuming entirely, without
the least appearance of smoke or fuliginosity; its containing no
particles reducible to a coal; and its being perfectly miscible with
water. Ardent Spirits are lighter and more volatile than any of the
principles of the mixts from which they were produced, and consequently
more so than the phlegm, the acid, and the oil of which they themselves
consist. This arises from a particular disposition of these principles,
which are in a singular manner attenuated by fermentation, and thereby
rendered more susceptible of expansion and rarefaction.

Ardent spirits are supposed to be the natural solvents of oils and oily
matters. But it is very remarkable that they dissolve essential oils
only, without touching the fat of animals, or the fat oils obtained
from vegetables by expression; yet when these oils have once undergone
the action of fire, they become soluble in spirit of wine, and even
acquire a new degree of solubility every time they are distilled. It is
not so with essential oils, which can never be rendered more soluble in
ardent spirits than they are at first; and are so far from acquiring
a new degree of solubility every time they are distilled, that on the
contrary they even in some measure lose that property by repeated
rectifications.

I have taken some pains to find out the causes of these singular
effects, and the result of my inquiries is published among the Memoirs
of the Academy of Sciences for the year 1745. I therein consider ardent
spirits as consisting of an oil, or at least a phlogiston, mixed with a
portion of water, in which it is rendered soluble by means of an acid.
This being laid down, I shew that the inability of spirit of wine to
dissolve some oils must be imputed to its aqueous part, in which oils
are not naturally soluble without the intervention of a salt: and that
the power which this spirit exerts in dissolving other oils with ease,
such as essential oils, must in all probability be owing to this, that
in these oils it meets with the necessary saline medium, that is, with
an acid, which numberless experiments shew they actually contain.

On the other hand, I there prove, that the acid in essential oils is
super-abundant, and in some sort foreign to their nature, or that it
is but slightly connected with them, and in part deserts them every
time they are distilled; which renders them less soluble after every
new rectification: whereas, on the contrary, the fat expressed oils in
their natural state give not the least sign of acidity, but the action
of fire upon them discovers an acid which was not perceivable before.
Hence I conjecture, that these oils contain no more acid than is just
necessary to constitute them oils; that this acid is intimately blended
with their other component parts; that it is so sheathed and entangled
by these parts as to be incapable of exerting any of its properties;
and that on this account these oils in their natural state are not
soluble in spirit of wine: but that the disposition of their parts
being gradually changed by the fire, and their acid, being by that
means set more and more at liberty, at length recovers its properties,
and particularly that of rendering the oily parts soluble in an aqueous
menstruum: and hence it follows, that the fat oils become so much the
more soluble in spirit of wine the oftener they are exposed to the
action of fire.

Spirit of wine doth not dissolve fixed alkalis; or at least it takes
up but a very small quantity thereof; and hence ardent spirits may be
freed from much of their phlegm by means of these salts thoroughly
dried: for as they strongly imbibe moisture, and have even a greater
affinity than ardent spirits with water, if a fixed alkali, well
exsiccated, be mixed with spirit of wine that is not perfectly
dephlegmated, the alkali immediately attracts its superfluous moisture,
and is thereby resolved into a liquor, which, on account of its
gravity, descends to the bottom of the vessel. The spirit of wine,
which swims at top, is by this means as much dephlegmated, and as dry,
as if it had been rectified by several distillations. As it takes up
some alkaline particles in this operation, it is thereby qualified to
dissolve oily matters with the greater facility. When rectified in
this manner, it is called _Alcoholized Spirit of Wine_.

Yet spirit of wine, even when rectified to an alcohol, is not capable
of dissolving all oily matters. Those named Gums will by no means
enter into any sort of union therewith; but it readily dissolves most
of those which are known by the appellation of Resins. When it has
dissolved a certain proportion of resinous particles it acquires a
greater consistence, and forms what is called a _Spirit Varnish_, or a
_Drying Varnish_, because it soon dries. This Varnish is subject to be
damaged by water. Many sorts thereof are prepared, differing from each
other according to the different resins employed, or the proportions
in which they are used. Most of these Varnishes are transparent and
colourless.

Such bitumens or resins, as spirit of wine will not touch, are
dissolved in oils by means of fire, and then form another kind of
Varnish, which water does not hurt. These Varnishes are usually
coloured, and require much longer time to dry than the Spirit
Varnishes: they are called _Oil Varnishes_.

Spirit of wine hath a much greater affinity with water than with oily
matters: and therefore if a solution of any oil or resin in spirit of
wine be mixed with water, the liquor immediately grows turbid, and
acquires a whitish milky colour, owing entirely to the oily parts being
separated from the spirituous menstruum by the accession of water, and
too finely divided to appear in their natural form. But if the liquor
stand some time quiet, several of these particles unite together, and
gradually acquire a bulk sufficient to render them very perceptible to
the eye.

Acids have an affinity with spirit of wine, and may be combined with
it. By this union they lose most of their acidity, and on that account
are said to be _Dulcified_. But as these combinations of acids,
especially of the vitriolic acid, with spirit of wine furnish some new
productions of very singular properties, and as an examination thereof
may throw much light on the nature of ardent spirits, it will not be
amiss to take notice of them in this place, and consider each of them
particularly.

One part of highly concentrated oil of vitriol being mixed with four
parts of well dephlegmated spirit of wine, there arises immediately a
considerable ebullition and effervescence, attended with great heat,
and abundance of vapours, which smell pleasantly, but are hurtful to
the lungs. At the same time is heard a hissing like that produced by
a piece of red-hot iron plunged into water. Indeed it is proper to
mix the liquors very gradually; for otherwise the vessels in which the
operation is performed will be in great danger of breaking.

If the two liquors thus mixed be distilled with a very gentle heat,
there rises first a spirit of wine of a most penetrating and grateful
odour: when about half thereof is come over, what follows has a quicker
and more sulphureous smell, and is also more loaded with phlegm. When
the liquor begins to boil a little, there comes off a phlegm which
smells very strong of sulphur, and grows gradually more acid. On this
phlegm floats a small quantity of a very light and very limpid oil. In
the still there remains a thick blackish substance, somewhat like a
resin or bitumen. From this substance may be separated a good deal of a
vitriolic but sulphureous acid. When that is extracted, there remains
a black mass like a charred coal, which being put into a crucible, and
exposed to a violent heat, leaves a small portion of earth, very fixed,
and even vitrifiable.

By rectifying the ardent spirit, which came over in distilling the
above-mentioned mixture, a very singular liquor is obtained, which
differs essentially both from oils and from ardent spirits, though
in certain respects it resembles them both. This liquor is known in
Chymistry by the name of _Æther_, and its chief properties are as
follow.

Æther is lighter, more volatile, and more inflammable, than the most
highly rectified spirit of wine. It quickly flies off when exposed
to the air, and suddenly catches fire when any flame approaches it.
It burns like spirit of wine without the least smoke, and consumes
entirely without leaving the smallest appearance of a coal or of ashes.
It dissolves oils and oily matters with great ease and rapidity. These
properties it has in common with an ardent spirit. But it resembles
an oil in that it is not miscible with water; and this makes it
essentially different from spirit of wine, the nature of which is to be
miscible with all aqueous liquors.

Another very singular property of Æther is its great affinity with
gold, exceeding even that of _aqua regis_. It does not indeed dissolve
gold when in a mass, and in its metalline form; but if a small quantity
of Æther be added to a solution of gold in _aqua regis_, and the whole
shaken together, the gold separates from the _aqua regis_, joins the
Æther, and remains dissolved therein.

The reason of all the phenomena above-mentioned, resulting from the
mixture of spirit of wine with oil of vitriol, is founded on the great
affinity between this acid and water. For if the vitriolic acid be
weak, and as it were over-dosed with watery parts, neither oil nor
Æther can be obtained by means thereof: but when highly concentrated,
it attracts the aqueous parts very powerfully; and therefore, being
mixed with spirit of wine, lays hold of most of the water contained
in it, and even robs it of some portion of that which is essential to
its nature, and necessary to constitute it spirit of wine: whence it
comes to pass, that a certain quantity of the oily particles in its
composition being separated from the watery particles, and so brought
nearer to each other, they unite and assume their natural form; and
thus the oil that swims at top of the sulphureous phlegm is produced.

The vitriolic acid moreover thickens and even burns some of this oil;
and hence comes the bituminous residuum left at the bottom of the
still, which looks like the result of a vitriolic acid combined with
common oil. Lastly, the vitriolic acid becomes sulphureous, as it
always doth when united with oily matters, and also very aqueous, on
account of the quantity of phlegm which it attracts from the spirit of
wine.

Æther may be considered as a spirit of wine exceedingly dephlegmated,
even to such a degree that its nature is thereby changed; so that the
few aqueous particles left in it are not sufficient to dissolve the
oily particles and keep them asunder; which therefore being now much
nearer to one another than in common spirit of wine, the liquor hath
lost its property of being miscible with water.

Spirit of nitre well dephlegmated, and combined with spirit of wine,
presents likewise some very singular appearances.

First, in the very instant of its mixture with spirit of wine, it
produces a greater and more violent effervescence than the vitriolic
acid occasions.

Secondly, this mixture, without the help of distillation, and only by
stopping the bottle in which the liquors are contained, affords a sort
of Æther, produced probably by the vapours which ascend from, and swim
at top of the mixture. This is a very singular liquor. Dr. Navier was
the first that took notice of it, and gave a description thereof, which
may be seen in the Memoirs of the Academy of Sciences.

Thirdly, some authors pretend that, by distilling the mixture under
consideration, an oil is obtained greatly resembling that which, as we
observed above, rises from spirit of wine combined with the vitriolic
acid: others again deny this. For my part, I believe the thing depends
on the different concentration of the spirit of nitre, as well as on
the quality of the spirit of wine, which is sometimes more sometimes
less oily.

Fourthly, the two liquors we are speaking of, being intimately mixed by
distillation, form a liquor slightly acid, used in medicine, and known
by the name of _Sweet_ or _Dulcified Spirit of Nitre_: a very proper
name, seeing the nitrous acid, by uniting with the spirit of wine,
actually loses almost all its acidity and corrosive quality.

Fifthly and lastly, when the distillation is finished, there remains in
the bottom of the vessel a thick blackish substance, nearly resembling
that which is found after distilling oil of vitriol and spirit of wine.

Spirit of salt hath likewise been combined with spirit of wine; but it
does not unite therewith so easily or so intimately as the two acids
above-mentioned. To mix them thoroughly, the spirit of salt must be
highly concentrated, and smoking, and moreover the assistance of the
still must be called in. Some authors pretend that from this mixture
also a small quantity of oil may be obtained; which probably happens
when the liquors have the qualities above-specified. The marine acid
likewise, by uniting with spirit of wine, loses most of its acidity; on
which account it is in like manner called _Sweet_ or _Dulcified Spirit
of Salt_. A thick residuum is also found here after distillation.



CHAP. XIV.

_Of the_ ACETOUS FERMENTATION.


Besides an ardent spirit, wine affords a great deal of water, oil,
earth, and a sort of acid which shall be considered presently. When
the spirituous part is separated from these other matters, they
undergo no further change. But if all the constituent parts of wine
remain combined together, then, after some time, shorter or longer as
the degree of heat in which the wine stands is greater or less, the
fermentation begins afresh, or rather arrives at its second stage. The
liquor once more grows turbid, a new intestine motion arises, and,
after some days, it is found changed into an acid; which, however,
is very different from those hitherto treated of. The liquor then
takes the name of _Vinegar_. The acetous fermentation differs from
the spirituous, not only in its effect, but also in several of its
concomitant circumstances. Moderate motion is of service to this,
whereas it obstructs the spirituous; and it is attended with much more
warmth than the spirituous. The vapours it produces are not noxious,
like those of fermenting wine. Lastly, Vinegar deposites no tartar,
even when the wine employed in this operation is quite new, and hath
not had time to discharge its tartar: instead of tartar, Vinegar
deposites a viscid matter which is very apt to putrify.

It must be observed, that wine is not the only substance that is
susceptible of the acetous fermentation: for several vegetable and even
animal matters, which are not subject to the spirituous fermentation,
turn sour before they putrify. But as vinous liquors possess in a
very eminent degree the property of being susceptible of the acetous
fermentation, and likewise of producing the strongest acids that can
result from such fermentation, their acid shall be more particularly
considered in this place.


SECTION I.

_Of_ VINEGAR.

If wine, which has gone through this second stage of fermentation,
be distilled, instead of an ardent spirit, only an acid liquor is
obtained, which is called _Distilled Vinegar_.

This acid has the same properties as the mineral acids of which we have
already treated; that is, it unites with alkaline salts, absorbent
earths, and metallic substances, and therewith forms neutral saline
combinations.

Its affinity with these substances observes the same order as that
observed by the mineral acids with regard to the same substances;
but in general it is weaker; that is, any mineral acid is capable of
expelling the acid of Vinegar out of all matters with which it is
united.

Vinegar hath likewise a greater affinity than sulphur with alkalis:
whence it follows, that it is capable of decompounding that combination
of sulphur with an alkali called Liver of Sulphur, and of precipitating
the sulphur it contains.

The acid of Vinegar is always clogged with a certain proportion of
oily parts, which greatly weaken it, and deprive it of much of its
activity; and for this reason it is not near so strong as the mineral
acids, which are not entangled with any oil. By distillation, indeed,
it may be freed from this oil, and at the same time from the great
quantity of water which in a manner suffocates it, and by that means
may be brought much nearer to the nature of the mineral acids: but this
attempt hath not yet been prosecuted with the assiduity it deserves.
Besides distillation, there is another way of freeing Vinegar from a
good deal of its phlegm; and that is, by exposing it to a hard frost,
which readily congeals the watery part into ice, while the acid retains
its fluidity.

Vinegar, saturated with a fixed alkali, forms a neutral oily salt, of
a dark colour, which is semi-volatile, melts with a very gentle heat,
flames when thrown upon burning coals, and dissolves in spirit of wine,
of which, however, it requires six parts to complete the solution.
This solution being evaporated to dryness leaves a matter in the form
of leaves lying on each other; on which account it hath obtained the
name of _Terra Foliata_. The same foliated matter will be obtained,
though the salt be not previously dissolved in spirit of wine; but not
so readily. This salt is also called _Regenerated Tartar_. Under the
head of Tartar we shall see the reason of these different appellations.
Regenerated Tartar is also in some degree capable of crystallizing: for
this purpose a solution thereof in water must be slowly evaporated to
the consistence of a syrup, and then suffered to stand quiet in a cool
place; by which means it will shoot into clusters of crystals, lying
one upon another, not unlike the feathers on a quill.

With Vinegar and several absorbent earths, such as calcined pearls,
coral, shells of fish, _&c._ are also formed neutral saline compounds,
each of which takes the name of the particular earth employed in its
composition.

Vinegar perfectly dissolves Lead, and converts it to a neutral metallic
salt, which shoots into crystals, and has a sweet saccharine taste.
This compound is called _Sugar of Lead_, or _Sal Saturni_.

If Lead be exposed to the bare vapour of Vinegar, it will be thereby
corroded, calcined, and converted into a white matter much used in
painting, and known by the name of _Ceruse_; or, when it is finer than
ordinary, _White Lead_.

Vinegar corrodes Copper likewise, and converts it into a beautiful
green rust, which also is used in painting; and distinguished by the
name of _Verdegris_. However, Vinegar is not commonly employed to make
Verdegris: for this purpose they use wine, or the rape of wine, from
which fire extricates an acid analogous to that of Vinegar.

In treating of the several substances which constitute wine, we
mentioned an acid matter, but did not then enter into a particular
examination thereof; because as that matter greatly resembles the acid
of Vinegar, we thought it more proper to defer the consideration of its
properties till we had treated of the acetous fermentation, and its
effects.


SECTION II.

_Of_ TARTAR.

This substance is a saline compound, consisting of earthy, oily, and
especially acid parts. It is found in the form of crusts, adhering to
the inner sides of vessels in which wines have stood for some time,
particularly acid wines, such as those of Germany.

Tartar derives its origin from the super-abundant quantity of acid
contained in the juice of the grape. This superfluous acid, being more
than is requisite to constitute the ardent spirit, unites with some of
the oil and earth contained in the fermented liquor, and forms a kind
of salt; which for some time continues suspended in that liquor, but,
when the wine stands undisturbed in a cool place, is deposited, as hath
been said, on the sides of the cask.

Tartar in this state contains many earthy parts, which are superfluous,
and foreign to its nature. From these it may be freed by boiling
it repeatedly with a sort of earth found in the neighbourhood of
Montpelier, as may be seen in the Memoirs of the Academy of Sciences.

When it is purified, there appears on the surface of the liquor a sort
of white, crystalline pellicle, which is skimmed off as it forms. This
matter is called _Cream of Tartar_. The same liquor which produces this
Cream, and in which the purified Tartar is dissolved, being set to
cool, yields a great number of white semi-transparent crystals, which
are called _Crystals of Tartar_. The Cream and the Crystals of Tartar
are therefore no other than purified Tartar, and differ from each other
in their form only.

Though the Crystals of Tartar have every appearance of a neutral salt,
yet they are far from being such; for they have all the properties of
a true acid, which scarce differs from that of vinegar, except that it
contains less water, and more earth and oil; to which it owes its solid
form, as well as its property of not being soluble in water without
much difficulty: for a very great quantity of water is requisite to
keep the Crystals of Tartar in solution; and it must moreover be
boiling hot; otherwise as soon as it cools most of the Tartar dissolved
in it separates from the liquor, and falls to the bottom in the form of
a white powder.

Tartar is decomposed by calcination in the open fire. All its oily
parts are consumed or dissipated in smoke, together with most of its
acid. The other part of its acid, uniting intimately with its earth,
forms a very strong and very pure fixed alkali, called _Salt of Tartar_.

It will be shewn in its proper place, that almost every vegetable
matter, as well as Tartar, leaves a fixed alkali in its ashes: yet
Tartar has these peculiar properties; first, it assumes an alkaline
character even when burnt or calcined in close vessels, whereas other
substances acquire it only by being burnt in the open air; secondly,
the alkali of Tartar is stronger and more saline than almost any that
is obtained from other matters.

This alkali, when thoroughly calcined, powerfully attracts the moisture
of the air, and melts into an unctuous alkaline liquor, improperly
called _Oil of Tartar per deliquium_. This is the alkali generally used
in making the _Terra Foliata_, mentioned under the head of Vinegar;
for which reason this combination is called _Terra Foliata Tartari_; a
name suitable enough. But the same cannot be said of the other name,
_Regenerated Tartar_, which is also given it. It is true, that on this
occasion an oily acid is restored to the earth of the Tartar, analagous
to that of which the fire had deprived it: but the compound thence
resulting is a neutral salt which very readily dissolves in water;
whereas Tartar is manifestly acid, and not soluble, or at least hardly
soluble, in water.

Crystals of Tartar combined with alkali of Tartar produce a great
effervescence while they are mixing, as all acids usually do; and if
the combination be brought exactly up to the point of saturation, a
perfectly neutral salt is formed, which shoots into crystals, and
easily dissolves in water; and this hath procured it the name of
_Soluble Tartar_. It is also called the _Vegetable Salt_, as being
obtained from vegetables only; and again, _Tartarised Tartar_, because
it consists of the acid and the alkali of Tartar combined together.

Crystals of Tartar combined with alkalis procured from the ashes of
maritime plants, such as Soda, which alkalis resemble the basis of
sea-salt, form likewise a neutral salt, which crystallizes well, and
dissolves easily in water. This salt is another sort of soluble
Tartar. It is called _Saignette's Salt_, from the inventor's name.

Both the Vegetable Salt and Saignette's Salt are gently purgative
soaps, and much used in Medicine.

Tartar likewise dissolves the absorbent earths, as lime, chalk, _&c._
and with them forms neutral salts which are soluble in water[3]. It
even attacks metallic bodies, and when combined with them becomes
soluble. A soluble Tartar for medical use is prepared with Crystals of
Tartar and Iron: the metallic salt thereby produced hath the name of
_Chalybeated Soluble Tartar_. This salt attracts the moisture of the
air, and is one of those which do not crystallize.

  [3] See Mr. Duhamel's Essays on this subject in the Memoirs of the
  Academy of Sciences.

Crystallized Tartar acts also upon several other metallic substances:
for instance, it dissolves the Regulus, Liver, and Glass of Antimony,
and thence acquires an emetic quality: it is then called _Stibiated_ or
_Emetic Tartar_. It likewise dissolves Lead, and therewith forms a salt
which, in the figure of its crystals, resembles Tartarised Tartar.

It is very extraordinary that Tartar, which of itself is not soluble in
water, should be soluble therein when become a neutral salt by uniting
either with alkalis or with absorbent earths, or even with metals. With
respect to alkalis, indeed, it may be urged, that, having themselves
a great affinity with water, they communicate to Tartar some of that
facility with which they naturally unite therewith: but the same cannot
be alledged concerning absorbent earths, and metallic substances, which
water dissolves not at all, or at least with great difficulty, and in
small quantity. This effect, therefore, must be attributed wholly to
some change in the disposition of its parts which is to us unknown.

All the Soluble Tartars are easily decompounded by exposing them to a
certain degree of heat. In distillation they yield the same principles
which are obtained from Tartar; and what remains fixed in the fire,
after they are thoroughly burnt, is a compound of the alkali which
Tartar naturally produces, and of the alkaline or metallic substance
with which it was converted into a neutral salt.

As Crystal of Tartar is the weakest of all acids, on account of the
oily and earthy matters with which it is combined, Soluble Tartars are
decompounded by all the acids; by any of which crystal of Tartar may be
separated from the substance that serves it for a basis and renders it
a neutral salt.

The other acids which are procured from vegetables, and even those
which are obtainable from some animal substances, may all be referred
to and compared with either Vinegar or Tartar, according to the
quantities of oil or earth with which they are combined.

After all, these acids have not yet been thoroughly examined. There
is great reason to think that they are no other than the mineral
acids, which, in passing through the bodies of vegetables, and even of
animals, undergo a considerable change, especially by contracting an
union with oily matters. For, as we said before in treating of Vinegar,
by freeing them from their oil they are brought very near to the nature
of mineral acids; and so likewise the mineral acids acquire many of the
properties of vegetable acids by being combined with oils.



CHAP. XV.

_Of the_ PUTRID FERMENTATION, _or_ PUTREFACTION.


Every body which hath gone through the two stages of fermentation above
described, that is, the spirituous and the acetous fermentation, being
left to itself in a due degree of warmth, which varies according to
the subject, advances to the last stage of fermentation; that is, to
putrefaction.

It is proper to observe, before we go any further, that the converse
of this proposition is not true; that is, it is not necessary that a
body should successively pass through the spirituous and the acetous
fermentation, before it can arrive at the putrid; but that, as certain
substances fall into the acetous without having gone through the
spirituous fermentation, so others begin to putrify without having
undergone either the spirituous or the acetous fermentation; of which
last kind are, for instance, most animal substances. When therefore
we represented these three sorts of fermentation as three different
degrees or stages of one and the same fermentation, we supposed it to
be excited in a body susceptible of fermentation in its full extent.

However, there is still room to think that every substance which is
capable of fermenting always passes necessarily through these three
different stages; but that the substances most disposed thereto pass
with such rapidity through the first, and even the second, that they
arrive at the third before our senses can perceive the least signs of
either of the two former. This opinion is not destitute of probability:
yet it is not supported by proofs sufficiently strong and numerous to
compel our assent.

When a body is in a putrefying state it is easy to discover (as in the
two sorts of fermentation already treated of) by the vapours which rise
from it, by the opacity which invades it, if a pellucid liquor, and
frequently even by a greater degree of heat than is found in the two
other sorts of fermentation, that an intestine motion is begun among
its constituent parts, which lasts till the whole be entirely putrefied.

The effect of this intestine motion is in this, as in the two other
sorts of fermentation, to break the union, and change the disposition,
of the particles constituting the body in which it is excited, and to
produce a new combination. This is brought about by a mechanism to
which we are strangers, and concerning which nothing beyond conjectures
can be advanced: but these we neglect, resolving to keep wholly to
facts, as the only things in Natural Philosophy that are positively
certain.

If, then, we examine a substance that has undergone putrefaction, we
shall soon perceive that it contains a principle which did not exist in
it before. If this substance be distilled, there rises, first, by means
of a very gentle heat, a saline matter which is exceedingly volatile,
and affects the organ of smelling briskly and disagreeably. Nor is the
aid of distillation necessary to discover the presence of this product
of putrefaction: it readily manifests itself in most substances where
it exists, as any one may soon be convinced by observing the different
smell of fresh and of putrefied urine; for the latter not only affects
the nose, but even makes the eyes smart, and irritates them so as to
draw tears from them in abundance.

This saline principle which is the product of putrefaction, when
separated from the other principles of the body which affords it, and
collected by itself, appears either in the form of a liquor, or in that
of a concrete salt, according to the different methods used to obtain
it. In the former state it is called a _Volatile Urinous Spirit_; and
in the latter a _Volatile Urinous Salt_. The qualification of urinous
is given it, because, as was said, a great deal thereof is generated in
putrefied urine, to which it communicates its smell. It goes also by
the general name of a _Volatile Alkali_, whether in a concrete or in
a liquid form. The enumeration of its properties will shew why it is
called an alkali.

Volatile Alkalis, from whatever substance obtained, are all alike,
and have all the same properties; differing only according to their
degrees of purity. The Volatile Alkali, as well as the Fixed, consists
of a certain quantity of acid combined with and entangled by a portion
of the earth of the mixt body from which it was obtained; and on that
account it has many properties like those of a Fixed Alkali. But there
is moreover in its composition a considerable quantity of a fat or oily
matter, of which there is none in a Fixed Alkali; and on this account
again there is a great difference between them. Thus the Volatility of
the Alkali produced by putrefaction, which is the principal difference
between it and the other kind of Alkali whose nature it is to be Fixed,
must be attributed to the portion of oil which it contains: for there
is a certain method of volatilizing Fixed Alkalis by means of a fatty
substance.

Volatile Alkalis have a great affinity with acids, unite therewith
rapidly and with ebullition, and form with them neutral salts, which
shoot into crystals, but differ from one another according to the kind
of acid employed in the combination.

The neutral salts which have a Volatile Alkali for their basis are
in general called _Ammoniacal Salts_. That whose acid is the acid of
sea-salt is called _Sal Ammoniac_. As this was the first known, it gave
name to all the rest. Great quantities of this salt are made in Egypt,
and thence brought to us. They sublime it from the soot of cow's dung,
which is the fuel of that country, and contains sea-salt, together with
a Volatile Alkali, or at least the materials proper for forming it; and
consequently all the ingredients that enter into the composition of Sal
Ammoniac. See the Memoirs of the Academy of Sciences.

The neutral salts formed by combining the acids of nitre and of vitriol
with a Volatile Alkali are called, after their acids, _Nitrous Sal
Ammoniac_, and _Vitriolic Sal Ammoniac_: the latter, from the name of
its inventor, is also called Glauber's _Secret Sal Ammoniac_.

A Volatile Alkali, then, has the same property as a Fixed Alkali with
regard to acids: yet they differ in this, that the affinity of the
former with acids is weaker than that of the latter: and hence it
follows, that any Sal Ammoniac may be decompounded by a Fixed Alkali,
which will lay hold of the acid, and discharge the Volatile Alkali.

A Volatile Alkali will decompound any neutral salt which has not a
Fixed Alkali for its basis; that is, all such as consist of an acid
combined with an absorbent earth or a metallic substance. By joining
with the acids in which they are dissolved, it disengages the earths or
metallic substances, takes their place, and, in conjunction with their
acids, forms Ammoniac Salts.

Hence it might be concluded, that, of all substances, next to the
Phlogiston and the Fixed Alkalis, Volatile Alkalis have the greatest
affinity with acids in general. Yet there is some difficulty in this
matter: for absorbent earths, and several metallic substances, are also
capable of decompounding Ammoniacal Salts, discharging their volatile
Alkali, and forming new compounds by uniting with their acids. This
might induce us to think, that these substances have nearly the same
affinity with acids.

But it is proper to observe, that a Volatile Alkali decompounds such
neutral salts as have for their basis either an absorbent earth or a
metallic substance, without the aid of fire; whereas absorbent earths
or metallic substances will not decompound an Ammoniacal Salt, unless
they be assisted by a certain degree of heat.

Now, as all these matters are extremely fixed, at least in comparison
with a Volatile Alkali, they have the advantage of being able to resist
the force of fire, and so of acting in conjunction therewith; and fire
greatly promotes the natural action of substances upon one another:
whereas the Volatile Alkali in the Ammoniacal Salt, being unable to
abide the force of fire, is compelled to desert its acid; and that
so much the more quickly, as its affinity therewith is considerably
weakened by the presence of an earthy or metallic substance, both of
which have a great affinity with acids.

These considerations oblige us to conclude, that Volatile Alkalis
have a somewhat greater affinity, than absorbent earths and metallic
substances, with acids.

Ammoniacal Salts projected upon nitre in fusion make it detonate; and
the Nitrous Sal Ammoniac detonates by itself, without the addition of
any inflammable matter. This singular effect evidently demonstrates
the existence of an oily matter in Volatile Alkalis; for it is certain
that nitre will never deflagrate without the concurrence, and even the
immediate contact, of some combustible matter.

This oily substance is often found combined with Volatile Alkalis in
such a large proportion as to disguise it, in some measure, and render
it exceedingly foul. The salt may be freed from its superfluous oil by
repeated sublimations; and particularly by subliming it from absorbent
earths, which readily drink up oils. This is called the _Rectification_
of a Volatile Alkali. The salt, which before was of a yellowish or
dirty colour, by being thus rectified becomes very white, and acquires
an odour more pungent and less fetid than it had at first, that is,
when obtained by one single distillation from a putrid substance.

It is proper to observe, that the rectification of a Volatile Alkali
must not be carried too far, or repeated too often; for by that means
it may be entirely decomposed at length; and particularly if an
absorbent earth, and especially chalk, be employed for that purpose,
the salt may be converted into an oil, an earth, and water.

Volatile Alkalis act upon several metallic substances, and particularly
on copper; of which they make a most beautiful blue solution. On this
property depends a pretty singular effect, which happens sometimes when
we attempt, by means of a Volatile Alkali, to separate copper from
any acid with which it is combined. Instead of seeing the liquor grow
turbid, and the metal fall, both which generally happen when any Alkali
whatever is mixed with a metallic solution, we are surprised to observe
the solution of copper, upon adding a Volatile Alkali, retain its
limpidity, and let fall no precipitate; or at least, if the liquor does
grow turbid, it remains so but for a moment, and instantly recovers its
transparency.

This is occasioned by adding such a quantity of Volatile Alkali as
is more than sufficient fully to saturate the acid of the solution,
and considerable enough to dissolve all the copper as fast as it is
separated from the acid. On this occasion the liquor acquires a deeper
blue than it had before; which arises from the property which Volatile
Alkalis have of giving this metal, when combined with them, a fuller
blue than any other solvent can: hence we have a touchstone to discover
copper wherever it is; for let the quantity of this metal combined
with other metals be ever so small, a Volatile Alkali never fails to
discover it, by making it appear of a blue colour.

Though a Volatile Alkali be constantly the result of putrefaction, yet
it must not therefore be imagined that none can be produced by any
other means; on the contrary, most of those substances which contain
the ingredients necessary to form it, yield no inconsiderable quantity
thereof in distillation. Tartar, for example, which by being burnt in
an open fire is converted, as was shewn, into a Fixed Alkali, yields a
Volatile Alkali when it is decomposed in close vessels; that is, when
it is distilled; because, in this latter case, the oily part is not
dissipated or burnt, as it is by calcination in a naked fire, but has
time to unite with some of the earth and acid of the mixt, in such a
manner as to form a true Volatile Alkali.

To prove that on this occasion, as well as on all others, where
unputrefied bodies yield a Volatile Alkali, this salt is the product of
the fire, we need only observe, that in these distillations it never
rises till after some part of the phlegm, of the acid, and even of the
thick oil of the mixt, is come over; which never is the case when it is
formed beforehand in the body which is the subject of the operation, as
it is in those which have undergone putrefaction: for this salt, being
much lighter and more volatile than those other substances, rises of
course before them in distillation.



CHAP. XVI.

_A General View of_ CHYMICAL DECOMPOSITION.


Though we have considered all the substances which enter into the
composition of Vegetables, Animals, and Minerals, whether as primary or
as secondary principles, it will not be improper to shew in what order
we obtain these principles from the several mixts; and especially from
Vegetables and Animals, because they are much more complicated than
Minerals. This is called _Analysing_ a compound.

The method most commonly taken to decompose bodies is by applying to
them successive degrees of heat, from the gentlest to the most violent,
in appropriated vessels, so contrived as to collect what exhales from
them. By this means the principles are gradually separated from each
other; the most volatile rise first, and the rest follow in order, as
they come to be acted on by the proper degree of heat: and this is
called _Distillation_.

But it being observed that fire, applied to the decomposition of
bodies, most commonly alters their secondary principles very sensibly,
by combining them in a different manner with each other, or even partly
decomposing them, and reducing them to their primitive principles;
other means have been used to separate those principles without the
help of fire.

With this view the mixts to be decomposed are forcibly compressed, in
order to squeeze out of them all such parts of their substance as they
will by this means part with: or else those mixts are for a long time
triturated, either along with water, which carries off all their saline
and saponaceous contents, or with solvents, such as ardent spirits,
capable of taking up every thing in them that is of an oily or resinous
nature.

We shall here give a succinct account of the effects of these different
methods, as applied to the principal substances among Vegetables and
Animals, and likewise to some Minerals.


SECTION I.

_The_ ANALYSIS _of_ VEGETABLE SUBSTANCES.

A vast many vegetable substances, such as kernels and seeds, yield,
by strong compression, great quantities of mild, fat, unctuous Oils,
which are not soluble in ardent spirits: these are what we called
_Expressed Oils_. They are also sometimes called _Fat Oils_, on account
of their unctuousness, in which they exceed all other sorts of Oil. As
these oils are obtained without the aid of fire, it is certain that
they existed in the mixt just as we see them, and that they are not in
the least altered: which could not have been the case had they been
obtained by distillation; for that never produces any Oils but such as
are acrid and soluble in spirit of wine.

Some vegetable matters, such as the rind of citrons, lemons, oranges,
_&c._ also yield, only by being squeezed between the fingers, a great
deal of Oil. This spirts out in fine small jets, which being received
upon any polished surface, such as a looking glass, run together and
form a liquor that is a real Oil.

But it must be carefully noted, that this sort of Oil, though obtained
by expression only, is nevertheless very different from the Oils
mentioned before, to which the title of _Expressed Oils_ peculiarly
belongs: for this is far lighter and thinner; moreover, it retains the
perfect odour of the fruit which yields it, and is soluble in spirit
of wine; in a word, it is a true essential Oil, but abounds so in
the fruits which produce it, and is lodged therein in such a manner,
occupying a vast number of little cells provided in the peel for its
reception, that a very slight pressure discharges it; which is not the
case with many other vegetables that contain an essential Oil.

Succulent and green plants yield by compression a great deal of liquor
or juice, which consists of most of the phlegm, of the salts, and a
small portion of the oil and earth of the plant. These juices, being
set in a cool place for some time, deposite saline crystals, which are
a combination of the acid of the plant with part of its oil and earth,
wherein the acid is always predominant. These salts, as is evident from
the description here given, bear a great resemblance to the tartar
of wine treated of above. They are called _Essential Salts_; so that
Tartar might likewise be called the _Essential Salt of Wine_.

Dried plants, and such as are of a ligneous, or acid nature, require to
be long triturated with water, before they will yield their essential
salts. Trituration with water is an excellent way to get out of them
all their saline and saponaceous contents.

A vegetable matter that is very oily yields its essential salt with
much difficulty, if at all; because the excessive quantity of oil
entangles the salt so that it cannot extricate itself or shoot into
crystals. Mr. Gerike, in his _Principles of Chymistry_, says, that
if part of the oil of a plant be extracted by spirit of wine, its
essential salt may be afterwards obtained with more ease and in greater
quantity. This must be a very good method for such plants as have an
excessive proportion of essential oil; but will not succeed if the
essential salt be hindered from crystallizing by a redundancy of fat
oil, because fat oils are not soluble in spirit of wine.

Essential Salts are among those substances which cannot be extracted
from mixts by distillation: for the first impression of fire decomposes
them.

Though the acid which predominates in the Essential Salts of plants,
be most commonly analogous to the vegetable acid, properly so called,
that is, to the acid of vinegar and tartar, which is probably no other
than the vitriolic acid disguised; yet it sometimes differs therefrom,
and somewhat resembles the nitrous or the marine acid. This depends
on the places where the plants grow which produce these salts: if
they be maritime plants, their acid is akin to the acid of sea-salt;
if on the contrary they grow upon walls, or in nitrous grounds, their
acid is like that of nitre. Sometimes one and the same plant contains
salts analogous to all the three mineral acids; which shews that the
vegetable acids are no other than the mineral acids variously changed
by circulating through plants.

Liquors containing the Essential Salts of plants being evaporated by a
gentle heat to the consistence of honey, or even further, are called
_Extracts_. Hence it is plain, that an Extract is nothing but the
essential salt of a plant, combined with some particles of its oil and
earth, that remained suspended in the liquor, and are now incorporated
by evaporation.

Extracts of plants are also prepared by boiling them long in water, and
then evaporating some part of it. But these Extracts are of inferior
virtue; because the fire dissipates many of the oily and saline parts.


EMULSIONS.

Substances which abound much in Oil, being bruised and triturated
with water for some time, afford a liquor of an opaque dead-white
colour, like milk. This liquor consists of such juices as the water is
capable of dissolving, together with a portion of the oil, which being
naturally indissoluble in water, is only divided and dispersed in the
liquor, the limpidity whereof is by that means destroyed. This sort of
oily liquor, in which the oil is only divided, not dissolved, is called
an _Emulsion_. The oily particles in Emulsions spontaneously separate
from the water, when left at rest, and uniting into greater masses
rise, on account of their lightness, to the surface of the liquor,
which by that means recovers a degree of transparency.

If vegetables abounding in essential oils and resins be digested in
spirit of wine, the menstruum takes up these oily matters, as being
capable of dissolving them; and they may afterwards be easily separated
from it by the affusion of water. The water, with which spirit of wine
has a greater affinity than with oily matters, separates them by this
means from their solvent, agreeably to the common laws of affinities.

Without the help of fire, scarce any thing, besides the substances
already mentioned, can be obtained from a plant: but, by the means
of distillation, we are enabled to analyse them more completely.
In prosecuting this method of extracting from a plant the several
principles of which it consists, the following order is to be observed.

A plant being exposed to a very gentle heat, in a distilling vessel set
in the _balneum mariæ_, yields a water which retains the perfect smell
thereof. Some Chymists, and particularly the illustrious Boerhaave,
have called this liquor the _Spiritus Rector_. The nature of this
odoriferous part of plants is not yet thoroughly known; because it is
so very volatile that it is difficult to subject it to the experiments
necessary for discovering all its properties.

If, instead of distilling the plant in the _balneum mariæ_, it be
distilled over a naked fire, with the precaution of putting a certain
quantity of water into the distilling vessel along with it, to prevent
its suffering a greater heat than that of boiling water, all the
essential oil contained in that plant will rise together with that
water, and with the same degree of heat.

On this occasion it must be observed, that no essential oil can be
obtained from a plant after the _Spiritus Rector_ hath been drawn off;
which gives ground to think that the volatility of these oils is owing
to that spirit.

The heat of boiling water is also sufficient to separate from vegetable
matters the fat oils which they contain. That, however, is to be done
by the way of decoction only, and not by distillation: because, though
these oils will swim on water, yet they will not rise in vapours
without a greater degree of heat.

When the essential oil is come over, if the plant be exposed to a
naked fire, without the addition of water, and the heat be increased
a little, a phlegm will rise that gradually grows acid; after which,
if the heat be increased as occasion requires, there will come over a
thicker and heavier oil; from some a volatile alkali; and last of all,
a very thick, black, empyreumatic oil.

When nothing more rises with the strongest degree of heat, there
remains of the plant a mere coal only, called the _Caput Mortuum_, or
_Terra Damnata_. This coal when burnt falls into ashes, which, being
lixiviated with water, give a fixed alkali.

It is observable, that in the distillation of plants which yield
an acid and a volatile alkali, these two salts are often found
quite distinct and separate in the same receiver; which seems very
extraordinary, considering that they are naturally disposed to
unite, and have a great affinity with one another. The reason of
this phenomenon is, that they are both combined with much oil, which
embarrasses them so that they cannot unite to form a neutral salt, as
they would not fail to do were it not for that impediment.

All vegetables, except such as yield a great deal of volatile alkali,
being burnt in an open fire, and so as to flame, leave in their ashes
a large quantity of an acrid, caustic, fixed alkali. But if care be
taken to smother them, so as to prevent their flaming while they burn,
by covering them with something that may continually beat down again
what exhales, the salt obtained from their ashes will be much less
acrid and caustic; the cause whereof is, that some part of the acid
and oil of the plant being detained in the burning, and stopped from
being dissipated by the fire, combines with its alkali. These salts
crystallize, and, being much milder than the common fixed alkalis, may
be used in medicine, and taken internally. They are called _Tachenius's
Salts_, because invented by that Chymist.

Marine plants yield a fixed alkali analogous to that of sea-salt.
As for all other plants or vegetable substances, the fixed alkalis
obtained from them, if rightly prepared and thoroughly calcined, are
all perfectly alike, and of the very same nature.

The last observation I have to make on the production of fixed alkalis
is, that if the plant you intend to work upon be steeped or boiled
in water before you burn it, a much smaller quantity of salt will
be obtained from it; nay, it will yield none at all, if repeated
boilings have robbed it entirely of those saline particles which must
necessarily concur with its earth to form a fixed Alkali.


SECTION II.

_The_ ANALYSIS _of_ ANIMAL SUBSTANCES.

Succulent animal substances, such as new-killed flesh, yield by
expression a juice or liquid, which is no other than the phlegm,
replete with all the principles of the animal body, except the earth,
of which it contains but little. The hard or dry parts, such as the
horns, bones, _&c._ yield a similar juice, by boiling them in water.
These juices become thick, like a glue or jelly, when their watery
parts are evaporated; and, in this state, they are truly extracts of
animal matters. These juices afford no crystals of essential salt,
like those obtained from vegetables, and shew no sign either of an acid
or an alkali.

Great part of the oil which is in the flesh of animals may be easily
separated without the help of fire; for it lies in a manner by itself:
it is commonly in a concrete form, and is called _Fat_. This oil
somewhat resembles the fat oils of vegetables; for like them it is
mild, unctuous, indissoluble in spirit of wine, and is subtilized and
attenuated by the action of fire. But there is not in animals, as in
vegetables, any light essential oil, which rises with the heat of
boiling water; so that, properly speaking, animals contain but one sort
of oil.

Few animal substances yield a perceptible acid. Ants and bees are
almost the only ones from which any can be obtained: and indeed the
quantity they yield is very small, as the acid itself is extremely weak.

The reason thereof is, that as animals do not draw their nourishment
immediately from the earth, but feed wholly either on vegetables or
on the flesh of other animals, the mineral acids, which have already
undergone a great change by the union contracted between them and
the oily matters of the vegetable kingdom, enter into a closer union
and combination with these oily parts while they are passing through
the organs and strainers of animals; whereby their properties are
destroyed, or at least so impaired, that they are no longer sensible.

Animal matters yield in distillation, first, a phlegm, and then, on
increasing the fire, a pretty clear oil, which gradually becomes
thicker, blacker, more fetid, and empyreumatic. It is accompanied
with a great deal of volatile alkali; and if the fire be raised
and kept up till nothing more comes over, there will remain in the
distilling vessel a coal like that of vegetables; except that when it
is reduced to ashes, no fixed alkali, or at least very little, can be
obtained from them, as from the ashes of vegetables. This arises from
hence, that, as we said before, the saline principle in animals being
more intimately united with the oil than it is in plants, and being
consequently more attenuated and subtilized, is too volatile to enter
into the combination of a fixed alkali; on the contrary, it is more
disposed to join in forming a volatile alkali, which on this occasion
does not rise till after the oil, and therefore must certainly be the
production of the fire. It must be observed, that all we have hitherto
said concerning the analysis of bodies must be understood of such
matters only as have not undergone any sort of Fermentation.

The chyle and milk of animals which feed on plants still retain some
likeness to vegetables; because the principles of which these liquors
are composed have not gone through all the changes which they must
suffer before they enter into the animal combination.

Urine and sweat are excrementitious aqueous liquors, loaded chiefly
with the saline particles which are of no service towards the
nourishment of the animal, but pass through its strainers without
receiving any alteration; such as the neutral salts which have a fixed
alkali for their basis, and particularly the sea-salt, which happens
to be in the food of animals, whether it exist therein naturally, as
it does in some plants, or whether the animals eat it to please their
palates.

The saliva, the pancreatic juice, and especially the bile, are
saponaceous liquors, that is, they consist of saline and oily particles
combined together: so that being themselves dissolved in an aqueous
liquor, they are capable of dissolving likewise the oily parts, and of
rendering them miscible with water.

Lastly, the blood being the receptacle of all these liquors partakes of
the nature of each, more or less in proportion to the quantity thereof
which it contains.


SECTION III.

_The_ ANALYSIS _of_ MINERAL SUBSTANCES.

Minerals differ greatly from vegetables, and from animals; they are
not near so complex as those organized bodies, and their principles
are much more simple; whence it follows, that these principles are
much more closely connected, and that they cannot be separated without
the help of fire; which not having on their parts the same action and
the same power as on organized bodies, hath not the same ill effect
on them; I mean the effect of changing their principles, or even
destroying them entirely.

I do not here speak of pure, vitrifiable, or refractory earths; of
mere metals and semi-metals; of pure acids; or even of their simplest
combinations, such as sulphur, vitriol, alum, sea-salt: of all these we
have said enough.

We are now to treat of bodies that are more complex, and therefore more
susceptible of decomposition. These bodies are compound masses, or
combinations of those above-mentioned; that is, metallic substances as
they are found in the bowels of the earth, united with several sorts
of sand, stones, earths, semi-metals, sulphur, _&c._ When the metallic
matter is combined with other matters, in such a proportion to the
rest that it may be separated from them with advantage and profit,
these compounds are called _Ores_; when the case is otherwise, they are
called _Pyrites_, and _Marcasites_; especially if sulphur or arsenic be
predominant therein, which often happens.

In order to analyse an ore, and get out of it the metal it contains,
the first step is to free it from a great deal of earth and stones,
which commonly adhere to it very slightly and superficially. This
is effected by pounding the ore, and then washing it in water; to
the bottom of which the metalline parts presently sink, as being the
heaviest, while the small particles of earth and stone remain suspended
some time longer.

Thus the metallic part is left combined with such matters only as are
most intimately complicated with it. These substances are most commonly
sulphur and arsenic. Now, as they are much more volatile than other
mineral matters, they may be dissipated in vapours, or the sulphur may
be consumed, by exposing the ore which contains them to a proper degree
of heat. If the sulphur and arsenic be desired by themselves, the fumes
thereof may be catched and collected in proper vessels and places. This
operation is called _Roasting_ an Ore.

The metal thus depurated is now fit to be exposed to a greater force of
fire, capable of melting it.

On this occasion the semi-metals and the imperfect metals require
the addition of some matter abounding in phlogiston, particularly
charcoal-dust; because these metallic substances lose their phlogiston
by the action of the fire, or of the fluxes joined with them, and
therefore without this precaution would never acquire either the
splendour or the ductility of a metal. By this means the metallic
substance is more accurately separated from the earthy and stony parts,
of which some portion always remains combined therewith till it is
brought to fusion. For, as we observed before, a metallic glass or calx
only will contract an union with such matters; a metal possessed of its
phlogiston and metalline form being utterly incapable thereof.

We took notice of the cause of this separation above, where we shewed
that a metal possessed of its phlogiston and metalline form will not
remain intimately united with any calcined or vitrified matter, not
even with its own calx or glass.

The metal therefore on this occasion gathers into a mass, and lies
at the bottom of the vessel, as being most ponderous; while the
heterogeneous matters float upon it in the form of a glass, or a
semi-vitrification. These floating matters take the name of _Scoriæ_,
and the metalline substance at bottom is called the _Regulus_.

It frequently happens, that the metalline regulus thus precipitated
is itself a compound of several metals mixed together, which are
afterwards to be separated. We cannot at present enter into a detail
of the operations necessary for that purpose: they will appear in our
Treatise of _Practical Chymistry_: but the principles on which they are
founded may be deduced from what we have said above, concerning the
properties of the several metals and of acids.

It is proper to observe, before we quit this subject, that the rules
here laid down for analysing ores are not absolutely general: for
example, it is often adviseable to roast the ore before you wash it;
for by that means some ores are opened, attenuated, and made very
friable, which would cost much trouble and expence, on account of their
excessive hardness, if you should attempt to pound them without a
previous torrefaction.

It is also frequently necessary to separate the ore from part only
of its stone; sometimes to leave the whole; and sometimes to add
more to it, before you smelt it. This depends on the quality of the
stone, which always helps to promote fusion when it is in its own
nature fusible and vitrifiable. It is then called the _Fluor_ of the
ore: but of this we must say, as we did of the preceding article, it
is sufficient for our present purpose to lay down the fundamental
principles on which the reason of every process is built; the
description of the operations themselves being reserved for our second
Part.

We shall now give a succinct account of the principal ores and mineral
bodies, contenting ourselves with just pointing out the particulars of
which they severally consist.


_Of the_ PYRITES.

_The yellow Pyrites._

The yellow Pyrites is a mineral consisting of sulphur, iron, an
unmetallic earth, and frequently a little copper: the sulphur, which
is the only one of these principles that is volatile, may be separated
from the rest by sublimation: it usually makes a fourth, and sometimes
a third, of the whole weight of these Pyrites. The other principles are
separated from one another by fusion and reduction with the phlogiston,
which, by metallizing the ferruginous and cupreous earths, parts
them from the unmetallic earth: for this earth vitrifies, and cannot
afterwards continue united with metallic matters possessed of their
metalline form, as hath been said before.

There is yet another way of decomposing the yellow Pyrites, which is to
let it ly till it effloresces, or begins to shoot into flowers; which
is nothing but a sort of slow accension of the sulphur it contains.
The sulphur being by this means decomposed, its acid unites with the
ferruginous and cupreous parts of the Pyrites, and therewith forms
green and blue vitriols; which may be extracted by steeping in water
the Pyrites which has effloresced or been burnt, and then evaporating
the lixivium to a pellicle; for by this means the vitriol will shoot
into crystals.

Sometimes the Pyrites contains also an earth of the same nature with
that of alum; a Pyrites of this sort, after flowering, yields alum as
well as vitriol.


_The white Pyrites._

The white Pyrites contains much arsenic, a ferruginous earth, and an
unmetallic earth. The arsenic, being a volatile principle, may be
separated by sublimation or distillation from the rest, which are
fixed: and these again may be disjoined from each other by fusion and
reduction, as was said in relation to the yellow Pyrites.


_The Copper Pyrites._

The Copper Pyrites contains sulphur, copper, and an unmetallic earth.
A great deal thereof likewise holds arsenic, and its colour approaches
more or less to orange, yellow, or white, according to the quantity of
arsenic in it. It may be decomposed by the same means as the yellow and
white Pyrites.

_Of_ ORES.

_Of Gold Ores._

Gold being constantly found in its metalline form, and never combined
with sulphur and arsenic, its matrices are not, properly speaking,
ores; because the metal contained in them is not mineralized. The
gold is only lodged between particles of stone, earth, or sand, from
which it is easily separated by lotion, and by amalgamation with
quick-silver. The gold thus found is seldom pure, but is frequently
alloyed with more or less silver, from which it is to be separated by
quartation.

It is also very common to find gold in most ores of other metals or
semi-metals, and even in the Pyrites; but the quantity contained
therein is generally so small, that it would not pay the cost of
extracting it. However, if any should incline to attempt it, merely
out of curiosity, it would be necessary to begin with treating these
ores in the manner proper for separating their metalline part; then to
cupel the metalline regulus so obtained; and, lastly, to refine it by
quartation.


_Of Silver Ores._

It is no rare thing to find silver, as well as gold, in its metalline
form, only lodged in sundry earths and stony matters, from which it may
be separated in the same manner as gold. But the greatest quantities
of this metal are usually dug out of the bowels of the earth in a
truly mineral state: that is, combined with different substances, and
particularly with sulphur and arsenic.

Several silver ores are distinguished by peculiar characteristics, and
are accordingly denoted by particular names. That which is called the
_Vitreous Silver Ore_, is scarce any thing else but a combination of
silver and sulphur. Another is known by the name of the _Horny Silver
Ore_, because when in thin plates it is semi-transparent: in this ore
the silver is mineralized by sulphur and a little arsenic. The _Red
Silver Ore_ is of the colour which its name imports, sometimes more,
sometimes less vivid; and is chiefly composed of silver, arsenic, and
sulphur: it also contains a little iron.

These three ores are very rich in silver: the first contains nearly
three fourths of its weight, and the others about two thirds of theirs.

There is a fourth, called the _White Silver Ore_, which, though it be
heavier, is not so rich in silver, because it contains much copper.
Many other minerals contain silver, yet are not, properly speaking,
silver ores; because a much greater quantity of other metals than of
silver is found in them.

When a silver ore is to be decomposed, in order to have the silver
pure, or when silver is to be extracted out of any ore that contains
it, the first thing to be done is to roast the ore, in order to clear
it of the volatile minerals: and as silver cannot be had pure without
the operation of the cupel, which requires more or less lead to be
joined with it, it is usual to mix with the torrified silver ore a
quantity of lead, proportioned to that of the heterogeneous matters
combined with the silver, and to melt the whole together. Part of the
added lead vitrifies during the fusion, and at the same time converts
some of the heterogeneous matters also into glass, with which it forms
a scoria that rises to the surface of the matter. The other part of the
lead, with which the silver is mixed, falls to the bottom in the form
of a regulus, which must be cupelled in order to have the silver pure.


_Of Copper Ores._

Copper is much seldomer found in a metalline form than gold or silver:
it is commonly in a mineral state: it is mineralized by sulphur and
arsenic: almost all its ores contain also more or less of iron;
sometimes a little silver, or even gold, together with unmetallic
earths and stones, as all ores do.

Most copper ores are of a beautiful green or blue, or else in shades
blended of these two colours. The minerals called _mountain green_, and
_mountain blue_, are true copper ores; not in the form of hard stones,
like other ores, but crumbly and friable like earth.

Nevertheless, there are several copper ores of different colours, as
ash-coloured, whitish, and shaded with yellow or orange; which colours
arise from the different proportions of arsenic, sulphur, and iron,
which these ores contain.

In order to decompose a copper ore, and to extract the copper it
contains, it is first of all to be freed from as many of its earthy,
stony, sulphureous, and arsenical parts, as is possible, by roasting
and washing; then what remains is to be mixed with a flux, compounded
of a fixed alkali and some inflammable matter; a little sea-salt is
to be put over all, and the whole melted by a strong fire. The salts
facilitate the fusion and scorification of the unmetallic matters, and
therewith form a slag, which being the lightest rises to the surface.
The metalline matters are collected below in the form of a shining
regulus of copper; which, however, is not usually fine copper, but
requires to be purified in the manner to be shewn in our second part.

In order to separate the copper from the unmetallic matters, it is
absolutely necessary to melt its ore along with inflammable substances
abounding in phlogiston. For, as this metal is not possessed of its
metalline form while it is in a mineral state, as it is destitute of
the true quantity of phlogiston, and, though it were not, would lose it
by the action of the fire, it would come to pass, that if its ore were
melted without the addition of any inflammable matter, the cupreous
earth or calx would be scorified and confounded with the unmetallic
matters; and as all metallic matters, except gold and silver, are
subject to this inconvenience as well as copper, the addition of an
inflammable substance, in fluxing all ores that contain them, is a
general rule that ought constantly to be observed.


_Of Iron Ores._

Iron is seldom found pure and malleable in the earth; yet it is much
seldomer found in the mineral state, properly so called, than any of
the other metals: for most iron ores are scarce any thing more than a
ferruginous earth mixed in different proportions with unmetallic earths
and stones. Some of them, however, contain also volatile minerals, such
as sulphur and arsenic; and therefore it is necessary to roast the iron
ores, like all others, before you attempt to extract the metal out of
them. That being done, they are to be smelted with a flux consisting of
fusible and inflammable matters, as the general rule directs.

Iron is the commonest of all metals: nay, it is so universally diffused
through the earth, that it is difficult to find any stone, earth, or
sand, that does not contain some of it; and therefore none of these are
usually considered and treated as iron ores, except such as contain a
great deal of that metal, and melt easily. The hematites, emery, yellow
pyrites, calamine, all contain a pretty considerable quantity of iron;
but no body attempts to extract it from them, because they are very
hard to melt.

Ferruginous earth being naturally of an orange colour, a stone or earth
may be judged to contain iron, if either naturally, or after roasting,
it appears to have one shade of yellow or red.

The singular property which iron has of being attracted by the magnet,
and of being the only body, exclusive of all others, that is so,
likewise affords us an easy method of discovering the presence of
this metal among other matters, where it often exists in such a small
quantity that it could not otherwise be found out. For this purpose
the body in which iron is suspected to lurk, must be pulverised and
torrefied with some inflammable matter; and then the powder thus
roasted being touched with a magnet, or an animated bar, if it contains
any particles of iron they will infallibly adhere to the magnet or bar.


_Of Tin Ores._

Tin is never found in the earth pure and malleable, but always in a
mineral state, and always mineralized by arsenic. Tin ores are not
sulphureous; whence it comes, that though tin be the lightest of all
metals, its ores are nevertheless heavier than those of other metals,
as arsenic greatly exceeds sulphur in gravity. Some tin ores contain
also a little iron. The ores of tin are to be washed, roasted, and
smelted with a reducing flux, according to the general rules.


_Of Lead Ores._

Lead, like tin, is never found but in a mineral state. It is most
commonly mineralized by sulphur; yet there are some lead ores which
also contain arsenic.

Lead ores, as well as others, must be roasted and smelted with a
reducing flux: however, as it is difficult to free them from all their
sulphur by torrefaction only, the reducing flux employed in their
fusion may be made up with a quantity of iron filings, which being
incapable of any union with lead, and having a much greater affinity
than that metal with sulphur, will, on this occasion, be of great
service by interposing between them.


_Of Quick-silver Ores._

Running Mercury is sometimes found in certain earths, or grey, friable
stones; but most commonly in a mineral state. It is always mineralized
by sulphur, and by sulphur alone: so that cinabar is the only ore of
quick-silver that we know of; and a very rich one it is, seeing it
contains six or seven times as much mercury as sulphur.

Roasting can be of no use towards decomposing the ore of mercury, and
separating its sulphur; because mercury being itself very volatile
would be carried off by the fire together with the sulphur. In order,
therefore, to part the two substances of which cinabar consists,
recourse must necessarily be had to some third body, which will unite
with one of them, and by that means separate it from the other. Now
all the metals, except gold, having a greater affinity than mercury
with sulphur, such a body is easily found: any metal but gold may be
employed with success in this decomposition; but as iron hath a greater
affinity with sulphur than any of the rest, and is moreover the only
one that cannot unite with mercury, it must, on account of these two
qualities, be preferred to all the rest.

Fixed alkalis are also well qualified to absorb the sulphur of cinabar.
Cinabar must be decomposed in close vessels, and by the way of
distillation; otherwise the mercury, as soon as it separates from the
sulphur, will be dissipated in vapours and entirely lost.

In this operation it is needless to add either flux or phlogiston;
because the cinabar is decomposed without melting, and the mercury,
though in a mineral state, contains, like gold and silver, all the
phlogiston requisite to secure its metalline properties.


_Of the Ores of Regulus of Antimony._

Regulus of Antimony is always found in a mineral state: it is
mineralized by sulphur; but sometimes, though rarely, it is also
combined with a little arsenic.

When the ore of regulus of antimony is to be decomposed, the first
thing to be done is to expose it to a degree of heat too weak to melt
its earthy and stony parts, but strong enough to fuse its reguline,
together with its sulphureous parts, which by this means are separated
from the earth, and united into one mass, known by the name of Antimony.

It is plain that this first operation, which is founded on the great
fusibility of antimony, produces, with regard to the ore of regulus
of antimony, the same effect that washing hath on other ores: so that
after this first fusion nothing more is requisite to the obtaining of
a pure regulus of antimony, but to separate it from its sulphur by
roasting, and to melt it with some matter abounding in phlogiston,
in the same manner as other metallic matters are treated. The term
_Calcination_ is generally used to express this torrefaction of
antimony, by means whereof the metallic earth of the regulus of
antimony is separated from its sulphur.

As regulus of Antimony hath, like Mercury, much less affinity with
sulphur than the other metals have, it follows that antimony may be
decomposed by the same means as cinabar; but the regulus, so obtained,
is adulterated with a portion of the additament made use of, which
combines therewith.

There is still another process employed for obtaining the regulus of
antimony: it consists, as was mentioned in its place, in detonating
the mineral with a mixture of nitre and tartar, applied in such a
proportion that, after the detonation has consumed the sulphur, there
may remain so much inflammable matter as will be sufficient to furnish
the metalline earth of the antimony with the phlogiston necessary to
preserve its metallic properties. But by this method less regulus is
produced, than by calcining, or torrefying, and reducing as usual.


_Of the Ores of Bismuth._

The ore of Bismuth consists of the semi-metal mineralized by arsenic,
and of an unmetallic earth. It is very easy to decompose this ore,
and to extract the bismuth it contains: for this purpose it need only
be exposed to a moderate heat, whereby the arsenic will be dissipated
in vapours, and the bismuth melted, which will then separate from the
unmetallic earth. This earth, at least, in several ores of bismuth,
possesses the property of tinging all vitrifiable matters, with which
it is melted, of a beautiful blue colour.

To decompose the ore of bismuth no flux or inflammable matter is used;
because this semi-metal is possessed, even in its mineral state, of
all the phlogiston requisite to maintain its metalline properties; and
its great fusibility makes it unnecessary to melt the unmetallic earth
contained in its ore.


_Of the Ores of Zinc._

Zinc is not generally obtained from a particular ore of its own; but
sublimes during the fusion of a mineral, or rather a confused mass of
minerals, that contains this semi-metal together with iron, copper,
lead, sulphur, arsenic, and, like all other ores, an unmetallic earth.

Nevertheless, there is a substance which may be considered as the
proper ore of zinc, because it contains a pretty large quantity of
that semi-metal, a little iron, and an unmetallic earth. It is called
_Calamine_, or _Lapis Calaminaris_; but hitherto the art of procuring
zinc directly from this mineral hath no where been practised. Calamine
is commonly employed only to convert copper into brass, or a yellow
metal, by cementing it therewith. Indeed, till lately, no easy or
practicable method of obtaining pure zinc from calamine was publicly
known; for that semi-metal being volatile and very inflammable, its ore
cannot be fused like others. Mr. Margraaf was the first who, by mixing
powdered charcoal with calamine in close vessels, obtained a perfect
zinc from it, by the means of distillation or sublimation, as shall be
shewn in our Practical Chymistry.


_Of Arsenical Minerals._

Arsenic, as well as sulphur, is naturally combined with almost all
ores, or minerals containing metallic substances. As it is very
volatile, while the matters with which it is united are fixed, at least
in comparison therewith, it is easily separated by sublimation.

The minerals that contain most arsenic are the white pyrites, orpiment,
and cobalt. We have already considered the white pyrites: as to
orpiment, it consists of sulphur and arsenic. Both these substances
being very volatile, it is difficult to separate them by sublimation:
yet, with proper management, and a due regulation of the fire, this
separation may be effected; because sulphur sublimes a little more
easily than arsenic. But it is more convenient, as well as more
expeditious, to make use of some additament that hath a greater
affinity with one of those substances than with the other. Fixed
alkalis and mercury, both of which have more affinity with sulphur than
with arsenic, may be very properly employed on this occasion.

Cobalt is a mineral composed of arsenic, an unmetallic earth, and
frequently bismuth: and as none of these are very volatile, except the
arsenic, this may be easily separated from the rest by sublimation. The
unmetallic earth which remains has, like that of the ore of bismuth,
the property of giving a blue colour to any vitrifiable matters
melted with it; whence it is conjectured, that cobalt and the ore
of bismuth have a great resemblance, or are often blended with each
other. Nevertheless, Mr. Brant, an ingenious Swedish Chymist, insists
that they are very different: he pretends that the metallic substance
contained in the true cobalt is a semi-metal of a peculiar nature,
which hath been erroneously confounded with bismuth: and indeed he
proves by a great number of curious experiments, related in the Memoirs
of the Academy of Upsal, that these two metallic substances have
properties that are essentially different: to that which is obtained
from cobalt, he gives the name of _Regulus of Cobalt_.

Besides the minerals already recited, there is found in the bowels of
the earth another species of compound body, of which we have already
taken notice; but which is supposed, with some degree of probability,
to belong as much to the vegetable as to the mineral kingdom: I mean
the _Bitumens_; which the best observations oblige us to consider as
vegetable oils, that by lying long in the earth have contracted an
union with the mineral acids, and by that means acquired the thickness,
consistence, and other properties observable in them.

By distillation they yield an oil, and an acid not unlike a mineral
acid. Mr. Bourdelin has even demonstrated, by a very artful and
ingenious process, that amber contains a manifest acid of sea-salt. See
the Memoirs of the Royal Academy of Sciences.



CHAP. XVII.

_Explanation of the Table of Affinities_.


It hath been shewn in the course of this work, that the causes of
almost all the phenomena, which Chymistry exhibits, are deducible from
the mutual affinities of different substances, especially the simplest.
We have already explained (Chap. II.) what is meant by affinities, and
have laid down the principal laws to which the relations of different
bodies are subject. The late Mr. Geoffroy, one of the best Chymists we
have had, being convinced of the advantages which all who cultivate
Chymistry would receive from having constantly before their eyes a
state of the best ascertained relations between the chief agents in
Chymistry, was the first who undertook to reduce them into order, and
unite them all in one point of view, by means of a table. We are of
opinion, with that great man, that this Table will be of considerable
use to such as are beginning to study Chymistry, in helping them to
form a just idea of the relations which different substances have with
one another; and that the practical Chymist will thereby be enabled
to account for what passes in several of his operations, otherwise
difficult to be understood, as well as to judge what may be expected to
result from mixtures of different compounds. These reasons have induced
us to insert it at the end of this Elementary Treatise, and to give a
short explanation of it here; especially as it will serve, at the same
time, for a recapitulation of the whole work, in which the several
axioms of this Table are dispersed.

You have it here just as it was drawn up by Mr. Geoffroy, without any
addition or alteration. I own, however, that it might be improved
both ways: for since the death of that great Chymist many experiments
have been made, some of which have discovered new affinities, and
others have raised exceptions to some of those laid down by him. But
several reasons dissuade me from publishing a new Table of Affinities,
containing all the emendations and innovations that might be made in
the old one.

The first is, that many of the affinities lately discovered are not yet
sufficiently verified, but, on the contrary, subject to be contested:
in short, they are perhaps liable to more considerable objections, and
exceptions, than the other.

The second is, that as Mr. Geoffroy's Table contains all the
fundamental affinities, it is more suitable to an Elementary Treatise
than a much fuller one would be; seeing this would necessarily suppose
the knowledge of many things not treated of by us, and of which it was
not proper to say any thing in such a book as this.

However, as it is essential to our purpose that we lead none into
error, we shall take care in explaining the affinities delivered by Mr.
Geoffroy, to mention the principal objections and exceptions to which
they are liable: we shall, moreover, add a very few new ones, confining
ourselves to such only as are elementary and well ascertained.

The upper line of Mr. Geoffroy's Table, comprehends several substances
used in Chymistry. Under each of those substances are ranged in
distinct columns several matters compared with them, in the order
of their relation to that first substance; so as that which is the
nearest to it is that which hath the greatest affinity with it, or that
which none of the substances standing below it can separate therefrom;
but which, on the contrary, separates them all when they are combined
with it, and expels them in order to join itself therewith. The same is
to be understood of that which occupies the second place of affinity;
that is, it has the same property with regard to all below it, yielding
only to that which is above it: and so of all the rest.

At the top of the first column stands the character which denotes an
Acid in general. Immediately under this stands the mark of a Fixed
Alkali, being placed there as the substance which has the greatest
affinity with an Acid. After the Fixed Alkali appears the Volatile
Alkali, whose affinity with Acids yields only to the Fixed Alkali.
Next come the Absorbent Earths; and last of all Metallic Substances.
Hence it follows, that when a Fixed Alkali is united with an acid it
cannot be separated therefrom by any other substance; that a Volatile
Alkali united with an Acid cannot be separated from it by any thing
but a Fixed Alkali; that an Absorbent Earth combined with an acid
may be separated from it either by a Fixed or by a Volatile Alkali;
and lastly, that any Metallic Substance combined with an Acid may be
separated from it by a Fixed Alkali, a Volatile Alkali, or an Absorbent
Earth.

There are many important remarks to be made on this first column.
First, it is making the rule too general to say that any Acid whatever
has a greater affinity with a Fixed Alkali, than with any other
substance. And indeed Mr. Geoffroy himself hath made an exception
with respect to the Vitriolic Acid; for in the fourth column, at the
head of which stands that Acid, we find the sign of the Phlogiston
placed above that of the Fixed Alkali, as having a greater affinity
than the Fixed Alkali with the Vitriolic Acid. This is founded on the
famous experiment, wherein Vitriolated Tartar and Glauber's Salt are
decompounded by means of the Phlogiston, which separates the Fixed
Alkalis of these Neutral Salts, and uniting with the Vitriolic Acid
contained in them forms therewith a Sulphur.

Secondly, Nitre deflagrates, and is decomposed, by the contact of any
inflammable matter whatever that is actually ignited; and the operation
which produces Phosphorus is no other than a decomposition of sea-salt,
whose Acid quits its Alkaline basis to join with the Phlogiston: now
these facts furnish very strong reasons for believing that both these
Acids, as well as the Vitriolic, have a stronger affinity with the
Phlogiston than with a Fixed Alkali. Lastly, as several experiments
shew the Vegetable Acids to be only the Mineral Acids disguised and
mortified, there are sufficient grounds for suspecting that Acids in
general have a greater affinity with the Phlogiston than with Fixed
Alkalis: so that instead of making an exception with regard to the
Vitriolic Acid, it would perhaps be better to lay down this greater
affinity as common to all Acids whatever, and to place the Phlogiston
in the first column, immediately under the character which denotes an
Acid in general. This theory, however, stands in need of confirmation
from other experiments[4].

  [4] Mr. Margraaf, an able German Chymist, has made several
  experiments, which induce him to think that the Acid of Phosphorus
  is of a particular kind, and different from that of sea-salt. May it
  not be the Marine Acid, but altered by the union it has contracted
  with the Phlogiston? Or may it not be, with respect to Phosphorus,
  what the volatile sulphureous spirit is, with respect to Sulphur?
  See the Memoirs of the Royal Academy of Sciences of Berlin.

Thirdly, in this same column the character of a Volatile Alkali is set
above that of an Absorbent Earth, as having a greater affinity with
Acids; and yet these Absorbent Earths decompose the Ammoniacal salts,
drive away the Volatile Alkali from the Acids, and assume its place.
This is one of the first objections made against Mr. Geoffroy's Table.
His answer thereto is printed in the Memoirs of the Academy of Sciences
for 1718, where his Table also is to be found. We have already declared
our opinion about this matter in treating of a Volatile Alkali.

Fourthly, in 1744, Mr. Geoffroy, brother to the author of the Table,
who hath done no less honour to Chymistry than that eminent physician,
gave in a Memoir containing an exception to the last affinity in the
first column; namely, that which places Absorbent Earths above Metallic
substances. He therein shews, that Alum may be converted into Copperas
by boiling it in iron vessels; that, on this occasion, the iron
precipitates the Earth of the Alum, separates it from its Acid, and
assumes its place; so that of course it must have a greater affinity,
than the Absorbent Earth of Alum, with the Vitriolic Acid.

At the head of the second column stands the character of the Marine
Acid, which signifies that the affinities of this Acid are the subject
of the column. Immediately below it is placed the mark of Tin. As this
is a metalline substance, and as the first column places metalline
substances in the lowest degree of affinity with all Acids, it is
plain we must suppose Fixed Alkalis, Volatile Alkalis, and Absorbent
Earths, to be placed here in order after the Marine Acid, and before
Tin. Tin, then, is of all Metalline substances that which has the
greatest affinity with the Marine Acid; and then follow Regulus of
Antimony, Copper, Silver, Mercury. Gold comes last of all; and there
are no less than two vacant places above it. By this means it is in
some sort excluded from the rank of substances that have an affinity
with the Marine Acid. The reason thereof is, that this Acid alone is
not capable of dissolving Gold and combining therewith, necessarily
requiring for that purpose the aid of the Nitrous Acid, or at least of
the Phlogiston.

The third column exhibits the affinities of the Nitrous Acid, the
character whereof stands at its head. Immediately below it is the sign
of Iron, as the metal which has the greatest affinity with this Acid;
and then follow other metals, each according to the degree of its
relation; to wit, Copper, Lead, Mercury, and Silver. In this column,
as in the preceding one, we must suppose the substances, which in the
first column stand above Metallic substances, to be placed in their
proper order before Iron.

The fourth column is intended to represent the Affinities of the
Vitriolic Acid. Here Mr. Geoffroy has placed the Phlogiston as the
substance which has the greatest affinity with this Acid, for the
reason given in our explanation of the first column. Below it he has
ranked Fixed Alkalis, Volatile Alkalis, and Absorbent Earths, to
shew that this is an exception to the first column. As to Metalline
substances, he has set down but three, being those with which the
Vitriolic Acid has the most perceptible affinity: these metals, placed
in the order of their affinities, are Iron, Copper, and Silver.

The fifth column shews the affinities of Absorbent Earths. As these
Earths have no sensible affinity but with Acids, this column contains
only the characters of the Acids ranked according to the degree of
their strength, or affinity with the Earths; to wit, the Vitriolic, the
Nitrous, and the Marine Acids. Underneath this last might be placed the
Acid of Vinegar, or the Vegetable Acid.

The sixth column expresses the Affinities of Fixed Alkalis with Acids,
which are the same with those of Absorbent Earths. Moreover, we find
Sulphur placed here below all the Acids; because Liver of Sulphur,
which is a combination of Sulphur with a Fixed Alkali, is actually
decompounded by any Acid: for any Acid precipitates the Sulphur and
unites with the Alkali.

Immediately over the Sulphur, or in the same square with it, might be
set a mark denoting the Volatile Sulphureous Spirit; because, like
Sulphur, it has less affinity than any other Acid with Fixed Alkalis.
Oils might also be ranked with Sulphur, because they unite with Fixed
Alkalis, and therewith form Soaps, which are decompounded by any acid
whatever.

The seventh column points out the affinities of Volatile Alkalis, which
are likewise the same as those of Absorbent Earths; and the Vegetable
Acid might be placed here also under the Marine Acid.

The eighth column specifies the affinities of Metallic substances
with Acids. The affinities of the Acids, which, with respect to Fixed
Alkalis, Volatile Alkalis, and Absorbent Earths, succeeded each other
uniformly, do not appear in the same order here. The Marine Acid,
instead of being placed below the Vitriolic and Nitrous Acids, stands,
on the contrary, at their head; because, in fact, this Acid separates
Metalline substances from all the other Acids with which they happen
to be united, and, forcing these Acids to quit possession, intrudes
into their place. Nevertheless, this is not a general rule; for several
Metalline substances must be excepted, particularly Iron and Copper.

The ninth column declares the affinities of Sulphur. Fixed Alkalis,
Iron, Copper, Lead, Silver, Regulus of Antimony, Mercury, and Gold,
stand below it in the order of their affinities. With regard to Gold it
must be observed, that it will not unite with pure Sulphur: it suffers
itself to be dissolved only by the Liver of Sulphur, which is known to
be a composition of Sulphur and Fixed Alkali.

At the head of the tenth column appears Mercury, and beneath it several
Metalline substances, in the order of their affinities with it. Those
Metalline substances are Gold, Silver, Lead, Copper, Zinc, and Regulus
of Antimony.

It is proper to remark on this column, that Regulus of Antimony,
which stands the lowest, unites but very imperfectly with Mercury;
and that after a seeming union of these two Metallic substances hath
been obtained, by a tedious triture with the addition of water, they
do not continue long united, but spontaneously separate from each
other in a short time. Iron and Tin are here excluded; the former
with great reason, because hitherto it hath not been clearly proved,
by any known experiment, that ever Mercury was united with Iron: but
the same objection cannot be made to Tin, which amalgamates very well
with Mercury, and might therefore be placed in this column nearly
between Lead and Copper. I use the word _nearly_, because the different
degrees of affinity between Metalline substances and Mercury are not so
exactly determined, as the other relations before considered; seeing
they generally unite with it, without excluding one another. We can
therefore scarce judge of the degree of affinity that belongs to each,
but by the greater or less readiness of each to amalgamate therewith.

The eleventh column shews, that Lead has a greater affinity with Silver
than with Copper.

The twelfth, that Copper has a greater affinity with Mercury than with
Calamine.

The thirteenth, that Silver has a greater affinity with Lead than with
Copper.

The fourteenth contains the affinities of Iron. Regulus of Antimony
stands immediately underneath it, as being the Metallic substance which
has the greatest affinity with it. Silver, Copper, and Lead, are placed
together in the next square below, because the degrees of affinity
which those metals have with Iron are not exactly determined.

The same is to be said of the fifteenth column: Regulus of Antimony
stands at its head; Iron is immediately below it; and below the Iron
the same three metals occupy one square as before.

Lastly, the sixteenth column indicates that Water has a greater
affinity with Spirit of Wine than with Salts. By this general
expression must not be understood any Saline substance whatever; but
only the Neutral Salts, which Spirit of Wine frees from the water that
kept them in solution. Fixed Alkalis, on the contrary, as well as the
Mineral Acids, have a greater affinity than Spirit of Wine with water:
so that these Saline substances, being well dephlegmated, and mixed
with Spirit of Wine; imbibe the water it contains and rectify it.

To these might be added another short column, having Spirit of Wine at
its head: immediately below it should be the character of Water, and
below that the mark of Oil. This column would shew that the Spirit of
Wine has a greater affinity with Water than with Oils; because any Oily
matter whatever, that is dissolved in Spirit of Wine, may be actually
separated from it by the affusion of Water. This rule admits of no
exception but in one case; which is when the oily substance partakes
of the nature of soap, by having contracted an union with some saline
matter. But as this must be imputed wholly to that adventitious saline
matter being superadded to the oily substance, it is no just foundation
for an exception, and the affinity in question is nevertheless general.

We have now delivered every thing material that we had to say
concerning Mr. Geoffroy's Table of Affinities. It is, as we observed
before, of exceeding great service, as it collects into one view
the principal truths laid down in this Treatise. Indeed the most
advantageous way of using it is, not to delay consulting it till you
have read the book through, but to turn to it while you are reading, as
oft as any affinity between bodies is treated of; which it will imprint
more strongly on your mind, by representing it in a manner before your
eyes.



CHAP. XVIII.

_The_ THEORY _of_ CONSTRUCTING _the_ VESSELS _most commonly used in_
CHYMISTRY.


Chymists cannot perform the operations of their art without the help of
a considerable number of vessels, instruments, and furnaces, adapted
to contain the bodies on which they intend to work, and to apply to
them the several degrees of heat required by different processes. It is
therefore proper, before we advance to the operations themselves, to
consider particularly and minutely what relates to the instruments with
which they are to be performed.

Vessels intended for Chymical Operations should, to be perfect, be
able to bear, without breaking, the sudden application of great heat
and great cold; be impenetrable to every thing, and unalterable by any
solvent; unvitrifiable, and capable of enduring the most violent fire
without melting: but hitherto no vessels have been found with all these
qualities united.

They are made of sundry materials; namely, of metal, of glass, and of
earth. Metalline vessels, especially those made of Iron or Copper,
are apt to be corroded by almost every saline, oily, or even aqueous
substance. For this reason, in order to render the use of them a little
more extensive, they are tinned on the inside. But, notwithstanding
this precaution, they are on many occasions not to be trusted; and
should never be employed in any nice operations which require great
accuracy: they are, moreover, incapable of resisting the force of fire.

Earthen vessels are of several sorts. Some, that are made of a
refractory earth, are capable of being suddenly exposed to a strong
fire without breaking, and even of sustaining a great degree of heat
for a considerable time: but they generally suffer the vapours of
the matters which they contain, as well as vitrified metals, to pass
through them, especially the glass of lead, which easily penetrates
them and runs through their pores as through a sieve. There are others
made of an earth that, when well baked, looks as if it were half
vitrified: these being much less porous, are capable of retaining the
vapours of the matters which they contain, and even glass of lead in
fusion; which is one of the severest trials a vessel can be put to: but
then they are more brittle than the other sort.

