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Title: Elements of Chemistry, - In a New Systematic Order, Containing all the Modern Discoveries
Author: Lavoisier, Antoine, 1743-1794
Language: English
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*** Start of this LibraryBlog Digital Book "Elements of Chemistry, - In a New Systematic Order, Containing all the Modern Discoveries" ***
ELEMENTS
OF
CHEMISTRY,
IN A
NEW SYSTEMATIC ORDER,
CONTAINING ALL THE
MODERN DISCOVERIES.
ILLUSTRATED WITH THIRTEEN COPPERPLATES.
BY MR LAVOISIER,
Member of the Academy of Sciences, Royal Society of Medicine, and
Agricultural Society of Paris, of the Royal Society of London, and
Philosophical Societies of Orleans, Bologna, Basil, Philadelphia,
Haerlem, Manchester, &c. &c.
TRANSLATED FROM THE FRENCH,
BY ROBERT KERR, F.R. & A.SS.E.
Member of the Royal College of Surgeons, and Surgeon to the Orphan
Hospital of Edinburgh.
EDINBURGH: PRINTED FOR WILLIAM CREECH, AND SOLD IN LONDON BY G. G. AND
J. J. ROBINSONS.
MDCCXC.
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Transcriber's note: Tables needed to be split to fit space
constraints. Minor typos have been corrected and footnotes moved to the
end of the chapters. The italic markup for single italized
letters (such as variables in equations) and weight abbreviations are
deleted for easier reading.
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ADVERTISEMENT OF THE TRANSLATOR.
The very high character of Mr Lavoisier as a chemical philosopher, and
the great revolution which, in the opinion of many excellent chemists,
he has effected in the theory of chemistry, has long made it much
desired to have a connected account of his discoveries, and of the new
theory he has founded upon the modern experiments written by himself.
This is now accomplished by the publication of his Elements of
Chemistry; therefore no excuse can be at all necessary for giving the
following work to the public in an English dress; and the only
hesitation of the Translator is with regard to his own abilities for the
task. He is most ready to confess, that his knowledge of the composition
of language fit for publication is far inferior to his attachment to
the subject, and to his desire of appearing decently before the judgment
of the world.
He has earnestly endeavoured to give the meaning of the Author with the
most scrupulous fidelity, having paid infinitely greater attention to
accuracy of translation than to elegance of stile. This last indeed, had
he even, by proper labour, been capable of attaining, he has been
obliged, for very obvious reasons, to neglect, far more than accorded
with his wishes. The French copy did not reach his hands before the
middle of September; and it was judged necessary by the Publisher that
the Translation should be ready by the commencement of the University
Session at the end of October.
He at first intended to have changed all the weights and measures used
by Mr Lavoisier into their correspondent English denominations, but,
upon trial, the task was found infinitely too great for the time
allowed; and to have executed this part of the work inaccurately, must
have been both useless and misleading to the reader. All that has been
attempted in this way is adding, between brackets ( ), the degrees of
Fahrenheit's scale corresponding with those of Reaumeur's thermometer,
which is used by the Author. Rules are added, however, in the Appendix,
for converting the French weights and measures into English, by which
means the reader may at any time calculate such quantities as occur,
when desirous of comparing Mr Lavoisier's experiments with those of
British authors.
By an oversight, the first part of the translation went to press without
any distinction being preserved between charcoal and its simple
elementary part, which enters into chemical combinations, especially
with oxygen or the acidifying principle, forming carbonic acid. This
pure element, which exists in great plenty in well made charcoal, is
named by Mr Lavoisier _carbone_, and ought to have been so in the
translation; but the attentive reader can very easily rectify the
mistake. There is an error in Plate XI. which the engraver copied
strictly from the original, and which was not discovered until the plate
was worked off at press, when that part of the Elements which treats of
the apparatus there represented came to be translated. The two tubes 21.
and 24. by which the gas is conveyed into the bottles of alkaline
solution 22. 25. should have been made to dip into the liquor, while the
other tubes 23. and 26. which carry off the gas, ought to have been cut
off some way above the surface of the liquor in the bottles.
A few explanatory notes are added; and indeed, from the perspicuity of
the Author, very few were found necessary. In a very small number of
places, the liberty has been taken of throwing to the bottom of the
page, in notes, some parenthetical expressions, only relative to the
subject, which, in their original place, tended to confuse the sense.
These, and the original notes of the Author, are distinguished by the
letter A, and to the few which the Translator has ventured to add, the
letter E is subjoined.
Mr Lavoisier has added, in an Appendix, several very useful Tables for
facilitating the calculations now necessary in the advanced state of
modern chemistry, wherein the most scrupulous accuracy is required. It
is proper to give some account of these, and of the reasons for omitting
several of them.