Good glass vessels should constantly be employed in preference to all
others, whenever they can possibly be used: and that not only because
they are no way injured by the most active solvents, nor suffer any
part of what they contain to pass through, but also because their
transparency allows the Chymist to observe what passes within them:
which is always both curious and useful. But it is pity that vessels of
this sort should not be able to endure a fierce fire without melting.
We shall take care, when we come to describe the several sorts of
chymical instruments, and the manner of using them, to note what
vessels are to be preferred to others on different occasions.

Distillation, as hath been already said, is an operation by which
we separate from a body, by the help of a gradual heat, the several
principles of which it consists.

There are three methods of distilling. The first is performed by
applying the heat over the body whose principles are to be extracted.
In this case, as the liquors, when heated and converted into vapours,
constantly endeavour to fly from the center of heat, they are forced to
re-unite in the lower part of the vessel, that contains the matter in
distillation, and so passing through the pores or holes of that vessel,
they fall into another cold vessel applied underneath to receive them.
This way of distilling is on this account called distilling _per
Descensum_. It requires no other apparatus than two vessels figured
like segments of hollow spheres, whereof that which is pierced with
little holes, and intended to contain the matter to be distilled,
should be much less than the other, which is to contain the fire,
and to fill its aperture exactly; the whole together to be supported
vertically upon a third vessel, which is to serve the purpose of a
recipient, admitting into its mouth the convex bottom of the vessel
containing the matter to be distilled, which must accurately fill it.
This method of distilling is but little used.

The second method of distilling is performed by applying the heat
underneath the matter to be decomposed. On this occasion the liquors
being heated, rarefied, and converted into vapours, rise, and are
condensed in a vessel contrived for that purpose, which we shall
presently describe. This way of distilling is called distilling _per
Ascensum_, and is much used.

The vessel in which this distillation _per Ascensum_ is performed we
call an _Alembic_.

There are several sorts thereof, differing from one another both in the
matter of which, and the manner in which, they are made.

Those employed to draw the odoriferous waters and essential oils of
plants are generally made of copper, and consist of several pieces. The
first, which is designed to contain the plant, is formed nearly like a
hollow cone, the vertex whereof is drawn out in the shape of a hollow
cylinder or tube: this part is named the _Cucurbit_, and its tube the
_Neck_ of the _Alembic_. To the upper end of this tube another vessel
is soldered: this is called the _Head_, and commonly has likewise the
form of a cone, joined to the neck of the alembic by its base, round
which, on the inside, is hollowed a small groove, communicating with
an orifice that opens at its most depending part. To this orifice is
soldered a small pipe in a direction sloping downwards, which is called
the _Nose_, _Spout_, or _Beak_ of the alembic.

As soon as the matters contained in the alembic grow hot, vapours begin
to arise from them, and ascending through the neck of the alembic into
the head, are by the sides thereof stopped and condensed: from thence
they trickle down in little streams to the groove, which conveys them
to the spout; and by that they pass out of the alembic into a glass
vessel with a long neck, the end of the spout being introduced into
that neck, and luted thereto.

To facilitate the refrigeration and condensation of the vapours
circulating in the head, all alembics of metal are moreover provided
with another piece, which is a kind of large pan of the same metal,
fitted and soldered round the head. This piece serves to keep cold
water in, which incessantly cools the head, and therefore it is called
the _Refrigeratory_. The water in the refrigeratory itself grows hot
after some time, and must therefore be changed occasionally; the heated
water being first drawn off by means of a cock fixed near the bottom of
the refrigeratory. All copper alembics should be tinned on the inside
for the reasons already given.

When saline spirits are to be distilled, alembics of metal must not
be used; because the saline vapours would corrode them. In this case
recourse must be had to alembics of glass. These consist of two pieces
only; namely, a _Cucurbit_, whose superior orifice is admitted into and
exactly luted with its _Head_, which is the second piece.

In general, as alembics require that the vapours of the matter to be
distilled should rise to a considerable heighth, they ought to be used
only when the most volatile principles are to be drawn from bodies:
and the lighter and more volatile the substances to be separated by
distillation are, the taller must the alembic be; because the most
ponderous parts, being unable to rise above a certain heighth, fall
back again into the cucurbit as soon as they arrive there, leaving the
lighter to mount alone, whose volatility qualifies them to ascend into
the head.

When a matter is to be distilled, that requires a very tall alembic,
and yet does not admit of a metalline vessel, the end will be best
answered by a glass vessel of a round or oval shape, having a very
long neck, with a small head fitted to its extremity. Such a vessel
serves many purposes: it is sometimes employed as a receiver, and at
other times as a digesting vessel; on which last occasion it goes under
the name of a _Matrass_. When one of these, provided with a head, is
applied to the purpose of distilling, it forms a sort of alembic.

There are some alembics of glass, blown in such a manner by the
workmen, that the body and head form but one continued piece. As these
alembics do not stand in need of having their several pieces luted
together, they are very useful on some occasions, when such exceeding
subtile vapours rise as are capable of transpiring through lutes. The
head must have an aperture at the top, provided with a short tube,
through which, by means of a funnel with a long pipe, the matter to be
distilled may be introduced into the cucurbit. This is to be exactly
closed with a glass stopple, the surface whereof must be made to fit
the inside of the tube in every point, by rubbing those two pieces
well together with emery.

Another sort of alembic hath also been invented, which may be used
with advantage when _Cohobation_ is required; that is, when the liquor
obtained by distillation is to be returned upon the matter in the
cucurbit; and especially when it is intended that this cohobation
shall be repeated a great number of times. The vessel we are speaking
of is constructed exactly in the same manner as that last described;
except that its beak, instead of being in a straight line, as in the
other alembics, forms a circular arch, and re-enters the cavity of the
cucurbit, in order to convey back again the liquor collected in the
head. This instrument hath commonly two beaks opposite to each other,
both turned in this manner, and is called a _Pelican_: it saves the
artist the trouble of frequently unluting and reluting his vessels, as
well as the loss of a great many vapours.

There are certain substances which in distillation afford matters in
a concrete form, or rise wholly in the form of a very light powder,
called _Flowers_. When such substances are to be distilled, the
cucurbit which contains them is covered with a head without a nose,
which is named a _Blind-head_.

When the flowers rise in great quantities and very high, a number of
heads is employed to collect them; or rather a number of a kind of
pots, consisting of a body only without any bottom, which fitting one
into the other form a canal, that may be lengthened or shortened at
pleasure, according as the flowers to be sublimed are more or less
volatile. The last of the heads, which terminates the canal, is quite
close at one end, and makes a true blind-head. These vessels are called
_Aludels_; they are usually of earthen or stone ware.

All the vessels above-mentioned are fit only for distilling such light
volatile matters as can be easily raised and brought over; such as
phlegm, essential oils, fragrant waters, acid oily spirits, volatile
alkalis, _&c._ But when the point is to procure by distillation
principles that are much less volatile, and incapable of rising high,
such as the thick fetid oils, the vitriolic, the nitrous, and the
marine acids, _&c._ we are under a necessity of having recourse to
other vessels, and another manner of distilling.

It is easy to imagine, that such a vessel must be much lower than
the alembic. It is indeed no more than a hollow globe, whose upper
part degenerates into a neck or tube, that is bent into a horizontal
position; for which reason this instrument is called a _Retort_: it is
always of one single piece.

The matter to be distilled is introduced into the body of the retort by
means of a ladle with a long tubular shank. Then it is set in a furnace
built purposely for this use, and so that the neck of the retort coming
out of the furnace may, like the nose of the alembic, stand in a
sloping position, to facilitate the egress of the liquors, which by its
means are conveyed to a receiver, into which it is introduced, and with
which it is luted. This way of distilling, in which the vapours seem
rather to be driven out of the vessel horizontally and laterally, than
raised up and sublimed, is for that reason called Distillation _per
Latus_.

Retorts are, of all the instruments of distillation, those that must
sustain the greatest heat, and resist the strongest solvents; and
therefore they must not be made of metal. Some, however, which are
made of iron may do well enough on certain occasions: the rest are
either of glass or earth. Those of glass, for the reasons above given,
are preferable to the other sort, in all cases where they are not to
be exposed to such a force of fire as may melt them. The best glass,
that which stands both heat and solvents best, is that in which there
are fewest alkaline salts. Of this sort is the green German glass: the
beautiful white crystal glass is far from being equally serviceable.

Retorts, as well as alembics, may be of different forms. For example,
some matters are apt to swell, and rise over the neck of the retort in
substance, without suffering any decomposition; when such matters are
to be distilled in a retort, it is proper that the body of the vessel,
instead of being globular, be drawn out into the form of a pear, so as
nearly to resemble that of a cucurbit. In a retort of this kind, the
distance between the bottom and the neck being much greater than in
those whose bodies are spherical, the matters contained have much more
room for expansion; so that the inconvenience here mentioned is thereby
prevented. Retorts of this form are called English retorts. As they
hold the middle place between alembics and common retorts, they may be
used to distil such matters as have a mean degree of volatility between
the greatest and the least.

It is moreover proper to have, in a laboratory, sundry retorts with
necks of different diameters. Wide necks will be found the fittest
for conveying thick matters, and such as readily become fixed; for
instance, some very thick fetid oils, butter of antimony, _&c._; for
as these matters acquire a consistence as soon as they are out of
the reach of a certain degree of heat, they would soon choak a narrow
neck, and by stopping the vapours which rise at the same time from the
retort, might occasion the bursting of the vessels.

Some retorts are also made with an opening on their upper side, like
that of tubulated glass alembics, which is to be closed in the same
manner with a glass stopple. These retorts are also called Tubulated
retorts, and ought always to be used whenever it is necessary to
introduce fresh matter into the retort during the operation; seeing it
may be done by means of this invention, without unluting and reluting
the vessels; which ought always to be avoided as much as possible.

One of the things that most perplexes the Chymists, is the prodigious
elasticity of many different vapours, which are frequently discharged
with impetuosity during the distillation, and are even capable of
bursting the vessels with explosion, and with danger to the artist. On
such occasions it is absolutely necessary to give these vapours vent,
as we shall direct in its proper place: but as that can never be done
without losing a great many of them; as some of them in particular
are so elastic that scarce any at all would remain in the vessel; for
instance, those of the spirit of nitre, and especially those of the
smoking spirit of salt; the practice is to make use of very large
receivers, of about eighteen or twenty inches diameter, that the
vapours may have sufficient room to circulate in, and by applying to
the wide surface presented them by the extensive inside of such a large
vessel, may be condensed into drops. These huge receivers are commonly
in the form of hollow globes, and are called Ballons.

To give these vapours still more room, ballons have been contrived
with two open gullets in each, diametrically opposite to one another;
whereof one admits the neck of the retort, and the other is received by
one of the gullets of a second ballon of the same form, which is joined
in like manner to a third, and so on. By this artifice the space may be
enlarged at pleasure. These ballons with two necks are called Adopters.

Operations on bodies that are absolutely fixed, as metals, stones,
sand, _&c._ require only such vessels as are capable of containing
those bodies, and resisting the force of fire. These vessels are little
hollow pots, of different dimensions, which are called Crucibles.
Crucibles can hardly be made of any thing but earth; they ought to have
a cover of the same material fitted to shut them close. The best earth
we know is that whereof those pots are made in which butter is brought
from Bretagne: these pots themselves are exceeding good crucibles; and
they are almost the only ones that are capable of holding glass of lead
in fusion, without being penetrated by it.

For the roasting of ores, that is, freeing them, by the help of fire,
from their sulphureous and arsenical parts, little cups of the same
material with crucibles are used; but they are made flat, shallow,
and wider, above than below, that these volatile matters may the more
freely exhale. These vessels are called Tests, or Scorifiers: they are
scarce ever used but in the Docimastic art, that is, in making small
Assays of ores.



CHAP. XIX.

_The_ THEORY _of_ CONSTRUCTING _the_ FURNACES _most commonly used in_
CHYMISTRY.


Skill in conducting and applying fire properly, and determining its
different degrees, is of very great consequence to the success of
Chymical operations.

As it is exceeding difficult to govern and moderate the action of fire,
when the vessels in which any operation is performed are immediately
exposed to it, Chymists have contrived to convey heat to their vessels,
in nice operations, through different mediums, which they place
occasionally between those vessels and the fire.

Those intermediate substances in which they plunge their vessels are
called Baths. They are either fluid or solid: the fluid baths are water
or its vapours. When the distilling vessel is set in water, the bath is
called _Balneum Mariæ_, or the _Water Bath_; and the greatest degree
of heat of which it is susceptible is that of boiling water. When the
vessel is exposed only to the vapours which exhale from water, this
forms the _Vapour Bath_; the heat of which is nearly the same with
that of the _Balneum Mariæ_. These baths are useful for distilling
essential oils, ardent spirits, sweet-scented waters; in a word, all
such substances as cannot bear a greater heat, without prejudice either
to their odour, or to some of their other qualities.

Baths may also be made of any other fluids, such as oils, mercury,
_&c._ which are capable of receiving and communicating much more heat:
but they are very seldom used. When a more considerable degree of
heat is required, a bath is prepared of any solid matter reduced to a
fine powder, such as sand, ashes, filings of iron, _&c._ The heat of
these baths may be pushed so far as to make the bottom of the vessel
become faintly red. By plunging a thermometer into the bath, by the
side of the vessel, it is easy to observe the precise degree of heat
applied to the substance on which you are working. It is necessary
that the thermometers employed on this occasion be constructed on good
principles, and so contrived as to be easily compared with those of the
most celebrated natural philosophers. Those of the illustrious Réaumur
are most used and best known, so that it would not be amiss to give
them the preference. When a greater heat is required than any of those
baths can give, the vessels must be set immediately on live coals, or
in a flaming fire: this is called working with a naked fire; and, in
this case it is much more difficult than in the other to determine the
degrees of heat.

There are several ways of applying a naked fire. When the heat or flame
is reflected upon the upper part of a vessel which is exposed to the
fire, this is called a Reverberated heat. A Melting heat is that which
is strong enough to fuse most bodies. A Forging heat is that of a fire
which is forcibly excited by the constant blast of a pair of bellows,
or more.

There is also another sort of fire which serves very commodiously for
many operations, because it does not require to be fed or frequently
mended: this is afforded by a lamp with one or more wicks, and may be
called a Lamp-heat. It is scarce ever employed but to heat baths, in
operations which require a gentle and long continued warmth: if it hath
any fault, it is that of growing gradually hotter.

All the different ways of applying fire require Furnaces of different
constructions: we shall therefore describe such as are of principal and
most necessary use.

Furnaces must be divided into different parts or stories, each of which
has its particular use and name.

The lower part of the furnace, designed for receiving the ashes and
giving passage to the air, is called the Ash-hole. The ash-hole is
terminated above by a grate, the use of which is to support the coals
and wood, which are to be burnt thereon: this part is called the
Fire-place. The fire-place is in like manner terminated above by
several iron bars, which lie quite across it from right to left, in
lines parallel to each other: the use of these bars is to sustain the
vessels in which the operations are to be performed. The space above
these bars to the top of the furnace is the upper story, and may be
called the Laboratory of the furnace. Lastly, some furnaces are quite
covered above by means of a kind of vaulted roof called the Dome.

Furnaces have moreover several apertures: one of these is at the
ash-hole, which gives passage to the air, and through which the ashes
that fall through the grate are raked out; this aperture is called the
ash-hole Door: another is at the fire-place, through which the fire
is supplied with fuel, as occasion requires; this is called the mouth
or door of the Fire-place, or the Stoke-hole: there is a third in the
upper story, through which the neck of the vessel passes; and a fourth
in the dome for carrying off the fuliginosities of combustible matters,
which is called the Chimney.

To conclude, there are several other openings in the several parts of
the furnace, the use whereof is to admit the air into those places, and
also, as they can be easily shut, to incite or slacken the activity of
the fire, and so to regulate it; which has procured them the title of
Registers. All the other openings of the furnace should be made to shut
very close, the better to assist in governing the fire; by which means
they likewise do the office of registers.

In order to our forming a just and general idea of the construction of
furnaces, and of the disposition of the several apertures in them, with
a view to increase or diminish the activity of the fire, it will be
proper to lay down, as our ground-work, certain principles of natural
philosophy, the truth of which is demonstrated by experience.

And first, every body knows that combustible matters will not burn or
consume unless they have a free communication with the air; insomuch
that if they be deprived thereof, even when burning most rapidly, they
will be extinguished at once: that consequently combustion is greatly
promoted by the frequent accession of fresh air, and that a stream of
air, directed so as to pass with impetuosity through burning fuel,
excites the fire to the greatest possible activity.

Secondly, it is certain that the air which touches, or comes near
ignited bodies is heated, rarefied, and rendered lighter than the
air about it, that is, farther distant from the center of heat;
and consequently that this air, so heated and become lighter, is
necessarily determined thereby to ascend and mount aloft, in order
to make room for that which is less heated and not so light, which by
its weight and elasticity tends to occupy the place quitted by the
other. Another consequence hereof is, that if fire be kindled in a
place enclosed every where but above and below, a current of air will
be formed in that place, running in a direction from the bottom to the
top; so that if any light bodies be applied to the opening below, they
will be carried up towards the fire; but, on the contrary, if they be
held at the opening above, they will be impelled by a force which will
drive them up, and carry them away from the fire.

Thirdly and lastly, it is a truth demonstrated in hydraulics, that the
velocity of a given quantity of any fluid, determined to flow in any
direction whatever, is so much the greater the narrower the channel is
to which that fluid is confined; and consequently that the velocity
of a fluid will be increased by making it run from a wider through a
narrower passage.

These principles being established, it is easy to apply them to the
construction of furnaces. First, if a fire be kindled in the fire-place
of a furnace, which is open on all sides, it burns nearly as if it were
in the open air. It has with the surrounding air a free communication;
so that fresh air is continually admitted to facilitate the entire
combustion of the inflammable matters employed as fuel. But there being
nothing to determine that air to pass with rapidity through the fire in
this case, it does not at all augment the activity thereof, but suffers
it to waste away quietly.

Secondly, if the ash-hole or dome of a furnace, in which a fire
is burning, be shut quite close, then there is no longer any free
communication between the air and the fire: if the ash-hole be shut,
the air is debarred from having free access to the fire; if the dome
be stopt, the egress of the air rarefied by the fire is prevented; and
consequently the fire must in either case burn very faintly and slowly,
gradually die away, and at last go quite out.

Thirdly, if all the openings of the furnace be wholly closed, it is
evident that the fire will be very quickly extinguished.

Fourthly, if only the lateral openings of the fire-place be shut,
leaving the ash-hole and upper part of the furnace open; it is plain
that the air entering by the ash-hole will necessarily be determined
to go out at top, and that consequently a current of air will be
formed, which will pass through the fire, and make it burn briskly and
vigorously.

Fifthly, if both the ash-hole and the upper story of the furnace be
of some length, and form canals either cylindric or prismatic, then
the air being kept in the same direction through a longer space, the
course of its stream will be both stronger and better determined, and
consequently the fire will be more animated by it.

Sixthly and lastly, if the ash-hole and the upper part of the furnace,
instead of being cylindric or prismatic canals, have the form of
truncated cones or pyramids, standing on their bases, and so ordered
that the upper opening of the ash-hole, adjoining to the fire-place,
may be wider than the base of the superiour cone or pyramid, then the
stream of air, being forced to pass incessantly from a larger channel
through a smaller, must be considerably accelerated, and procure to
the fire the greatest activity which it can receive from the make of a
furnace.

The materials fittest for building furnaces are, 1. Bricks, joined
together with potters clay mixed with sand and moistened with water. 2.
Potters clay mingled with potsherds, moistened with water, and baked in
a violent fire. 3. Iron; of which all furnaces may be made, with this
precaution, that the inside be provided with a great many prominent
points, as fastenings for a coat of earth, with which the internal
parts of the furnace must necessarily be covered to defend it from the
action of the fire.

The reverberating furnace is one of those that are most employed in
Chymistry: it is proper for distillations by the retort, and should be
constructed in the following manner.

First, the use of the ash-hole being, as was said, to give passage
to the air and to receive the ashes, no bad consequence can attend
its being made pretty high: it may have from twelve to twenty or
twenty-four inches in heighth. Its aperture should be wide enough to
admit billets of wood, when a great fire is to be made.

Secondly, the ash-hole must be terminated at its upper part by an
iron grate, the bars of which should be very substantial, that they
may resist the action of the fire: this grate is the bottom of the
fire-place, and destined to support the coals. In the lateral part of
the fire-place, and nearly about the same heighth with the grate, there
should be a hole of such a size that it may easily admit charcoal, as
well as little tongs and shovels for managing the fire. This aperture
or mouth of the fire-place should be perpendicularly over the mouth of
the ash-hole.

Thirdly, from six to eight or ten inches high above the grate over the
ash-hole, little apertures must be made in the walls of the furnace,
of eight or ten lines in diameter, an inch from one another, and those
in one side must be diametrically opposite to those in the other. The
use of these holes is to receive bars of iron for the retort to rest
on; which should be, as I said, at different heights, in order to
accommodate retorts of different sizes. At the upper extremity of this
part of the furnace, which reaches from the iron bars to the top, the
heighth whereof should be somewhat less than the width of the furnace,
must be cut a semi-circular aperture for the neck of the retort to come
through. This hole must by no means be over the doors of the fire-place
and ash-hole; for then, as it gives passage to the neck of the retort,
it must of course be opposite to the receiver, and in that case the
receiver itself would stand over against those two apertures; which
would be attended with this double inconvenience, that the receiver
would not only grow very hot, but greatly embarrass the operator, whose
free access to the fire-place and ash-hole would be thereby obstructed.
It is proper therefore that the semi-circular cut we are speaking of be
so placed that when the greatest ballons are luted to the retort they
may leave an open passage to the fire-place and ash-hole.

Fourthly, in order to cover in the laboratory of the reverberating
furnace, there must be a roof made for it in the form of a cupola,
or concave hemisphere, having the same diameter as the furnace. This
dome should have a semi-circular cut in its rim, answering to that
above-directed to be made in the upper extremity of the furnace,
so that, when adjusted to each other, the two together may form a
circular hole for the neck of the retort to pass through. At the top of
this dome there must also be a circular hole of three or four inches
diameter, carrying a short tapering funnel of the same diameter, and
three inches high, which will serve for a chimney to carry off all
fuliginosities, and accelerate the current of the air. This passage may
be shut at pleasure with a flat cover. Moreover, as it is necessary
that the dome should be taken off and put on with ease, it should have
two ears or handles for that purpose: a portative or moveable furnace
should also have a pair of handles, fixed opposite to each other,
between the ash-hole and the fire-place.

Sixthly and lastly, a conical canal must be provided of about three
feet long, and sufficiently wide at its lower end to admit the funnel
of the aperture at the top of the dome. This conical tube is to be
applied to the dome when the fire is required to be extremely active:
it tapers gradually from its base upwards, and breaks off as if
truncated at top, where it should be about two inches wide.

Besides the apertures already mentioned as necessary to a reverberating
furnace, there must also be many other smaller holes made in its
ash-hole, fire-place, laboratory, and dome, which must all be so
contrived as to be easily opened and shut with stopples of earth: these
holes are the registers of the furnace, and serve to regulate the
activity of the fire, according to the principles before laid down.

When the action of the fire is required to be exactly uniform and very
brisk, it is necessary to stop carefully with moist earth all the
little chinks in the juncture of the dome with the furnace, between the
neck of the retort and the circular hole through which it passes, and
which it never fills exactly, and, lastly, the holes which receive the
iron bars that sustain the retort.

It is proper to have, in a laboratory, several reverberating furnaces
of different magnitudes; because, they must be proportioned to the size
of the retorts employed. The retort ought to fill the furnace, so as
to leave only the distance of an inch between it and the inside of the
furnace.

Yet when the retort is to be exposed to a most violent fire, and
especially when it is required that the heat shall act with equal force
on all parts of the furnace, and as strongly on its vault as on its
bottom, a greater distance must be left between the retort and the
inside of the furnace; for then the furnace may be filled with coals,
even to the upper part of the dome. If moreover some pieces of wood be
put into the ash-hole, the conical canal fitted on to the funnel of the
dome, and all the apertures of the furnace exactly closed, except the
ash-hole and the chimney, the greatest heat will then be excited that
this furnace can produce.

The furnace now described may also be employed in many other chymical
operations. If the dome be laid aside, an alembic may very well be
placed therein: but then the space, which will be left between the
body of the alembic and the top of the upper part of the furnace, must
be carefully filled up with Windsor-loam moistened; for without that
precaution the heat will soon reach the very head, which ought to be
kept as cool as possible, in order to promote the condensation of the
vapours. On this occasion therefore it will be proper to leave no holes
open in the fire-place, but the lateral ones; of which also those
over-against the receiver must be stopped.

A pot, or broad-brimmed earthen pan, may be placed over this furnace,
and being so fitted to it as to close the upper part thereof
accurately, and filled with sand, may serve for a sand-heat to distil
with.

The bars designed to support distilling vessels being taken out, a
crucible may stand therein, and many operations be performed that do
not require the utmost violence of fire. In a word, this furnace is one
of the most commodious that can be, and more extensively useful than
any other.

The Melting furnace is designed for applying the greatest force of
heat to the most fixed bodies, such as metals and earths. It is never
employed in distilling: it is of no use but for calcination and fusion;
and consequently need not admit any vessels but crucibles.

The ash-hole of this furnace differs from that of the reverberating
furnace only in this, that it must be higher, in order to raise the
fire-place to a level with the artist's hand; because in that all
the operations of this furnace are performed. The ash-hole therefore
must be about three feet high: and this heighth procures it moreover
the advantage of a good draught of air. For the same reason, and in
consequence of the principles we laid down, it should be so built that
its width lessening insensibly from the bottom to the top, it may be
narrower where it opens into the fire-place than any where below.

The ash-hole is terminated at its upper end, like that of the
reverberating furnace, by a grate, which serves for the bottom of
the fire-place, and ought to be very substantial, that it may resist
the violence of the fire. The inside of this furnace is commonly an
elliptic curve; because it is demonstrated by mathematicians that
surfaces having that curvature reflect the rays of the sun, or of fire,
in such a manner, that meeting in a point, or a line, they produce
there a violent heat. But, to answer this purpose, those surfaces must
be finely polished; an advantage hardly procurable to the internal
surface of this furnace, which can be made of nothing but earth:
besides, if it were possible to give it a polish, the violent action of
the fire that must be employed in this furnace would presently destroy
it. Yet the elliptical figure must not be entirely disregarded: for,
if care be taken to keep the internal surface of the furnace as smooth
as possible, it will certainly reflect the heat pretty strongly, and
collect it about the center.

The fire-place of this furnace ought to have but four apertures.

First, that of the lower grate, which communicates with the ash-hole.

Secondly, a door in its fore-side, through which may be introduced
coals, crucibles, and tongs for managing them: this aperture should be
made to shut exactly with a plate of iron, having its inside coated
with earth, and turning on two hinges fixed to the furnace.

Thirdly, over this door a hole slanting downwards, towards the place
where the crucible is to stand. The use of this hole is to give the
operator an opportunity of examining the condition of the matters
contained in his crucible without opening the door of the fire-place:
this hole should be made to open and shut easily, by means of a stopple
of earth.

Fourthly, a circular aperture of about three inches wide in the upper
part or vault of the furnace, which should gradually lessen and
terminate, like that of the dome of the reverberating furnace, in a
short conical funnel of about three inches long, and fitted to enter
the conical pipe before described, which is applied when the activity
of the fire is to be increased.

When this furnace is to be used, and a crucible to be placed in it,
care must be taken to set on the grate a cake of baked earth, somewhat
broader than the foot of the crucible. The use of this stand is to
support the crucible, and raise it above the grate, for which purpose
it should be two inches thick. Were it not for this precaution the
bottom of the crucible, which would stand immediately on the grate,
could never be thoroughly heated, because it would be always exposed to
the stream of cold air which enters by the ash-hole. Care should also
be taken to heat this earthen bottom red-hot before it be placed in the
furnace, in order to free it from any humidity, which might otherwise
happen to be driven against the crucible during the operation, and
occasion its breaking.

We omitted to take notice, in speaking of the ash-hole, that, besides
its door, it should have about the middle of its heighth a small hole,
capable of receiving the nosel of a good perpetual bellows, which is
to be introduced into it and worked, after the door is exactly shut,
when it is thought proper to excite the activity of the fire to the
utmost violence. The Forge is only a mass of bricks of about three
feet high, along whose upper surface is directed the nose or pipe of a
pair of large perpetual bellows, so placed that the operator may easily
blow the fire with one hand. The coals are laid on the hearth of the
forge near the nose of the bellows; they are confined, if necessary,
to prevent their being carried away by the wind of the bellows, within
a space inclosed by bricks; and then by pulling the bellows the fire
is continually kept up in its greatest activity. The forge is of use
when there is occasion to apply a great degree of heat suddenly to any
substance, or when it is necessary that the operator be at liberty to
handle frequently the matters which he proposes to fuse or calcine.

The Cupelling furnace is that in which gold and silver are purified, by
the means of lead, from all alloy of other metallic substances. This
furnace must give a heat strong enough to vitrify lead, and therewith
all the alloy which the perfect metals may contain. This furnace is to
be built in the following manner.

First, of thick iron plates, or of some such composition of earth as we
recommended for the construction of furnaces, must be formed a hollow
quadrangular prism, whose sides may be about a foot broad, and from ten
to eleven inches high; and extending from thence upwards may converge
towards the top, so as to form a pyramid truncated at the heighth of
seven or eight inches, and terminated by an aperture of the width
of seven or eight inches every way. The lower part of the prism is
terminated, and closed, by a plate of the same materials of which the
furnace is constructed.

Secondly, in the fore-side or front of this prism there is an opening
of three or four inches in heighth, by five or six inches in breadth:
this opening, which should be very near the bottom, is the door of the
ash-hole. Immediately over this opening is placed an iron grate, the
bars of which are quadrangular prisms of half an inch square, laid
parallel to each other, and about eight or nine inches asunder, and
so disposed that two of their angles are laterally opposite, the two
others looking one directly upwards and the other downwards. As in this
situation the bars of the grate present to the fire-place very oblique
surfaces, the ashes and very small coals do not accumulate between
them, or hinder the free entrance of the air from the ash-hole. This
grate terminates the ash-hole at its upper part, and serves for the
bottom of the fire-place.

Thirdly, three inches, or three and a half, above the grate, there is
in the fore-side of the furnace another opening, terminated by an arch
for its upper part, which consequently has the figure of a semi-circle:
it ought to be four inches wide at bottom, and three inches and an half
high at its middle. This opening is the door of the fire-place; yet
it is not intended for the same uses as the door of the fire-place in
other furnaces: the purpose for which it is actually destined shall
be explained when we come to shew how the furnace is to be used. An
inch above the door of the fire-place, still in the fore-side of the
furnace, are two holes of about an inch diameter, and at the distance
of three inches and a half from each other, to which answer two other
holes of the same size, made in the hinder part, directly opposite to
these. There is, moreover, a fifth hole of the same width about an inch
above the door of the fire-place. The design of all these holes shall
be explained when we describe the manner in which these furnaces are to
be used.

Fourthly, the fore-part of the furnace is bound by three iron braces,
one of which is fixed just below the door of the ash-hole; the second
occupies the whole space between the ash-hole door and the door of
the fire-place, and has two holes in it, answering to those which we
directed to be made in the furnace itself about this place; and the
third is placed immediately over the door of the fire-place. These
braces must extend from one corner of the front of the furnace to the
other, and be fastened thereto with iron pins, in such a manner that
their sides next to the doors may not lie quite close to the body of
the furnace, but form a kind of grooves for the iron plates to slide
in, that are designed to shut the two doors of the furnace when it is
necessary. Each of these iron plates should have a handle, by which it
may be conveniently moved; and to each door there should be two plates,
which meeting each other, and joining exactly in the middle of the
door-place, may shut it very close. Each of the two plates belonging
to the door of the fire-place ought to have a hole in its upper part;
one of these holes should be a slit of about two lines wide, and half
an inch long; the other may be a semi-circular opening of one inch
in heighth and two in breadth. These holes should be placed so that
neither of them may open into the fire-place when the two plates are
joined together in the middle of the door to shut it close.

Fifthly, to terminate the furnace above, there must be a pyramid formed
of the same materials with the furnace, hollow, quadrangular, three
inches high on a base of seven inches, which base must exactly fit
the upper opening of the furnace: the top of this pyramidal cover must
end in a tube of three inches in diameter and two in heighth, which
must be almost cylindrical, and yet a little inclining to the conical
form. This tube serves, as in the furnaces already described, to carry
the conical funnel, which is fitted to the upper part when a fire of
extraordinary activity is wanted.

The furnace thus constructed is fit to serve all the purposes for
which it is designed: yet before it can be used another piece must be
provided, which, though it does not properly belong to the furnace, is
nevertheless necessary in all the operations performed by it; and that
is a piece contrived to contain the cupels, or other vessels which are
to be exposed to the fire in this furnace. It is called a Muffle, and
is made in the following manner.

On an oblong square, of four inches in breadth, and six or seven in
length, a concave semi-cylinder is erected, in the form of a vault,
which makes a semi-circular canal, open at both ends. One of these
is almost entirely closed, except that near the bottom two small
semi-circular holes are left. In each of its sides likewise two such
holes are made, and the other end is left quite open.

The Muffle is intended to bear and communicate the fiercest heat; and
therefore it must be made thin, and of an earth that will resist the
violence of fire, such as that of which crucibles are made. The Muffle
being thus constructed, and then well baked, is fit for use.

When it is to be used it must be put into the furnace by the upper
opening, and set upon two iron bars, introduced through the holes
made for that purpose below the door of the fire-place. The Muffle
must be placed on these bars in the fire-place in such a manner that
its open end shall stand next to, and directly against the door of
the fire-place, and may be joined to it with lute. Then the cupels
are ranged in it, and the furnace is filled up, to the heighth of two
or three inches above the Muffle, with small coals not bigger than
a walnut, to the end that they may lie close round the Muffle, and
procure it an equal heat on every side. The chief use of the Muffle
is to prevent the coals and ashes from falling into the cupels, which
would be very prejudicial to the operations carrying on in them:
for the lead would not vitrify as it ought, because the immediate
contact of the coals would continually restore its phlogiston; or
else the glass of lead, which ought to penetrate and pass through the
cupels, would be rendered incapable of so doing; because the ashes
mixing therewith would give it such a consistence and tenacity as
would destroy that property, or at least considerably lessen it. The
openings, therefore, which are left in the lower part of the Muffle,
should not be so high as to admit coals or ashes to get into the
cupels; the use of them is to procure an easier passage for the heat
and the air to those vessels. The Muffle is left quite open in its
fore-part, that the operator may be at liberty to examine what passes
in the cupels, to stir their contents, to remove them from one place
to another, to convey new matters into them, &c. and also to promote
the free access of the air, which must concur with the fire towards the
evaporation necessary to the vitrification of lead; which air, if fresh
were not often enough admitted, would be incapable of producing that
effect; because it would soon be loaded with such a quantity of vapours
that it could not take up any more.

The government of the fire in this furnace is founded on the general
principles above laid down for all furnaces. Yet as there are some
little differences, and as it is very essential to the success of the
operations for which this furnace is intended, that the artist should
be absolutely master of his degree of heat, we shall in few words shew
how that may be raised or lowered.

When the furnace is filled with coals and kindled, if the door of the
ash-hole be set wide open, and that of the fire-place shut very close,
the force of the fire is increased; and if, moreover, the pyramidal
cover be put on the top, and the conical funnel added to it, the fire
will become still more fierce.

Seeing the matters contained in this furnace are encompassed with fire
on all sides, except in the fore-part opposite to the door of the
fire-place, and as there are occasions which require that the force
of the fire should be applied to this part also, an iron box, of the
shape and size of the door, hath been contrived to answer that purpose.
This box is filled with lighted coals, and applied immediately to the
door-place, by which means the heat there is considerably augmented.
This help may be made use of at the beginning of the operation, in
order to accelerate it, and bring the heat sooner to the desired
degree; or in case a very fierce heat be required; or at a time when
the air being hot and moist will not make the fire burn with the
necessary vigour.

The heat may be lessened by removing the iron box, and shutting the
door of the fire-place quite close. It may be still further and
gradually diminished, by taking off the conical funnel from the top; by
shutting the door of the fire-place with one of its plates only, that
which has the least, or that which has the greatest aperture in it; by
taking off the pyramidal cover; by shutting the ash-hole door wholly or
in part; and, lastly, by setting the door of the fire-place wide open:
but, in this last case, the cold air penetrates into the cavity of the
Muffle, and refrigerates the cupels more than is almost ever necessary.
If it be observed, during the operation, that the Muffle grows cold
in any particular part, it is a sign there is a vacuity left by the
coals in that place: in this case an iron wire must be thrust into the
furnace, through the hole which is over the door of the fire-place, and
the coals stirred therewith, so as to make them fall into their places
and fill up the vacant interstices.

It is proper to observe, that, besides what has been said concerning
the ways of increasing the activity of the fire in the cupelling
furnace, several other causes also may concur to procure to the matters
contained in the Muffle a greater degree of heat: for example, the
smaller the Muffle is, the wider and more numerous the holes in it are;
the nearer to its bottom, or further end, the cupels are placed, the
more will the matters therein contained be affected with heat.

Besides the operations to be performed by the cupel, this furnace
is very useful, and even necessary, for many chymical experiments;
such, for instance, as those relating to sundry vitrifications and
enamelling. As it is pretty low, the best way is to place it, when it
is to be used, on a base of brick-work that may raise it to a level
with the operator's hand.

A Lamp-furnace is exceeding useful for all operations that require
only a moderate, but long-continued, degree of heat. The furnace for
working with a lamp-heat is very simple: it consists only of a hollow
cylinder, from fifteen to eighteen inches high, and five or six in
diameter, having at its bottom an aperture large enough for a lamp to
be introduced and withdrawn with ease. The lamp must have three or four
wicks, to the end that by lighting more or fewer of them a greater
or less degree of heat may be produced. The body of the furnace must
moreover have several small holes in it, in order to supply the flame
of the lamp with air enough to keep it alive.

On the top of this furnace stands a bason five or six inches deep,
which ought to fill the cavity of the cylinder exactly, and to be
supported at its circumference by a rim which may entirely cover and
close the furnace: the use of this bason is to contain the sand through
which the lamp-heat is usually conveyed.

Besides this, there must be a kind of cover or dome made of the same
material with the furnace, and of the same diameter with the sand-bath,
without any other opening than a hole, nearly circular, cut in its
lower extremity. This dome is a sort of reverberatory, which serves
to confine the heat and direct it towards the body of the retort; for
it is used only when something is to be distilled in a vessel of this
fashion; and then the hole at its bottom serves for a passage to the
neck of the retort. This dome should have an ear or handle, for the
conveniency of putting it on and taking it off with ease.


_Of Lutes._

Chymical vessels, especially such as are made of glass, and the earthen
vessels commonly called stone-ware, are very subject to break when
exposed to sudden heat or cold: whence it comes, that they often crack
when they begin to heat, and also when being very hot they happen to be
cooled, either by fresh coals thrown into the furnace, or by the access
of cold air. There is no way to prevent the former of these accidents,
but by taking the pains to warm your vessel very slowly, and by almost
insensible degrees. The second may be avoided by coating the body of
the vessel with a paste or lute, which being dried will defend it
against the attacks of cold.

The fittest stuff for coating vessels is a composition of fat earth,
Windsor-loam, fine sand, filings of iron, or powdered glass, and
chopped cow's hair, mixed and made into a paste with water. This lute
serves also to defend glass vessels against the violence of the fire,
and to prevent their melting easily.

In almost all distillations it is of great consequence, as hath been
said, that the neck of the distilling vessel be exactly joined with
that of the receiver into which it is introduced, in order to prevent
the vapours from escaping into the air and so being lost: and this
junction is effected by means of a lute.

A few slips of paper applied round the neck of the vessels with common
size will be sufficient to keep in such vapours as are aqueous or not
very spirituous.

If the vapours are more acrid, or more spirituous, recourse may be had
to slips of bladder long steeped in water, which containing a sort of
natural glue, close the junctures of the vessels very well.

If it be required to confine vapours of a still more penetrating
nature, it will be proper to employ a lute that quickly grows very
hard; particularly a paste made with quick-lime and any sort of jelly,
whether vegetable or animal; such as the white of an egg, stiff size,
_&c._ This is an excellent lute, and not easily penetrated. It is also
used to stop any cracks or fractures that happen to glass vessels. But
it is not capable of resisting the vapours of mineral acid spirits,
especially when they are strong and smoking: for that purpose it is
necessary to incorporate the other ingredients thoroughly with fat
earth softened with water; and even then it frequently happens that
this lute is penetrated by acid vapours, especially those of the spirit
of salt, which of all others are confined with the greatest difficulty.

In such cases its place may be supplied with another, which is called
Fat Lute, because it is actually worked up with fat liquors. This
lute is composed of a very fine cretaceous earth, called tobacco-pipe
clay, moistened with equal parts of the drying oil of lint-seed, and a
varnish made of amber and gum copal. It must have the consistence of
a stiff paste. When the joints of the vessels are closed up with this
lute, they may, for greater security, be covered over with slips of
linen smeared with the lute made of quick-lime and the white of an egg.

Chymical vessels are liable to be broken in an operation by other
causes besides the sudden application of heat or cold. It frequently
happens, that the vapours of the matters exposed to the action of fire
rush out with such impetuosity, and are so elastic, that, finding no
passage through the lute with which the joints of the vessels are
closed, they burst the vessels themselves, sometimes with explosion and
danger to the operator.

To prevent this inconvenience, it is necessary that in every receiver
there be a small hole, which being stopped only with a little lute may
easily be opened and shut again as occasion requires. It serves for a
vent-hole to let out the vapours, when the receiver begins to be too
much crowded with them. Nothing but practice can teach the artist when
it is requisite to open this vent. If he hits the proper time, the
vapours commonly rush out with rapidity, and a considerable hissing
noise; and the vent should be stopped again as soon as the hissing
begins to grow faint. The lute employed to stop this small hole ought
always to be kept so ductile, that, by taking the figure of the hole
exactly, it may entirely stop it. Besides, if it should harden upon the
glass, it would stick so fast that it would be very difficult to remove
it without breaking the vessel. This danger is easily avoided by making
use of the fat lute, which continues pliant for a long time, when it is
not exposed to an excessive heat.

This way of stopping the vent-hole of the receiver has yet another
advantage: for if the hole be of a proper width, as a line and half, or
two lines, in diameter, then, when the vapours are accumulated in too
great a quantity, and begin to make a great effort against the sides of
the receiver, they push up the stopple, force it out, and make their
way through the vent-hole: so that, by this means, the breaking of the
vessels may always be certainly prevented. But great care must be taken
that the vapours be not suffered to escape in this manner, except when
absolute necessity requires it; for it is generally the very strongest
and most subtile part of a liquor which is thus dissipated and lost.

Heat being the chief cause that puts the elasticity of the vapours in
action, and prevents their condensing into a liquor, it is of great
consequence in distillation that the receiver be kept as cool as
possible. With this view a thick plank should be placed between the
receiver and the body of the furnace, to intercept the heat of the
latter, and prevent its reaching the former. As the vapours themselves
rise very hot from the distilling vessel, they soon communicate their
heat to the receiver, and especially to its upper part, against which
they strike first. For this reason it is proper that linen cloths, dipt
in very cold water, be laid over the receiver, and frequently shifted.
By this means the vapours will be considerably cooled, their elasticity
weakened, and their condensation promoted.

By what hath been said in this first part, concerning the properties
of the principal agents in Chymistry, the construction of the most
necessary vessels and furnaces, and the manner of using them, we are
sufficiently prepared for proceeding directly to the operations,
without being obliged to make frequent and long stops, in order to give
the necessary explanations on those heads.

Nevertheless, we shall take every proper occasion to extend the
theory here laid down, and to improve it by the addition of several
particulars, which will find their places in our Treatise of Chymical
Operations.



    ELEMENTS
    OF THE
    PRACTICE OF CHYMISTRY;

    WHEREIN

  The Fundamental Operations are described, and
  illustrated by Observations on each Process.


[Illustration: Decorative Scroll]



  ELEMENTS
  OF THE
  PRACTICE OF CHYMISTRY.



INTRODUCTION.


AS the Elements of the Theory of Chymistry, delivered in the former
part of this work, were intended for the use of persons supposed to be
altogether unacquainted with the art, they could not properly admit of
any thing more than fundamental principles, so disposed as constantly
to lead from the simple to the compound, from things known to things
unknown: for which reason I could not therein observe the usual order
of Chymical Decomposition, which is not susceptible of such a method.
I therefore supposed all the analyses made, and bodies reduced to
their simplest principles; to the end that, by observing the chief
properties of those primary elements, we might be enabled to trace them
through their several combinations, and to form some sort of judgment
_a priori_ of the qualities of such compounds as may result from their
junctions.

But this latter part is of a different nature. It is a practical
Treatise, intended to contain the manner of performing the principal
Operations of Chymistry; the operations which serve as standards for
regulating all the rest, and which confirm the fundamental truths laid
down in the Theory.

As these operations consist almost wholly of analyses and
decompositions, there can be no doubt concerning the order proper to
be observed in giving an account of them: it evidently coincides with
that of the analysis itself.

But as all bodies, which are the subjects of Chymical operations,
are divided by nature into three classes or kingdoms, the mineral,
the vegetable, and the animal, the analysis thereof may naturally be
divided into three branches: some difference may also arise from the
different order in which these three may be treated of.

As the reasons assigned for beginning with one kingdom rather than with
another have never been thoroughly canvassed, and may perhaps seem
equally good when viewed in a particular light, Chymical writers differ
in their opinions on this point. For my part, without entering into
a discussion of the motives which have determined others to follow a
different order, I shall only produce the reasons that led me to begin
with the mineral kingdom, to examine the vegetable in the second place,
and to conclude with the animal.

First, then, seeing vegetables draw their nourishment from minerals,
and animals derive theirs from vegetables, the bodies which constitute
these three kingdoms seem to be generated the one by the other, in a
manner that determines their natural rank.

Secondly, this disposition procures us the advantage of tracing the
principles, from their source in the mineral kingdom, down to the
last combinations into which they are capable of entering, that is,
into animal matters; and of observing the successive alterations they
undergo in passing out of one kingdom into another.

Thirdly and lastly, I look upon the analysis of minerals to be the
easiest of all; not only because they consist of fewer principles than
vegetables and animals, but also because almost all of them are capable
of enduring the most violent action of fire, when that is necessary to
their decomposition, without any considerable change or diminution of
their principles, to which those of other substances are frequently
liable.

Besides, I am not singular in this distribution of the three classes
of bodies, which are the subjects of the chymical analysis: as it is
the most natural, it has been adopted by several authors, or rather by
most who have published Treatises of Chymistry. But there is something
peculiarly my own in the manner wherein I have treated the analysis of
each kingdom. In the mineral kingdom, for instance, will be found a
considerable number of operations not to be met with in other Treatises
of Chymistry; the authors having probably considered them as useless,
or in some measure foreign, to the purpose of Elementary Books, and
as constituting together a distinct art. I mean the processes for
extracting saline and metallic substances from the minerals containing
them.

Yet, if it be considered that salts, metals, and semi-metals are
far from being produced by nature in a state of perfection, or in
that degree of purity which they are commonly supposed to have when
they are first treated of in Books of Chymistry; but that, on the
contrary, these substances are originally blended with each other, and
adulterated with mixtures of heterogeneous matters, wherewith they form
compound minerals; I imagine it will be allowed, that the operations by
which these minerals are decomposed, in order to extract the metals,
semi-metals, and other simpler substances, especially as they are
founded on the most curious properties of these substances, are so
far from being useless or foreign to the purposes of an Elementary
Treatise, that they are, on the contrary, absolutely necessary thereto.

After I had made these reflections, I could not help thinking that
an analysis of minerals, which should treat of saline and metallic
substances, without taking any notice of the manner in which their
matrices must be analysed, in order to extract them, would be no less
defective than a treatise of the analysis of vegetables, in which Oils,
essential Salts, fixed and volatile Alkalis, should be amply treated
of, without saying one word of the manner of analysing the plants from
which these several substances are obtained. I therefore thought myself
indispensably obliged to describe the manner of decomposing every ore
or mineral, before I attempted to treat of the saline or metallic
substance which it yields.

For example: as the Vitriolic Acid, with the consideration of which I
begin my Mineral Analysis, is originally contained in Vitriol, Sulphur,
and Alum; and as these substances again derive their origin from the
sulphureous and ferruginous Pyrites, the first operations I describe
under this head are the processes for decomposing the Pyrites in order
to extract its Vitriol, Sulphur, and Alum. I then proceed to the
particular analysis of each of these substances, with a view to extract
their Vitriolic Acid; and afterwards deliver, in their order, the other
operations usually performed on this Acid. Thus it appears, that this
saline substance occasions my describing the analyses of the Pyrites,
Vitriol, Sulphur, and Alum. The whole of the Treatise on Minerals
proceeds on the same plan.

The operations by which we decompose ores and minerals are of two
sorts: those employed in working by the great, and those for trying
in small the yield of any ore. These two manners of operating are
sometimes a little different; yet in the main they are the same,
because they are founded on the same principles, and produce the same
effects.

As my chief design was to describe the operations that may be
conveniently performed in a laboratory, I have preferred the processes
for small assays: especially as they are usually performed with more
care and accuracy than the operations in great works: and here I must
acknowledge, that I am obliged to M. Cramer's _Docimasia_, or Art
of Assaying, for all the operations of this kind in my analysis of
minerals. As M. Hellot's work on that subject did not appear till after
I had finished this, M. Cramer's _Docimasia_, in which sound Theory is
joined with accurate practice, was the best book of the kind I could
at that time consult. I therefore preferred it to all others; and as I
have not quoted it in my analysis of minerals, because the quotations
would have been too frequent, let what I say here serve for a general
quotation. I have been careful to name, as often as occasion required,
the other authors whose processes I have borrowed: it is a tribute
justly due to those who have communicated their discoveries to the
public.

Though I have told the reader that in my analysis of minerals he will
find the processes for extracting out of each the saline or metallic
substances contained in it, yet he must not expect that this book
will instruct him in all that is necessary he should know to be able
to determine, by an accurate assay, the contents of every mineral.
My intention was not to compose a Treatise of Assaying; and I have
taken in no more than was absolutely necessary to make the analysis
of minerals perfectly understood, and to render it as complete as it
ought to be in an Elementary Treatise. I have therefore described only
the principal operations relating thereto; the operations which are
fundamental, and which, as I said before, are to serve as standards
for the rest, abstracted from such additional circumstances as are of
consequence only to the Art of Assaying, properly so called.

Such therefore as are desirous of being fully instructed in that Art,
must have recourse to those works which treat professedly of the
subject; and particularly to that published by M. Hellot: a performance
most esteemed by such as are best skilled in Chymistry, and rendered
so complete by the numerous and valuable observations and discoveries
of the Author, that nothing better of the kind can be wished for. I
thought it proper to give these notices in relation to my analysis of
minerals; and shall now proceed to shew the plan of my analyses of
vegetables and of animals.

Seeing all vegetable matters are susceptible of fermentation, and when
analysed after fermentation, yield principles different from those we
obtain from them before they are fermented, I have divided them into
two classes; the former including vegetables in their natural state,
before they have undergone fermentation; and the latter those only
which have been fermented. This analysis opens with the processes
by which we extract from vegetables all the principles they will
yield without the help of fire: and then follow the operations for
decomposing plants by degrees of heat, from the gentlest to the most
violent, both in close vessels, and in the open air.

I have not made the same division in the animal kingdom, because the
substances that compose it are susceptible only of the last degree of
fermentation, or putrefaction; and moreover the principles they yield,
whether putrefied or unputrefied, are the very same, and differ only
with regard to their proportions, and the order in which they are
extricated during the analysis.

I begin this analysis with an examination of the milk of animals that
feed wholly on vegetables; because, though this substance be elaborated
in the body of the animal, and by that means brought nearer to the
nature of animal matters, yet it still retains a great similitude
to the vegetables from which it derives its origin, and is a sort
of intermediate substance between the vegetable and animal. Then I
proceed to the analysis of animal matters properly so called, those
which actually make a part of the animal body. I next examine the
excrementitious substances, that are thrown out of the animal body as
superfluous and useless. And then I conclude this latter part with
operations on the Volatile Alkali; a saline substance of principal
consideration in the decomposition of animal matters.

Though, in the general view here given of the order observed in this
Treatise of Practical Chymistry, I have mentioned only such processes
as serve for analysing bodies, yet I have also inserted some other
operations of different kinds. The book would be very defective if
it contained no more: for the design of Chymistry is not only to
analyse the mixts produced by nature, in order to obtain the simplest
substances of which they are composed, but moreover to discover by
sundry experiments the properties of those elementary principles, and
to recombine them in various manners, either with each other, or with
different bodies, so as to reproduce the original mixts with all their
properties, or even form new compounds which never existed in nature.
In this book therefore the reader will find processes for combining
and recompounding, as well as for resolving and decomposing bodies. I
have placed them next to the processes for decomposition, taking all
possible care not to interrupt their order, or break the connection
between them.



PART I.

OF MINERALS.



SECTION I.

_Operations performed on Saline Mineral Substances._



CHAP. I.

_Of the_ VITRIOLIC ACID.


PROCESS I.

_To extract Vitriol from the Pyrites._

Take any quantity you please of Iron Pyrites; leave them for some time
exposed to the air: they will crack, split, lose their brightness, and
fall into powder. Put this powder into a glass cucurbit, and pour upon
it twice its weight of hot water; stir the whole with a stick, and the
liquor will grow turbid. Pour it, while it is yet warm, into a glass
funnel lined with brown filtering paper; and having placed your funnel
over another glass cucurbit, let the liquor drain into it. Pour more
hot water on the powdered Pyrites, filter as before, and so go on,
every time lessening the quantity of water, till that which comes off
the Pyrites appears to have no astringent vitriolic taste.

Put all these waters together into a glass vessel that widens upwards;
set it on a sand-bath, and heat the liquor till a considerable smoke
arises; but take care not to make it boil. Continue the same degree of
fire till the surface of the liquor begins to look dim, as if some
dust had fallen into it; then cease evaporating, and remove the vessel
into a cool place: in the space of four and twenty hours will be formed
therein a quantity of crystals, of a green colour and a rhomboidal
figure: these are Vitriol of Mars, or Copperas. Decant the remaining
liquor; add thereto twice its weight of water; filter, evaporate, and
crystallize as before; repeat these operations till the liquor will
yield no more crystals, and keep by themselves the crystals obtained at
each crystallization.


_OBSERVATIONS._

The Pyrites are minerals which, by their weight and shining colours,
frequently impose on such as are not well acquainted with ores. At
first sight they may be taken for very rich ones; and yet they consist
only of a small quantity of metal combined with much sulphur or
arsenic, and sometimes with both.

They strike fire with a steel as flints do, and emit a sulphureous
smell: so that they may be known by this extemporaneous proof. The
metal most commonly and most abundantly found in the Pyrites is iron;
the quantity whereof sometimes equals, or even exceeds, that of the
sulphur. Besides metallic and sulphureous matters, the Pyrites contain
also some unmetallic earth.

There are several sorts of Pyrites: some of them contain only iron and
arsenic. They have not all the property of efflorescing spontaneously
in the air, and turning into vitriol: none do so but such as consist
only of iron and sulphur, or at least contain but a very small portion
of copper, or of arsenic: and even amongst those that are composed of
iron and sulphur alone, there are some that will continue for years
together exposed to the air without shooting, and indeed without
suffering the least sensible alteration.

The efflorescence of the Iron Pyrites, and the changes they undergo,
are phenomena well worth our notice. They depend on the singular
property which iron possesses of decomposing sulphur by the help of
moisture. If very fine iron-filings be accurately mingled with flowers
of sulphur, this mixture, being moistened with water, grows very hot,
swells up, emits sulphureous vapours, and even takes fire; what remains
is found converted into Vitriol of Mars. On this occasion, therefore,
the sulphur is decomposed; its inflammable part is dissipated or
consumed; its acid combines with the iron, and a Vitriol arises from
that conjunction.

This is the very case with the Pyrites that consist only of iron
and sulphur; yet some of them, as we said before, do not effloresce
spontaneously and turn to Vitriol. The reason probably is, that, in
such minerals, the particles of iron and sulphur are not intimately
mixed together, but separated by some earthy particles.

In order to procure Vitriol from Pyrites of this kind, they must be
for some time exposed to the action of fire, which, by consuming part
of their sulphur, and rendering their texture less compact, makes way
for the air and moisture, to which they must be afterwards exposed, to
penetrate their substance, and produce in them the changes with which
those others are affected that germinate spontaneously.

The Pyrites which contain copper and arsenic, and for that reason
do not effloresce, must likewise undergo the action of fire; which,
besides the effects it produces on Pyrites that consist of iron and
sulphur only, dissipates also the greatest part of the arsenic. These
Pyrites being first roasted, and then exposed to the air for a year or
two, do also yield Vitriol; but then it is not a pure Vitriol of Iron,
but is combined with a portion of blue Vitriol, the basis of which is
Copper.

Sometimes also there is Alum in the vitriolic waters drawn off the
Pyrites. It was on account of this mixture of different salts that we
recommended the keeping apart the crystals obtained from each different
crystallization: for by this means they may be examined separately, and
the species to which they belong discovered.

When Vitriol of Iron is adulterated with a mixture of the Vitriol
of Copper only, it is easy to purify it and bring it to be entirely
martial, by dissolving it in water, and setting plates of iron in the
solution: for iron having a greater affinity than copper with the
vitriolic acid, separates the latter from it, and assuming its place
produces a pure Vitriol of Mars.

In large works for extracting Vitriol from the Pyrites they proceed
thus. They collect a great quantity of Pyrites on a piece of ground
exposed to the air, and pile them up in heaps of about three feet high.
There they leave them exposed to the action of the air, sun, and rain,
for three years together; taking care to turn them every six months,
in order to facilitate the efflorescence of those which at first lay
undermost. The rain-water which has washed those Pyrites is conveyed by
proper channels into a cistern; and when a sufficient quantity thereof
is gathered, they evaporate it to a pellicle in large leaden boilers,
having first put into it a quantity of iron, some part of which is
dissolved by the liquor, because it contains a vitriolic acid that is
not fully saturated therewith. When it is sufficiently evaporated, they
draw it off into large leaden or wooden coolers, and there leave it to
shoot into crystals. In these last vessels several sticks are placed,
crossing each other in all manner of directions, in order to multiply
the surfaces on which the crystals may fasten.

The Pyrites are not the only minerals from which Vitriol may be
procured. All the ores of iron and copper that contain sulphur may
also be made to yield green or blue Vitriol, according to the nature
of each, by torrefying them, and leaving them long exposed to the air:
but this use is seldom made of them, as there is more profit to be got
by extracting the metals they contain. Besides, it is easier to obtain
Vitriol from the Pyrites than from those other mineral substances.


PROCESS II.

_To extract Sulphur from the Pyrites, and other sulphureous Minerals._

Reduce to a coarse powder any quantity of yellow Pyrites, or other
Mineral containing Sulphur. Put this powder into an earthen or glass
retort, having a long wide neck, and so large a body that the matter
may fill but two thirds of it. Set the retort in a sand-bath fixed over
a reverberating furnace: fit to it a receiver half full of water, and
so placed that the nose of the retort may be about an inch under the
water: give a gradual fire, taking care you do not make it so strong as
to melt the matter. Keep the retort moderately red for one hour, or an
hour and half, and then let the vessels cool.

Almost all the Sulphur separated by this operation from its matrix
will be found at the extremity of the neck of the retort, being fixed
there by the water. You may get it out either by melting it with such a
gentle heat as will not set it on fire, or by breaking the neck of the
retort.


_OBSERVATIONS._

Of all minerals the Pyrites contain the most Sulphur; those especially
which have the colour of fine brass, a regular form, such as round,
cubical, hexagonal, and being broken present a number of shining
needles, all radiating, as it were, from a center.

A very moderate heat is sufficient to separate the Sulphur they
contain. We directed that the retort employed should have a long and
wide neck, with a view to procure a free passage for the Sulphur: the
water set in the receiver detains the Sulphur, fixes it, and prevents
it from flying off; so that it is unnecessary to close the joints of
the vessels. But it is proper to take notice, that whenever you use
an apparatus for distilling, which requires the beak of the retort
to be under water, it is of very great consequence that the fire be
constantly so regulated, that the retort may not cool in the least;
for, in that case, as the rarefied air contained therein would be
condensed, the water in the receiver would rise into the retort and
break it.

If in distilling Sulphur, according to the present process, the matter
contained in the retort should happen to melt, the operation would be
thereby considerably protracted, and it would require a great deal
more time to extract all the Sulphur; because all evaporation is from
the surface only, and the matter, while it remains in a coarse powder,
presents a much more extensive surface than when it is melted.

This remark holds with regard to all other distillations. Any quantity
of liquor, set to distil in its fluid state, will take much more time
to rise in vapours, and pass from the retort into the receiver, than
if it be incorporated with some solid body reduced to minute parts, so
that the whole shall make a moist powder; and this though the very same
degree of fire be applied in both cases.

If the matter from which it is proposed to extract Sulphur be such as
will melt with the degree of fire necessary to this operation; that
is, with a heat which will make the retort but faintly red, it must
be mixed with some substance that is not so fusible. Very pure coarse
sand, or clean gravel, may be used with success: but absorbent earths
are altogether improper for this purpose, because they will unite with
the Sulphur.

The sulphureous minerals which are most apt to fuse are the cupreous
Pyrites, or yellow copper ores: common lead ores are also very fusible.

The Pyrites are by this operation deprived of almost all the Sulphur
they contain; and consequently little is left behind, but the particles
of iron and copper, together with a portion of unmetallic earth, which
we shall shew how to separate from these metals, when we come to
treat of them. I say that by this operation the Pyrites are deprived
of almost all, and not entirely of all their Sulphur; because, this
separation being made in close vessels only, there always remains
a certain quantity of Sulphur, which adheres so obstinately to the
metals, that it would be almost impossible to get it all out, even
though a much stronger fire than that directed in the process were
applied for this purpose, and though choice had been, as it ought to
be, made of such Pyrites, or other sulphureous Minerals as part most
easily with their sulphur. Nothing but a very strong fire in the open
air is capable of carrying it wholly off, or consuming it entirely.

In several places are found great quantities of native Sulphur. The
Volcanoes abound with it, and people gather it at the foot of those
burning mountains. Several springs of mineral waters also yield
Sulphur, and it is sometimes found sublimed to the vaulted roofs of
certain wells, and among others in one at Aix-la-Chapelle.

The Germans and Italians have large works for extracting Sulphur in
quantities out of Pyrites, and other minerals which abound therewith.
The process they work by is the same with that here delivered; but with
this difference only, that Sulphur being but of small value they do
not use so many precautions. They content themselves with putting the
sulphureous minerals into large crucibles, or rather earthen cucurbits,
which they place in the furnace in such a manner that, when the
sulphureous part melts, it runs into vessels filled with water, and is
thereby fixed.

The Sulphur obtained, either by distillation or by simple fusion, is
not always pure.

When it is obtained by distillation, if the matters from which you
extract it contain moreover some other minerals of nearly the same
volatility, such, for instance, as Arsenic, or Mercury, these minerals
will come over with it. This is easily perceived: for pure sublimed
Sulphur is always of a beautiful yellow, inclining to a lemon colour.
If it look red, or have a reddish cast, it is a sign that some Arsenic
hath risen along with it.

Mercury sublimed with Sulphur likewise gives it a red colour; but
Sulphur is very seldom adulterated with this metallic substance: for
Arsenic is frequently found combined with the Pyrites, and other
sulphureous minerals; whereas, on the contrary, we very rarely meet
with any Mercury in them.

But if Mercury should happen to rise with the Sulphur in distillation,
it may be discovered by examining the sublimate; which, in that case,
will have the properties of Cinabar: on being broken its inside will
appear to consist of needles adhering laterally to each other; its
weight will be very considerable; and, lastly, the great heat of the
place where it is collected will furnish another mark to know it by;
for, as Cinabar is less volatile than Arsenic or Sulphur, it fastens on
places too hot for either Sulphur or Arsenic to bear.

Sulphur may also be adulterated with such fixed matters, either
metallic or earthy, as it may have carried up along with it in the
distillation, or as may have been sublimed by the Arsenic, which has a
still greater power than Sulphur to volatilize fixed bodies.

If you desire to free the Sulphur from most of these heterogeneous
matters, it must be put into an earthen cucurbit, and set in a
sand-bath. To the cucurbit must be fitted one or more aludels, and such
a degree of heat applied as shall but just melt the Sulphur; which is
much less than that necessary to separate the Sulphur from its matrix.
As soon as the Sulphur is melted it will sublime in lemon-coloured
flowers, that will stick to the insides of the aludels.

When nothing more appears to rise with this degree of heat, the vessels
must be suffered to cool. At the bottom of the cucurbit will be found
a sulphureous mass, containing the greatest part of the adventitious
matters that were mixed with the Sulphur, and more or less red or
dark-coloured, according to the nature of those matters.

When we come to treat of Arsenic and Mercury, we shall give the methods
of separating Sulphur entirely from those metallic substances.


PROCESS III.

_To extract Alum from aluminous Minerals._

Take such minerals as are known or suspected to contain Alum. Expose
them to the air, that they may effloresce. If they remain there a year
without any sensible change, calcine them, and then leave them exposed
to the air, till a bit thereof being put on the tongue imparts an
astringent aluminous taste.

When your matters are thus prepared, put them into a leaden or glass
vessel; pour upon them thrice their weight of hot water; boil the
liquor; filter it; and repeat these operations till the earth be so
edulcorated that the water which comes off it hath no taste. Mix all
these solutions together, and let them stand four and twenty hours,
that the gross and earthy parts may settle to the bottom; or else
filter the liquor: then evaporate till it will bear a new-laid egg. Now
let it cool, and stand quiet four and twenty hours: in that time some
crystals will shoot, which are most commonly vitriolic; for Alum is
rarely obtained by the first crystallization. Remove these vitriolic
crystals: if any crystals of Alum be found amongst them, these must be
dissolved anew, and set to crystallize a second time in order to their
purification; because they partake of the nature as well as of the
colour of vitriol. By this method extract all the Alum that the liquor
will yield.

If you get no crystals of Alum by this means, boil your liquor again,
and add to it a twentieth part of its weight of a strong alkaline
lixivium, or a third part of its weight of putrefied urine, or a small
quantity of quick-lime. Experience and repeated trials must teach you
which of these three substances is to be preferred, according to the
particular nature of the mineral on which you are to operate. Keep
your liquor boiling, and if there be any alum in it, there will appear
a white precipitate: in that case let it cool and settle. When the
white precipitate is entirely fallen, decant the clear, and leave the
crystals of Alum to shoot at leisure, till the liquor will yield no
more: it will then be exceeding thick.


_OBSERVATIONS._

Alum is obtained from several sorts of Minerals. In some parts of
Italy, and in sundry other places, it effloresces naturally on the
surface of the earth. There it is swept together with brooms, and
thrown into pits full of water. This water is impregnated therewith
till it can dissolve no more. Then it is filtered, and set to evaporate
in large leaden vessels; and when it is sufficiently evaporated, and
ready to shoot into crystals, it is drawn off into wooden coolers, and
there left for the salt to crystallize.

In aluminous soils there are often found springs strongly impregnated
with Alum: so that to obtain it, the water need only be evaporated.

In the country about Rome there is a very hard stone, which is hewn out
of the quarry just like other stones for building; this stone yields
a great deal of Alum. In order to extract it, the stones are calcined
for twelve or fourteen hours; after which they are exposed to the air
in heaps, and carefully watered three or four times a-day for forty
days together. In that time they begin to effloresce, and to throw out
a reddish matter on their surface. Then they are boiled in water, which
dissolves all the Alum they contain, and, being duly evaporated, gives
it back in crystals. This is the Alum called _Roman Alum_.

Several sorts of Pyrites also yield a great deal of Alum. The English
have a stone of this kind, which, in colour, is very like a slate. This
stone contains much Sulphur, which they get rid of by roasting it.
After this they steep the calcined stone in water, which dissolves the
Alum it contains, and to this solution they add a certain quantity of a
lye made of the ashes of sea-weeds.

The Swedes have a Pyrites of a bright golden colour, variegated with
silver spots, from which they procure Sulphur, Vitriol, and Alum. They
separate from it the Sulphur and the Vitriol by the methods above
prescribed. When the liquor which hath yielded Vitriol is become thick,
and no more vitriolic crystals shoot in it, they add an eighth part of
its weight of putrefied urine, mixed with a lye made of the ashes of
green wood. Upon this there appears and falls to the bottom a copious
red sediment. They decant the liquor from this precipitate, and, when
it is duly evaporated, find it shoot into beautiful crystals of Alum.

What hath been said, concerning the several matrices from which Alum
is obtained, sufficiently shews, that it is seldom solitary in the
waters with which aluminous subjects have been lixiviated. It is almost
always accompanied with a certain quantity of Vitriol, or other saline
mineral matters, which obstruct its crystallization, and prevent its
being pure. It is with a view to free it from these matters, that the
waters impregnated with Alum are mixed with a certain quantity of the
lye of some fixed Alkali, or with putrefied urine, which contains much
volatile Alkali. These Alkalis have the property of decompounding
all the Neutral salts which have for their basis either an absorbent
earth or a metallic substance; and such as have a metallic substance
for their basis more readily than those whose basis is an earth.
Consequently, if they are mixed with a liquor in which both these sorts
of salts are dissolved, they must decompound that sort whose basis is
metallic sooner than the other whose basis is an earth. This is what
comes to pass in a solution of Alum and Vitriol. The metallic part of
the latter is separated from its acid by the Alkalis when mixed with
that solution; and it is this metallic part, which is generally iron,
that appears in the form of a reddish precipitate, as above-mentioned.

But because Alkalis decompound also those Neutral salts which have an
earth for their basis, care must be taken that too much thereof be not
added; else what you put in, more than is necessary to decompound the
vitriolic salts in your liquor, will attack the Alum, and decompound it
likewise.

The Alkali made use of to promote the crystallization of the Alum
joins with the Vitriolic Acid, which had dissolved the substances now
precipitated, and therewith forms different Neutral salts according
to its particular nature. If the Alkali be a lixivium of common
wood-ashes, the Neutral salt will be a vitriolated Tartar; if a
lixivium of the ashes of a maritime plant like Soda, the Neutral salt
will be a Glauber's salt; if putrefied urine, the Neutral salt will be
a vitriolic Ammoniacal salt. Some of these salts incorporate with the
Alum, which in large works crystallizes in vast lumps: and hence it
comes that some sorts of Alum when mixed with a fixed Alkali smell like
a volatile Alkali.

The crystals of Alum are octaedral, that is, they are solids with eight
sides. These octaedral solids are triangular pyramids, having their
angles cut away, so that four of their surfaces are hexagons, and the
other four triangles.

Sulphur, Vitriol, and Alum are the three principal subjects in which
we certainly know that the universal or Vitriolic Acid particularly
resides, and from which we extract it when we want to have it pure. For
this reason we thought it proper, before we treated of the extraction
of this Acid, to shew the method of separating those matters themselves
from the other minerals out of which we obtain them.

Moreover, all the other matrices, in which the Vitriolic Acid is most
commonly lodged, may be referred to one or other of the matters which
serve as bases to these three minerals.

To Sulphur we may refer all combinations of the Vitriolic Acid with an
inflammable matter: but we must take care not to confound Sulphur with
those Bitumens in which the Vitriolic Acid may be found: for the basis
of those bitumens is a real Oil; whereas the basis of Sulphur is the
pure Phlogiston. Yet as Oils themselves contain the Phlogiston, which,
in union with the Vitriolic Acid forms a true Sulphur, it follows that
such bitumens may in a certain respect be classed with Sulphur.

The same is to be said of Vitriol. The name is usually given to such
combinations only as are formed of the Vitriolic Acid with Iron or
Copper, which make the green and blue Vitriol; and to a third species
of Vitriol, which is white, and has Zinc for its basis: but as the
Vitriolic Acid may, by particular combinations, be united with many
other metallic substances, all such Metallic Salts must be referred to
the class of Vitriols.

The same may also be said of Alum, which is no other than a combination
of the Vitriolic Acid with a particular kind of absorbent earth; so
that all combinations of this Acid with any earth whatever may be
placed in the same class.

This last class of mixts is the most extensive of all that contain the
Vitriolic Acid; because there are a vast many earths, all differing
from one another, with which that Acid may be united. Alum properly
so called, the Gypsums, Talcs, Selenites, Boles, and all the other
compounds of this kind, differ from each other only in their particular
earths.

The different properties of these earthy salts depend on the nature of
their bases. Those which are of the aluminous kind retain much water in
crystallizing, which makes them very soluble in water, and gives them
the property of acquiring readily the aqueous fluor when exposed to the
fire. Those which are of the nature of the Selenites admit but very
little water in their crystals, and consequently are almost insoluble
in water; nor does the fire give them an aqueous fluor. Lastly, the
Gypsums and Talcs are still more destitute of these properties. The
natures of the earths in these several compounds are hitherto but very
imperfectly known, and may give the Chymists occasion for inquiries
equally curious and useful.

The Vitriolic Acid is sometimes found complicated with a fixed alkaline
basis. This is almost always the Alkali of Sea-salt; so that the
compound is a Glauber's Salt. Some mineral waters are impregnated
therewith; which happens when these waters contain Vitriol or Alum,
together with Sea-salt.

From the principles laid down, in our Elements of the Theory, it
appears that the Vitriolic Acid hath not so great an affinity with
earthy and metallic substances as with fixed Alkalis; and also that it
is stronger than the Marine Acid, and hath a greater affinity with
fixed Alkalis. This being allowed, the generation of native Glauber's
Salts is easily accounted for. The Acid of aluminous or vitriolic Salts
quits the earth or the metal with which it was combined, and expelling
the Acid of Sea-salt unites with its basis. Warmth greatly promotes
these decompositions.

If the common fossil salt, usually called _Sal Gem_, or any other kind
of Sea-salt, should happen to be near a Volcano, when it discharges
flaming Sulphur, as is frequently the case, and if this Sulphur should
run among the Sea-salt, a Glauber's Salt would instantly be formed in
that place; because when Sulphur burns, its Acid is separated and set
at liberty.

Lastly, if aluminous or vitriolic matters, or burning Sulphur, should
meet with the ashes of plants or trees consumed by fire, a vitriolated
Tartar would be formed, because these ashes contain a fixed Alkali of
the same nature with that of Tartar.

The Vitriolic Acid when combined with an earthy basis adheres strongly
thereto; so that the force of fire is able to expel very little or
none of it. There is no way of separating it from such a basis, but by
presenting to it an Alkaline Salt, with which it will unite: nor is it
ever extracted from such matters when it is required pure. It does not
adhere so firmly to metallic substances; but is separated from them by
the force of fire: so that it may be obtained from the several sorts
of Vitriol. It is usually drawn from Green Vitriol; that being the
commonest sort.

As to Sulphur, the Phlogiston which is its basis being the substance
wherewith the Vitriolic Acid hath the greatest affinity, it would be
altogether impossible to decompose it, and to separate its Acid, if it
were not inflammable; but by burning it the Phlogiston is destroyed,
and leaves the Acid at liberty. By this means therefore it may be
separated. We shall now give the processes for extracting the Acid from
Vitriol and Sulphur.


PROCESS IV.

_To extract the Vitriolic Acid from Green Vitriol._

Take any quantity of Green Vitriol: put it in an unglazed earthen
vessel, and heat it gradually. Vapours will soon begin to rise.
Increase the fire a little, and it will liquefy by means of the
water contained in it, and acquire what we called an _aqueous_ fluor.
Continue the calcination, and it will become less and less fluid, grow
thick, and turn of a greyish colour. Now raise your fire, and keep it
up till the salt recover its solidity, acquire an orange colour, and
begin to grow red where it immediately touches the sides of the vessel.
Then take it out, and reduce it to powder.

Put the Vitriol thus calcined and pulverized into a good earthen
retort, of which one half at least must remain empty. Set the retort
in a reverberatory furnace: fit thereto a large glass receiver, and,
having luted the joint well, give fire by degrees. You will soon see
white clouds rise into the receiver, which will render it opaque, and
heat it. Continue the same degree of fire till these clouds disappear:
they will be succeeded by a liquor which will trickle down the sides
of the receiver in veins. Still keep up the fire to the same degree
as long as these veins appear. When they begin to abate, increase the
fire, and push it to the utmost extremity: upon this, there will come
over a black, thick liquor: it will even be found congealed, and prove
the icy Oil of Vitriol, if care hath been taken to change the receiver,
keep the vessels perfectly close, and give a sufficient degree of heat.
Proceed thus till nothing more comes over, or at least very little. Let
the vessels cool, unlute them, pour the contents of the receiver into a
bottle, and seal it hermetically.


_OBSERVATIONS._

Green Vitriol retains much water in crystallizing; and, in order to
free it from that superfluous phlegm, it must be calcined before you
distil it. Without this precaution the operation will be exceedingly
protracted, and a great deal of time wasted in distilling such a
quantity of water; which will moreover greatly weaken the Acid by
commixing with it, unless care be taken to change the recipient as soon
as the water is all come over.

But there is also another advantage in calcining the Vitriol before
you put it into the retort: for otherwise this salt would melt on the
first application of heat, and run into a mass; which would prove a
great hindrance to its distillation. This inconvenience is avoided by
a previous calcination, in consequence whereof the Vitriol is easily
reduced to a powder which never becomes fluid.

Vitriol calcined as directed in the process grows so hard, and adheres
so firmly to the vessel in which the calcination is performed, that
it requires no small pains to separate and pulverize it. Care must
be taken to put it into the retort as soon as it is pulverized, and
to stop that vessel very close if you do not begin the distillation
immediately: for otherwise it will naturally attract from the air
almost all the moisture it hath lost.

The Acid which Vitriol yields by distillation is sulphureous; probably
because it still retains some of the Phlogiston, with which it was
united when under the form of sulphur in the Pyrites; or else hath laid
hold on a portion of that belonging to the iron which served for its
basis in Vitriol. But this sulphureous part is volatile, and flies off
in time.

This decomposition of Vitriol in close vessels is a difficult and
laborious process. To carry the operation to its utmost perfection
requires a fire of extreme violence, kept up without intermission
during four or five days; such in short as few vessels are able to
bear. Of course this operation is seldom performed in laboratories.
The French Chymists fetch their Oil of Vitriol from Holland, where it
is extracted from Vitriol in large quantities, by means of furnaces
erected for the purpose, in which many retorts are employed at once.

In the Memoirs of the Academy of Sciences M. Hellot hath given us the
most material circumstances of a very fine experiment of this kind, in
which he pushed the distillation of Green Vitriol to the utmost. Into
a German retort[5] he put six pounds of Green English Vitriol calcined
to redness, which he exposed to a fire of the extremest violence,
constantly kept up during four days and four nights. At the expiration
of that time he found in the vessels employed as receivers an Icy Oil
of Vitriol, which was altogether in a crystalline form and black. The
precautions necessary to make this experiment succeed, he represents,
in the following terms.

  [5] They are much the best, and bear a very fierce heat.

"The success of this operation, which produces an Oil of Vitriol
perfectly Icy and without any liquor, depends on the care taken to
prevent the acid vapours, driven by the fire out of Vitriol calcined to
redness, from having any communication with the external air while they
are distilling: for otherwise they will attract from it a moisture
which will keep them fluid in the receiver. The receiver must be at
such a distance from the furnace that it may remain cool enough for
the vapours to condense in it. There must also be sufficient room
for those vapours to circulate in, and to prevent the sulphureous
explosions, which are every now and then discharged out of the retort,
from bursting the vessels: for though the previous calcination of the
Vitriol hath carried off the most volatile, yet there still remains
enough of the inflammable principle, even in the iron itself, to
form a Sulphur with the Acid as it is extricated, or at least a mixt
that would be as apt to take fire as common Sulphur, if it were not
over-dosed with the Acid.

"As the best means of gaining these ends, M. Hellot contrived to adapt
to the neck of his retort a receiver with two necks, the lowermost of
which was inserted into a large ballon. Receivers applied to each other
in this manner are called Adopters.

"It is no easy matter to get this Icy Oil out of the ballon: for as
soon as the air touches it such a thick cloud of sulphureous fumes
arises, that it is absolutely necessary to place the vessel on some
shelf over head, because a man cannot stand exposed thereto for a
single minute without being suffocated."

This Icy Acid must be shut up with all possible expedition in a
crystal bottle accurately closed with a glass stopple, which should be
ground with emery in its neck so as to fit it exactly: for it attracts
moisture so powerfully, that, unless exceeding great care be taken to
prevent all communication with the external air, it will soon dissolve
into a fluid.

"The Icy Oil is black; because the acid vapours carry over with them
something of a greasy matter, from which Vitriol is seldom free, and
which always appears, after repeated solutions and crystallizations
of this Salt, in the mother-water which will shoot no more. Now the
smallest portion of inflammable matter presently blackens the most
highly rectified Oil of Vitriol, which is perfectly clear.

"The Vitriolic Acid, when forced over by a violent heat, carries
along with it some ferruginous particles also, that want nothing but
to be united with a phlogiston to become true iron. They are easily
discovered, either in the common black Oil of Vitriol, or in the
blackish crystals of the Icy Oil, by only dissolving them in a large
quantity of distilled water: for after seven or eight days digestion
a light powder or downy sediment precipitates, which being calcined
in a violent fire is partly attracted by the magnet; and being again
calcined with bees-wax becomes almost entirely iron."

The _Caput mortuum_ of this distillation of Vitriol is the ferruginous
earth of this Salt, and is called _Colcothar_. When this Colcothar hath
undergone a violent fire, as in the experiment now related, scarce any
Acid remains therein. Out of six pounds of Vitriol that M. Hellot used,
he could recover no more, by lixiviating what was left in the retort,
than two ounces of a Vitriolic Salt; and even that was very earthy.

If Vitriol be exposed to a fire neither so violent nor so long
continued, its Colcothar will yield a greater quantity of Vitriol that
hath not been decomposed. A white crystalline salt is also obtained
from it, and called _Salt of Colcothar_; which is no other than the
small portion of Alum usually contained in Vitriol, and not so easily
decomposed by the the action of fire.


PROCESS V.

_To decompose Sulphur, and extract its Acid, by burning it._

Take any quantity of the purest Sulphur: fill therewith a crucible or
other earthen dish: heat it till it melts; then set it on fire, and,
when its whole surface is lighted, place it under a large glass head,
taking care that the flame of the Sulphur do not touch either its sides
or bottom; that the air have free access, in order to make the Sulphur
burn clear; and that the head incline a little toward the side on which
its beak is, that, as the vapours condense therein, the liquor may run
off with ease. To the beak of this vessel fit a receiver: the fumes of
the lighted sulphur will be condensed, and gather into drops in the
head, out of which they will run into the receiver. There, when the
Sulphur has done burning, you will find an Acid liquor, which is the
Spirit of Sulphur.


_OBSERVATIONS._

In the burning of Sulphur, the Phlogiston which serves for its basis
is dissipated, and separated from the acid which is left at liberty.
The acid fumes which rise from the lighted sulphur strike against the
inside of the head placed over it, are there condensed, and appear
in the form of a liquor. But as Sulphur, like all other inflammable
bodies, Nitre excepted, will not burn in close vessels, it is necessary
that the air be freely admitted here; which occasions the loss of a
great deal of the Acid of the Sulphur, as is evident from the pungent
suffocating smell perceived in the laboratory during the operation.

This Acid, while combined with the Phlogiston, is incapable of
contracting any union with water; but when alone is very apt to mix
therewith: it is even proper to put some in its way, that it may
incorporate therewith as soon as it is discharged from the Sulphur; for
it is then very free from phlegm, very volatile, and consequently very
little disposed to condense into a liquor, but, on the contrary, very
apt to fly off in vapours. The water, which it imbibes with a kind of
avidity, fixes and detains it; so that by this means a much greater
quantity thereof is obtained from Sulphur, than if it were distilled
without this precaution.

It is proper, therefore, now and then, to introduce a dish full of
hot water under the head which receives the fumes of the Sulphur. The
vapours that exhale from the water be-dew the inside of the head, and
procure the advantage we are speaking of.

The same thing may be effected several other ways: thus, the crucible
containing the Sulphur may be set on a foot placed in an earthen dish
with some water in it; which, however, must not rise above the foot;
for if it should reach the crucible, it might cool and fix the sulphur.
The dish thus prepared must be placed on a sand-bath hot enough to make
the water smoke continually; and over all is to be placed the head as
directed in the process.

The size and form of the vessel which immediately receives the
sulphureous fumes may also contribute to increase the quantity of the
Acid Spirit. A very large vessel, with a hole at bottom no wider than
is just sufficient to admit the vapours, is the properest for this
operation.

After the Sulphur has burnt for some time, it often happens that a sort
of skin or crust forms on its surface, which is not inflammable, but
gradually lessens the quantity and vigour of the flame as it increases
in thickness, and at last puts it quite out. This crust proceeds from
the impurities, and heterogeneous uninflammable particles contained in
the sulphur. Care must be taken to remove it with an iron wire as fast
as it forms.

Two quantities of sulphur may also be kept in two crucibles, and
heated alternately. That in which the Sulphur is hot and melted may be
substituted for the other in which the Sulphur is grown cold and fixed;
because cold Sulphur does not burn well.

The Spirit of Sulphur is at first pungent and volatile, because it
still retains a small portion of the Phlogiston: but that sulphureous
part flies off, especially if the bottle in which the Spirit is kept be
left for some time unstopped.

The Acid obtained from Sulphur appears by all chymical proofs perfectly
like that obtained from Vitriol: they differ in this only, that the
former is the purest; for the Acid obtained from Vitriol carries over
with it some metallic parts, as we observed before, which can never
happen to that obtained from Sulphur.

If linen rags dipped in a solution of Fixed Alkali be exposed to the
fumes of burning brimstone, the Spirit of Sulphur joins with the
Alkali, and therewith forms a Vitriolated Tartar. This Salt is known
to be formed when the rags grow stiff, and appear spangled with a vast
many glittering points, which are nothing but little crystals of the
Salt we are speaking of.

When the Sulphur burns very gently and slowly the Spirit that exhales
from it is so much the more sulphureous and volatile: and hence the
Salt formed by the combination of this Spirit with the Alkali exposed
to it in linen rags, as in the above-mentioned experiment, is not
at first a Vitriolated Tartar; but a Neutral Salt of a particular
kind, which is capable of being decomposed by any other Mineral Acid,
the sulphureous Acid having less affinity than any of the rest with
Alkalis. Nevertheless, this Salt becomes in time a true Vitriolated
Tartar, because the sulphureous part which weakened its Acid easily
quits it and flies off.


PROCESS VI.

_To concentrate the Vitriolic Acid._

Take the Vitriolic Acid you intend to concentrate, that is, to
dephlegmate and make stronger: pour it into a good glass retort, of
such a size that your quantity of Acid may but half fill it: set this
retort in the sand-bath of a reverberating furnace: fit to it a
receiver; lute it on, and give a gradual fire. There will come over
into the receiver a clear liquor, the first drops of which will be but
faintly acid: this is the most aqueous part.

When the drops begin to follow one another much more slowly, raise your
fire, till the liquor begin to bubble a little in the middle. Keep
it thus gently boiling, till one half or two thirds thereof be come
over into the receiver. Then let your vessels cool; unlute them; what
remains in the retort pour into a crystal bottle, and stop it exactly
with a glass stopple rubbed with emery.


_OBSERVATIONS._

The Acid obtained from Sulphur is generally very aqueous; either
because in preparing it water must necessarily be administered, that it
may unite therewith as it separates from the Sulphur; or because it is
so greedy of moisture as to attract a great deal from the air, which
must needs be admitted to make the Sulphur burn.

The Acid obtained from Vitriol, excepting that which rises last, is
also mixed with a pretty considerable quantity of phlegm; because
the Vitriol, though calcined, still retains a great deal thereof,
which rises with the Acid in distillation. Now, as there are many
chymical experiments that will not succeed without Acids exceedingly
dephlegmated, it is proper to have in a laboratory all the Acids thus
conditioned; because if they happen to be too strong for particular
operations, as is sometimes the case, it is very easy to lower them to
the desired degree, by adding a sufficient quantity of water.

The Vitriolic Acid is much heavier and much less volatile than water.
If therefore a mixture of these two liquors be exposed to the fire, the
aqueous part will rise with a degree of heat which is not able to carry
up the Acid: by this means they may be separated from each other; and
thus is the Vitriolic Acid concentrated.

Nevertheless, as this Acid combines most closely with water, and is in
a manner strongly connected with it, the water carries up some portion
thereof along with it; and hence it comes, that the liquor which rises
into the receiver is acid: it is called _Spirit of Vitriol_.

As the fire carries off the most aqueous part, the other which remains
in the retort increases in specific gravity. The Acid particles
are brought nearer together, retain the aqueous particles more
obstinately, and therefore to separate them the degree of heat must be
increased.

It is usual to draw off one half or two thirds of the liquor that was
put into the retort: but this depends on the degree of strength the
Acid was of before concentration, and the degree of concentration
intended to be given it.

If the Acid to be concentrated be Oil of Vitriol, from being brown or
black it grows clearer as the operation advances, and at last becomes
perfectly colourless and transparent; because the fat matter which
tinged it black is dissipated during the process. Some of it deposites
a white crystalline earth.

A sulphureous smell is generally perceived about the vessels in this
operation. This arises from a small portion of the Phlogiston from
which the Acid is not free; and it is this inflammable matter which
gives the Oil of Vitriol its black colour: for the clearest and best
rectified Oil of Vitriol will become brown, and even black, in a short
time, if any inflammable matter, though in a very small quantity, be
dissolved therein.

The vessels are luted in this operation, to prevent any loss of the
Spirit of Vitriol, which being very acid is of use in many chymical
experiments, and may itself also be again concentrated.

We observed, that in this operation it is necessary the retort should
be of very good glass. Indeed the Acid is so active, and so strong,
that if the glass be tender and have a little too much salt in its
composition, it will be so corroded thereby that it will fall to pieces.

Though we directed the retort to be set in a sand-bath for this
operation, it does not follow that it may not also be placed in a naked
fire: on the contrary, when the heat is not conveyed through a bath the
operation advances faster, and is much less tedious. But then great
caution must be used, and the closest attention given to the management
of the fire, which must be raised by almost imperceptible degrees,
especially at the beginning of the operation; otherwise it is next to a
certainty that the vessels will break. In general, a naked fire may be
employed in almost all distillations which require a greater degree of
heat than that of boiling water, or the _balneum mariæ_: the operation
will be sooner finished; but it requires an experienced hand, that has
by practice acquired a habit of governing the fire with judgment.

There is moreover another advantage in not using the sand-bath; which
is, that if in the time of the operation you perceive the fire too
fierce, you can quickly check it, either by stopping close all the
apertures of the furnace, or by drawing out all or part of the lighted
coals. This inconvenience is not near so easily remedied when you use
the sand-bath; because when once heated it retains its heat very long
after the fire is quite extinguished.


PROCESS VII.

 _To decompose Vitriolated Tartar by means of the Phlogiston; or to
 compose Sulphur by combining the Vitriolic Acid with the Phlogiston._

Take equal parts of Vitriolated Tartar, and very dry Salt of Tartar,
separately reduced to powder; add an eighth part of their weight of
charcoal-dust; and mix the whole together very accurately. Throw this
mixture into a red-hot crucible, placed in a furnace filled with
burning coals. Cover it very close, and keep it very hot; till the
mixture melt, which may be known by uncovering the crucible from time
to time. There will then appear a blueish flame, accompanied with a
pungent smell of Sulphur.

Take the crucible out of the fire: dissolve its contents in hot water:
filter the solution through brown paper supported by a glass funnel:
drop into the filtered liquor by little and little any Acid whatever.
As you add the acid the liquor will grow more and more turbid, and let
fall a grey precipitate. Continue dropping in more Acid till the liquor
will yield no more precipitate. Filter it a second time, to separate it
from the precipitate: what remains on the filter is a true inflammable
Sulphur, which you may either melt or sublime into flowers.


_OBSERVATIONS._

All bodies that contain the Vitriolic Acid may contribute, as well
as Vitriolated Tartar, to the generation of Sulphur: so that all the
neutral salts in which this Acid is a principle, the Alums, Selenites,
Gypsums, Vitriols, may be substituted for it in this experiment. All
these matters, with the addition of charcoal-dust only, being fused
in a crucible, constantly produce Sulphur; because the Vitriolic Acid
having a greater affinity with the Phlogiston than with any thing
else, will quit its basis, whatever it be, to join with the Phlogiston
of the charcoal, and therewith form a Sulphur.

The fixed Alkali added thereto helps to promote the fusion of the
ingredients, which is necessary for effecting the desired combination.
It also serves to unite with the Sulphur, when formed; and thus makes
the combination called _Liver of Sulphur_, which prevents the Sulphur
from being consumed as soon as formed: for the fixed Alkalis, which are
incombustible, hinder Sulphur from burning so easily as it would do if
they were not joined with it. They may afterwards be separated from
each other, by the means of any Acid whatever.

This process, in which Sulphur is regenerated by recombining together
the principles of which it was originally composed, is one of the most
beautiful experiments that modern Chymistry hath produced. We are
indebted for it to M. Stahl; and Dr. Geoffroy hath given a particular
account of it in the Memoirs of the Academy of Sciences.

Before these gentlemen Glauber and Boyle had indeed published methods
of producing Sulphur, Glauber made use of his _Sal mirabile_ and
powdered charcoal: Boyle employed the Vitriolic Acid and Oil of
Turpentine. But neither of those Chymists understood the true theory
of their operations: they did not thoroughly know the principles of
Sulphur: they did not imagine they had composed Sulphur: they thought
they only extracted what they supposed to exist previously in the
matters they employed in their experiments.

M. Stahl was the first who discovered and explained the nature of
Sulphur, and proved that in Glauber's and Boyle's experiments Sulphur
was actually produced, by uniting together the principles of which it
is constituted. This beautiful experiment gives the strongest lustre
of evidence to the theory of the composition of that mixt, which acts
such a capital part in Chymistry; and it can no longer be doubted,
that Sulphur is actually a combination of the Vitriolic Acid with the
Phlogiston.

Besides this important truth, our process for composing Sulphur by art
proves several others that are equally essential and fundamental.

The first is, that the Vitriolic Acid hath a greater affinity with
the Phlogiston than with any other thing, seeing it quits metallic
and earthy substances, as well as Alkaline salts, in order to combine
therewith.

The second is, that Sulphur combines with fixed Alkalis without
suffering any decomposition; seeing it may be separated from them
entire and unaltered; and seeing that very Sulphur, which is naturally
indissoluble in water, is rendered soluble therein by the union it hath
contracted with the fixed alkali.

The third is, that the Vitriolic Acid, which, when it is pure, hath the
greatest affinity with Alkalis of any Acid whatever, loses a great deal
of that affinity by contracting an union with the Phlogiston; seeing
the weakest acids are capable of decomposing the Liver of Sulphur, and
separating the Sulphur from the Alkali. And this also confirms one of
the general propositions concerning affinities advanced in our theory;
to wit, that the affinities of compound or mixed substances are weaker
than those of the same substances in a purer or more simple state.



CHAP. II.

_Of the_ NITROUS ACID.


PROCESS I.

 _To extract Nitre out of nitrous Earths and Stones. The Purification
 of Salt-petre. Mother of Nitre. Magnesia._

Take any quantity of nitrous earths or stones; reduce them to powder;
and therewith mix a third part of the ashes of green-wood and
quick-lime. Put this mixture into a barrel or vat, and pour on it hot
water to about twice the weight of the whole mass. Let it stand thus
for twenty-four hours, stirring it from time to time with a stick. Then
filter the liquor through brown paper, or pass it through a flannel
bag, till it come clear: it will then have a yellowish colour. Boil
this liquor, and evaporate till you perceive that a drop of it let fall
on any cold body coagulates. Then stop the evaporation, and set your
liquor in a cool place. In the space of four and twenty hours crystals
will be formed in it, the figure of which is that of an hexagonal
prism, having its opposite planes generally equal, and terminated at
each extremity by a pyramid of the same number of sides. These crystals
will be of a brownish colour, and deflagrate on a live coal.

Decant the liquor from these crystals; mix it with twice its weight
of hot water; evaporate and crystallize as before. Repeat the same
operation till the liquor will yield no more crystals: it will then be
very thick, and goes by the name of _Mother of Nitre_.


_OBSERVATIONS._

Earths and stones that have been impregnated with animal or vegetable
juices susceptible of putrefaction, and have been long exposed to the
air, but sheltered from the sun and rain, are those which yield the
greatest quantity of Nitre. But all sorts of earths and stones are not
equally fit to produce it. None is ever found in flints or sands of a
crystalline nature.

Some earths and stones abound so with Nitre, that it effloresces
spontaneously on their surface, in the form of a crystalline down. This
Nitre may be collected with brooms, and accordingly has the name of
_Salt-petre Sweepings_. Some of this sort is brought from India.

Hitherto we are much in the dark as to the origin and generation of
Nitre. Some Chymists pretend that the Nitrous Acid is diffused through
the air, and gradually deposited in such earths and stones as are
qualified to receive it.

Others, considering that none of it is ever obtained but from earths
that have been impregnated with vegetable or animal juices, have from
thence concluded those two kingdoms to be the general repositories
of the Nitrous Acid; that if we do not perceive it to exist in such
matters at all, or at least in any great quantity, till they have
undergone putrefaction, and are in some measure incorporated with
suitable earths and stones, it is because the Acid is so entangled
with heterogeneous particles that it requires the assistance of
putrefaction, and much more of filtration through an earth, to
disengage it, and enable it to appear in its proper nature.

Lastly, others are of opinion that this Acid is no other than the
universal or Vitriolic Acid; disguised indeed by a portion of the
Phlogiston, which is combined with it in a peculiar manner by the means
of putrefaction. They ground this opinion chiefly on the analogy or
resemblance which they find between the Nitrous Acid and the Volatile
Sulphureous Spirit. Its volatility, its pungent smell, its properties
of taking fire, and of destroying the blue and violet colours of
vegetables, serve them as so many proofs.

Their opinion is the more probable on this account, that even though
the Nitrous Acid should actually be produced by vegetable and animal
substances, yet as these substances themselves draw all their component
principles from the earth, and as the Vitriolic Acid is diffused
through all the soils which afford them nourishment, there is great
reason to think that the Nitrous Acid is no other than the Vitriolic
Acid altered by the changes and combinations it hath undergone in its
passage into and through those substances. In 1750 the Royal Academy
of Sciences at Berlin proposed an account of the generation of Nitre
as the subject for their prize, which was conferred on a Memoir
wherein this last opinion was supported by some new and very judicious
experiments.

The process by which our Salt-petre makers extract Nitre in quantities,
out of rubbish and nitrous earths, is very nearly the same with that
here set down; so that I shall not enter into a particular account
of it. I shall only take notice of one thing, which it is of some
consequence to know; namely, that there is no nitrous earth which does
not contain sea-salt also. The greatest quantities of this salt are to
be found in those earths which have been drenched with urine, or other
animal excrements. Now as the rubbish of old houses in great cities
is in this class, it comes to pass that when the Salt-petre workers
evaporate a nitrous lixivium drawn from that rubbish, as soon as the
evaporation is brought to a certain pitch, a great many little crystals
of sea-salt form in the liquor, and fall to the bottom of the vessel.

The Salt-petre workers in France call these saline particles _the
Grain_, and take care to separate them from the liquor (which, as
long as it continues hot, keeps the salt-petre dissolved) before they
set it to crystallize. This fact seems a little singular, considering
that sea-salt dissolves in water more easily than salt-petre, and
crystallizes with more difficulty.

In order to discover the cause of this phenomenon, we must recollect
some truths delivered in our theoretical Elements. The first is, that
water can keep but a determinate quantity of any salt in solution, and
that if water fully saturated with a salt be evaporated, a quantity
of salt will crystallize in proportion to the quantity of water
evaporated. The second is, that those salts which are the most soluble
in water, particularly those which run in the air, will dissolve in
cold and in boiling water equally; whereas much greater quantities of
the other salts will dissolve in hot and boiling water than in cold
water. These things being admitted, when we know that sea-salt is
one of the first sort, and salt-petre of the second, the reason why
sea-salt precipitates in the preparation of salt-petre appears at once.
For,

When the solution of Salt-petre and Sea-salt comes to be evaporated to
such a degree that it contains as much Sea-salt as it possibly can,
this salt must begin to crystallize, and continue to do so gradually
as the evaporation advances. But because at the same time it does not
contain as much salt-petre as it can hold, seeing it is capable of
dissolving a much greater quantity thereof when it is boiling hot than
when it is cold, this last-named salt will not crystallize so soon. If
the evaporation were continued till the case of the Salt-petre came to
be the same with that of the Sea-salt, then the salt-petre also would
begin to crystallize gradually in proportion to the water evaporated,
and the two salts will continue crystallizing promiscuously together:
but it is never carried so far; nor is it ever necessary: for, as the
water cools, it becomes more and more incapable of holding in solution
the same quantity of salt-petre as when it was boiling hot.

And then comes the very reverse, with regard to the crystallizing of
the two salts; for then the Salt-petre shoots, and not the Sea-salt.
The reason of this fact also is founded on what has just been said. The
Sea-salt, of which cold water will dissolve as much as boiling water,
and which owed its crystallizing before only to the evaporation, now
ceases to crystallize as soon as the evaporation ceases; while the
Salt-petre, which the water kept dissolved only because it was boiling
hot, is forced to crystallize merely by the cooling of the water.

When the solution of Salt-petre has yielded as many crystals of that
Salt as it can yield by cooling, it is again evaporated, and being
then suffered to cool yields more crystals. And thus they continue
evaporating and crystallizing, till the liquor will afford no more
crystals. It is plain that as the Salt-petre crystallizes, the
proportion of Sea-salt to the dissolving liquor increases; and as a
certain quantity of water evaporates also during the time employed in
crystallizing the Salt-petre, a quantity of Sea-salt, proportioned to
the water so evaporating, must crystallize in that time: and this is
the reason why Salt-petre is adulterated with a mixture of Sea-salt.
It likewise follows that the last crystals of Nitre, obtained from a
solution of Salt-petre and Sea-salt, contain much more Sea-salt than
the first.

From all that has been said concerning the crystallization of
Salt-petre and Sea-salt, it is easy to deduce the proper way of
purifying the former of these two Salts from a mixture of the latter.
For this purpose the Salt-petre to be refined need only be dissolved
in fair water. The proportion between the two salts in this second
solution is very different from what it was in the former; for it
contains no more Sea-salt than what had crystallized along with the
Salt-petre under favour of the evaporation, the rest having been left
dissolved in the liquor that refused to yield any more nitrous crystals.

As there is therefore a much greater quantity of Salt-petre than of
Sea-salt in this second solution, it is easy to evaporate it to such a
degree that a great deal of Salt-petre shall crystallize, while much
more of the water must necessarily be evaporated before any of the
Sea-salt will crystallize.

However, the Salt-petre is not yet entirely freed from all mixture of
Sea-salt by this first purification; for the crystals obtained from
this liquor, in which Sea-salt is dissolved, are still encrusted, and,
as it were, infected therewith: hence it comes, that, to refine the
Salt-petre thoroughly, these crystallizations must be repeated four or
five times.

The Salt-petre men commonly content themselves with crystallizing it
thrice, and call the produce Salt-petre of the first, second, or third
shoot, according to the number of crystallizations it has undergone.
But their best refined Salt-petre, even that of the third shooting, is
not yet sufficiently pure for Chymical experiments that require much
accuracy: so that it must be further purified; but still by the same
method.

The Nitrous Acid is not pure in the earths and stones from which it
is extracted. It is combined partly with the very earth in which
it is formed, and partly with the Volatile Alkali produced by the
putrefaction of the vegetable or animal matters that concurred to its
generation. A Fixed Alkali and Quick-lime are added to the lixivium
of a nitrous earth, in order to decompose the nitrous Salt formed in
that earth, and to separate the Acid from the Volatile Alkali and the
absorbent earth with which it is united: thence comes that copious
sediment which appears in the lye at the beginning of the evaporation.
These matters form with that Acid a true Nitre, much more capable than
the original Nitrous Salts of crystallization, detonation, and the
other properties which are essential thereto. The basis of Nitre is
therefore a Fixed Alkali mixed with a little lime.

The Mother of Nitre, which will yield no more crystals, is brown and
thick: by evaporation over a fire it is further inspissated, and
becomes a dry, solid body; which, however, being left to itself soon
gives, and runs into a liquor. This water still contains a good deal of
Nitre, Sea-salt, and the Acids of these Salts united with an absorbent
earth. It contains moreover a great deal of a fat, viscid matter, which
prevents its crystallizing.

All saline solutions in general, after having yielded a certain
quantity of crystals, grow thick, and refuse to part with any
more, though they still contain much Salt. They are all called
_Mother-waters_, as well as that which hath yielded Nitre. The
Mother-waters of different Salts may prove the subjects of curious and
useful inquiries.

If a Fixed Alkali be mixed with the Mother of Nitre, a copious white
precipitate immediately falls, which being collected and dried is
called _Magnesia_. This precipitate is nothing but the absorbent earth
that was united with the Nitrous Acid, together with a good deal of the
lime that was added, and was also united with that Acid, from which
they are now separated by the Fixed Alkali, according to the usual laws
of affinities.

The Vitriolic Acid poured upon Mother of Nitre causes many Acid vapours
to rise, which are a compound of the Nitrous and Marine Acids, that is,
an _Aqua Regia_. On this occasion also there falls a large quantity of
a white powder, which is still called _Magnesia_; yet it differs from
the former in that it is not, like it, a pure absorbent earth, but
combined with the Vitriolic Acid.

An _Aqua regis_ may also be drawn from nitrous earths by the force of
fire only, without the help of any additament.


PROCESS II.

_To decompose Nitre by means of the Phlogiston. Nitre fixed by
Charcoal._ Clyssus _of Nitre_. Sal Polychrestum.

Take the purest Salt-petre in powder; put it into a large crucible,
which it may but half fill; set the crucible in a common furnace,
and surround it with coals. When it is red-hot the Nitre will melt,
and become as fluid as water. Then throw into the crucible a small
quantity of charcoal-dust: the Nitre and the Charcoal will immediately
deflagrate with violence; and a great commotion will be raised,
accompanied with a considerable hissing, and abundance of black smoke.
As the charcoal wastes, the detonation will abate, and cease entirely
as soon as the coal is quite consumed.

Then throw into the crucible the same quantity of charcoal-dust as
before, and the same phenomena will be repeated. Let this coal also
be consumed: then add more, and go on in the same manner till you
can excite no further deflagration; always observing to let the
burning coal be entirely consumed before you add any fresh. When no
deflagration ensues, the matter contained in the crucible will have
lost much of its fluidity.


_OBSERVATIONS._

Nitre will not take fire, unless the inflammable matter added to it
be actually burning, or the Nitre itself red-hot, and so thoroughly
ignited, as immediately to kindle it. Therefore, if you would procure
the detonation of Nitre with charcoal, and make use of cold charcoal,
as in the process, the Nitre in the crucible must be red-hot, and in
perfect fusion: but you may also use live coals, and then the Nitre
need not be red-hot.

It is proper that the crucible used in this experiment should be only
half full; for during the detonation its contents swell, and might run
over without this precaution. For the same reason the charcoal-dust is
to be thrown in by little and little; and that first put in must be
entirely consumed before any fresh be added.

The matter remaining in the crucible after the operation is a very
strong Fixed Alkali. Being exposed to the air it quickly attracts the
moisture thereof, and runs into a liquor. It is called _Alkalizated
Nitre_, or, to distinguish it from Nitre alkalizated by other
inflammable matters, _Nitre fixed by charcoal_.

However, this Alkali is not absolutely pure. It still contains a
portion of the Nitre that hath not been decomposed. For when there
remains but a little of this salt mixed with a great quantity of
Alkali, which is not inflammable, the Alkali in some measure shelters
it, coats it over, and obstructs that immediate contact with the
inflammable matters applied, which is necessary to make it deflagrate.

If the Fixed Alkali be desired perfectly free from any mixture of
undecomposed Nitre, the fire about the crucible must be considerably
increased as soon as the detonation is entirely over; the matter must
be made to flow, which requires a much stronger heat than would melt
Nitre, and kept thus in fusion for about an hour. After this no perfect
Nitre will be found therein: for the little that was left, being unable
to abide the force of the fire, as not being extremely fixed, either
is entirely dissipated, or loses its Acid, which is carried off by the
violence of the heat.

Fixed Nitre contains also a portion of the earth that constituted the
basis of the Nitre, which is no other than the lime employed in its
crystallization, or else some of the earth with which its Acid was
originally combined, and which it retained in crystallizing. When Nitre
is deflagrated with such matters as produce ashes, these ashes likewise
furnish a certain quantity of earth, which mixes with the Fixed Alkali.
To separate these several earths from the Alkali, nothing more is
requisite than to let it run _per deliquium_, or to dissolve it in
water, and filter the solution through brown paper. Whatever is saline
will pass through the filtre with the water, and the earthy part will
be left upon it.

The Nitrous Acid is not only dissipated during the deflagration of the
Nitre, but is even destroyed, and perfectly decomposed. The smoke that
rises during the operation has not the least odour of an Acid. Its
nature may be accurately examined by catching it in proper vessels, and
condensing it into a liquor.

Nitre differs from Sulphur, and from all other inflammable bodies
whatever, in this, that the free access of the air is indispensably
necessary to make any of the others burn; whereas Nitre, and Nitre
only, is capable of burning in close vessels: and this property
furnishes us with the means of collecting the vapours which it
discharges in deflagration.

For this purpose, to a tubulated earthen retort you must fit two or
three large adopters: set the retort in a furnace; and under it make a
fire sufficient to keep its bottom moderately red. Then take a small
quantity, two or three pinches for example, of a mixture of three parts
of Nitre with one of charcoal-dust, and drop it into the retort through
its tube, which must be uppermost, and immediately stopped close.
A detonation instantly ensues, and the vapours that rise from the
inflamed mixture of Nitre and charcoal, passing out through the neck
of the retort into the adopters, circulate therein for a while, and at
last condense into a liquor.

When the detonation is over, and the vapours condensed, or nearly so,
drop into the retort another equal quantity of the mixture; and repeat
this till you find there is liquor enough in the recipients to be
examined with ease and accuracy. This liquor is almost insipid, and
shews no tokens of acidity; or at most but very slight ones. It is
called _Clyssus_ of Nitre.

It is easy to perceive why several adopters are required in this
experiment, and why a very small quantity of the mixture must be
introduced into the retort at once. The explosion, and the quantity of
air and vapours discharged on this occasion, would quickly burst the
vessels, if all these precautions were not attended to. This plainly
appears from the terrible effects of gun-powder, which is nothing but a
composition of Nitre, Sulphur, and Charcoal.

Nitre is also decomposed and takes fire by the means of Sulphur; but
the circumstances and the result differ widely from those produced
therewith by charcoal, or any other inflammable body.

Nitre deflagrates with Sulphur on account of the Phlogiston which the
latter contains. If one part of Sulphur be mixed with two or three
parts of Nitre, and the mixture thrown by little and little into a
red-hot crucible, upon every projection there arises a detonation
accompanied with a vivid flame.

The vapours discharged on this occasion have the mingled smell of
a Sulphureous Spirit and Spirit of Nitre; and if they be collected
by means of a tubulated retort, and such an apparatus of vessels as
was used in the preceding experiment, the liquor contained in the
recipients is found to be an actual mixture of the Acid of Sulphur, the
Sulphureous Spirit, and the Acid of Nitre; the first being in greater
quantity than the other two, and the second greater than the last.

Nor is the remainder after detonation a Fixed Alkali, as in the former
experiments; but a Neutral Salt, consisting of the Acid of Sulphur
combined with the Alkali of Nitre; a sort of Vitriolated Tartar known
in medicine by the name of _Sal Polychrestum_.

There are evidently two essential differences between this last
experiment and the preceding one. What remains after the deflagration
of Nitre with Sulphur is not a Fixed Alkali: and, moreover, the vapours
emitted in the operation are impregnated with a quantity of the Nitrous
Acid; which is not the case when Nitre is decomposed by any other
inflammable matter which contains no Vitriolic Acid.

The reason of these differences is naturally deducible from what hath
been already said concerning the properties of the Vitriolic and
Nitrous Acids. We have seen that by burning Sulphur its Acid is not
decomposed, but only separated from its Phlogiston. We also know,
that its Acid has a great affinity with Fixed Alkalis. These things
being granted, it follows that, as soon as the Nitrous Acid quits its
Alkaline basis, by deflagrating with the Phlogiston of the Sulphur, the
Acid of this very Sulphur, being set at liberty by that deflagration,
must unite with the Alkaline basis deserted by the Acid of Nitre, and
therewith form a Neutral Salt. Hence, instead of a Fixed Alkali, we
find at the end of the operation a sort of Vitriolated Tartar; the
Acids of Sulphur and of Vitriol being the same, as is evident from what
hath been above said concerning them.

In order to discover the cause of the other phenomenon, we must
recollect two things advanced in our Elements of the Theory; to wit,
that the affinity of the Vitriolic Acid with Fixed Alkalis is greater
than that of the Nitrous Acid; and again, that the Nitrous Acid is not
capable of combining and taking fire with the Phlogiston, but when it
is in the form of a Neutral Salt, that is, when it is united with some
alkaline, earthy, or metallic basis. If these two principles be applied
to the effect in question, the solution is easy and natural. For, in
the deflagration of Nitre with Sulphur, the Phlogiston is not the only
substance capable of separating the Nitrous Acid from its basis: the
Acid of the Sulphur, more and more of which is set at liberty as the
Phlogiston is consumed, is also capable of producing the same effect;
but with this difference, that the portion of the Nitrous Acid which is
detached from its Alkali by the Phlogiston is at the same instant set
on fire and decomposed by that union; whereas the portion thereof which
is separated by the Vitriolic Acid, being when so separated incapable
of uniting with the Phlogiston, and of consuming therewith, is
preserved entire, and rises in vapours, together with that portion of
the Vitriolic Acid which could not unite with the basis of the Nitre.


PROCESS III.

_To decompose Nitre by means of the Vitriolic Acid. The Smoking Spirit
of Nitre._ Sal de duobus. _The Purification of Spirit of Nitre._

Take equal parts of well purified Nitre and Green Vitriol: dry the
Nitre thoroughly, and bruise it to a fine powder. Calcine the Vitriol
to redness: reduce it likewise to a very fine powder; and mingle
these two substances well together. Put the mixture into an earthen
long-neck, or a good glass retort coated, of such a size that it may be
but half full.

Set this vessel in a reverberating furnace covered with its dome; apply
a large glass receiver, having a small hole in its body, stopped with
a little lute. Let this receiver be accurately luted to the retort
with the fat lute, and the joint covered with a slip of canvas smeared
with lute made of quick-lime and the white of an egg. Heat the vessels
very gradually. The receiver will soon be filled with very dense red
vapours, and drops will begin to distil from the nose of the retort.

Continue the distillation, increasing the fire a little when you
observe the drops to follow each other but slowly, so that above two
thirds of a minute passes between them; and, in order to let out the
redundant vapours, open the small hole in the receiver from time to
time. Towards the end of the operation raise the fire so as to make
the retort red. When you find that, even when the retort is red-hot,
nothing more comes over, unlute the receiver, and without delay pour
the liquor it contains into a crystal bottle, and close it with a
crystal stopple ground in its neck with emery. This liquor will be of a
reddish yellow colour, smoking exceedingly, and the bottle containing
it will be constantly filled with red fumes like those observed in the
receiver.


_OBSERVATIONS._

The Vitriolic Acid having a greater affinity with Fixed Alkalis than
with any other substance, the Phlogiston excepted, and being in the
Vitriol united with a ferruginous basis, will naturally quit that basis
to join with the Fixed Alkali of the Nitre; the Acid whereof being
weaker than the Vitriolic, as we have already observed on several
occasions, must needs be thereby expelled from its basis. The Nitre
therefore is decomposed by the Vitriol, and its Acid being set at
liberty, is carried up by the force of the fire.

Indeed the Nitrous Acid, being thus separated from its alkaline
basis, might be expected to combine with the ferruginous basis of
the Vitriol: but as it has, like all other Acids, much less affinity
with Metallic substances than with Alkalis, even a moderate degree of
fire is sufficient to separate it from them. Moreover, this Acid hath
either no effect, or very little, upon iron that has lost much of its
Phlogiston by contracting an union with any Acid; which is the case of
the ferruginous basis of Vitriol.

By the process here delivered a very strong, perfectly dephlegmated,
and vastly smoking Spirit of Nitre is obtained. If the precautions of
drying the Nitre and calcining the Vitriol be neglected, the Acid that
comes over, greedily attracting the water contained in these salts,
will be very aqueous, will not smoke, and will be almost colourless,
with a very slight tinge of lemon.

The fumes of highly concentrated Spirit of Nitre, such as that obtained
by the above process, are light, corrosive, and very dangerous to the
lungs; being no other than the most dephlegmated part of the Nitrous
Acid. The person therefore who unlutes the vessels, or pours the liquor
out of the receiver into the bottle, ought with the greatest caution
to avoid drawing them in with his breath; and for that reason ought to
place himself so that a current of air, either natural or artificial,
may carry them off another way. It is also necessary that care be
taken, during the operation, to give the vapours a little vent every
now and then, by opening the small hole in the recipient; for they are
so elastic, that, if too closely confined, they will burst the vessels.

When the operation is over, you will find a red mass at the bottom of
the retort, cast, as it were, in a mould. This is a Neutral Salt of the
nature of Vitriolated Tartar, resulting from the union of the Acid of
the Vitriol with the Alkaline basis of the Nitre.

The ferruginous basis of the Vitriol, which is mixed with this salt,
gives it the red colour. To separate it therefrom, you must pulverise
it, dissolve it in boiling water, and filter the solution several times
through brown paper; because the ferruginous earth of the Vitriol is
so fine, that some of it will pass through the first time. When the
solution is very clear, and deposites no sediment, let it be set to
shoot, and it will yield crystals of Vitriolated Tartar; to which
Chymists have given the peculiar title of _Sal de duobus_.

In this _Caput mortuum_ we frequently find, besides the ferruginous
earth of Vitriol, a portion of Nitre and Vitriol not decomposed; either
because the two salts were not thoroughly mingled, or because the fire
was not raised high enough towards the end of the operation.

Nitre may also be decomposed, and its acid obtained, by the
interposition of any of the other Vitriols, Alums, Gypsums, Boles,
Clays; in short, by means of any compound in which the Vitriolic Acid
is found, provided it have not a Fixed Alkali for its basis.

The distillers of _Aqua fortis_, who make large quantities at a time,
and who use the least chargeable methods, do their business by the
means of earths impregnated with the Vitriolic Acid; such as Clays
and Boles. With these earths they accurately mix the Nitre from which
they intend to draw their Spirit: this mixture they put into large
oblong earthen pots, having a very short curved neck, which enters a
recipient of the same matter and form. These vessels they place in two
rows opposite to each other in long furnaces, and cover them over with
bricks cemented with Windsor-loam, which serves for a reverberatory:
then they light the fire in the furnace, making it at first very small,
only to warm the vessels; after which they throw in wood, and raise the
fire till the pots grow quite red-hot, in which degree they keep it up
till the distillation is entirely finished.

The Acid of Nitre may also be separated from its basis by means of the
pure Vitriolic Acid. For this purpose the Nitre from which you mean to
extract the Acid must be finely pulverized, put into a glass retort,
and a third of its weight of concentrated Oil of Vitriol poured on it:
the retort must be placed in a reverberating furnace, and a receiver,
like that used in the preceding operation, expeditiously applied.

As soon as the Oil of Vitriol touches the Nitre the mixture grows hot,
and copious red fumes begin to appear: some drops of the Acid come over
even before the fire is kindled in the furnace.

On this occasion the fire must be moderate; because the Vitriolic Acid,
being clogged by no basis, acts upon the Nitre much more briskly, and
with much greater effect, than when it is not pure.

This operation may be performed by a sand-heat; which is a speedy and
commodious way of obtaining the Nitrous Acid. In other respects the
precautions recommended in the preceding experiment must be carefully
observed here, both in distilling the Acid and in taking it out of the
receiver.

The Spirit of Nitre extracted by this method is as strong, and smokes
as much, as that obtained by calcined Vitriol, provided the Oil of
Vitriol made use of be well concentrated; but it is generally tainted
by the admixture of a small portion of the Vitriolic Acid, which,
having no basis of its own to restrain it, is carried up by the heat
before it can lay hold of the basis of the Nitre.

There are several experiments in Chymistry that succeed equally well
whether the Nitrous Acid be or be not thus adulterated with a mixture
of the Vitriolic Acid; but there are some, as we shall see, that
will not succeed without a Spirit of Nitre so mixed. If the Acid be
distilled with a view to such experiments, it must be kept as it is.
But most experiments require the Spirit of Nitre to be absolutely pure;
and if it be intended for such, it must be perfectly cleansed from the
Vitriolic taint.

This is easily effected by mixing your Spirit with very pure Nitre,
and distilling it a second time. The Vitriolic Acid, with which this
Spirit of Nitre is adulterated, coming in contact with a great quantity
of undecomposed Nitre, unites with its Alkaline basis, and expels a
proportionable quantity of the Nitrous Acid.

In the retort made use of to distil the Nitrous Acid, by means of the
pure Vitriolic Acid, is found a _Caput mortuum_, differing from that
left after the distillation of the same Acid by the interposition of
Vitriol, in as much as it contains no red ferruginous earth. This is
a very white saline mass, moulded in the bottom of the retort: if you
pound it, dissolve it in boiling water, and evaporate the solution,
it will shoot into crystals of Vitriolated Tartar: sometimes also
it contains a portion of undecomposed Nitre, which shoots after the
Vitriolated Tartar, because it is much more soluble in water.



CHAP. III.

_Of the_ MARINE ACID.


PROCESS I.

_To extract Sea-salt from Sea-water, and from Brine-springs. Epsom
Salt._

Filter the salt-water from which you intend to extract the salt:
evaporate it by boiling till you see on its surface a dark pellicle:
this consists wholly of little crystals of salt just beginning to
shoot: now slacken the fire, that the brine may evaporate more slowly,
and without any agitation. The crystals, which at first were very
small, will become larger, and form hollow truncated pyramids, the
apices whereof will point downwards, and their bases be even with the
surface of the liquor.

These pyramidal crystals are only collections of small cubical crystals
concreted into this form. When they have acquired a certain magnitude
they fall to the bottom of the liquor. When they come to be in such
heaps as almost to reach the surface of the liquor, decant it from
them, and continue the evaporation till no more crystals of Sea-salt
will shoot.


_OBSERVATIONS._

The Acid of Sea-salt is scarce ever found, either in sea-water or in
the earth, otherwise than united with a fixed alkali of a particular
kind, which is its natural basis; and consequently it is in the form of
a Neutral Salt. This salt is plentifully dissolved in the waters of the
ocean, and when obtained therefrom bears the name of _Sea-salt_. It is
also found in the earth in vast crystalline masses, and is then called
_Sal-gem_: so that Sea-salt and Sal-gem are but one and the same sort
of salt, differing very little from each other, except as to the places
where they are found.

In the earth are also found springs and fountains, whose waters are
strong brines, a great deal of Sea-salt being dissolved in them. These
springs either rise directly from the sea, or run through some mines
of Sal-gem, of which they take up a quantity in their passage.

As the same, or at least nearly the same, quantity of Sea-salt will
continue dissolved in cold water as boiling water will take up, it
cannot shoot, as Nitre does, by the mere cooling of the water in which
it is dissolved: it crystallizes only by the means of evaporation,
which continually lessens the proportion of the water to the salt; so
that it is always capable of containing just so much the less Sea-salt
the more there is crystallized.

The brine should not boil after you perceive the pellicle of little
crystals beginning to form on its surface; for the calmness of the
liquor allows them to form more regularly, and become larger. Nor after
this should the evaporation be hurried on too fast; for a saline crust
would form on the liquor, which, by preventing the vapours from being
carried off, would obstruct the crystallization.

If the evaporation be continued after the liquor ceases to yield any
crystals of Sea-salt, other crystals will be obtained of an oblong
four-sided form, which have a bitter taste, and are almost always
moist. This sort of salt is known by the name of _Epsom Salt_, which
it owes to a salt spring in England, from the water of which it was
first extracted. This salt, or rather saline compound, is a congeries
of Glauber's salt and Sea-salt, in a manner confounded together, and
mixed with some of the Mother of Sea-salt, in which is contained a
kind of bituminous matter. These two Neutral Salts, which constitute
the Epsom Salt, may be easily separated from each other, by means of
crystallization only. Epsom Salt is purgative and bitter; and therefore
named _Sal Catharticum Amarum_, or bitter purging Salts.

There are different methods used in great works for obtaining Sea-salt
out of water in which it is dissolved. The simplest and easiest is that
practised in France, and in all those countries which are not colder.
On the sea-shore they lay out a sort of broad shallow pits, pans, or
rather ponds, which the sea fills with the tide of flood. When the
ponds are thus filled, they stop their communication with the sea, and
leave the water to evaporate by the heat of the sun; by which means
all the salt contained in it necessarily crystallizes. These pits are
called _Salt Ponds_. Salt can be made in this way in the summer-time
only; at least in France, and other countries of the same temperature:
for during the winter, when the sun has less power and rains are
frequent, this method is not practicable.

For this reason, as it often rains in the province of Normandy, the
inhabitants take another way to extract Salt from sea-water. The
labourers employed for this purpose raise heaps of sand on the shore,
so that the tide waters and drenches them when it flows, and leaves the
sand dry when it ebbs. During the interval between two tides of flood
the sun and the air easily carry off the moisture that was left, and
so the sand remains impregnated with all the salt that was contained
in the evaporated water. Thus they let it acquire as much salt as it
can by several returns of flood, and then wash it out with fresh water,
which they evaporate over a fire in leaden boilers.

To obtain the Salt from brine-springs, the water need only be
evaporated: but as several of these springs contain too little salt
to pay the charges that would be incurred, if the evaporation were
effected by the force of fire only, the manufacturers have fallen upon
a less expensive method of getting rid of the greatest part of the
water, and preparing the brine for crystallization, in much less time,
and with much less fire, than would otherwise have been necessary.

The method consists in making the water fall from a certain heighth on
a great many small spars of wood, which divide it into particles like
rain. This is performed under sheds open to all the winds, which pass
freely through this artificial shower. By this means the water presents
to the air a great extent of surface, being indeed reduced almost
entirely to surface, and the evaporation is carried on with great ease
and expedition. The water is raised by pumps to the heighth from which
it is intended to fall[6].

  [6] The Marquis de Montalembert, in a Memoir read before the Academy
  of Sciences, proposes a new method of effecting these evaporations,
  together with some considerable improvements in the structure and
  disposition of the buildings necessary for that purpose. They are
  called by the French _Batiments de Graduation_; which may properly
  enough be rendered _Brine-houses_.


PROCESS II.

_Experiments concerning the decomposition of Sea-salt, by means of the
Phlogiston._ Kunckel_'s Phosphorus_.

"Of pure urine that has fermented five or six days take a quantity
in proportion to the quantity of phosphorus you intend to make:
it requires about one third part of a hogshead to make a dram of
Phosphorus. Evaporate it in iron pans, till it become clotted, hard,
black, and nearly like chimney-soot; at which time it will be reduced
to about a sixtieth part of its original weight before evaporation.

"When the urine is brought to this condition put it in several portions
into so many iron pots, under which you must keep a pretty brisk fire
so as to make their bottoms red, and stir it incessantly till the
volatile salt and the fetid oil be almost wholly dissipated, till the
matter cease to emit any smoke, and till it smell like peach-blossoms.
Then put out the fire, and pour on the matter, which will now be
reduced to a powder, somewhat more than twice its weight of warm
water. Stir it about in this water, and leave it to soak therein for
twenty-four hours. Pour off the water by inclination; dry the drenched
matter, and pulverize it. The previous calcination carries off from the
matter about a third of its weight, and the lixiviation washes out half
the remainder.

"With what remains thus calcined, washed, and dried, mix half its
weight of gravel, or yellow freestone rasped, having sifted out and
thrown away all the finest particles. River sand is not proper on this
occasion, because it flies in a hot fire. Then add to this mixture a
sixteenth part of its weight of charcoal, made of beech, or of any
other wood except oak, because that also flies. Moisten the whole
with as much water as will bring it to a stiff paste, by working and
kneading it with your hands: now introduce it into your retort, taking
care not to daub its neck. The retort must be of the best earth, and of
such a size, that when your matter is in it, a full third thereof shall
still be empty.

"Place your retort, thus charged, in a reverberating furnace, so
proportioned, that there may be an interval of two inches all round
between the sides of the furnace and the bowl of the retort, even where
it contracts to form the neck, which should stand inclined at an angle
of sixty degrees. Stop all the apertures of the furnace, except the
doors of the fire-place and ash-hole.

"Fit on to the retort a large glass ballon two thirds full of water,
and lute them together, as in distilling the Smoking Spirit of Nitre.
In the hinder part of this ballon, a little above the surface of the
water, a small hole must be bored. This hole is to be stopped with a
small peg of birch-wood, which must slip in and out very easily, and
have a small knob to prevent its falling into the ballon. This peg
is to be pulled out from time to time, that by applying the hand to
the hole it may be known whether the air, rarefied by the head of the
retort, issues out with too much or too little force.

"If the air rushes out with too much rapidity, and with a hissing
noise, the door of the ash-hole must be entirely shut, in order to
slacken the fire. If it do not strike pretty smartly against the
hand, that door must be opened wider, and large coals thrown into the
fire-place to quicken the fire immediately.

"The operation usually lasts four and twenty hours; and the following
signs shew that it will succeed, provided the retort resist the fire.

"You must begin the operation with putting some unlighted charcoal in
the ash-hole, and a little lighted charcoal at the door thereof, in
order to warm the retort very slowly. When the whole is kindled, push
it into the ash-hole, and close the door thereof with a tile. This
moderate heat brings over the phlegm of the mixture. The same degree of
fire must be kept up four hours, after which some coals may be laid on
the grate of the fire-place, which the fire underneath will kindle by
degrees. With this second heat brought nearer the retort, the ballon
grows warm, and is filled with white vapours, which have the smell of
fetid oil. In four hours after, this vessel will grow cool and clear;
and then you must open the door of the ash-hole one inch, throw fresh
coals into the fire-place every three minutes, and every time shut the
door of it, lest the cold air from without should strike against the
bottom of the retort and crack it.

"When the fire has been kept up to this degree for about two hours, the
inside of the ballon begins to be netted over with a volatile salt of a
singular nature, which cannot be driven up but by a very violent fire,
and which smells pretty strong of peach-kernels. Care must be taken
that this concrete salt do not stop the little hole in the ballon: for
in that case it would burst, the retort being then red-hot, and the
air exceedingly rarefied. The water in the ballon, being heated by the
vicinity of the furnace, exhales vapours which dissolve this sprigged
salt, and the ballon clears up in half an hour after it has ceased
rising.

"In about three hours from the first appearance of this salt, the
ballon is again filled with new vapours, which smell like Sal Ammoniac
thrown upon burning coals. They condense on the sides of the receiver
into a salt which is not branched like the former, but appears in long
perpendicular streaks, which the vapours of the water do not dissolve.
These white vapours are the fore-runners of the Phosphorus, and a
little before they cease to rise they lose their first smell of Sal
Ammoniac, and acquire the odour of garlic.

"As they ascend with great rapidity, the little hole must be frequently
opened, to observe whether the hissing be not too strong: for, in that
case, it would be necessary to shut the door of the ash-hole quite
close. These white vapours continue two hours. When you find they cease
rising, make a small passage through the dome, by opening
some of its registers, that the flame may just begin to draw. Keep up
the fire in this mean state till the first volatile Phosphorus begin to
appear.

"This appears in about three hours after the white vapours first begin
to rise. In order to discover it, pull out the little birchen peg once
every minute, and rub it against some hot part of the furnace, where it
will leave a trail of light, if there be any Phosphorus upon it.

"Soon after you observe this sign, there will issue out through the
little hole of the ballon a stream of blueish light, which continues of
a greater or shorter extent to the end of the operation. This stream or
spout of light does not burn. If you hold your finger against it for
twenty or thirty seconds, the light will adhere to it; and if you rub
that finger over your hand, the light will besmear it, and render it
luminous.

"But from time to time this streamer darts out to the length of seven
or eight inches, snapping and emitting sparks of fire; and then it
burns all combustible bodies that come in its way. When you observe
this, you must manage the fire very warily, and shut the door of the
ash-hole quite close, yet without ceasing to throw coals into the
fire-place every two minutes.

"The Volatile Phosphorus continues two hours; after which the little
spout of light contracts to the length of a line or two: and now is the
time for pushing your fire to the utmost: immediately set the door of
the ash-hole wide open, throw billets of wood into it, unstop all the
registers of the reverberatory, supply the fire-place with large coals
every minute: in short, for six or seven hours all the inside of the
furnace must be kept of a white heat, so that the retort shall not be
distinguishable.

"In this fierce extremity of heat the true Phosphorus distils like an
oil, or like melted wax: one part thereof floats on the water in the
recipient, the other falls to the bottom. At last, the operation is
known to be quite over when the upper part of the ballon, in which the
volatile Phosphorus appears condensed in a blackish film, begins to
grow red: for this shews that the Phosphorus is burnt where the red
spot appears. You must now stop all the registers, and shut all the
doors of the furnace, in order to smother the fire; and then close
up the little hole in the ballon with fat lute or bees-wax. In this
condition the whole must be left for two days; because, the vessels
must not be separated till they are perfectly cold, lest the Phosphorus
should take fire.

"As soon as the fire is out, the ballon, which is then in the dark,
presents a most agreeable object: all the empty part thereof above
the water seems filled with a beautiful blue light: which continues
for seven or eight hours, or as long as the ballon keeps warm, never
disappearing till it is cooled.

"When the furnace is quite cold take out the vessels, and separate them
from each other as neatly as possible. With a linen cloth wipe away
all the black stuff you find in the mouth of the ballon; for if that
filth should mix with the Phosphorus, it would hinder it from being
transparent when moulded. This must be done with great expedition:
after which pour into the ballon two or three quarts of cold water, to
accelerate the precipitation of the Phosphorus that swims at top. Then
agitate the water in the ballon, to rinse out all the Phosphorus that
may stick to the sides: pour out all the water thus shaken and turbid,
into a very clean earthen pan, and let it stand till it grows clear.
Then decant this first useless water, and on the blackish sediment,
left at the bottom of the pan, pour some boiling water to melt the
Phosphorus; which thereupon unites with the fuliginous matter, or
volatile Phosphorus, that precipitated with it, both together forming a
mass of the colour of slate. When this water, in which you have melted
the Phosphorus, is cool enough, take out the Phosphorus, throw it into
cold water, and therein break it into little bits in order to mould it.

"Then take a matras, having a long neck somewhat wider next the body
than at its mouth: cut off half the body, so as to make a funnel of
the neck-part, the smaller end of which must be stopped with a cork.
The first mould being thus prepared, plunge it endwise, with its
mouth uppermost, in a vessel full of boiling water, and fill it with
that water. Into this funnel throw the little bits of your slate-like
mass, which will melt again in this hot water, and fall so melted to
the bottom of the tube. Stir this melted matter with an iron wire, to
promote the separation of the Phosphorus from the fuliginous matter
with which it is fouled, and which, being less ponderous than the
Phosphorus, will gradually rise above it towards the upper part of the
cylinder.

"Keep the water in the vessel as hot as at first, till, on taking out
the tube, you see the Phosphorus clean and transparent. Let the clear
tube cool a little, and then set it in cold water, where the Phosphorus
will congeal as it cools. When it is perfectly congealed, pull out the
cork, and with a small rod, near as big as the tube, push the cylinder
of Phosphorus towards the mouth of the funnel, where the feculency
lies. Cut off the black part of the cylinder, and keep it apart: for
when you have got a quantity thereof, you may melt it over again in the
same manner, and separate the clean Phosphorus which it still contains.
As to the rest of the cylinder which is clean and transparent, if you
intend to mould it into smaller cylinders, you may cut it in slices,
and melt it again by the help of boiling water in glass tubes of
smaller dimensions."


_OBSERVATIONS._

This process for making Phosphorus is copied from the Memoirs of the
Academy of Sciences for the Year 1737; where it is described by M.
Hellot, with so much accuracy, clearness, and precision, that I thought
I could not do better than transcribe it, without departing from the
author's own expressions, for the sake of such as may not have those
Memoirs. We shall take occasion, in these observations, to point out
some essential circumstances which I have omitted in the description
of the Process, that I might not break the connection between the
phenomena that happen in the course of this experiment.

It is proper to observe, in the first place, that one of the most usual
causes of miscarriage in this operation is a defect of the requisite
qualities in the retort employed. It is absolutely necessary to have
that vessel made of the best earth, and so well made that it shall be
capable of resisting the utmost violence of fire, continued for a very
long time; as appears by the description of the process. The retorts
commonly sold by potters, and other earthen-ware men, are not fit for
this operation; and M. Hellot was obliged to send to Hesse-Cassel for
such as he wanted.

We shall, in the second place, observe with M. Hellot, that, "before
you set your retort in the furnace, it is proper to make an essay of
your matter, to see if there be reason to hope for success. For this
purpose put about an ounce thereof into a small crucible, and heat it
till the vessel be red. The mixture, after having smoked, ought to chop
or crack without puffing up, or even rising in the least. From these
cracks will issue undulating flames, white and blueish, darting upwards
with rapidity. This is the first volatile Phosphorus, which occasions
all the danger of the operation. When these first flashes are over,
increase the heat of your matter by laying a large live coal upon the
crucible. You will then see the second Phosphorus, like a luminous,
steady vapour, of a colour inclining to violet, covering the whole
surface of the matter: it continues for a very long time, and diffuses
a smell of garlic, which is the distinguishing odour of the Phosphorus
you are seeking.

"When this luminous vapour is entirely gone, pour the red hot matter
out of the crucible upon an iron plate. If you do not find one drop of
salt in fusion, but that, on the contrary, the whole falls readily into
powder, it is a proof that your matter was sufficiently lixiviated, and
that it contains no more fixed Salt, or Sea-salt, if you will, than
is requisite. If you find on the plate a drop of salt coagulated, it
shews that there is too much left in, and that there is danger of your
miscarrying in the operation; because the redundant salt would corrode,
and eat through the retort. In this case your matter must be washed
again, and then sufficiently dried."

Our third observation shall be concerning the furnace proper to be
employed in this operation. This furnace must be so constructed, that,
within a narrow compass it may give a heat at least equal to that of
a glass-house furnace, or rather greater, especially during the last
seven or eight hours of the operation. M. Hellot in his Memoir gives an
exact description of such a furnace.

"As certain accidents may happen in the course of the operation, some
precautions are to be taken against them. For instance, if the ballon
should break while the Phosphorus is distilling, and any of it should
fall on combustible bodies, it would set them on fire, and probably
burn the laboratory, because it is not to be extinguished without the
greatest difficulty. The furnace must therefore be erected under some
vault, or upon a bed of brick-work raised under some chimney that draws
well: nor must any furniture or utensil of wood be left near it. If a
little flaming Phosphorus should fall on a man's legs or hands, in less
than three minutes it would burn its way to the very bone. In such a
case nothing but urine will stop its progress.

"If the retort crack while the Phosphorus is distilling, there is an
unsuccessful end of your operation. It is easy to perceive this by the
stink of garlic which you will smell about the furnace; and moreover,
the flame that issues through the apertures of the reverberatory will
be of a beautiful violet colour. The Acid of Sea-salt always gives this
colour to the flame of such matters as are burnt along with it. But
if the retort break before the Phosphorus hath made its appearance,
its contents may be saved by throwing a number of cold bricks into the
fire-place, and upon them a little water to quench the fire at once."
All these useful observations we owe also to M. Hellot.

The Phosphorus here described was first discovered by a citizen
of Hamburgh, named Brandt, who worked upon urine in search of the
Philosopher's stone. Afterwards two other skilful Chymists, who knew
nothing more of the process, than that Phosphorus was obtained from
urine, or, in general, from the human body, likewise endeavoured
to discover it; and each of them separately did actually make the
discovery. These two Chymists were Kunckel and Boyle.

The former perfected the discovery, and found out a method of making it
in considerable quantities at a time; which occasioned it to be called
_Kunckel's Phosphorus_. The other, who was an English gentleman, had
not time to bring his discovery to perfection, and contented himself
with lodging a voucher of his having discovered it in the hands of the
Secretary of the Royal Society of London, who gave him a certificate
thereof.

"Though Brandt," says M. Hellot, "who had before this sold his secret
to a Chymist named Krafft, sold it afterwards to several other persons,
and even at a very low rate; and though Mr. Boyle published the process
for making it; yet it is extremely probable that both of them kept in
their own hands the master-key; I mean, _the particular management
necessary to make the operation succeed_: for, till Kunckel found it
out, no other Chymist ever made any considerable quantity thereof,
except Mr. Godfrey Hankwitz, an English Chymist, to whom Mr. Boyle
revealed the whole mystery.

"Nevertheless," continues he, "we are very far from alledging that
all those who have described this operation meaned to impose upon the
world: but we conceive that most of them having observed luminous
vapours in the ballon, and some sparks about the juncture of the
vessels, were contented with those appearances. And thus it came to
pass, that, after Kunckel and Boyle died, Mr. Godfrey Hankwitz was the
only Chymist that could supply Europe therewith; on which account it is
likewise very well known by the name of _English Phosphorus_."

Almost all the Chymists consider Phosphorus as a substance consisting
of the Acid of Sea-salt combined with the Phlogiston, in the same
manner as Sulphur consists of the Vitriolic Acid combined with the
Phlogiston. This opinion is founded on the following principles.

First, Urine abounds with Sea-salt, and contains also a great deal of
Phlogiston; now these are the ingredients of which they conjecture
Phosphorus to be composed.

Secondly, Phosphorus has many of the properties of Sulphur; such
as being soluble in oils; melting with a gentle heat; being very
combustible; burning without any soot; giving a vivid and blueish
flame; and lastly, leaving an acid liquor when burnt: sensible proofs
that it differs from Sulphur in nothing but the nature of its Acid.

Thirdly, this Acid of Phosphorus, being mixed with a solution of silver
in Spirit of Nitre, precipitates the silver, and this precipitate is
a true _Luna cornea_, which appears to be more volatile even than the
common sort; as M. Hellot tells us, who made the experiment. This
fact proves incontestably that the Acid of Phosphorus is of the same
nature with that of Sea-salt: for all Chymists know that the property
of precipitating silver in a _Luna cornea_ belongs to the Marine Acid
only.

Fourthly, M. Stahl observes, that, if Sea-salt be cast on live coals,
they instantly burn with great activity; then they emit a very
vivid flame, and are much sooner consumed than if none of this salt
had touched them; that Sea-salt in substance, which will bear the
violence of fire a considerable time when fused in a crucible, without
sustaining any sensible diminution, yet evaporates very quickly, and is
reduced to white flowers, by the immediate contact of burning coals;
and, lastly, that the flame which rises on this occasion is of a blue
colour inclining to violet, especially if it be not thrown directly
on the coals themselves, but kept in fusion amidst burning coals, in
a crucible so placed that the vapour of the Salt may join with the
enflamed Phlogiston as it rises from the coals.

These experiments of M. Stahl's prove, that the Phlogiston acts upon
the acid of Sea-salt, even while it is combined with its alkaline
basis. The flame that appears on this occasion may be considered as an
imperfect Phosphorus: and indeed its colour is exactly like that of
Phosphorus.

All the facts above related evince, that the Acid of Phosphorus is akin
to that of Sea-salt; or rather that it is the very same. But there are
other facts which prove that this Acid undergoes some change at least,
some peculiar preparation, before it enters into the composition of a
true Phosphorus, and that, when extricated therefrom by burning, it is
not a pure Acid of Sea-salt, but is still adulterated with a mixture of
some other substance, which makes it considerably different from that
Acid. For these observations we are obliged to M. Marggraff, of the
Academy of Sciences at Berlin, a celebrated Chymist. I shall presently
give an account of his principal experiments as succinctly as possible.

M. Marggraff hath also published a process for making Phosphorus, and
assures us, that by means thereof we may obtain in less time, with less
heat, less trouble, and less expence, a greater quantity of Phosphorus
than by any other method. His operation is this:

He takes two pounds of Sal Ammoniac in powder, which he mixes
accurately with four pounds of Minium. This mixture he puts into
a glass retort, and with a graduated fire draws off a very sharp,
volatile, urinous spirit.

We observed in our theoretical Elements, that some metallic substances
have the property of decomposing Sal Ammoniac, and separating its
volatile Alkali; concerning which phenomenon we there gave our opinion.
Minium, which is a calx of lead, is one of those metallic substances.
In this experiment it decomposes the Sal Ammoniac, and separates its
volatile Alkali; what remains in the retort is a combination of the
Minium with the Acid of the Sal Ammoniac, which is well known to be
the same with the Marine Acid; and consequently the residue of this
operation is a sort of _Plumbum corneum_.

The quantity thereof is four pounds eight ounces. Of this he mixes
three pounds with nine or ten pounds of urine, that has stood
putrefying for two months, evaporated to the consistence of honey.
These he mixes by little and little in an iron pan over the fire,
stirring the mixture from time to time. Then he adds half a pound of
charcoal-dust, and evaporates the matter, kept continually stirring,
till the whole be brought to a black powder. He next distils the
mixture in a glass retort with degrees of fire, which he raises towards
the end so as to make the retort red-hot, in order to expel all the
urinous spirit, superfluous oil, and ammoniacal salt. The distillation
being finished, there remains nothing in the retort but a very friable
_caput mortuum_.

This remainder he pulverises again, and throws a pinch thereof on
live coals, thereby to discover whether or no the matter be rightly
prepared, and in order for yielding Phosphorus. If it be so, it
presently emits an arsenical odour, and a blue undulating flame, which
passes over the surface of the coals like a wave.

Being thus assured of the success of his operation, he puts one half
of his matter in three equal parts, into three small earthen German
retorts, capable of holding about eighteen ounces of water a-piece.
These three retorts, none of which is above three quarters full, he
places together in one reverberatory furnace, built much like those we
have described, except that it is so constructed as to hold the three
retorts disposed in one line. To each retort he lutes a recipient
something more than half full of water, ordering the whole in such a
manner, that the noses of his retorts almost touch the surface of the
water.

He begins the distillation with warming the retorts slowly, for about
an hour, by a gentle heat. When that time is elapsed he raises the fire
gradually, so that in half an hour more the coals begin to touch the
bottoms of the retorts. He continues throwing coals into the furnace by
little and little, till they rise half way the heighth of the retorts;
and in this he employs another half hour. Lastly, in the next half hour
he raises the coals above the bowls of the retorts.

Then the Phosphorus begins to ascend in clouds: on this he instantly
increases the heat of the fire as much as possible, filling the furnace
quite up with coals, and making the retorts very red. This degree of
fire causes the Phosphorus to distil in drops, which fall to the bottom
of the water. He keeps up this intense heat for an hour and half, at
the end of which the operation is finished; so that it lasts but four
hours and an half in all: nay, he further assures us, that an artist
well versed in managing the fire, may perform it in four hours only. In
the same manner he distils the second moiety of his mixture in three
other such retorts.

The advantage he finds in making use of several small retorts, instead
of a single large one, is, that the heat penetrates them with more
ease, and the operation is performed with less fire, and in less time.
He purifies and moulds his Phosphorus much in the same manner as M.
Hellot does. From the quantity of ingredients above-mentioned, he
obtains two ounces and a half of fine crystalline moulded Phosphorus.

M. Marggraff considering, as a consequence of the experiments above
related, that a highly concentrated Acid of Sea-salt contributes
greatly towards the formation of Phosphorus, proceeded to try several
other experiments, in which he employed that Acid in a state of
combination with other bases. He mixed, for instance, an ounce of _Luna
cornea_ with an ounce and half of putrefied and inspissated urine, and
from the mixture obtained a very beautiful Phosphorus.

In short, the several experiments mentioned having thoroughly persuaded
him that the Acid of Sea-salt, provided it were highly concentrated,
would combine with the Phlogiston as readily as the Vitriolic Acid
does, he resolved to try whether he could not make Phosphorus with
matters containing that Acid and the Phlogiston, without making use of
any urine.

With this view he made a great number of different trials, wherein he
employed Sea-salt in substance, Sal Ammoniac, Plumbum corneum, Luna
cornea, fixed Sal Ammoniac, otherwise called _Oil of Lime_. These
several substances, all of which contain the Acid of Sea-salt, he mixed
with sundry matters abounding in Phlogiston, different vegetable coals,
and even animal matters, such as the oil of hartshorn, human blood,
_&c._ varying the proportions of these substances many different ways,
without ever being able to produce a single atom of Phosphorus: which
gave this able Chymist just cause to suspect, that the Marine Acid,
while pure and crude, is not capable of combining with the Phlogiston
in the manner requisite to form a Phosphorus; that for this purpose it
is necessary the Acid would have contracted a previous union with some
other matter; and that the Acid found in urine hath probably undergone
the necessary change. M. Marggraff is of opinion that the matter, which
by its union renders the Marine Acid capable of entering into the
composition of Phosphorus, is a sort of exceedingly subtle vitrifiable
earth. The experiments he made upon the Acid of Phosphorus, will shew
that his notion is not altogether groundless. M. Marggraff having let
some urine, evaporated to the consistence of honey, stand quiet in a
cool place, obtained from it, by crystallization, a Salt of a singular
nature. By distilling this urine afterwards, he satisfied himself that
it yielded him much less Phosphorus than urine from which no Salt had
been extracted; and as it cannot be entirely deprived of this Salt, he
thinks that the small quantity of Phosphorus, which this urine yielded
him, came from the Salt that was still left in it.

Further, he distilled this salt separately with lamp-black, and
obtained from it a considerable quantity of very fine Phosphorus. He
even mixed _Luna cornea_ with this Salt, in order to see whether it
would not increase the quantity of his Phosphorus; but without success:
whence he concluded, that in this Saline matter resides the true Acid
that is fit to enter into the composition of Phosphorus. This opinion
is confirmed by several experiments on the Acid of Phosphorus, which he
found to have some properties resembling those of this Salt.

The Acid of Phosphorus seems to be more fixed than any other: and
therefore if you would separate it, by burning, from the Phlogiston
with which it is united, there is no occasion for such an apparatus
of vessels as is employed for obtaining the Spirit of Sulphur. For
this Acid will remain at the bottom of the vessel in which you burn
your Phosphorus: indeed, if it be urged by the force of fire, its most
subtile part evaporates, and the remainder appears in the form of a
vitrified matter.

This Acid effervesces with fixed and volatile Alkalis, and therewith
forms Neutral Salts; but very different from Sea-salt, and from Sal
Ammoniac. That which has a fixed Alkali for its basis does not crackle
when thrown on burning coals; but swells and vitrifies like Borax. That
which has a volatile Alkali for its basis shoots into long pointed
crystals; and, being urged by fire in a retort, lets go its volatile
alkali, a vitrified matter remaining behind. This Salt is like that
above-mentioned, as obtained from urine and yielding Phosphorus.

It appears from the experiments adduced, that the Acid of Phosphorus
tends always to vitrification; which proves that it is not pure, and
gave M. Marggraff cause to think that it is altered by the admixture of
a very subtile vitrifiable earth.

M. Marggraff also obtained Phosphorus from several vegetable substances
which we use every day for food. This gives him occasion to conjecture,
that the Salt requisite to the formation of Phosphorus exists in
vegetables, and passes from thence into the animals that feed upon them.

Lastly, he concludes his dissertation by informing us of a very
important truth, _viz._ That the Acid obtained from Phosphorus, by
burning it, will serve to form Phosphorus anew; for which purpose it
need only be combined with some charred coal, such as lamp-black, and
distilled.

From what hath been said on this subject it is plain, that the Chymists
have a great many curious and interesting inquiries to make concerning
Phosphorus, and particularly concerning its Acid.

I shall conclude this article with an account of certain properties of
Phosphorus which I have not yet mentioned.

Phosphorus dissolves by lying exposed to the air. What water cannot
effect, says M. Hellot, or at least requires eight or ten years to
bring about, the moisture of the air accomplishes in ten or twelve
days; whether it be that the Phosphorus takes fire in the air, and
the inflammable part evaporating, almost entirely, leaves the Acid of
the Phosphorus naked, which, like all other Acids, when exceedingly
concentrated, is very greedy of moisture; or else that the moisture
of the air, being water divided into infinitely fine particles, is so
subtile as to find its way through the pores of the Phosphorus, into
which the grosser particles of common water can by no means insinuate
themselves.

Phosphorus heated by the vicinity of fire, or by being any way rubbed,
soon takes fire and burns fiercely. It is soluble in all Oils and in
Ether, giving to those liquors the property of appearing luminous when
the bottle containing the solution is opened. Being boiled in water,
it likewise communicates thereto this luminous quality. M. Morin,
Professor at Chartres, is the author of this observation.

The late Mr. Grosse, a celebrated Chymist of the Academy of Sciences,
observed, that Phosphorus being dissolved in essential oils
crystallizes therein. These crystals take fire in the air, either when
thrown into a dry vessel, or wrapt up in a piece of paper. If they
be dipped in Spirit of Wine, and taken out immediately, they do not
afterwards take fire in the air: they smoke a little, and for a very
short time, but hardly waste at all. Though some of them were left in
a spoon for a fortnight, they did not seem to have lost any thing of
their bulk: but when the spoon was warmed a little they took fire, just
like common Phosphorus that had never been dissolved and crystallized
in an essential Oil.

M. Marggraff, having put a dram of Phosphorus, with an ounce of highly
concentrated Spirit of Nitre, into a glass retort, observed, that,
without the help of fire, the Acid dissolved the Phosphorus; that part
of the Acid came over into the recipient which was luted to the retort;
that, at the same time, the Phosphorus took fire, burnt furiously, and
burst the vessels with explosion. Nothing of this kind happens when any
of the other Acids, though concentrated, are applied to Phosphorus.


PROCESS III.

 _To decompose Sea-salt by means of the Vitriolic Acid. Glauber's Salt.
 The Purification and Concentration of Spirit of Salt._

Put the Sea-salt from which you mean to extract the Acid into an
unglazed earthen pipkin, and set it amidst live coals. The Salt will
decrepitate, grow dry, and fall into a powder. Put this decrepitated
Salt into a tubulated glass retort, leaving two thirds thereof empty.
Set the retort in a reverberating furnace; apply a receiver like that
used in distilling the Smoking Spirit of Nitre, and lute it on in the
same manner, or rather more exactly if possible. Then through the
hole, in the upper convexity of the retort, pour a quantity of highly
concentrated Oil of Vitriol, equal in weight to about a third part
of your Salt, and immediately shut the hole very close with a glass
stopple, first ground therein with emery so as to fit it exactly.

As soon as the Oil of Vitriol touches the Salt, the retort and receiver
will be filled with abundance of white vapours; and soon after,
without lighting any fire in the furnace, drops of a yellow liquor
will distil from the nose of the retort. Let the distillation proceed
in this manner without fire, as long as you perceive any drops come:
afterwards kindle a very small fire under the retort, and continue
distilling and raising the fire by very slow degrees, and with great
caution, to the end of the distillation; which will be finished before
you have occasion to make the retort red-hot. Unlute the vessels, and
without delay pour the liquor, which is a very smoking Spirit of Salt,
out of the receiver into a crystal bottle, like that directed for the
smoking Spirit of Nitre.


_OBSERVATIONS._

Sea-Salt, as hath been already said, is a Neutral Salt composed of an
Acid, which differs from those of Vitriol and Nitre, combined with a
fixed Alkali that has some peculiar properties; but does not vary from
the others in its affinities. This Salt therefore, as well as Nitre,
must be decomposed by the Vitriolic Acid; which accordingly is the
case in the process here described. The Vitriolic Acid unites with the
Alkaline basis of the Sea-salt, and separates its Acid; and that with
much greater facility than it expels the Nitrous Acid from its Alkaline
basis, because the Acid of Sea-salt has not so great an affinity as the
Nitrous Acid with Fixed Alkalis.

As a highly concentrated Oil of Vitriol is used on this occasion, and
as the Sea-salt is previously dried and decrepitated, the Acid obtained
from it by distillation is very free from phlegm, and always smokes,
even more violently than the strongest Acid of Nitre. The vapours of
this Acid are also much more elastic and more penetrating than those
of the Nitrous Acid: on which account this distillation of the smoking
Spirit of Salt is one of the most difficult, most laborious, and most
dangerous operations in Chymistry.

This process requires a tubulated retort, that the Oil of Vitriol
may be mixed with the Sea-salt after the receiver is well luted to
the retort, and not before: for, as soon as these two matters come
together, the Spirit of Salt rushes out with so much impetuosity, that,
if the vessels were not luted at the time, the copious vapours that
would issue through the neck of the ballon would so moisten it, as well
as the neck of the retort, that it would be impracticable to apply the
lute and secure the joint as the operation requires. Moreover, the
operator would be exposed to those dangerous fumes, which, on this
occasion, rush out, and enter the lungs, with such incredible activity
as to threaten instant suffocation.

Having said so much of the elasticity and activity of the fumes of
Spirit of Salt, it is needless to insist upon the necessity of giving
vent to the vessels from time to time, by opening the little hole of
the ballon: indeed the best way to prevent the loss of a great many
vapours, on this occasion, is to employ adopters, and cover them with
wet canvas, which will cool and condense the vapours they contain.

When the operation is finished, we find a white, saline mass at the
bottom of the retort as in a mould. If this mass be dissolved in water,
and the solution crystallized, it yields a considerable quantity of
Sea-salt that hath not been decomposed, and a Neutral Salt consisting
of the Vitriolic Acid united with the Alkaline basis of that part
which hath been decomposed. This Neutral Salt, which bears the name of
_Glauber_ its inventor, differs from Vitriolated Tartar, or the _Sal de
duobus_, which remains after distilling the Nitrous Acid, especially in
that it is more fusible, more soluble in water, and hath its crystals
differently figured. But as in these two Salts the Acid is the same,
the differences that appear between them must be attributed to the
peculiar nature of the basis of Sea-salt.

Spirit of Salt drawn by the process above described is tainted with a
small mixture of the Vitriolic Acid, carried up by the force of fire
before it had time to combine with the Alkali of the Sea-salt; which
happens likewise to the Nitrous Acid procured in the same manner.
If you desire to have it pure, and absolutely free from the Acid of
Vitriol, it must be distilled a second time from Sea-salt, as the Acid
of Nitre was before directed to be distilled again from fresh Nitre, in
order to purify it from any Vitriolic taint.

Sea-salt, as well as Nitre, may be decomposed by any combination of
the Vitriolic Acid with a metallic or earthy substance: but it is
proper to observe, that if you distil Spirit of Salt by means of Green
Vitriol, the operation will not succeed so well as when Spirit of Nitre
is distilled in the same manner: less Spirit is obtained, and a much
fiercer fire is required.

The cause of this lies in the property which the Acid of Sea-salt
possesses of dissolving Iron, even when deprived of a part of its
Phlogiston by having contracted an union with another Acid; so that it
is no sooner dislodged from its own basis by the Vitriolic Acid, than
it unites with the ferruginous basis of the Vitriol, from which it
cannot be separated but by a most violent fire. This is the consequence
more especially when calcined Vitriol is made use of: for moisture,
as we shall presently see, greatly facilitates the separation of the
Marine Acid from those substances with which it is united.

When you do not desire a highly dephlegmated and smoking Spirit of
Salt, you may distil with the additament of any earth containing the
Vitriolic Acid; as Clay, for instance, or Bole. To this end one part
of Sea-salt, slightly dried and reduced to a fine powder, must be
accurately mingled with two parts of the earth you intend to employ
likewise pulverized; of this mixture make a stiff paste with a proper
quantity of rain water, and having formed little balls thereof about
the size of a hazel nut, let them dry in the sun; when dry, put them
into a stone or coated glass retort, leaving a third part thereof
empty; set this vessel in a reverberating furnace, covered with its
dome; apply a receiver, which need not be luted on for some time; and
heat the vessels very slowly. At first an insipid water will rise,
which must be thrown away: afterwards the Spirit of Salt will appear
in white clouds. Now lute your vessels, and raise the fire by degrees;
which, towards the end must be pushed to the utmost extremity. The
operation is known to be finished when no drops fall from the nose of
the retort, the receiver cools, and the white vapours that filled it
are seen no more.

The Spirit of Salt obtained by the process here delivered does not
smoke, and contains much more phlegm than that which is distilled by
means of the concentrated Oil of Vitriol; because the earth, though
dried in the sun, still retains a great deal of moisture, which
commixes with the Acid of the Sea-salt. Consequently it is much easier
to collect its vapours; so that this operation is attended with much
less trouble than the other. Nevertheless it is adviseable to proceed
gently; to apply but little heat at first, and to unstop every now and
then the small hole of the receiver: for a quantity of the vapours of
Spirit of Salt, even when weakened by the admixture of water, is very
apt to burst the vessels.

A much greater degree of fire is necessary to raise the Spirit of Salt
by this latter process, than by that in which the pure Vitriolic Acid
is employed: for, as fast as the Spirit of Salt is dislodged from its
own basis, by the Vitriolic Acid contained in the earth made use of,
part of it joins that earth, and cannot be separated from it without
the most violent heat.

A Spirit of Salt that shall not smoke may also be obtained by means of
the pure Vitriolic Acid. Spirit of Vitriol, or Oil of Vitriol, lowered
with a good deal of water, will do the business.