No. I. of the French Appendix is a Table for converting ounces, gros,
and grains, into the decimal fractions of the French pound; and No. II.
for reducing these decimal fractions again into the vulgar subdivisions.
No. III. contains the number of French cubical inches and decimals which
correspond to a determinate weight of water.
The Translator would most readily have converted these Tables into
English weights and measures; but the necessary calculations must have
occupied a great deal more time than could have been spared in the
period limited for publication. They are therefore omitted, as
altogether useless, in their present state, to the British chemist.
No. IV. is a Table for converting lines or twelfth parts of the inch,
and twelfth parts of lines, into decimal fractions, chiefly for the
purpose of making the necessary corrections upon the quantities of
gasses according to their barometrical pressure. This can hardly be at
all useful or necessary, as the barometers used in Britain are graduated
in decimal fractions of the inch, but, being referred to by the Author
in the text, it has been retained, and is No. I. of the Appendix to
this Translation.
No. V. Is a Table for converting the observed heights of water within
the jars used in pneumato-chemical experiments into correspondent
heights of mercury for correcting the volume of gasses. This, in Mr
Lavoisier's Work, is expressed for the water in lines, and for the
mercury in decimals of the inch, and consequently, for the reasons given
respecting the Fourth Table, must have been of no use. The Translator
has therefore calculated a Table for this correction, in which the water
is expressed in decimals, as well as the mercury. This Table is No. II.
of the English Appendix.
No. VI. contains the number of French cubical inches and decimals
contained in the corresponding ounce-measures used in the experiments of
our celebrated countryman Dr Priestley. This Table, which forms No. III.
of the English Appendix, is retained, with the addition of a column, in
which the corresponding English cubical inches and decimals are
expressed.
No. VII. Is a Table of the weights of a cubical foot and inch, French
measure, of the different gasses expressed in French ounces, gros,
grains, and decimals. This, which forms No. VI. of the English Appendix,
has been, with considerable labour, calculated into English weight and
measure.
No. VIII. Gives the specific gravities of a great number of bodies, with
columns, containing the weights of a cubical foot and inch, French
measure, of all the substances. The specific gravities of this Table,
which is No. VII. of the English Appendix, are retained, but the
additional columns, as useless to the British philosopher, are omitted;
and to have converted these into English denominations must have
required very long and painful calculations.
Rules are subjoined, in the Appendix to this translation, for converting
all the weights and measures used by Mr Lavoisier into corresponding
English denominations; and the Translator is proud to acknowledge his
obligation to the learned Professor of Natural Philosophy in the
University of Edinburgh, who kindly supplied him with the necessary
information for this purpose. A Table is likewise added, No. IV. of the
English Appendix, for converting the degrees of Reaumeur's scale used by
Mr Lavoisier into the corresponding degrees of Fahrenheit, which is
universally employed in Britain[1].
This Translation is sent into the world with the utmost diffidence,
tempered, however, with this consolation, that, though it must fall
greatly short of the elegance, or even propriety of language, which
every writer ought to endeavour to attain, it cannot fail of advancing
the interests of true chemical science, by disseminating the accurate
mode of analysis adopted by its justly celebrated Author. Should the
public call for a second edition, every care shall be taken to correct
the forced imperfections of the present translation, and to improve the
work by valuable additional matter from other authors of reputation in
the several subjects treated of.
EDINBURGH, }
Oct. 23. 1789. }
FOOTNOTES:
[1] The Translator has since been enabled, by the kind assistance of the
gentleman above alluded to, to give Tables, of the same nature with
those of Mr Lavoisier, for facilitating the calculations of the results
of chemical experiments.
PREFACE OF THE AUTHOR.
When I began the following Work, my only object was to extend and
explain more fully the Memoir which I read at the public meeting of the
Academy of Sciences in the month of April 1787, on the necessity of
reforming and completing the Nomenclature of Chemistry. While engaged in
this employment, I perceived, better than I had ever done before, the
justice of the following maxims of the Abbé de Condillac, in his System
of Logic, and some other of his works.
"We think only through the medium of words.--Languages are true
analytical methods.--Algebra, which is adapted to its purpose in every
species of expression, in the most simple, most exact, and best manner
possible, is at the same time a language and an analytical method.--The
art of reasoning is nothing more than a language well arranged."
Thus, while I thought myself employed only in forming a Nomenclature,
and while I proposed to myself nothing more than to improve the chemical
language, my work transformed itself by degrees, without my being able
to prevent it, into a treatise upon the Elements of Chemistry.
The impossibility of separating the nomenclature of a science from the
science itself, is owing to this, that every branch of physical science
must consist of three things; the series of facts which are the objects
of the science, the ideas which represent these facts, and the words by
which these ideas are expressed. Like three impressions of the same
seal, the word ought to produce the idea, and the idea to be a picture
of the fact. And, as ideas are preserved and communicated by means of
words, it necessarily follows that we cannot improve the language of
any science without at the same time improving the science itself;
neither can we, on the other hand, improve a science, without improving
the language or nomenclature which belongs to it. However certain the
facts of any science may be, and, however just the ideas we may have
formed of these facts, we can only communicate false impressions to
others, while we want words by which these may be properly expressed.
To those who will consider it with attention, the first part of this
treatise will afford frequent proofs of the truth of the above
observations. But as, in the conduct of my work, I have been obliged to
observe an order of arrangement essentially differing from what has been
adopted in any other chemical work yet published, it is proper that I
should explain the motives which have led me to do so.
It is a maxim universally admitted in geometry, and indeed in every
branch of knowledge, that, in the progress of investigation, we should
proceed from known facts to what is unknown. In early infancy, our ideas
spring from our wants; the sensation of want excites the idea of the
object by which it is to be gratified. In this manner, from a series of
sensations, observations, and analyses, a successive train of ideas
arises, so linked together, that an attentive observer may trace back to
a certain point the order and connection of the whole sum of human
knowledge.
When we begin the study of any science, we are in a situation,
respecting that science, similar to that of children; and the course by
which we have to advance is precisely the same which Nature follows in
the formation of their ideas. In a child, the idea is merely an effect
produced by a sensation; and, in the same manner, in commencing the
study of a physical science, we ought to form no idea but what is a
necessary consequence, and immediate effect, of an experiment or
observation. Besides, he that enters upon the career of science, is in a
less advantageous situation than a child who is acquiring his first
ideas. To the child, Nature gives various means of rectifying any
mistakes he may commit respecting the salutary or hurtful qualities of
the objects which surround him. On every occasion his judgments are
corrected by experience; want and pain are the necessary consequences
arising from false judgment; gratification and pleasure are produced by
judging aright. Under such masters, we cannot fail to become well
informed; and we soon learn to reason justly, when want and pain are the
necessary consequences of a contrary conduct.
In the study and practice of the sciences it is quite different; the
false judgments we form neither affect our existence nor our welfare;
and we are not forced by any physical necessity to correct them.
Imagination, on the contrary, which is ever wandering beyond the bounds
of truth, joined to self-love and that self-confidence we are so apt to
indulge, prompt us to draw conclusions which are not immediately derived
from facts; so that we become in some measure interested in deceiving
ourselves. Hence it is by no means to be wondered, that, in the science
of physics in general, men have often made suppositions, instead of
forming conclusions. These suppositions, handed down from one age to
another, acquire additional weight from the authorities by which they
are supported, till at last they are received, even by men of genius, as
fundamental truths.
The only method of preventing such errors from taking place, and of
correcting them when formed, is to restrain and simplify our reasoning
as much as possible. This depends entirely upon ourselves, and the
neglect of it is the only source of our mistakes. We must trust to
nothing but facts: These are presented to us by Nature, and cannot
deceive. We ought, in every instance, to submit our reasoning to the
test of experiment, and never to search for truth but by the natural
road of experiment and observation. Thus mathematicians obtain the
solution of a problem by the mere arrangement of data, and by reducing
their reasoning to such simple steps, to conclusions so very obvious, as
never to lose sight of the evidence which guides them.
Thoroughly convinced of these truths, I have imposed upon myself, as a
law, never to advance but from what is known to what is unknown; never
to form any conclusion which is not an immediate consequence necessarily
flowing from observation and experiment; and always to arrange the
facts, and the conclusions which are drawn from them, in such an order
as shall render it most easy for beginners in the study of chemistry
thoroughly to understand them. Hence I have been obliged to depart from
the usual order of courses of lectures and of treatises upon chemistry,
which always assume the first principles of the science, as known, when
the pupil or the reader should never be supposed to know them till they
have been explained in subsequent lessons. In almost every instance,
these begin by treating of the elements of matter, and by explaining the
table of affinities, without considering, that, in so doing, they must
bring the principal phenomena of chemistry into view at the very outset:
They make use of terms which have not been defined, and suppose the
science to be understood by the very persons they are only beginning to
teach. It ought likewise to be considered, that very little of chemistry
can be learned in a first course, which is hardly sufficient to make the
language of the science familiar to the ears, or the apparatus familiar
to the eyes. It is almost impossible to become a chemist in less than
three or four years of constant application.
These inconveniencies are occasioned not so much by the nature of the
subject, as by the method of teaching it; and, to avoid them, I was
chiefly induced to adopt a new arrangement of chemistry, which appeared
to me more consonant to the order of Nature. I acknowledge, however,
that in thus endeavouring to avoid difficulties of one kind, I have
found myself involved in others of a different species, some of which I
have not been able to remove; but I am persuaded, that such as remain do
not arise from the nature of the order I have adopted, but are rather
consequences of the imperfection under which chemistry still labours.