Some Chymists direct a little water to be placed in the receiver, when
Spirit of Salt is to be distilled by the intermedium of concentrated
Oil of Vitriol, in order to make the acid vapours condense more
readily. By this means indeed some of the inconveniencies attending
the distillation of smoking Spirit of Salt may be avoided: but, on the
other hand, the acid vapours being absolutely suffocated by the water
as fast as they come over, the Spirit of Salt obtained by this method
will be no less aqueous than that procured by the interposition of
earths: so that here is an expence to no manner of purpose. Therefore,
when a Spirit of Salt is desired that shall not smoke, it is best
to employ an additament of earth; and that so much the rather as
the Marine Acid obtained by this means is purer and freer from any
Vitriolic taint, for the reasons already assigned.

Part of the Acid of Sea-salt may be separated from its Alkaline basis
by the force of fire alone, without the intervention of any other body.
With this view the Salt must be put into the retort without being
dried. At first an insipid water rises; but it gradually becomes acid,
and hath all the properties of Spirit of Salt. When the Salt in the
retort is grown perfectly dry, nothing more can be forced over by any
degree of heat whatever. If you would obtain more Acid from the same
Salt, you must take it out of the retort, where you will find it in a
lump, reduce it to powder, and expose it to the air for some time, that
it may attract the moisture thereof; or else wet it at once with some
rain water, and distil as before. You will again have an insipid water,
and a little Spirit of Salt; which will in like manner cease to rise
when the Salt in the retort becomes dry. This operation may be repeated
as often as shall be thought proper: and perhaps it may be possible to
decompose Sea-salt entirely by means thereof, without the interposition
of any other body. The Spirit of Salt thus obtained is exceeding weak,
in small quantity, and loaded with much water.

This experiment proves, that moisture greatly facilitates the
separation of the Acid of Sea-salt from the matters with which it is
united: and this is the reason that, in distilling Spirit of Salt with
the additament of an earth, the operation requires much less fire
at the beginning, while the earth and salt retain a great deal of
humidity, than towards the end, when they begin to grow dry.

After the operation there remains in the retort a saline and earthy
mass, which contains, 1. Some entire Sea-salt that has suffered no
decomposition; 2. A Glauber's Salt which is, as we said before, a
Neutral Salt consisting of the Vitriolic Acid united with the Alkaline
basis of the Sea-salt, from which it hath expelled its proper Acid; 3.
Part of the earth used as an intermedium, still retaining a portion of
its original Vitriolic Acid, which happening not to lie near enough to
any particles of Sea-salt, could not exert its power in decomposing
them, and so remains united with its earthy basis; 4. Another part
of the same earth, impregnated with some of the Marine Acid, which
combined therewith upon being expelled from its Alkaline basis by the
Vitriolic Acid, and which the force of fire was unable to separate
from it when the matters were grown perfectly dry. In consequence
of what remains in this _caput mortuum_, if the whole mass be
triturated, moistened with a little water, and distilled a second time,
considerably more Spirit of Salt will be obtained from it: and the same
is to be said of all distillations of this sort.

Spirit of Salt obtained by the means of any other additament than
concentrated Oil of Vitriol is generally very weak: but it may be
dephlegmated and concentrated, if required, much in the same manner as
Oil of Vitriol. For this purpose you must put it into a glass cucurbit,
set it in a _balneum mariæ_, fit thereto a head and a receiver, and
with a moderate degree of heat draw off one third or one half of the
liquor. What comes over into the receiver will be the most aqueous
part, which being the lightest will rise first, impregnated however
with a little acid: in the cucurbit will be left a concentrated Spirit
of Salt, or the most acid part, which being the heaviest will not rise
with the degree of heat that is capable of carrying up the phlegm.
Spirit of Salt thus concentrated, called also _Oil of Salt_, does not
smoke: it is of a yellow colour inclining to green, and an agreeable
smell, not unlike that of saffron.


PROCESS IV.

_To decompose Sea-salt by means of the Nitrous Acid._ Aqua regis.
_Quadrangular Nitre._

Take dried Sea-salt; bruise it to powder; put it into a glass retort,
leaving one half of the vessel empty. Pour upon it a third of its
weight of good Spirit of Nitre. Place your retort in the sand-bath of a
reverberating furnace; put on the dome; lute to the retort a receiver
having a small hole in it, and heat the vessels very slowly. There will
come over into the receiver some vapours, and an acid liquor. Increase
the fire gradually till nothing more rises. Then unlute the vessels,
and pour the liquor out of the receiver into a crystal bottle, stopped
like others containing Acid Spirits.


_OBSERVATIONS._

The Nitrous Acid hath a greater affinity than the Marine Acid with
fixed Alkalis. When therefore Spirit of Nitre and Sea-salt are mixed
together, the same consequences, in some measure, will follow, as when
the Vitriolic Acid is mixed with that salt; that is, the Nitrous Acid
will, like the Vitriolic, decompose it, by dislodging its Acid from
its Alkaline basis, and assuming its place. But as the Nitrous Acid is
considerably weaker, and much lighter, than the Vitriolic Acid, a good
deal of it rises along with the Acid of Sea-salt during the operation.
The liquor found in the receiver is therefore a true _Aqua regis_.

If decrepitated Salt, and a right smoking Spirit of Nitre, be employed
in this process, the _Aqua regis_ obtained will be very strong; and,
during the operation, very elastic vapours will rush out and burst the
vessels, if those precautions be not taken which we pointed out as
necessary in distilling the Spirit of Nitre, and the smoking Spirit of
Salt.

The operation being finished, there is left in the retort a saline
mass, containing Sea-salt not decomposed, and a new species of Nitre,
which having for its basis the Alkali of Sea-salt, that is, as we have
several times observed, an Alkali of a peculiar nature, differs from
the common Nitre, 1. In the figure of its crystals; which are solids of
four sides, formed like lozenges: 2. In that it crystallizes with more
difficulty, retains more water in its crystals, attracts the moisture
of the air, and dissolves in water with the same circumstances as
Sea-salt.



CHAP. IV.

_Of_ BORAX.


PROCESS.

 _To decompose Borax by the means of Acids, and to separate from it the
 Sedative Salt by sublimation and by crystallization._

Reduce to a fine powder the Borax from which you intend to extract
the Sedative Salt. Put this powder into a wide-necked glass retort.
Pour upon it an eighth part of its weight of common water, to moisten
the powder; and then add concentrated Oil of Vitriol to the weight of
somewhat more than a fourth part of the weight of Borax. Set the retort
in a reverberatory, make a moderate fire at first, and augment it
gradually till the retort become red-hot.

A little phlegm will first come over, and then with the last moisture
that the heat expels the Sedative Salt will rise; by which means some
of it will be dissolved in this last phlegm, and pass therewith into
the receiver; but most of it will adhere in the form of saline flowers
to the fore-part of the neck of the retort, just where it is clear of
the groove of the furnace. There they collect into a heap, which the
succeeding flowers push insensibly forward till they slightly stop the
passage. Those which rise after the neck is thus stopped stick to the
after-part of it which is hot, vitrify in some measure, and form a
circle of fused Salt. In this state the flowers of the Sedative Salt
seem to issue out of the circle, as from their basis: they appear
like very thin, light, shining scales, and must be brushed off with a
feather.

At the bottom of the retort will be left a saline mass: dissolve this
in a sufficient quantity of hot water; filter the solution in order
to free it from a brown earth which it deposites; set the liquor to
evaporate, and crystals of Sedative Salt will form in it.


_OBSERVATIONS._

Though Borax is of great use in many chymical operations, especially in
the fusion of metals, as we shall have occasion to see, yet, till of
late years, Chymists were quite ignorant of its nature, as they still
are of its origin; concerning which we know nothing with certainty, but
that it comes rough from the East Indies, and is purified by the Dutch.

M. Homberg was one of the first that attempted to analyse this Salt. He
shewed, that on mixing it with the Vitriolic Acid, and distilling the
mixture, a salt sublimes in little fine needles. This product of Borax
he called by the name of _Sedative Salt_, because he found it had the
property of moderating the great tumult and heat of the blood in fevers.

After M. Homberg, other Chymists also exercised themselves on Borax. M.
Lemery discovered that the Vitriolic is not the only Acid by means of
which the Sedative Salt may be obtained from Borax; but that either of
the other two Mineral Acids, the Nitrous or the Marine, may be used in
its stead.

M. Geoffroy hath greatly facilitated the means of obtaining the
Sedative Salt from Borax; having shewn that it may be extracted by
crystallization as well as by sublimation; and that the Sedative Salt
so obtained is in no respect inferior to that which was procured before
by sublimation only. To him also we are indebted for the discovery,
that in the composition of Borax there is an Alkaline Salt of the same
nature as the basis of Sea-salt. This he found by observing that he got
a Glauber's Salt from a solution of Borax into which he had poured some
Vitriolic Acid with a view to obtain its Sedative Salt.

Lastly, M. Baron, whom we mentioned before on occasion of this Salt,
hath proved, by a great number of experiments, that a Sedative Salt
may be procured from Borax by the help of Vegetable Acids, which was
never done by any body before him; that the Sedative Salt is not
a combination of an Alkaline matter with the Acid made use of in
extracting it, as some of its properties seemed to indicate; but that
it exists previously and completely formed in the Borax; that the Acid
employed to extract it only helps to disengage it from the Alkali with
which it is united; that this Alkali is actually of the same nature as
the basis of Sea-salt, because that after extracting the Sedative Salt,
which by its union therewith forms the Borax, a Neutral Salt is found,
of the same sort with that which would be produced by combining the
basis of Sea-salt with the particular Acid made use of; that is, if
with the Vitriolic Acid, a Glauber's Salt; if with the Nitrous Acid,
a quadrangular Nitre; and if with the Marine Acid, a true Sea-salt;
and, lastly, that the Sedative Salt may be re-united to its Alkali, and
reproduce a Borax.

Nothing therefore now remains, to give us all the insight we can desire
into the nature of Borax, but to know what the Sedative Salt is. M.
Baron hath already given us certain negative notices concerning it,
by shewing what it is not; that is, that the Acid employed in its
extraction doth not enter into its composition. We have great reason to
hope, that he will carry his inquiries still further, and clear up all
our doubts on this subject.

The Sedative Salt may be extracted from Borax, not only by the means
of pure and simple Acids, but also by the same Acids combined with a
metallic basis. Thus Vitriols, for instance, may be employed for this
purpose with good success. It is easy to see, that the Vitriol must
be decomposed on this occasion, and that its Acid cannot unite with
the Alkali in which the Sedative Salt is lodged, without quitting its
metallic basis, which must of course precipitate.

The Sedative Salt actually sublimes, when a liquid containing it is
distilled; but it does not therefore follow, that it is naturally
volatile. It rises only by the aid of the water with which it is mixed.
The proof of this assertion is, that, when all the humidity of the
mixture containing this Salt is dissipated, no more Salt will rise,
be the fire ever so violent; and that by adding more water to moisten
the dried mass containing it, more Salt will every time be obtained,
through many repeated distillations. In the same manner, if some
Sedative Salt be moistened, and exposed to a proper degree of heat, a
small quantity thereof will rise at first by the help of the water; but
as soon as it grows dry it remains exceedingly fixed. This observation
we owe to M. Rouelle.

The Sedative Salt hath the appearance and the taste of a Neutral Salt:
it does not change the colour of the juice of violets; nor does it
easily dissolve in water; for it requires a quart of boiling water to
dissolve two ounces of it: yet, with regard to Alkalis, it has the
properties of an Acid; it unites with those salts, forms therewith a
saline compound which crystallizes, and even expels the Acids that
happen to be combined with them; so that it decomposes the same Neutral
Salts that are decomposed by the Vitriolic Acid.

The Sedative Salt, when suddenly exposed to the violent heat of a
naked fire, loses near half its weight, melts, puts on and retains the
appearance of glass; but its nature still remains unchanged. This glass
dissolves in water, and shoots anew into crystals of Sedative Salt.
This Salt communicates to the Alkaline salt with which it is united,
when in the form of Borax, the property of melting with a moderate
heat, and forming a kind of glass; and it is this great fusibility that
recommends the frequent use of Borax as a flux for assaying ores. It is
also employed sometimes as an ingredient in the composition of glass;
but, in time, it always communicates thereto the fault which its own
glass hath, namely that of tarnishing with the air. The Sedative Salt
hath, moreover, the singular property of dissolving in Spirit of Wine,
and of giving to its flame, when set on fire, a beautiful green colour.
All these observations we owe to Mess. Geoffroy and Baron.

M. Geoffroy prepares the Sedative Salt by crystallization only, in
the following manner. "He dissolves four ounces of refined Borax in a
sufficient quantity of warm water, and then pours into the solution
one ounce and two drams of highly concentrated Oil of Vitriol, which
makes a crackling noise as it falls in. When this mixture has stood
evaporating for some time, the Sedative Salt begins to make its
appearance in little, fine, shining plates floating on the surface of
the liquor. The evaporation is then to be stopped, and the plates will
by little and little increase in thickness and breadth. They unite
together into little tufts, forming with each other sundry different
groups. If the vessel be ever so little stirred, the regularity of
the crystals will be disturbed; so that it must not be touched till
the crystallization appears to be finished. The crystalline clusters,
being grown too bulky and too heavy, will then fall of themselves to
the bottom of the vessel. This being observed, the saline liquor must
be gently decanted from those little crystals, which, as they are not
easily dissolved, must be washed clean, by pouring cold water slowly
on the sides of the pan, three or four times successively, in order
to rinse out all remains of the saline liquor, and then set first to
drain, and afterwards to dry in the sun. This Salt, in the form of
light flakes of snow, is now soft to the touch, cool in the mouth,
slightly bitter, crackling a little between the teeth, and leaving a
small impression of acidity on the tongue. It will keep long without
giving or calcining, if managed according to the preceding directions;
that is, if it be exactly freed from its saline liquor.

"It differs from the Sedative Salt obtained by sublimation in this
respect only, that notwithstanding its seeming lightness it is a
little heavier than the other. M. Geoffroy supposes the cause of this
weight to be, that, as several of the thin plates adhere together in
crystallizing, they retain between them some small matter of humidity;
or, if you will, that, as they form larger crystals, they present
less surface to the air which elevates light bodies: whereas, on the
contrary, the other Sedative Salt, being driven up by the force of
fire, rises into the head of the cucurbit in a more subtile form,
having its particles much more expanded and divided.

"M. Geoffroy, having put his Sedative Salt made by crystallization to
all the same trials with that made by sublimation, satisfied himself
that there is no other difference between the two. If the Sedative Salt
made by crystallizations happens to calcine in the sun; that is, if its
lustre tarnishes, and its surface grows mealy, it is a sign that it
still contains either a little Borax or some Glauber's Salt: for these
two Salts are apt to calcine in this manner, and pure Sedative Salt
should not be subject to this inconvenience. In order to purify it, and
free it entirely from those Salts, it must be dissolved once more in
boiling water. As soon as the water cools, the Sedative Salt reappears
in light, shining, crystalline plates, swimming in the liquor. After
standing four and twenty hours, the liquor must be decanted, and the
salt washed with fresh water; by which means it will be very pure and
beautiful."

Glauber's Salt and Borax dissolve in water with vastly more ease than
the Sedative Salt, and consequently do not crystallize so readily by
much: so that the small portion of those salts which may have been left
on the surface of the Sedative Salt, being diffused through a large
quantity of water, continues in a state of solution, while the Sedative
Salt crystallizes; which being also washed afterwards with fair water,
it is impossible that the smallest particle of those other Salts
should remain adhering to it; and consequently this must be deemed an
excellent way of purifying it.



SECTION II.

_Of Operations on_ METALS.



CHAP. I.

_Of_ GOLD.


PROCESS I.

_To separate Gold, by Amalgamation with Mercury, from the Earth and
Stones with which it is found mixed._

Pulverize the earths and stones containing Gold. Put the powder into a
little wooden tray; dip this tray in water, gently shaking it and its
contents. The water will grow muddy, by taking up the earthy parts of
the ore. Continue washing it in this manner till the water cease to
appear turbid. Upon the ore thus washed pour strong vinegar, having
first dissolved therein, by the help of heat, about a tenth part of its
weight of alum. The powder must be quite drenched and covered with this
liquor, and so left to stand for twice twenty-four hours.

Decant the vinegar, and wash your powder with warm water, till the
last that comes off hath no taste: then dry it, and put it into an
iron mortar, with four times its weight of Quick-silver: triturate the
whole with a heavy wooden pestle, till all the powder be of a blackish
colour: then pour in a little water, and continue rubbing for some time
longer. More earthy and heterogeneous particles will be separated from
the metalline parts by means of this water, which will look dirty: it
must then be decanted, and more fair water added. Repeat this several
times; then dry what remains in the mortar with a sponge, and by the
help of a gentle heat: you will find it an Amalgam of the Mercury with
the Gold.

Put this Amalgam into a chamoy bag: tie a knot on its neck, and squeeze
it hard between your fingers, over some wide-mouthed vessel; there
will issue through the pores of the leather numberless little jets
of Mercury, forming a sort of shower, that will collect into large
globules in the vessel placed underneath. When you can force out no
more Mercury by this means, open the bag, and in it you will find the
Amalgam freed from the superfluous Mercury; the Gold retaining only
about as much thereof as nearly equals itself in weight.

Put this Amalgam into a glass retort; set this retort in the sand-bath
of a reverberating furnace; cover it quite over with sand; apply a
glass receiver half full of water, so that the nose of the retort may
be under the water. The receiver need not be luted to the retort. Give
a gradual heat, and raise the fire till drops of the sublimed Mercury
appear in the neck of the retort, and fall into the water with a
hissing noise. If you hear any noise in the retort slacken your fire a
little. Lastly, when you observe, that, though you raise the fire still
higher than before, nothing more will come over, take out your retort,
break it, and there you will find the Gold, which must be melted in a
crucible with Borax.


_OBSERVATIONS._

Gold is a perfect metal, which can by no means be deprived of its
Phlogiston, and on which few, even of the most powerful chymical
solvents, have any effect: and therefore it almost always hath its
metalline form when found in the earth; from which it may sometimes
be separated by simple lotion. The Gold dust found in the sands of
certain rivers is of this kind. When it resides in stones, or tenacious
earths, it may be extracted by the process here delivered; to wit, by
Amalgamation, or combination of Mercury with Gold. Mercury is incapable
of uniting with any earthy substances, not even with the metallic
earths, when they are deprived of their Phlogiston, and consequently
have not the metalline form.

Hence it follows, that when Mercury is triturated with particles of
Gold, of earth, and of stone, mingled together, it unites with the
Gold, and separates it from those heterogeneous matters. Yet, if there
be along with the Gold any other metal, in its metalline form, except
Iron, the Mercury will amalgamate with that also. This often happens
to Silver, which being a perfect metal as well as Gold, is for that
reason sometimes dug up in its metalline form, and even incorporated
with Gold. When this is the case, the mass that remains in the retort,
after abstracting the Mercury of the Amalgama, is a compound of Gold
and Silver, which are to be separated from each other by the methods
we shall give for that purpose. The present process is therefore
applicable to Silver as well as Gold.

Sometimes Gold is intimately combined with such mineral matters as
hinder the Mercury from acting upon it. In that case the mixed mass
must be roasted before you proceed to Amalgamation: for if the matters
be volatile, such, for instance, as antimony or arsenic, the fire
will carry them off; so that, after roasting, the Amalgamation will
succeed. But sometimes these matters are fixed, and require fusion; if
so, recourse must be had to some particular methods, which we shall
describe when we come to treat of Silver, as these two perfect metals
are to be treated in the same manner.

Ores containing Gold must be washed before an Amalgam is attempted;
that the metalline parts, being freed from the numerous particles of
earth with which they are encompassed, may the more readily incorporate
with the Mercury. Besides, it is the property of Mercury to take the
form of a dark unmetallic powder, after being long rubbed with other
matters, so that it cannot be easily distinguished from the particles
of earth. And hence, if you still continue to grind the matters
together, after the Amalgamation is completed, and wash them again
and again, the water that comes off will always look turbid, being
impregnated with some particles of the Amalgam. This is easily proved:
for if you let the turbid water settle, and distil the sediment, you
will obtain Quick-silver from it.

The ore is to be steeped in vinegar charged with alum, in order to
cleanse the surface of the Gold, which is often covered with a thin
coat of earth that obstructs the Amalgamation.

Great care must be taken that the Mercury employed in this operation be
very pure. If it be adulterated with any metallic substance, it must be
freed therefrom by the methods which we shall propose in their proper
place.

The way of separating Mercury from Gold is founded on the different
properties of these two metallic substances; the one being exceedingly
fixed, and the other very volatile. The union which Mercury contracts
with the metals is not intimate enough, to give the new compound which
results therefrom all the properties of either of the two united
substances; at least so far as concerns their degrees of fixity
and volatility. Hence it comes, that, in our Amalgam, the Gold
communicates but very little of its fixity to the Mercury, and the
Mercury communicates to the Gold but very little of its volatility. Yet
if the Mercury be distilled off with a much greater degree of heat than
is necessary to elevate it, a pretty considerable quantity of Gold will
most certainly be carried up along with it.

It is also of consequence, on another account, that the fire be duly
governed on this occasion. For if too great a degree of heat be
applied, and the fire afterwards lowered, the water in the receiver,
which covers the nose of the retort, will rise into its body, break it
to pieces, and spoil the operation.

The cause of this phenomenon depends on the property which air
possesses of rarefying with heat and condensing with cold, joined to
its weight. As soon as the retort is acted on by a less degree of heat
than acted on it the instant before, the air contained therein is
condensed, and leaves a _vacuum_, which the external air, by virtue of
its weight, tends to occupy; but, the orifice of the retort being under
water, the external air can no way gain admittance, but by pushing in
before it the water which intercepts its passage. This caution, as we
observed above, must be applied to all distillations, where the vessels
are disposed as they are in this.

Care must also be taken that the nose of the retort be not placed too
deep under water: for as the neck grows very warm during the operation,
because the degree of heat required to raise Mercury is about three
times greater than that which raises water, it may easily be broken by
the contact of the cold water in the receiver.

This method of extracting Gold and Silver from their ores, by
Amalgamation with Mercury, is not to be absolutely depended on as a
sure proof of the quantity of those metals that may be contained in
the earth assayed by this means: for some small part of the Amalgam is
always lost in washing it; and, moreover, the Mercury, when squeezed
through chamoy, always carries with it a small portion of Gold. So that
if you desire to know more exactly, by this method, the quantity of
Gold or Silver contained in any earth, the Amalgam must not be squeezed
through chamoy, but distilled altogether. Much the surest method of
making an accurate assay is that by fusion and scorification, which we
shall describe under the head of Silver.

In some countries, and especially in America, the method of
Amalgamation is used for extracting Gold and Silver in large
quantities, from the matrices which contain them in their metalline
form. Agricola and other metallurgists have described the machines by
means whereof such Amalgamations are managed.


PROCESS II.

 _To dissolve Gold in_ Aqua regis, _and by that means to separate it
 from Silver_. Aurum Fulminans. Aurum Fulminans _reduced_.

Take Gold that is perfectly pure, or alloyed with Silver only. Reduce
it to little thin plates, by hammering it on an anvil. If it be not
sufficiently tough, neal it till it be red in a moderate, clear fire,
quite free from smoking coals, and then let it cool gradually, which
will restore its ductility.

When the plates are thin enough, make them red hot once more, and cut
them into small bits with a pair of sheers. Put these bits into a tall,
narrow-mouthed cucurbit, and pour on them twice their weight of good
_Aqua regis_, made of one part Sal Ammoniac, or Spirit of Salt, and
four parts Spirit of Nitre. Set the cucurbit in a sand-bath moderately
heated, stopping its orifice slightly with a paper coffin, to prevent
any dirt from falling in. The _Aqua regis_ will presently begin to
smoke. Round the little bits of Gold will be formed an infinite number
of small bubbles, which will rise to the surface of the liquor. The
Gold will totally dissolve, if it be pure, and the solution will be of
a beautiful yellow colour: if the Gold be alloyed with a small quantity
of Silver, the latter will remain at the bottom of the vessel in the
form of a white powder. If the Gold be alloyed with much Silver, when
the Gold is dissolved the Silver will retain the form of the little
metalline plates put into the vessel.

When the dissolution is completed, gently pour off the liquor into
another low, wide-mouthed, glass cucurbit, taking care that none of the
Silver, which lies at the bottom in the form of a powder, escape with
the liquor. On this powder of Silver pour as much fresh _Aqua regis_ as
will cover it entirely; and repeat this till you are sure that nothing
more can be taken up by it. Lastly, having decanted the _Aqua regis_
from the Silver, wash the Silver with a little Spirit of Salt weakened
with water, and add this Spirit of Salt to the _Aqua regis_ in which
your Gold is dissolved. Then to the body containing these liquors fit
a head and a receiver, and distil with a gentle heat, till the matter
contained in the cucurbit become dry.


_OBSERVATIONS._

It is certain that _aqua regis_ is the true solvent of Gold, and that
it does not touch Silver: so that if the Gold dissolved in it were
alloyed with Silver, which is often the case, the two metals would by
this means be pretty accurately separated from each other. But if you
desire to obtain from this solution a Gold absolutely pure, you must
free it, before you dissolve it, from every other metallic substance
but Silver; because _aqua regis_ acts upon most of the other metals
and the semi-metals. We shall shew under the head of Silver, as we
promised before, how to purify a mass of Gold and Silver from every
other metallic alloy. Thither also we refer the common parting assay
performed by means of _aqua fortis_: because in that operation the
Silver is dissolved, and not the Gold.

If the Gold put to dissolve in _aqua regis_ be pure, the dissolution
is easily and readily effected. But if, on the contrary, it be alloyed
with Silver, the _aqua regis_ finds more difficulty in dissolving it.
Nay, if the Silver exceed the Gold in quantity, the dissolution will
not take place at all, for the reasons adduced in our Theoretical
Elements; of which we shall speak more fully when we come to treat of
the Parting Assay.

In the process we directed the Gold to be dissolved in a tall body.
This precaution is necessary to prevent the loss of some part thereof:
for it is the property of _aqua regis_ to carry off along with it
some of the Gold, especially when there is any Sal Ammoniac in its
composition, if the vessel be heated while the dissolution is going on,
or if the _aqua regis_ be very strong. Yet it is proper to make use of
_aqua regis_ that is too strong rather than too weak: for if it prove
too strong, and be observed not to act upon the metal for that reason,
it is easy to weaken it, by gradually adding small quantities of pure
water, till you perceive it begin to act with vigour. This is a general
rule regarding all metallic dissolutions in Acids.

When the solution of Gold is evaporated to dryness, if you desire to
reduce into a mass the Gold dust left at the bottom of the cucurbit,
you must put it into a crucible, and cover it with pulverized borax,
mixed with a little nitre and calcined wine-lees; then cover the
crucible close, heat it with a moderate fire, which must be afterwards
increased so as to melt the contents. At the bottom of the crucible you
will find a lump of Gold, over which the salts you added will be as it
were vitrified. These salts are added chiefly to promote the fusion of
the metal.

The Gold may, if you will, be separated from its solvent without
evaporating the solution as above directed. You need only mix with the
solution a fixed or volatile Alkali by little and little, till you see
no more precipitate fall, and then let the liquor stand to settle, at
the bottom of which you will find a sediment: filter the whole, and dry
what is left on the filter.

Both fixed and volatile Alkalis possessing, as hath been frequently
repeated, a greater affinity with Acids than metallic substances have,
they precipitate the Gold, and separate it from the Acids in which it
is dissolved: but it is of great consequence to take notice, that,
if you attempt to melt this precipitated Gold in a crucible, it will
fulminate as soon as it feels the heat, with such a terrible explosion,
that, if the quantity be at all considerable, it may prove fatal to
the operator: even rubbing it a little hard will make it blow up. This
preparation is therefore called _Aurum Fulminans_.

Hitherto no satisfactory explanation hath been given of this
phenomenon. Some Chymists considering, that, in the precipitation of
the Gold, a Nitre is regenerated by the union of the Alkali with the
Nitrous Acid which enters into the composition of the _aqua regis_,
imagine that some of this regenerated Nitre, combining with the
precipitated Gold, takes fire and detonates, either by means of some
small portion of Phlogiston that may be contained in the Alkali, or
by means of that which constitutes the Gold itself. But, in the first
place, it is well known that Fixed Alkalis do not contain Phlogiston
enough to make Nitre detonate. Indeed, if a Volatile Alkali be employed
in the precipitation, a Nitrous Ammoniacal Salt will be formed,
containing Phlogiston enough to be capable of detonating without the
concourse of any additional Phlogiston: but this detonation of the
Nitrous Ammoniacal Salt is not to be compared, as to the violence of
its effects, with the fulmination of Gold. Besides, we do not find that
Gold precipitated by a Volatile Alkali explodes with greater force than
that precipitated by a Fixed Alkali. As for the Gold, it is certain
that it suffers no decomposition at all by fulminating. When fulminated
under a glass bell, in such small quantities as not to endanger the
operator, the Gold is found scattered about under the bell in very fine
particles, without having undergone any alteration.

Others have fancied this fulmination of the Gold to be nothing but the
decrepitation of the Sea-salt that is regenerated, in the precipitation
of the metal, by the Fixed Alkali uniting with the Acid of Sea-salt
which makes part of the _aqua regis_. But to this it may be said,
that Gold precipitated by a Volatile Alkali fulminates as violently
as that precipitated by a Fixed Alkali; and yet no sea-salt can be
formed in the liquor by the addition of a Volatile Alkali, but only a
Sal Ammoniac which has not the property of decrepitating. Moreover,
there is no comparison, as to the effects, between the decrepitation of
Sea-salt and the fulmination of Gold.

Nor, lastly, can this fulmination be attributed, as it is by some, to
the effort made by the Salts to escape from amidst the particles of
Gold, in which they are supposed by them to be imprisoned: for then we
might deprive this Gold entirely of its fulminating quality by only
boiling it in water, and so washing off all the saline particles,
which probably adhere to its surface only. It is plain there is great
room for very beautiful discoveries on this subject. In Walerius's
Mineralogy we find some observations that may throw a little light on
the point before us.

"The quantity," says he, "of fulminating Gold precipitated exceeds that
of the Gold dissolved: if the _aqua regis_ be made with Sal Ammoniac
the explosion will be stronger; it will also be more violent if the
solution be precipitated with a Volatile Alkali, than if a Fixed Alkali
be used for that purpose."

One of the speediest and easiest methods to deprive this Gold of its
fulminating quality, is to grind in a mortar twice as much flowers
of Sulphur as you have Gold to reduce, mixing your fulminating Gold
therewith by little and little, as you grind them together; then to
put the mixture into a crucible, and heat it just enough to melt the
Sulphur. Part of the Sulphur will be dissipated in vapours, and the
rest will burn away. When it is quite consumed, increase the fire so
as to make the crucible red-hot. When you perceive no more smell of
Sulphur, pour on the Gold a little Borax, previously melted in another
crucible with a Fixed Alkali, as calcined Wine-lees, or Nitre fixed
with Tartar; and then raise the fire sufficiently to make the whole
flow. After the fusion is completed, you will find a button of Gold at
the bottom of the crucible under the Salts.

Fulminating Gold may also be reduced by pouring on it a sufficient
quantity of Fixed Alkali reduced to a liquor, or of oil of Vitriol,
evaporating all the moisture, and gradually throwing what remains,
mixed up with some pinguinous matter, into a crucible kept red-hot in
a furnace. The reason why these substances deprive the Gold of its
fulminating quality, depends on the causes that produce the fulmination.

Gold may also be separated from _aqua regis_, and precipitated by the
means of several metallic substances that have a greater affinity,
either with _aqua regis_, or with one of the two Acids that compose it.
Mercury is one of the fittest for this purpose. On dropping a solution
of Mercury in the Nitrous Acid by little and little into a solution of
Gold, the mixture becomes turbid, and a precipitate is formed. Continue
dropping in more of the solution of Mercury till no more precipitate
falls; then let the liquor stand to settle, and at the bottom of it
you will find a sediment, which is the precipitated Gold: pour off the
liquor by inclination, and wash the precipitate with fair water.

Mercury hath a greater affinity with the Marine than with the Nitrous
Acid. The affinity which Mercury hath with the Marine Acid is also
greater than that of Gold with the Marine Acid; for unless this Acid
be associated either with the Nitrous Acid, or at least with a certain
proportion of Phlogiston, it will not dissolve Gold. Hence it comes,
that when a solution of Mercury in the Nitrous Acid is dropped into a
solution of Gold in _aqua regis_, the Mercury unites with the Acid of
Sea-salt, which is an ingredient in the _aqua regis_: but the Marine
Acid cannot on this occasion join the Mercury, without deserting the
Gold and the Nitrous Acid with which it was united; and then the Gold,
which cannot be kept in solution by the Nitrous Acid alone, is forced
to quit its solvent and precipitate. The liquor, therefore, that now
floats over the Gold thus precipitated, must contain Mercury united
with the Acid of Sea-salt: and in fact it yields a true Corrosive
Sublimate, which is known to be a combination of Mercury with the
Marine Acid.

Mercury dissolved in Spirit of Nitre is employed to procure the
precipitation we are speaking of; because metallic substances, when so
comminuted by an Acid, are much fitter for such experiments than when
they are in a concrete form.

Gold precipitated in this manner by a metallic substance doth not
fulminate.


PROCESS III.

_To dissolve Gold by Liver of Sulphur._


Mix together equal parts of common Brimstone, and a very strong Fixed
Alkali; for instance, Nitre fixed by Charcoal. Put them in a crucible,
and melt the mixture, stirring it from time to time with a small rod.
There is no occasion to make the fire very brisk; because the Sulphur
facilitates the fusion of the Fixed Alkali. Some sulphureous vapours
will rise from the crucible; the two substances will mix intimately
together, and form a reddish compound. Then throw into the crucible
some little pieces of Gold beat into thin plates, so that the whole do
not exceed in weight one third part of the Liver of Sulphur: raise the
fire a little. As soon as the Liver of Sulphur is perfectly melted, it
will begin to dissolve the Gold with ebullition; and will even emit
some flashes of fire. In the space of a few minutes the Gold will be
entirely dissolved, especially if it was cut and flatted into small
thin leaves.


_OBSERVATIONS._

The process here delivered is taken from M. Stahl. The design of that
ingenious Chymist's inquiry was to discover how Moses could burn the
golden calf, which the Israelites had set up and worshipped while he
was on the mount; how he could afterwards reduce that calf to powder,
throw it into the water which the people used, and make all who had
apostatized drink thereof, as related in the Book of Exodus.

M. Stahl, having first observed that Gold is absolutely unalterable
and indestructible by the force of fire alone, be it ever so violent,
concludes, that without a miracle Moses could not possibly perform the
above-mentioned operations on the golden calf any way but by mixing
with the Gold some matter qualified to alter and dissolve it. He then
takes notice, that pure Sulphur does not act upon Gold at all, and
that many other substances, which are thought capable of dividing and
dissolving it, cannot however do it so completely as is necessary to
render that metal susceptible of the effects related. He then gives the
method of dissolving it by Liver of Sulphur, described in the process.

Liver of Sulphur dissolves likewise all the other metals: but M.
Stahl observes, that it attenuates Gold more than any other metallic
substance, and unites with it much more intimately than with the rest.
This appears from what happens, on attempting to dissolve in water
any of the mixts resulting from the union of another metal with the
Liver of Sulphur: for then the metal separates, and appears in the
form of a powder or fine calx; whereas, when Gold is united with Liver
of Sulphur, the whole compound dissolves in water so perfectly, that
the Gold even passes with the Liver of Sulphur through the pores of
filtering paper.

If an Acid be poured into a solution of this combination of Gold with
Liver of Sulphur, the Acid unites with the Alkali of the _Hepar_, and
the Gold falls to the bottom of the liquor along with the Sulphur,
which doth not quit it. The Sulphur thus precipitated with the Gold
is easily carried off by a slight torrefaction, after which the
Gold remains exceedingly comminuted. The Sulphur of this compound
may also be destroyed by torrefaction, without the trouble of a
previous solution and precipitation, and then also the Gold remains so
attenuated as to be miscible with liquors, and floats on them, or swims
in them, in such a manner that it may easily be swallowed with them in
drinking. From all this M. Stahl concludes there is great reason to
believe it was by means of the Liver of Sulphur that Moses divided, and
in a manner calcined, the golden calf, so that he could mingle it with
water, and make the Israelites drink it.


PROCESS IV.

_To separate Gold from all other metallic Substances by means of
Antimony._

Having put the Gold you intend to purify into a crucible, set it in
a melting furnace, cover it, and make the Gold flow. When the metal
is in fusion cast upon it, by a little at a time, twice its weight
of pure crude Antimony in powder, and after each projection cover
the crucible again immediately: this done keep the matter in fusion
for a few minutes. When you perceive that the metallic mixture is
perfectly melted, and that its surface begins to sparkle, pour it out
into a hollow iron cone, previously heated, and smeared on the inside
with tallow. Immediately strike with a hammer the floor on which the
cone stands; and when all is cold, or at least sufficiently fixed,
invert the cone and strike it: the whole metallic mass will fall out,
and the under part thereof, which was at the point of the cone, will
be a Regulus more or less yellow as the Gold was more or less pure.
On striking the metallic mass the Regulus will freely part from the
sulphureous crust at top.

Return this Regulus into the crucible, and melt it. Less fire will do
now than was required before. Add the same quantity of Antimony, and
proceed as at first. Repeat the same operation a third time, if your
Gold be very impure.

Then put your Regulus into a good crucible, much larger than is
necessary to hold it. Set your crucible in a melting furnace, and heat
the matter but just enough to make it flow, with a smooth, brilliant
surface. When you find it thus conditioned, point towards it the nose
of a long-snouted pair of bellows, and therewith keep gently and
constantly blowing. There will arise from the crucible a considerable
smoke, which will abate greatly when you cease to blow, and increase
as soon as you begin again. You must raise the fire gradually as you
approach towards the end of the operation. If the surface of the metal
lose its brilliant polish, and seem covered with a hard crust, it is
a sign the fire is too weak; in which case it must be increased, till
the surface recover its shining appearance. At last, when no more smoke
rises, and the surface of the Gold looks neat and greenish, cast on
it, by little and little, some pulverized Nitre, or a mixture of Nitre
and Borax. The matter will swell up. Continue thus adding more Nitre
gradually, till no commotion is thereby produced in the crucible; and
then let the whole cool. If you find, when the Gold is cold, that it is
not tough enough, melt it over again; when it begins to melt, cast in
the same Salts as before; and repeat this till it be perfectly ductile.


_OBSERVATIONS._

Antimony is a compound, consisting of a semi-metallic part united with
about a fourth part of its weight of common Sulphur. It appears, in the
ninth column of the Table of Affinities, that all the metals, Mercury
and Gold excepted, have a greater affinity than the reguline part of
Antimony with Sulphur. If therefore Gold, adulterated with a mixture
of Copper, Silver, or any other metal, be melted with Antimony, those
metals will unite with the Sulphur of the Antimony, and separate it
from the reguline part, which being thus set free will combine and be
blended with the Gold. These two metallic substances, forming a mass
far heavier than the other metals mixed with the sulphur, fall together
to the bottom of the crucible in the form of a Regulus, while the
others float over them like a sort of scoria or flag: and thus the Gold
is freed from all alloy but the reguline part of the Antimony.

As all the other metals have a great affinity with Sulphur, and Gold
is the only one that is capable of resisting its action, one would
think Sulphur alone might be sufficient to free it from the metals
combined with it, and that it would therefore be better to employ pure
Sulphur, in this operation, than to make use of Antimony; the reguline
part of which remaining united with the Gold requires another long and
laborious operation to get rid of it.

Indeed, strictly speaking, Sulphur alone would be sufficient to
produce the desired separation: but it is proper to observe, that, as
Sulphur alone is very combustible, most of it would be consumed in
the operation before it could have an opportunity to unite with the
metallic substances; whereas, when it is combined with the Regulus
of Antimony, it is thereby enabled to bear the action of the fire
much longer without burning, and consequently is much fitter for the
purpose in question. Besides, if we were to make use of pure Sulphur,
a great part of the Gold, which is kept in perfect fusion, and its
precipitation facilitated, by the Regulus of Antimony, would remain
confounded with the Sulphureous scoria.

Nevertheless, seeing the metals with which Gold is alloyed cannot
be separated from it by Antimony, but that a quantity of Regulus
proportioned to the quantity of the metals so separated will unite
with the Gold, and that the more Regulus combines with the Gold, the
more tedious, chargeable, and laborious will the operation prove, this
consideration ought to have some influence in directing our process.
Therefore, if the Gold be very impure, and worse than sixteen carats,
we must not mix it with crude Antimony alone, but add two drams of
pure Sulphur for every carat the Gold wants of sixteen, and lessen the
quantity of Antimony in proportion to that of the real Gold.

It is necessary to keep the crucible close covered, after mixing the
Antimony with the Gold, to prevent any coals from falling into it: for,
if that should happen, the melted mass would puff up considerably, and
might perhaps run over.

The inside of the cone, into which you pour the melted metallic mass,
must be greased with tallow, to prevent its sticking thereto, and that
it may come easily out. Striking the floor, on which the cone with the
melted metal stands, helps the precipitation and descent of the Regulus
of Gold and Antimony to the bottom of the cone.

Less fire is requisite to melt this compound Regulus, in order to add
fresh Antimony, than was necessary before the Gold was mixed with the
reguline part of the Antimony; because this metallic substance, being
much more fusible than Gold, promotes its melting. The Antimony is
mixed with the Gold by repeated projections, that the separation of
the metals may be accomplished with the greater ease and accuracy. Yet
the operation might be successfully performed, by putting in all the
Antimony at once, and with one melting only.

The metalline mass found at the bottom of the cone after all these
operations, is a mixture of Gold with the reguline part of the
Antimony. All the rest of the process consists only in separating this
reguline part from the Gold. As Gold is the most fixed of all metals,
and as the Regulus of Antimony cannot bear the violence of fire without
flying off in vapours, nothing more is necessary for this purpose but
to expose the compound, as directed in the process, to a heat strong
enough and long enough continued, to dissipate all the Regulus of
Antimony. This semi-metal exhales in the form of a very thick white
smoke. It is proper to blow gently into the crucible during the whole
operation; because the immediate contact of the fresh air incessantly
thrown in promotes and considerably increases the evaporation: and this
is a general rule applicable to all evaporations.

The fire must be gradually raised as the Regulus of Antimony is
dissipated, and the operation draws towards an end; because the mixed
mass of Regulus of Antimony and Gold becomes so much the less fusible
as the proportion of the Regulus is lessened. Though the Regulus of
Antimony be separated from the Gold in this operation, because the
latter is of such a fixed nature that it cannot be volatilized by the
degree of fire which dissipates the Regulus; yet, as the Regulus is
very volatile, it will undoubtedly carry up some of the Gold along with
it, especially if you hurry on the evaporation too fast, by applying
too great a degree of fire, by blowing too briskly into the crucible,
and still more if you evaporate your mixture in a broad flat vessel
instead of a crucible. All these things must therefore be avoided, if
you would lose no more Gold than you needs must.

However, unless the evaporation be carried to the utmost, by the means
above pointed out, a small portion of the Regulus of Antimony will
always remain combined with the Gold, which defends it from the action
of the fire. This small portion of Regulus hinders the Gold from being
perfectly pure and ductile. In order therefore to consume and scorify
it, we cast Nitre into the crucible when we perceive it to emit no more
white vapours.

We know that Nitre has the property of reducing all metallic substances
to a calx, Gold and Silver excepted; because it deflagrates with
the phlogiston to which their metalline form is owing: but as this
accension of the Nitre occasions a tumid effervescence, care must be
taken to throw it in but by little and little at a time; for if too
much be projected at once the melted matter will run over.

This operation might be considerably abridged by taking advantage of
the property which Nitre possesses of thus consuming the phlogiston
of metallic substances; as by means thereof we might destroy all the
Regulus of Antimony incorporated with the Gold, without having recourse
to a long and tedious evaporation. But then we should at the same time
lose a much greater quantity of Gold, by reason of the tumult and
ebullition which are inseparable from the detonation of Nitre. On the
whole, therefore, if Nitre be made use of to purify Gold, great care
must be taken to apply but very little of it at a time.

All the Silver that was mixed with the Gold, and indeed a little of
the Gold itself, remains confounded with the sulphureous scoria, which
floats upon the Golden Regulus after the addition of the Antimony: we
shall shew in the Chapter on Silver how these two metals are to be
separated from the Sulphur.



CHAP. II.

_Of_ SILVER.


PROCESS I.

_To separate Silver from its Ore, by means of Scorification with Lead._

Beat to powder in an iron mortar the ore from which you mean to
separate the Silver, having first roasted it well in order to free it
from all the Sulphur and Arsenic that it may contain. Weigh it exactly:
then weigh out by itself eight times as much granulated Lead. Put one
half of this Lead into a test, and spread it equally thereon: upon this
Lead lay your ore, and cover it quite over with the remaining half of
the Lead.

Place the test thus loaded under the further end of the muffle in a
cupelling furnace. Light your fire, and increase it by degrees. If you
look through one of the apertures in the door of the furnace you will
perceive the ore, covered with calcined Lead, swim upon the melted
Lead. Presently afterwards it will grow soft, melt, and be thrown
towards the sides of the vessel, the surface of the Lead appearing in
the midst thereof bright and shining like a luminous disc: the Lead
will then begin to boil, and emit fumes. As soon as this happens, the
fire must be a little checked, so that the ebullition of the Lead may
almost entirely cease, for about a quarter of an hour. After this it
must be excited to the degree it was at before, so that the Lead may
begin again to boil and smoke. Its shining surface will gradually
lessen, and be covered with _scoriæ_. Stir the whole with an iron hook,
and draw in towards the middle what you observe towards the sides of
the vessel; to the end that, if any part of the ore should still remain
undissolved by the Lead, it may be mixed therewith.

When you perceive that the matter is in perfect fusion, that the
greatest part of what sticks to the iron hook, when you dip it in the
melted matter, separates from it again, and drops back into the vessel;
and that the extremity of this instrument, when grown cold, appears
varnished over with a thin, smooth, shining crust; you may look on
these as marks that the business is done, and the more uniform and
evenly the colour of the crust is, the more perfect may you judge the
scorification to be.

Matters being brought to this pass, take the test with a pair of tongs
from under the muffle, and pour its whole contents into an iron cone,
first heated and greased with tallow. This whole operation lasts about
three quarters of an hour. When all is cold, the blow of a hammer
will part the Regulus from the scoria; and as it is not possible, how
perfect soever the scorification be, to avoid leaving a little Lead
containing Silver in the scoria, it is proper to pulverize this scoria,
and separate therefrom whatever extends under the hammer, in order to
add it to the Regulus.


_OBSERVATIONS._

Silver, as well as Gold, is often found quite pure, and under its
metalline form, in the bowels of the earth; and in that case it may
be separated from the stones or sand in which it is lodged by simple
washing, or by Amalgamation with Mercury, in the same manner as before
directed for Gold. But it also happens frequently, that Silver is
combined in the ore with other metallic substances and minerals, which
will not admit of this process, but force us to employ other methods of
separating it from them.

Sulphur and Arsenic are the substances to which Silver and the other
metals usually owe their mineral state. These two matters are never
very closely united with Silver; but may be pretty easily separated
from it by the action of fire, and the addition of Lead. If Arsenic be
predominant in a Silver ore, it will unite with the Lead by the help
of a pretty moderate heat, and quickly convert a considerable quantity
thereof into a penetrating fusible glass, which has the property of
scorifying with ease all substances that are capable of scorification.

When Sulphur predominates, the scorification proceeds more slowly,
and doth not always succeed; because that mineral combined with Lead
lessens its fusibility, and retards its vitrification. In this case,
part of the Sulphur must be dissipated by roasting: the other part
unites with the Lead; and that, being rendered lighter by this union,
floats on the rest of the mixture, which chiefly contains the Silver.
At last, the joint action of the air and of the fire dissipates the
portion of Sulphur that had united with the Lead: the Lead vitrifies
and reduces to a scoria whatever is not either Silver or Gold: and
thus the Silver being disentangled from the heterogeneous matters with
which it was united, one part thereof being dissipated and the other
vitrified, combines with the portion of Lead which is not vitrified,
and falls through the scoria, which, to favour its descent, must be in
perfect fusion.

The whole process, therefore, consists of three distinct operations.
The first is Roasting, which dissipates some of the volatile substances
found united with the Silver: the second is Scorification, or the
Vitrification of the fixed matters also united with the Silver, such
as sand, stones, metals, _&c._ and the third is precipitation, or the
separation of the Silver from the scoria. The two first are, as hath
been shewn, preparatives for the last, and indeed produce it.

As every thing we said concerning Gold, when we treated of the process
of Amalgamation, is to be applied to Silver, which may be extracted
by the same method when it is in its metalline form; in the same
manner, all we now advance touching the method of extracting Silver
by Scorification, when it is depraved with a mixture of heterogenous
matters, is equally applicable to Gold in the same circumstances: and
indeed Silver almost always contains more or less Gold naturally.

In the process we directed, that the ore should be pulverized before
it be exposed to the fire, with a view to enlarge its surface, and by
that means facilitate the action of the Lead upon it, as well as the
evaporation of its volatile parts.

We recommended the precaution of slackening the fire a little at the
beginning of the operation, only to prevent the Lead from being too
hastily converted into litharge, lest it should penetrate and corrode
the test before it had wholly dissolved the ore: but if we were
perfectly certain of the vessel's being so good as to be in no danger
of penetration by the Lead, this precaution would be needless.

It is proper to add eight parts of Lead for one of ore; though so
much is not always absolutely necessary, especially when the ore is
very fusible. The success of this operation depends chiefly on the
completeness of the Scorification; and therefore the addition of more
Lead than enough is attended with no inconvenience: for, as it always
promotes the Scorification, it can never do any harm.

If the ore be mixed with such earthy and stony parts as cannot be
separated from it by washing, it is the more difficult of fusion,
even though the stones should be such as are most disposed to vitrify;
because the most fusible earths and stones are always less so than most
metallic substances. In that case it will be necessary, for effecting
the Scorification, to mix thoroughly with the pulverized ore an equal
quantity of Glass of Lead, to add twelve times as much granulated Lead,
and then to proceed as directed for a fusible ore; exposing the mixture
to a degree of fire strong enough, and long enough kept up, to give
the scoria all the properties above required as signs of a perfect
scorification.

Silver ore is sometimes mixed with Pyrites, and the ore of Arsenic, or
Cobalt, which also make it refractory. As the Pyrites contain a large
quantity of Sulphur, which is very volatile as well as Arsenic; in
this case it is proper to begin with freeing the ore from these two
extraneous substances. This is easily done by roasting: only be sure,
when you first expose the ore to the heat, to cover the vessel in which
you roast it, for some minutes, with an inverted vessel of the same
width; because such sorts of ore are very apt to fly when they first
feel the heat.

After this uncover it, and leave it exposed to the fire till no more
sulphureous or arsenical matters rise. Then mix it with the same
quantity of Glass of Lead as we ordered for ores rendered refractory by
the admixture of earths or stones, and proceed in the same manner.

It is the more necessary to roast Silver ore infected with Sulphur and
Arsenic, because, as Sulphur obstructs the fusion of Lead, it cannot
but do hurt, and protract the operation; and Arsenic does mischief, on
the other hand, by scorifying a very great quantity of Lead too hastily.

When the Sulphur and Arsenic are dissipated by roasting, the ore must
be treated like that which is rendered refractory by stony and earthy
matters; for as the pyrites contain much iron, there remains, after the
Sulphur is evaporated, a considerable quantity of martial earth, which
is difficult to scorify. The pyrites, as well as the cobalts, contain
moreover an unmetallic earth, which is hard to fuse.

The general rule therefore is, when the ore is rendered refractory
by any cause whatever, to mix it with Glass of Lead, and to add a
larger quantity of granulated Lead. Yet some ores are so refractory
that Lead alone will not do the business, and recourse must be had to
some other flux. That which is fittest for the present purpose is the
_Black Flux_, composed of one part of Nitre and two parts of Tartar
deflagrated together. The Phlogiston contained in this quantity of
Tartar is more than sufficient to alkalizate the Nitre. This Flux,
therefore, is nothing more than Nitre alkalizated by Tartar, mixed with
some of the same Tartar that hath not lost its Phlogiston, and is only
reduced to a sort of coal.

The _White Flux_ is also very fit to promote fusion; but on this
occasion the Black Flux is preferable, because the Phlogiston of the
Black Flux prevents the Lead from being too soon converted to litharge,
and so gives it time to dissolve the metallic matters. The White Flux,
which is the result of equal parts of Tartar and Nitre alkalizated
together, being no more than an Alkali destitute of Phlogiston, or
containing but very little, doth not possess this advantage.

If Silver should be combined in the ore with Iron in its metalline
state, which however does not commonly happen, then, in order to
separate them, the Iron must be deprived of its Phlogiston, and
converted to a _crocus_ before the mixed mass be melted with Lead;
which may be done by dissolving it in the Vitriolic Acid, and then
evaporating the Acid.

We are necessitated to make use of this contrivance, because Iron in
its metalline form cannot be dissolved either by Lead or by the Glass
of Lead; but when it is reduced to a calx, litharge unites with it and
scorifies it.

If you have not at hand the utensils necessary for performing the
operation we have been describing in a test, and under the muffle; or
if you have a mind to work on a greater quantity of ore at a time, you
may make use of a crucible for the purpose, and perform the operation
in a melting furnace.

In this case the ore must be prepared, as above directed, according to
its nature, and mixed with a proper quantity of Lead and Glass of Lead;
the whole put into a good crucible, leaving two thirds thereof empty,
and covered with a mixture of Sea-salt and a little Borax, both very
dry, to the thickness of a full half inch.

This being done, set the crucible in the midst of a melting furnace,
raise the coals quite to the lip of the crucible; light the fire;
cover the furnace with its dome; but do not urge the fire more than
is necessary to bring the mixture to perfect fusion: leave it thus in
fusion for a good quarter of an hour; stir the whole with a bit of
strong iron wire; then let it cool; break the crucible, and separate
the Regulus from the scoria.

The Salts added on this occasion are fluxes, and their use is to
procure a perfect fusion of the scoria.

If the melted matters be left exposed to the fire, either in a test
or in a crucible, longer than is above prescribed, the portion of
Lead, that hath united and precipitated with the Silver, will at last
vitrify, and at the same time scorify all the alloy with which that
metal may be mixed. But as there are no vessels that can long endure
the action of litharge, without being pierced like a sieve, some of the
Silver may escape through the holes or fissures of the vessel, and so
be lost. It is better, therefore, to complete the purification of your
Silver by the operation of the Cupel, the description of which follows.


PROCESS II.

_The refining of Silver by the Cupel._

Take a cupel capable of containing one third more matter than you
have to put into it: set it under the muffle of a furnace, like that
described in our Theoretical Elements, as peculiarly appropriated to
this sort of operation. Fill the furnace with charcoal; light it; make
the cupel red-hot, and keep it so till all its moisture be evaporated;
that is, for about a good quarter of an hour, if the cupel be made
wholly of the ashes of burnt bones; and for a whole hour, if there be
any washed wood-ash in its composition.

Reduce the Regulus which remained after the preceding operation to
little thin plates, flatting them with a small hammer, and separating
them carefully from all the adherent scoria. Wrap these in a bit of
paper, and with a small pair of tongs put them gently into the cupel.
When the paper is consumed the Regulus will soon melt, and the scoria,
which will be gradually produced by the Lead as it turns to litharge,
will be driven to the sides of the cupel, and immediately absorbed
thereby. At the same time the cupel will assume a yellow, brown, or
blackish colour, according to the quantity and nature of the scoria
imbibed by it.

When you see the matter in the cupel in a violent ebullition, and
emitting much smoke, lower the fire by the methods formerly prescribed.
Keep up such a degree of heat only that the smoke which ascends
from the matter may not rise very high, and that you may be able to
distinguish the colour which the cupel acquires from the scoria.

Increase the fire by degrees, as more and more litharge is formed and
absorbed. If the Regulus examined by this assay contain no Silver,
you will see it turn wholly into scoria, and at last disappear. When
it contains Silver, and the quantity of Lead is much diminished, you
will perceive little vivid irises, or beautiful rain-bow colours,
shooting swiftly along its surface, and crossing each other in many
different directions. At last, when all the Lead is destroyed, the
thin dark skin, that is continually protruded by the Lead while it is
turning into litharge, and which hitherto covered the Silver, suddenly
disappears; and, if at this moment the fire happen not to be strong
enough to keep the Silver in fusion, the surface of that metal will at
once dart out a dazzling splendour: but, if the fire be strong enough
to keep the Silver in fusion, though freed from all mixture of Lead,
this change of colour, which is called its _fulguration_, will not be
so perceptible, and the Silver will appear like a bead of fire.

These phenomena shew that the operation is finished. But the cupel
must still be left a minute or two under the muffle, and then drawn
slowly out with the iron hook towards the door of the furnace. When the
Silver is so cooled as to be but moderately red, you may take the cupel
from under the muffle with your little tongs, and in the middle of its
cavity you will find an exceeding white bead of Silver, the lower part
whereof will be unequal, and full of little pits.


_OBSERVATIONS._

The Regulus obtained by the former process consists altogether of
the Silver contained in the ore, alloyed with the other metals that
happened to be mixed therewith in its mineral state, and a good deal of
the Lead that was added to precipitate the Silver. The operation of the
cupel may be considered as the sequel of that process, being intended
only to reduce into a scoria whatever is not Gold or Silver. Lead being
of all metals that which vitrifies the most easily, which most promotes
the vitrification of the rest, and the only one which, when vitrified,
penetrates the cupel, and carries along with it the other metals which
it hath vitrified, is consequently the fittest for that purpose. We
shall see in its place, that Bismuth hath the same properties with
Lead, and may be substituted for it in this operation.

Care must be taken to chuse a cupel of a proper capacity. Indeed it
should rather be too big than too little: because the operation is
no way prejudiced by an excess in its size; whereas, if it be too
small, it will be over-dosed with Lead, and at last the litharge, which
destroys every thing, will corrode its cavity, and eat holes through
the very body of the vessel. Add, that the ashes, of which the cupel
is made, being once glutted with litharge, absorb it afterwards but
slowly, and that the quantity of this vitrified litharge, becoming too
great to be contained in the substance of the vessel, exsudes through
it, and drops on the floor of the muffle, which it corrodes and renders
unequal; and moreover solders to it the vessels set thereon. It may be
laid down as a general rule for determining the size of a cupel, that
it weigh, at least, half as much as the metallic mass to be refined in
it.

It is also of the utmost consequence that the cupel be well dried
before the metal be put into it. In order to make sure of this point,
it must be kept red-hot for a certain time, as is above directed:
for though to the sight and to the touch it may appear very dry, it
nevertheless obstinately retains a small matter of moisture, sufficient
to occasion the loss of some of the metal; which, when it comes to
melt, will be thereby spirited up, in the form of little globules, to
the very roof of the muffle. The cupels that stand most in need of
an intense heat to dry them, are those chiefly in whose composition
wood-ashes are employed: for whatever care be taken to lixiviate those
ashes before they are used, they will still retain a little alkaline
salt; and that, we know, is very greedy of moisture, will not part
entirely with it, but by the means of a violent calcination, and
presently re-imbibes it when exposed to the air.

A little Phlogiston also may still be left in the ashes of which the
cupels are made; and that is another reason for calcining them before
they are used. By this means the remaining Phlogiston is dissipated,
which might otherwise combine with the litharge during the operation,
reduce it, and occasion such a ferment in the matter as to make some of
it run over; to these inconveniencies, which any remainder of moisture
or Phlogiston may produce, we must add the cracks and flaws, which are
very incident to cupels not perfectly freed from both those matters.

It is of no less importance to the success of this operation, that a
due degree of heat be kept up. In the process we have described the
marks which shew the heat to be neither too strong nor too weak; when
it exceeds in either of these respects it may be known by the following
signs.

If the fume emitted by the Lead rise like a spout to the roof of
the muffle; if the surface of the melted metal be extremely convex,
considering the quantity of the mass: if the cupel appear of such a
white heat, that the colour communicated thereto by the imbibed scoria
cannot be distinguished: all these shew that the heat is too great, and
that it ought to be diminished. If, on the contrary, the vapours only
hover, as it were, over the surface of the metal; if the melted mass
be very flat, considering its quantity; if its ebullition appear but
faint; if the _scoriæ_, that appear like little fiery drops of rain,
have but a languid motion; if the scoria gather in heaps, and do not
penetrate the cupel; if the metal be covered with it as with a glassy
coat; and, lastly, if the cupel look dull; these are proofs that the
heat is too weak, and ought to be increased.

The design of this operation being to convert the Lead into litharge,
and to give it sufficient time and opportunity to scorify and carry
off with it whatever is not Gold or Silver; the fire must be kept up
to such a degree that the Lead may easily be turned into litharge, and
yet that litharge not be absorbed too hastily by the cupel, but that
a small quantity thereof may all along remain, like a ring, round the
melted metal.

The fire is to be gradually increased as the operation draws nearer
to its end: for, as the proportion of the Lead to the Silver is
continually lessening, the metallic mass gradually becomes less
fusible; while the Silver defends the Lead mixed with it from the
action of the fire, and prevents its being easily converted into
litharge.

When the operation is finished, the cupel must still be left under
the muffle, till it has imbibed all the litharge, to the end that the
bead of Silver may be easily taken out: for, without this precaution,
it would stick so fast as not to be removed, but by breaking off part
of the cupel along with it. Care must also be taken to let this bead
of Silver cool gradually, and be perfectly fixed, before you draw it
from under the muffle; for if you expose it at once to the cold air,
before it be fixed, it will swell, shoot into sprigs, and even dart out
several little grains to a considerable distance, which will be lost.

If the bead appear to have a yellowish tinge, it is a sign that it
contains a great deal of Gold, which must be separated from it by the
methods to be hereafter shewn.

It is proper to observe, that there is scarce any Lead that does not
contain some Silver; too little perhaps to defray the charges necessary
to separate it, yet considerable enough to lead us into an error, by
mixing with the Silver obtained from an ore, and increasing its weight.
And therefore, when the operations above described are applied to the
assaying of an ore, in order to know how much Silver it yields, it is
previously necessary to examine the Lead to be used, and to ascertain
the quantity of Silver it contains, which must be deducted from the
total weight of the bead of Silver obtained by purifying it in this
manner.

Silver may be separated from its ore, and at the same time refined, by
the single operation of the cupel, without any previous scorification
with Lead. In order to do this, you must pound the ore; roast it, to
dissipate all its volatile parts; mix it with an equal quantity of
litharge, if it be refractory; divide it into five or six parcels,
wrapping each in a bit of paper; weigh out eight parts of granulated
Lead for one of ore, if it be fusible, and from twelve to sixteen,
if it be refractory; put one half of the Lead into a very large
cupel under the muffle; add thereto one of the little parcels of
ore, when the Lead begins to smoke and boil; immediately slacken the
fire a little; continue the same degree of heat till you perceive
that the litharge formed round the metal, and on its surface, begins
to look bright; then raise the fire; add a fresh parcel of ore;
continue proceeding in the same manner till you have put in all the
ore; then add the remaining half of the granulated Lead, and conduct
the succeeding part of the operation in the same manner as that of
cupelling.

In this operation it is necessary that the fire be not too strongly
urged, and that it be diminished every time you add a fresh
parcel of ore; that so the Lead and the litharge may have time
to dissolve, scorify, and carry off into the pores of the cupel,
all the adventitious matters with which your Silver may be mixed.
Notwithstanding this precaution, when the ore is refractory, there
often gathers in the cupel a great quantity of scoria, together also
with some of the ore that could not be dissolved and scorified. It is
with a view to remedy this inconvenience that the second moiety of the
Lead is added towards the end, which completes the dissolution and
scorification of the whole; so that by means thereof no scoria, or very
little, is left in the cupel at the end of the operation.

The operation of the cupel is chiefly used to purify Silver from the
alloy of Copper; because this metal, being more fixed and harder to
calcine than other metallic substances, is the only one that remains
united with Silver and Lead, after roasting and scorification with
Lead. It requires no less than sixteen parts of the Lead to destroy
it in the cupel, and separate it from Silver. It melts into one mass
with the Lead; and the glass produced by these two metals, deprived
of their phlogiston, inclines to a brown or a black colour; by which
appearance chiefly we know that our Silver was alloyed with Copper.


PROCESS III.

_To purify Silver by Nitre._

Granulate the Silver you intend to purify, or reduce it to thin plates;
put it into a good crucible; add thereto a fourth part in weight of
very dry pulverized Nitre, mixed with half the weight of the Nitre of
calcined Wine-lees, and about a sixth part of the same weight of common
glass in powder. Cover this crucible with another crucible inverted;
which must be of such a size that its mouth may enter a little way into
that of the lower one, and have its bottom pierced with a hole of about
two lines in diameter. Lute the two crucibles together with clay and
Windsor-loam. When the lute is dry, place the crucibles in a melting
furnace. Fill the furnace with charcoal, taking care however that the
fuel do not rise above the upper crucible.

Kindle the fire, and make your vessels of a middling-red heat. When
they are so, take up with the tongs a live-coal, and hold it over
the hole of the upper crucible. If you immediately perceive a vivid
splendour round the coal, and at the same time hear a gentle hissing
noise, it is a sign that the fire is of a proper strength; and it must
be kept up at the same degree till this phenomenon cease.

Then increase the fire to the degree requisite to keep pure Silver in
fusion; and immediately after take your vessels out of the furnace.
You will find the Silver at the bottom of the lower crucible, covered
with a mass of Alkaline scoria of a greenish colour. If the metal be
not rendered perfectly pure and ductile by this operation, it must be
repeated a second time.


_OBSERVATIONS._

The purification of Silver by Nitre, as well as the process for
refining it on the cupel, is founded on the property which this metal
possesses of resisting the force of the strongest fire, and the
power of the most active solvents, without losing its phlogiston.
The difference between these two operations consists wholly in the
substances made use of to procure the scorification of the imperfect
metals, or semi-metals, that may be combined with the Silver. In the
former this was obtained by Lead, and here it is effected by Nitre.
This Salt, as we have shewn, hath the property of calcining and quickly
destroying all metallic substances, by consuming their phlogiston,
except the perfect metals, Gold and Silver, which alone are able to
resist its force. This method may therefore be employed to purify Gold
as well as Silver, or indeed both the two mixed together.

In this operation the Nitre is gradually alkalizated, as its Acid is
consumed with the phlogiston of the metallic substances. The Alkaline
Salt and pounded glass are added, with a view to promote the fusion of
the metalline calces, as fast as they are formed, and to fix and retain
the Nitre, which, as we shall presently see, is apt to fly off in a
certain degree of heat.

The precaution of covering the crucible with another crucible inverted,
which hath only a small hole in its bottom, is designed to prevent any
of the Silver from being lost in the operation: for when the Nitre
comes to be acted on by a certain degree of heat, and especially when
it deflagrates with any inflammable matter, part of it flies off, and
so rapidly too as to be capable of carrying off with it a good deal of
the Silver. The little hole left in the covering crucible is necessary
for giving vent to the vapours, which rise during the deflagration
of the Nitre, as they would otherwise open themselves a passage by
bursting the vessels. After the operation this vent-hole is found beset
with many little particles of Silver, which would have been lost if the
crucible had not been covered.

If you should observe, during the detonation of the Nitre, that a great
many vapours issue through the vent-hole with a considerable hissing
noise, even without applying the coal, you must take it for a sign that
the fire is too brisk, and accordingly check it; else a great deal of
the Nitre will be dissipated, and with it much Silver.

You must observe to take the Silver out of the fire as soon as it is in
fusion: for if you neglect this, the Nitre being entirely dissipated
or alkalizated, the calces of the metals destroyed by it may possibly
recover a little phlogiston, communicated either by the vapours of
the charcoal, or by little bits of coal accidentally falling into the
crucible; by which means some portion of those metals being reduced
will mix again with the Silver, prevent its having the desired degree
of purity and ductility, and oblige you to begin the operation afresh.


PROCESS IV.

 _To dissolve Silver in_ Aqua Fortis, _and thereby separate it from
 every other metalline substance. The Purification of_ Aqua Fortis.
 _Silver precipitated by Copper._

The Silver you intend to dissolve being beaten into thin plates, put it
into a glass cucurbit; pour on it twice its weight of good precipitated
_aqua fortis_; cover the cucurbit with a piece of paper, and set it on
a sand-bath moderately heated. The _aqua fortis_ will begin to dissolve
the Silver as soon as it comes to be a little warm. Red vapours will
rise; and from the upper surfaces of the Silver there will seem to
issue streams of little bubbles, ascending to the top of the liquor,
between which and the Silver they will form, as it were, a number of
fine chains: this is a sign that the dissolution proceeds duly, and
that the degree of heat is such as it ought to be. If the liquor appear
to boil and be agitated, a great many red vapours rising at the same
time, it is a sign that the heat is too great, and should be lessened
till it be reduced to the proper degree indicated above: having
obtained that, keep it equally up till no more bubbles or red vapours
appear.

If your Silver be alloyed with Gold, the Gold will be found, when the
dissolution is finished, at the bottom of the vessel in the form of a
powder. This solution must now be decanted while it is yet warm; on
the powder pour half as much fresh _aqua fortis_ as before, and make
it boil; again decant this second _aqua fortis_, and repeat the same
a third time; then with fair water wash the remaining powder well: it
will be of a brown colour inclining to red. In the observations we
shall show how the Silver is to be separated from the _aqua fortis_.


_OBSERVATIONS._

All the processes on Silver already delivered, whether for extracting
it from its ores, or for refining it, either by the Cupel or by Nitre,
are applicable to Gold also. And if Silver be alloyed with Gold before
it undergo those several operations, it will still remain alloyed
therewith after them, in the same manner, and in the same quantity;
because both metals bear them equally. All therefore that can be
expected from those several assays, is the separation of every thing
that is neither Silver nor Gold from these two metals. But in order to
separate these two from each other, recourse must be had either to the
process laid down under the head of Gold, or to that here described,
which is the most commodious, the most usual, and known by the names of
_Quartation_ and the _Parting Assay_.

_Aqua fortis_ is the true solvent of Silver, and is utterly incapable
of dissolving the least atom of Gold. If therefore a mass consisting of
Gold and Silver be exposed to the action of _aqua fortis_, that Acid
will dissolve the Silver contained in the compound, without touching
the Gold, and the two metals will be separated from each other. This
method of parting them is just the reverse of that described before
under the head of Gold, which is effected by the means of _aqua regis_.

To the success of this separation, by means of _aqua fortis_, several
conditions are essentially necessary. The first is, that the Gold and
Silver be in due proportion to each other; that is, there must be at
least twice as much Silver as Gold in the metalline mass, otherwise the
_aqua fortis_ will not be able to dissolve it, for the reason formerly
given. If therefore the mass contain too little Silver, it must either
be melted down again, and a proper quantity of Silver added; or else,
if the Gold be in a sufficient proportion to the Silver, they may be
parted by means of _aqua regis_.

Secondly, it is necessary that the _aqua fortis_ employed in this
operation be absolutely pure, and free from any taint of the Vitriolic
or Marine Acid: for, if it be adulterated with the Vitriolic Acid,
the Silver will precipitate as fast as it dissolves, and so the
precipitated Silver will again mix with the Gold. If the _aqua fortis_
contain any of the Marine Acid, the Silver will be precipitated in
that case also; and this inconvenience will be attended with another,
namely, that the menstruum, being partly an _aqua regis_, will dissolve
some of the Gold. You must therefore be very sure that your _aqua
fortis_ is pure, before you set about the operation. In order to
discover its quality, you must try it by dissolving, in a small portion
thereof, as much Silver as it will take up: if the _aqua fortis_ grow
opaque and milky as it dissolves the Silver, it is a sign it contains
some foreign Acid, from which it must be purified.

In order to effect this, let the portion of _aqua fortis_ used for the
above trial stand to settle: the white milky part will gradually fall
to the bottom of the vessel. When it is all fallen, gently decant the
clear liquor, and pour a few drops of this decanted solution of Silver
into the _aqua fortis_ which you want to purify. It will instantly
become milky. Let the white particles precipitate as before, and then
add a few more drops of your solution of Silver. If the _aqua fortis_
still become milky, let it precipitate again, and repeat this till you
find that a drop of your solution of Silver, let fall into this _aqua
fortis_, does not make it in the least turbid. Then filter it through
brown paper, and you will have an _aqua fortis_ perfectly fit for the
Parting Assay.

The white particles that appear and settle to the bottom, on dissolving
silver in an _aqua fortis_ adulterated with a mixture of some foreign
Acid, are no other than that very Silver, which is no sooner dissolved
by the Nitrous Acid than it deserts that solvent to unite with the
Vitriolic or Marine Acid, wherewith it has a greater affinity, and
falls to the bottom with them. And this happens as long as there
remains in the _aqua fortis_ a single atom of either of those two Acids.

When therefore your _aqua fortis_ hath dissolved as much Silver as it
is capable of taking up, and when all the white particles formed during
the dissolution are settled to the bottom, you may be assured that
the portion which remains clear and limpid is a solution of Silver in
an exceeding pure _aqua fortis_. But if the solution of Silver thus
depurated be mixed with an _aqua fortis_ adulterated with the Vitriolic
or Marine Acid, a like precipitation will immediately ensue, for the
reasons above given, till the very last particle of the heterogeneous
Acid contained in the _aqua fortis_ be precipitated.

_Aqua fortis_ purified by this method contains no extraneous substance
whatever, except a small portion of Silver; so that it is very fit for
the parting process. But if it be intended for other chymical purposes,
it must be rectified in a glass retort with a moderate heat, in order
to separate it from the small portion of Silver it contains, which will
remain at the bottom of the retort.

The third condition necessary to the success of this operation is, that
your _aqua fortis_ be neither too aqueous, nor too highly concentrated.
If too weak, it will not act upon the Silver: and the consequence will
be the same if it be too strong. Both these inconveniencies are easily
remedied: for in the former case part of the superfluous phlegm may be
drawn off by distillation; or a sufficient quantity of much stronger
_aqua fortis_ may be mixed with that which is too weak: and, in the
latter case, very pure rain water, or a weaker _aqua fortis_, may be
mixed with that which is too strong.

You may satisfy yourself whether or no your _aqua fortis_ hath the
requisite degree of strength, by dissolving therein a thin plate
consisting of one part Gold and two or three parts Silver; which plate
must be rolled up in form of a paper coffin. If, when all the Silver
contained in the plate is dissolved, the Gold remains in the form
of the coffin, it is a sign that your solvent has a due degree of
strength. If, on the contrary, the Gold be reduced to a powder, it is a
proof that your _aqua fortis_ is too strong, and ought to be weakened.

The Gold remaining after the dissolution of the Silver must be melted
in a crucible with Nitre and Borax, as hath already been said under the
process for parting Gold and Silver by means of _aqua regis_. As to the
Silver which remains dissolved in the _aqua fortis_, there are several
ways to recover it.

The most usual is to precipitate it by the interposition of Copper,
which hath a greater affinity than Silver with the Nitrous Acid[7].
For this purpose the solution is weakened by adding twice or thrice as
much very pure rain water. The cucurbit containing the solution is set
on a sand-bath gently heated, and very clean plates of copper put into
it. The surfaces of these plates are soon covered with little white
scales, which gradually fall to the bottom of the vessel, as they come
to be collected in quantities. It is even proper to strike the cucurbit
gently now and then, in order to shake the scales of Silver from the
copper plates, and so make room for a new crop.

  [7] See the Table of Affinities, Column IV.

The _aqua fortis_ parts with the Silver by degrees only, as it
dissolves the Copper; and therefore the liquor gradually acquires a
blueish green colour as the precipitation advances. This precipitation
of the Silver is to be continued as long as any remains dissolved in
the _aqua fortis_: you may be sure that your liquor contains no more
Silver, if the surface of a fresh plate of Copper laid therein remain
clean and free from ash-coloured or greyish particles: or if one drop
of a solution of Sea-salt let fall into it produce no white or milky
cloud.

The precipitation being finished, the liquor is to be gently poured off
from the precipitated Silver, which must be rinsed in several waters,
and even made to boil therewith, in order to free it wholly from the
dissolved Copper. The Silver thus well washed must be thoroughly dried,
mixed with a fourth part of its weight of a flux compounded of equal
parts of Nitre and calcined Borax, and then melted in a crucible.
On this occasion care must be taken to raise the fire gently and
gradually, till the Silver be brought to fusion.

With what accuracy soever the precipitated Silver be washed, in order
to free it from the solution of Copper, yet the Silver will always be
found alloyed with a small portion of the Copper: but then this Copper
is easily destroyed by the Nitre, with which the Silver is afterwards
melted; so that the latter metal remains perfectly pure after the
operation.

Though the Silver be not previously cupelled, but be alloyed with
other metallic substances at the time it is thus dissolved, yet
the dissolving, precipitating, and fusing it with Nitre, would be
sufficient to separate it accurately from them all, and refine it to a
degree of purity equal to that obtained by the cupel.

The Copper that remains dissolved in the _aqua fortis_, after the
precipitation of the Silver, may in like manner be precipitated by
Iron, and, as it retains a small portion of Silver, ought not to
be neglected when these operations are performed on considerable
quantities.

In the two next processes we shall shew two other methods of separating
Silver from _aqua fortis_.


PROCESS V.

_To separate Silver from the Nitrous Acid by Distillation. Crystals of
Silver. The Infernal Stone._

Into a large, low, glass body put the solution of Silver, from which
you intend to separate the Silver by distillation. To this body fit
a tubulated head provided with its stopple. Set this alembic in a
sand-bath, so that the body may be almost covered with sand: apply
a receiver, and distil with a moderate heat, so that the drops may
succeed each other at the distance of some seconds. If the receiver
grow very hot, check the fire. When red vapours begin to appear, pour
into the alembic, through the hole in its head, a fresh quantity of
your solution of Silver, first made very hot. Continue distilling in
this manner, and repeating the addition of fresh liquor, till all your
solution be put into the alembic. When you have no more fresh solution
to put in, and when, the phlegm being all come over, red vapours begin
again to appear, convey into the alembic half a dram or a dram of
tallow, and distil to dryness; which being done, increase your fire so
as to make the vessel containing the sand-bath red-hot. In the alembic
you will find a calx of Silver, which must be melted in a crucible with
some soap and calcined wine-lees.


_OBSERVATIONS._

A low cucurbit is recommended for this operation, to the intent that
the particles of the Nitrous Acid, which are ponderous, may the more
easily be carried up and pass over into the receiver. For the same
reason the cucurbit is directed to be almost wholly covered with sand,
lest otherwise the acid vapours should be condensed about that part of
the cucurbit, which, being out of the sand, would be much cooler than
that which is encompassed therewith, and from thence should fall back
again to the bottom; by which means the distillation would certainly be
retarded, and the vessel probably be broken.

Notwithstanding these precautions the vessels are liable to break
in such distillations; especially when they contain a great deal of
liquor. With a view, therefore, to prevent this accident, we ordered
that the whole quantity of the solution of Silver to be distilled
should not be put at once into the alembic. The little bit of tallow,
added towards the end of the operation, is intended to hinder the metal
from adhering closely to the vessel, as it would otherwise do, when all
the moisture is dissipated.

The Soap and Fixed Alkali mixed with the Silver to flux it, after its
separation from the _aqua fortis_ in this way, serve to absorb such of
the most fixed particles of the Acid as may still remain united with
the metal.

If the distillation be stopped when part of the phlegm is drawn off,
and the liquor be then suffered to cool, many crystals will shoot
therein, which are a Neutral Salt constituted of the Nitrous Acid and
Silver. If the distillation be carried further, and stopped when near
its conclusion, the liquor being then suffered to cool will wholly
coagulate into a blackish mass called the _Infernal Stone_.

This way of separating Silver from its solvent is attended with the
advantage of saving all the _aqua fortis_, which is excellent, and fit
to be employed in other operations.


PROCESS VI.

_To separate Silver from the Nitrous Acid by Precipitation._ Luna
Cornea. Luna Cornea _reduced_.


Into your solution of Silver pour about a fourth part in weight of
Spirit of Salt, solution of Sea-salt, or solution of Sal Ammoniac. The
liquor will instantly become turbid and milky. Add twice or thrice
its weight of fair water, and let it stand some hours to settle. It
will deposite a white powder. Decant the clear liquor, and on the
precipitate pour fresh _aqua fortis_, or Spirit of Salt, and warm
the whole on a sand-bath with a gentle heat for some time. Pour off
this second liquor, and boil your precipitate in pure water, shifting
it several times, till the precipitate and the water be both quite
insipid. Filter the whole, and dry the precipitate, which will be a
_Luna Cornea_, and must be reduced in the following manner.

Smear the inside of a good crucible well with soap. Put your _Luna
Cornea_ into it; cover it with half its weight of Salt of Tartar,
thoroughly dried and pulverized; press the whole hard down; pour
thereon as much oil, or melted tallow, as the powder is capable of
imbibing; set the crucible thus charged, and close covered, in a
melting furnace, and, for the first quarter of an hour, make no more
fire than is necessary to make the crucible moderately red: after that
raise it so as to melt the Silver and the Salt, throwing into the
crucible from time to time little bits of tallow. When it ceases to
smoke, let the whole cool; or pour it into a hollow iron cone, warmed
and tallowed.