This science still has many chasms, which interrupt the series of facts,
and often render it extremely difficult to reconcile them with each
other: It has not, like the elements of geometry, the advantage of being
a complete science, the parts of which are all closely connected
together: Its actual progress, however, is so rapid, and the facts,
under the modern doctrine, have assumed so happy an arrangement, that we
have ground to hope, even in our own times, to see it approach near to
the highest state of perfection of which it is susceptible.
The rigorous law from which I have never deviated, of forming no
conclusions which are not fully warranted by experiment, and of never
supplying the absence of facts, has prevented me from comprehending in
this work the branch of chemistry which treats of affinities, although
it is perhaps the best calculated of any part of chemistry for being
reduced into a completely systematic body. Messrs Geoffroy, Gellert,
Bergman, Scheele, De Morveau, Kirwan, and many others, have collected a
number of particular facts upon this subject, which only wait for a
proper arrangement; but the principal data are still wanting, or, at
least, those we have are either not sufficiently defined, or not
sufficiently proved, to become the foundation upon which to build so
very important a branch of chemistry. This science of affinities, or
elective attractions, holds the same place with regard to the other
branches of chemistry, as the higher or transcendental geometry does
with respect to the simpler and elementary part; and I thought it
improper to involve those simple and plain elements, which I flatter
myself the greatest part of my readers will easily understand, in the
obscurities and difficulties which still attend that other very useful
and necessary branch of chemical science.
Perhaps a sentiment of self-love may, without my perceiving it, have
given additional force to these reflections. Mr de Morveau is at
present engaged in publishing the article _Affinity_ in the Methodical
Encyclopædia; and I had more reasons than one to decline entering upon a
work in which he is employed.
It will, no doubt, be a matter of surprise, that in a treatise upon the
elements of chemistry, there should be no chapter on the constituent and
elementary parts of matter; but I shall take occasion, in this place, to
remark, that the fondness for reducing all the bodies in nature to three
or four elements, proceeds from a prejudice which has descended to us
from the Greek Philosophers. The notion of four elements, which, by the
variety of their proportions, compose all the known substances in
nature, is a mere hypothesis, assumed long before the first principles
of experimental philosophy or of chemistry had any existence. In those
days, without possessing facts, they framed systems; while we, who have
collected facts, seem determined to reject them, when they do not agree
with our prejudices. The authority of these fathers of human philosophy
still carry great weight, and there is reason to fear that it will even
bear hard upon generations yet to come.
It is very remarkable, that, notwithstanding of the number of
philosophical chemists who have supported the doctrine of the four
elements, there is not one who has not been led by the evidence of facts
to admit a greater number of elements into their theory. The first
chemists that wrote after the revival of letters, considered sulphur and
salt as elementary substances entering into the composition of a great
number of substances; hence, instead of four, they admitted the
existence of six elements. Beccher assumes the existence of three kinds
of earth, from the combination of which, in different proportions, he
supposed all the varieties of metallic substances to be produced. Stahl
gave a new modification to this system; and succeeding chemists have
taken the liberty to make or to imagine changes and additions of a
similar nature. All these chemists were carried along by the influence
of the genius of the age in which they lived, which contented itself
with assertions without proofs; or, at least, often admitted as proofs
the slighted degrees of probability, unsupported by that strictly
rigorous analysis required by modern philosophy.
All that can be said upon the number and nature of elements is, in my
opinion, confined to discussions entirely of a metaphysical nature. The
subject only furnishes us with indefinite problems, which may be solved
in a thousand different ways, not one of which, in all probability, is
consistent with nature. I shall therefore only add upon this subject,
that if, by the term _elements_, we mean to express those simple and
indivisible atoms of which matter is composed, it is extremely probable
we know nothing at all about them; but, if we apply the term _elements_,
or _principles of bodies_, to express our idea of the last point which
analysis is capable of reaching, we must admit, as elements, all the
substances into which we are capable, by any means, to reduce bodies by
decomposition. Not that we are entitled to affirm, that these substances
we consider as simple may not be compounded of two, or even of a greater
number of principles; but, since these principles cannot be separated,
or rather since we have not hitherto discovered the means of separating
them, they act with regard to us as simple substances, and we ought
never to suppose them compounded until experiment and observation has
proved them to be so.