_OBSERVATIONS._

The process here delivered furnishes us with the means of procuring
Silver in a degree of purity which is not to be obtained by any other
method of treating it whatever. That which is refined on the cupel
always retains a small portion of Copper, from which it cannot possibly
be separated in that way: but if it be dissolved in _aqua fortis_,
and precipitated thence in a _Luna Cornea_ by the Marine Acid, the
precipitate will be an absolutely pure Silver, unalloyed with that
small portion of Copper which is retained on the cupel. The reason of
this effect is, that the Copper remains as perfectly dissolved in
Spirit of Salt and in _aqua regia_ as in _aqua fortis_: so that when
the Silver, and the Copper with which it is alloyed, are dissolved
together in the Nitrous Acid, if the Acid of Sea-salt be mixed with
the solution, part of this latter Acid unites with the Silver, and
therewith forms a new compound, which not being soluble in the liquor,
falls to the bottom. The other part of the Acid mixing with the
Nitrous, forms an _aqua regis_, in which the Copper remains dissolved,
without separating from it.

Fresh Acid is poured on the precipitated calx of Silver, in order to
complete the solution of the small portion of Copper that may have
escaped the action of the first solvent. It is indifferent whether
the Spirit of Salt or the Spirit of Nitre be employed for this
purpose, because they both dissolve Copper alike, and because Silver
precipitated by Spirit of Salt is not soluble in either.

After this it is necessary to wash the precipitate well with pure
water, in order to free it entirely from the particles of _aqua fortis_
adhering to the Silver; because they may possibly contain something
of Copper, which would mix with the Silver in melting, and taint its
purity.

If this precipitate of Silver be exposed to the fire, unmixed with any
other substance, it melts as soon as it begins to be red; and, if the
fire be increased, part thereof will be dissipated in vapours, and the
rest will make its way through the crucible. But being poured out as
soon as melted, it coagulates into a cake of a purplish red colour,
semi-transparent, ponderous, and in some degree pliable, especially
if it be very thin. It bears some resemblance to horn, which hath
occasioned it to be called _Luna Cornea_.

As _Luna Cornea_ is not soluble in water, recourse must be had to
fusion, in order to reduce it, by separating from the Silver those
acids which give it the above-mentioned properties. Fixed Alkalis and
fatty matters are very fit to produce that separation.

We directed that the inside of the crucible, in which the reduction is
to be made, should be carefully smeared with soap, and that the _Luna
Cornea_ should be quite covered with a Fixed Alkali and fat, to the end
that when the heat is strong enough to dissipate it in vapours, or to
attenuate it so as to render it capable of penetrating the crucible, it
may be forced to pass through matters qualified to absorb its Acid, and
reduce it.

_Luna Cornea_ may also be reduced by being melted with such metalline
substances as have a greater affinity than Silver with the Acids
wherewith it is impregnated. Of this kind are Tin, Lead, Regulus of
Antimony: but the _Luna Cornea_ rushes so impetuously into conjunction
with those metalline substances, that a vast many vapours arise, and
carry off with them part of the Silver: if therefore you chuse to
effect the reduction by the interposition of such metalline substances,
you must employ a retort instead of a crucible.

But this method is attended with another inconvenience; which is, that
some part of those metalline substances may unite with the Silver, and
adulterate it: for which reason it is best to keep to the method first
proposed.



PROCESS VII.

_To dissolve Silver, and separate it from Gold, by Cementation._


Mix thoroughly together fine brick-dust four parts, Vitriol calcined to
redness one part, and Sea-salt or Nitre one part. Moisten this powder
with a little water. With this cement cover the bottom of a crucible
half an inch thick; on this first bed lay a thin plate of the mass of
Gold and Silver you intend to cement, and which you must previously
take care to beat into such thin plates. Cover this plate with a second
layer of cement, of the same thickness as the former; on this second
bed lay another plate of your metal; cover it in like manner with
cement; and so proceed till the crucible be filled to within half an
inch of its brim. Fill up the remaining space with cement, and close
the crucible with a cover, luted with a paste made of Windsor-loam and
water: set your crucible thus charged in a furnace, whose fire-place
is deep enough to let it be entirely surrounded with coals, quite up to
its mouth. Light some coals in the furnace, taking care not to make the
fire very brisk at first; increase it by degrees, but only so far as to
make the crucible moderately red; keep up the fire in this degree for
eighteen or twenty hours: then let the fire go out; open the crucible
when it is cold, and separate the cement from your plates of Gold.
Boil the Gold repeatedly in fair water, till the water come off quite
insipid.


_OBSERVATIONS._

It cannot but seem strange, that, after having so often declared the
Acid of Sea-salt to be incapable of dissolving Silver, we should
direct either Nitre or Sea-salt indifferently to be employed in
composing a cement, which is to produce an Acid capable of eating
out all the Silver mixed with Gold. It is easy to conceive how the
Nitrous Acid extricated from its basis by means of the Vitriolic Acid
may produce this effect: but if Sea-salt instead of Nitre be made an
ingredient in the cement, its Acid, though set at liberty in the same
manner by the Vitriolic Acid, must at first sight appear unable to
answer the end.

In order to remove this difficulty, we must here observe, that there
are two very essential differences between the Marine Acid collected
in a liquor, as it is when distilled in the usual manner, and the same
Acid separated from its basis in a crucible, as it is in cementation.

The first of these two differences is, that the Acid being reduced
into vapours when it acts on the Silver in cementation, its activity
is thereby greatly increased: the second is, that in the crucible it
sustains a vastly greater degree of heat than it can ever bear when
it is in the form of a liquor. For, after it is once distilled and
separated from its basis, it cannot sustain any extraordinary degree
of heat without being volatilized and entirely dissipated: whereas,
while it continues united with its basis, it is much more fixed, and
cannot be separated but by a very intense heat. Consequently, if it
meet with any body to dissolve, at the very instant of its separation
from its basis, while it is actuated by a much fiercer heat than can
ever be applied to it on any other occasion, it must operate upon that
body with so much the more efficacy: and thus it comes to pass, that in
cementation it has the power of dissolving Silver, which it would be
incapable of touching if it were not so circumstanced.

But herein Gold differs from Silver: for, whatever force the Nitrous
or the Marine Acid may exert, when extricated from their bases in the
cementing crucible, this metal obstinately refuses to yield to either
of those Acids separately, and can never be dissolved by them, unless
both be united together.

Our cementation, therefore, is actually a parting process in the dry
way. The Silver is dissolved, and the Gold remains unaltered. Nay, as
the action of the Acids is much stronger when they are applied this
way, than when they are used for dissolution in the moist way, the
Nitrous Acid, which in the common parting process will not dissolve
Silver unless its weight be double that of the Gold, is able in
cementation to dissolve a very small quantity of Silver diffused
through a large quantity of Gold.

It sometimes happens, that after the operation the cement proves
extremely hard, so that it is very troublesome to separate it entirely
from the Gold. In this case it must be softened by moistening it with
hot water. This hardness which the cement acquires is occasioned by
the fusion of the Salts, which is the effect of too strong a heat. It
was in order to prevent this, and that a due degree of heat might be
applied, without the danger of melting the salts, that we directed
the cement to be mixed with a considerable quantity of earthy matter
incapable of fusion, such as brick-dust. A greater inconvenience will
ensue, if the fire be made so strong as to melt the Gold: for then it
will partly commix again with the other metalline substances dissolved
by the cement, and consequently will not be purified.

The crucible is covered, and its cover luted on, to prevent the acid
vapours from being too soon dissipated, and to force them to circulate
the longer in the crucible. However, it is necessary that those vapours
should find a vent at last, otherwise they would burst the vessel:
and for this reason we directed the crucible to be luted only with
Windsor-loam, which does not grow very hard by the action of fire, and
so is capable of yielding and giving passage to the vapours, when a
certain quantity of them is collected in the crucible, and they begin
to struggle for an escape on every side.

When the operation is finished, the Silver dissolved by the Acid of
the cement is partly distributed through the cement, and partly in the
Gold itself, which is impregnated therewith. For this reason the Gold
must be washed several times in boiling water, till the water become
absolutely insipid: for, if the Gold be melted without this precaution,
it will mix again with the Silver: the cement also may be washed in the
same manner to recover the Silver it contains.

Though this cementation be, properly speaking, a purification of
Gold, yet we have placed it among the processes on Silver, because it
is the Silver that is dissolved on this occasion, and because this
is a particular way of dissolving that metal. Moreover, most of the
processes hitherto delivered, either on Gold or Silver, are equally
applicable to both these metals.

If the Gold do not appear quite pure after the cementation, the process
must be repeated.

There are several ways to know the fineness of Gold, the quantity of
Silver with which it is alloyed, and the proportion in which these two
metals are mixed in a mass purified by the cupel.

One of the simplest is the trial by the Touch-stone; which indeed is
hardly any more than judging by the eye only, from the colour of the
compound metal, what proportion of Gold and Silver it contains.

The Touch-stone is a sort of black marble, whose surface ought to be
half polished. If the metalline mass which you want to try be rubbed
on this stone, it leaves thereon a thin coat of metal, the colour of
which may be easily observed. Such as are accustomed to see and handle
Gold and Silver can at once judge very nearly from this sample in what
proportion the two metals are combined: but, for greater accuracy,
those who are in the way of having frequent occasion for this trial
are provided with a sufficient number of small bars or needles, of
which one is pure Gold, another pure Silver, and all the rest consist
of these two metals mixed together in different proportions, varied
by carats, or even by fractions of carats, if greater exactness be
required.

The fineness of each needle being marked on it, that needle whose
colour seems to come nearest the colour of the metalline streak on the
Touch-stone, is rubbed on the stone by the side of that streak. This
needle likewise leaves a mark; and if there appear to be no difference
between the two metalline streaks, the metalline mass is judged to be
of the same fineness as the needle thus compared with it. If the eye
discovers a sensible difference, another needle is sought for whose
colour may come nearer to that of the metal to be tried. But though
a man be ever so well versed in judging thus of the fineness of Gold
by the eye only, he can never be perfectly and accurately sure of it
by this means alone. If such certainty be required, recourse must be
had to the parting assay; and yet when you have gone through it, there
always remains a small quantity of the metal, which should have been
dissolved, and yet escaped the action of the solvent. For example,
if you make use of _aqua regis_, the Silver that remains after the
operation still contains a little Gold; and, if you make use of _aqua
fortis_, the Gold that remains after the operation still contains a
little Silver. And therefore if you resolve to carry the separation
of these two metals still further by solvents, it will be necessary,
after you have gone through one parting process, to perform a second
the contrary way. For example, if you begin with _aqua fortis_, then,
after it has dissolved all the Silver in the metalline mass that it is
capable of taking up, dissolve the remaining Gold in _aqua regis_: by
which means you will separate the small portion of Silver left in it by
the _aqua fortis_. The contrary is to be done if you made use of _aqua
regis_ first.



CHAP. III.

_Of_ COPPER.


PROCESS I.

_To separate Copper from its Ore._

Beat your Copper ore to a fine powder, having first freed it as
accurately as possible, by washing and roasting, from all stony,
earthy, sulphureous, and arsenical parts. Mix your ore thus pulverized
with thrice its weight of the black flux; put the mixture into a
crucible; cover it with common salt to the thickness of half an inch,
and press the whole down with your finger. With all this the crucible
must be but half full. Set it in a melting furnace; kindle the fire by
degrees, and raise it insensibly till you hear the Sea-salt crackle.
When the decrepitation is over, make the crucible moderately red-hot
for half a quarter of an hour. Then give a considerable degree of heat,
exciting the fire with a pair of good perpetual bellows, so that the
crucible may become very red-hot, and be perfectly ignited. Keep the
fire up to this degree for about a quarter of an hour; then take out
the crucible, and with a hammer strike a few blows on the floor whereon
you set it. Break it when cold. If the operation hath been rightly and
successfully performed, you will find at the bottom of the vessel a
hard Regulus, of a bright yellow colour, and semi-malleable; and over
it a scoria of a yellowish brown colour, hard and shining, from which
you may separate the Regulus with a hammer.


_OBSERVATIONS._

Copper in the ore is often blended with several other metallic
substances, and with volatile minerals, such as Sulphur and Arsenic.
Copper ores also frequently participate of the nature of the pyrites,
containing a martial and an unmetallic earth, both of which are
entirely refractory, and hinder the ore from melting. In this case you
must add equal parts of a very fusile glass, a little borax, and four
parts of the black flux, to facilitate the fusion. The black flux is
moreover necessary to furnish the Copper with the Phlogiston it wants,
or restore so much thereof as it may lose in melting. For the same
reason, when any ore, but that of Gold or Silver, is to be smelted, it
is a general rule to add some black flux, or other matter abounding
with Phlogiston.

The Regulus produced by this operation is not malleable, because it is
not pure Copper, but a mixture of Copper with all the other metallic
substances that were in the ore; except such as were separated from it
by roasting, of which it contains but little.

According to the nature of the metallic matters that remain combined
with the Copper after this fusion, the colour of the Regulus is
either like that of pure Copper, or a little more whitish: it is also
frequently blackish, which has procured it the name of _Black Copper_.
In this state, and even in general, it is usual enough to call this
Regulus by the name of Black Copper, when alloyed with other metallic
substances that render it unmalleable, whatever its colour be.

Hence it appears that there may be several different sorts of Black
Copper. Iron, Lead, Tin, Bismuth, and the reguline part of Antimony,
are almost always combined with the ores of Copper, in a multitude of
different proportions; and all these substances, being reduced by the
black flux in the operation, mix and precipitate with the Copper. If
the ore contain any Gold or Silver, as is pretty often the case, these
two metals also are confounded with the rest in the precipitation, and
become part of the Black Copper.

Pyritose, sulphureous, and arsenical Copper ores may be fused, in order
to get rid of the grosser heterogeneous parts, without previously
roasting them: but in this case no alkaline flux must be mixed with the
ore; because the Alkali in combination with the Sulphur would produce
a Liver of Sulphur, and so dissolve the metalline part; by which means
all would be confounded together, and no Regulus, or very little, be
precipitated. On this occasion therefore nothing must be added to
promote the fusion, but some tender fusile glass, together with a small
quantity of borax.

This first fusion may also be performed amidst the coals, by casting
the ore upon them in the furnace, without using a crucible; and then an
earthen vessel, thoroughly heated, or even made red-hot, must be placed
under the grate of the fire-place, to receive the metal as it runs from
the ore.

The Regulus obtained by this means is much more impure and brittle
than Black Copper, because it contains moreover a large quantity of
Sulphur and Arsenic; as these volatile substances have not time to
evaporate during the short space requisite to melt the ore, and as they
cannot be carried off by the action of the fire after the ore is once
melted, whatever time be allowed for that purpose. However, some part
thereof is dissipated; and the Iron which is in pyritose ores, having a
much greater affinity than Copper, and indeed than any other metallic
substance, with Sulphur and Arsenic, absorbs another part thereof, and
separates it from the Regulus.

This Regulus, it is plain, still contains all the same parts that were
in the ore, but in different proportions; there being more Copper,
combined with less Sulphur, Arsenic, and unmetallic earth, which have
been either dissipated or turned to slag. Therefore, if you would make
it like Black Copper, you must pound it, roast it over and over, to
free it from its Sulphur and Arsenic, and then melt it with the black
flux.

If this Regulus contain much Iron, it will be adviseable to melt it
once or twice more, before all the Sulphur and Arsenic are separated
from it by roasting; for as the Iron, by uniting with these volatile
substances, separates them from the Copper, with which they have not so
great an affinity; so also the Sulphur and Arsenic, by uniting with the
Iron, help in their turn to separate it from the Copper.


PROCESS II.

_To purify Black Copper, and render it malleable._

Break into small bits the Black Copper you intend to purify; mix
therewith a third part in weight of granulated Lead, and put the
whole into a cupel set under the muffle in a cupelling furnace, and
previously heated quite red. As soon as the metals are in the cupel
raise the fire considerably, making use, if it be needful, of a pair of
perpetual bellows, to melt the Copper speedily. When it is thoroughly
melted, lower the fire a little, and continue it just high enough to
keep the metalline mass in perfect fusion. The melted matter will then
boil, and throw up some _scoriæ_, which will be absorbed by the cupel.

When most of the Lead is consumed, raise the fire again, till the face
of the Copper become bright and shining, thereby shewing that all its
alloy is separated. As soon as your Copper comes to this state, cover
it with charcoal-dust conveyed into the cupel with an iron ladle: then
take the cupel out of the furnace and let it cool.


_OBSERVATIONS._

Of all the metals, next to Gold and Silver, Copper bears fusion the
longest without losing its phlogiston; and on this property is founded
the process here delivered for purifying it.

It is necessary the Copper should melt as soon as it is in the cupel,
because its nature is to calcine much more easily and much sooner,
when it is only red-hot, than when it is in fusion. For this reason
the fire is to be considerably raised, immediately on putting the
Copper under the muffle, that it may melt as soon as possible. Yet too
violent a degree of fire must not be applied to it: for when it is
exposed to such a degree of heat only as is but just necessary to keep
it in fusion, it is then in the most favourable condition for losing
as little as may be of its phlogiston; and if the heat be stronger,
a greater quantity thereof will be calcined. As soon therefore as it
flows it is proper to weaken the fire, and reduce it to the degree just
requisite to keep up the fusion.

The Lead added on this occasion is intended to facilitate and expedite
the scorification of the metallic substances combined with the Copper.
So that the event is here nearly the same as when Gold or Silver is
refined on the cupel. The only difference between this refining of
Copper, and that of the perfect metals, is that the latter as hath been
shewn, absolutely resist the force of fire and the action of Lead,
without suffering the least alteration; whereas a good deal of Copper
is calcined and destroyed, when it is purified in this manner on the
cupel. Indeed it would be wholly destroyed, if a greater quantity of
Lead were added, or if it were left too long in the furnace. It is with
a view to save as much of it as possible that we order it to be covered
with charcoal-dust as soon as the scorification is finished.

The Lead serves moreover to free the Copper expeditiously from the
Iron with which it may be alloyed. Iron and Lead are incapable of
contracting any union together: so that as fast as the Lead unites with
the Copper, it separates the Iron, and excludes it out of the mixture.
For the same reason if Iron were combined in a large proportion with
Copper, it would prevent the Lead from entering into the composition.
Now, as it is necessary to give the more heat, and to keep the Copper
to be incorporated with Lead the longer in fusion, as that Copper is
alloyed with a greater proportion of Iron, some black flux must be
added on this occasion, to prevent the Copper and the Lead from being
calcined before their association can be effected.

Copper purified in the manner here directed is beautiful and malleable.
It is now alloyed with no other metalline substance but Gold or Silver,
if there were any in the mixed mass. If you desire to extract this Gold
or Silver, recourse must be had to the operation of the cupel. The
process here given for purifying Copper is not used in large works,
because it would be much too chargeable. In order to purify their Black
Copper, and render it malleable, the smelters content themselves with
roasting it, and melting it repeatedly, that the metallic substances,
which are not so fixed as Copper, may be dissipated by sublimation, and
the rest scorified by fusion.


PROCESS III.

_To deprive Copper of its Phlogiston by calcination._

Put your Copper in filings into a test, and set it under the muffle of
a cupelling furnace; light the fire, and keep up such a degree of heat
as may make the whole quite red, but not enough to melt the Copper.
The surface of the Copper will gradually lose its metalline splendour,
and put on the appearance of a reddish earth. From time to time stir
the filings with a little rod of copper or iron, and leave your metal
exposed to the same degree of fire till it be entirely calcined.


_OBSERVATIONS._

In our observations on the preceding process we took notice that
Copper, in fusion, calcines more slowly, and less easily, than when it
is exposed to a degree of fire barely sufficient to keep it red-hot,
without melting it; and therefore, the design here being to calcine it,
we have directed that degree of heat only to be applied.

The cupelling furnace is the fittest for this operation, because the
muffle is capable of receiving such a flat vessel as ought to be used
on this occasion, and communicating to it a great deal of heat; while,
at the same time, it prevents the falling in of any coals, which, by
furnishing the Copper with fresh phlogiston, would greatly prejudice
and protract the operation.

As Copper calcines with great difficulty, this operation is extremely
tedious: nay, though Copper hath stood thus exposed to the fire
for several days and nights, and seems perfectly calcined, yet it
frequently happens that, when you try afterwards to melt it, some of
it resumes the form of Copper: a proof that all the Copper had not
lost its phlogiston. Copper is much more expeditiously deprived of its
phlogiston by calcining it in a crucible with Nitre.

The calx of Copper perfectly calcined is with great difficulty brought
to fusion: yet, in the focus of a large burning-glass, it melts and
turns to a reddish and almost opaque glass.

By the process here delivered, you may likewise calcine all other
metalline substances, which do not melt till they are thoroughly
red-hot. As to those which melt before they grow red, they are easily
enough calcined, even while they are in fusion.


PROCESS IV.

_To resuscitate the Calx of Copper, and reduce it to Copper, by
restoring its Phlogiston._

Mix the Calx of Copper with thrice as much of the black flux; put the
mixture into a good crucible, so as to fill two thirds thereof, and
over it put a layer of Sea-salt a finger thick. Cover the crucible, and
set it in a melting furnace; heat it gradually, and keep it moderately
red till the decrepitation of the Sea-salt be over. Then raise the fire
considerably by means of a good pair of perpetual bellows; satisfy
yourself that the matter is in perfect fusion, by dipping into the
crucible an iron wire; continue the fire in this degree for half a
quarter of an hour. When the crucible is cold, you will find at its
bottom a button of very fine Copper, which will easily separate from
the saline scoria at top.


_OBSERVATIONS._

What hath been said before on the smelting of Copper ores may be
applied to this process, as being the very same. The observations there
added should therefore be consulted on this occasion.


PROCESS V.

_To dissolve Copper in the Mineral Acids._

On a sand-bath, in a very gentle heat, set a matrass containing some
Copper filings; pour on them twice their weight of Oil of Vitriol. That
Acid will presently attack the Copper. Vapours will rise, and issue
out of the neck of the matrass. A vast number of bubbles will ascend
from the surface of the metal to the top of the liquor, and the liquor
will acquire a beautiful blue colour. When the Copper is dissolved, put
in a little and a little more, till you perceive the Acid no longer
acts upon it. Then decant the liquor, and let it stand quiet in a cool
place. In a short time great numbers of beautiful blue crystals will
shoot in it. These crystals are called _Vitriol of Copper_, or _Blue
Vitriol_. They dissolve easily in water.


_OBSERVATIONS._

The Vitriolic Acid perfectly dissolves Copper, which is also soluble in
all the Acids, and even in many other menstruums.

This Acid may be separated from the Copper which it hath dissolved by
distillation only: but the operation requires a fire of the utmost
violence. The Copper remaining after it must be fused with the black
flux, to make it appear in its natural form; not only because it still
retains a portion of the Acid, but also because it hath lost part of
its phlogiston by being dissolved therein. The black flux is very well
adapted both to absorb the Acid that remains united with the Copper,
and to restore the phlogiston which the metal hath lost.

The most usual method of separating Copper from the Vitriolic Acid
is by presenting to that Acid a metal with which it hath a greater
affinity than with Copper. Iron being so qualified is consequently very
fit to bring about this separation. When therefore plates of Iron well
cleaned are laid in a solution of Blue Vitriol, the Acid soon begins to
act upon them, and by degrees, as it dissolves them, deposites on their
surfaces a quantity of Copper in proportion to the quantity of Iron it
takes up. The Copper thus precipitated hath the appearance of small
leaves or scales, exceeding thin, and of a beautiful copper-colour.
Care must be taken to shake the Iron-plates now and then, to make the
scales of Copper fall off, which will otherwise cover them entirely,
hinder the Vitriolic Acid from attacking the Iron, and so put a stop to
the precipitation of the remaining Copper.

When these scales of Copper cease to settle on the clean Iron
plates, you may be sure all the Copper that was in the liquor is
precipitated, and that this liquor, which was a solution of Copper
before the precipitation, is a solution of Iron after it. So that here
two operations are performed at one and the same time; to wit, the
precipitation of the Copper, and the dissolution of the Iron.

The Copper thus precipitated requires only to be separated from the
liquor by filtration, and melted with a little black flux, to become
very fine malleable Copper.

The Copper may also be precipitated out of a solution of Blue Vitriol
by the interposition of a Fixed Alkali. This precipitate is of a
greenish blue colour, and requires a much greater quantity of the black
flux to reduce it.

Copper dissolves in the Nitrous Acid, in the Marine Acid, and in _Aqua
regis_; from all of which it may be separated by the same methods as
are here ordered with regard to the Vitriolic Acid.



CHAP. IV.

_Of_ IRON.


PROCESS I.

_To separate Iron from its Ore._

Pound into a coarse powder the martial stones or earths out of which
you design to extract the Iron: roast this powder in a test under the
muffle for some minutes, and let your fire be brisk. Then let it cool,
beat it very fine, and roast it a second time, keeping it under the
muffle till it emit no more smell.

Then mix with this powder a flux composed of three parts of Nitre fixed
with Tartar, one part of fusile glass, and half a part of Borax and
charcoal-dust. The dose of this reducing flux must be thrice the weight
of the ore.

Put this mixture into a good crucible; cover it with about half a
finger thick of Sea-salt; over the crucible put its cover, and lute it
on with Windsor-loam made into a paste with water. Having thus prepared
your crucible, set it in a melting furnace, which you must fill up with
charcoal. Light the fire, and let it kindle by gentle degrees, till
the crucible become red-hot. When the decrepitation of the Sea-salt
is over, raise your fire to the highest by the blast of a pair of
perpetual bellows, or rather several. Keep up this intense degree of
heat for three quarters of an hour, or an whole hour, taking care that
during all this time the furnace be kept constantly filling up with
fresh coals as the former consume. Then take your crucible out of the
furnace; strike the pavement on which you set it several times with a
hammer, and let it stand to cool: break it, and you will find therein a
Regulus of Iron covered with slag.


_OBSERVATIONS._

Iron ore, like all others, requires roasting, to separate from it, as
much as possible, the volatile minerals, Sulphur and Arsenic, which
being mixed with the Iron would render it unmalleable. Indeed it is
so much the more necessary to roast these ores, as Iron is, of all
metallic substances, that which has the greatest affinity with those
volatile minerals; on which account no metallic substance whatever is
capable of separating it from them by fusion and precipitation.

Fixed Alkalis, it is true, have a greater affinity than Iron with
Sulphur; but then the composition which a Fixed Alkali forms with
Sulphur is capable of dissolving all metals. Consequently, if you do
not dissipate the Sulphur by roasting, but attempt to separate it from
the Iron by melting the ore with a Fixed Alkali, the Liver of Sulphur
formed in the operation will dissolve the martial part; so that after
the fusion you will find little or no Regulus.

All Iron ores in general are refractory, and less fusible than any
other; for which reason a much greater proportion of flux, and a much
more violent degree of fire, is required to smelt them. One principal
cause why these ores are so refractory is the property which Iron
itself has of being extremely difficult to fuse, and of resisting
the action of the fire so much the more as it is purer, and further
removed from its mineral state. Among all the metallic substances it is
the only one that is less fusible when combined with that portion of
phlogiston which gives it the metalline form, than when it is deprived
thereof, and in the form of a calx.

In smelting-houses Iron ore is fused amidst charcoal, the phlogiston
of which combines with the martial earth, and gives it the metalline
form. The Iron thus melted runs down to the bottom of the furnace, from
whence it is let out into large moulds, in which it takes the shape of
oblong blocks, called _Pigs_ of Iron. This Iron is still very impure,
and quite unmalleable. Its want of ductility after the first melting
arises partly from hence, that, notwithstanding the previous roasting
which the ore underwent, there still remains, after this first fusion,
a considerable quantity of Sulphur or Arsenic combined with the metal.

A certain quantity of quick-lime, or of stones that will burn to lime,
is frequently mixed with Iron ore on putting it into the smelting
furnace. The lime being an absorbent earth, very apt to unite with
Sulphur and Arsenic, is of use to separate those minerals from the Iron.

It is also of use to mix some such matters with the ore, when the
stones or earths which naturally accompany it are very fusible; for, as
the Iron is of difficult fusion, it may happen that the earthy matters
mixed with the Iron shall melt as easily as the metal, or perhaps
more easily. In such a case there is no separation of the earthy
from the metalline part, both of which melt and precipitate together
promiscuously; now quick-lime, being extremely refractory, serves on
this occasion to check the melting of those matters which are too
fusible.

Yet quick-lime, notwithstanding its refractory quality, may sometimes
be of use as a flux for Iron. This is the case when the ore happens to
be combined with substances which, being united with lime, render it
fusible: such are all arsenical matters, and even some earthy matters,
which being combined with quick-lime make a fusible compound.

When the ore of an Iron mine is found difficult to reduce, it is
usually neglected even though it be rich: because Iron being very
common, people chuse to work those mines only whose ores are smelted
with the most ease, and require the least consumption of wood.

Yet refractory ores are not to be altogether rejected, when another
Iron ore of a different quality is found near them. For it often
happens, that two several Iron ores, which being worked separately
are very difficult to manage, and yield at last but bad metal, become
very tractable, and yield excellent Iron, when smelted together: and
accordingly such mixtures are often made at Iron-works.

The Iron obtained from ores by the first fusion may be divided into two
sorts. The one, when cold, resists the hammer, doth not easily break,
and is in some measure extensible on the anvil; but, if struck with a
hammer when red-hot, flies into many pieces: this sort of Iron hath
always a mixture of Sulphur in it. The other sort, on the contrary, is
brittle when cold, but somewhat ductile when red-hot. This Iron is not
sulphurated, is naturally of a good quality, and its brittleness arises
from its metalline parts not being sufficiently compacted together.

Iron abounds so much, and is so universally diffused through the earth,
that it is difficult to find a body in which there is none at all: and
this hath led several Chymists, even men of great fame, into the error
of thinking that they had transmuted into Iron several sorts of earths
in which they suspected no Iron, by combining them with an inflammable
matter; whereas, in fact, all they did was to give the metalline form
to a true martial earth which happened to be mixed with other earths.


PROCESS II.

_To render Pig-iron and brittle Iron malleable._

Into an earthen vessel widening upwards put some charcoal-dust, and
thereon lay the Pig-iron which you propose to render ductile; cover it
all over with a quantity of charcoal; excite the fire violently with a
pair, or more, of perpetual bellows till the Iron melt. If it do not
readily flow and form a great deal of slag on its surface, add some
flux, such as a very fusible sand.

When the matter is in fusion keep stirring it from time to time, that
all the parts thereof may be equally acted on by the air and the fire.
On the surface of the melted Iron _scoriæ_ will be formed, which must
be taken off as they appear. At the same time you will see a great many
sparkles darted up from the surface of the metal, which will form a
sort of fiery shower. By degrees, as the Iron grows purer, the number
of these sparkles diminishes, though they never vanish entirely. When
but few sparkles appear, remove the coals which cover the Iron, and
let the slag run out of the vessel; whereupon the metal will grow
solid in a moment. Take it out while it is still red-hot, and give
it a few strokes with a hammer, to try if it be ductile. If it be
not yet malleable, repeat the operation a second time, in the same
manner as before. Lastly, when it is thus sufficiently purified by the
fire, work it for a long time on the anvil, extending it different
ways, and making it red-hot as often as there is occasion. Iron thus
brought to the necessary degree of ductility, so as to yield to the
hammer, and suffer itself to be extended every way, either hot or cold,
without breaking to bits, or even cracking in the least, is very good
and very pure. If it cannot be brought to this degree by the method
here prescribed, it is a proof that the ore from which this Iron was
extracted ought to be mixed with other ores; but it frequently requires
a great number of trials to obtain an exact knowledge of the quality
and proportion of those other ores with which it is to be mixed.


_OBSERVATIONS._

The brittleness and shortness of Pig-iron arises from the heterogeneous
parts which it contains, and which could not be separated from it
by the first fusion. These extraneous matters are usually Sulphur,
Arsenic, and unmetallic earth, and also a ferruginous earth; but
such as could not be combined with the phlogiston as it ought to be,
in order to have the properties of a metal, and must therefore be
considered as heterogeneous, with respect to the other well-conditioned
martial particles.

The Pig-iron, by undergoing repeated fusions, is freed from those
heterogeneous matters; those which are volatile, such as Sulphur and
Arsenic, being dissipated, and the unmetallic matters being scorified.
As to the ferruginous earth, which did not at first acquire the
metalline form, it becomes true Iron at last; because, among the coals
with which it is encompassed, it meets with a sufficient quantity of
phlogiston to reduce it to metal. Charcoal is also necessary on this
occasion, that it may continually furnish phlogiston to the Iron, which
would otherways be converted into a calx.

Hammering the red-hot Iron, after each fusion, serves to force out from
amongst the martial parts such earthy matters as may happen to remain
there, and so bring into closer contact the metalline parts which were
separated before by the interposition of those heterogeneous matters.


PROCESS III.

_To convert Iron into Steel._

Take small bars of the best Iron; that is, of such as is malleable both
hot and cold; set them on their ends in a cylindrical earthen vessel,
whose depth is equal to the length of the bars, and in such a manner
that they may be an inch distant from each other, and from the sides of
the crucible. Fill the vessel with a cement compounded of two parts of
charcoal, one part of bones burnt in a close vessel till they become
very black, and one half part of the ashes of green wood; having first
pulverized and thoroughly mixed the whole together. Take care to lift
up the Iron bars a little, to the end that the cement may cover the
bottom of the vessel, and so that there be about the depth of half an
inch thereof under every bar: cover the crucible and lute on the cover.

Set the crucible thus prepared in a furnace, so contrived that the
crucible may be surrounded with coals from top to bottom: for eight
or ten hours keep up such a degree of fire that the vessel may be
moderately red; after this take it out of the furnace; plunge your
little Iron bars into cold water, and you will find them converted into
Steel.


_OBSERVATIONS._

The principal difference between Iron and Steel consists in this, that
the latter is combined with a greater quantity of phlogiston than the
former.

It appears by this experiment, that, to make Iron unite with an
inflammable matter, it is not necessary it should be in fusion; it is
sufficient that it be so red-hot as to be opened and softened by the
fire.

Every kind of charcoal is fit to be an ingredient in the composition
of the cement employed to make Steel, provided it contain no Vitriolic
Acid. However, it hath been observed, that animal coals produce a
speedier effect than others: for which reason it is proper to mix
something of that kind with charcoal-dust, as above directed.

The following signs shew that the operation hath succeeded, and that
the Iron is changed into good Steel.

This metal being quenched in cold water, as proposed above, acquires
such an extraordinary degree of hardness, that it will by no means
yield to any impression of the file or hammer, and will sooner break
in pieces than stretch upon the anvil. And here it is proper to
observe, that the hardness of Steel varies with the manner in which it
is quenched. The general rule is, that the hotter the Steel is when
quenched, and the colder the water is in which you quench it, the
harder it becomes. It may be deprived of the temper thus acquired,
by making it red-hot, and letting it cool slowly; for it is thereby
softened, rendered malleable, and the file will bite upon it. For this
reason the artisans who work in Steel begin with untempering it, that
they may with more ease shape it into the tool they intend to make.
They afterwards new-temper the tool when finished, and by this second
temper the Steel recovers the same degree of hardness it had acquired
by the first temper.

The colour of Steel is not so white as that of Iron, but darker, and
the grains, facets, or fibres, which appear on breaking it, are finer
than those observed in Iron.

If the bars of Iron thus cemented in order to convert them into Steel
be too thick, or not kept long enough in cementation, they will not be
turned into Steel throughout their whole thickness: their surfaces only
will be Steel to a certain depth, and the center will be mere Iron;
because the phlogiston will not have thoroughly penetrated them. On
breaking a bar of this sort, the difference in colour and grain between
the Steel and the Iron is very visible.

It is easy to deprive Steel of the super-abundant quantity of phlogiston
which constitutes it Steel, and thereby reduce it to Iron. For this
purpose it need only be kept red-hot some time, observing that no
matter approach it all the while that is capable of refunding to it
the phlogiston which the fire carries off. The same end is still
sooner obtained by cementing it with meagre hungry matters, capable
of absorbing the phlogiston; such as bones calcined to whiteness, and
cretaceous earths.

Steel may also be made by fusion; or Pig-iron may be converted into
Steel. For this purpose the same method must be employed as was
above directed for reducing Pig-iron into malleable Iron; with this
difference, that, as Steel requires more phlogiston than is necessary
to Iron, all the means must be made use of that are capable of
introducing into the Iron a great deal of phlogiston; such as melting
but a small quantity of Iron at a time, and keeping it constantly
encompassed with abundance of charcoal; reiterating the fusions; taking
care that the blast of the bellows directed along the surface of the
metal do not remove the coals that cover it, _&c._ And here it must
be observed, that there are some sorts of Pig-iron which it is very
difficult to convert into Steel by this method, and that there are
others which succeed very readily, and with scarce any trouble at all.
The ores which yield the last-mentioned sort of Pig-iron are called
_Steel Ores_. Steel made by this means must be tempered in the same
manner as that made by cementation[8].

  [8] M. Réaumur hath obliged the public with a treatise on the means
  of converting Iron into Steel, in which he hath exhausted the subject.
  Such as desire the amplest and most useful instructions on that part
  of metallurgy, would do well to consult his Work.


PROCESS IV.

_The Calcination of Iron. Sundry Saffrons of Mars._

Take filings of Iron, in what quantity you please; put them into a
broad unglazed earthen vessel; set it under the muffle of a cupelling
furnace; make it red-hot; stir the filings frequently; and keep up the
same degree of fire till the Iron be wholly turned into a red powder.


_OBSERVATIONS._

Iron easily loses its phlogiston by the action of fire. The calx
that remains after its calcination is exceeding red; which makes
this be thought the natural colour of the earth of that metal. It
hath accordingly been observed, that all the earths and stones which
either are naturally red, or acquire that colour by calcination, are
ferruginous.

The yellowish red colour which every calx of Iron hath, in whatever
manner it be prepared, hath procured the name of _Crocus_ or _Saffron_
to every preparation of this kind. That made in the manner above
directed is called in Medicine _Crocus Martis astringens_.

The rust produced on the surface of Iron is a sort of calx of Iron made
by way of dissolution. The moisture of the air acts upon the metal,
dissolves it, and robs it of some of its phlogiston. This rust is
called in Medicine _Crocus Martis Aperiens_; because it is thought that
the saline parts, by means whereof the humidity dissolves the Iron,
remain united with the metal after its dissolution, and give it an
aperitive virtue. The Apothecaries prepare this sort of Saffron of Mars
by exposing Iron filings to the dew, till they be turned entirely to
rust: which is then called _Saffron of Mars by dew_.

Another Saffron of Mars is also prepared in a much shorter manner, by
mixing filings of Iron with pulverized Sulphur, and moistening the
mixture, which after some time ferments and grows hot. It is then set
on the fire; the Sulphur burns away, and the mass is kept stirring till
it become a red matter. This Saffron is nothing but Iron dissolved by
the Acid of Sulphur, which is known to be of the same nature with that
of Vitriol; and consequently this Saffron of Mars is no way differing
from Vitriol calcined to redness.


PROCESS V.

_Iron dissolved by the mineral Acids._

Put any mineral Acid whatever into a matrass with some water; set the
matrass on a sand-bath gently heated; drop into the vessel some filings
of Iron: the phenomena which usually accompany metalline dissolutions
will immediately appear. Add more filings, till you observe the Acid
hath lost all sensible action upon them: then remove your matrass from
the sand-bath; you will find in it a solution of Iron.


_OBSERVATIONS._

Iron is very easily dissolved by all the Acids. If you make use of the
Vitriolic Acid, care must be taken to weaken it with water, in case it
be concentrated; because the dissolution will succeed the better. The
vapours that rise on this occasion are inflammable; and if a lighted
paper be held to the mouth of the matrass, especially after keeping
it stopt for some time and shaking the whole gently, the sulphureous
vapours take fire with such rapidity as to produce a considerable
explosion; which is sometimes strong enough to burst the vessel into a
thousand pieces. This solution hath a green colour, and is in fact a
fluid Green Vitriol, which wants nothing but rest to make it shoot into
crystals.

If you make use of the Nitrous Acid, you must cease adding more filings
when the liquor, after standing still some moments, becomes turbid;
for, when this Acid is impregnated with Iron to a certain degree, it
lets fall some of that which it had dissolved, and becomes capable of
taking up fresh filings. Thus, by constantly adding new supplies of
Iron, this Acid may be made to dissolve a much greater quantity thereof
than is necessary to saturate it entirely. This solution is of a russet
colour, and doth not crystallize.

If the weather be not extremely cold, and the Acids have a proper
degree of strength, the sand-bath is unnecessary, as the dissolution
will succeed very well without it.

Iron dissolved by Acids may be separated therefrom, like all other
metallic substances in the same circumstances, either by the action
of fire, which carries off the Acid and leaves the Martial Earth, or
by the interposition of substances which have a greater affinity than
metallic substances have with Acids; that is, by Absorbent Earths
and Alkaline Salts. By whatever means you separate Iron from an Acid
solvent, it constantly appears, after the separation, in the form of
a yellowish red powder; because it is then deprived of most of the
phlogiston to which it owed its metalline form; whence it is reasonable
to think, that this is the proper colour of Martial earth.

All these precipitates of Iron are true Saffrons of Mars, which,
as well as those prepared by calcination, are so much the further
removed from the nature of a metal, the more they are deprived of
their phlogiston. Thence it comes that they are more or less soluble
by Acids, and more or less attracted by the magnet: as no ferruginous
earth, perfectly deprived of all inflammable matter, is at all
attracted by the magnet, or soluble by Acids.



CHAP. V.

_Of_ TIN.


PROCESS I.

_To extract Tin from its Ore._

Break your Tin ore into a coarse powder, and by washing carefully
separate from it all the heterogeneous matters, and ores of a different
kind, that may be mixed therewith. Then dry it, and roast it in a
strong degree of fire, till no more Arsenical vapour rise from it. When
the ore is roasted, reduce it to a fine powder, and mix it thoroughly
with twice its weight of the black flux well dried, a fourth part of
its weight of clean iron filings, together with as much borax and
pitch; put the mixture into a crucible; over all put Sea-salt to the
thickness of four fingers, and cover the crucible close.

Set the crucible thus prepared in a melting furnace: apply at first a
moderate and slow degree of fire, till the flame of the pitch, which
will escape through the joint of the cover, disappear entirely. Then
suddenly raise your fire, and urge it with rapidity to the degree
necessary for melting the whole mixture. As soon as the whole is in
fusion take the crucible out of the furnace, and separate the Regulus
from the scoria.


_OBSERVATIONS._

All Tin ores contain a considerable quantity of Arsenic, and no Sulphur
at all, or at most very little. Hence it comes that, though Tin be the
lightest of all metals, its ore is nevertheless much heavier than any
other; Arsenic being much heavier than Sulphur, of which the ores of
every other kind always contain a pretty large proportion. This ore is
moreover very hard, and is not brought to a fine powder with so much
ease as the rest.

These properties of Tin ore furnish us with the means of separating it
easily by lotion, not only from earthy and stony parts, but even from
the other ores which may be mixed with it. And this is of the greater
advantage on two accounts, _viz._ because Tin cannot endure, without
the destruction of a great part thereof, the degree of fire necessary
to scorify the refractory matters which accompany its ore; and again
because this metal unites so easily with Iron and Copper, the ores
of which are pretty commonly blended with Tin ore, that, after the
reduction, it would be found adulterated with a mixture of these two
metals, if they were not separated from it before the fusion.

But sometimes the Iron ore confounded with that of Tin is very heavy,
and is not easily pulverized; whence it comes to pass that it cannot be
separated therefrom by washing only. In that case the magnet must be
employed to separate it, after the ore hath been roasted.

Roasting is moreover necessary for Tin ore, in order to dissipate the
Arsenic which volatilizes, calcines, or destroys one part of the Tin,
and reduces the rest to a short, brittle substance, like a Semi-metal.
The ore is known to be sufficiently roasted when no more fumes rise
from it; when it has lost the smell of garlic; and when it does not
whiten a clean plate of Iron held over it.

Tin being one of those metals which are most easily calcined, it is
necessary in reducing its ore to employ such matters as may furnish it
with phlogiston. In order to defend it from the contact of the air,
which always accelerates the calcination of metallic substances, the
mixture is to be covered with Sea salt; and the addition of pitch helps
to increase the quantity of phlogiston.


PROCESS II.

_The Calcination of Tin._

Into an unglazed earthen dish put the quantity of Tin you intend to
calcine; melt it, and keep stirring it from time to time. Its surface
will be covered with a greyish white powder: continue the calcination
till all your Tin be converted into such a powder, which is the _Calx
of Tin_.


_OBSERVATIONS._

Though the calcination of metalline substances is promoted by exposing
them, in powder, or in filings, to the action of fire, and by ordering
it so that they may not melt, because they present a much smaller
surface when melted than when unmelted; yet we have not directed this
precaution to be used in calcining Tin. The reason is, this metal is so
fusible that it cannot endure the degree of fire requisite to destroy
its phlogiston without melting, and of course, though Tin calcines
easily, the operation is nevertheless tedious, because the melted metal
presents but a small surface to be acted on by the fire and the air.
This inconvenience may be partly remedied, and the operation greatly
expedited, by dividing the quantity of Tin to be calcined into several
small parcels, and exposing them to the fire in separate vessels, so
that they may not re-unite when melted, and form one single mass.

Leaf Tin cast on Nitre in actual fusion causes it to deflagrate and
fulminate; and from this mixture there rises a white vapour, which is
converted into flowers when it meets with any obstacle to impede its
flying off entirely.

Mr. Geoffroy, who went through a course of experiments on Tin, an
account whereof may be seen in the Memoirs of the Academy of Sciences,
found that from the colour of the calx of that metal a judgment may be
formed of its degree of purity, and nearly of the quantity and quality
of the metallic substances with which it is alloyed. The experiments
tried on this subject by that eminent Chymist are very curious.

He performed the calcination in a crucible, which he heated to a
cherry-red, and kept up the same degree of fire from the beginning to
the end of the operation. The calx which formed upon his metal, in that
degree of heat, appeared like small white scales, a little reddish on
the under side. He pushed it to one side as it formed, to the end that
it might not cover the surface of the metal, which, like all others,
requires the contact of the air to turn it into a calx.

"While he was making these calcinations, he had an opportunity of
observing a curious fact, of which no body before him had ever taken
notice; probably because no body had ever calcined Tin by the same
method. The fact is, that during the calcination of the Tin, whether
you break the pellicle which forms on the surface of the metal while
in red-hot fusion, or whether you let it remain without touching it,
you perceive in several places a small swell of a certain matter,
which bursts and makes its way through the pellicle. This matter puffs
up, grows red, at the same instant takes fire, and darts out a small
whitish flame, as vivid and as brilliant as that of Zinc, when urged
by a fire strong enough to sublime it into flowers. The vividness of
this flame may be further compared to that of several small grains of
phosphorus of urine fired and gently dropped on boiling water. From
this bright flame a white vapour exhales; after which the swelled mass
partly crumbles down, and turns to a light white powder, sometimes
spotted with red, according to the force of the fire. After this
momentary ignition, there arise stronger, more numerous, or more
frequent heavings of matter, out of which issues a good deal of white
fume, that may be intercepted by a cover of tin-plate or copper fitted
to the crucible, and appears to be the flowers of Tin, which in some
measure corrode these metals. Hence Mr. Geoffroy conjectures, with a
great deal of probability, that their sublimation is promoted by a
portion of Arsenic. When the crust formed by this calx comes to be too
thick, or in too great a quantity, to be pushed on one side, so as to
leave part of the metal uncovered, Mr. Geoffroy puts out the fire,
because no more calx would be formed: the communication of the external
air with the Tin in fusion being absolutely necessary thereto, as
hath been already said. In this operation it is to be observed that,
if the fire be too slow, neither the inflammation of the sulphureous
particles, nor the white fumes that rise, will be so distinctly
perceived, as when the fire is of the degree requisite to keep the
crucible just of a cherry-red heat.

"Mr. Geoffroy having taken off this first calx began the calcination
anew. In this second heat the buddings or heavings were more
considerable, and shot up in the form of cauli-flowers; but were still
composed of little scales. The thoroughly calcined portion of this
vegetation was likewise white and red; and the inferior surfaces of
some little bits thereof were wholly red. When these calcinations are
continued, sulphureous vapours rise seemingly of another kind than
those which appeared in the beginning; for all the calx made by the
first heat was perfectly white: whereas in the second it begins to be
spotted here and there with a tinge of black. Mr. Geoffroy was obliged
to go through a course of twelve several calcinations before he could
convert two ounces of Tin into a calx. He had the opportunity, during
these several calcinations, to observe that after the fourth, and
sometimes after the third, the red spots of the calx decrease, and the
black increase; that the germinations cease; that the crust of the calx
remains flat; that in the twelfth fire the Tin yields no more of this
scaly crust; that towards the end the undulations of the fused metal
appear no longer; and that the small remainder of calx is mixed with
several very minute grains of metal, which seem much harder than Tin.
Mr. Geoffroy could not collect a sufficient quantity thereof to cupel
them, and satisfy himself whether or no they were Silver."

Though Tin, and all the imperfect metals in general, seem converted
to a calx, and lose the metalline form, by one single calcination,
and that a slight one; yet they are not wholly deprived of their
phlogiston: for if the calx of Tin, for instance, prepared according
to the process above delivered, be cast upon Nitre in fusion, it will
make that salt deflagrate very perceptibly; a convincing proof that it
still contains much inflammable matter. If therefore a calx be required
absolutely free from phlogiston, this first calx must be recalcined
by a more violent fire, and the calcination continued till all the
phlogiston be dissipated.

"Mr. Geoffroy, being desirous of having his calx of Tin very pure and
perfectly calcined, exposed once more to the action of fire the twelve
portions of calx obtained by his former calcinations. But, as it would
have been too tedious to re-calcine them all separately, he made four
parcels of the whole, each consisting of three taken according to
the order in which they were first calcined; and gave to each a fire
sufficiently strong, and long enough continued, to calcine them as
thoroughly as was possible. After this second calcination he found
them all of a most beautiful white, except the first parcel: as that
consisted of the portions obtained by the three first heats, in all of
which there were scales tinged with red, it still retained a stain of
carnation, though hardly perceptible. Agreeably to the general rule,
the two ounces of Tin gained in weight by being thus calcined; and the
increase was two drams and fifty seven grains.

"Mr. Geoffroy observes, that no Tin, but what is absolutely pure, will
yield a perfectly white calx. He calcined in this manner several other
parcels of Tin that were impure and variously alloyed; each of which
produced a calx differently coloured, according to the nature and
quantity of its alloy: whence he justly concludes, that calcination
is a very good method of trying the fineness of Tin, or its degree of
purity." The particulars of Mr. Geoffroy's experiments on this subject,
which are very curious, may be seen in the Memoirs of the Academy for
1738.

It is proper to take notice that a man should be very cautious how he
exposes himself to the vapours of Tin, because they are dangerous; this
metal being very justly suspected by Chymists of containing something
Arsenical.


PROCESS III.

_The dissolution of Tin by Acids, The Smoking Liquor of_ Libavius.

Put into a glass vessel what quantity you please of fine Tin cut into
little bits. Pour on it thrice as much _aqua regis_, compounded of two
parts _aqua fortis_ weakened with an equal quantity of very pure water,
and one part Spirit of Salt. An ebullition will arise, and the Tin will
be very rapidly dissolved; especially if the quantities of metal and of
_aqua regis_ be considerable.


_OBSERVATIONS._

Tin is soluble by all the Acids; but _aqua regis_ dissolves it best
of any. Yet in this dissolution it comes to pass that part of the
dissolved Tin precipitates of its own accord to the bottom of the
vessel, in the form of a white powder. This solution of Tin is very fit
for preparing the purple-coloured precipitate of Gold. For this purpose
the solution of Tin must be let fall, drop by drop, into a solution of
Gold. Spirit of Nitre dissolves Tin nearly as _aqua regis_ does; but it
occasions a greater quantity of calx.

If two or three parts of Oil of Vitriol be poured on one part of Tin,
and if the vessel in which the mixture is made be exposed to such a
degree of heat as to evaporate all the moisture, there will remain
a tenacious matter sticking to the sides of the vessel. If water
be poured on this matter, and it be then exposed a second time to
the fire, it will dissolve entirely, excepting a small portion of
a glutinous substance, which also may be dissolved in fresh Oil of
Vitriol.

The Acid of Sea-salt may be combined with Tin by the following process.
Mix perfectly, by trituration in a marble mortar, an amalgam of two
ounces of fine Tin, and two ounces and a half of Quick-silver, with
as much Corrosive Sublimate. As soon as the mixture is completed, put
it into a glass retort, and distil with the same precautions as we
directed to be used in preparing concentrated and smoking Acids. There
will first come over into the receiver some drops of a limpid liquor,
which will be soon followed by an elastic spirit that will issue out
with impetuosity. At last some flowers, and a saline tenacious matter,
will rise into the neck of the retort. Then stop your distillation,
and pour into a glass bottle the liquor you will find in the receiver.
This liquor continually exhales a considerable quantity of dense, white
fumes, as long as it is allowed to have a free communication with the
air.

The product of this distillation is a combination of the Acid of
Sea-salt with Tin. As the affinity of Tin with this Acid is greater
than that of Mercury, the Acid contained in the Corrosive Sublimate
quits the Mercury, wherewith it was united, to join the Tin; which it
volatilizes so as to make it rise with itself in a limpid form. We make
use of the amalgam of Tin with Quick-silver, because we are thereby
enabled to mix the Corrosive Sublimate perfectly therewith, as the
success of the operation requires it should be.

In this experiment the Tin is volatilized, and the Acid of Sea-salt,
which is exceedingly concentrated, flies off incessantly in the form
of white vapours. This compound is known in Chymistry by the name of
_Smoking Liquor of Libavius_; a name derived from its quality, and from
its Inventor. Tin dissolved by Acids is easily separated from them by
Alkalis. It always precipitates in the form of a white calx.



CHAP. VI.

_Of_ LEAD.


PROCESS I.

_To extract Lead from its Ore._

Having roasted your Lead ore reduce it to a fine powder; mix it with
twice its weight of the black flux, and one fourth of its weight of
clean iron filings and borax; put the whole into a crucible capable of
containing at least thrice as much; over all put Sea-salt four fingers
thick; cover the crucible; lute the juncture; dry the whole with a
gentle heat, and set it in a melting furnace.

Make the crucible moderately red: you will hear the Sea-salt
decrepitate, and after the decrepitation a small hissing in the
crucible. Keep up the same degree of fire till that be over.

Then throw in as many coals as are necessary to complete the operation
entirely, and raise the fire suddenly, so as to bring the whole mixture
into perfect fusion. Keep up this degree of fire for a quarter of an
hour, which is time sufficient for the precipitation of the Regulus.

When the operation is finished, which may be known by the quietness of
the matter in the crucible, and by a bright vivid flame that will rise
from it, take the crucible out of the furnace, and separate the Regulus
from the scoria.


_OBSERVATIONS._

All Lead ore contains a good deal of Sulphur, which must be first
separated from it by roasting: and as this kind of ore is apt to fly
when first exposed to the fire, it is proper to keep it covered till it
be thoroughly heated. Another precaution to be used, in roasting this
ore, is not to give it too great a heat, but to keep the vessel which
contains it just moderately red; because it easily turns clammy, which
occasions it to stick to the vessel.

The Iron that is added, and mixed with the flux, absorbs the Sulphur
which may happen to remain, even after roasting: it helps also to
separate from the Lead some portions of semi-metal, especially of
Antimony, which are frequently mixed with this ore.

There is no fear least the Iron mix with the Lead in fusion, and
adulterate it: for these two metals are incapable of contracting any
union together, when each has its metalline form.

Nor is there any reason to apprehend lest the Iron should, by its
refractory quality, obstruct the fusion of the mixture; for though this
metal be not fusible when alone, yet, by the union it contracts with
the matters it is designed to absorb, it becomes so to such a degree as
in some measure to perform, on this occasion, the office of a flux.

The government of the fire is a point of great consequence in this
operation. It is necessary to apply but a moderate degree of heat
at first: for, when the metallic earth of the Lead, combining with
the phlogiston, acquires the metalline form, it swells up in such an
extraordinary manner, that there is great danger least the matter
should overflow, and run all out of the containing vessel. With a view
therefore to avoid this inconvenience, we direct a very large crucible
to be used. This heaving of the Lead, at the instant of its reduction,
is attended with a noise like the whistling of wind.

Notwithstanding all the precautions that can be used to prevent the
reduction from taking place too hastily, and so occasioning the
effusion of the matter, it often happens that, on raising the fire in
order to bring the mixture into fusion, the hissing suddenly begins
again, and is very loud. In that case all the apertures of the furnace
must immediately be shut close, in order to choak and suffocate the
fire: for, if this be neglected, the matter in the crucible will swell
up, make its way through the luting of the juncture, nay, push up the
cover, and run over. This accident is to be apprehended during the
first five or six minutes after you raise the fire in order to melt
the mixture. This effusion of the matter is accompanied with a dull
flame, a thick, grey and yellow smoke, and a noise like that of some
boiling liquor. When you observe these several phenomena you may be
sure the matter is run out of the crucible, either in the manner above
described, or by making its way through some cracks in the vessel, and
consequently that the operation is spoiled.

Moreover, this event infallibly follows whenever a bit of coal happens
to fall into the crucible; and this is one reason why it is necessary
to cover it.

You may be certain that the operation hath succeeded if the scoria be
smooth when cold, and have not in part escaped through the lute; if
the Lead be not dispersed in globules through the whole mass of the
matter contained in the crucible, but is, on the contrary, collected at
the bottom, in the form of a solid Regulus, not very shining, but of a
blueish cast, and ductile. Moreover, the scoria ought, in the present
case, to be hard and black, and should not appear full of holes like a
sieve, except only in that part which was contiguous to the Salt.

Here it is proper to observe, that the Sea-salt doth not mix with the
scoria, but floats upon it. After the operation it is black; which
colour it gets, no doubt, from the charred parts of the flux. The
absence of these signs shews the operation to have miscarried.

When the ore to be smelted is pyritose and refractory, it may be
roasted at first with a much stronger degree of fire than is used for
ores that are fusible; because the martial earth, and the unmetallic
earth, which are always mixed in pyritose matters, hinder it from
growing readily soft in the fire. Besides, such an ore requires a
greater quantity of the black flux and of borax to be mixed with it,
and a higher degree of fire to fuse it.

It is generally needless to mix iron filings with this sort of ore;
because the martial earth, with which pyritose matters are always
accompanied, is reduced during the operation by the help of the black
flux, which for that purpose is mixed with it in a large proportion,
and furnishes a quantity of iron sufficient to absorb the heterogeneous
minerals mixed with the Lead.

Yet, if it should be observed that the pyrites which accompany the Lead
ore are arsenical, then, as such pyrites contain but a small quantity
of ferruginous earth, iron filings must be added; which are, on this
occasion, so much the more necessary for absorbing the Arsenic, as
this mineral remains in part confounded with the ore, is reduced to
a Regulus during the operation, unites with the Lead, and destroys a
great deal of it by procuring its vitrification.

The Lead obtained from such pyritose ores is commonly not very pure; it
is blackish and scarce ductile; qualities communicated to it by a small
mixture of Copper in the pyrites, which always contain more or less
thereof. We shall presently shew the method of separating Lead from
Copper.

Lead ore may also be reduced by melting it amidst coals. For that
purpose first kindle a fire in the furnace in which you intend to melt
your ore; then put a layer of your ore immediately upon the lighted
coals, and cover it with another layer of coals.

Though the melting furnace used for this operation be capable of giving
a considerable heat, yet it is necessary further to increase the force
of the fire by the means of a good pair of perpetual bellows, which
will produce an effect like that of a forge. The ore melts, the earth
of the Lead unites with the phlogiston of the coals, and so is reduced
to metal, which runs through the coals, and falls into an earthen
vessel placed at the bottom of the furnace to receive it. Care must be
taken to keep this vessel well filled with charcoal-dust, to the end
that the Lead may be in no danger of calcination while it continues
there; the charcoal-dust constantly furnishing it with phlogiston to
preserve its metalline form.

The earthy and stony matters that accompany the ore are scorified by
this fusion, just as they are by the other which is performed in a
close vessel. With regard to the Sulphur and Arsenic, they are supposed
to have been first accurately separated from the ore by roasting. This
is the method commonly employed for smelting Lead ore at the works.


PROCESS II.

_To separate Lead from Copper._

With luting earth and charcoal-dust make a flat vessel, widening
upwards, and large enough to contain your metalline mass. Set it
shelving downwards from the back towards the fore-part; and in the
fore-part, at the bottom, make a little gutter communicating with
another vessel of the same nature, placed near the former and a little
lower. Let the mouth of the gutter within side the upper vessel be
narrowed, by means of a small iron plate fixed across it, while the
loam is yet soft; so as to leave a very small aperture, in the lower
part of this canal, sufficient to discharge the Lead as it melts. Dry
the whole by placing lighted coals around it.

When this apparatus is dry, put your mixed mass of Copper and Lead into
the upper vessel: both in that, and in the other vessel, light a very
gentle fire of wood or charcoal, so as not to exceed the degree of heat
necessary to melt Lead. In such a degree of heat the Lead contained
in the mixed mass will melt, and you will see it run out of the upper
vessel into the lower; at the bottom of which it will unite into a
Regulus. When in this degree of heat no more Lead flows, increase the
fire a little, so as to make the vessel moderately red.

When no more will run, collect the Lead contained in the lower vessel.
Melt it over again in an iron ladle, with a degree of fire sufficient
to make the ladle red; throw into it a little tallow or pitch, and
while it burns keep stirring the metal, in order to reduce any part of
it that may be calcined. Remove the pellicle or thin crust which will
form on the surface; squeeze out all the Lead it contains, and then put
it to the mass of Copper left in the upper vessel. Check the fire, and
in the same manner take off a second skin that will form on the surface
of the Lead. Lastly, when the metal is ready to fix, take off the skin
that will then appear on it. The Lead remaining after this will be very
pure, and free from all alloy of Copper.

With regard to the Copper itself, you will find it in the upper vessel
covered with a thin coat of Lead: and if the Lead mixed with it was in
the proportion of a fourth or a fifth part only, and the fire applied
was gentle and slow, it will retain nearly the same form after the
operation that the mixed mass had before.


_OBSERVATIONS._

Lead frequently remains mixed with Copper after the reduction of its
ore, especially if the ore was pyritose. Though Copper be a much more
beautiful and more ductile metal than Lead, yet the latter by being
alloyed with the former is rendered eager and brittle. This bad quality
is easily discovered by the eye on breaking it: for the surface of
the broken part appears all granulated; whereas when it is pure it is
more evenly, and resembles a congeries of solid angles. If the Lead
be alloyed with a considerable quantity of Copper, its colour hath a
yellowish cast.

Considering the bad qualities which Copper communicates to Lead, it
is necessary to separate these two metals from each other. The method
above laid down is the simplest and the best. It is founded on two
properties belonging to Lead: the first is that of being much more
fusible than Copper; so that it will melt and run in a degree of heat
that is not capable of making the Copper even red-hot, which yet is
very far from being able to melt it: the second is, that Lead, though
it hath an affinity with Copper, and unites very perfectly therewith,
yet is not able to dissolve it without a greater heat than the degree
barely necessary to fuse Lead. Hence it comes that Lead may be melted
in a Copper vessel, provided no greater degree of heat be applied than
that purpose requires. But when the Lead becomes so hot as to be red,
fume, and boil, it instantly begins to dissolve the Copper. For this
reason, it is essential to the success of our operation that a moderate
degree of heat only be applied, and no greater than is requisite to
keep the Lead in fusion.

Charcoal-dust is made an ingredient in the composition of the vessels
used on this occasion, in order to prevent the calcination of the Lead.

The iron plate, with which the entrance of the gutter within the upper
vessel is narrowed, serves to prevent the larger pieces of Copper,
which the Lead may carry along with it, from passing through: it stops
them, and allows the Lead to run off alone.

But as these parcels of Copper may entirely choak the passage, care
must be taken, when any happen to be stopt, to remove them from the
entrance of the gutter, and push them back into the middle of the
vessel. It is also necessary to observe whether or no the Lead fixes
any where in the passage; and, if it does, the heat of that part must
be increased, in order to melt it and make it run off.

Notwithstanding all the precautions that can be taken, to hinder the
melted Lead from carrying off any Copper with it, it is impossible to
prevent this inconvenience entirely; and therefore the Lead is melted
over again, in order to separate the small portion of Copper with which
it is still adulterated.

As Copper is much lighter than Lead, if these two metals happen to
be so blended together that the Copper, without being in fusion and
dissolved by the Lead, is only interposed between the parts of the
melted Lead, so as to swim therein, it is then precisely in the case of
a solid body plunged into a fluid heavier than itself, and must rise
to the surface, like wood thrown into water. It is proper to burn some
inflammable matter on this melted Lead, in order to reduce such parts
thereof as are constantly calcining on its surface while it is in
fusion; for without this precaution they would be taken off together
with the Copper.

The Copper remaining after this separation is, as we took notice
before, still mixed with a little Lead. If you desire to separate it
entirely therefrom, you must put it into a cupel, and expose it under
the muffle to such a degree of fire as may convert all the Lead into
litharge. This cannot be so done but that some of the Copper also
will be scorified by the heat of the fire, and by the action of the
Lead: but as there is a very great difference between the facility and
readiness with which these two metals calcine, the portion of Copper
that is calcined, while the whole Lead is turning into litharge, is
scarce worth considering.

The Lead, though carefully separated from the Copper by the process
here delivered, is not yet absolutely pure: sometimes it is alloyed
with Gold, and almost always contains some Silver. If you would free
the Lead as much as possible from any mixture of these two metals, you
must convert it into glass, separate the remaining bead, and afterwards
reduce this glass of Lead. But, as these two perfect metals are of no
prejudice to the Lead, it is not usual to separate them from it, unless
they be in a sufficient proportion to defray the charge, and produce
some profit besides.

When we examine by the cupel the just proportion of Gold and Silver
that an ore or a mixed metalline mass will yield, we make a previous
assay of the Lead to be employed in the operation, and afterwards, in
our estimate, deduct a proper allowance for the quantity of fine metal
due to the Lead made use of.


PROCESS III.

_The Calcination of Lead._

Take what quantity of Lead you please; melt it in one or more unglazed
earthen pans: a dark grey powder will be found on its surface. Keep
stirring the metal incessantly till it be wholly converted into such a
powder, which is the _Calx of Lead_.


_OBSERVATIONS._

As Lead is a very fusible metal, and in that respect greatly resembles
Tin, most of the observations we made on the calcination of Tin may be
applied here.

In the calcination of all metals, and particularly in this of Lead,
there appears a singular phenomenon which is not easily accounted for.
It is this: though these matters lose a great deal of their substance,
either by the dissipation of their phlogiston, or because some of the
metal, perhaps, exhales in vapours, yet when the calcination is over
their calces are found to be increased in weight, and this increase is
very considerable. An hundred pounds of Lead, for example, converted
into Minium, which is nothing but a calx of Lead brought to a red
colour by continuing the calcination, are found to gain ten pounds
weight; so that for an hundred pounds of Lead we have one hundred and
ten pounds of Minium: a prodigious and almost incredible augmentation,
if it be considered that, far from adding any thing to the Lead, we
have on the contrary dissipated part of it.

To account for this phenomenon Natural Philosophers and Chymists have
invented several ingenious hypotheses, but none of them entirely
satisfactory. As we have no established theory to proceed upon, we
shall not undertake to explain this extraordinary fact.


PROCESS IV.

_To prepare Glass of Lead._

Take two parts of Litharge, and one part of pure crystalline Sand;
mingle them together as exactly as possible, adding a little Nitre and
Sea-salt: put this mixture into a crucible of the most solid and most
compact earth. Shut the crucible with a cover that may perfectly close
it.

Set the crucible thus prepared in a melting furnace; fill the furnace
with coals; light the fire gradually, so that the whole may be slowly
heated: then raise the fire so as to make the crucible very red, and
bring the matter it contains into fusion; keep it thus melted for a
quarter of an hour.

Then take the crucible out of the furnace, and break it: in the bottom
thereof you will most commonly find a small button of Lead, and over
it a transparent Glass, of a yellow colour nearly resembling that of
amber. Separate this Glass from the little button of metal, and from
the saline matters which you will find above it.


_OBSERVATIONS._

Pure Lead, being exposed to a strong fire without any additament,
turns to Litharge; which is a scaly sort of substance, more or less
yellowish, shining, and soft to the touch. This is the first advance
to the Vitrification of Lead. The large refineries of Gold and Silver
by the means of Lead furnish a great quantity of this material. It is
sometimes whitish, and is then called _Litharge of Silver_; sometimes
yellow, and then bears the name of _Litharge of Gold_. The difference
of its colour depends on the degree of fire it hath undergone, and on
the metalline substances vitrified with it.

Litharge alone is very fusible, and being exposed to the fire is easily
converted into glass: but this Glass of Lead, made without additament,
is so active, so penetrating, and so apt to swell, that it can scarcely
be made use of when pure. We are obliged in some sort to clog it, by
uniting it with some vitrifiable matter that is not so subtile, such
as sand; and it is for this reason, not to render the mixture more
fusible, that we have directed the addition of one third part of Sand
to two thirds of Litharge.

The Nitre and Sea-salt, prescribed as ingredients in the mixture, are
designed to procure an equal fusion of the whole. For, as the sand is
lighter and less fusible than the Litharge, it will partly rise towards
the upper part of the crucible when that matter first begins to flow;
in consequence whereof the contents of the upper part will be much more
difficult to melt, and form a Glass much more compact than that below:
but the Nitre and Sea-salt possessing the upper part of the crucible,
because they are still lighter than the Sand, and being in their own
nature very efficacious fluxes, on account of their great fusibility,
they quickly bring about the fusion of those particles of sand, which,
having escaped the action of the Litharge, may have risen unvitrified
to its surface.

The most difficult thing to procure, and yet the most necessary to the
success of this operation, is a crucible of earth so firm and compact
as not to be penetrated by the Glass of Lead, which corrodes and makes
its way through every thing.

The precaution of chusing a crucible, that shall contain a good deal
more than the matter to be vitrified, is a necessary one, because
Litharge and Glass of Lead are very apt to swell.

The rule to keep the crucible close shut is also indispensably
necessary, to prevent any bit of charcoal, or other inflammable matter,
from falling into it: for when this happens it occasions a reduction of
the Lead, which is always attended with a sort of effervescence, and
such a considerable heaving, that commonly most of the mixture runs
over the crucible. For the same reason it is very proper, before you
expose the mixture to the fire, to examine whether or no it contains
any matter capable of furnishing a phlogiston during the operation; and
if it does, to remove that matter with great care.

The little button of Lead, found at the bottom of the crucible after
the operation, comes from a small portion of Lead that is commonly
left in Litharge, unless you prepare it carefully yourself, and do not
take it from the fire till you are sure of having destroyed all the
Lead. Besides, this small portion of Lead can be of no prejudice to the
operation, because it cannot communicate its phlogiston to the rest of
the matter.

The revivifying of Litharge, of the Calx, and of the Glass of Lead, may
be obtained by the same processes as the reduction of its ore.


PROCESS V.

_Lead dissolved by the Nitrous Acid._

Put into a matrass some _aqua fortis_ precipitated like that used to
dissolve Silver; weaken it by mixing therewith an equal quantity of
common water; set the matrass in a hot sand-bath; throw into it, little
by little, small bits of Lead, till you see that no more will dissolve.
_Aqua fortis_ thus lowered will dissolve about a fourth of its weight
of Lead.

There is gradually formed upon the Lead, as it dissolves, first a
grey powder, and afterwards a white crust, which at last hinder the
solvent from acting on the remaining part of the metal; and therefore
the liquor should be made to boil, and the vessel should be shaken to
remove those impediments, by which means all the Lead will be dissolved.


_OBSERVATIONS._

Lead very much resembles Silver, with respect to the phenomena which
attend its dissolution in Acids. For example, the Nitrous Acid must
be very pure and uncontaminated with the Vitriolic or Marine Acid, to
qualify it for keeping the Lead in solution: for, if it be mixed with
either the one or the other of these Acids, the Lead will precipitate
in the form of a white powder as fast as it dissolves; which is just
the case with Silver.

If the Vitriolic Acid be mixed with the Nitrous, the precipitate will
be a combination of the Vitriolic Acid with Lead; that is, a Neutral
Metallic Salt, or Vitriol of Lead. If the Acid of Sea-salt be mixed
therewith, the precipitate will be a _Plumbum corneum_; that is, a
Metallic Salt resembling the _Luna cornea_.

When all the Lead is dissolved as above described, the liquor appears
milky. If it be kept warm over the fire till little crystals begin to
appear on its surface, and afterwards left to stand quiet, in a certain
time there will be found at the bottom a greyish powder, which being
tried on Gold is Mercurial enough to whiten it. Little globules of
Quick-silver are even discernible in it.

We owe this observation, together with this manner of proving the
existence of Mercury in Lead, and of procuring it from thence, to M.
Grosse, who hath given an account of his process in the Memoirs of the
Academy of Sciences, from whence we have copied the description of the
operation in hand.

The solution being quickly poured off by inclination from the grey
mercurial precipitate is still milky, and deposites another white
sediment. When this second precipitate falls the liquor becomes clear
and limpid, and is then of a fine yellow colour, like a solution of
Gold. On this gold-coloured solution, and on the two precipitates
above-mentioned, M. Grosse made several observations, the chief of
which we shall here insert.

The yellow liquor affects the tongue at first with a taste of
sweetness; but afterwards vellicates it very smartly, and leaves on it
a strong sensation of acrimony, which continues for a long time.

Alkalis precipitate the Lead suspended in this liquor, just as they do
all other metals dissolved by Acids; and this precipitate of Lead is
white.

Sea-salt, or Spirit of Salt, separates the Lead from its solvent, and
precipitates it, as we observed before, into a _Plumbum corneum_: but
this precipitate differs from the _Luna cornea_, as being very soluble
in water; whereas the _Luna cornea_ will not dissolve in it at all;
or at least dissolves therein with great difficulty, and in a very
small quantity. This _Plumbum corneum_ dissolved in water is again
precipitated by the Vitriolic Acid. M. Grosse observes, that this
forms an exception to the eighth column of Mr. Geoffroy's Table of
Affinities; in which the Acid of Sea-salt is marked as having a greater
affinity than any other Acid with Metallic substances.

Our solution of Lead is also precipitated in a white powder by several
Neutral Salts; such as Vitriolated Tartar, Alum, and common Vitriol. It
is by the means of double affinities that these Neutral Salts effect
this precipitation.

Even pure water alone is capable of precipitating the Lead of our
solution, by weakening the Acid, and thereby disabling it from keeping
the metal suspended.

Lastly, as all the solutions of metals in Acids are nothing but
Neutral Metallic Salts in a fluid form, so if the solution of Lead be
evaporated over the fire, it will shoot into very beautiful crystals,
about the bigness of hemp-seed, shaped like regular pyramids having
square bases. These crystals are yellowish, and have a sweet saccharine
taste: but what is most singular in them is, that, as they consist of
the Nitrous Acid combined with Lead, which manifestly contains a great
deal of phlogiston, they constitute a Nitrous Metallic Salt, which has
the property of deflagrating in a crucible, without the addition of any
other inflammable matter. It is extremely hard to dissolve this Salt in
water.

The grey mercurial precipitate which whitens Gold, and in which little
globules of running Mercury are perceivable, is far from being pure
Mercury. This metallic substance makes but a small part thereof: for
it is an assemblage, 1. of little crystals of the same nature with
those afforded by the evaporated solution; 2. of a portion of the white
matter, or powder, which renders the solution milky; 3. of a grey
powder, which M. Grosse considers as the only mercurial part; 4. and
lastly, of little particles of Lead that have escaped the action of the
solvent; especially if a little more Lead than the Acid is capable of
dissolving were added with a view to saturate it entirely, as in the
present process.

By means of motion and heat the small parcels of Mercury may be
amalgamated with the Lead.

That Mercury should be found entire and in globules in the Spirit of
Nitre, which very easily dissolves that metallic substance, will not
be surprizing to those who reflect that, in the present case, the
Acid is saturated with Lead, with which it has a greater affinity
than with Mercury; as appears by M. Geoffroy's Table of Affinities,
where, in the column that hath the Nitrous Acid at top, Lead is placed
above Mercury. Agreeably to this, if Lead be presented to a solution
of Mercury in Spirit of Nitre, the Lead will be dissolved, and as the
dissolution thereof advances the Mercury will precipitate.

Hence it appears that, in order to find any Mercury in the spontaneous
precipitate of Lead dissolved by the Nitrous Acid, it is necessary that
the Acid be entirely saturated with Lead; or else that portion of the
Acid which remains unsaturated will dissolve the Mercury.

With regard to the white powder that renders the solution milky, and
afterwards precipitates, it is nothing but a portion of the Lead,
which, not being intimately united with the Acid, falls in part of its
own accord. It is a sort of calx of Lead, which being exposed to the
fire becomes partly glass, and partly Lead, because it still retains
some of its phlogiston.



CHAP. VII.

_Of_ MERCURY.


PROCESS I.

_To extract Mercury from its Ore, or to revivify it from Cinabar._

Pulverize the Cinabar from which you would extract the Mercury; with
this powder mix an equal part of clean iron filings; put the mixture
into a retort of glass or iron, leaving at least one third part thereof
empty. Set the retort thus prepared in a sand-bath, so that its body
may be quite buried in the sand, and its neck decline considerably
downwards: fit on a receiver half filled with water, and let the nose
of the retort enter about half an inch into the water.

Heat the vessels so as to make the retort moderately red. The Mercury
will rise in vapours, which will condense into little drops, and fall
into the water in the receiver. When you see that nothing more comes
over with this degree of heat, increase it, in order to raise what
Mercury may still be left. When all the Mercury is thus brought over,
take off the receiver, pour out the water contained in it, and collect
the Mercury.


_OBSERVATIONS._

Mercury is never mineralized in the bowels of the earth by any thing
but Sulphur; with which it forms a compound of a brownish red colour,
known by the name of _Cinabar_.

Sometimes it is only mixed with earthy and stony matters that contain
no Sulphur; but, as this metallic substance is never destitute of its
phlogiston, it then has its metalline form and properties. When it is
found in this condition, nothing is more easy than to separate it from
those heterogeneous matters. For that purpose no more is requisite than
to distil the whole with a fire strong enough to raise the Mercury in
vapours. This mineral is volatile; the earthy and stony matters are
fixed; and a certain degree of heat will effect a complete separation
of what is volatile from what is fixed.

This is not the case when Mercury is combined with Sulphur: for this
latter mineral is volatile as well as Mercury; and the compound
resulting from the union of them both is also volatile: so that if
Cinabar were exposed to the fire in close vessels, as it must be to
save the Mercury, it would be sublimed in substance, without being
decomposed at all.

In order therefore to separate these two substances from each other,
we must have recourse to the interposition of some third, which hath a
greater affinity with one of them than the other hath, and no affinity
with that other.

Iron hath all the conditions requisite for this purpose; seeing it
hath, as may be seen in the Table, a much greater affinity with Sulphur
than Mercury hath, and is incapable of contracting any union with
Mercury.

Iron, however, is not the only substance that may be employed on this
occasion: Fixed Alkalis, Absorbent earths, Copper, Lead, Silver,
Regulus of Antimony, have all, as well as Iron, a greater affinity
than Mercury with Sulphur. Nay, several of these substances, namely,
the saline and earthy Alkalis, as well as Regulus of Antimony, cannot
contract any union with Mercury: the rest, to wit, Copper, Lead, and
Silver, are indeed capable of amalgamating with Mercury; but then the
union which these metals contract with the Sulphur prevents it; and
even though they should unite with this metallic substance, the degree
of heat to which the whole mixture is exposed would soon carry up the
Mercury, and separate it with ease from those fixed substances.

In this distillation the same cautions must be observed as in all
others: that is, the vessels must be slowly heated, especially if a
glass retort be used; the fire must be raised by degrees, and a much
stronger one applied at last than at first. This operation particularly
requires a very strong degree of fire, when there is but a small
quantity of Mercury left.

After the operation there remains in the retort a compound of Iron and
Sulphur, which may easily be converted into a _crocus_, by calcining it
and burning away the Sulphur.

If a Fixed Alkali be employed, a Liver of Sulphur will be found in the
retort after the distillation.

If the Cinabar from which you extract the Mercury be good, you will
generally obtain seven eighths of its weight in Quick-silver.

In the present operation it is not necessary to lute on the receiver,
because the water, in which the nose of the retort is plunged, is
sufficient to fix the Mercurial vapours. In case the Cinabar, from
which you intend to separate the Mercury, be mixed with a great
quantity of heterogeneous, but fixed, matters, such as earths, stones,
&c. it may be separated from them by subliming it with a proper degree
of heat, because it is volatile.

The vapours of Mercury are prejudicial, and may excite a salivation,
tremors, and palsies; they should therefore be always avoided by such
as work on this mineral.

The oldest and richest mine of Mercury is that of Almaden in Spain.
It is a singular property of that mine that, though the Mercury found
in it is combined with Sulphur, and in the form of Cinabar, yet no
additament is required to procure the separation of these two; the
earthy and stony matter, with which the particles of the ore are
incorporated, being itself an excellent absorbent of Sulphur.

In the Quick-silver works carried on at this mine they make no use
of retorts. They place lumps of the ore on an iron grate, which
stands immediately over the furnace. The furnaces which serve for
this operation are closed at the top by a sort of dome, behind which
stands the shaft of a chimney that communicates with the fire-place,
and gives vent to the smoke. These furnaces have in their fore-side
sixteen apertures, to each of which is luted an aludel in a horizontal
position, communicating with a long row of other aludels placed
likewise in an horizontal direction; which aludels so connected
together form one long pipe or canal, the further end whereof opens
into a chamber destined to receive and condense all the mercurial
vapours. These rows of aludels are supported from end to end by a
terrass, which runs from the body of the building, wherein the furnaces
are erected, to that where the chambers are built that perform the
office of receivers.

This is a very ingenious contrivance and saves much labour, expence,
and trouble, that would be unavoidable if retorts were employed.

That part of the furnace which contains the lumps of ore, serves for
the body of the retort; the row of aludels for its neck; and the little
chambers in which these canals terminate are actual receivers. The
terrass of communication, which reaches from the one building to the
other, is formed of two inclined planes, the lower edges of which,
meeting in the middle of the terrass, rise from thence insensibly; the
one quite to the building where the furnaces are, and the other to that
which forms the recipient chambers. By this means, when any Mercury
escapes through the joints of the aludels, it naturally runs down
along these inclined planes, and so is collected in the middle of the
terrass, where the inferior sides of the planes meeting together form a
sort of canal, out of which it is easily taken up.

The celebrated M. de Jussieu having viewed the whole himself, in a
journey he made to this mine, furnished us with this description of the
work.


PROCESS II.

_To give Mercury, by the action of Fire, the appearance of a Metalline
Calx._

Put Mercury into several little glass matrasses with long and narrow
necks. Stop the matrasses with a little paper, to prevent any dirt from
falling into them. Set them all in one sand-bath, so that they may
be surrounded with sand as high as two thirds of their length. Apply
the strongest degree of heat that Mercury can bear without subliming:
continue this heat without interruption, till all the Mercury be turned
to a red powder. The operation lasts about three months.


_OBSERVATIONS._

Mercury treated according to the process here delivered hath all
the appearance of a metalline calx, but it hath no more: for, if it
be exposed to a pretty strong degree of fire, it sublimes, and is
wholly reduced to running Mercury, without the addition of any other
inflammable matter; which proves that during this long calcination it
lost none of its phlogiston.

The volatile nature of Mercury, which permits it not to bear a heat
of any strength without subliming, prevents our examining all the
effects that fire is capable of producing on it. Yet there is reason
to believe that, as this metallic substance resembles the perfect
metals in its weight, its splendour, and a brilliancy which resists all
the impressions of the air without alteration, it would like them be
unchangeable by the greatest force of fire, if it were fixed enough to
bear it.

In order to give Mercury the form of a metalline calx, it must
necessarily be exposed for about three months together, to the utmost
heat it can bear without subliming, as is above directed. Boerhaave
kept it digesting in a less heat for fifteen years successively, both
in open and in close vessels, without observing it to suffer the least
change; except that there was formed upon its surface a small quantity
of a black powder, which was reduced to running Mercury by trituration
alone.

Mercury thus converted to a red powder is known in chymistry and
medicine by the name of _Mercury precipitated per se_: a title proper
enough, as it is actually reduced to the form of a precipitate, and
that without any additament; but very improper on the other hand,
considering, that in reality this Mercury is not a precipitate, as not
having been separated from any menstruum in which it was dissolved.


PROCESS III.

_To dissolve Mercury in the Vitriolic Acid. Turbith Mineral._

Put Mercury into a glass retort, and pour on it thrice its weight of
good Oil of Vitriol. Set the retort in a sand-bath; fit on a recipient;
warm the bath by degrees till the liquor just simmer. With this heat
the Mercury will begin to dissolve. Continue the fire in this degree
till all the Mercury be dissolved.


_OBSERVATIONS._

The Vitriolic Acid dissolves Mercury pretty well: but for this purpose
the Acid must be very hot, or even boil; and then too it is a very
long time before the dissolution is completed. We have directed the
operation to be performed in a retort; because this solution is usually
employed to make another preparation called _Turbith Mineral_, which
requires that as much as possible of the Acid solvent be abstracted by
distillation. Having therefore dissolved your Mercury in the Vitriolic
Acid, if you will now prepare the Turbith, you must, by continuing
to heat the retort, drive over all the liquor into the receiver, and
distil till nothing remains but a white powdery matter: then break
the retort; pulverize its contents in a glass mortar, and thereon
pour common water, which will immediately turn the white matter of a
lemon-colour; wash this yellow matter in five or six warm waters, and
it will be what is called in medicine _Turbith Mineral_; that is, a
combination of the Vitriolic Acid with Mercury, five or six grains
whereof is a violent purgative, and also an emetic; qualities which
it possesses in common with the Vegetable Turbith, whose name it hath
therefore taken.

There rises out of the retort, both while the Mercury is dissolving,
and while the solvent is abstracting, a weak Spirit of Vitriol; because
a great part of the Acid remains united with the Quick-silver, which
at last appears in the form of a white powder: so that, if you do not
incline to save the Acid which rises on this occasion, you may, instead
of drawing off the liquor in a retort, evaporate it in a glass bason
set on a sand-bath, which will be much sooner done.

It is very remarkable that, on this occasion, the Mercury may be
exposed, without any danger of subliming, to a much greater heat than
it is capable of bearing when not combined with the Vitriolic Acid;
which shews that this Acid hath the property of fixing Mercury to a
certain degree.

The white matter, that remains after the evaporation of the fluid, is
one of the most violent corrosives, and would prove an actual poison if
taken internally. By washing it several times in warm water it is freed
from a great deal of its Acid, and so considerably sweetened. The proof
is this; if the water used in washing the Turbith be evaporated, there
remains after the evaporation a matter in form of a Salt, that being
set in a cellar runs into a liquor called _Oil of Mercury_, which is a
powerful corrosive. Several authors further direct Spirit of Wine to be
burnt on the Turbith, to sweeten it still more.

If, instead of washing the white matter that remains after the moisture
is drawn off, fresh Oil of Vitriol be poured on it, and then abstracted
as before; this treatment being repeated two or three times, there
will at last remain in the retort a matter having the appearance of an
oil, which resists the action of the fire, and cannot be desiccated:
qualities which are owing to the great quantity of Acid particles thus
united with the Mercury. This Oil of Mercury is one of the most violent
corrosives. The Mercury may be separated therefrom, by precipitating it
with an Alkali, or a metallic substance that hath more affinity than
Mercury with the Vitriolic Acid: Iron, for instance, may be employed in
this precipitation. Mercury thus separated from the Vitriolic Acid need
only be distilled to recover the form of Quick-silver.


PROCESS IV.

_To combine Mercury with Sulphur. Æthiops Mineral._

Mix a dram of Sulphur with three drams of Quick-silver, by triturating
the whole in a glass mortar with a glass pestle. By degrees, as you
triturate, the Mercury will disappear, and the matter will acquire a
black colour. Continue the triture till you cannot perceive the least
particle of running Mercury. The black matter you will then have in
the mortar is known in medicine by the name of _Æthiops Mineral_. An
Æthiops may also be made by fire in the following manner.

In a shallow unglazed earthen pan melt one part of flowers of Sulphur:
add three parts of running Mercury, making it fall into the pan in
the form of small rain, by squeezing it through chamoy leather. Keep
stirring the mixture with the shank of a tobacco-pipe all the while the
Mercury is falling: you will see the matter grow thick and acquire a
black colour. When the whole is thoroughly mixed, set fire to it with a
match, and let as much of the Sulphur burn away as will flame.


_OBSERVATIONS._

Mercury and Sulphur unite together with great ease; cold triture alone
is sufficient to join them. By this means the Mercury is reduced into
exceeding small atoms, and combines so perfectly with the Sulphur that
the least vestige thereof is not to be seen.

Sulphur is not the only matter which being rubbed with Mercury will
destroy its form and fluidity: all fat substances that have any degree
of consistence, such as the fat of animals, balsams, and resins, are
capable of producing the same effect. This metallic substance, being
triturated for some time in a mortar with these matters, becomes at
last invisible, and communicates to them a black colour. When thus
divided by the interposition of heterogeneous particles, it is said to
be _Killed_. But Mercury doth not contract such an intimate union with
these other matters as it doth with Sulphur.

The Æthiops prepared by fusion is a more perfect and accurate
combination of Mercury and Sulphur than the other: for, the quantity
of Sulphur directed to be used in making it being much greater than
is absolutely necessary to fix the Mercury, the redundant Sulphur is
destroyed by burning, and none left but what is most intimately united
with the Mercury; and hindered by the union it hath contracted with
that metallic substance from being so easily consumed. The Æthiops
therefore, which is prepared by fusion and burning the Sulphur,
contains a much greater proportion of Mercury than that which is made
by simple triture; so that in Medicine it ought to be prescribed in
different cases, and in smaller doses.

If no more Sulphur than is just necessary to kill the Mercury be added
to it at first, it will be difficult to obtain a perfect mixture;
because that quantity is very small: it is better, therefore, to employ
at once the quantity above directed.


PROCESS V.

_To sublime the Combination of Mercury and Sulphur into Cinabar._

Grind to powder Æthiops mineral prepared by fire. Put it into a
cucurbit; fit thereto a head; place it in a sand-bath, and begin with
applying such a degree of heat as is requisite to sublime Sulphur. A
black matter will rise, and adhere to the sides of the vessel. When
nothing more will rise with this degree of heat, raise the fire so
as to make the sand and the bottom of the cucurbit red; and then the
remaining matter will sublime in the form of a brownish red mass, which
is true _Cinabar_.


_OBSERVATIONS._

Æthiops Mineral requires nothing but sublimation to become true
Cinabar, like that found in Quick-silver mines: but our Æthiops
contains still more Sulphur than ought to be in the composition of
Cinabar; for which reason we have directed the degree of fire applied
at first to be no greater than that which is capable of subliming
Sulphur. As Cinabar, though consisting of Mercury and Sulphur, is
yet much less volatile than either of these substances alone; which
probably arises from the Vitriolic Acid contained in the Sulphur;
therefore, if there be any redundant Sulphur in the Æthiops, which hath
not contracted an intimate union with the Mercury, it will sublime by
itself in this first degree of heat. Some mercurial particles also will
rise with it, and give it a black colour.

Cinabar contains no more Sulphur than about a sixth or seventh part of
its weight: so that, instead of employing the common Æthiops to make
it, it would be better to prepare one on purpose that should contain
much less Sulphur; because too much Sulphur prevents the success of the
operation by blackening the Sublimate. Indeed in whatever manner you
go about it, the Cinabar always appears black at first: but when it is
well prepared, and contains no more than its due proportion of Sulphur,
the blackness is only external. This black coat therefore may be taken
off; and then the internal part will appear of a fine red, and, if
sublimed a second time, will be very beautiful.

As artificial Cinabar hath the same properties with the native, it may
be decomposed by the same means: so that, if you want to extract the
Mercury out of it, recourse must be had to the process above delivered
for working on Cinabar ores.


PROCESS VI.

_To dissolve Mercury in the Nitrous Acid. Sundry Mercurial
Precipitates._

Put into a matrass the quantity of Mercury you intend to dissolve: pour
on it an equal quantity of good Spirit of Nitre, and set the matrass
in a sand-bath moderately heated. The Mercury will dissolve with the
phenomena that usually attend the dissolutions of metals in this Acid.
When the dissolution is completed let the liquor cool. You will know
that the Acid is perfectly saturated, if there remain at the bottom of
the vessel, notwithstanding the heat, a little globule of Mercury that
will not dissolve.


_OBSERVATIONS._

Mercury dissolves in the Nitrous Acid with much more facility, and
in much greater quantity, than in the Vitriolic; so that it is not
necessary, on this occasion, to make the liquor boil. This solution
when cold yields crystals, which are a Nitrous Mercurial Salt. If you
desire to have a clear limpid solution of Mercury, you must employ an
_aqua fortis_ that is not tainted with the Vitriolic or Marine Acid:
for, the affinity of these two Acids with Mercury being greater than
that of the Nitrous Acid, they precipitate it in the form of a white
powder, when they are mixed with the solvent.

Mercury thus precipitated in a white powder, out of a solution
thereof in the Spirit of Nitre, is used in Medicine. To obtain this
precipitate, which is known by the name of the _White Precipitate_,
Sea-salt dissolved in water together with a little Sal Ammoniac is
used; and the precipitate is washed several times in pure water,
without which precaution it would be corrosive, on account of the great
quantity of the Marine Acid which it would contain.

The preparation known by the name of _Red Precipitate_ is also obtained
from our solution of Mercury in Spirit of Nitre. It is made by
abstracting all the moisture of the solution, either by distillation in
a retort, or by evaporation in a glass bason set on a sand-bath. When
it begins to grow dry it appears like a white ponderous mass. Then the
fire is made strong enough to drive off almost all the Nitrous Acid,
which, being now concentrated, rises in the form of red vapours. If
these vapours be catched in a receiver, they condense into a liquor,
which is a very strong and vastly smoking Spirit of Nitre.

By degrees, as the Nitrous Acid is forced up by the fire, the mercurial
mass loses its white colour, and becomes first yellow, and at last
very red. When it is become entirely of this last colour the operation
is finished. The red mass remaining is a Mercury that contains but
very little Acid, in comparison of what it did while it was white:
and indeed the first white mass is such a violent corrosive, that it
cannot be used in Medicine; whereas, when it is become red, it makes an
excellent escharotic, which those who know how to use it properly apply
with very great success, particularly to venereal ulcers.

This preparation is very improperly called a _Precipitate_: for the
Mercury is not separated from the Spirit of Nitre by the interposition
of any other substance, but only by evaporating the Acid. It is also
called _Arcanum Corallinum_.

It must be observed that Mercury, by its union with the Nitrous Acid,
acquires a certain degree of fixity: for the red precipitate is capable
of sustaining, without being volatilized, a stronger degree of heat
than pure Mercury can; which, as we observed before, is the property of
Turbith Mineral also.


PROCESS VII.

_To combine Mercury with the Acid of Sea-salt. Corrosive Sublimate._

Evaporate a solution of Mercury in the Nitrous Acid till there remain
only a white powder, as mentioned in our observations on the preceding
process. With this powder mix as much Green Vitriol calcined to
whiteness, and as much decrepitated Sea-salt, as there was Mercury in
the solution. Triturate the whole carefully in a glass mortar. Put
this mixture into a matrass, so that two thirds thereof may remain
empty, having first cut off the neck to half its length: or instead
thereof you may use an apothecary's phial. Set your vessel in a
sand-bath, and put sand round it as high as the contents can reach.
Apply a moderate fire at first, and raise it by slow degrees. Vapours
will begin to ascend. Continue the fire in the same degree till they
cease. Then stop the mouth of the vessel with paper, and increase the
fire till the bottom of the sand-bath be red-hot. With this degree of
heat a Sublimate will rise, and adhere to the inside and upper part
of the vessel, in the form of white, semi-transparent crystals. Keep
up the fire to the same degree till nothing more will sublime. Then
let the vessel cool; break it, and take out what is sublimed, which is
_Corrosive Sublimate_.


_OBSERVATIONS._

In this operation the mineral Acids act, and are acted upon, in a
remarkable manner. Every one of the three is at first neutralized,
or united with a different basis; the Vitriolic being combined with
Iron; the Nitrous with Mercury, forming therewith a Nitrous Mercurial
Salt; and the Marine with its natural Alkaline basis. The Vitriolic
and Nitrous Acids, which are united with metalline substances, being
both stronger than the Acid of Sea-salt, strive to expel it from its
basis, in order to combine with it themselves; but the Vitriolic Acid,
being the strongest of the two, would take sole possession of this
basis exclusive of the Nitrous, which would continue united with the
Mercury, if the Marine Acid had not a greater affinity than the Nitrous
with this metallic substance. This Acid therefore being expelled from
its basis by the Vitriolic Acid, and so set at liberty, must unite with
the Mercury, and separate the Nitrous Acid from it; which now hath no
resource but to unite with the Iron deserted by the Vitriolic Acid. But
as all these changes are brought about by the means of a considerable
heat, and as the Nitrous Acid hath not a very firm connection with the
Iron, it is driven off by the force of the fire; and this it is which
we see rise in vapours during the operation. It also carries off with
it some parts of the other two Acids, but in a very small quantity.
After the operation therefore there remains, 1. A combination of the
Vitriolic Acid with the basis of Sea-salt; that is, a Glauber's Salt:
2. A red martial earth, being that which was the basis of the Vitriol:
these two substances are blended together, and remain at the bottom of
the vessel because of their fixity: 3. A combination of the Marine
Acid with Mercury; both of which being volatile, they ascend together
into the upper part of the vessel, and there form a Corrosive Sublimate.

If we reflect on this process with attention, and recollect distinctly
the affinities of the different substances employed in it, we shall
perceive that it is not necessary to make use of all those matters, and
that the operation would succeed though several of them were left out.

First, the Nitrous Acid may be omitted; since, as hath been shewn, it
is not an ingredient in the Sublimate, but is dissipated in vapours
during the operation. From an accurate mixture therefore of Vitriol,
Sea-salt, and Mercury, a Corrosive Sublimate must be obtained: for
as the Acid of the Vitriol will disengage the Acid of Sea-salt, the
latter will be at liberty to combine with the Mercury, and so form the
compound we are in quest of.

Secondly, if we make use of Mercury dissolved by the Nitrous Acid,
we may omit the Vitriol; because the Nitrous Acid having a greater
affinity than the Marine Acid itself with the basis of Sea-salt, and
the Acid of Sea-salt having a greater affinity than the Nitrous Acid
with Mercury, these two Acids will naturally make an exchange of the
bases with which they are united: the Nitrous will lay hold on the
basis of Sea-salt, and form a quadrangular Nitre, while the Marine Acid
will join the Mercury, and with it form a Corrosive Sublimate.

Thirdly, instead of Sea-salt its Acid only may be employed; which being
mixed with the solution of Mercury in the Spirit of Nitre, will, by
virtue of its greater affinity with that metallic substance, separate
it from the Nitrous Acid, unite with it, and form a white mercurial
precipitate, which need only be sublimed to become the combination
required.

Fourthly, instead of Mercury dissolved in the Nitrous Acid, Mercury
dissolved by the Vitriolic Acid, or Turbith, may be used; only mixing
Sea-salt therewith: for these two saline substances will mutually
decompound each other, by virtue of the affinities of their Acids,
and for the same reasons that Sea-salt and the Mercurial Nitrous Salt
decompound each other. The Vitriolic Acid quits the Mercury with which
it is combined, to unite with the basis of the Sea-salt; and the
Acid of this Salt being expelled by the Vitriolic, combines with the
Mercury, and consequently forms our Corrosive Sublimate. In this case a
Glauber's Salt remains after the sublimation.

These several methods of preparing Corrosive Sublimate are never used,
because each of them is attended with some inconvenience; such as
requiring too long triture, yielding a Sublimate less corrosive than it
should be, or a smaller quantity of it. We must, however, except the
last; which was invented by the late Mr. Boulduc, of the Academy of
Sciences, who found none of these inconveniencies attending it[9].

  [9] See the Memoirs of the Academy for 1730.

Corrosive Sublimate may also be made only by mixing Mercury with
Sea-salt, without any additament. This may appear surprizing when we
consider that, as Acids have a greater affinity with Alkalis than with
metallic substances, the Acid of Sea-salt ought not to quit its basis,
which is Alkaline, to unite with Mercury.

In order to explain this phenomenon it must be remembered that
Sea-salt, when exposed to the fire without additament, suffers a little
of its Acid to escape. Now this portion of the Marine Acid unites with
the Mercury, and forms a Corrosive Sublimate. Moreover, as there is a
pretty strong affinity between the Marine Acid and Mercury, this may
help to detach from the Sea-salt a greater quantity of Acid than it
would otherwise part with. Nevertheless, the quantity of Sublimate
obtained by this means is not considerable, nor is it very corrosive.

On this occasion we must also mention another combination of the Marine
Acid with Mercury; which is made by mixing that metallic substance
perfectly with Sal Ammoniac, by the means of triture. Mercury, like all
other metals except Gold, possesses the property of decompounding Sal
Ammoniac, separating the volatile Alkali which serves it for a basis,
and combining, by the help of a very gentle heat, with its Acid, which
is well known to be the same with that of Sea-salt. This decomposition
of Sal Ammoniac, by the metalline substances, is a full exception
to the first column of Mr. Geoffroy's Table of Affinities, and is
the basis of several new Medicines invented by the late Comte de la
Garaye[10].

  [10] See the Memoir given in by me on this subject to the Academy of
  Sciences in the _Memoires l'Acadamie_ 1754.

Corrosive Sublimate is the most violent and the most active of all
corrosive poisons. It is never used in Medicine, but in external
applications. It is a powerful escharotic; it destroys proud flesh,
and cleans old ulcers: but it must be used by those only who know how
to apply it properly, and requires an able hand to manage it. It is not
commonly applied by itself, but mixed in the proportion of half a dram
to a pound of lime-water. This mixture is yellowish, and bears the name
of _Aqua Phagadenica_.

Water dissolves Corrosive Sublimate, but in a small quantity. If a
Fixed Alkali be mixed with this solution, the Mercury precipitates in
the form of a red powder. If the precipitate be procured by a Volatile
Alkali, it is white; if by Lime-water, it is yellow. This Mercurial
Salt dissolves pretty easily in boiling Spirit of Wine.


PROCESS VIII.

_Sweet Sublimate._

Take four parts of Corrosive Sublimate; pulverize it in a glass
or marble mortar; add by little and little three parts of Mercury
revivified from Cinabar; triturate the whole carefully, till the
Mercury be perfectly killed, so that no globule thereof can be
perceived. The matter will then be grey. Put this powder into an
apothecary's phial, or into a matrass, whose neck is not above four or
five inches long, leaving two thirds thereof empty. Set the vessel in
a sand-bath, and put sand round it to one third of its heighth. Apply
a moderate fire at first; and afterwards raise it gradually till you
perceive that the mixture sublimes. Keep it up to this degree till
nothing more will rise, and then break the vessel. Reject, as useless,
a small quantity of earth which you will find at the bottom; separate
also what adheres to the neck of the vessel, and carefully collect the
matter in the middle, which will be white. Pulverize it; sublime it
a second time, in the same manner as before; and in the same manner
separate the earthy matter left at the bottom of the vessel, and what
you find sublimed into the neck. Pulverize, and sublime a third time,
the white matter you last found in the middle. The white matter of this
third sublimation is the _Sweet Sublimate_, called also _Aquila Alba_.


_OBSERVATIONS._

The Acid of Sea-salt in the Corrosive Sublimate is very far from being
perfectly saturated with Mercury; and thence comes the corrosive
quality of this saline compound. But though Mercury, as appears by this
combination, is capable of imbibing a much greater quantity of Acid
than is necessary to dissolve it; nay, though it naturally takes up
this super-abundant quantity of Acid, yet it doth not follow from thence
that this redundant Acid may not combine with Mercury to the point of
perfect saturation, so as to lose its corrosive acidity.

This is the case in the operation here described. A fresh quantity
of running Mercury is mixed with Corrosive Sublimate; and the fresh
Mercury, combining with the super-abounding Acid, deprives the
Sublimate of its acrimony, and forms a compound which comes much nearer
the nature of a Neutral Metallic Salt.

Trituration alone is not sufficient to produce an union between the
newly added Mercury and the Acid of the Corrosive Sublimate: because,
generally speaking, the Acid of Sea-salt cannot dissolve Mercury
without the help of a certain degree of heat, and unless it be reduced
into vapours.

Thus, though the newly added Mercury becomes invisible by trituration,
and seems actually combined with the Corrosive Sublimate, yet the
union is not intimate. There is only an interposition of parts, but
no true dissolution of the newly added Mercury by the super-abundant
Acid of the Corrosive Sublimate. For this reason the mixture must be
sublimed; and by this sublimation only is the true union effected. Nor
is one single sublimation sufficient: no less than three are necessary
to deprive the Sublimate of the corrosive quality which renders it
poisonous. After the third sublimation, the Sublimate being put upon
the tongue gives no considerable sensation of acrimony; nor doth it
retain any more of its former activity than is requisite to make it a
gentle purgative, when administered from six to thirty grains for a
dose.

If a less quantity of Mercury than that above directed be mixed
with the Corrosive Sublimate, the super-abundant Acid will not be
sufficiently saturated; and the less Mercury is added, the more of its
corrosive virtue will the Sublimate retain.

If, on the contrary, a greater quantity of Mercury be added, there
will be more than the Acid can possibly dissolve, and the superfluous
quantity will remain in its natural form of Quick-silver. It is better
therefore to err in the excess than in the defect of the proportion of
Mercury to be added; because the Corrosive Sublimate will take up no
more than is necessary to dulcify it.

Part of the Acid of the Corrosive Sublimate is also dissipated in
vapours during the operation; and it is necessary to allow room for
these vapours to circulate, and a vent to give them passage, or else
they will burst the vessels. These are our reasons for leaving an empty
space in the subliming vessels, and for having their necks no more than
five or six inches long.

The matter which sublimes into the neck of the vessel is always very
acrid; for which reason it must be separated from the Sweet Sublimate.
There remains also at the bottom of the matrass an earthy, reddish
matter; which probably comes from the Vitriol employed in making the
Corrosive Sublimate. This matter must likewise be rejected as useless
after every sublimation.


PROCESS IX.

_The Panacea of Mercury._

Pulverize some Sweet Sublimate, and sublime it in the same manner as
you did thrice before. Repeat this nine times. After these sublimations
it will make no impression on the tongue. Then pour on it aromatic
Spirit of Wine, and set the whole in digestion for eight days. After
that decant the Spirit of Wine, and dry what remains, which is the
_Panacea of Mercury_.


_OBSERVATIONS._

The great number of sublimations, which the Sweet Sublimate is made to
undergo, sweeten it still more, and to such a degree that it leaves no
sensation on the tongue, nor hath any purgative virtue.

The Spirit of Wine in which it is digested after all the sublimations,
is designed to blunt still more the sharpness of any acid particles
that may not have been sufficiently dulcified by the preceding
sublimations.

As Mercury is the specific remedy for venereal disorders, sundry
preparations thereof have been attempted with a view to produce
different effects. Sweet Sublimate is purgative; and for that reason is
not quite proper for procuring a salivation, because it carries off the
humours by stool. The Panacea of Mercury, which, on the contrary, is
not purgative, may raise a salivation when taken inwardly.



SECTION III.

_Of Operations on the_ SEMI-METALS.



CHAP. I.

_Of_ ANTIMONY.


PROCESS I.

_To Separate Antimony from its Ore by Fusion._

Having drilled some small holes, of about two lines in diameter, in
the bottom of a crucible, put into it your Antimonial Ore broken into
little bits, about the size of a hazel nut; lute on its cover; set the
crucible thus prepared in the mouth of another crucible, and close the
joints with lute.

At the distance of half a foot from this compound vessel place bricks
all round, so as to form a furnace; the sides of which must rise as
high as the brim of the uppermost crucible.

Let the bottom of this furnace be filled with ashes, up to the top of
the lower crucible, and the rest of the furnace with lighted coals.
Blow the fire, if it be necessary, with bellows, till the upper
crucible become red. Keep it up in this degree for about a quarter of
an hour. Then take your vessels out of the furnace, and you will find
the Antimony collected in the bottom of the lower crucible, having run
through the holes of the upper one.


_OBSERVATIONS._

The ore of Antimony is one of the most fusible: it always contains a
great deal of Sulphur, and cannot sustain a fire of any force without
being dissipated into vapours. It requires no additament to flux it:
for it is not necessary, on this occasion, that the earthy and stony
matters mixed therewith be brought to fusion. It is sufficient that
the Antimonial part be melted; which, as soon as it becomes fluid, is
carried by its weight to the lower part of the crucible. Thus it is
separated from all heterogeneous matters; which are left in the upper
crucible, while it passes through the holes in its bottom, and forms a
mass in the lower.

The precaution of closing all the apertures of both crucibles is
necessary, on account of the volatility of this mineral: and that the
Antimony, when once melted, may not continue exposed to a great heat,
it is made to run down into a vessel surrounded with ashes only, and
by that means very little affected with heat; ashes being one of those
solid mediums that transmit least of it.


PROCESS II.

_The common Regulus of Antimony._

Reduce crude Antimony to powder. Mix it with three fourths of its
weight of white Tartar, and half its weight of refined Salt-petre,
both pulverized. Into a large crucible made red-hot in the fire,
throw a spoonful of your mixture, and cover it. There will be a very
considerable detonation. When it is over, throw in a second spoonful
of your mixture, and cover the crucible as before: this will produce a
second detonation. Go on thus, till you have thrown in all your mixture.

When the whole has thus fulminated, increase the fire so as to bring
the matter into fusion; that being done, take the crucible out of the
furnace, and immediately pour its contents into an iron cone heated and
greased with tallow. Strike the floor and the cone some gentle blows
with a hammer, to make the Regulus precipitate: and when the matter
is fixed and cold, invert the cone and turn it out. You will see it
consist of two distinct substances; the uppermost of which is a saline
scoria, and the undermost the reguline part. Strike this mass a blow
with a hammer, in the place where these substances join, and you will
by this means separate the scoria from the Regulus; the latter of which
will have the form of a metallic cone, on whose base you will observe
the signature of a bright star.


_OBSERVATIONS._

Antimony, though separated by a former fusion from the earthy and stony
parts of its ore, must nevertheless be still considered as an ore, on
account of the great quantity of Sulphur it contains, which mineralizes
the metalline part or Regulus. Therefore, if you desire to have this
Regulus pure, you must separate it from the Sulphur that is combined
with it. This may be done several ways. The method above proposed
is one of the readiest and easiest, though not altogether free from
inconveniencies, as we shall shew.

The Salt-petre in the mixture detonates by means of the Sulphur of
the Antimony, which it consumes, and from which it separates the
reguline part: but lest it should also consume some of the phlogiston
which gives the Regulus its metalline form, Tartar is added; because
it contains a great deal of inflammable matter, and so is capable
of furnishing enough for the detonation of the Nitre, or rather for
restoring to the metallic earth of the Antimony, the phlogiston that
may be consumed by the Nitre.

If we consider what passes in this operation we shall soon be convinced
that a great deal must be lost in it, and that we do not thereby obtain
near the whole of the Regulus that the Antimony is capable of yielding:
for, 1. the Regulus of Antimony being a volatile substance, much of it
must be dissipated during the detonation; and so much the more as the
detonation is frequently repeated, and continued for a considerable
time. The flowers that may be collected by presenting cold bodies to
the smoke that rises in the operation, and which may be reduced to a
Regulus by the addition of a phlogiston, sufficiently prove what is
here advanced.

2. All the Sulphur of the Antimony is not consumed by the Nitre on
this occasion; and moreover, the Acid of that part thereof which is
burnt, uniting with some of the Alkali produced by the deflagration
of the Nitre and Tartar, forms a Vitriolated Tartar, which meeting
with a sufficient quantity of phlogiston in the mixture produces new
Sulphur. Now this Sulphur, whether not consumed, or reproduced, in the
operation, combining with the Alkali forms a Liver of Sulphur; and that
dissolves part of the Regulus, which by this means remains confounded
with the scoria. The proof of this is, that, if the scoria be mixed
with filings of iron, and fused a second time, you will find at the
bottom of the crucible a button of Regulus, which it contained, and
which is separated therefrom by the interposition of the Iron. We shall
say more on this subject in the process for making the Martial Regulus,
which immediately follows this. If, instead of melting the scoria
with iron filings, we pulverize it, boil it in water, and then pour
an acid into that water; the liquor will instantly grow turbid, and a
Sulphureous Precipitate will fall, commonly called _the Golden Sulphur
of Antimony_; which is nothing else but common Sulphur still combined
with some particles of the Regulus; a new proof of what we advanced
concerning the production of Liver of Sulphur in this operation.

As Regulus of Antimony is of no great value, the loss sustained in
this process is seldom regarded. However, we shall have occasion, in
the sequel, to point out a method of obtaining this Regulus with less
disadvantage.


PROCESS III.

_Regulus of Antimony precipitated by Metals._

Put one part of small iron nails into a crucible, and set it amidst
burning coals, in a melting furnace. When the iron is thoroughly
red-hot, and begins to grow white, add thereto little by little, and at
several times, two parts of crude Antimony in powder. The Antimony will
immediately flow and unite with the Iron. When the Antimony is entirely
melted, add thereto, at several times, the fourth of its weight of
pulverized Nitre: a detonation will ensue, and the whole mixture will
be in fusion.

After you have kept the matter in this condition for some minutes, pour
it into an iron cone, first heated and tallowed. Strike the sides of
the cone with a hammer, that the Regulus may fall to the bottom; and,
when all is cold, separate it from the scoria by a blow with a hammer.
Melt this first Regulus again in another crucible, adding a fourth
part of its weight of crude Antimony. Keep the crucible close shut,
and give no more heat than is necessary to melt the matter. When it is
in perfect fusion, add to it at several times, as you did before, the
sixth part of its weight of pulverized Nitre; and, in half a quarter
of an hour after this, pour the whole into a cone as you did the first
time.

Lastly, melt your Regulus over again a third, or even a fourth time,
always adding a little Nitre, which will detonate as before. If after
all these fusions you pour the Regulus into an iron cone, you will find
it very beautiful, and the star well formed: it will be covered with a
semi-transparent, lemon-coloured scoria. This scoria is extremely acrid
and caustic.


_OBSERVATIONS._

Though Regulus of Antimony unites very readily with Sulphur, and is
always found combined therewith in the earth, we must not thence
conclude that it hath a greater affinity than other substances with
that mineral: on the contrary, all the metals, except Gold, have a
greater affinity than this Semi-metal with Sulphur. Hence it follows
that all the metals, except Gold, are capable of decomposing Antimony,
and separating the sulphureous part from the metalline; so that,
instead of employing Iron, as in our process, Copper, Lead, Tin, or
Silver, may be used, and a Regulus obtained by means thereof.

But as Iron is, of all the metallic substances, that which hath the
greatest affinity with Sulphur, it is on this occasion preferred to
the rest. And from hence two advantages arise: the first is, that the
operation is performed sooner and with greater ease: the second, that
the Regulus is purer, and contains less of the precipitating metal. For
it is a general rule, that, when one metallic substance is employed
to precipitate another, the precipitated substance is always a little
adulterated by the admixture of some particles of the precipitant. Now,
the greater affinity the precipitant hath with the matter united to
that which is to be precipitated, the less doth the precipitate retain
of the precipitant.

In this process the Iron melts very easily by means of the union it
contracts with the Sulphur; which, as we observed before, hath the
property of rendering this metal very fusible, though of itself the
most refractory of all.

The scoria found on the Regulus of the first fusion is a combination
of Iron with the sulphureous part of the Antimony. This scoria is
extremely hard, and not to be separated from the Regulus without some
trouble. The Nitre added, being alkalizated and united therewith,
renders it a little softer, and gives it the property of relenting in
the air. Any Alkaline Salt may be substituted for the Nitre.

The Nitre that is alkalizated in the operation, or the Alkali that is
added, procures moreover another advantage; namely, that, by uniting
with part of the Sulphur of the Antimony, it produces a Liver of
Sulphur, which dissolves the Iron, retains it, and hinders that which
is not yet combined with pure Sulphur from uniting so readily with the
Regulus as it otherwise would do.

Lastly, the addition of Nitre, or an Alkali, contributes greatly to
promote the fusion, to render it more perfect, and to procure a more
complete precipitation of the Regulus.

The second fusion which the Regulus is made to undergo is intended to
purify it from any mixture of Iron. When the fresh Antimony added on
that occasion comes to melt with the Regulus, the Sulphur contained
in the Antimony joins with the ferruginous parts in the Regulus; and
the Iron becoming lighter by this union is thrown up to the surface
of the matter. There it forms a sort of scoria, with which a good
deal of Antimony is mixed; the Regulus not being wholly precipitated,
because there is not Iron enough in the mixture for that purpose. The
Salt-petre added here produces the same effect as in the first fusion.

But if, on one hand, the Regulus precipitated in the first fusion be
purified, by this addition of fresh Antimony, from most of the Iron
with which it was alloyed; on the other hand, this same Regulus cannot
be kept from re-uniting with some sulphureous parts.

In order therefore to separate it entirely from these, it must be
melted over again once or twice more, and a little Nitre added each
time, to consume them by deflagration. But this cannot be done
without consuming also some of the very phlogiston which gives the
Regulus its metalline form: whence it comes to pass that part of the
Regulus is converted to a calx, which, by means of the alkalizated
Nitre, is turned into glass; and it is this glass which mixing with
the scoria gives it the yellow colour observed therein. This yellow
colour may also be in part produced by some ferruginous particles,
of which a small quantity always remains combined with the Regulus,
notwithstanding its former depuration by Antimony.

It is of no use to repeat the fusions of the Regulus oftener than
is above proposed, or to add fresh Nitre with a view to consume the
Sulphur it may still contain: for after the second fusion it contains
none at all, and retains only the phlogiston necessary to give it the
metalline form. So that, by prosecuting the matter further, you would
only calcine and destroy the Regulus to no manner of purpose.

From what hath been said it is plain that, even by this process,
we do not obtain all the Regulus which our Antimony is capable of
yielding; seeing part of it is destroyed by the fusions it must
necessarily undergo with Nitre, in order to its purification. We shall
give a process for obtaining from Antimony the greatest quantity of
Regulus it can possibly be made to yield, after we have treated of its
Calcination, which is in some sort the first step of that process.


PROCESS IV.

_The Calcination of Antimony._

Take an unglazed earthen vessel, wider at top than at bottom; put
into it two or three ounces of crude Antimony finely pulverized. Set
this vessel over a weak charcoal fire, and increase the heat till you
see the Antimony begin to smoke a little. Continue the fire in this
degree, and keep incessantly stirring the Antimony with the shank of a
tobacco-pipe all the while it is upon the fire.

The powder of Antimony, which, before calcination, was of a brilliant
colour inclining to black, will become dull, and look like an earth.
When it comes to have this appearance raise your fire till the vessel
be red-hot, and keep it up in this degree till the matter cease
entirely to smoke.


_OBSERVATIONS._

Antimony, as hath been already said, is a sort of ore consisting of a
metalline or reguline part mineralized by Sulphur.

The design of this calcination is, by the action of fire, to dissipate
the sulphureous part, which is the most volatile, in order to separate
it from the metalline part. It is evidently a real torrefaction; but
the operation is very difficult, and requires a good deal of attention;
for Antimony very easily melts, while at the same time it is necessary
to our success that it do not melt; because when the matter is in
fusion the Sulphur requires a much greater degree of heat to carry it
off. Now, as Regulus of Antimony itself is very volatile, a good deal
of it would be dissipated along with the Sulphur, if it were exposed to
the degree of heat necessary to carry off the Sulphur when the mass is
melted.

Therefore if it happen that the Antimony begin to melt during the
calcination, which is easily perceived by its running into clots, it
must be taken off the fire, and the clotted parts be again pulverized;
after which the calcination is to be prosecuted with a less degree of
heat.

When the Antimony has lost all its brightness, and is become like an
earth, it is time to augment the degree of heat, in order to complete
the calcination; because the last portions of the Sulphur are the
most difficult to raise. Moreover, the inconveniences just mentioned
are not now to be apprehended: for, as the great fusibility of the
reguline part is owing to the Sulphur, what remains, after you have
dissipated the greatest part of the Sulphur, is much less fusible; and,
as the redundant Sulphur of the Antimony cannot be driven off, without
dissipating at the same time a good deal of the phlogiston necessary
to metallize its Regulus, the matter that remains comes much nearer
to the nature of a calx, than to that of a metalline substance; and
consequently partakes of the nature of all metallic calces, which is to
be very fixed.

Antimony may also be calcined by mixing with that mineral an equal
quantity of charcoal-dust. As charcoal is incapable of fusion, it
prevents the Antimony from clotting, as well as from losing so much of
its metallizing phlogiston as it otherwise would: and hence it comes
to pass that the calx of Antimony, prepared in this manner, comes
nearer to the nature of a Regulus, than that which is prepared without
addition.

If you happen to raise the fire too much, in this calcination with
charcoal-dust, the calx will be partly reduced to a Regulus, by means
of the phlogiston which the charcoal furnishes; and then the Regulus
will be dissipated in vapours, especially as this calx, which comes
very near the nature of a Regulus, is not so fixed as that prepared
without addition. For this reason it always continues to smoke, even
when it contains no superfluous Sulphur: and therefore you must not
wait till it cease to smoke before you put an end to your calcination;
for you will lose a great deal of it in vapours. It is time to stop
when the vapours that rise from it, while it is moderately red, do not
smell of burning Sulphur.


PROCESS V.

_Calx of Antimony reduced to a Regulus._

Mix the calx of Antimony, which you intend to reduce, with an equal
quantity of black soap. This mixture will make a thin paste. Put it
little by little into a crucible, previously made red-hot amidst live
coals. Thus let the soap burn till it cease to emit any oily smoke.
Then cover the crucible; make the fire strong enough to melt the
matter, and you will hear it effervesce and boil. When this noise is
over let the crucible cool, and then break it: you will find in it a
beautiful scoria, marked with circles of several colours; and under
that a button of Regulus, which is not yet quite pure, and must be
purified in the following manner.

Pound this Regulus, and mix it with half its weight of an antimonial
calx as perfectly desulphurated as possible. Put it into a crucible,
and cover it: melt the whole, so that the surface of the melted matter
may be smooth and uniform. Let the crucible cool, and then break it:
you will find in it a beautiful button of very pure Regulus, covered
with a scoria having the appearance of an opaque glass, or a kind of
greyish enamel, moulded on the finely radiated surface of the Regulus.


_OBSERVATIONS._

Of all the metalline calces that of Antimony is most easily reduced.
Any matter that contains the phlogiston, even charcoal-dust alone, is
sufficient to procure it the form of a Regulus, without the addition of
any thing to facilitate its fusion; because this calx, which is not of
itself altogether refractory, becomes still more fusible as it combines
with the phlogiston, and approaches to the reguline state.

Though all inflammable matters are capable of procuring the reduction
of the calx of Antimony, yet there are some with which the operation
succeeds better, and produces a greater quantity of Regulus, than it
does with others. Fatty matters, joined with Alkalis, are those which
answer best in this reduction, as they do in most others. The black
flux, for instance, is very proper for this purpose: but Mr. Geoffroy,
who made many experiments on Antimony, found by repeated trials that
black soap is still fitter for it, and that a greater quantity of
Regulus was obtained by its means, than by any other reducing flux
whatever. The process here given is taken from one of the Memoirs on
this subject, which he laid before the Academy of Sciences.

Black soap is made of the lye of a Fixed Alkali, such as potash
for instance, with quick-lime, incorporated by boiling with oil of
lint-seed, rape-seed, or hemp-seed, and sometimes also with animal fat.
The oily matters, contained in this reducing flux, are first burnt and
charred to a coal in the crucible. As soon as they are brought to this
state, the crucible is covered, and the fire is increased, till the
matters melt. At that instant the reduction begins to take place; and
the bubbling noise observed is an effect thereof.

The Regulus obtained by this first fusion is not yet very pure,
being adulterated with the mixture of some unmetallic earth that was
contained in the Antimony, and with a portion of the calcarious earth
of the soap.

Mr. Geoffroy found that his Regulus was contaminated with this
substance, by putting it into water: for on that occasion he observed
a very brisk ebullition about the reguline buttons, which sometimes
lasted above four and twenty hours; and on examining them with a glass,
he discovered some little holes, imperceptible to the naked eye,
through which the water entered, to unite with the lime retained in the
internal parts of the Regulus, which having been recalcined in the
operation required to be slaked.

This Regulus may be purified by simple fusion, without any additament,
because the particles of lime, being lighter than those of the Regulus,
will be thrown up to the surface, on which they will form a sort of
scoria. But Mr. Geoffroy took notice that, in this case, the surface
of the Regulus is never very neat; that it is always sullied with a
very adhesive scoria, and that no star is formed upon it. Besides,
the Regulus must be kept a long while in very thin fusion, that the
heterogeneous matters, which hinder the perfect re-union of its parts,
may have time to rise to the surface by their lightness. But the longer
the Regulus is kept in fusion, the more of it evaporates, because of
its volatility. He was therefore obliged to have recourse to other
means.

We have in the process described the method which succeeded best with
Mr. Geoffroy. It consists in melting the Regulus over again, with the
addition of a little fresh calx of Antimony thoroughly freed from
its Sulphur. This calx being in its nature easily vitrifiable, and
combining with the earthy parts that deprave the Regulus, and which
cannot be vitrified without addition, scorifies these matters, and with
them forms the opaque glass, or kind of enamel which is found over the
Regulus purified in this manner.

The star on that part of the Regulus of Antimony, which was contiguous
to the scoria, is a mark of its purity, and a proof that the operation
was well performed. This star is nothing but a particular disposition
of the parts of the Antimony, which have the property of running
naturally into facets and needles. The perfect fusion, both of the
Regulus and the scoria that covers it, leaves the parts of the Regulus
at liberty to range themselves in this order. This disposition appears
not only on the upper surface of the Regulus, but, if you break the
button, you find the same in its internal parts. There are some round
pyrites whose insides have nearly the same appearance, and seem to
consist of rays issuing from a common center.

The quantity of Regulus obtained by Mr. Geoffroy's process is more than
double of what is procured in the common way, which yields but about
four ounces in the pound; whereas this gives from eight to ten ounces.

When Antimony is calcined with charcoal-dust, what remains after the
dissipation of all the Sulphur is not, properly speaking, a calx of
Antimony; but a sort of Regulus quite formed, and differing from the
common Regulus only in that its parts are disunited, and not collected
into a mass. For if this pretended calx of Antimony be melted, it
directly coalesces into a Regulus, without the addition of any
inflammable matter fit to procure its reduction. Indeed less Regulus is
obtained by this means than when a reductive is added: but nevertheless
this experiment still proves what I advanced; seeing Regulus of
Antimony cannot be melted without losing more or less thereof, either
because some of it is dissipated in vapours, or because part of it
loses its phlogiston in the fusion, and so is converted into a calx.


PROCESS VI.

_Antimony calcined with Nitre. Liver of Antimony. Crocus Metallorum._

Pulverize and mix perfectly together equal parts of Nitre and Antimony:
put the mixture into an iron mortar, and cover it with a tile, which
however must not shut it quite close. With a live coal set fire to the
matter in the mortar, and immediately withdraw it. The mixture will
flame, with great detonation; which being over, and the mortar cooled,
invert it, and strike its bottom to make all the matter fall out. Then,
by a blow with a hammer, separate the scoria from the shining part,
which is the _Liver of Antimony_.


_OBSERVATIONS._

In this operation the Nitre takes fire and detonates with the Sulphur
of the Antimony; and nothing remains but the metallic earth of the
mineral, which, meeting with no substance to restore its phlogiston,
cannot take the form of a Regulus; but, being combined with a large
quantity of fused saline matters, begins itself to flow, and forms a
sort of vitrification; which, however, is not a complete one, because
the matters do not continue long enough in fusion, but cool too soon.
This preparation of Antimony is a violent Emetic. It is used to make
Emetic Wine and Tartar Emetic: it is also given in substance to horses.

The saline matters found after the operation in the form of a scoria,
or perhaps confounded with the Liver of Antimony, are combinations
of Fixed Nitre, partly with the Acid of the burnt Sulphur, forming a
Neutral Salt of the same kind as Vitriolated Tartar, and partly with
some unburnt Sulphur, forming a sort of Liver of Sulphur that contains
a little Regulus. It is usual to pulverize this Liver of Antimony and
wash it with water, in order to dissolve and carry off all the Salts.
When thus pulverized and washed it is called _Crocus Metallorum_. If
Liver of Antimony be melted with any inflammable matter, it will be
reduced to a Regulus; because it is nothing but a metalline calx half
vitrified.


PROCESS VII.

_Another Calcination of Antimony with Nitre. Diaphoretic Antimony._
Materia Perlata. Clyssus _of Antimony_.

Mix one part of Antimony with three parts of Nitre; project this
mixture by spoonfuls into a crucible kept red-hot in a furnace. Each
projection will be attended with a detonation. Continue doing this till
you have used all your mixture: then raise the fire, and keep it up
for two hours; after which throw your matter into a pan full of hot
water. Let it lie steeping in water kept hot for a whole day. Then pour
off the liquor: wash the white powder you find at bottom in warm water;
and repeat the ablutions till the powder become insipid. Dry it, and
you have _Diaphoretic Antimony_.


_OBSERVATIONS._

This operation differs from the preceding one, in respect of the
quantity of Nitre deflagrated with the Antimony. In the former we added
one part only of Nitre to one part of Antimony; but in this three parts
of Nitre are put to one of the mineral; and the calx resulting from
this mixture is of course very different from the other.

In the first place, Liver of Antimony hath a reddish colour; whereas
Diaphoretic Antimony is very white. Secondly, Liver of Antimony is in a
manner half vitrified; Diaphoretic Antimony is, on the contrary, in the
form of a powder, the parts of which have no connection together.

The reason of these differences will easily appear, if we consider,
that, Liver of Antimony being the result of calcination with one part
of the Nitre only, which is not sufficient to consume all the Sulphur
of the mineral, what remains after the detonation is not entirely
deprived of its phlogiston; from whence arise the colour it retains and
the ease with which it flows in the fire: but that, when three parts of
Nitre are added instead of one, this quantity is not only sufficient to
consume all the Sulphur and the phlogiston of the Antimony, but even
more than enough; seeing that, after the operation, some Nitre is still
found undecomposed.

The calx of Antimony, prepared by calcining it with three parts of
Nitre, is therefore deprived of all its phlogiston. This is the cause
of its whiteness, and the reason why it is not half vitrified by
the operation, as Liver of Antimony is: for we know that the more a
metallic calx is deprived of its phlogiston, the less fusible and
the less vitrifiable it is. This calx of Antimony bears the name of
_Diaphoretic Antimony_, or _Diaphoretic Mineral_: because, being
neither emetic nor purgative, it is thought to have the virtue of
promoting perspiration.

Antimony may be calcined with various proportions of Nitre, between
that used to make Liver of Antimony, and this with which Diaphoretic
Antimony is prepared; and from these calcinations will result calces
possessed of properties both chymical and medical, of an intermediate
nature between the extremes of those two preparations. The nearer
the proportion of Nitre comes to that employed in preparing Liver of
Antimony, the more will the resulting calx resemble that preparation;
and in the same manner, a calx prepared with a greater proportion of
Nitre will so much the more resemble Diaphoretic Antimony, as the
proportion of Nitre used comes nearer three parts of Nitre for one of
Antimony.

It is not necessary that Antimony in substance be employed to make the
Diaphoretic Mineral: you may, if you please, make use of its Regulus.
But as the Regulus contains no Sulphur, nor any more phlogiston than
is requisite to secure its metalline form, it is needless to put three
parts of Nitre to one of Regulus; an equal quantity thereof being
sufficient.

The matter is projected by spoonfuls, to the end that, by gradual and
repeated detonations, the Antimony may be more perfectly calcined:
it is also with a view to destroy entirely the small remainder of
phlogiston, which may have escaped the action of the Nitre, that the
matter is kept red-hot in the crucible for two hours.

The whole is afterwards thrown into hot water, and left steeping
therein for several hours, with design to give the water time to
dissolve all the saline matters that are mixed with the Diaphoretic
Calx. When crude Antimony is used in making this preparation, these
saline matters are, 1. an Alkalizated Nitre; 2. a Neutral Salt formed
by the union of the Acid of Sulphur with part of that Alkali, as in the
preparation of Liver of Antimony; 3. a portion of undecomposed Nitre.

The water in which the Diaphoretic is washed takes up moreover a
portion of the calx of Antimony, which is exceeding finely attenuated,
and continues united with the fixed Nitre, and suspended therewith in
the liquor. This matter is to be separated from the Fixed Nitre, by
mixing the water wherein it is dissolved with an Acid, which unites
with the Alkali, and precipitates this matter in the form of a white
powder, to which the name of _Materia Perlata_ hath been given.
Because it is precipitated in the same manner as the Golden Sulphur of
Antimony, and, like that, is found in the water with which the saline
matters are washed out, after the detonation of Nitre with Antimony,
some Chymists have given it, though very improperly, the name of the
_Fixed Sulphur of Antimony_.

This matter is a true Calx of Antimony, and differs from Diaphoretic
Antimony in nothing but its being still more perfectly calcined. It
is so indeed to such a degree that it is impossible to restore its
metalline form, or reduce it to a Regulus, by the addition of an
inflammable matter. Diaphoretic Antimony, on the contrary, may be
re-metallized, by supplying it with phlogiston: but it must be observed
that, in whatever manner you go about this, you will obtain a much
smaller quantity of Regulus, than when you use a Calx of Antimony
prepared with a smaller quantity of Nitre.

If you attempt to reduce either Liver of Antimony or Diaphoretic
Antimony, great care must be taken to wash them thoroughly, in order
to free them from every thing saline: for, without this precaution,
the Acid of the Sulphur, having, as was observed, formed a Neutral
Salt with the Alkali of the Nitre, will combine with the inflammable
matter added to revivify the calx of Antimony and reproduce a Sulphur;
which, uniting afterwards with the same Alkali, will produce a Liver
of Sulphur, that will dissolve part of the Regulus, hinder its
precipitation, and greatly lessen the quantity which might otherwise be
expected.

A particular sort of Diaphoretic Antimony is sometimes prepared for
Medical uses, which hath a purgative quality: it is not washed at all,
and is therefore called _Unwashed Diaphoretic Mineral_.

Diaphoretic Antimony may also be prepared in close vessels, by means
of which the vapours that rise during the operation are retained.
For this purpose a tubulated retort is employed, having a series of
adopters fitted to it. The retort is placed in a furnace, and heated
till its bottom become red: then a very small quantity of the mixture,
for making Diaphoretic Antimony, is introduced through the tube in
the upper part of the retort, and the tube immediately stopped. A
detonation ensues, and the vapours expand themselves into the adopters,
where they condense. This is repeated till the intended quantity of
matter be used. After the operation some white flowers are found
sublimed in the neck of the retort, and a small quantity of liquor in
the recipients. This liquor is acid. It consists of some of the Acid
of the Nitre, which the Acid of the Sulphur hath expelled from its
basis, and also a little of the Acid of the Sulphur carried up by the
heat before it could combine with the basis of the Nitre. This liquor
is called _Clyssus of Antimony_. The name of _Clyssus_ is given to all
liquors in general that are prepared by this method.

The white flowers found in the neck of the retort are flowers of
Antimony; that is, a calx of Antimony forced up by the heat, and by the
impetus of the detonation. These flowers may be reduced to a Regulus.
What remains in the retort is the same with the matter that remains
in the crucible, wherein the mixture of Nitre and Antimony for making
Diaphoretic Antimony hath been deflagrated.

Neither Diaphoretic Antimony nor the Pearly matter are soluble in any
Acid.


PROCESS VIII.

_Calx of Antimony Vitrified._

Take any quantity you please of calx of Antimony, made without
addition; put it into a good crucible, which set in a melting furnace:
kindle the fire gradually, and leave the crucible uncovered at the
beginning.

A quarter of an hour after the matter is red-hot, cover the crucible,
and excite the fire vigorously till the calx melt. You may know when it
is thoroughly melted, by dipping into the crucible an iron wire, to the
end of which a little knob of glass will adhere, if the matter be in
perfect fusion. Keep it in fusion for a quarter of an hour, or rather
longer if your crucible can bear it. Then take it out of the furnace,
and immediately pour out the melted matter on a smooth stone, made very
hot for the purpose: it will presently fix into a yellow Glass.


_OBSERVATIONS._

All the calces of Antimony, when exposed to a violent fire, are
converted into Glass; but not all with the same facility. In general,
the more of their phlogiston they have lost in the calcination, the
more difficult is their vitrification. This causes also a difference in
the colour of the Glass; which will be of so much a deeper yellow, and
the nearer to a red, the less the Antimony was calcined.

It frequently happens, when we employ a calx of Antimony which is not
sufficiently deprived of its phlogiston, that we find in the crucible a
button of Regulus, which, being heavier than the Glass, always lies at
the bottom. With a view to avoid this inconvenience, and to dissipate
completely the excess of phlogiston that may still be left in the calx
of Antimony, we direct the crucible to be left uncovered for some time,
at the beginning of the operation. If, notwithstanding this precaution,
any Regulus be still found at the bottom of the crucible, and you
resolve to vitrify it, the crucible must be returned to the furnace,
and the fusion continued; by which means the Regulus will at last be
converted into Glass.

If, on the contrary, you meet with any difficulty in effecting the
vitrification, on account of your having employed a calx that hath lost
too much of its phlogiston, such as Diaphoretic Antimony, or the Pearly
matter, the fusion may be greatly facilitated by throwing into the
crucible a little crude Antimony.

Glass of Antimony is a most violent emetic. This Glass, as well as
Liver of Antimony, is employed in preparing Emetic Wine and Emetic
Tartar.

It may be resuscitated, like the calces of Antimony, into a Regulus,
by re-uniting it with a phlogiston. For this purpose it must be
finely pulverized, thoroughly mixed with some black flux, and melted
in a covered crucible. This Glass, as well as that of Lead, hath the
property of greatly promoting the vitrification of matters that are to
be scorified.


PROCESS IX.

_Kermes Mineral._

Break any quantity you will of Hungarian Antimony into little bits:
put it into a good earthen coffee-pot: pour on it twice its weight of
rain-water, and a fourth part of its weight of well filtered liquor
of Nitre fixed by charcoal. Boil the whole briskly for two hours, and
then filter the liquor. As it cools it will acquire a red colour, grow
turbid, and leave a red powder on the filter.

Return your Antimony into the coffee-pot. Pour on it as much rain-water
as before, and three fourths of the former quantity of the liquor of
Fixed Nitre. Boil it again for two hours, and then filter the liquor.
It will again deposite a red sediment. Return your Antimony into the
coffee-pot: pour on it the same quantity of rain-water, and half the
first quantity of the liquor of Fixed Nitre. Boil it again for two
hours, and then filter the liquor as formerly. Wash all these sediments
with warm water, till they become insipid; then dry them, and you have
the _Kermes Mineral_.


_OBSERVATIONS._

If you recollect what we said concerning the property which Fixed
Alkalis possess of uniting with Sulphur, both by fusion, and, when
those Salts are resolved into a liquor, by boiling, and of forming
therewith a Liver of Sulphur, which dissolves all metalline substances,
you will readily comprehend the nature of this Kermes.

Antimony consists of a sulphureous and a reguline part. Therefore,
if this mineral be boiled in a solution of a Fixed Alkali, such as
Nitre fixed by charcoal, the Alkali will dissolve the Sulphur of the
Antimony, and form therewith a Liver of Sulphur, which, in its turn,
will dissolve the reguline part. Now, Kermes Mineral, prepared as above
directed, is no other than a Liver of Sulphur combined with a certain
quantity of Regulus of Antimony.

Mr. Geoffroy hath set this truth in the clearest light, by his
accurate analysis of the Kermes Mineral. The experiments he made on
that subject are circumstantially related in several Memoirs printed
in the volumes of the Academy for 1734 and 1735. By combining Acids
with the Kermes he demonstrated, 1. the existence of Sulphur in this
compound; having separated from it a burning Sulphur, which cannot
be mistaken for any other than the Sulphur of Antimony. In order to
obtain this Sulphur pure, an Acid must be employed that will not only
absorb the Alkali, but also perfectly dissolve the reguline part that
might otherwise remain united with the Sulphur. _Aqua regia_ was the
Acid which succeeded best with Mr. Geoffroy. 2. He also proved that
there is a Fixed Alkali in the composition of the Kermes; seeing the
Acids with which he precipitated the Sulphur became Neutral Salts, and
just such as those very Acids combined with a Fixed Alkali would have
constituted: that is, the Vitriolic Acid produced a _Sal de duobus_;
the Nitrous Acid a regenerated Nitre; and the Marine Acid a regenerated
Sea-salt. 3. Mr. Geoffroy demonstrated the reguline part of Antimony
to be an ingredient in the Kermes; having procured therefrom an actual
Regulus of Antimony, by fusing it with the black flux.

In preparing the Kermes it is necessary to renew the liquor from time
to time, as above directed; because, when it is once impregnated with
Kermes to a certain degree, it can take up no more; and consequently
the same liquor cannot operate again on the Antimony. Experience hath
shewn, that, if the doses above prescribed be applied, the liquor will
after two hours boiling be sufficiently saturated with Kermes.

If the liquor in which the Kermes is dissolved be filtered while it
is very hot, and almost boiling, it leaves nothing on the filter; the
Kermes passing through with it: but as it cools it grows turbid, and
gradually deposites the Kermes. Therefore it ought not to be filtered
till it be cold; or, if it be filtered while it is boiling hot, in
order to separate from it some coarse particles of Antimony not yet
converted into Kermes, it must be filtered a second time when it is
cold, in order to get the Kermes.

Though in the method usually practised for making Kermes, the Antimony
is boiled only thrice, yet it does not follow that more Kermes may not
be obtained from it, or that but little more would be obtained by a
fourth and fifth boiling; on the contrary, it would yield considerably
more. Mr. Geoffroy observed, that he got more Kermes by the second
boiling than by the first, and still more by the third than by the
second; and that the yield goes on increasing in this manner to a very
great number of times, which he hath not determined. This increased
effect arises from hence, that by multiplying the frictions of the
little bits of Antimony against each other, new surfaces are exposed to
the action of the Alkaline liquor, and furnish it with more Sulphur;
while the addition of this sulphur renders the hepar more active and
more penetrating; or, if you please, produces a new hepar every time
the matters are boiled. When the Alkaline liquor is once saturated
with Kermes, it ceases to act, and forms no new hepar; but it does
not follow that its virtue is quite exhausted. To restore its ability
of acting as well as at first, or nearly so, you need only let it
cool, and deposite the Kermes dissolved in it. We owe this singular
observation also to Mr. Geoffroy: he had the patience to go through no
less than threescore and ten boilings with the same liquor, without
adding any thing but rain water, to supply the place of what was
dissipated by evaporation: and he always obtained a pretty considerable
quantity of Kermes by each boiling, for the reason given above.

Boiling is not the only means of making Kermes. Mr. Geoffroy found the
way of making it by fusion. For this purpose you must mix accurately
one part of very pure Fixed Alkali, dried and pulverized, with two
parts of Hungarian Antimony also pulverized, and melt the mixture.
Mr. Geoffroy made use of a retort. When the mass is melted, it must
again be pulverized, while it is still hot, and then put into, and
kept in, boiling hot water for an hour or two; after which the liquor,
now become saline and antimonial, must be filtered into another vessel
filled with boiling water. Every ounce of Antimony treated in this
manner yields, by thrice boiling the melted mass, from six drams to
six drams and a half of Kermes; which differs from the Kermes made by
boiling, only in that it is not quite so soft to the touch, having in
every other respect the same qualities.

As Liver of Sulphur is made two different ways, to wit, by boiling and
by fusion, and as the Kermes is nothing but a Liver of Sulphur in which
the reguline part is dissolved; it follows that Kermes may be made by
fusion as well as by boiling. It is necessary to pulverize the melted
mass, and to steep it in boiling hot water for an hour or two, that the
water may dissolve and divide it sufficiently to make the Kermes fine
and beautiful.

With the same view, that is, to make it finer and more perfect, Mr.
Geoffroy orders the water saturated with the Kermes made by fusion,
to be received, when filtered, in a vessel full of other boiling hot
water. He observed, that when the liquor impregnated with Kermes cools
too fast, the Kermes that precipitates is much coarser. The warm
solution of Kermes is diffused through the boiling-hot water into which
it is filtered, and is thereby enabled to retain its heat so much the
longer.

From what hath been said on the nature of Kermes, it plainly appears
that there must be a great resemblance between it and the Golden
Sulphur of Antimony, obtained from the scoria, either of plain Regulus
of Antimony, or of the Liver of Antimony; this Golden Sulphur being
no other than a portion of the Antimony combined with the Nitre
alkalizated during the operation.

Yet there is a difference in the manner of precipitating these two
compounds: for the Kermes precipitates spontaneously, on the bare
cooling of the water in which it is dissolved; whereas an Acid is
employed to precipitate the Golden Sulphur suspended in the water, with
which the scoria of the plain Regulus of Antimony, or that of Liver of
Antimony, hath been washed. This gives some ground to suspect that the
reguline part is not so intimately united with the Liver of Sulphur in
the Kermes, as in the scoriæ from which the Golden Sulphur is obtained.


PROCESS X.

_Regulus of Antimony dissolved in the Mineral Acids._

Compound an _aqua regis_ by mixing together four measures of Spirit of
Nitre, and one measure of Spirit of Salt: on a sand-bath moderately
heated place a matrass, into which pour sixteen times as much of this
_aqua regis_ as you have Regulus to dissolve. Break your Regulus
into little bits; and throw them successively one after another into
the matrass, observing not to add a new one till that put in before
is entirely dissolved: continue this till your Regulus be all used.
By degrees, as the dissolution advances, the liquor will acquire a
beautiful golden colour; which, however, will insensibly disappear, as
the white fumes that continually ascend from it evaporate.


_OBSERVATIONS._

Regulus of Antimony is one of those metalline substances that dissolve
with the greatest difficulty. Not but that most of the Acids attack
and corrode it; but they do not make a clear, limpid solution thereof:
they in some sort only calcine it, and this semi-metal, as fast as
it dissolves, precipitates of its own accord in the form of a white
magistery. In order to effect a complete dissolution thereof, it is
necessary to employ an _aqua regis_ compounded as directed, and in
the dose prescribed in the process, which is wholly taken from Mr.
Geoffroy's Memoirs on Antimony mentioned above.

If, instead of the Regulus, small bits of crude Antimony be thrown into
the _aqua regis_, the Acid will attack and dissolve the reguline part,
and so separate it from the sulphureous part which it will not touch.
When the dissolution is finished, the particles of Sulphur being now
become lighter, because no longer united with the metalline part, will
float upon the liquor. Being collected they form a true Sulphur, which
seems no way different from common brimstone. This operation, you see,
is a sort of Parting Process.

The Vitriolic Acid, whether concentrated or much weakened with water,
does not act when cold either on Antimony or on its Regulus. This Acid
only dims the splendour of the facets of the Regulus; but if one part
of exceeding pure Regulus of Antimony be put into a retort, and four
parts of clear concentrated Oil of Vitriol poured on it, as soon as the
Acid is heated it turns brown, and emits a most suffocating smell of
Sulphur, which increases as the Regulus is penetrated and corroded by
the Acid.

On raising the fire, there separates from it a matter that seems
mucilaginous; and when the Acid hath boiled some time, the Regulus is
converted into a white saline mass, as Mercury is in the preparation of
Turbith mineral. At the same time a little Sulphur sublimes into the
neck of the retort. At last all the Oil of Vitriol passes over into the
receiver, and leaves the Regulus in a white, spungy, saline mass in the
retort. When the fire is out, the vessels unluted, and the receiver
separated from the retort, there rises a white vapour like that of the
smoking liquor of Libavius.

The saline mass left in the retort, after the operation, is found
increased to near double its weight: this increased weight is owing to
the Acid that hath united with the Regulus.

This combination of the Vitriolic Acid with the Regulus of Antimony
is excessively caustic, and cannot, for that reason, be administered
internally.

The purest Spirit of Salt hath no sensible effect either on Antimony
or its Regulus: but if Antimony be coarsely pounded, it separates
therefrom, though slowly, some light, sulphureous flakes.

The action of Spirit of Nitre on this metallic substance is more
perceptible: by little and little it attacks the plates of the
Antimony, which discharge a great number of air-bubbles. As the
dissolution advances, the Acid acquires a greenish colour inclining to
blue; and if there be not too much of it, it will be almost entirely
imbibed by the Antimony, penetrate between its _laminæ_, and exfoliate
them in the direction of the needles that compose them. If there be
too much of the Acid, that is, if it rise above the Antimony, it will
destroy these plates, and reduce them to a white powder.

But when the Acid is imbibed slowly, we discover between the swelled
_laminæ_ little saline transparent crystals, that vegetate much in the
same manner as those of the pyrites, in which small crystals of Vitriol
are frequently observed, whose figures are not very well determined.
These little crystals between the Antimonial plates are intermixed with
yellow particles, which being carefully separated burn like common
Sulphur.

All these useful observations, concerning the action of the Acids on
Antimony and its Regulus, we owe likewise to Mr. Geoffroy; who advises
the collecting a quantity of these little crystals in time; because
they disappear soon after they are formed, being probably covered by
the white powder, or magistery, which is continually produced as fast
as the Nitrous Acid disunites and separates the needle-like fibres of
the Antimony.

Mr. Geoffroy observed the same sort of crystals on the Regulus of
Antimony, when substituted for crude Antimony in this experiment;
but it requires a great deal of care to separate these crystals;
for as soon as the air comes into contact with them they lose their
transparency; and if you wait till the Regulus be in some measure
converted into a magistery, they are not then to be distinguished.

In order therefore to have a good view of these crystals, the Regulus
must be broken to pieces; these pieces put in a glass bason, and Spirit
of Nitre poured on them to half their heighth, but not to cover them.
This Acid penetrates them, exfoliates them in white scales; and on the
surface of these scales the crystals shoot of a dead white colour. In
two or three days time these crystals vegetate and grow in the form
of cauli-flowers: they must then be gathered, to prevent their being
confounded in the white magistery which continues to be produced,
and would not suffer them to be distinguished. If you attempt to
dissolve the reguline part of Antimony by an _aqua regis_ compounded
in different proportions, and applied in a different dose from what
is prescribed in the process, the Regulus of Antimony will only be
calcined, as it is by the other Acids, and will precipitate in the form
of a white magistery as fast as it dissolves, so that no part thereof
will remain united with the solvent. The proof of this is, that if an
alkaline liquor be poured, even to the point of saturation, upon the
_aqua regis_ that hath thus dropt the Antimony, no new precipitate will
be deposited.


PROCESS XI.

_Regulus of Antimony combined with the Acid of Sea-salt. Butter of
Antimony. Cinabar of Antimony._

Pulverize and mix thoroughly six parts of Regulus of Antimony, and
sixteen parts of Corrosive Sublimate. Put this mixture into a glass
retort that hath a wide short neck, and let one half of its body at
least be left empty. Set it in a reverberatory furnace, and having
fitted a recipient thereto, and luted the joint, make a very small fire
at first, to heat it slowly. Increase it afterwards by degrees, till
you see a liquor ascend from the retort that grows thick as it cools.
Keep up the fire to this degree as long as you see any of this matter
come over.

When no more rises with this degree of fire, unlute your vessels, take
off the receiver, and in its place substitute another filled with
water. Then increase your fire by degrees till the retort be red-hot.
Some running Mercury will fall into the water, which you may dry and
keep for use; it being very pure.


_OBSERVATIONS._

In our observations on the preceding process, we took notice that the
purest Marine Acid, in the form of a liquor, will not dissolve the
reguline part of Antimony. Here this very Acid combined with Mercury,
and applied in a dry form to the Regulus of Antimony, quits the Mercury
with which it was united, in order to join this very Regulus, as having
a greater affinity therewith. This operation is a further proof of what
we advanced on the subject of Mercury; to wit, that several metallic
substances, which are not soluble by certain Acids when in a fluid
state, may be dissolved by those Acids when most highly concentrated;
as they are when combined with any other substance in a dry form, and
are separated from it by the force of fire. Their efficacy is also
further promoted by their being reduced, on this occasion, into subtile
vapours.

The Marine Acid combined with the reguline part of Antimony doth not
form a hard, solid compound; but a kind of soft substance, that melts
in a very gentle heat, and also becomes fixed by the least cold, much
in the same manner as butter; and from this property it hath its name.

Soon after mixing the Regulus with the Corrosive Sublimate, the matter
sometimes grows considerably hot: this is occasioned by the Marine
Acid's beginning to act on the reguline part, and to desert its Mercury.

The Butter of Antimony rises with a very moderate heat; because the
Acid of Sea salt hath the property of volatilizing, and carrying up
along with it, the metallic substances with which it is combined: and
for this reason a very gentle heat only is required at the beginning of
the operation.

It is absolutely necessary that the neck of the retort be wide and
short: for otherwise if the Butter of Antimony should fix and be
accumulated therein, it might stop up the passage entirely, and
occasion the bursting of the vessels. By this operation we obtain eight
parts and three quarters of fine Butter of Antimony, and ten parts of
running Mercury; there being left in the retort one part and a half of
a rarefied matter, black, white, and red. This is probably the most
earthy and most impure part of the Regulus of Antimony.

It is of the utmost consequence to the operator that he avoid with the
greatest care the vapours that issue from the vessels, because they are
extremely noxious, and may occasion mortal disorders. The Butter of
Antimony is a most violent Corrosive and Caustic.

When all the Butter is risen, the receiver is shifted in order to
receive the Mercury; which, being disengaged from the Acid that gave
it a saline form, appears in its natural form of Quick-silver: but it
requires a much greater degree of heat than the Butter of Antimony to
raise it by distillation.

If crude Antimony, instead of Regulus of Antimony, be mixed with
Corrosive Sublimate, a Butter of Antimony will be obtained in the same
manner; but, instead of having a running Mercury after the Butter, you
will find a Cinabar sublimed into the neck and upper concavity of the
retort.

The reason of this difference is easily conceived: for when the
Regulus is used, the Mercury being deserted by its Acid finds no other
substance to unite with, and so rises in the form of Quick-silver; but
when crude Antimony is employed instead of its Regulus, as the reguline
part thereof cannot combine with the Acid without quitting its Sulphur,
so this Sulphur, being at liberty, unites with the Mercury, which is so
likewise, and therewith forms a Cinabar; which from its origin is named
_Cinabar of Antimony_. When you intend to make both Butter and Cinabar
of Antimony at the same time, six parts of Antimony must be mixed with
eight of Corrosive Sublimate; and care must be taken, while the Butter
is coming over, to warm the neck of the retort by holding some live
coals near it, with the precautions necessary to avoid breaking it.
This warmth makes the Butter melt and run into the receiver; whereas,
being thicker and of a much denser consistence than that made with the
Regulus, it would otherwise gather in the neck of the retort, choak it
entirely, and burst the vessel.

When the Butter is drawn from crude Antimony, more circumspection is
necessary to make it of a beautiful white colour, than when it is
obtained from the Regulus: for, if the fire be too strong during the
distillation, or if the receiver be not soon enough separated from the
neck of the retort, certain red sulphureous vapours, the fore-runners
of the Cinabar, will at last ascend, and mixing with the Butter give it
a brown colour.

In order to restore its beauty it must be put into a clean retort,
and rectified by distilling it over again with a gentle sand-heat.
By this rectification the Butter of Antimony becomes more fluid; and
by re-distilling it a second time you may give it the thinness and
fluidity of an oil.

After the operation there will be found in the receiver three parts and
three quarters of Butter of Antimony, and some small crystals adhering
to its inside, in the form of sprigs. When you break the retort there
exhales from it a sulphureous odour; and you will find in it seven
parts of Cinabar of Antimony, the greatest part of which is usually in
compact glebes, that are heavy, smooth, shining, blackish throughout
most of the mass, but in some places red: another part thereof appears
in shining needles, and the rest in powder.

When all the Butter of Antimony is come over, and you begin to see the
red vapours that predict the approaching ascent of the Cinabar, the
receiver containing the Butter must be removed, lest the colour of the
Butter should be spoiled by those sulphureous vapours. Another receiver
is usually fitted on, without luting; in which a small quantity of
running Mercury is sometimes found, when the operation is finished.

There remains, at the bottom of the retort, a fixed, shining,
crystalline, black mass, which may be reduced to a Regulus by the
common method.

Butter of Antimony may also be obtained from a mixture of Antimony with
any of the other preparations of Mercury in which the Acid of Sea-salt
is an ingredient; such as sweet Sublimate, the Mercurial Panacea, and
White Precipitate: but as none of these combinations contain so great
a proportion of that Acid as is in the Corrosive Sublimate, the Butter
obtained by their means is far from being so caustic and so fiery as
that which rises from a mixture of Antimony, or its Regulus, with
Corrosive Sublimate.

Silver precipitated by the Acid of Sea-salt, and ready to be melted
into a _Luna cornea_, being mixed with powdered Regulus of Antimony
yields likewise a Butter of Antimony.

If you propose to make it by this means, you must mingle one part of
the Regulus of Antimony in powder with two parts of the Precipitate;
put this mixture into a glass retort of such a size that it may fill
but one half thereof; set it in a furnace; apply a receiver; begin
with a gentle heat, which will make a clear liquor come over; and then
increase your fire by degrees. White vapours will rise and condense
into a liquid Butter; and in the mean time there will be a slight
ebullition in the receiver, attended with a little heat. Continue the
fire till nothing more will come over; then let your vessels cool and
unlute them.

You will find in the receiver an Oil or Butter of Antimony, partly
fluid and partly congealed, somewhat inclined to yellow, weighing an
eighth part more than the Regulus of Antimony made use of.

The inside of the retort will be carpeted over with small white
flowers, of a brilliant silver colour, and an acid taste; and in the
bottom of the retort will be found a hard, compact, ponderous mass,
difficult to break, yet falling of itself to a powder; its colour
externally grey, white, and blueish; internally black, and shining much
like Regulus of Antimony; having a saltish taste on its surface, and
weighing about a sixteenth less than the Precipitate of Silver employed
in the operation.

This experiment demonstrates that the Acid of Sea-salt hath a greater
affinity with Regulus of Antimony than with Silver.

The Butter of Antimony prepared by this method is somewhat less caustic
than that made with Corrosive Sublimate. It is called the _Lunar Butter
of Antimony_.

The effervescence that arises in the receiver is remarkable. Probably
the Acid of Sea-salt, though reduced into vapours when it ascends out
of the retort, is not yet perfectly combined with the reguline part
of the Antimony, which it nevertheless carries over with it, and the
union is completed in the receiver; which occasions the effervescence
observed.

The little white silvery flowers, adhering to the inside of the retort,
are flowers of Regulus of Antimony, which sublime towards the end of
the distillation.

The compact mass, found at the bottom of the retort, is no other than
the Silver separated from its Acid, and combined with a portion of the
Regulus of Antimony. The colours and the saltish taste of its surface
are occasioned by a remainder of the Marine Acid. This Silver is
rendered brittle and eager by the union it hath contracted with some of
the Regulus of Antimony.

It is easy to purify it, and restore its ductility, by separating it
from the Regulus of Antimony. There are several ways of doing this:
one of the most expeditious is to flux it with Nitre, which burns and
converts to a calx the semi-metal with which the Silver is adulterated.


PROCESS XII.

_Butter of Antimony decompounded by means of Water only. The_ Pulvis
Algaroth, _or_ Mercurius Vitæ. _The Philosophic Spirit of Vitriol._

Melt with a gentle heat as much Butter of Antimony as you please.
When it is melted, pour it into a large quantity of warm water. The
water will immediately grow turbid, but whitish, and let fall a great
quantity of white powder. When all the precipitate is settled, decant
the water: pour on fresh warm water; and having thus edulcorated it
by several ablutions, dry it, and you have the _Pulvis Algaroth_, or
_Mercurius Vitæ_.


_OBSERVATIONS._

In the preceding processes we observed that the Marine Acid will not
dissolve the reguline part of Antimony, unless it be very highly
concentrated, and more so than it can possibly be while in the form of
a liquor. Of this the experiment before us is a further proof. Whilst
the Marine Acid is so perfectly dephlegmated, as it is in Corrosive
Sublimate and Butter of Antimony, it remains combined with the reguline
part of Antimony; but if this combination be dissolved in water, the
moment the Acid is weakened by the interposition of the particles of
water, it becomes incapable of continuing united with the semi-metal
which it had before dissolved; deserts it, and lets it fall in the
form of a white powder.

The _Pulvis Algaroth_ is therefore no other than the reguline part of
Antimony, attenuated and divided by the union it had contracted with
the Acid of Sea-salt, and afterwards separated from that Acid by the
intervention of water alone. The proof is, that this powder retains
none of the properties of the Butter of Antimony: it is neither so
fusible nor so volatile; on the contrary, it is capable of sustaining a
very strong degree of fire, without subliming and without melting: it
may be reduced to a Regulus: it hath not now the same caustic nature:
it is only an emetic; which however is extremely violent, and on that
account is never prescribed by any prudent physician.