The foregoing reflections upon the progress of chemical ideas naturally
apply to the words by which these ideas are to be expressed. Guided by
the work which, in the year 1787, Messrs de Morveau, Berthollet, de
Fourcroy, and I composed upon the Nomenclature of Chemistry, I have
endeavoured, as much as possible, to denominate simple bodies by simple
terms, and I was naturally led to name these first. It will be
recollected, that we were obliged to retain that name of any substance
by which it had been long known in the world, and that in two cases only
we took the liberty of making alterations; first, in the case of those
which were but newly discovered, and had not yet obtained names, or at
least which had been known but for a short time, and the names of which
had not yet received the sanction of the public; and, secondly, when the
names which had been adopted, whether by the ancients or the moderns,
appeared to us to express evidently false ideas, when they confounded
the substances, to which they were applied, with others possessed of
different, or perhaps opposite qualities. We made no scruple, in this
case, of substituting other names in their room, and the greatest number
of these were borrowed from the Greek language. We endeavoured to frame
them in such a manner as to express the most general and the most
characteristic quality of the substances; and this was attended with the
additional advantage both of assisting the memory of beginners, who find
it difficult to remember a new word which has no meaning, and of
accustoming them early to admit no word without connecting with it some
determinate idea.
To those bodies which are formed by the union of several simple
substances we gave new names, compounded in such a manner as the nature
of the substances directed; but, as the number of double combinations is
already very considerable, the only method by which we could avoid
confusion, was to divide them into classes. In the natural order of
ideas, the name of the class or genus is that which expresses a quality
common to a great number of individuals: The name of the species, on the
contrary, expresses a quality peculiar to certain individuals only.
These distinctions are not, as some may imagine, merely metaphysical,
but are established by Nature. "A child," says the Abbé de Condillac,
"is taught to give the name _tree_ to the first one which is pointed out
to him. The next one he sees presents the same idea, and he gives it the
same name. This he does likewise to a third and a fourth, till at last
the word _tree_, which he first applied to an individual, comes to be
employed by him as the name of a class or a genus, an abstract idea,
which comprehends all trees in general. But, when he learns that all
trees serve not the same purpose, that they do not all produce the same
kind of fruit, he will soon learn to distinguish them by specific and
particular names." This is the logic of all the sciences, and is
naturally applied to chemistry.
The acids, for example, are compounded of two substances, of the order
of those which we consider as simple; the one constitutes acidity, and
is common to all acids, and, from this substance, the name of the class
or the genus ought to be taken; the other is peculiar to each acid, and
distinguishes it from the rest, and from this substance is to be taken
the name of the species. But, in the greatest number of acids, the two
constituent elements, the acidifying principle, and that which it
acidifies, may exist in different proportions, constituting all the
possible points of equilibrium or of saturation. This is the case in the
sulphuric and the sulphurous acids; and these two states of the same
acid we have marked by varying the termination of the specific name.
Metallic substances which have been exposed to the joint action of the
air and of fire, lose their metallic lustre, increase in weight, and
assume an earthy appearance. In this state, like the acids, they are
compounded of a principle which is common to all, and one which is
peculiar to each. In the same way, therefore, we have thought proper to
class them under a generic name, derived from the common principle; for
which purpose, we adopted the term _oxyd_; and we distinguish them from
each other by the particular name of the metal to which each belongs.
Combustible substances, which in acids and metallic oxyds are a specific
and particular principle, are capable of becoming, in their turn, common
principles of a great number of substances. The sulphurous combinations
have been long the only known ones in this kind. Now, however, we know,
from the experiments of Messrs Vandermonde, Monge, and Berthollet, that
charcoal may be combined with iron, and perhaps with several other
metals; and that, from this combination, according to the proportions,
may be produced steel, plumbago, &c. We know likewise, from the
experiments of M. Pelletier, that phosphorus may be combined with a
great number of metallic substances. These different combinations we
have classed under generic names taken from the common substance, with a
termination which marks this analogy, specifying them by another name
taken from that substance which is proper to each.
The nomenclature of bodies compounded of three simple substances was
attended with still greater difficulty, not only on account of their
number, but, particularly, because we cannot express the nature of their
constituent principles without employing more compound names. In the
bodies which form this class, such as the neutral salts, for instance,
we had to consider, 1st, The acidifying principle, which is common to
them all; 2d, The acidifiable principle which constitutes their peculiar
acid; 3d, The saline, earthy, or metallic basis, which determines the
particular species of salt. Here we derived the name of each class of
salts from the name of the acidifiable principle common to all the
individuals of that class; and distinguished each species by the name of
the saline, earthy, or metallic basis, which is peculiar to it.
A salt, though compounded of the same three principles, may,
nevertheless, by the mere difference of their proportion, be in three
different states. The nomenclature we have adopted would have been
defective, had it not expressed these different states; and this we
attained chiefly by changes of termination uniformly applied to the same
state of the different salts.
In short, we have advanced so far, that from the name alone may be
instantly found what the combustible substance is which enters into any
combination; whether that combustible substance be combined with the
acidifying principle, and in what proportion; what is the state of the
acid; with what basis it is united; whether the saturation be exact, or
whether the acid or the basis be in excess.