Another proof, that the Marine Acid is separated from the Regulus of
Antimony in the precipitation of the _Pulvis Algaroth_, is, that the
water in which this precipitation is made becomes acid, or a sort
of weak Spirit of Salt. If it be evaporated, and concentrated by
distillation, a very strong acid liquor may be obtained from it. This
Acid goes, very improperly, by the name of the _Philosophic Spirit of
Vitriol_; for it is rather a Spirit of Salt.

The _Pulvis Algaroth_, made with Butter of Antimony procured from the
Regulus, is whiter than that made with Butter of Antimony procured
from crude Antimony; probably because the latter always retains some
sulphureous particles.

Butter of Antimony exposed to the air attracts the moisture thereof,
and partly runs into a liquor; but, as fast as this liquor is
produced, it deposites a white sediment, which is an actual _Pulvis
Algaroth_. This also is very agreeable to what we advanced touching
the decomposition of Butter of Antimony by the addition of water. The
Butter attracts the moisture of the air, because the Acid it contains
is exceedingly concentrated; and this moisture produces the same effect
as water purposely added.


PROCESS XIII.

_Bezoar Mineral. The Bezoartic Spirit of Nitre._

Melt Butter of Antimony over warm ashes, and put it into a phial or
matrass. Gradually pour on it good Spirit of Nitre, till the matter
be entirely dissolved. This usually requires as much Spirit of Nitre
as there is Butter of Antimony. During the dissolution fumes will
rise, which must be carefully avoided. Pour your solution, which will
be clear and of a reddish colour, into a glass cucurbit, or a pan of
stone-ware: set it in a sand-bath, and evaporate to dryness with a
moderate heat. There will be left a white mass, weighing a fourth part
less than the whole quantity used, both of the Butter and the Spirit
of Nitre. Let it cool, and again pour on it as much Spirit of Nitre as
you used the first time. Place the vessel again in the sand-bath, and
evaporate the moisture as before. You will have a white mass that hath
neither gained nor lost in weight. On this pour, for the third time,
the same quantity of Spirit of Nitre as you did the first time. Again
evaporate the moisture to perfect dryness: then increase your fire,
and calcine the matter for half an hour. You will have a dry, friable,
light, white matter, of an agreeable acid taste; which will fall into
a coarse powder, and must be kept in a phial carefully stopt. This
is _Bezoar Mineral_: it is neither caustic nor emetic, and has only
a sudorific virtue. It obtained the name it bears, because, like the
animal Bezoar, it was imagined to have the property of resisting poison.


_OBSERVATIONS._

It is not surprising that the Nitrous Acid poured on Butter of Antimony
should dissolve it, and unite with it: for with the Marine Acid, which
makes a part of this combination, it forms an _aqua regis_, which we
know is the true solvent of the reguline part of Antimony. But in this
dissolution, and the changes it produces, there are some things very
remarkable and worthy of attention. 1. The Nitrous Acid, by uniting
with the Butter of Antimony, deprives it of its property of rising with
a very gentle heat, and makes it much more fixed: it can now be dried,
and suffer all its moisture to be evaporated; which is not to be done
with pure Butter of Antimony: for that, being exposed to a certain
degree of heat, instead of letting go its moisture and remaining dry,
rises wholly, without the least appearance of any separation of parts.

2. The Butter of Antimony, which, before its combination with the
Nitrous Acid, is a most violent Caustic and Corrosive, becomes so mild
after it, that it may not only be taken internally without danger, but
hath scarce any sensible operation.

The following considerations will lead us to a reasonable explanation
of these phenomena. 1. The Nitrous Acid, when combined with metallic
substances, doth not communicate to them the same volatility as they
acquire from the Marine Acid. Hence it follows, that, if the Nitrous
Acid be added to any combination of a metallic substance with the
Marine Acid, this new compound will be rendered less volatile, and
consequently more able, without rising in vapours, to bear a degree of
heat sufficient to carry off part of its Acid. This is the case with
Butter of Antimony, after Spirit of Nitre is mixed with it; especially
considering, 2. That the Nitrous Acid cannot unite with the reguline
part of the Butter of Antimony without weakening the connection between
it and the Marine Acid; whence it follows, that the combination of the
Nitrous Acid further facilitates the separation of the Marine Acid
from the Regulus. Now as soon as the Marine Acid quits the reguline
part, that part becomes more fixed, and consequently more capable of
enduring the degree of heat requisite to discharge all the adhering
Acid; and not only the Marine, but even the Nitrous also. It is not
therefore surprizing that, after the Antimony which remains combined
with the Nitrous Acid is dried, it should not possess that corrosive
power which it derives only from the Acids wherewith it is armed. In
order to free it more perfectly from all Acid, we order the fire to be
increased after the third desiccation; and the remainder of the Butter
of Antimony to be calcined for a full half-hour longer.

That the Marine Acid is separated from the reguline part of the Butter
of Antimony, by the desiccations it undergoes in converting it into
Bezoar, is proved by this, that, when these desiccations are performed
in close vessels, the liquor drawn off is a true _aqua regis_, known by
the name of the _Bezoartic Spirit of Nitre_.

It remains to be considered why the Bezoar mineral, though freed from
all acid, is not emetic; while the _Pulvis Algaroth_, which is likewise
the reguline part of the Butter of Antimony deprived of its Acid,
is such a violent emetic, and even to be dreaded for its remaining
causticity.

In order to discover the reason of this difference, it is proper to
observe that, when we say Bezoar mineral and the _Pulvis Algaroth_
contain no Acid, we must not be understood in too strict a sense: on
the contrary, there is reason to think that a certain quantity of Acid
still remains in each of them; which however is scarce worth notice,
in comparison of the quantity each contained at first. This being
allowed, it will not be hard to find the difference between these two
preparations of Antimony. The _Pulvis Algaroth_ is deprived of its
Acid by the addition of water alone, which only carries off all the
loose Acid it can take up, without making any change in the nature of
that which continues in combination with the reguline part. Now, as
the Marine Acid is not intimately united with the reguline part in
Butter of Antimony; as it still retains some of its properties, such as
attracting the moisture of the air, giving manifest tokens of its Acid
nature, &c.; and as the corrosive quality of this compound depends on
this last in particular; the small portion of Acid left in the _Pulvis
Algaroth_ will in some degree preserve its former character: and hence
comes the effect of this powder, which still retains a little of the
corrosive quality that belonged to the Butter of Antimony.

But this is not the case with the small remainder of Acid, which
possibly still continues united with the Bezoar mineral prepared as
here directed. This compound hath been exposed to a fire sufficient,
not only to dry it, but even to calcine it. Now fire is capable of
producing great changes in the texture of bodies. It must have forced
off from the Bezoar all the Acid that was not intimately combined
with it; and that part which it could not drive off, because of its
obstinate adhesion, it must have further united and combined more
closely with the metallic earth: for we see that fire greatly promotes
the action of solvents on the matters with which they are united.

With regard to the properly emetic quality of the _Pulvis Algaroth_,
it cannot be imputed to the combination of any Acid with that powder;
since we see that the most powerfully emetic preparations of Antimony,
_viz._ its Regulus and Glass, contain no Acid: it must therefore be
attributed to some cause different from that on which its corrosive
quality depends. This cause we shall easily find by attending to the
different manners in which the Marine Acid, when alone and in _aqua
regia_, operates on the reguline part of Antimony.

The Marine Acid alone dissolves the Regulus of Antimony, but with
great difficulty; nor doth it effect a complete dissolution thereof,
as is evident from what hath been already said: whereas the Marine
Acid, combined with the Nitrous Acid, and therewith forming an _aqua
regis_, as in the preparation of Bezoar, dissolves the reguline part
of Antimony completely and radically. Now, it is certain that, the
more efficaciously Acids operate on metallic substances, the more of
their phlogiston do they destroy; and we cannot but recollect that
the preparations of Antimony are so much the less emetic the less
phlogiston they contain, or the further they recede from the nature
of a Regulus, and the nearer they approach to that of Diaphoretic
Antimony: consequently it is plain how Bezoar mineral, which is a
sort of calx of Antimony entirely deprived of its phlogiston by the
intimate dissolution thereof made by the Acids of the _aqua regis_,
may be in no degree emetic; while the _Pulvis Algaroth_, being a true
Regulus of Antimony, on which the Marine Acid hath operated but very
superficially, and which still contains a great deal of phlogiston, is
a most violent emetic.


PROCESS XIV.

_Flowers of Antimony._

Take an unglazed earthen pot, having an aperture in its side, with a
stopple to shut it close. Set this pot in a furnace, the cavity whereof
it may fit as exactly as possible; and fill up with lute the space,
if any, left between the vessel and the furnace. Over this vessel fix
three aludels, with a blind-head at the top; and light a fire in the
furnace under the pot.

When the bottom of the pot is thoroughly red, throw into the lateral
aperture a small spoonful of powdered Antimony. Stir the matter
immediately with an iron spatula made a little bending, in order to
spread it over the bottom of the vessel, and then stop the hole. The
flowers will rise and adhere to the insides of the aludels. Keep up the
fire so that the bottom of the pot may always continue red; and, when
nothing more sublimes, put in a like quantity of Antimony, and operate
as before. In this manner go on subliming your Antimony, till you have
as many flowers as you want. Then let the fire go out; and when the
vessels are cold unlute them. You will find flowers adhering all round
the insides of the aludels and the head, which you may collect with a
feather.


_OBSERVATIONS._

Antimony is a volatile mineral, capable of being sublimed into flowers;
but this cannot be effected without occasioning a notable change
in its parts. The reguline and the sulphureous parts are not united
so intimately, or in the same proportion, in the flowers as in the
Antimony itself; and accordingly we find these flowers have a strong
emetic quality, which Antimony hath not. They are of divers colours;
which probably arises from their containing more or less Sulphur. Three
or four aludels are placed one over another, not only with a view to
provide a greater surface, to which the flowers may adhere, but also to
give them room enough to circulate, without which they might burst the
vessels.

If you introduce the nosle of a pair of bellows into the pot that
contains the Antimony, and blow upon it, the sublimation of the flowers
will be much sooner effected. This is a general rule with regard to all
matters that are to be sublimed or evaporated; the reason of which we
have already given.

It is proper that no interval be left between the furnace and the pot
containing the Antimony, lest the heat should be thereby communicated
to the aludels, on which the flowers fasten best when they are cold.

After the operation, there remains at the bottom of the pot a portion
of Antimony half calcined; which being pulverized, and thoroughly
calcined till it emit no fume, may be employed to make the Glass of
Antimony.


PROCESS XV.

_Regulus of Antimony converted into Flowers._

Pulverize your Regulus of Antimony: put the powder into an unglazed
earthen pot: three or four fingers breadth above the powder, fit into
the pot a little cover, made of the same earth, and having a small
hole in its middle, so that it may with ease be placed in the pot, and
taken out when there is occasion: cover the mouth of the pot with a
common lid; set it in a furnace, and kindle a fire under it sufficient
to make the bottom of the pot red, and to melt the Regulus. When it
hath been thus kept in fusion for about an hour, let the fire go out,
and the whole cool. Then remove the two covers. You will find adhering
to the surface of the Regulus, which will be in a mass at the bottom
of the pot, white flowers resembling snow, intermixed with beautiful,
brilliant, silver-coloured needles. Take them out, and you will find
them make about one part in sixty-two of the whole Regulus employed.

Put the covers again in their places, and proceed in the same manner
as before; when the vessels are cold you will find half as many more
flowers as you got the first time.

Proceed thus till you have converted all your Regulus into flowers.
This will require a considerable number of sublimations, which, as you
advance, will always yield you a greater portion of flowers; respect,
however, being had to the quantity of Regulus remaining in the pot.


_OBSERVATIONS._

We must here repeat what we said just before, in our observations on
the preceding process; _viz._ that Regulus of Antimony is capable of
being wholly elevated and sublimed by the action of fire; but that it
must at the same time undergo a considerable change and alteration.
These flowers of Regulus of Antimony are very different from every
other Antimonial preparation. They resemble the Pearly Matter in this,
that they cannot be reduced to a Regulus by any means whatever: but
they differ from it, 1. in that they are not fixed; for, when melted
by fire, they fly wholly away in vapours: 2. in that they are capable
of being dissolved by _aqua regis_, much in the same manner as the
Regulus; whereas the Pearly Matter is known to be indissoluble by any
Acid.

As soon as Regulus of Antimony is in fusion, it begins to sublime into
flowers; so that it is needless to apply a greater degree of heat than
is just sufficient to melt it.

A pan of some width is preferable to a crucible for this operation;
because the upper surface of the Regulus melted therein is larger,
and, the larger that surface is, the more considerable is the quantity
sublimed from it.

The two covers which are applied within and over the pot are designed
to check, as much as possible, the dissipation of the melted
Regulus; yet without absolutely excluding the free access of the
air, the concourse of which is useful in all metallic sublimations.
Notwithstanding these precautions, it is impossible to prevent the
escape of some of the Regulus, in vapours that cannot be confined.
Somewhat less than three fourths of the Regulus made use of is nearly
the yield in flowers: the rest evaporates through the interstices left
by the covers, which must not be luted for the reason just assigned.



CHAP. II.

_Of_ BISMUTH.


PROCESS I.

_To extract Bismuth from its Ore._

Break the ore of Bismuth into small pieces, and therewith fill a
crucible either of earth or iron. Set the crucible in a furnace, and
light such a fire that the bits of ore may become moderately red. Stir
the ore from time to time, and, if you perceive it crackle and fly,
keep the crucible covered. At the bottom you will find a button of
Bismuth.


_OBSERVATIONS._

The extraction of Bismuth from its ore requires nothing but simple
fusion, without the addition of any inflammable matter, because it is
naturally possessed of its metalline form. Nor does it require any
flux; because it is very fusible: which allows us to melt it, and
collect it in a mass, without the necessity of fusing likewise the
earthy and stony matters in which it is lodged. These matters remain in
their first state; and the melted Bismuth descends by its gravity to
the bottom of the crucible. No greater degree of heat must be applied,
on this occasion, than is necessary to melt the semi-metal: for, as it
is volatile, part of it would be dissipated; so that much less thereof
would be obtained, if the fire were made too strong, and so much the
less as another portion thereof would be converted into a calx. For the
same reason, the crucible must be taken out of the furnace as soon as
you perceive that all the Bismuth contained in the ore is melted, and
that the button doth not increase.

The ore of Bismuth may also be treated like the ores of Lead and Tin;
that is, it may be reduced into a fine powder, mixed with the black
flux, a little Borax, and Sea-salt; put into a close crucible, and
fused in a melting furnace. In that case you will find a button of
Regulus covered with scoria. By this method rather more Bismuth is
obtained; and it is best to make use of it when the ore is poor,
because, in such a case, none at all would be obtained by the other
process. But here care must be taken to apply at once the degree of
fire necessary to melt the mixture: for, if it remain long in the fire,
much Bismuth will be lost, on account of the great volatility of this
semi-metal, and the facility with which it turns to a calx.

Bismuth is pretty frequently found pure in its earthy and stony
matrices; and when mineralized it is usually so by Arsenic, which,
being still more volatile, flies off in vapours while the ore is
melting, provided it be but in a small quantity: if there be much
of it, and the ore be smelted by fusing it with the black flux, the
Arsenic also is reduced to a Regulus, unites more intimately with the
Bismuth, becomes a little more fixed by that union, and increases the
quantity of the semi-metallic mass found after the fusion.

Though Bismuth be not usually mineralized by Sulphur, that is not
because it is incapable of uniting therewith; for, if equal parts of
Bismuth and Sulphur be melted together, after the fusion the Bismuth
will be found increased near an eighth part, and formed into a mass
disposed in needles much like Antimony.

When we come to treat of the ore of Arsenic, we shall have occasion
to say a good deal more concerning Bismuth and its ore; because these
minerals resemble each other very much.

Mr. Geoffroy, son of the Academician, hath shewn in a Memoir read
before the Academy of Sciences, that there is a great resemblance
between Bismuth and Lead. That Memoir, which contains only the
beginning of Mr. Geoffroy's course of experiments, proves that the
author supports with dignity the glory of his name. It is there
demonstrated, by a very great number of experiments, that fire produces
the same effects on Bismuth as on Lead. This semi-metal is converted
into a calx, into litharge, and into glass, as Lead is; and these
productions have the same properties as the preparations of Lead made
with the same degree of fire. Bismuth is capable of vitrifying all the
imperfect metals, and of carrying them off through the pores of the
crucible. So that Gold and Silver may be purified and cupelled by its
means, as well as with Lead. You may on this occasion turn to what we
have said concerning Lead.


PROCESS II.

_Bismuth dissolved by Acids. Magistery of Bismuth. Sympathetic Ink._

Into a matrass put Bismuth broken into little bits: pour on it,
by little and little, twice as much _aqua fortis_. This Acid will
attack the semi-metal briskly, and dissolve it entirely, with heat,
effervescence, vapours, and puffing up. The solution will be clear and
limpid.


_OBSERVATIONS._

Of all Acids the Nitrous is that which best dissolves Bismuth. It is
not necessary, on this occasion, to place the phial, in which the
dissolution is performed, on a sand-heat, as in most other metallic
dissolutions: on the contrary, care must be taken not to pour on all
the _aqua fortis_ at once; because it operates with so much activity
that the mixture will heave up and run over the vessel.

The bare addition of water is sufficient to precipitate the solution
of Bismuth. If this solution be mixed with a very large proportion
of water, the liquor grows turbid, appears milky, and deposites a
precipitate of a very beautiful white. This is that white which the
ladies use at their toilets.

Water produces this precipitation by weakening the Acid; which probably
is incapable of keeping the Bismuth dissolved, unless it have a certain
degree of strength.

If you would have a Magistery of Bismuth beautifully white, you must
perform the dissolution with an _aqua fortis_ that is not tainted with
any mixture of the Vitriolic Acid; for this gives the precipitate a
dirty white colour, inclining to grey. Several authors advise the use
of a solution of Sea-salt, instead of pure water, for precipitating
the Bismuth, imagining that this Salt will effect a precipitation here
as it does in the cases of Silver and Lead. But Mr. Pott, a German
Chymist, who hath published a long dissertation on Bismuth, pretends,
on the contrary, that neither Sea-salt, nor its Acid, is capable of
precipitating this semi-metal; and that when a precipitation takes
place on mixing them with our solution, it is brought about only by
means of the water in which those substances are diffused.

Bismuth may also be precipitated by the means of Fixed or Volatile
Alkalis; but the precipitate is not of so fine a white as when procured
by the means of pure water only.

If a greater quantity of _aqua fortis_, than that prescribed in the
process, be made use of to dissolve the Bismuth, a great deal more
water will also be required to precipitate the Magistery; because there
will be much more Acid to weaken. This white ought to be well washed,
in order to free it from any remainder of acidity; and it should be
kept in a bottle well stopped; because the access of the air makes it
turn brown, and if any of the Acid be left it will turn it yellow.

A solution of Bismuth prepared with the proper quantity of _aqua
fortis_, that is, with two parts of the Acid to one of the semi-metal,
concretes into little crystals almost as soon as made.

_Aqua fortis_ not only acts on Bismuth when separated from its ore,
and reduced to a Regulus, but attacks it even in its ore, and likewise
dissolves at the same time some portion of the ore itself. With
this solution of the ore of Bismuth Mr. Hellot makes a very curious
Sympathetic Ink, differing from all that were known before.

Mr. Hellot prepares the liquor in the following manner: "He bruises
the ore of Bismuth to a coarse powder. On two ounces of this powder
he pours a mixture of five ounces of common water with five ounces of
_aqua fortis_. He does not heat the vessel till the first ebullitions
are over. He then sets it in a gentle sand-heat, and lets it digest
there till he sees no more air bubbles rise. When none appear in this
heat, he increases it so as to make the solvent boil slightly for a
full quarter of an hour. It takes up a tincture nearly of the colour
of brown beer. The ore that gives the _aqua fortis_ this colour is
the best. He then lets the solution cool, laying the matrass on its
side, that he may decant the liquor more conveniently when all is
precipitated that is not taken up by the solvent.

"The second vessel, into which the liquor is first decanted, he also
lays declining, that a new precipitation of the undissolved matters may
be obtained; after which he pours the liquor into a third vessel. This
liquor must not be filtered, if you would have the rest of the process
succeed perfectly; because the _aqua fortis_ would dissolve some of the
paper, and that would spoil the colour of your paper.

"When this solution, which Mr. Hellot calls the _Impregnation_, is
thoroughly clarified by being decanted three or four times, he puts
it into a glass bason with two ounces of very pure Sea-salt. The fine
white salt made by the sun succeeded best with Mr. Hellot. If that
cannot be had, common bay-salt, purified by solution, filtration,
and crystallization, may be used instead of it. But as it is rare to
meet with any of the sort that is not a little tainted with iron,
the white bay-salt is to be preferred. The glass bason he sets in a
gentle sand-heat, and keeps it there till the mixture be reduced by
evaporation to an almost dry saline mass.

"If you desire to save the _aqua regis_, the impregnation must be put
into a retort, and distilled with the gentle heat of a sand-bath. But
there is an inconveniency, as Mr. Hellot observes, in employing a
retort; which is, that, as the saline mass cannot be stirred while it
coagulates in the retort, it is reduced to a compact cake of coloured
Salt, which presents but one single surface to the water in which it
must be dissolved; so that the dissolution thereof takes up sometimes
no less than five or six days. In the bason, on the contrary, the
saline mass is easily brought to a granulated Salt, by stirring it
with a glass rod; and, when thus granulated, it has a great deal more
surface; it dissolves more easily, and yields its tincture to water
in four hours time. Indeed one is more exposed to the vapours of the
solvent, which would be dangerous, if the operation were to be often
performed, without proper precautions.

"When the bason, or little vessel, containing the mixture of the
Impregnation and Sea-salt is heated, the liquor, which was of an
orange-coloured red, becomes a crimson red; and, when all the phlegm of
the solvent is evaporated, it acquires a beautiful emerald colour. By
degrees it thickens, and acquires the colour of a mass of Verdegris.
It must then be carefully stirred with the glass rod, in order to
granulate the Salt, which must not be kept over the fire till it be
perfectly dry; because you run a risk of losing irrecoverably the
colour you are seeking. You may be sure you have lost it, if by too
much heat the Salt that was of a green colour become of a dirty yellow.
If it be once brought to this state, it will continue without changing
when cold: but if care be taken to remove it from the fire while it
is still green, you will see it gradually grow pale, and become of a
beautiful rose colour as it cools.

"Mr. Hellot removes it from this vessel, and throws it into another
containing distilled rain water: and this second vessel he keeps in
gentle digestion till he observes that the powder which falls to the
bottom is perfectly white. If, after three or four hours digesting,
this powder still continues tinged with a rose colour, it is a proof
that water enough was not added to dissolve all the Salt impregnated
with the tincture of the solution. In this case, the first tinged
liquor must be poured off, and fresh water added, in proportion to the
quantity of tinged Salt, that is supposed to remain mixed with the
precipitate.

"When the ore is pure, and doth not contain a great deal of fusible
stone, commonly called _Fluor_ or _Quartz_, an ounce of it generally
yields tincture enough for eight or nine ounces of water, and the
liquor is of a beautiful colour like that of the lilach or pipe-tree
blossom. In order to prove the effect of this tincture, you must write
with this lilach-coloured liquor on good well-gummed paper, that does
not sink: or you may use it to shade the leaves of some tree or plant,
having first drawn the outlines thereof lightly, with China-ink or
with a black-lead pencil. Let this coloured drawing, or writing, dry
in a warm air. You will perceive no colour while it is cold; but if
it be gently warmed before the fire, you will see the writing, or the
drawing, gradually acquire a blue or greenish-blue colour, which is
visible as long as the paper continues a little warm, and disappears
entirely when it cools."

The singularity of this sympathetic ink consists in its property of
disappearing entirely and becoming invisible, though it be not touched
with any thing whatever: and this distinguishes it from all others;
which, when once rendered visible by the application of proper means,
do not again disappear, or at least not without touching the strokes on
the paper with some other liquor.

Mr. Hellot made a vast variety of experiments on this subject, and gave
his sympathetic ink successively the properties of all others that are
known.

It follows from Mr. Hellot's experiments, that it is the Acid of
Sea-salt which makes this saline _magma_ of a green colour while it
is hot: that without this Acid the saline matter continues red; and
that the solution of Bismuth-ore in _aqua fortis_ may therefore serve
as a touchstone, to discover whether or no any unknown Salt under
examination contains Sea-salt, or a portion of the Marine Acid.

He also proves, in the Memoirs he hath given in on this subject,
that the Nitrous Acid is the true solvent of those ores of Bismuth
which contain moreover Smalt and Arsenic. That Acid dissolves all the
metallic and colouring matters contained in those ores, sparing nothing
but the sulphureous and arsenical portion, the greatest part of which
remains precipitated; and from this colouring matter the sympathetic
ink derives its virtue.

Under the head of Arsenic we shall speak more amply of this matter in
Cobalt, or the ore of Arsenic, that gives a blue colour to the sand
with which it is vitrified.

The Vitriolic Acid does not, properly speaking, dissolve Bismuth. If
to one part and an half of this semi-metal you add one part of Oil of
Vitriol; distil the whole to dryness; and then lixiviate with water
what remains in the retort; the liquor you obtained by this means will
be of a reddish yellow colour, but will let nothing fall when mixed
with an Alkali: and this shews that the Vitriolic Acid acts only upon
the inflammable part of Bismuth, and doth not dissolve its metallic
earth.

It dissolves the ore of Bismuth more perceptibly than Bismuth itself;
because the ore contains, besides the reguline part, an arsenical
matter, and a coloured matter, over which perhaps it hath more power.

The Acid of Sea-salt attacks and dissolves Bismuth in some small
measure, but slowly and with difficulty. That this Acid dissolves a
portion of our semi-metal may be proved, by mixing a Fixed or Volatile
Alkali with Spirit of Salt in which Bismuth hath lain some time
digesting; for then a precipitate falls.

But, though the Marine Acid be capable of dissolving Bismuth, it doth
not follow that it hath a greater affinity than the Nitrous Acid with
this metallic substance, as some Chymists have thought; who imagined
that, in the precipitation of the Magistery of Bismuth by a solution
of Sea-salt, the Acid of that Salt quits its basis to unite with the
Bismuth which it precipitates, as is the case in the precipitations
of Lead and of Silver by the same Salt, and that it forms, on this
occasion, a _Bismuthum corneum_.

On this subject, Mr. Pott observed, 1. that, when only a small quantity
of the solution of Sea-salt is mixed with the solution of Bismuth in
the Nitrous Acid, no precipitate is formed: now it is certain that when
the smallest quantity whatever of Sea-salt is mixed with the solution
either of Lead or of Silver, a precipitate is immediately deposited, in
a quantity proportioned to that of the Salt used.

2. Mr. Pott, having examined the precipitate of Bismuth thrown down
by a solution of Sea-salt, found it not to have the properties of a
metallic substance rendered horny: on the contrary, that precipitate
being exposed to a very violent fire appeared refractory, and could not
be melted.



CHAP. III.

_Of_ ZINC.


PROCESS I.

_To extract Zinc from its Ore, or Calamine._

Take eight parts of Calamine reduced to a powder; mix this powder
accurately with one part of fine charcoal-dust, previously calcined
in a crucible to free it from all moisture: put this mixture into a
stone retort coated with lute, leaving a third part of it empty: set
your retort in a reverberatory furnace, capable of giving a very fierce
heat. To the retort apply a receiver, with a little water in it. Kindle
the fire, and raise it by degrees till the heat be strong enough to
melt Copper. With this degree of fire the Zinc being metallized will
separate from the mixture, and sublime into the neck of the retort,
in the form of metallic drops. Break the retort when it is cold, and
collect the Zinc.


_OBSERVATIONS._

The process here given for smelting Zinc out of Calamine is taken from
the Memoirs of the Academy of Sciences at Berlin. The author of it is
Mr. Marggraff, a skilful Chymist, whom we have already had occasion to
mention under the article of Phosphorus.

Till this process was published, we knew no method of obtaining pure
Zinc directly from the _Lapis Calaminaris_.

Most of the Zinc we have comes from an ore of difficult fusion that is
worked at Goslar, and yields, at one and the same time, Lead, Zinc, and
another metallic matter called _Cadmia Fornacum_, which also contains
much Zinc, as we shall afterwards see.

The furnace used for smelting this ore is closed on its fore-side with
thin plates or tables of stone, not above an inch thick. This stone is
greyish, and bears a violent fire.

In this furnace the ore is melted amidst charcoal, by the help of
bellows. Each melting takes twelve hours, during which time the Zinc
flowing with the Lead is resolved into flowers and vapours, great part
of which adheres to the sides of the furnace in the form of a very hard
crust of earth. The workmen take care to remove this crust from time
to time; for it would otherwise grow so thick at last as to lessen the
cavity of the furnace very considerably.

There adheres moreover to the fore-part of the furnace, which is
formed, as we said before, of thin plates of stone, a metallic matter,
which is the Zinc, and is carefully collected at the end of each
melting, by removing from this part all the live coals. A quantity
of small coal is laid unlighted at the bottom; and on this small
coal, by striking the stone plates gently with a hammer, the Zinc
is made to fall out of the other matter, known by the Latin name
of _Cadmia Fornacum_, among which it appears fixed in a radiated
form. To this other matter we may properly enough give the name of
_Furnace-Calamine_. The Zinc falls in the form of a melted metal, all
on fire, and in a bright flame. It would soon be entirely burnt and
reduced to flowers, as we shall see, if it were not extinguished, and
easily cooled and fixed, by being hid under the unlighted small-coal
placed below on purpose to receive it.

The Zinc adheres to the fore-part of the furnace preferably to any
other, because that being the thinnest is therefore the coolest: and,
in order further to promote its fixing on this part, they take care to
keep the thin stone plates cool during the operation, by throwing water
on them.

Hence it appears, that Zinc is not extracted from its ore by fusion and
the precipitation of a Regulus, like other metallic substances. This is
owing to the great volatility of our semi-metal, which cannot, without
subliming, bear the degree of fire necessary to melt its ore. It is at
the same time so combustible, that a great part of it rises in flowers
which have not the metalline form.

Mr. Marggraff provides against these inconveniences by working the
ore of Zinc in close vessels. By this means he prevents the Zinc from
taking fire, and being converted into flowers; so that it sublimes in
its metalline form. The water in the recipient serves to receive and
cool the drops of Zinc that may be forced quite over the helm. As the
operation requires a most violent fire, these drops must needs issue
exceeding hot, and, without this precaution, break the recipient.

Mr. Marggraff by the same process extracted Zinc out of the
Furnace-Calamine procured from ores containing Zinc; from Tutty, which
is a sort of furnace-calamine; from the flowers and from the calx of
Zinc; and from the precipitate of White Vitriol; all of them matters
known to be Zinc, that wanted nothing but the phlogiston to give it a
semi-metalline form, and from which nevertheless no body could ever
before him procure any Zinc.

Mr. Marggraff observes, that the Zinc obtained by his process bears
being flatted under the hammer into pretty thin plates; which the
common Zinc will not do. The cause of this probably is, that the Zinc
obtained by his method is more intimately combined with the phlogiston,
and contains a greater quantity thereof, than that which is procured in
the ordinary way.


PROCESS II.

_To sublime Zinc into Flowers._

Take a very deep, large crucible: place it in a furnace, so that it may
stand inclining in an angle of forty-five degrees nearly. Throw some
Zinc into it, and kindle a fire in the furnace somewhat stronger than
would be necessary to keep Lead in fusion. The Zinc will melt. Stir it
with an iron wire, and there will appear on its surface a very bright
white flame: two inches above this flame a thick smoke will be formed,
and with this smoke exceeding white Flowers will rise, and remain some
time adhering to the sides of the crucible, in the form of a very fine
light down. When the flame slackens, stir your melted matter again with
the iron wire: you will see the flame renewed, and the flowers begin
again to appear in greater abundance. Go on thus till you observe that
the matter will not flame, nor any more Flowers rise.


_OBSERVATIONS._

Zinc takes fire very easily as soon as it is affected by a certain
degree of heat; which proves, that in the composition of this
semi-metal there is very much phlogiston, united but slightly with
its metallic earth. The Flowers into which Zinc resolves, during its
combustion, are of a perfectly singular nature, and differ greatly from
all the other productions obtainable out of metallic substances.

They may be considered as the very calx of Zinc, or its metallic earth
robbed of its phlogiston, and sublimed during the combustion of this
semi-metal, being probably carried up by the phlogiston in flying off.
For these Flowers, when once sublimed, are afterwards exceedingly
fixed: they sustain the greatest violence of fire without rising, and
are converted by it into a sort of glass.

None of the methods hitherto employed, for restoring to the Flowers
of Zinc their metalline form, have ever succeeded. When treated like
other metalline calces in a crucible, with every kind of inflammable
matter, and different sorts of reducing fluxes, they never can be
re-metallized: they only melt with the flux, and produce a kind of
Glass.

Mr. Marggraff indeed, as mentioned before, obtained Zinc from these
Flowers, by treating them as he did Calamine in a retort with
charcoal-dust: but as the Flowers often carry up with them little
particles of undecomposed Zinc, there still remains some doubt
concerning the reduction of these Flowers, even by this method.

If the crucible, into which you put the Zinc to be converted into
Flowers, instead of being left open, as directed, be covered with
another crucible inverted, the two vessels luted together, placed in
a melting furnace, and a strong fire immediately kindled and kept up
for about half an hour; you will find, when the vessels are cold, that
all the Zinc hath left the lower crucible, and is sublimed into the
upper one, in its metalline form, without suffering any decomposition.
This experiment proves, that Zinc, to be converted into Flowers, must
necessarily be set on fire and burnt. As it cannot burn in close
vessels, any more than other combustible bodies, and as it is volatile,
it sublimes without suffering any decomposition. Regulus of Antimony
and Bismuth may be sublimed in the same manner; but not so easily as
Zinc, which is still more volatile than those other semi-metals.

It is necessary to stir the Zinc in fusion from time to time with
an iron wire, when you intend to convert it into Flowers: for there
forms on its surface a grey crust that obstructs its deflagration,
and beneath which it is gradually converted into a clotted calx. In
order, therefore, to promote the rising of the flowers, care must be
taken to break this crust, as oft as it begins to form. On this there
immediately appears a very bright white flame: two inches above the
flame is seen a thick smoke, and with this smoke very white Flowers
rise, that continue some time adhering to the inside of the crucible,
in the form of a fine down.

M. Malouin, who, in sundry Memoirs on Zinc, hath endeavoured to
discover what resemblance there is between this semi-metal and Tin,
tried to calcine Zinc in the same manner as Tin; but found it somewhat
more difficult. Zinc, while it is not in fusion, doth not calcine; but
it begins to turn to a calx the moment it begins to melt. M. Malouin,
having repeated the fusion of Zinc a great number of times, by that
means collected at last a quantity of the calx of this semi-metal,
resembling other metalline calces. This calx of Zinc he melted in
a crucible with animal fat; whereby the calx was re-metallized, and
reduced to Zinc. There is great reason to believe that the calx of Zinc
made by this method is not so much burnt as the Flowers, and that it
still contains a portion of phlogiston.


PROCESS III.

_To combine Zinc with Copper. Brass. Prince's Metal_, &c.

Pound one part and an half of Calamine, and an equal quantity of
charcoal: mingle these two powders together, and moisten them with a
little water. Put this mixture into a large crucible, or some other
earthen vessel that will bear a melting heat. Amongst and over this
mixture put one part of very pure Copper in thin plates, and then put
fresh charcoal-dust over all: cover the crucible; set it in a melting
furnace; put coals all round it, and let them kindle gradually. Raise
the fire so as to make the crucible very red-hot. When you observe
that the flame hath acquired a purple or bluish-green colour, uncover
the crucible, and dip into it an iron wire, to examine whether or no
the copper be in fusion under the charcoal-dust. If you find it is,
moderate the force of the fire a little, and let your crucible remain
in the furnace for a few minutes. Then take it out and let it cool: you
will find your Copper of a gold colour, increased in weight a fourth,
or perhaps a third part, and yet very malleable.


_OBSERVATIONS._

The _Lapis Calaminaris_ is not the only substance with which Copper
may be converted into brass: all other ores containing Zinc, the
Furnace-Calamine that sublimes where such ores are worked, Tutty, Zinc
in substance, may be substituted for it, and, like it, will make very
fine Brass; but, in order to succeed, sundry precautions are necessary
which we shall now lay before you.

This process is a sort of cementation: for the Calamine doth not melt;
only the Zinc is converted into vapours, and then combines with the
Copper. On this the success of the operation partly depends, as it
is the means of the Copper's preserving its purity and malleability;
because the other metallic substances that may be united with the ore
of Zinc, or with the Zinc itself, not having the same volatility,
cannot be reduced to vapours. If you are apprised that the Calamine,
or other ore of Zinc used on this occasion, is contaminated with a
mixture of any other metallic matter, you must mingle luting earth
with the charcoal-dust and the matter containing the Zinc; make it
into stiff paste with water; of this make a bed at the bottom of your
crucible, and ram it hard down; lay the Copper plates thereon, cover
them with charcoal-dust, and then proceed as before. By this means when
the Copper melts it cannot fall to the bottom of the crucible, nor mix
with the ore; but is borne up by the mixture, and cannot combine with
any thing but the Zinc, that rises in vapours, and, passing through the
lute, fixes in the Copper.

_Lapis Calaminaris_, or other ore of Zinc, may also be purified before
it be used for making Brass; especially if adulterated with Lead ore,
which is often the case. For this purpose the ore must be roasted in
a fire strong enough to give a small degree of fusion to the leaden
matter; which will thereby be reduced into larger, heavier, and tougher
masses. The most subtile particles are dissipated in the torrefaction,
together with some of the Calamine. The Calamine, on the contrary, is
by roasting made more tender, lighter, and much more friable. When it
is in this condition, put it into a washing tray or van; dip the tray
in a vessel full of water, and bruise the matter it contains. The water
will carry off the lightest powder, which is the Calamine, and leave
nothing at the bottom of the tray but the heaviest substance; that is
the leaden matter, which is to be rejected as useless. The powder of
the Calamine will settle at the bottom of the vessel, where, after
pouring off the water, it may be found, and used as above directed.

In this operation the charcoal-dust serves to prevent both the Copper
and the Zinc from being calcined: and for this reason, when you work
on a great quantity of materials at once, it is not necessary to use
so much charcoal-dust, in proportion, as when you work but on a small
quantity; because, the greater the mass of metal, the less easily will
it calcine.

Though the Copper melts in this operation, yet it is far from being
necessary to apply such a strong fire as Copper usually requires to
melt it: for the accession of the Zinc, on this occasion, communicates
to it a great deal of fusibility. The increase of its weight is also
owing to the quantity of Zinc combined with it. Copper acquires still
another advantage by its association with this semi-metal; for it
remains longer in the fire without calcining.

Brass well prepared ought to be malleable when cold. But in whatever
manner it be made, and whatever proportion of Zinc there be in it, it
is constantly found quite unmalleable when red-hot.

Brass melted in a crucible, with a fierce heat, takes fire almost like
Zinc, and from its surface many white flowers ascend, dancing about
in flakes like the flowers of Zinc. They are indeed the flowers of
Zinc, and the flame of Brass urged by a strong fire is no other than
the flame of the Zinc that is united with the Copper, and at that
time burns. If Brass be thus kept long in fusion it will lose almost
all the Zinc it contains. It will also lose much of its weight, and
its colour will be nearly that of Copper. It is therefore necessary,
towards performing this operation aright, to seize the moment when the
Copper is sufficiently impregnated with Zinc, when it hath acquired
the most weight and the finest colour, with the least detriment to its
ductility, that is possible, and that instant to put out the fire;
because, if the Copper be left longer in fusion, it will only lose
the Zinc already united with it. Skill acquired by much practice, and
an acquaintance with the particular Calamine employed, are necessary
to guide the artist surely through this operation; for there are very
considerable differences between the sundry ores of Zinc. Some of them
contain Lead, as was said above, and in others there is Iron. When
these heterogeneous metals come to be mixed with the Copper, they do
indeed augment its weight, but they render it at the same time pale,
and make it very harsh. Some Calamines require to be roasted before
they can be used for this purpose, and in the torrefaction emit vapours
of a Volatile Alkali, succeeded by vapours of a Sulphureous Spirit:
others exhale no vapours while roasting, and may be employed without
any antecedent preparation. These different qualities must evidently
produce great differences in the operation.

Brass may also be made as Prince's metal and other imitations of Gold
are actually made, by using Zinc in substance, instead of the ores that
contain it. But these compositions have not, when cold, the ductility
of Brass prepared with _Lapis Calaminaris_, because Zinc is seldom
pure, or free from a mixture of Lead. Perhaps also the different
manner in which the Zinc unites with the Copper may contribute to this
variation.

To obviate this inconvenience, the Zinc must be refined from all alloy
of Lead. The property of being indissoluble by Sulphur, which this
semi-metal possesses, points out a very practicable method of doing
it. The Zinc must be melted in a crucible, and stirred briskly with
a strong iron wire, while tallow and mineral Sulphur are alternately
projected upon it; but so that the quantity of Sulphur may greatly
exceed that of the tallow. If the Sulphur do not burn entirely away,
but form a kind of scoria on the surface of the Zinc, it is a sign
that your semi-metal contains Lead. In this case you must continue
throwing in more Sulphur, and keep stirring the Zinc incessantly, till
you perceive that the Sulphur ceases to unite any more with a metallic
substance, but burns freely on the surface of the Zinc. The semi-metal
is then refined, because the Sulphur, which cannot dissolve it, unites
very readily with the Lead, or other metallic substance, contained in
it.

If Zinc thus refined be mixed with pure Copper, in the proportion
of a fourth or a third part, and the mixture be kept in fusion and
constantly stirring for some time, the Brass produced will be as
ductile, when cold, as that made by cementation with the _Lapis
Calaminaris_.

With regard to Prince's metal, and other imitations of Gold, they are
made either with Copper or Brass re-combined with more Zinc. As it is
necessary, for giving them a fine golden colour, to mix with them other
proportions of Zinc than that acquired to make Brass only, they are
generally much less ductile. In 1725, M. Geoffroy gave a Memoir on this
subject in which he examined the effects of incorporating both Copper
and Brass with Zinc, from a small to a very large quantity.


PROCESS IV.

_Zinc dissolved in the Mineral Acids_.

Weaken concentrated Oil of Vitriol by mixing with it an equal quantity
of water. Into a matrass put the Zinc you intend to dissolve, first
broken to small pieces. Pour on it six times its weight of the
Vitriolic Acid, lowered as above directed, and set the matrass in a
sand-bath gently heated. The Zinc will dissolve entirely, without any
sediment. The Neutral Metallic Salt resulting from this dissolution
shoots into crystals, which go by the name of _White Vitriol_, or
_Vitriol of Zinc_.


_OBSERVATIONS_.

Though Zinc be soluble in all the Acids, and when combined with
those Acids exhibits some uncommon phenomena, yet M. Hellot is the
first that ever gave a particular account of what happens in those
dissolutions: so that all we have to say on this head is extracted
from that Gentleman's Memoirs. If a solution of Zinc in the Vitriolic
Acid, prepared according to the directions in the process, be
distilled from a retort placed in a sand-bath with a graduated heat,
almost half the liquor presently comes over in pure phlegm. A small
quantity of a Sulphureous Acid Spirit rises next. A greater force of
fire is now requisite: the retort must therefore be removed into a
reverberatory, and the distillation continued with a naked fire. On the
first impression of this heat an odour of Liver of Sulphur discovers
itself, which becomes sharp and suffocating towards the end of the
distillation. In two hours time white vapours begin to appear, as in
the rectification of common Oil of Vitriol. If the receiver be then
shifted, you will obtain an Oil of Vitriol, in quantity about the
eighteenth part of the whole used in the distillation, which, though
sulphureous, is yet so concentrated, that, if a few drops thereof be
poured into a weak Oil of Vitriol, they fall to the bottom with as much
noise as if they were so many bits of red-hot iron, and heat this Oil
of Vitriol as much as common Oil of Vitriol heats water.

At the bottom of the retort there remains a dry, white, crystalline,
saline mass, exceeding in weight the Zinc that was dissolved, about
a twelfth part of the whole weight of the liquor. The increase of
its weight is owing to a portion of the Vitriolic Acid that remains
concentrated in the Zinc, and could not be expelled by the fire. This
portion of Acid adheres to it most tenaciously: for, though M. Hellot
kept the retort containing it during two whole hours in so violent a
fire that the vessel began to melt, the smallest vapour did not rise
from it.

This saline _caput mortuum_ is in the form of needles, much like
the Sedative Salt. It is caustic, grows considerably hot when water
is poured on it, and gives in the air, but slowly. Spirit of wine,
digested with this Salt for eight or ten days, acquires the same smell
as that which is mixed with concentrated Oil of Vitriol in preparing
Æther.

Zinc is dissolved by the Nitrous and Marine Acids, much in the same
manner as by the Vitriolic; except that the Marine Acid does not touch
a black, spungy, rarefied matter, which it separates from the Zinc. M.
Hellot found upon trial that this matter is not Mercury, and that it
cannot be reduced to a metallic substance.

That ingenious Chymist distilled likewise Solutions of Zinc in the
Nitrous and Marine Acids. There came over at first, as there did from
the solution made by the Vitriolic Acid, an aqueous, and then an
acidulated liquor. At last, by exciting the fire with great violence,
towards the end of the distillation, he obtained a small quantity of
the Acid that hath been employed in the dissolution: but the small
portion of Acid thus obtained was exceeding strong; and the quantity of
the Nitrous much more considerable than that of the Marine Acid.

A solution of Zinc in the Marine Acid, being distilled to dryness,
yields a Sublimate on applying a violent heat to it.

All the Acids dissolve with ease, not only Zinc, but its Flowers
also; and that nearly in the same quantity, and with almost all the
same phenomena. M. Hellot, observing that the residues of most of the
solutions of Zinc have a great resemblance with its flowers, is of
opinion that this semi-metal may be reduced, by the means of solvents,
to the same state into which it is brought by the fire when sublimed in
Flowers.



CHAP. IV.

_Of_ ARSENIC.


PROCESS I.

_To extract Arsenic from its Matrices. Zaffre or Smalt._

Powder some Cobalt, white Pyrites, or other Arsenical matters. Put
this powder into a retort with a short wide neck, leaving a full third
thereof empty. Set your retort in a reverberating furnace; lute on a
receiver; heat your vessel by degrees, and increase the fire till you
see a powder sublime into the neck of the retort. Keep up the fire in
this degree as long as the sublimation continues: when this begins
to slacken, raise your fire, and make it as strong as the vessels
will bear. When nothing more ascends, let it go out. On unluting the
vessels, you will find in the receiver a little Arsenic in the form of
a fine light _farina_. The neck of the retort will be full of white
flowers, not quite so fine, some of which will appear like little
crystals; and if a good deal of Arsenic be sublimed, a ponderous
matter, like a white, semi-transparent glass, will be found adhering to
that part of the neck of the retort which is next its body.


_OBSERVATIONS._

Arsenic is a metallic substance still more volatile than Zinc; so
that it cannot be separated from the matters with which it is mixed
otherwise than by sublimation. It is proper, however, to take notice,
that it is not naturally in a metallic form, and that, properly
speaking, the whole Sublimate obtained from Cobalt, as above directed,
is nothing but a metallic calx, that cannot be brought to the form and
gloss of a metal, till it be worked up with fatty matters, as we shall
shew in its place.

This calx is of a very singular nature, and differs from every other
metallic calx, in that this is volatile, and all the rest extremely
fixed; even those procured from the semi-metals: for the Flowers of
Zinc, which are justly considered as a calcined Zinc, though obtained
by a sort of sublimation, are not for all that of a volatile nature,
but rather exceedingly fixed; seeing they are capable of sustaining
the most violent fire, and melt instead of subliming. Arsenic, on the
contrary, is not only extracted from its ore by sublimation, but when
once sublimed continues to be volatile, and flies off in vapours as
soon as it is exposed even to a moderate degree of heat.

This metallic matter, before it is combined with the phlogiston, is
called _White Arsenic_, or plain _Arsenic_: it acquires the title
of _Regulus of Arsenic_ when it is united with the phlogiston, and
glitters like a metal.

Though Arsenic be volatile, yet it requires a pretty strong fire to
separate it from the minerals containing it, especially in close
vessels; because it adheres very close to earthy and vitrifiable
matters. This adhesion is so firm, that, when thus combined, it is
capable of bearing a melting heat, and vitrifies with metallic calces,
and other fusible matters. On this account it is impossible to extract
from Cobalt, or other Arsenical matters, all the Arsenic they contain
by working them only in close vessels. If such matters are to be
freed from all their Arsenic, you must, after you have extracted all
they will yield by distillation, put them into a crucible, and set
it uncovered in the midst of a strong fire. Many Arsenical vapours
will still rise; and care must be taken to stir the contents of the
crucible frequently with an iron rod, to facilitate the discharge of
the remaining Arsenic.

It often happens that the Arsenic, obtained from minerals by
sublimation, is not very white, but of a lighter or darker grey colour.
This is owing to some particles of inflammable matter, from which
Arsenical minerals are seldom quite free. A very small quantity of
phlogiston is sufficient to deprive much Arsenic of its whiteness,
and to give it a grey colour. But when fouled in this manner, it may
easily be brought to its due degree of whiteness: it need only be
sublimed once more, after mixing it with some substance on which it
doth not act; Sea-salt, for instance. If the matters from which Arsenic
is extracted contain Sulphur also, as some pyrites do, the Arsenic
sublimes with much less heat, than when it is united with earthy
matters only; because it combines with the Sulphur, wherewith it hath
a great affinity, and the Sulphur serves to separate the Arsenic, by
this interposition, from the earth. In consequence hereof, Sulphur may
be employed to extract Arsenic out of the earths in which it is fixed.
In this case, the Sulphur changes the colour of the Arsenic, which it
makes of a lighter or deeper yellow, or even red, in proportion to the
quantity there is of it, and to the degree of fire that hath acted on
both together.

The consistence of Arsenic is different, according to the degree of
heat applied in subliming it. If the Arsenical vapour meet with a cold
place, it gathers there in the form of a powder, as the Flowers of
Sulphur do: this is the case with that which falls into the receiver in
distilling it. But if it be stopped in a hot place, and cannot escape
from that heat, it condenses into a heavy, compact, semi-transparent
body, having undergone the first degree of fusion.

Yet it cannot be perfectly melted, so as to flow like other fused
matters: not that it is refractory; for, on the contrary, the degree of
heat in which it begins to melt is very moderate, and it is in its own
nature very fit to promote the fusion of refractory matters: but the
reason is this; it is necessarily converted into vapours by the degree
of heat necessary to fuse it, and these vapours burst the vessels, if
they find no vent.

Arsenic made yellow by a mixture of Sulphur, which is also called
_Orpiment_, is reducible to the form of a solid Sublimate with more
ease; because it is alloyed with a twentieth, or perhaps a tenth part,
of its weight of Sulphur, which renders it more fusible.

Red Arsenic, which contains still more Sulphur, melts also more easily.
It then becomes of a transparent red, like a ruby: and hence, when it
is in this form, it is called _Ruby of Arsenic_.

When a combination of Sulphur and Arsenic is wanted, it is better
to mingle and distil together such minerals as contain Sulphur and
Arsenic, the white and the yellow pyrites, for instance, than to mingle
pure Arsenic with pure Sulphur: for the great volatility of these two
substances is a hindrance to their uniting; whereas, when combined with
other matters, they are capable of sustaining a much greater degree of
heat, which favours and promotes their union.

Those who work by the grate do not extract Arsenic out of Cobalt by
distillation: they throw the ore mixed promiscuously with wood and
charcoal into a great furnace, from whence a flue carries the vapours
into a long winding passage, across which beams of wood are fixed at
proper distances from each other. The Arsenical vapours being conducted
into this passage, adhere both to the sides thereof and to the joists
that lye across it. The fuliginous parts of the combustible matters
being lighter ascend higher, and go out through a chimney at the
farther end of this passage.

The Arsenic sublimed by this method is not white, but of a grey colour;
owing to the inflammable matter of the wood and charcoal with which the
ore is torrefied.

When all the Arsenic the Cobalt will yield is thus separated, the
earthy fixed matter left behind is mixed with divers fusible matters
and vitrified, and produces a glass of a beautiful blue colour. It is
called _Smalt_. This glass is to be prepared in the following manner.

Take four parts of fine fusible sand, an equal quantity of any Fixed
Alkali perfectly depurated, and one part of Cobalt from which the
Arsenic hath been sublimed by torrefaction. Pulverize these different
substances very finely, and mix them thoroughly together; put the
mixture into a good crucible, cover it, and set it in a melting
furnace. Make a strong fire, and keep it up constantly in the same
degree for some hours. Then dip an iron wire into the crucible; to the
end of which a glassy matter will stick, in the form of threads, if the
fusion and vitrification be perfect. In this case take the crucible out
of the fire; cool it by throwing water on it, and then break it. You
will find in it a glass, which will be of an exceeding deep blue, and
almost black, if the operation hath succeeded. This glass, when reduced
to a fine powder, acquires a much brighter and more lively blue colour.

If you find after the operation that the glass hath too little colour,
the fusion must be repeated a second time, with twice or thrice the
quantity of Cobalt. If, on the contrary, the glass be too dark, less
Cobalt must be used.

Instead of the mixture here prescribed you may employ a ready-made
glass, providing it be white and fusible. But as glass is always
hard to melt, and as the mixing Cobalt with it renders it still more
refractory, therefore though an Alkaline Salt be one of the ingredients
in its composition, it is proper to promote the fusion, by mixing
therewith calcined wine-lees, in the quantity of one third part of the
weight of the Cobalt.

In order to make the assay of a particular Cobalt, with a view to know
what quantity of blue glass it will yield, it is necessary to perform
the operation in the manner here set down; a great deal of time and
trouble may be saved by melting one part of Cobalt with two or three
parts of Borax. This Salt is very fusible, and turns, when melted, into
a substance which, for a time, possesses all the properties of glass.
In this trial the glass of Borax will be nearly of the same colour as
the true glass, or Smalt, made with the same Cobalt.

The ores of Bismuth, as well as Cobalt, yield a matter that colours
glass blue; nay, the Smalt made with these ores is more beautiful than
that procured from the ore of pure Arsenic. Some Cobalts yield both
Arsenic and Bismuth. When such Cobalts are used, it is common to find
at the bottom of the crucible a little button of metallic matter, which
is called _Regulus of Cobalt_. This Regulus is a sort of Bismuth,
generally adulterated with a mixture of ferruginous and arsenical parts.

The heaviest and most fixed Flowers of Arsenic, procured from Cobalt,
have likewise the property of giving a blue colour to glass. But this
colour is faint: it is owing to a portion of the colouring matter
carried up along with the Arsenic. These Flowers may be made an
ingredient in the composition of blue glass, not only because of the
colouring principle they contain, but also because they greatly promote
fusion; Arsenic being one of the most efficacious fluxes known.

In short, all those blue glasses, or Smalts, contain a certain quantity
of Arsenic; for a portion of this semi-metal always remains united with
the fixed matter of the Cobalt, though roasted for a long time, and in
a very hot fire. The portion of Arsenic that is thus fixed vitrifies
with the colouring matter, and enters into the composition of the Smalt.

The blue glass made with the fixed part of Cobalt hath several names,
according to the condition in which it is. When it hath undergone the
first imperfect degree of fusion only it is called _Zaffre_. It takes
the name of _Smalt_ when perfectly vitrified: and this again being
pulverized is called _Powder-blue_, or, if finely levigated, _Blue
Enamel_; because it is used in enamelling, as well as in painting
earthen ware and porcelain.


PROCESS II.

_To separate Arsenic from Sulphur._

Powder the yellow or red Arsenic which you intend to separate from
its Sulphur. Moisten this powder with a Fixed Alkali resolved into a
liquor. Dry the mixture gently; put it into a very tall glass cucurbit,
and fit on a blind-head. Set this cucurbit in a sand-bath; warm the
vessels gently, and increase the fire by degrees, till you perceive
that no more Arsenic sublimes. The Arsenic, which before was yellow
or red, rises into the head partly in white flowers, and partly in a
compact, white, semi-transparent matter, which looks as if it were
vitrified. The Sulphur combined with the Fixed Alkali remains at the
bottom of the cucurbit.


_OBSERVATIONS._

A Fixed Alkali hath more affinity than any metallic substance with
Sulphur: so that it is not surprising Sulphur should be separated from
Arsenic by its interposition. Yet there is an inconvenience attends the
use of it: for it hath a great affinity with the Arsenic also, and so
always retains some part thereof, which continues fixed with it. For
this reason care should be taken not to mix, with sulphurated Arsenic,
a greater quantity of Alkali than is necessary to absorb the Sulphur
it contains. Nothing, however, but experience and repeated trials
can teach us the exact quantity of Alkali that ought to be employed;
because the quantity of Sulphur that may be contained in yellow or red
Arsenic is indefinite.

The vessel ought to be tall, that the upper part of the head, where the
Arsenical particles condense, may be the less exposed to heat. Towards
the end of the operation the fire must be strongly excited, so as to
make the sand red-hot; because the last portions of Arsenic that rise
are strongly retained by the Fixed Alkali.

Arsenic that is grey or blackish may be depurated and whitened by the
same means; because a Fixed Alkali absorbs the phlogiston likewise with
great avidity. Mercury, as well as a Fixed Alkali, is an excellent
additament for separating Arsenic from Sulphur. If you will use it for
that purpose, reduce the sulphurated Arsenic to a very fine powder, by
rubbing it a long time in a glass mortar; when it is well pulverized,
let a few drops of Mercury fall upon it, by squeezing it through
chamoy, and continue the trituration. The yellow or red colour of
the Arsenic will insensibly change, and gradually grow darker as the
Mercury incorporates with it. When the Mercury is perfectly killed,
add a little more of it than you did the first time, and in the same
manner: continue to triturate till it disappear; and thus go on adding
more and more till the Mercury you add remain quick, and you can kill
no more of it. Neither the red nor the yellow colour will then appear
in the mixture; which will be grey, if it contain but a little Sulphur,
and black, if a great deal.

Put this mixture into a very tall glass cucurbit; fit on a blind-head;
set it in a sand-bath, and bury it in the sand as far as the contained
mixture reaches. Heat the vessels, and, during the whole operation,
keep up a degree of fire a little weaker than that required for
subliming Cinabar. White Arsenical Flowers will adhere to the upper
part of the head, amongst which will be some beautiful crystals of
Arsenic; and underneath them you will find some Cinabar sublimed, but
not entirely free from Arsenic. If you desire to have your Cinabar and
your Arsenic purer, and more unmixed with each other, separate the
upper sublimate, which is Arsenical, from the lower, which consists
chiefly of Cinabar. Powder each of them coarsely, and sublime them
separately each in a different cucurbit.

On this occasion the Mercury separates the Sulphur from the Arsenic,
because it hath a greater affinity than Arsenic with that mineral. It
is not the only metallic substance of this character: for, as hath
been shewn, there are several others that have a greater affinity
than Mercury with Sulphur, being able to decompose Cinabar by their
interposition. Yet those metallic substances must not be substituted
for Mercury in the present operation: because there is none of them
but hath at the same time a very great affinity with Arsenic, or even
as strong an one as they have with Sulphur; whereas Mercury will by no
means unite with Arsenic.

This method of separating Arsenic from Sulphur hath two advantages over
that in which a Fixed Alkali is the medium. The first is, that by this
means all the Arsenic contained in the mixture is extracted out of it;
and the second, that, as Mercury doth not absorb Arsenic, we are not
put to the trouble of groping out, as it were, by trials the quantity
necessary to be added; and that, though more be added than is necessary
to absorb all the Sulphur, it will be of no prejudice to the operation.
But then it is attended with the inconvenience of being much more
tedious and more laborious than the other. For, in the first place, it
requires previously a very tiresome trituration, in order to procure an
union between the Sulphur and the Mercury, and so to form an Æthiops;
without which the Mercury and the sulphurated Arsenic will sublime
separately, so that no decomposition will be effected. Secondly, though
the Mercury be sufficiently united with the Sulphur of the Arsenic
by the long trituration that precedes the sublimation, this doth not
prevent, as we took notice above, the sublimed Arsenic and Cinabar
from being in some measure blended together; so that each requires a
second separate sublimation to render it very pure.

These inconveniencies cause a Fixed Alkali to be used preferably to
Mercury; the loss of a small quantity of the Arsenic, which remains
united with the Alkali, being little regarded; as that metallic
substance is neither scarce nor precious.

When Arsenic is united with a great quantity of Sulphur, it may be
freed from a part thereof without the intervention of any third body:
it is sufficient for the purpose to sublime it with a very gentle fire,
increased by insensible degrees. The most sulphureous part ascends
first; what rises afterwards is more Arsenical, and less sulphureous;
and the last flowers of all are pure Arsenic, or at least nearly so.


PROCESS III.

_To give Arsenic the Metalline Form. Regulus of Arsenic._

Take two parts of white Arsenic in fine powder, one part of the black
flux, half a part of Borax, and as much clean iron filings. Rub the
whole together, in order to mix them thoroughly. Put this mixture into
a good crucible, and over it put Sea-salt three fingers thick. Cover
the crucible; set it in a melting furnace; and begin with a gentle fire
to heat the crucible equally.

When arsenical vapours begin to ascend from the crucible, raise the
fire immediately so as to melt the mixture. Examine whether or no the
matter be thoroughly melted, by introducing an iron wire into the
crucible; and if the fusion be perfect, take the crucible out of the
furnace. Let it cool; break it; and you will find in it a Regulus of
a white and livid metallic colour, very brittle, scarcely hard, but
rather friable.


_OBSERVATIONS._

White Arsenic is, as hath been said, a metallic calx; and consequently
wants no more, in order to its acquiring the metalline properties, than
to be combined with the phlogiston: this is effected by the operation
before us.

The Iron added doth not serve here, as in making the Regulus of
Antimony, to precipitate the Regulus of Arsenic, by separating it from
some other substance with which it was united: on this occasion it does
nothing but join the Regulus of Arsenic, to which it gives solidity and
consistence. This is the only reason of its being made an ingredient
in the mixture; as the Regulus of Arsenic, without it, would have such
a tender consistence, that it could scarce be handled without falling
asunder into little bits. The Iron procures a further advantage in this
process; which is, that it prevents a great quantity of Arsenic from
being lost in vapours: for the Arsenic, with which it combines, is
restrained, and, in some measure, fixed by it.

Copper may be substituted for Iron, and procures the same advantages.

It is very necessary to remove the crucible from the fire as soon
as the matter is melted, and indeed to cool it as expeditiously as
possible, to prevent the Arsenic from flying off in vapours: for, when
once the Regulus is formed, the proportion of Arsenic, with respect
to that of the metal mixed with it, is continually lessening while it
stays in the fire; so that, after some time, there will be left in the
crucible, not a Regulus of Arsenic, but only Iron or Copper, alloyed
with a little Arsenic. On this occasion the Copper turns white, and
assumes the colour of Silver; but it soon tarnishes in the air.

It is easy to perceive, by what hath been said, that the Regulus of
Arsenic made according to this process is never pure, but contains
always a considerable quantity of Iron or Copper, whatever precautions
be used: but it is difficult to avoid this inconvenience, for the
reasons above assigned; and if we attempt to fuse Arsenic alone, with
reducing fluxes, the greatest part thereof is dissipated in vapours,
long before the very flux begins to melt: and that part of it, which
is found metallized, is not collected in one mass at the bottom of the
crucible, as in other metallic reductions; but in small particles,
dispersed and mixed among the scoriæ. There are nevertheless several
expedients for obtaining a Regulus of Arsenic absolutely pure, and
unalloyed with any metallic substance.

First: into a little low cucurbit, covered with a blind-head, put
Regulus of Arsenic made with Iron or Copper; set this cucurbit in a
sand-bath; heat it till the sand begins to grow red, and you will
see part of the Regulus sublime into the head, still retaining
its metalline splendour. The portion of Regulus thus sublimed is
pure Arsenic, or at least contains but a very small portion of the
adventitious metal, which may have been carried up with it. What is
left in the bottom of the cucurbit is the metal that was added, still
containing a little Arsenic, which continues obstinately fixed with it,
and which the violence of fire is unable to force away from it in close
vessels.

Secondly: mix your Arsenic in equal parts with the black flux; put
the mixture into such a cucurbit as that last mentioned; and apply to
it the strongest degree of heat that can be procured by a sand-bath;
arsenical flowers, of a blackish grey colour, will first sublime into
the head, and after them a Regulus of Arsenic of a white metalline
colour, which is pretty glossy, but tarnishes very soon in the air.
This Regulus hath no solidity: it is exceedingly friable; but it is
pure.

Thirdly: I have also made a Regulus of pure Arsenic by another method,
which produces a much greater quantity thereof, with a much smaller
degree of heat. For this purpose I powder the Arsenic, and mix with it
any Fat Oil; so that the mixture may be like a liquid paste: this paste
I put into a little phial of thin glass, like one of those used by
apothecaries; I set this phial in a sand-bath, and gradually heat it,
till the bottom of the pot containing the sand begin to be red. Part of
the Oil first rises out of the phial in vapours, which must be suffered
to pass off. After this the upper part of the phial is gradually lined,
on the inside, with a glittering metallic crust, which makes it look
like a quick-silvered glass. This crust is the Regulus of Arsenic. When
it begins to sublime, the mouth of the phial must be slightly stopped
with a bit of paper, and the heat increased a little, till you see that
nothing more rises.

If you break the bottle after the operation, you will find its upper
part crusted over with a coat of Regulus, thicker or thinner in
proportion to the quantity of Arsenic employed. The Regulus is in a
mass, of a beautiful brilliant colour, which to me seems to stand the
air better than that of any Regulus made by other methods; probably
because of the great quantity of fat matter with which it is united,
and by which it is defended.

This Regulus of Arsenic is absolutely pure, and a much greater quantity
thereof is obtained, by this method, than by treating it with the black
flux; because the Arsenic is much sooner and more easily combined
with the inflammable matter: and hence it comes to pass that part of
the Arsenic doth not rise at first in grey flowers, as in operating
with the black flux. Moreover, by our process, all the Arsenic is
sublimed in Regulus: whereas, when the black flux is employed, a pretty
considerable part of the Arsenic unites with the alkaline part of the
flux, and remains fixed therewith. In our operation there is nothing
left at the bottom of the phial, except an oily, light, but very fixed
coal.

Regulus of Arsenic, in whatever manner made, may be easily reduced
into white, crystalline Arsenic, by the means of a Fixed Alkali, or
of Mercury, applied in the same manner as for separating Arsenic from
Sulphur.


PROCESS IV.

_To distil the Nitrous Acid by the interposition of Arsenic. Blue_ Aqua
Fortis. _A new Neutral Salt of Arsenic._

Pulverize finely any quantity you please of refined Salt-petre. Mix
it accurately with an equal weight of white crystalline Arsenic, well
pulverized, or else with very white and very fine flowers of Arsenic.
Put this mixture into a glass retort, leaving one half of it empty.
Set your retort in a reverberating furnace; apply a receiver having a
small hole drilled in it, and containing a little filtered rain-water;
lute the receiver to the retort with stiff lute. Begin with putting two
or three small live coals in the ash-hole of the furnace, and replace
them with others when they are ready to go out. Go on thus warming your
vessels by insensible degrees, and put no coals in the fire-place,
till the retort begin to be very warm. You will soon see the receiver
filled with vapours of a dark-red, inclining to a russet colour. With
a bit of lute stop the little hole of the receiver. The vapours will
be condensed in the water of this vessel, and give it a very fine blue
colour, that will grow deeper and deeper as the distillation advances.
If your Salt-petre was not very dry, some drops of Acid will also come
over, and falling from the nose of the retort mix with the water in
the receiver. Continue your distillation, increasing the fire little
by little as it advances, but exceeding slowly, till you see that when
the retort is red-hot nothing more comes off; and then let your vessels
cool.

When the vessels are cold, unlute the receiver, and, as expeditiously
as you can, pour the blue _aqua fortis_ it contains into a crystal
bottle; which you must seal hermetically, because this colour
disappears in a short time when the liquor takes air. You will find in
the retort a white saline mass moulded in its bottom, and some flowers
of Arsenic sublimed to its upper cavity, and into its neck.

Pulverize the saline mass, and dissolve it in warm water. Filter the
solution, in order to separate some arsenical parts that will be left
on the filter. Let the filtered liquor evaporate of itself in the
open air; when it is sufficiently evaporated, crystals will shoot in
it representing quadrangular prisms, terminated at each extremity
by pyramids, that are also quadrangular. These crystals will be in
confused heaps at the bottom of the vessel: over them will be other
crystals in the form of needles; a saline vegetation creeping along the
sides of the vessel; and the surface of the liquor will be obscured by
a thin dusty pellicle.


_OBSERVATIONS._

Arsenic, as we took notice in our Elements of the Theory, besides the
properties it hath in common with metallic substances, possesses others
also in common with saline substances. One of the most remarkable among
the latter is that of decomposing Nitre; of expelling the Acid of that
Salt from its Alkaline basis, assuming its place, and forming with that
Alkali a Neutral Salt, which is very soluble in water, and shoots into
regular crystals.

To inquire into what passes in the decomposition of Nitre by Arsenic,
and into the new Salt resulting from thence, was the design of the
first Memoir given in by me to the Academy of Sciences on this
subject, and from that the present process is copied. Though the whole
quantity of Arsenic prescribed in the process doth not enter into the
composition of the new Neutral Salt, seeing some of it sublimes in
flowers, that quantity must not therefore be thought too great: for
we see, on the other hand, that part of the Nitre is not decomposed.
The needle-like Salt is no other than Nitre that hath not suffered any
decomposition, and actually deflagrates on live coals like common Nitre.

The precaution of putting some water in the receiver is absolutely
necessary, to condense the nitrous vapours that rise in the
distillation: for they are so elastic, so volatile, so dephlegmated,
that a very small part of them will otherwise be condensed into a
liquor, while the rest will remain in the form of vapours, to which
vent must be given through the small hole in the receiver, as without
that they will burst the vessels with impetuosity: and consequently
scarce any Acid will be obtained; especially if the Nitre employed be
very dry, as it must be to be reducible into a fine powder.

The blue colour communicated by the Nitrous Acid to the water is very
remarkable. The cause that produces this colour is not yet known.

Though the Acid is, on this occasion, mortified by a great quantity of
water, yet, when it rises out of the retort, it is so concentrated as
to form, even with that water, if too much be not put in, a most active
and even smoking _aqua fortis_.

It is necessary in this operation, and more so than in any other, to
warm the vessels gradually, and to proceed exceeding slowly; otherwise
the artist runs the risque of seeing his vessels burst to pieces with
violence, and with great danger to his person: for Arsenic acts on
Nitre with incredible vivacity; insomuch that, if a mixture of Nitre
and Arsenic be heated to a certain degree, the Nitre is decomposed
almost as rapidly, and with as great an explosion, as when it is made
to fulminate with an inflammable matter. In short, the appearances are
such, that one would be almost induced to think the Nitre really takes
fire on this occasion: though it be only decomposed just as it is by
the Vitriolic Acid.

The solution of the _caput mortuum_ of this distillation contains, at
the same time, several sorts of Salts: to wit, 1. the Neutral Salt
of Arsenic, formed by the union of the Arsenic with the basis of the
Nitre; this shoots into the prismatic crystals above-mentioned: 2. some
Nitre that hath not been decomposed; this forms the needles and part
of the vegetations: 3. a small portion of Arsenic, that is known to be
soluble in water; this forms the thin dark pellicle that covers the
surface of the liquor when it begins to evaporate.

For the properties of this new Neutral Salt of Arsenic you may consult
what we have said thereupon in our Elements of the Theory, and in the
Memoirs of the Academy of Sciences.


PROCESS V.

_To alkalizate Nitre by Arsenic._

Melt in a crucible the Nitre you intend to alkalizate. When it is
melted, and moderately red, project upon it two or three pinches of
pulverized Arsenic. A considerable effervescence and ebullition
will immediately be produced in the crucible, attended with a noise
like that which Nitre makes, when it detonates with an inflammable
matter. At the same time a thick smoke will rise, which at first will
smell like garlic, the odour peculiar to Arsenic; it will also smell
afterwards like Spirit of Nitre. When the effervescence in the crucible
is over, throw again upon the Nitre as much pulverized Arsenic as
you did the first time; and all the same phenomena will be repeated.
Continue thus throwing in Arsenic in small parcels, till it produce no
more effervescence; taking care to stir the matter at every projection
with an iron wire, the better to mix the whole together. Then increase
your fire, and melt what remains. Keep it thus in fusion for a quarter
of an hour, and then take the crucible out of the fire. It will contain
a Nitre alkalizated by Arsenic.


_OBSERVATIONS._

This operation, as well as the preceding one, is a decomposition of
Nitre by Arsenic; yet the result is very different: for, instead of a
Salt capable of crystallizing, and discovering no tokens either of Acid
or Alkali, we obtain, on this occasion, only a Salt that runs into a
liquor by the moisture of the air, doth not crystallize, and hath all
the properties of an Alkali.

These differences arise only from the different manner in which the
decomposition of the Nitre, and the union of the Arsenic with the basis
of that Salt, is brought about. When the Nitrous Acid is distilled by
the interposition of Arsenic, with a view to obtain the Arsenical Salt,
the operation must be performed in close vessels; no greater degree of
heat must be applied to the mixture than is necessary for enabling the
Arsenic to act; and that heat must be administered very slowly and by
insensible degrees. But, when the business is to alkalizate Nitre by
the means of Arsenic, the operation is performed in a crucible, in a
naked fire, with a strong degree of heat, and that suddenly applied.
The violence of the heat, the suddenness with which it is applied, the
vivacity wherewith the Arsenic unites with the basis of the Nitre; and,
still more than all these, the free access of the air, occasion the
greatest part of the Arsenic, which at first combines with the basis of
the Nitre after having expelled its Acid, to be presently carried off
and dissipated in vapours; and consequently the basis of the Nitre,
not being sufficiently saturated, discovers its Alkaline properties.

I say, the concurrence of the air contributes, still more than all the
rest, to separate the Arsenic from the Alkaline basis of the Nitre;
experience having taught me that the Neutral Salt of Arsenic is not
to be alkalizated by the most violent force of heat, as long as it
continues in close vessels, and the external air hath no communication
with it; but that some of the Arsenic contained in that Salt is
dissipated, by exposing it to a strong heat in open vessels.

The tumult and effervescence that arise, when Arsenic is projected on
Nitre fused in a crucible, are so considerable, and so nearly resemble
the detonation of Nitre with an inflammable matter, that we should
be tempted to think, if we trusted appearances only, that Arsenic
furnishes a combustible matter, and that the Alkalization of the Nitre
is effected, on this occasion, in the same manner as when it is fixed
by charcoal: but, by examining attentively what passes, we easily
discover that there is no inflammation at all, and that the Nitre is
alkalizated in the manner and by the means above pointed out.

The first vapours that rise, when Arsenic is projected on Nitre, are
purely arsenical; and, if any cold body be put in their way, they
adhere to it in the form of flowers. These vapours are actual particles
of Arsenic, carried up by the heat before they could come to act on the
Nitre; but they are soon after mixed with Nitrous vapours, consisting
of the Acid of the Nitre, which the Arsenic expels from its basis as
fast as it comes to act on that Salt.

The nearer you come to the end of the operation, the more does the
matter in the crucible lose of its fluidity, though an equal fire
be constantly kept up in the furnace. At last it becomes quite like
a paste, and the fire must be made much stronger to put it again in
fusion. The reason of this is, that Nitre when alkalizated is much less
fusible than when it is not so. The case is the same when this Salt is
alkalizated by deflagration.

Though the Nitre, when alkalizated, makes no more effervescence with
Arsenic, and though, when kept in fusion, it emits no more arsenical
vapours, it doth not thence follow that it is a pure Alkali, and that
it contains no Arsenic: it still contains a large quantity thereof,
but so strongly united that the force of fire is not able to separate
them; which hath led some authors to give this Salt the title of _Fixed
Arsenic_.

The existence of Arsenic in this saline compound is easily discovered,
by fusing it with metallic substances, on which it produces the same
effects as Arsenic.

With solutions of metals in the Acids, it also presents almost the same
phenomena as the Neutral Salt of Arsenic. Particularly it precipitates
Silver dissolved by the Nitrous Acid in a red powder, as that Salt
does; and the differences observed between the precipitations made by
our new Neutral Salt of Arsenic, and those made by Nitre alkalizated
with Arsenic, can be attributed only to the alkaline quality of the
latter. See the Memoirs of the Academy for 1746.



[Illustration: Decorative Scroll.]

PART II.

OF VEGETABLES.



SECTION I.

_Operations on unfermented Vegetables._



CHAP. I.

_Of the_ SUBSTANCES _obtained from_ VEGETABLES _by_ EXPRESSION _only_.


PROCESS I.

_To express and depurate the Juice of a Plant, containing its Essential
Salt. The Crystallization of that Salt._

Before sun-rise gather a good quantity of the plant from which you
design to express the juice, in order to obtain its Salt. Wash it well
in running water, to clear it of earth, insects, and other adventitious
matters. Bruise it in a marble mortar; put it into a bag of new,
strong, thick linen cloth; tye the bag tight, and commit it to a press.
By pressing it strongly you will squeeze out a great quantity of green,
thick juice, which will have the same taste as the plant. Dilute this
juice with six times as much pure rain-water, and filter it repeatedly
through a woollen bag, till it pass clear and limpid. Evaporate the
filtered juice with a gentle heat, till it be almost as thick as before
it was mixed with water. Put this inspissated juice into a jar, or
other vessel of earth or glass; on its surface pour olive oil to the
depth of a line, and set it in a cellar. Seven or eight months after
this, pour off gently the liquor contained in the vessel, the inside
of which you will find covered with a crystallized Salt. Separate the
crystals gently; wash them quickly with a little fair cold water, and
dry them: this is the Essential Salt of the plant.


_OBSERVATIONS._

Every plant is not equally disposed to yield its Essential Salt,
by the method here proposed. Succulent vegetables only, whose
juices are aqueous and not too viscous, are fit for this purpose.
Such, for example, as sorrel, brook-lime, succory, fumitory,
water-cresses, plantain, &c. An Essential Salt cannot be procured
from those that yield thick, viscid, mucilaginous juices, such as
the seeds of flea-wort; unless their juices be previously attenuated
by fermentation, and that viscosity destroyed which obstructs the
Crystallization of this Salt.

Nor can the Essential Salt be obtained in any quantity from vegetable
matters abounding in Oil. Most kernels and seeds are of this sort:
they all contain a great quantity of fat oil, which so entangles and
clogs this Salt, that the particles thereof cannot shoot away from the
tenacious juices into crystals.

The same is to be said of dry aromatic plants; because they contain
much essential oil, or resinous matters that produce the same effect.
It is true the Essential Salt itself contains a certain portion of
oil; for it is no other than the Acid of the plant incorporated and
crystallized with part of its oil and of its earth: but then the oil
must not be in too great a quantity: because it sheaths the Acid,
renders it clammy, as it were, and hinders it from extricating itself,
so as to be able to exert its qualities, and appear in the form of Salt.

The plants, from which you intend to extract this Salt, should be
gathered in the morning before sun-rise; because they are then most
succulent, not being yet dried up or withered by the heat of the sun.

The juice of plants obtained by expression is very thick; because it
contains many particles of the bruised plant, that are unavoidably
squeezed out along with it. In order to clear it of these superfluous
parts, it is proper to filter it; but as that would be difficult, on
account of the thickness of the juice, it must be thinned, by diluting
it with a quantity of water, sufficient to give it the requisite degree
of fluidity.

Instead of thus diluting the expressed juice, the plant may be ground
with water, before it is put into the press: it will by this means
furnish a more fluid juice, that will easily pass through the filter.
This method may be employed with success on dry plants, or such as are
not very succulent. For this operation rain-water is to be preferred
to any other; because it is the purest: for all waters that have run
some time through the earth, or on its surface, are to be suspected of
containing some saline or selenetic matter, which would mix with and
deprave the Essential Salt.

The juice of the plant, when diluted with the quantity of water
sufficient to facilitate its filtration, is too aqueous to let the Salt
it contains unite into crystals: it must therefore be evaporated, till
it hath recovered a somewhat thicker consistence. The heat applied for
that purpose must be gentle; lest the acid and oily parts, that are to
form the Salt, be spoiled or dissipated, as they are not very fixed. In
summer, the heat of the sun is sufficient to effect this evaporation:
but if you make use of this method, the juice to be evaporated must be
put into several broad flat pans; that, a larger surface being exposed
to the action of the air and sun, the evaporation may be the sooner
completed: for if the juice should continue too long in the degree of
heat requisite for its evaporation, it might begin to ferment; which
would be very detrimental.

The oil poured on the liquor prevents its fermenting, putrefying,
or growing mouldy, during the long space of time required for the
crystallization of the Essential Salt.

These Salts are excellent medicines, being endued with the same virtues
as the plants from which they were obtained.