It may be easily supposed that it was not possible to attain all these
different objects without departing, in some instances, from established
custom, and adopting terms which at first sight will appear uncouth and
barbarous. But we considered that the ear is soon habituated to new
words, especially when they are connected with a general and rational
system. The names, besides, which were formerly employed, such as
_powder of algaroth_, _salt of alembroth_, _pompholix_, _phagadenic
water_, _turbith mineral_, _colcathar_, and many others, were neither
less barbarous nor less uncommon. It required a great deal of practice,
and no small degree of memory, to recollect the substances to which they
were applied, much more to recollect the genus of combination to which
they belonged. The names of _oil of tartar per deliquium_, _oil of
vitriol_, _butter of arsenic and of antimony_, _flowers of zinc_, &c.
were still more improper, because they suggested false ideas: For, in
the whole mineral kingdom, and particularly in the metallic class, there
exists no such thing as butters, oils, or flowers; and, in short, the
substances to which they give these fallacious names, are nothing less
than rank poisons.
When we published our essay on the nomenclature of chemistry, we were
reproached for having changed the language which was spoken by our
masters, which they distinguished by their authority, and handed down to
us. But those who reproach us on this account, have forgotten that it
was Bergman and Macquer themselves who urged us to make this
reformation. In a letter which the learned Professor of Upsal, M.
Bergman, wrote, a short time before he died, to M. de Morveau, he bids
him _spare no improper names; those who are learned, will always be
learned, and those who are ignorant will thus learn sooner_.
There is an objection to the work which I am going to present to the
public, which is perhaps better founded, that I have given no account of
the opinion of those who have gone before me; that I have stated only my
own opinion, without examining that of others. By this I have been
prevented from doing that justice to my associates, and more especially
to foreign chemists, which I wished to render them. But I beseech the
reader to consider, that, if I had filled an elementary work with a
multitude of quotations; if I had allowed myself to enter into long
dissertations on the history of the science, and the works of those who
have studied it, I must have lost sight of the true object I had in
view, and produced a work, the reading of which must have been extremely
tiresome to beginners. It is not to the history of the science, or of
the human mind, that we are to attend in an elementary treatise: Our
only aim ought to be ease and perspicuity, and with the utmost care to
keep every thing out of view which might draw aside the attention of the
student; it is a road which we should be continually rendering more
smooth, and from which we should endeavour to remove every obstacle
which can occasion delay. The sciences, from their own nature, present a
sufficient number of difficulties, though we add not those which are
foreign to them. But, besides this, chemists will easily perceive, that,
in the first part of my work, I make very little use of any experiments
but those which were made by myself: If at any time I have adopted,
without acknowledgment, the experiments or the opinions of M.
Berthollet, M. Fourcroy, M. de la Place, M. Monge, or, in general, of
any of those whose principles are the same with my own, it is owing to
this circumstance, that frequent intercourse, and the habit of
communicating our ideas, our observations, and our way of thinking to
each other, has established between us a sort of community of opinions,
in which it is often difficult for every one to know his own.
The remarks I have made on the order which I thought myself obliged to
follow in the arrangement of proofs and ideas, are to be applied only to
the first part of this work. It is the only one which contains the
general sum of the doctrine I have adopted, and to which I wished to
give a form completely elementary.
The second part is composed chiefly of tables of the nomenclature of the
neutral salts. To these I have only added general explanations, the
object of which was to point out the most simple processes for obtaining
the different kinds of known acids. This part contains nothing which I
can call my own, and presents only a very short abridgment of the
results of these processes, extracted from the works of different
authors.
In the third part, I have given a description, in detail, of all the
operations connected with modern chemistry. I have long thought that a
work of this kind was much wanted, and I am convinced it will not be
without use. The method of performing experiments, and particularly
those of modern chemistry, is not so generally known as it ought to be;
and had I, in the different memoirs which I have presented to the
Academy, been more particular in the detail of the manipulations of my
experiments, it is probable I should have made myself better understood,
and the science might have made a more rapid progress. The order of the
different matters contained in this third part appeared to me to be
almost arbitrary; and the only one I have observed was to class
together, in each of the chapters of which it is composed, those
operations which are most connected with one another. I need hardly
mention that this part could not be borrowed from any other work, and
that, in the principal articles it contains, I could not derive
assistance from any thing but the experiments which I have made myself.
I shall conclude this preface by transcribing, literally, some
observations of the Abbé de Condillac, which I think describe, with a
good deal of truth, the state of chemistry at a period not far distant
from our own. These observations were made on a different subject; but
they will not, on this account, have less force, if the application of
them be thought just.
'Instead of applying observation to the things we wished to know, we
have chosen rather to imagine them. Advancing from one ill founded
supposition to another, we have at last bewildered ourselves amidst a
multitude of errors. These errors becoming prejudices, are, of course,
adopted as principles, and we thus bewilder ourselves more and more. The
method, too, by which we conduct our reasonings is as absurd; we abuse
words which we do not understand, and call this the art of reasoning.
When matters have been brought this length, when errors have been thus
accumulated, there is but one remedy by which order can be restored to
the faculty of thinking; this is, to forget all that we have learned, to
trace back our ideas to their source, to follow the train in which they
rise, and, as my Lord Bacon says, to frame the human understanding anew.
'This remedy becomes the more difficult in proportion as we think
ourselves more learned. Might it not be thought that works which
treated of the sciences with the utmost perspicuity, with great
precision and order, must be understood by every body? The fact is,
those who have never studied any thing will understand them better than
those who have studied a great deal, and especially than those who have
written a great deal.'
At the end of the fifth chapter, the Abbé de Condillac adds: 'But, after
all, the sciences have made progress, because philosophers have applied
themselves with more attention to observe, and have communicated to
their language that precision and accuracy which they have employed in
their observations: In correcting their language they reason better.'
CONTENTS.
PART FIRST.
Of the Formation and Decomposition of
Aëriform Fluids,--of the Combustion
of Simple Bodies, and the Formation
of Acids, Page 1
CHAP. I.--Of the Combinations of Caloric, and
the Formation of Elastic Aëriform Fluids or
Gasses, ibid.
CHAP. II.--General Views relative to the Formation
and Composition of our Atmosphere, 26
CHAP. III.--Analysis of Atmospheric Air, and its
Division into two Elastic Fluids; one fit for
Respiration, the other incapable of being respired, 32
CHAP. IV.--Nomenclature of the several constituent
Parts of Atmospheric Air, 48
CHAP. V.--Of the Decomposition of Oxygen
Gas by Sulphur, Phosphorus, and Charcoal, and
of the Formation of Acids in general, 54
CHAP. VI.--Of the Nomenclature of Acids in general,
and particularly of those drawn from
Nitre and Sea Salt, 66
CHAP. VII.--Of the Decomposition of Oxygen
Gas by means of Metals, and the Formation of
Metallic Oxyds, 78
CHAP. VIII.--Of the Radical Principle of Water,
and of its Decomposition by Charcoal and
Iron, 83
CHAP. IX.--Of the Quantities of Caloric disengaged
from different Species of Combustion, 97
Combustion of Phosphorus, 100
SECT. I.--Combustion of Charcoal, 101
SECT. II.--Combustion of Hydrogen Gas, 102
SECT. III.--Formation of Nitric Acid, 102
SECT. IV.--Combustion of Wax, 105
SECT. V.--Combustion of Olive Oil, 106
CHAP. X.--Of the Combustion of Combustible
Substances with each other, 109
CHAP. XI.--Observations upon Oxyds and Acids
with several Bases, and upon the Composition
of Animal and Vegetable Substances, 115
CHAP. XII.--Of the Decomposition of Vegetable
and Animal Substances by the Action of Fire, 123
CHAP. XIII.--Of the Decomposition of Vegetable
Oxyds by the Vinous Fermentation, 129
CHAP. XIV.--Of the Putrefactive Fermentation, 141
CHAP. XV.--Of the Acetous Fermentation, 146
CHAP. XVI.--Of the Formation of Neutral Salts,
and of their Bases, 149
SECT. I.--Of Potash, 151
SECT. II.--Of Soda, 155
SECT. III.--Of Ammoniac, 156
SECT. IV.--Of Lime, Magnesia, Barytes, and Argill, 157
SECT. V.--Of Metallic Bodies, 159
CHAP. XVII.--Continuation of the Observations
upon Salifiable Bases, and the Formation
of Neutral Salts, 161
PART II.
Of the Combinations of Acids with Salifiable
Bases, and of the Formation
of Neutral Salts, 175
INTRODUCTION, ibid.