They cannot be procured from plants by distillation, though they
consist in a great measure of volatile principles: nor are they
obtainable by any other process that requires much heat; because
they are easily decomposed, and the fire changes their natures
entirely. The oily Acids extracted from plants by distillation do not
crystallize, and always have an empyreumatic acrimony, that makes
them very different from the Essential Salts, which are very mild and
saponaceous.


PROCESS II.

_To draw the Oils out of Kernels, Seeds, and Fruits, by Expression._

Pound in a marble mortar, or grind in a mill, the kernels, seeds, or
fruits, out of which you intend to express the Oil. If your matters be
meagre, and grind to meal, suspend that meal in the steam of boiling
water, in order to moisten it a little, and then dry it.

Tye up your matter thus prepared in a new, strong, thick, canvass bag,
and put it into a press, between two iron plates previously heated in
boiling water: squeeze it strongly, and you will see the Oil run in
streams into the receiving vessel.


_OBSERVATIONS._

The Fat Oil of Plants is particularly found in kernels, seeds, and
some fruits; some kernels contain such a vast quantity thereof, that,
on being very slightly bruised in a mortar, they discharge it in great
abundance. Sweet and bitter Almonds, Walnuts, and Lint-seed, are all
of this kind; and require no other management but to be pounded and
pressed, to make them yield a great deal of Oil. But there are others
more meagre, that being ground produce an almost dry flower. In order
to facilitate the expression of the Oil out of such, they must be
expressed, when ground, to the steam of boiling water. For this purpose
the meal may be put into a fine sieve, and that suspended over a pan
half-full of water kept boiling on the fire. The ascending vapours
will moisten the flower, render it more unctuous, and facilitate the
expression of the Oil.

It is proper to dry it a little before it be put into the press,
that it may yield as little water as possible along with the Oil.
Nevertheless, so much water happens now and then to be left in it, that
some is expressed together with the Oil: but as oil and water do not
incorporate, they are easily separated after the operation is finished.

The extraction of the Oil is also greatly facilitated by heating the
plates, between which the oleaginous matters are squeezed: but they
must not be made too hot, if you mean to have a very mild Oil, designed
either for aliment or for medicine; such as the Oil of Olives, and that
of sweet almonds. For this reason the plates must be warmed in boiling
water only: if you heat them to a greater degree, you run the risk of
giving an acrimony to the Oils you express. But, when these Oils are
intended for other uses, the plates may be made hotter, because their
heat increases the yield of Oil.

It is remarkable, that all the Oils obtained by expression, with the
precautions above recommended, are constantly very mild; even though
the matters from which they are extracted be in themselves very acrid.
Mustard-seed, which is so acrid that it is even caustic, yields, by
expression, an Oil as mild as that of sweet almonds. But then the
kernels, seeds, and fruits, from which the Oils are extracted, must
not be old; because these Oils, which are perfectly mild when fresh
and new, become intolerably acrid when they grow old, and acquire this
acrimony even in the fruit itself; for it is observed that these fruits
turn rancid as they grow old.

The Fat Oils obtained by expression are used in medicine, both
internally and externally, as Lenitives and Emollients. Every body
knows the great use of Oil of sweet Almonds, in inflammatory distempers
of the breast and intestines. But it must be carefully noted, that
these Oils can produce no good effects, unless they be fresh expressed,
and from fruits, kernels, or seeds, that have not been long kept: for
they not only lose their lenient virtue by growing old, but they even
acquire an opposite quality, and contract such a sharp acrimony, that
far from procuring any salutary relief or mitigation to the inflamed
parts, they are capable of irritating and inflaming the sound.

It is therefore of the last importance to administer them only when
they are quite fresh: they ought never to be above two or three days
old. Those that are old are generally more limpid and transparent than
the fresh, which look a little more cloudy. The best way to distinguish
them is to taste them, and to try whether or no they leave any
sensation of rancidity on the palate and in the throat.


PROCESS III.

_To draw the Essential Oils of certain Fruits by Expression._

Take the rind of a Citron, Lemon, Orange, Bergamot-pear, or other fruit
of that kind; cut it in slices, and, doubling the slices, squeeze them
between your fingers, over against a polished glass set upright, with
its lower end in a vessel of earth or porcelain. Every time you squeeze
the peel in a new ply, there will squirt out of it several fine jets of
liquor, which, meeting with the surface of the glass, will be condensed
into drops, and trickle down in small streams into the recipient. This
liquor is the Essential Oil of the fruit.


_OBSERVATIONS._

No fruits but those of the kind above-mentioned will yield an essential
Oil by expression. The rind of the fruit is the reservoir of this Oil:
it is contained in little vesicles, which may be seen by the naked eye,
spread all over the surface of the peel, and which, bursting when the
peel is squeezed, discharge the Oil in the form of very fine slender
spouts. Every body knows, that these little oily streams instantly take
fire, when spirted through the flame of a candle: the Oil in this case
is entirely consumed.

The Essential Oil, thus obtained by expression, hath a very sweet and
most agreeable scent. It is in every respect the same as when it made
a part of the fruit that yielded it, seeing it hath not undergone the
action of fire. Yet this method, however good it may be, can hardly be
practised but in the countries where those fruits are in great plenty;
because we cannot by this means obtain any thing near the quantity of
Oil they contain.

This inconvenience may be remedied by rubbing the rind, which contains
the Essential Oil, on the surface of a sugar-loaf. The inequalities of
that surface produce the effects of a rasp, by tearing all the oily
vesicles. The Oil, which issues in abundance, is imbibed by the sugar
and moistens it. When the sugar is sufficiently impregnated therewith,
it may be scraped off with a knife, and put into a well-stopped bottle.
The sugar does not alter the nature of the Oil; which may be kept in
this manner for years, and used, though combined with the sugar, for
almost all the same purposes as when in a fluid state; that is, to
aromatize the several matters with which you incline to mix it. We owe
these observations to Mr. Geoffroy.

This experiment, in which the Essential Oil of a vegetable is obtained
by expression alone, and without the aid of fire, proves that the Oils
of this kind exist naturally in vegetables; and that the Oils of the
same kind obtained by distillation, as shall be shewn in its place, are
not the product of the fire. Essential Oils drawn by expression do not
very sensibly differ from those procured by distillation.



CHAP. II.

_Of the_ SUBSTANCES _obtained from_ VEGETABLES _by_ TRITURATION.


PROCESS I.

_To make the Extract of a Plant by Trituration._

Bruise the vegetable substance of which you intend to make the Extract;
or, if it be hard and dry, grind it to a powder: put the matter thus
prepared, together with seven or eight times as much rain-water, into
an earthen vessel; and into this vessel fit a churning staff, so that
it may be continually whirled round with a rotatory motion, by means
of a cord, a wheel, and a winch. Ply this machine for ten or twelve
hours; and then filter the liquor through two linen cloths spread on a
hair-sieve. Let your filtered liquor stand quiet for twelve hours more:
then pour it off by inclination from the sediment you will find at
bottom; and filter it a second time through a flannel bag.

Pour fresh water, but in a smaller quantity, on the mass left after
trituration with the machine. Triturate it again for four or five
hours. Treat the liquor of this second triture just as you did that
of the first, and mix them both together. Distribute all the liquor
you now have among a sufficient number of shallow earthen plates, and
evaporate it by a gentle warmth, such as that of the sun, or of a
vapour-bath, to the consistence of an Extract, or even to dryness, as
you think proper.


_OBSERVATIONS._

In trituration the water takes up, not only the Salts of plants, but
also a pretty considerable quantity of their oily and earthy parts,
which those Salts have rendered soluble therein, by communicating
to them a saponaceous and mucilaginous quality. After trituration,
therefore, nothing remains but the grossest particles of oil and
earth. Hence it is evident, that the water, in which plants have been
triturated, contains nearly the same principles as the juices of those
plants drawn by expression; and that it is also impregnated with their
Essential Salts: so that, by evaporating it to a due consistence, we
have a well made Extract of the triturated plant.

The Count de la Garaye, who hath long cultivated with great assiduity
those parts of Chymistry by which Medicine may be improved, hath made a
great number of experiments for obtaining from plants, by triture with
water, the matters in which their virtues chiefly reside, and hath also
published a work, entitled Hydraulic Chymistry, in which he gives a
particular account of all the processes for making such Extracts of the
chief mineral, vegetable, and animal substances, as are most frequently
used in the Practice of Physic. His way of evaporating, by a gentle
heat, the liquor containing the Extract of a triturated substance is a
very good one: for we know that heat, if but a very little too strong,
is capable of changing the natures of compound bodies, by disuniting
their principles, and exhaling some of them.

If all vegetable matters were fat and succulent, as most pot-herbs
are, triture would not be necessary for the making an Extract of them,
even without the help of fire. We should have nothing to do, for that
purpose, but to express their juices, as before, clarify them, and
evaporate with a gentle heat to the consistence of an Extract. But
many vegetable substances, such as woods, barks, roots, &c. are dry,
hard, and compact. These matters will not give out their Extract,
without such an application of water as shall dissolve their saline,
saponaceous, and mucilaginous parts. Now this must be effected either
by triture or by fire. Trituration has the advantage of procuring
Extracts, in which the principles are perfectly unaltered, and retain
the same proportions, with respect to each other, as in the plant: but
then it is attended with the inconveniencies of being very tedious,
troublesome, and chargeable. When we come to deliver the methods of
making extracts by decoction and by infusion, we shall see what are the
advantages and disadvantages of preparing Extracts by heat.

The matters, from which an extract is to be made by triture, must be
previously bruised and reduced into small parts, in order to facilitate
the action of water upon them. The several filtrations and decantations
here directed are intended to separate the grosser parts of the plant,
that were only suspended in the liquor, but not truly dissolved, by
means of the agitation and motion: for this reason also, the longer the
liquor is left to settle, the purer will the Extract be.

Though the plant be triturated the first time with a great deal of
water, and for a good while too, yet it is not by that means wholly
exhausted: M. de la Garaye therefore directs the remainder to be
triturated again with fresh water: but this second operation requires
only half the water used in the former, and need be continued only half
the time; the plant having been already opened by the former triture,
and having fewer parts to give out. It is better to add fresh water,
and triturate a second time, than to triturate but once, and for a
greater length of time: for when the water is impregnated with the
principles of the plant to a certain degree, it is less capable of
acting, and of dissolving more, than when it is pure.

As the water impregnated with the principles of the plant by triture
must be almost wholly evaporated, in order to bring those principles
nearer together, and that the whole may lie in the smallest compass
possible; and, moreover, as this evaporation must be effected by the
gentlest heat, it is necessary to spread the liquor so, by distributing
it among a great number of plates, that it shall be reduced in a manner
entirely to surface. By this means the Extract may be evaporated even
to dryness; and this is M. de la Garaye's practice. As the Extracts,
thus evaporated to dryness, cannot be taken up otherwise than in
little scales, the lower surfaces whereof, by adhering to the glazing
of the plate, are smooth and shining, they in some measure resemble a
crystallized Salt; which led M. de la Garaye into an error, and induced
him to give the title of Essential Salts to the Extracts prepared in
this manner. The Essential Salt is indeed contained in them; but still
they are only Extracts, as Mr. Geoffroy hath shewn, in a memoir on this
subject given in by him to the Academy; since, besides the Essential
Salt, they contain moreover, as was said before, a great deal of the
oil and earth of the matters from which they were extracted. This, in
the main, is no objection, but rather an advantage to them; considering
that such saline Extracts are, on that account, so much the more like
the substances from which they were obtained; especially with regard to
their medicinal properties.


PROCESS II.

_To extract from Seeds and Kernels, by Trituration, the Matter of
Emulsions._

Blanch the kernels of which you desire to make an Emulsion; put them
into a marble mortar; add a very little water; and pound them with a
wooden pestle. Continue pounding and triturating till the matter become
like a white paste. From time to time pour on it, by little and little,
more fair water warmed, still continuing the trituration; by which
means the paste will grow thinner. Go on thus till every particle of
your kernels be crushed to pap. Then add, still rubbing the mixture,
enough of water to make the whole an actual fluid; and you will have
a liquor of a dead-white colour, resembling milk. Strain it through a
clean linen cloth; it will leave on the filter some coarse parts, which
must be returned to those left in the mortar. Again triturate and rub
the remainder of the kernels, with the addition of water as before.
This second liquor will not be so white nor so rich as the former:
filter it in the same manner, and again grind with water the solid
parts remaining. In this manner proceed, repeatedly rubbing and adding
fresh water, till it appear no longer milky, but come off clear. The
white milky waters thus obtained go by the name of an _Emulsion_.


_OBSERVATIONS._

All the matters, from which a Fat Oil is obtainable by expression,
produce Emulsions when triturated with water.

An Emulsion consists chiefly of two substances. One of these is
mucilaginous, and soluble in water. This substance by itself would not
give a milky appearance to the Emulsion, which, with it alone, would
be limpid. The other is a Fat Oil, which of itself is not soluble in
water; but being divided by the means of trituration into very small
globules, it is dispersed through the whole liquor, and suspended
therein by the aid of the mucilaginous part. It is this oily part that
gives the Emulsion its dead-white, milky colour; because it is not
actually dissolved in the water, but only diffused through it.

If Oil be mixed with water in a phial, and the mixture strongly shaken
for some time, with a rapid and continued motion, the Oil will be
divided into a vast number of little globules, which intervening
between the parts of the water will destroy its transparency, and give
it a dead-white colour, like that of our Emulsion. But, as the Oil is
not so minutely divided by this means, as by triturating the matters
containing it; and again, there being no mucilage in this liquor, as
there is in Emulsions, the Oil soon separates from the water when it is
left at rest, re-unites into round globules, and these joining together
rise to the surface of the liquor, which then recovers its transparency.

The case is not exactly the same with Emulsions; but something like it
happens to them also. If they be left to stand quiet in a long bottle,
the liquor, which at first appeared homogeneous, separates into two
manifestly different parts. The upper part retains its dead-white
colour, but is thicker and more opaque; while the lower part becomes
perfectly transparent. This is the beginning of an entire separation
of the oily from the aqueous parts. The former, being the lighter,
ascend and gain the upper part of the liquor; while the lower, being
freed from that which obstructed its translucence, recovers its proper
limpidity: but the oily parts do not re-unite into masses large enough
to form one homogeneous whole, with the appearance and limpidness
of Oil; their being minutely divided and entangled in the mucilage
impeding their natural tendency.

Emulsions first begin to spoil, as they grow old, not by turning rancid
and acrimonious like the Fat Oils drawn by expression, but by turning
sour; which is owing to the great quantity of mucilage they contain.
As there is a Fat Oil in their composition, they have the same virtues
with that sort of Oil; but they are, moreover, incrassating, cooling,
and emollient; qualities which render them extremely useful in acute
and inflammatory disorders. They grow sour in a very short time,
especially in the heat of summer; nay, they sometimes do so in two
hours: and therefore they ought to be prepared from time to time as
they are to be used.

The matter that is left when all the substance of the Emulsion is
extracted, and from which the water comes off clear and limpid, is
scarce any thing but the earthy part of the seed or kernel that was
triturated; which, however, still retains a portion of tenacious and
gross Oil, adhering to it so firmly as not to be separable by water.

The chyle and milk of animals resemble an Emulsion in several respects,
and particularly in their dead-white colour; which arises, in the same
manner, from the very minute particles of Oil contained in them, and
distributed through an aqueous gelatinous fluid, but not dissolved
therein. In general, whenever any Oil of any kind happens to be lodged
in this manner between the parts of an aqueous liquor, it always makes
the whole of an opaque white: for Oil will not mix with water, so as to
produce a liquor that shall appear homogeneous and transparent, unless
it be intimately dissolved in the water; which cannot be effected but
by means of an union previously contracted between it and some saline
matter: as is the case of mucilages, certain saponaceous matters, and
some other combinations of which we shall have occasion to treat in the
sequel.

The methods we have hitherto proposed, for extracting from vegetable
substances all that they will yield without the assistance of fire, are
not capable of analyzing those substances accurately, as you may have
observed; since by expression and trituration we obtain only the liquid
parts, impregnated indeed with almost all the principles of plants,
which, however are still combined with each other, and barely separated
from the grossest earthy and oily parts. We must therefore necessarily
have recourse to a more effectual expedient for carrying our analysis
further. This expedient consists in making them undergo the action of
fire, successively graduated, from the gentlest to the most violent
heat.

But, before we enter on this Analysis of Vegetables, it is proper to
describe the different operations that may be performed on Oils, the
only pure principle we have been able to obtain without the help of
fire. As we shall have occasion, when we come to treat of the analysis
of plants by fire, to say a great deal more concerning Essential
Oils, we reserve till then what relates to the operations that may be
performed on them; and confine ourselves here to the operations on Fat
Oils.



CHAP. III.

_Of_ OPERATIONS _on_ FAT OILS.


PROCESS I.

_To attenuate Fat Oils, and change their Nature, by exposing them to
the Action of Fire, and distilling them._

Mix thoroughly three or four pounds of any Fat Oil whatever, with
twice its weight of lime flaked in the air. Put this mixture into a
large earthen retort, leaving a third part of it empty. Set it in a
reverberating furnace, and lute on a receiver. Heat the vessel with a
very gentle fire. A little phlegm will rise first, and will soon be
followed by an Oil that will fall in drops from the nose of the retort.
Continue the distillation very slowly, till you perceive the Oil that
comes over begin to be not quite so fluid as before, but rather a
little thicker.

Then unlute your receiver, and put another in its place. Continue the
distillation, increasing your fire by degrees. The Oil that comes over
will grow thicker and thicker, its fluidity will decrease, and it will
acquire a dark-brown colour, which at last will become blackish. The
Oil will then be very thick. Push the operation till nothing more will
come off, though the retort be red-hot. During the whole time this
distillation lasts, there rises a good deal of water, in company with
the Oil. Keep the second thick Oil by itself.

Mix the Oil that came over first, in this operation, with an equal part
of fresh lime flaked in the air. Put the mixture into an earthen or
glass retort, of a size so proportioned to the quantity, that a third
part thereof may remain empty. Distil as before. The same phenomena
will appear: a clear Oil will first come over, and be succeeded by one
a little thicker. Then shift your receiver, and distil off all the
rest of the Oil with an increased fire. The first Oil obtained by this
second distillation will be clearer and thinner than that of the first
distillation; and the second Oil will not be so thick, nor of so deep a
colour as before.

Distil over again, in the same manner, the thin Oil of this second
distillation, and go on thus repeatedly distilling, till the first
clear oil come over with a degree of heat not exceeding that of boiling
water. Then, instead of mixing your Oil with lime, put it with some
water into a glass retort, or into a body with its head fitted on, and
distil it, keeping the water just in a simmer. Your Oil will be more
and more attenuated, and, after being thus distilled twice or thrice
with water, will be so limpid, so thin, and so clear, that you will
scarce be able to distinguish it from water itself.


_OBSERVATIONS._

Fat Oils, which are naturally mild, unctuous, inodorous, or have at
most a scarce perceptible smell, resembling that of the fruit or kernel
from which they were extracted, change their natures totally when
exposed to the action of fire. If they be but heated so as to boil,
they become acrid, lose much of their unctuosity, and acquire a very
pungent odour. From several analogies, and by several experiments,
recited in a Memoir on Oils which I read to the Academy, I shewed that
these alterations of Fat Oils are produced by the fire's extricating an
Acid in them, which before lay concealed and inactive. What I advanced
on this subject may be seen in the Memoirs of the Academy for 1745, and
in my Elements of the Theory of Chymistry. I shall take occasion to add
something more, in my Observations on the following process, by which
these Oils are combined with Acids. In this place I shall only examine
what passes in the repeated distillations they are here made to undergo.

Fat Oils do not rise in distillation without a degree of heat greater
than that of boiling water; and therefore they must be distilled in
a sand-bath, or with a naked fire. We prefer the latter method, for
reasons elsewhere assigned, and chiefly because the operator is more
master of his fire; it being absolutely necessary, in this operation,
that he have it in his power to suppress it in an instant, when he
finds it too strong: for, in such a case, it will impetuously raise
the thin Oil mixed with the thick; nay, the whole will be burnt, as
it were, to a coal, if a degree of fire ever so little too strong
be kept up but for a few moments. When this accident happens, it is
always predicted by a great quantity of white vapours ascending with
impetuosity out of the retort, and by drops of Oil following each other
very fast, that are scarce limpid at first, and soon become of a dark
colour. All this may be prevented by distilling very slowly, and with
great patience.

Fat Oils may be distilled and attenuated without any additament: but
then the operation, which is tedious and troublesome enough, even when
lime is used, as appears from our description of the process, would be
much more so if the Oil were distilled alone, without the addition of
any thing to divide it, spread it, and enlarge its surface.

Lime is one of the best additaments that can be employed on this
occasion; not only because it procures the advantages just mentioned,
but also by reason that, being an absorbent of fat matters, it unites
with the grosser parts of the Oil, retains them, and so allows the
thinnest and lightest parts to be readily separated from the rest. By
this means it greatly expedites the operation: and, the more of it is
added, with respect to the oil, the sooner is a considerable quantity
of thin limpid Oil obtained: and this is the reason of our directing
a double quantity of lime to be mixed with the Oil in the first
distillation.

Lime slaked in the air is employed preferably to quick-lime; because
it is naturally divided into a very fine powder, and capable of mixing
perfectly with all sorts of matters.

The water that first appears in the distillation comes from the
lime: it is part of the humidity which the lime had imbibed from
the air. This water continues to rise with the Oil during the whole
distillation, according as the degree of heat is increased: and, if the
distillation be finished by keeping the retort red-hot for some time
after all is come over, the lime in it will have a greyish cast, and,
when water is poured on it, grow almost as hot as quick-lime.

If you resolve to carry on these distillations of a Fat Oil, till it
becomes as light as an Essential Oil, it is necessary to begin with
a pretty large quantity thereof, as three or four pounds: for the
quantity of the Oil is considerably lessened by every distillation; not
only because the thickest and grossest part is separated from it every
time; but also because a portion of the Oil remains so strongly united
with the lime, that the force of fire is not able to separate them.
Moreover, there is reason to believe that some of it is decomposed
every time it is distilled.

If Oil be distilled by itself, the thickest and heaviest part remains
charred, as it were, in the retort, the inside of which is lined with a
crust of coal, that is to the last degree fixed: this therefore always
occasions a diminution of the Oil.

A Fat Oil must be distilled eight or nine times, even with lime, before
it become as light as an Essential Oil, and capable of rising wholly
with the heat of boiling water: by that time therefore it must be
considerably diminished; and if, at least, the quantity prescribed be
not taken at first, there will scarce remain a few ounces capable of
being distilled with water.

The portion of thick heavy Oil, obtained in the several distillations,
may, if you will, be rectified again. For this purpose you must mix it
with fresh lime, and distil it as you did the clear Oil. A portion of
this also will be attenuated, and come over first. Thus all the Fat
Oil may be subtilized by the action of fire; an absolutely charred
black part excepted, that remains fixed, and appears susceptible of no
change, but by burning it in the open air, and thereby reducing it to
ashes, from which a little Fixed Alkali may be obtained. In this fixed
part of the Oil the acid and earthy parts are combined therewith, in a
greater proportion than they ought to be in pure Oil.

The portion of Oil that hath become light and thin is nothing but the
purest oily part, separated from the gross acids, and from a certain
quantity of earth, which made it thick and heavy. This Oil resembles
the Essential Oils in lightness, fluidity, and a penetrating agreeable
odour: it dissolves in Spirit of Wine. We shall have occasion in the
sequel to enlarge further on the qualities of the several sorts of
Oils, and their solubility in Spirit of Wine, when we come to treat of
Ardent Spirits and of Æther.


PROCESS II.

_To combine Fat Oils with Acids. The Decomposition of this Combination._

Put any Fat Oil whatever into a glass bason, and set it in a sand-bath
very moderately heated. Pour on this Oil an equal quantity of
concentrated Oil of Vitriol, which will immediately dissolve it with
violence; a considerable ebullition and effervescence will arise,
attended with great heat, and a prodigious quantity of black, thick
vapours, in which may be easily perceived the smell of burnt Oil,
together with that of a Sulphureous Acid. The mixture will become of
a deep-red, black, and thick. Stir it with a small stick, till you
observe that all is quiet.


_OBSERVATIONS._

The Vitriolic and Nitrous Acids unite with Fat Oils, and dissolve
them with violence; but these Acids must be sufficiently strong and
concentrated, otherwise they will not act upon the Oils. The Vitriolic
Acid, in particular, dissolves them pretty thoroughly. If hot water
be poured on the mixture described in our process, this water will
become cloudy and milky, by dissolving some of it: so that Oils may be
rendered soluble in water by the means of Acids. Spirit of Wine, which
doth not attack Fat Oils in their natural state, unites perfectly with
them, and makes a clear limpid solution of them, when they are thus
combined with Acids.

The Acids also suffer a considerable alteration by contracting an union
with Oils. They become much milder, and lose almost all their strength.
If the mixture described in the process be distilled, there will come
over a great quantity of an empyreumatic acidulated phlegm, that
smells strong of Sulphureous Spirit; an Oil thinner than the original
saponaceous mixture; a weak Oily Acid, and a very thick, black Oil. If
the fire be made very strong, when the Oil ceases to rise, it sometimes
happens that a little Sulphur sublimes into the neck of the retort.

By this analysis it appears, that the strong concentrated Acid, which
was an ingredient in the combination, is not now to be found. The
Vitriolic Acid hath changed its nature, and is considerably weakened
by the union it hath contracted with the principles of the Oil. The
aqueous part of this latter substance weakens the other, and loads it
with phlegm; the inflammable part thereof renders it sulphureous, and
even converts it into Sulphur.

Hence it follows, that same part of the Oil is decomposed, by the
union it contracts with the Vitriolic Acid; for its phlogiston and its
aqueous principle cannot be disunited, so as to form a Sulphureous
Spirit, or an actual Sulphur, and an aqueous Acid, without the
decomposition of a certain quantity of the Oil, in proportion to the
two disjoined principles. Another portion of the Oil remains united
with the Vitriolic Acid, without suffering any decomposition, and
communicates to that portion of the Acid, with which it is combined,
a somewhat saponaceous quality, which makes it resemble the Vegetable
Acids.

Thus we see, that when the Vitriolic Acid and a Fat Oil are combined
together, they both suffer considerable changes; the Acid by the new
alliances into which it enters, and the Oil by the decomposition it
undergoes. In consequence hereof a much smaller quantity of Oil is
obtained, by decompounding this combination, than was at first put in.

If the Oil abstracted by distillation be combined again with a fresh
quantity of the concentrated Acid, the same effects will again follow;
and by this means any quantity of Oil at pleasure may be entirely
decomposed. This single experiment affords an evident proof of many
important truths advanced in our Elements of the Theory.

Spirit of Nitre likewise dissolves expressed Oils. With Oil of Olives
it forms a white paste, resembling a fine pomatum. This compound is
perfectly soluble in Spirit of Wine. The Acid must be very strong and
smoking to unite with this, or with any other Fat Oil: but it dissolves
some of them with more rapidity than others; in which number is the Oil
of Walnuts. It acts on these Oils with so much vehemence that it burns
them, in some measure, making them black and thick.


PROCESS III.

_To combine Fat Oils with Fixed Alkalis. Hard and soft Soap. The
Decomposition of Soap._

Take a lixivium of Alicant kelp made more caustic by lime, as we shall
shew when we come to speak of Alkalis. Evaporate this lye till it be
capable of bearing a new-laid egg. Divide it into two parts; and to one
of these put just water enough to weaken it so, that a new-laid egg
will not swim in it, but fall to the bottom. With the lye thus weakened
mix an equal quantity of fresh-drawn Olive Oil. Stir and agitate the
mixture well, till it become very white. Set it over a gentle fire,
and continue stirring it incessantly, that the two ingredients of
which it is compounded may gradually combine together, as part of the
water evaporates. When you perceive they begin to unite, pour into the
mixture thrice as much of the first strong lye as you took of Olive
Oil. Continue the coction with a gentle fire, always stirring the
matter, till it becomes so thick that a drop of it fixes, as it cools,
into the consistence that Soap ought to have. By dissolving a little
of this Soap in water, you will discover whether or no it contains
more Oil than ought to be in the composition. If it dissolves therein
wholly and perfectly, without the appearance of the least little drop
of Oil floating on the water, it is a sign that it doth not contain
too much Oil. If, on the contrary, you perceive any of these little
globules, you must pour into the vessel, containing your matter, a
little more of the strong lye, to absorb the redundant Oil. If there be
too much of the Alkali it may be discovered by the taste. If the Soap
leave on your tongue the sensation of an Alkaline Salt, and produce an
urinous savour, it is a sign that there is too much Salt in proportion
to the Oil. In this case a little Oil must be added to the mixture, to
saturate the super-abundant Alkali. An excess in the quantity of Alkali
discovers itself likewise by the Soap's growing moist in the air, on
being exposed to it for some time.


_OBSERVATIONS._

Fixed Alkalis, even when resolved into a liquor, that is, when loaded
with much water, unite easily with Fat Oils, as appears from the
experiment just recited, and require but a moderate heat to perfect
that union. This combination may even be completely effected without
the aid of fire, and by the heat of the sun only, provided sufficient
time be allowed for that purpose; as Mr. Geoffroy found upon trial. It
only requires the mixture of the Oil and Alkali to be kept five or six
days in digestion, and stirred from time to time. A lixivium of pure
Alkali, not acuated by lime, may also be used to make Soap: but it is
observed, that the combination succeeds better, and that the Alkali
unites sooner and more perfectly with the Oil, when it is sharpened by
lime.

The Oil is first mixed with a weaker and more aqueous lye, to the end
that the combination may not take place too hastily, but that all the
particles of the two substances to be compounded together may unite
equally. But as soon as the Alkali begins to dissolve the Oil gradually
and quietly, the dissolution may then be accelerated; and that is done
by adding the remaining lye, which is stronger and less diluted than
the other.

Soap made with Olive Oil is white, hard, and hath not a very
disagreeable smell: but as that Oil is dear, others, even the fat and
oils of animals, are sometimes substituted for it. The Soaps made with
most of these other matters are neither so hard, nor so white, as that
made of Olive Oil: they are called _Soft Soaps_.

Oils thus associated with Fixed Alkalis are by that means rendered
soluble in water; because the Alkaline Salts, having a great affinity
with water, communicate part thereof to the Oils with which they are
now incorporated. Yet the Oil is not for all that rendered thoroughly
miscible with water, or perfectly soluble therein; for the water in
which Soap is dissolved hath always a milky cast: now there is no other
criterion of a perfect solution but transparency.

Alkalis also lose part of their affinity with water, by the union
they thus contract with Oils: for, when the combination is properly
made, they no longer attract the moisture of the air, nor doth water
dissolve them in such quantities as before. The composition of Soap is
plainly a saturation of an Alkali with an Oil; and, in order to make
perfect Soap, we are forced, as was said in the process, to grope, in a
manner, by repeated trials, for this point of saturation; just as when
we prepare a Neutral Salt by saturating an Alkali with an Acid. The
union which the Oil contracts with the Alkali makes it lose, in part,
the readiness with which it naturally takes fire; because the Salt is
not inflammable: the water also, which enters in pretty considerable
quantities into the composition of Soap, as we shall presently see,
contributes a good deal to hinder the accension of the Oil.

Soap may be decompounded either by distilling it, or by mixing it with
some substance that hath a greater affinity than Oil with Alkalis.

If we decompound it by distillation, a phlegm, or transparent spirit,
of a somewhat yellowish colour, first comes over. This liquor is the
aqueous part of the Soap, quickened by a little of its Alkali, which
gives it an acrid taste. It is followed by a red Oil, which at first
is pretty thin and limpid, but thickens as the distillation advances,
grows black, and has a very disagreeable empyreumatic smell. This Oil
is soluble in Spirit of Wine.

When the distillation is finished, that is, when the retort being kept
red-hot for some time will discharge no more, there is left in it a
saline mass; which is the Alkali of the Soap, crusted over with some
of the most fixed parts of the Oil, that are charred to a coal. This
Salt may be restored to the same degree of purity it had before its
combination with the Oil, by calcining it in a crucible with a naked
fire, that may consume this burnt part of the Oil, and reduce it to
ashes.

It is plain that the Oil contained in Soap is affected by distillation,
much in the same manner as that which we mixed with lime and distilled.

Mr. Geoffroy, by analysing Soap with care, discovered that two ounces
thereof contain ninety-six grains of Salt of kelp, freed from all Oil
and moisture; or two drams and forty-eight grains of that Salt, as it
is used in manufacturing Soap; that is, containing water enough to make
it crystallize; one ounce three drams twenty grains of Olive Oil; and
about two drams four grains of water.

As Acids have a greater affinity than any other substance with Alkalis,
they may be very effectually employed to decompound Soap.

If you propose to decompound Soap by means thereof, you must first
dissolve it in a sufficient quantity of water. Mr. Geoffroy, who made
this experiment likewise, dissolved two ounces thereof in about three
gallons of warm water, and to the solution added Oil of Vitriol, which
he let fall into it drop by drop. Every time a drop of Acid falls into
it, a _coagulum_ is formed in the liquor. The vessel in which the
solution is contained must then be shaken, that the Acid may equally
attack all the Alkali diffused in it. When no new coagulation is
produced by a drop of the Acid, it is a sign you have added enough.
The liquor then begins to grow clear: and if another quart of water be
added, in order to facilitate the separation of the oily particles, you
will see them rise and unite together on the surface of the liquor.

This is a pure, clear, true Olive Oil, hath its taste, its smell, and,
like it, is fluid in warm weather, and becomes fixed by cold. Yet it
differs in some respects from that which never hath been united with
an Alkali in order to form a Soap; for it burns more vividly and more
rapidly, and is soluble in Spirit of Wine. We shall account for these
differences when we come to treat of Ardent Spirits.

Not only the Vitriolic Acid, but all others, even those obtained from
vegetables, are capable of decompounding Soap, and separating the Oil
from the Alkali. In the liquor wherein Soap is thus decompounded is
found a Neutral Salt, consisting of the Acid made use of, united with
the Alkali of the Soap. If the Vitriolic Acid be used, you will have a
Glauber's Salt; a quadrangular Nitre, if the Nitrous Acid be used; and
so of the rest.

The facility with which Acids decompound Soap is the reason that no
water, but what is very pure, will dissolve it, or is fit to be used in
washing with it.

Water that doth not dissolve Soap well is usually called _Hard Water_.
Such waters contain a certain quantity of saline matters, washed out of
the earths through which they pass. The hardness of water is generally
occasioned by selenitic particles.

The hardness of all the well-water in and about Paris is owing to a
considerable quantity of Selenetic Gypsum with which the Soil abounds.
The Selenites, we know, are Neutral Salts, consisting of the Vitriolic
Acid united with an earthy basis. If therefore Soap be put into water
in which a Salt of this kind is dissolved, it is evident that the
Vitriolic Acid in the Selenites, having a greater affinity with the
fixed Alkali of the Soap than with its own earthy basis, will quit the
latter to unite with the former; and thus the Soap will be decompounded
instead of being dissolved. Accordingly we see, that, when we attempt
to dissolve Soap in our well-water, the surface of the liquor is
in a short time covered with a fat oily pellicle. However, this
decomposition of Soap is not complete; at least, but a small part of
it is perfectly decompounded; because the great quantity of Selenites,
with which the water is impregnated, hinders the Soap from mixing so
thoroughly with it, as is requisite to produce a total decomposition
thereof.

All mineral waters are likewise hard, with regard to Soap; for as most
of them owe their virtues to the efflorescences they have washed off
from pyrites, that have grown hot and begun to be decomposed, they are
impregnated with the saline matters produced by pyrites in that state:
that is, with aluminous, vitriolic, and sulphureous substances, which
have the same effect on Soap as the Selenites have.

Mineral waters containing Neutral Salts only, such as Sea-salt, Epsom
Salt, Glauber's Salt, are nevertheless hard with regard to Soap,
though the Acids of those Salts, being united with Fixed Alkalis, are
incapable of decompounding it. The reason is, that those Neutral Salts
are more soluble in water than Soap is; so much indeed as even to
exclude it: because each of the two principles that composed them hath
a very great affinity with water; whereas only one of the principles
of Soap, namely, its Alkali, hath that affinity; the other, to wit,
the oily principle, having none at all. Thus water impregnated with
an Acid, or with any Neutral Salt, is hard with regard to Soap, and
incapable of dissolving it; and hence it follows, that Soap is a sort
of touchstone for trying the purity of water.

Wine dissolves Soap; but imperfectly, because it contains an acid or
tartarous part. Spirit of Wine also dissolves it: but neither is this
dissolution perfect; because it contains too little water: for its
spirituous part can dissolve nothing but the Oil of the Soap; and the
Alkali is not at all, or at least in a very small quantity, soluble in
this menstruum. The true solvent of Soap is therefore a liquor that is
partly spirituous, partly aqueous, and not acid.

Brandy has these qualities: and accordingly it is the solvent that
unites best with Soap, dissolves the greatest quantity, and makes the
most limpid solution thereof. Yet even this solution hath something
of a milky cast, occasioned by its not being entirely free from an
Acid, or the tartarous principle. This fault may be easily corrected,
by mixing with it a little Alkali to absorb the Acid. A dram of
crystallized salt of kelp mixed with three ounces and a half of good
brandy, renders it capable of dissolving an ounce and two drams of good
hard Soap, into a perfectly limpid liquor. This experiment also we owe
to Mr. Geoffroy.

Some years ago it was discovered that Soap might be used with great
success in Medicine, and that it possesses the property of dissolving
the stony concretions that form in several parts of the body,
particularly in the kidneys and bladder. Soap is the basis of the
composition known by the name of _Mrs. Stephen's Remedy_, and in this
one ingredient its whole virtue resides.

From what hath been said on the nature of this compound, as well as on
the cause and phenomena of its dissolution, it plainly appears to be
of the last consequence, in administering it to a patient, that his
constitution be considered, and a proper regimen ordered. All Acids
should be absolutely forbid him; as we know they hinder the Soap from
dissolving, and decompound it; and if the patient have any acidities
in the first passages, matters capable of neutralizing them should be
prescribed him: as prepared crabs eyes, and other absorbents known in
Medicine: in such cases those with which the Soap is compounded in Mrs.
Stephen's remedy may be of use.


PROCESS IV.

_To combine Fat Oils with Sulphur._

Put any Fat Oil whatever into an earthen vessel; add to it about the
fourth part of its weight of Flower of Sulphur, and set the vessel in
a furnace, with lighted coals under it. When the Oil hath acquired
a certain degree of heat, the Sulphur will melt, and you will see
it fall immediately to the bottom of the Oil, in the form of a very
red fluid. The two substances will remain thus separated, without
mixing together, while the heat is no greater than is necessary to
keep the Sulphur in fusion. Increase it therefore; but slowly and with
circumspection, lest the matter take fire. When the Oil begins to
smoke, the two liquors will begin to mix and look turbid: at last they
will unite so as to appear one homogeneous whole. If you keep up the
heat so that the mixture shall always continue smoking and ready to
boil, you may add more Sulphur, which will perfectly incorporate with
it: and thus may a pretty considerable quantity thereof be introduced
into this composition.


_OBSERVATIONS._

The Phlogiston and the Vitriolic Acid have each an affinity with Oils.
It is not therefore surprising that Sulphur, which is a compound of
these two substances, should be soluble in oily matters. Yet it is
remarkable, that Essential Oils, which are much thinner than the Fat
Oils, dissolve Sulphur with much more difficulty; as will be shewn when
we come to treat of those Oils; and that Spirit of Wine, which contains
an exceeding subtile Oil, doth not act upon Sulphur at all.

Oil, by contracting an union, with Sulphur, produces a considerable
alteration in that mineral: a phenomenon so much the more surprising,
that we know it to be in some sort unalterable by any other solvent,
of what kind soever, add, that its nature admits of no change but by
burning. We shall say more on this subject under the head of Essential
Oils.


PROCESS V.

_To combine Fat Oils with Lead, and the Calces of Lead. The Basis of
Plasters. The Decomposition of this Combination._

Into an earthen vessel put granulated Lead, Litharge, Ceruse, or
Minium; and pour thereon twice its weight of any Fat Oil whatever. If
you set the vessel over a brisk fire, the Lead at bottom will melt
before the Oil begin to boil. When it boils, stir the matter with a
stick: the Lead, or the Calx of Lead, will gradually disappear, and
at last be totally dissolved by the Oil, to which it will give a very
thick consistence.


_OBSERVATIONS._

Fat Oils dissolve not only Lead, but its calces also: nay, they
dissolve the latter more readily than Lead in substance; probably
because they are more divided. The result of a combination of these
matters is a thick, tenacious mass, that grows in some degree hard in
the cold, and soft by heat. This composition is known in Pharmacy by
the name of _Plaster_. It is made up with several drugs into plasters,
which partake of the virtues of those drugs; so that it is the basis of
almost all plasters.

Lead itself is seldom used to make plasters: Ceruse, Litharge, or
Minium, are preferred to it; because these matters unite, as hath been
said, more readily and more easily with Oils.

It sometimes happens, that the Oil is burnt in the operation, and that
the calx of Lead is partly resuscitated: and this gives the plaster
a black colour, which however it ought not to have. This accident is
occasioned by an excess of heat: and as it is very difficult to keep
the Oil and the Lead in the proper degree of heat, seeing both these
matters are apt to grow very hot, it hath been contrived to put into
the vessel, in which the coction is to be performed, a pretty large
quantity of water; which being susceptible only of a much smaller and
a certain degree of heat, that is constantly the same when it boils,
procures the advantage of having the composition very uniform and very
white.

It is necessary to stir the mixture incessantly, in order to prevent
the burning of the combined Oil and Lead; which, as they unite, sink
in the water by their greater weight. If the water happen to be wasted
before the Oil hath dissolved all the Lead, or before the plaster hath
acquired a proper degree of consistence, you must remove the vessel
from the fire, and let the mixture cool, before you add more: for, if
this precaution be neglected, the heat of the matter, which is now
much greater than that of boiling water, will occasion a considerable
explosion and extravasation thereof, though the water poured into it be
as hot as possible.

The combination of Fat Oil with a Calx of Lead may be considered as
a sort of metallic Soap, having a metalline Calx, instead of a Fixed
Alkali, for its basis. Mr. Geoffroy hath observed, that if a pound of
Litharge, rubbed very fine and well washed, be incorporated with two
pounds of Olive Oil, in the same manner as plaster is made, keeping
water enough in the vessel to hinder the mixture from burning, there
rises a smoke, while the Oil is uniting with the Calx of Lead, smelling
much like that which rises from Soap.

The Oil may be separated from the Calx of Lead, by the methods used to
separate it from a Fixed Alkali: and when it is so separated, it hath
the same properties as that separated from common Soap.

This species of metallic Soap, formed by the union of a Fat Oil with
the Calx of Lead, is not soluble in water, and communicates nothing to
it but a greasy taste. Therefore, if you would decompound it by the
means of an Acid, you must pour that Acid immediately on the compound.
The Acid will attack and dissolve the Calx of Lead; and the Oil, being
thus set at liberty, will rise clear and limpid to the surface of the
acid liquor. Distilled vinegar effects this separation better than any
other Acid, because it is the true solvent of Lead.



CHAP. IV.

_Of the_ SUBSTANCES _obtained from_ VEGETABLES _with a Degree of Heat
not exceeding that of boiling Water_.


PROCESS I.

 _To obtain from Plants, by distilling them with the mean Degree of
 Heat between freezing and boiling Water, a Liquor impregnated with
 their Principle of Odour._

In the morning, before sun-rise, gather the plant from which you design
to extract its odoriferous water. Chuse the plant in its full vigour,
perfectly sound, and free from all adventitious matters, except dew.
Put this plant, without squeezing it, into the body of a tinned copper
alembic, and set it in a water-bath. Fit on its head, and to the nose
thereof lute a glass receiver with wet bladder.

Warm the bath to the mean degree between freezing and boiling water.
You will see a liquor distil and fall drop by drop into the receiver.
Continue the distillation with this degree of heat, till no more drops
fall from the nose of the alembic. Then unlute the vessels; and if
you have not as much liquor as you want, take out of the cucurbit the
plant already distilled, and put a fresh one in its place. Distil
as before, and go on thus till you have a sufficient quantity of
odoriferous liquor. Put it into a bottle; stop it close; and set it in
a cool place.


_OBSERVATIONS._

The liquor obtained from plants, with the degree of heat here
prescribed, consists of the dew that was on the plant, and some of the
phlegm of the plant itself, together with its odorous principle. Mr.
Boerhaave, who examined this odoriferous part of plants with great
care, calls it the _Spiritus Rector_. The nature of this Spirit is
not yet thoroughly ascertained; because it is so very volatile, that
it cannot easily be subjected to the experiments that are necessary
to analyze it, and to discover all its properties. If the bottle
containing the liquor, which may be considered as the vehicle of this
Spirit, be not exceeding carefully stopped, it flies quite off: so that
in a few days nothing will be found but an insipid inodorous water.

Great part of the virtue of plants resides in this their principle
of odour; and to it must be ascribed the most singular and the most
wonderful effects we every day see produced by them. Every body
knows, that a great number of odorous plants affect, in a particular
manner, by their scent only, the brain and the _genus nervosum_, of
such especially whose nerves are very sensible, and susceptible of
the slightest impression; such as hypochondriacal or melancholy men,
and hysterical women. The smell of the Tuberose, for instance, is
capable of throwing such persons into fits, so as to make them drop
down and swoon away. The smell of Rue, again, which is equally strong
and penetrating, but of a different kind, is a specific remedy against
the ill effects of the Tuberose; and brings those persons to life
again, with as quick and as surprising an efficacy, as that by which
they were reduced to a state not unlike death. This is Mr. Boerhaave's
observation.

The odorous exhalations of plants must be considered as a continual
emanation of their _Spiritus Rector_: but as growing plants are in a
condition to repair, every instant, the losses they sustain by this
means, as well as by transpiration, it is not surprising that they
are not soon exhausted, while they continue in vigour. Those, on the
contrary, which we distil, having no such resource, are very soon
entirely deprived of this principle.

The separation of the _Spiritus Rector_ from plants requires but a
very gentle heat, equally distant from the freezing point and from
the heat of boiling water. Accordingly the heat of the sun in summer
is sufficient to dissipate it almost entirely. This shews why it is
dangerous to stay long in fields, or woods, where many noxious plants
grow. The virtues of plants residing chiefly in their exhalations,
which the heat of the sun increases considerably, a sort of atmosphere
is formed round them, and carried by the air and the wind to very great
distances.

For the same reason the air of a country may be rendered salutary and
medicinal, by the exhalations of wholesome plants growing therein. From
the facility with which the odorous principle of plants evaporates, we
learn what care ought to be taken in drying those intended for medical
uses, so as to preserve their virtues. They must by no means be exposed
to the sun, or laid in a warm place: a cool, dry place, into which the
rays of the sun never penetrate, is the properest for drying plants,
with as little loss of their virtue as possible.

Though there is reason to believe that every vegetable matter hath
a _Spiritus Rector_, seeing each hath its particular scent, yet
this principle is not very perceptible in any but those which have
a very manifest odour: and accordingly it is extracted chiefly from
aromatic plants, or the most odoriferous parts of plants. I say the
most odoriferous parts; because, in most plants and trees, there are
generally certain parts that have a much more sensible, and much
stronger scent than the rest. The odour of a plant, or of a tree, hath
its principal residence sometimes in the root, sometimes in the leaves,
at other times in the bark or wood, and very frequently in the flowers
and seeds. Therefore, when you design to extract the principle of odour
from a vegetable that is not equally odoriferous in every part, you
must chuse those parts that have the most perceptible and strongest
scent.


PROCESS II.

_To extract the Fat Oils of Plants by Decoction in boiling Water. Cacao
Butter._

Pound or bruise in a marble mortar your vegetable substances, abounding
with the Fat Oil which you intend to extract by decoction: tie them
up in a linen cloth; put this packet into a pan, with seven or eight
times as much water, and make the water boil. The Oil will be separated
by the ebullition, and float on the surface of the water. Skim it off
carefully with a ladle, and continue boiling till no more Oil appear.


_OBSERVATIONS._

The heat of boiling water is capable of separating the Fat Oils from
vegetable matters that contain any: but this is to be effected by
actual decoction only, and not by distillation; because these Oils will
not rise in an alembic with the heat of boiling water. We are therefore
necessitated to collect them from the surface of the water, as above
directed. By this means a much greater quantity of Fat Oil may be
obtained than by expression alone; because the degree of heat applied
greatly facilitates the separation of the Oil. For a convincing proof
of this truth, take the remains of any vegetable matters, from which
the Oil hath been so thoroughly expressed that they would yield no
more; boil them in this manner, and you will obtain a great deal more
Oil.

The water used in this coction generally becomes milky, like an
emulsion; because it contains many oily particles, that are dispersed
in it just as in an emulsion. Nevertheless, this way of obtaining the
Fat Oils is not generally practised; because the heat, to which they
are exposed in the operation, occasions their being less mild than they
naturally are: but it is an excellent method, and indeed the only one
that can be employed, for extracting from particular vegetables certain
concrete oily matters, in the form of Butter or Wax; which matters are
no other than Fat Oils in a fixed state. The Cacao yields, by this
means, a very mild butter; and in the same manner is a Wax obtained
from a certain shrub in America.

The heat of boiling water melts these oily matters, which then ascend
to the surface of the liquor, and float on it like other Oils. They
afterwards fix as they cool, and resume their natural consistence. We
shall see in the sequel, that they cannot be extracted in a concrete
form by distillation, which requires a greater degree of heat than
that of boiling water; because distillation changes their nature,
partly decomposes them, and prevents their returning to their proper
consistence as they cool.


PROCESS III.

_To extract Essential Oils of Plants by Distillation with the Heat of
boiling Water. Distilled Waters._

Put into a cucurbit the plant from which you design to extract the
Essential Oil. Add as much water as will fill two thirds of your
vessel, and dissolve therein half an ounce of Sea-salt for every quart
of water you use. To this body fit on an alembic-head, and to the nose
thereof lute a receiver, with sized paper, or wet bladder. Set it in a
furnace, and let the whole digest together, in a very gentle warmth,
for twenty-four hours.

This being done, light a wood-fire under your vessel, brisk enough to
make the water in it boil immediately. Then slacken your fire, and
leave it just strong enough to keep the water simmering. There will
come over into the receiver a liquor of a whitish colour, somewhat
milky; on the surface of which, or at the bottom, will be found an Oil;
which is the Essential Oil of the vegetable you put into the cucurbit.
Continue your distillation with the same degree of heat, till you
perceive the liquor come off clear, and unaccompanied with any Oil.

When the distillation is finished, unlute the receiver; and, if the
Essential Oil be of that sort that it is lighter than water, fill the
vessel up to the top with water. On this occasion a long-necked matrass
should be used for a receiver; that the Oil which floats on the water
may collect together in its neck, and rise up to its mouth. Then in the
neck of this vessel put the end of a thread of cotton-twine, so that
the depending part without the vessel may be longer than that in the
Oil, and the extremity thereof hang within the mouth of a little phial,
just big enough to contain your quantity of Oil. The Oil will rise
along the yarn as in a siphon, filter through it, and fall drop by drop
into the little phial. When all the Oil is thus come over, stop your
little bottle very close, with a cork coated over with a mixture of wax
and a little pitch.

If your Oil be ponderous, and of the sort that sinks in water, pour the
whole contents of the receiver into a glass funnel, the pipe of which
must terminate in a very small aperture that may be stopped with your
fore-finger. All the Oil will be collected in the lower part of the
funnel: then remove your finger, and let the Oil run out into a little
bottle through another small funnel. When you see the water ready to
come, stop the pipe of the funnel, and cork the bottle containing your
Oil.


_OBSERVATIONS._

Essential Oils, though they all resemble each other in their principal
properties, are nevertheless very different in some respects: for which
reason almost every one of them requires a particular management, for
obtaining it with the greatest advantage possible, both as to quality
and quantity.

One of the first things requisite is, to chuse the proper time for
distilling the plant, from which you desire to extract the Essential
Oil; because the quantity of Oil varies considerably, according to
the season of the year, as well as the age of the plant. For example,
the most favourable time for obtaining these Oils from the leaves of
ever-green plants or trees, such as Thyme, Sage, Rosemary, the Orange,
the Bay, the Fir, &c. is the end of Autumn; because these vegetables
contain a great deal more Oil at that season than at any other. With
regard to annual plants, they must be chosen when in their prime, and
just before they begin to decline. The time therefore of gathering them
is when they begin to flower: and if you want to extract the Oil from
the flowers themselves, you must pull them just when they are newly
blown.

Secondly, it must be observed, that the Essential Oils of plants
are, as it were, the chief residence and reservoir of their odorous
principle; that they are to be found wherever that principle exists,
and never where it is not: so that what we said concerning the
_Spiritus Rector_ of plants is applicable here. It must be remembered,
that all the parts of some vegetables are odoriferous. Such plants may
be put into the alembic all together, and the Essential Oil distilled
from all their parts at once. But others, and indeed the greatest
number, have no odour, or at least none that is very perceptible,
except in some particular parts; as in their leaves, flowers, roots,
or seeds: therefore, when you want to have the Essential Oil of such a
plant, you must chuse that part in which the Odour resides. The sense
of smelling must be the artist's principal guide on this occasion.

Thirdly, all vegetables, and all the parts of vegetables, have not the
same texture: some are hard and compact, as woods, barks, and some
roots; others are tender and succulent, as most annual plants, and
some fruits. For this reason, they must be differently prepared for
distillation. It may be laid down as a general rule, that the closer
and more compact their texture is, the more they require to be opened
and divided, either by comminuting them into small particles, or by
digesting them a considerable time in water acuated with Salt.

Fourthly, though all Essential Oils be capable of rising in
distillation with the heat of boiling water, yet they have not all
an equal degree of levity and weight: on the contrary, they vary
exceedingly in this respect: some, as, for instance, those of all our
European aromatics, being lighter than water, so that they always float
on its surface; whereas others, such as those of Cloves, Sassafras,
&c. which are Indian aromatics, are heavier than water, and always
sink in it by their specific gravity. These differences therefore
require different methods of distillation. It is proper, for example,
to make use of a low alembic in distilling such Essential Oils as are
heavier than water; and, moreover, to facilitate their separation, by
applying a degree of heat somewhat stronger than that of boiling water.
This is easily done by impregnating the water with a proper quantity
of Sea-salt, or the Vitriolic Acid; for, the more saline matters are
contained in water, the more will the degree of heat it acquires, by
being brought to boil, exceed that of pure boiling water.

Fifthly, Essential Oils differ from one another in point of fluidity.
Some are as thin and as fluid as Spirit of Wine: of this number is the
Essential Oil of Turpentine. Others, again, are thick, and even congeal
as they cool: such, for instance, is the Oil of Roses. In distilling
Oils of this latter sort, care must be taken that the spout of the
alembic head do not grow too cold, but be kept always in such a degree
of warmth as may prevent the Oil from fixing in it, and stopping it up;
which would interrupt the distillation, and might also occasion some
other more considerable inconveniencies, of which we shall take notice
presently.

From what hath been said it appears, that the distillation of Essential
Oils cannot be regulated by any one general rule; but that the manner
of operating must be a little varied, according to the nature of the
Oil to be distilled, and to that of the vegetable from which it is to
be drawn.

The time of day fittest to gather plants for this distillation is the
morning before sun-rise; because the coolness of the night hath shut
all their pores, and concentrated their odour: whereas in the evening,
after the plants have been exposed all day to the heat of the sun,
their odorous principle is in a great measure dissipated, and they
are left almost quite exhausted of it. Now, the more of the odorous
principle the plants contain, the more Essential Oil will they yield,
and the more virtue will that Oil have.

Plants fresh gathered, and as yet full of moisture, do not yield so
much Oil in distillation as they do when dried; because the oily
particles in a very moist plant are more diffused, and even separated
from each other, by the interposition of the aqueous parts: whence
it comes to pass that, in distillation, they ascend in a state of
separation from each other; so that being dispersed through the water
they give it a milky colour, like that of an emulsion; and cannot unite
together but in small quantities, which hinders their being easily
separated from the water.

This inconvenience doth not happen, or at least is considerably less,
when the greatest part of the humidity of the plant is evaporated by
desiccation: for the oily particles, being thus delivered from the
intervening aqueous parts, which kept them separated from each other,
are brought nearer together, unite, and form little visible globules of
Oil, which easily emerge from the water employed in the distillation.
But, in drying plants from which the Essential Oil is to be extracted,
great care must be taken that they be neither exposed to the sun, nor
laid in a warm place; because the heat would carry off part of their
odour, and even, from some plants, a pretty considerable quantity of
their Essential Oil.

Plants of a loose texture, that easily give out their Essential Oils,
need not be comminuted, or macerated in water with Salt. But this
method must unavoidably be taken with such as are hard, and do not
readily part with their Oil. Woods, barks, roots, for instance, must be
first rasped, then set to macerate in water impregnated with Salt, as
before directed; and this sometimes for several weeks before they be
distilled.

On this occasion Salt procures three different advantages. In the
first place, it prevents the matters, that must stand in maceration
for some time, from running into fermentation: an inconvenience that
would considerably diminish the quantity of Essential Oil, or perhaps
rob us of the whole, by converting it into an Ardent Spirit, if the
fermentation were spirituous; or into a Volatile Alkali, if it went
on to the last stage, and as far as putrefaction. In the next place,
it acuates the water, and renders it more capable of penetrating and
properly dividing, during the maceration, the texture of the plant
which requires to be thus prepared. Lastly, it adds a little to the
heat of the boiling water, and so promotes the ascent of the heaviest
Oils.

Nevertheless, when you find it necessary, for the reasons assigned
above, to mix Salt with the water to be employed in distilling your
Essential Oil, you must be cautious of putting in too much. You will
indeed obtain, by means thereof, much more Oil than if you distilled
it without Salt: but, as a great quantity of Salt will make the water
acquire a much greater degree of heat than that of pure boiling water,
a good deal of the heavy Oil of the vegetable will be raised by such a
heat, mix with the Essential Oil, deprave it, and make it like those
that are adulterated with a mixture of some heterogeneous Oil, as will
be afterwards shewn.

When every thing is prepared for distillation, it is proper, as
directed in the process, to apply at once a flaming fire, brisk enough
to make the liquor boil immediately: for, if the water be kept long
heating before it be made to boil, the Essential Oil, which cannot rise
without the heat of boiling water, will, by a less degree of heat, be
only agitated, dashed about every way, and churned as it were; by which
means it will be divided into very minute particles, and dispersed in
the water, which will thence acquire a milky colour: and consequently
we shall fall into the inconvenience that was pointed out above, as
happening when we distil plants without having dried them, and while
they are loaded with all the moisture and sap that was in them when
fresh gathered.

When the water in the cucurbit boils, it will be known by the noise
that boiling water usually makes, which is produced by the numerous
bubbles that rise and burst on its surface. The spout of the alembic
is then so hot, that a man cannot lay his finger on it, without such a
sensation of burning heat as is not to be endured. With this degree of
heat the water distils in drops, which succeed each other so fast, that
they seem to form a continued small stream; and this water is replete
with much Essential Oil.

And now it is proper to weaken the fire considerably, so as to leave it
but just strong enough to keep the liquor gently boiling: for if the
distillation be urged too precipitately, the aqueous and oily vapours,
being forcibly hurried up by too great a heat, may carry along with
them some parts of the plant, which may stick in the spout, stop it
up, and endanger the bursting of the vessel, or at least the forcing
off its head, by the exceedingly rarefied particles of water, oil, and
air, all striving to escape at the same time; and these burning hot
vapours, being discharged with impetuosity, may not only scald the
operator, but injure his lungs.

In such distillations it is of consequence to keep constantly cooling
the head of the alembic, by frequency renewing the water in the
refrigeratory, in order to facilitate the condensation of the oily
particles. The water in the cooler ought to be renewed when it begins
to smoke very perceptibly.

Whatever care be taken to save as much of the Oil as possible, and
to prevent its being left dispersed in the water, yet some loss of
this kind cannot be totally avoided: and thus the water that rises
in distilling the Oil is always more or less milky, and strongly
scented, even after it is separated from the Essential Oil. Yet this
portion of the Oil and of the odorous principle, which is retained by
the water employed in such distillation, is not therefore lost: the
water impregnated with these principles partakes of the properties
of the plant from which the Essential Oil was drawn, and may be used
medicinally: it is known in Pharmacy by the title of the _Distilled
Water_ of the plant.

The same water may be used again, with advantage, in distilling the
Essential Oil of a fresh plant of the same sort; because the oily and
odorous particles, with which it is impregnated, joining with those
afforded by the fresh plant, form larger _moleculæ_, capable of uniting
more easily, and emerging better from the water; and consequently
they increase the quantity of Oil. Thus the same water may be always
employed in new distillations; and, the oftener it is used, with the
greater advantage may it be used again.

After all the Essential Oil is risen, if the distillation be continued,
and the receiver changed, the liquor that will then come off will not
be milky, but limpid. It will have no odour at all of the plant, but
a kind of sourish smell; and indeed it is a part of the Acid of the
vegetable in the still, which is elevated by the heat of boiling water,
after all the Essential Oil is come over.

If you intend to keep the distilled water which hath served as a
vehicle to the Essential Oil, and design it for medicinal use, great
care must be taken to stop the distillation before this acid phlegm
begin to rise: for, if it should mix with the distilled water, it would
spoil it, and hinder it from keeping; probably because it contains some
mucilaginous parts, which are apt to putrify.


PROCESS IV.

_To extract the Essential Oils of Plants by Distillation_ per Descensum.

Reduce to a powder, or a paste, the vegetable substances from which you
intend to extract the Essential Oil by the method proposed. Lay this
matter about half an inch thick on a fine, close, linen cloth. If it be
dry and hard, expose the cloth containing it to the steam of boiling
water, till the matter become moist and soft. Then lay the cloth, with
its contents, over the mouth of a very tall cylindrical glass vessel,
which is to do the office of a receiver in this distillation; and, by
means of a piece of small pack-thread, fasten down the extremities of
the cloth, by winding the thread several times over them and round the
vessel; in such a manner, however, that the cloth be not tight, but
may yield to a small weight, and sink about five or six lines deep
into the vessel over which it is fastened. Set this recipient in a
larger vessel, containing so much cold water as will reach half way up
the cylindrical vessel; which, having little in it but air, must be
ballasted with as much lead as will sink it to the bottom of the water.

On the cloth containing the substance to be distilled set a flat pan
of iron or copper, about five or six lines deep, that may just fit
the mouth of the glass vessel over which the cloth is fastened, so as
to shut it quite close. Fill this pan with hot ashes, and on these
lay some live coals. Soon after this, you will see vapours descend
from the cloth, which will fill the recipient, and drops of liquor
will be formed on the under side of the cloth, from whence they will
fall into the vessel. Keep up an equal gentle heat till you perceive
nothing more discharged. Then uncover the recipient: you will find in
it two distinct liquors; one of which is the phlegm, and the other the
Essential Oil of the substance distilled.


_OBSERVATIONS._

The apparatus for distilling above described is very convenient, when
we have not the vessels necessary for distilling with water, or when
we want to obtain the Essential Oil of any vegetable substance in much
less time. The aqueous and oily parts of the substances distilled in
this manner, being rarefied by the heat of the fire placed over them,
cannot ascend upwards, because they are close confined on that side;
and, moreover, the fire which rarefies them possessing all the upper
part of the vessel in which they are contained, they are forced to fly
from it to the place which most favours their condensation: and this
determines them to descend in the recipient, where they meet with a
coolness that condenses and fixes them. It was with a view to promote
this condensation, that we ordered the lower part of the recipient to
be sunk in cold water.

Cloves are one of those substances whose Essential Oil is best obtained
by this method. In the same way also may be drawn the Essential Oil
of Lemon-peel, Citron-peel, Orange-peel, Nutmegs, and several other
vegetable substances: but you must be cautious of applying too strong
a heat; for in that case the Oil, instead of being white and limpid,
acquires a red, dark-brown, blackish colour, is burnt, and smells of
empyreuma: and, on the other hand, if you do not apply a proper degree
of heat, you will scarce get any Oil at all. It is the surest, and
therefore the best, way to distil these Oils with water in an alembic.
And indeed the distillation _per descensum_ is seldom used, but out of
curiosity to try its effect, or on such pressing occasions as allow no
choice.


PROCESS V.

_Infusions, Decoctions, and Extracts of Plants._

Make some water boiling-hot, and then take it off the fire. When it
ceases to boil, pour it on the plant of which you desire to have
the Infusion; taking care there be enough of it to cover the plant
entirely. Cover the vessel, and let your plant lie in the hot water for
the space of half an hour, or longer, if it be of a firm close texture.
Then pour off the water by inclination: it will have partly acquired
the colour, the smell, the taste, and the virtues of the plant. This
liquor is called an _Infusion_.

To make the Decoction of a vegetable substance, put it into an
earthen pan, or into a tinned copper vessel, with a quantity of water
sufficient to bear being boiled for several hours, without leaving
any part of the plant dry. Boil your plant more or less according to
its nature; and then pour off the water by inclination. This water is
impregnated with several of the principles of the plant, of which we
shall take notice in the following observations.


_OBSERVATIONS._

Water, especially when boiling hot, is capable of dissolving not only
all that is purely saline in vegetables, but also a pretty considerable
quantity of their Oil and of their earth, which, by contracting an
union with the saline parts, have formed saponaceous, gummy, and
mucilaginous compounds, that are soluble in water. After violent and
long-continued boiling, therefore, there remains nothing in the plant
but the purest oily part, and such as is the most fixed, that is, the
most closely united with the earth of the plant. I say, the most fixed:
for some part of the oily matters, though not soluble in water, may be
separated by the action of boiling water, when those matters abound
greatly in the vegetable decocted; as we have seen happen to the Fat
Oils of certain vegetable matters; but in that case these oily matters
float upon the Decoction, and do not constitute a part of it.

From what we have already said, touching the analysis of plants, it
seems evident, that, if those decocted be odoriferous and contain an
Essential Oil, the Decoction will contain none, or at most but very
little, of their Essential Oil, or their odorous principle; seeing
we know that these substances cannot bear the heat of boiling water,
without being carried off and entirely dissipated by it. Therefore,
when we make a decoction of an aromatic plant, containing an Essential
Oil, we may be assured that it will not possess the virtues, either
of the odorous part, or of the Essential Oil, and that it will have
none but those of the other more fixed principles of the plant, with
which it may be impregnated. The Decoction of such a plant perfectly
resembles the water left in the cucurbit, after distilling its
Essential Oil. But for those plants in which there are no such volatile
parts, or whose virtue doth not reside in those principles, such as
astringent and emollient plants, for example, that owe their properties
wholly to an earthy Salt, or to a mucilage, they are capable of
communicating their whole virtue to the water in which they are infused
or decocted.

If, on one hand, the Salts of plants render some portion of the
principles of those plants soluble in water, such as part of their
Oil and their earth, which if they were pure would not dissolve
therein; on the other hand, these principles, being of their own
nature indissoluble in water, hinder the Salts, by the union they have
contracted together, from dissolving in it so easily, so soon, and in
such quantities, as if they were pure. This is so true, that water,
though boiled long and violently, is far from extracting out of plants
all those parts that it is capable of dissolving. If, after boiling a
plant in water, as directed in the process, this water be poured off,
fresh water added, and a second decoction made in the same manner as
the first, the water of this latter decoction will, by that means, be
almost as strongly impregnated with the principles of the plant as
the former was. Mr. Boerhaave was obliged to make twenty successive
decoctions of the same plant, to wit, Rosemary, before the water came
off the plant colourless and insipid; in a word, just as it was before
the plant was boiled in it.

Mr. Boerhaave observes, that a plant, after having thus given out all
that water can dissolve, still retains exactly the same form that it
had before it underwent any of the many boilings necessary to exhaust
it; that its colour, from being green at first, becomes brown; and
that the plant, which when green is lighter than water, or at least
doth not sink in it, is heavier after this operation, and falls to the
bottom. This is a proof that the water hath extracted out of the plant
its lightest substances, assuming their places itself, and that it hath
left nothing but its heaviest principles, namely, its fixed oil and its
earth. We shall afterwards examine more particularly these remains of
plants exhausted by water.

If the Infusions and Decoctions of plants be filtered, and evaporated
in a gentle heat, they become Extracts, that may be kept for whole
years, especially if they be evaporated to a thick consistence; and
better still if they be evaporated to dryness.

From what hath been said concerning the Infusions, Decoctions, and
Extracts of plants, it follows, 1. That Infusions and Decoctions of
aromatic plants do not furnish a complete Extract of those plants;
because they do not contain the volatile and odorous parts, in which
the principal virtue of such plants usually resides. If therefore you
desire to make Extracts of such vegetables, that shall have no defect,
you must employ their juices drawn by expression, or water impregnated
with their principles by the means of trituration, and evaporate
the liquor by spreading it over a great number of plates, in order
to enlarge its surface, and quicken the evaporation, which must be
effected by the heat of the sun alone, or the well-tempered warmth of a
stove.

2. It may also be inferred, that water alone, aided by the degree
of heat it is capable of acquiring by being made to boil, is not
sufficient to effect the complete analysis of a plant; since not
only some of its principles are still left combined in it, though
exhausted as much as it can be by boiling water; but also several of
the substances extracted from it by water are compounds of some of
the principles of the plant, and susceptible of a much more accurate
analysis; as we shall be convinced when we come to examine the effects
which a degree of heat superior to that of boiling water is able to
produce on entire plants, on their Extracts, and on their remains
exhausted as much as they can be by boiling water.

But before we enter on that part of the analysis, it is proper to
consider the experiments and combinations that may be made with the
principles we have already obtained; in order to discover their nature,
and in some measure analyze even them. Essential Oils in particular
deserve to be thus examined.

We also obtain from certain plants, with a degree of heat less than
that of boiling water, a Volatile Alkali, which exists formally in
them: but as these plants, when analyzed, yield principles different
from these we obtain out of all other vegetable substances, and as they
resemble animal matters, we shall refer their analysis to a distinct
chapter.



CHAP. V.

_Of_ OPERATIONS _on_ ESSENTIAL OILS.


PROCESS I.

_The Rectification of Essential Oils._

Put into a cucurbit the Essential Oil you propose to rectify. Set the
cucurbit in a _balneum mariæ_; fit to it a head of tin, or of copper
tinned, together with its refrigeratory; and lute on a receiver.
Make the water in the bath boil, and keep up this degree of heat
till nothing more will come over. When the distillation is finished,
you will find in the receiver a rectified Essential Oil, which will
be clearer, thinner, and better scented, than before it was thus
re-distilled; and in the bottom of the cucurbit will be left a matter
of a deeper colour, more tenacious, more resinous, and of a less
grateful smell.


_OBSERVATIONS._

Essential Oils, even the purest, the best prepared, and the thinnest,
suffer great changes, and are much impaired by growing old: they
gradually turn thick and resinous; their sweet grateful scent is lost,
and succeeded by a more disagreeable smell, somewhat like that of
Turpentine. The cause of these changes is, that their finest and most
volatile part, that which contains most of the odorous principle, is
dissipated and separated from that which contains least of it; which
therefore grows thicker, and comes so much the nearer to the nature
of a resin, as the quantity of Acid, that was distributed through the
whole Oil before the dissipation of the more volatile part is, after
such dissipation, united and concentrated in the heaviest part; the
Acid in Oils being much less volatile than the odorous part, to which
alone they owe their levity.

Hence it appears what precautions are to be used for preserving
Essential Oils, as long as possible, without spoiling. They must be
kept in a bottle perfectly well stopped, and always in a cool place,
because heat quickly dissipates the volatile parts. Some authors direct
the bottle to be kept under water.

If these Oils should grow thick and resinous by age, yet they are
not to be thrown away. We shall shew, in the analysis of Balsams and
Resins, that, from these thick and even solid substances, Essential
Oils may be drawn, as thin and as limpid as from plants. Essential
Oils, thickened by time, may therefore be treated like Balsams, and
actually analyzed, by separating all the subtile odorous matter they
contain from their thick acid parts. For this purpose they need only
be distilled with a degree of heat just sufficient to elevate the thin
odorous parts, without raising the thick matter.

The residue left at the bottom of the vessel, because it could not
rise in distillation, is much thicker and less odorous than the Oil
was before rectification. The reason of this is evident, and follows
from what hath just been said. This remainder dissolves in Spirit of
Wine more readily, and in greater quantity, than the light Oil drawn
from it; because it contains more Acid, and because Oils owe their
solubility in this menstruum to their Acid part, as is proved in our
Memoir on Oils already quoted.

When we come to treat of Resins, we shall inquire more particularly
what this remainder is, and what principles it yields when analyzed: in
this place it is sufficient to take notice, that though all the Oil of
which it made a part came over at first with the heat of boiling water,
yet it cannot now be raised by the same degree of heat in distillation;
because it is not now combined with the principle of odour which gives
the Oil its volatility, and because it is rendered sluggish by being
clogged with too great a proportion of Acid.

From what hath been already said, it must be concluded, that Essential
Oils suffer great diminution by being rectified; and that in proportion
to the quantity of resinous matter left behind. All this resinous
matter, while combined with a proper quantity of the odorous principle
of the plant, (that is, at the time of its being distilled, and a
little while after), was really an Essential Oil: the change of its
nature, therefore, is entirely owing to its having left that principle.

An Essential Oil, though rectified, is still as apt to change and be
spoiled as before, because it still continues to lose its odorous
principle by degrees. After some time, therefore, it requires a second
rectification, which again lessens its quantity. In short, it is plain
that Oils will, in a number of years, greater or smaller according to
their nature, and the manner in which they are kept, be wholly changed,
and metamorphosed into a resinous matter, from which no thin Oil can
be drawn with the heat of boiling water: and this is a proof of the
fugacity of that odorous principle, or _Spiritus Rector_, of plants,
which, when united with their lightest Oil, gives it the character of
an Essential Oil.

This resinous matter, to which Essential Oils are finally reduced,
being subjected to repeated distillations, with a degree of heat
superior to that of boiling water, is still capable of yielding a
certain portion of a thin, limpid, sweet-scented Oil, which is as light
as an Essential Oil; as we observed before is the case with Fat Oils
drawn by expression: but the thin Oil obtained by this means, though it
possesses almost all the properties of an Essential Oil, is not for all
that a genuine one; seeing it hath not the same odour with the plant
from which it was originally drawn.

Essential Oils must be rectified in the _balneum mariæ_, as ordered in
the process: for, as some of the Oil touches the sides of the vessel in
the operation, if that vessel be made hotter than boiling water, the
thick matter will rise with the thin Oil, which therefore will not be
rectified.

Rectification is of use not only for procuring to Essential Oils the
tenuity and levity they may have lost by age, but also to separate
them from other oily matters with which they may be adulterated. If,
for instance, an Essential Oil be not properly distilled; if, by
the addition of too much Salt, the water have acquired a degree of
heat greater than that of pure boiling water, and if, in consequence
thereof, some of the heavy Oil of the plant have risen with the
Essential Oil, and mixed therewith, the Essential Oil may, by
rectification, be separated from this heterogeneous Oil; which, being
heavier and incapable of rising with the heat of pure boiling water,
will remain at the bottom of the vessel.

The effect will be the same, if your Essential Oil be falsified with a
mixture of any Fat Oil, as is often the case: for, some of them being
extremely dear, the vender frequently adds a portion of Fat Oil to
increase the quantity. For this purpose Oil of Ben is generally used.

When an Essential Oil is thus falsified with a mixture of any Fat Oil,
it may be discovered by letting a few drops of it fall into rectified
Spirit of Wine; which will dissolve the Essential Oil only, leaving the
Fat Oil quite untouched.

Essential Oils are sometimes falsified by mixing them with a certain
quantity of Spirit of Wine. This fraud doth not render their smell
less fragrant: on the contrary, it becomes rather more agreeable
and quicker. In order to try an Oil suspected of being falsified in
this manner, drop a little of it into very clear water. If a milky
cloud appear in the water, be assured the Oil is mixed with Spirit
of Wine: for as this liquor unites more readily with water than with
Oil, it quits the Oil with which it was mixed to incorporate with the
water: mean time a good deal of the Oil that was dissolved by the
Spirit of Wine, and is now separated from it by the intervention of
water, necessarily remains dispersed through this water in very small
particles; and these form the milky cloud produced on this occasion.

An Essential Oil may also be adulterated with another Essential Oil
that is much more common, and of much less value. Those who practise
this fraud generally employ Oil of Turpentine for that purpose, on
account of its cheapness and tenuity. The cheat is easily discovered,
by moistening a linen rag with the Oil supposed to be thus falsified,
and then holding the rag a little before the fire, which presently
dissipates the odorous part of the falsified Oil. This odour, which
prevented our distinguishing that of the Oil of Turpentine, being
vanished, the peculiar smell of the Turpentine, which is much more
permanent, remains alone; and is so perceptible that it cannot easily
be mistaken.

Those who are much accustomed to see and examine Essential Oils,
have seldom occasion to make the experiments here proposed for
discovering their qualities. A certain degree of thickness, partaking
of unctuosity, in an Essential Oil, convinces them that it is falsified
with a Fat Oil: on the other hand, a greater degree of tenuity,
together with a quicker smell, than a pure Essential Oil ought to have,
discovers the admixture of Spirit of Wine. Lastly, any one, whose sense
of smelling is not very dull, will easily discover the odour of the Oil
of Turpentine, though disguised by that of the Essential Oil with which
it is mixed.


PROCESS II.

_To fire Oils by combining them with highly concentrated Acids:
instanced in Oil of Turpentine._

Mix together, in a glass, equal parts of concentrated Oil of Vitriol,
and highly smoking fresh-drawn Spirit of Nitre: pour this mixture at
several times, but suddenly, on three parts of Oil of Turpentine, set
for that purpose in a glass bason. By a part here must be understood a
dram at least. A most violent commotion, accompanied with smoke, will
immediately be raised in the liquors, and the whole will take fire in
an instant, flame, and be consumed.


_OBSERVATIONS._

There is not in Chymistry a phenomenon more extraordinary, and more
surprising, than the firing of Oils by mixing them with Acids. It
could never have been suspected that a mixture of two cold liquors
would produce a sudden, violent, bright, and lasting flame, like that
we are at present considering. Beccher gave notice, in his _Physica
subterranea_, that highly rectified Spirit of Wine would be set on fire
by mixing it with highly concentrated Oil of Vitriol.

Afterwards Borrichius, a Danish Chymist, published a process for
kindling Oil of Turpentine, by mixing it with the Nitrous Acid, as
we find in the Philosophical Transactions of Copenhagen for the year
1671. Most Chymists have since tried to repeat those experiments, and
particularly to fire the Oil of Turpentine by mixing it with Oil of
Vitriol, or Spirit of Nitre; but to no purpose, when they made use of
the Oil of Vitriol, till Mr. Homberg told us, in the Memoirs of the
Academy of Sciences for 1701, that he had fired Oil of Turpentine by
mixing it with Oil of Vitriol.

To make the experiment succeed he requires, "That the Oil of Vitriol
be dephlegmated as much as possible, and that the Oil of Turpentine be
the last that comes over in distillation, which is thick like a syrop,
and of a dark-brown colour; for that which is white, and rises at the
beginning of the distillation, never takes fire." These are his own
words: but no body else hath ever succeeded in making the experiment.

Tournefort had succeeded, a little before Homberg, in firing, not
Oil of Turpentine indeed, in which he always failed, but the Oil of
Sassafras, by mixing it with an equal quantity of well dephlegmated
Spirit of Nitre. Homberg came afterwards, as appears by the Memoirs
of the Academy for the year 1702, to fire with Spirit of Nitre the
Essential Oils of the aromatic plants of India; and in 1706 Mr.
Rouviere fired, with Spirit of Nitre, the empyreumatic Oil of Guaiacum.
While this Oil of Guaiacum is burning, a porous spongy body rises from
the midst of the flame, to the height of about two feet above the
vessel.

Lastly, several years after all these discoveries, Messrs. Geoffroy and
Hoffman, the one at Paris, and the other at Hall in Saxony, found a way
to fire the Æthereal Oil of Turpentine, each by a different process;
yet agreeing in this, that they both combined the Vitriolic Acid with
the Nitrous, and with this compound Acid fired that Æthereal Essential
Oil, which is one of the thinnest, and, probably for that very reason,
the most unfit to produce a flame with Acids.

The most celebrated Chymists, as appears from this short account, have
employed themselves in firing Essential Oils; but no body attempted the
experiment on Fat Oils. It was not so much as suspected that they were
capable of taking fire after this manner, till in 1745 I read before
the Academy a Memoir on Oils, which I have already mentioned, and in
which I express myself thus:

"I put two ounces and a half of Walnut Oil into the bottom part of a
broken retort, having the figure of a cap, or concave hemisphere; and
poured thereon two ounces of smoking Spirit of Nitre. It was scarce
put in when a considerable ebullition arose, with a very thick smoke.
As I found it continually increasing, and very fast too, I retired a
little, that I might observe the event without dan