TABLE of Simple Substances, 175
SECT. I.--Observations upon simple Substances, 176
TABLE of Compound Oxydable and Acidifiable
Bases, 179
SECT. II.--Observations upon Compound Radicals, 180
SECT. III.--Observations upon the Combinations
of Light and Caloric with different Substances, 182
TABLE of the Combinations of Oxygen with the
Simple Substances, to face 185
SECT. IV.--Observations upon these Combinations, 185
TABLE of the Combinations of Oxygen with Compound
Radicals, 190
SECT. V.--Observations upon these Combinations, 191
TABLE of the Combinations of Azote with the
Simple Substances, 194
SECT VI.--Observations upon these Combinations
of Azote, 195
TABLE of the Combinations of Hydrogen with
Simple Substances, 198
SECT. VII.--Observations upon Hydrogen, and its
Combinations, 199
TABLE of the Binary Combinations of Sulphur
with the Simple Substances, 202
SECT. VIII.--Observations upon Sulphur, and its
Combinations, 203
TABLE of the Combinations of Phosphorus with
Simple Substances, 204
SECT. IX.--Observations upon Phosphorus and its
Combinations, 205
TABLE of the Binary Combinations of Charcoal, 207
SECT. X.--Observations upon Charcoal, and its
Combinations, 208
SECT. XI.--Observations upon the Muriatic, Fluoric,
and Boracic Radicals, and their Combinations, 209
SECT. XII.--Observations upon the Combinations
of Metals with each other, 219
TABLE of the Combinations of Azote, in the State
of Nitrous Acid, with the Salifiable Bases, 212
TABLE of the Combinations of Azote, in the State
of Nitric Acid, with the Salifiable Bases, 213
SECT. XIII.--Observations upon Nitrous and Nitric
Acids, and their Combinations with Salifiable
Bases, 214
TABLE of the Combinations of Sulphuric Acid
with the Salifiable Bases, 218
SECT. XIV.--Observations upon Sulphuric Acid,
and its Combinations, 219
TABLE of the Combinations of Sulphurous Acid, 222
SECT. XV.--Observations upon Sulphurous Acid,
and its Combinations with Salifiable Bases, 223
TABLE of the Combinations of Phosphorous and
Phosphoric Acids, 225
SECT. XVI.--Observations upon Phosphorous and
Phosphoric Acids, and their Combinations
with Salifiable Bases, 226
TABLE of the Combinations of Carbonic Acid, 228
SECT. XVII.--Observations upon Carbonic Acid,
and its Combinations with Salifiable Bases, 229
TABLE of the Combinations of Muriatic Acid, 231
TABLE of the Combinations of Oxygenated Muriatic
Acid, 232
SECT. XVIII.--Observations upon Muriatic and
Oxygenated Muriatic Acid, and their Combinations
with Salifiable Bases, 233
TABLE of the Combinations of Nitro-Muriatic Acid, 236
SECT. XIX.--Observations upon Nitro-muriatic
Acid, and its Combinations with Salifiable
Bases, 237
TABLE of the Combinations of Fluoric Acid, 239
SECT. XX.--Observations upon Fluoric Acid, and
its Combinations with Salifiable Bases, 240
TABLE of the Combinations of Boracic Acid, 242
SECT. XXI.--Observations upon Boracic Acid,
and its Combinations with Salifiable Bases, 243
TABLE of the Combinations of Arseniac Acid, 246
SECT. XXII.--Observations upon Arseniac Acid,
and its Combinations with Salifiable Bases, 247
SECT. XXIII.--Observations upon Molibdic Acid,
and its Combinations with Salifiable Bases, 249
SECT. XXIV.--Observations upon Tungstic Acid,
and its Combinations with Salifiable Bases, and
a Table of these in the order of their Affinity, 251
TABLE of the Combinations of Tartarous Acid, 253
SECT. XXV.--Observations upon Tartarous Acid,
and its Combinations with Salifiable Bases, 254
SECT. XXVI.--Observations upon Mallic Acid,
and its Combinations with Salifiable Bases, 256
TABLE of the Combinations of Citric Acid, 258
SECT. XXVII.--Observations upon Citric Acid,
and its Combinations with Salifiable Bases, 259
TABLE of the Combinations of Pyro-lignous Acid, 260
SECT. XXVIII.--Observations upon Pyro-lignous
Acid, and its Combinations with Salifiable Bases, 261
SECT. XXIX.--Observations upon Pyro-tartarous
Acid, and its Combinations with Salifiable
Bases, ibid.
TABLE of the Combinations of Pyro-mucous Acid, 263
SECT. XXX.--Observations upon Pyro-mucous
Acid, and its Combinations with Salifiable Bases, 264
TABLE of the Combinations of Oxalic Acid, 265
SECT. XXXI.--Observations upon Oxalic Acid,
and its Combinations with Salifiable Bases, 266
TABLE of the Combinations of Acetous Acid, to
face 267
SECT. XXXII.--Observations upon Acetous Acid,
and its Combinations with the Salifiable Bases, 267
TABLE of the Combinations of Acetic Acid, 271
SECT. XXXIII.--Observations upon Acetic Acid,
and its Combinations with Salifiable Bases, 272
TABLE of the Combinations of Succinic Acid, 273
SECT. XXXIV.--Observations upon Succinic Acid,
and its Combinations with Salifiable Bases, 274
SECT. XXXV.--Observations upon Benzoic Acid,
and its Combinations with Salifiable Bases, 275
SECT. XXXVI.--Observations upon Camphoric
Acid, and its Combinations with Salifiable
Bases, 276
SECT. XXXVII.--Observations upon Gallic Acid,
and its Combinations with Salifiable Bases, 277
SECT. XXXVIII.--Observations upon Lactic Acid,
and its Combinations with Salifiable Bases, 278
TABLE of the Combinations of Saccholactic Acid, 280
SECT. XXXIX.--Observations upon Saccholactic
Acid, and its Combination with Salifiable Bases, 281
TABLE of the Combinations of Formic Acid, 282
SECT. XL.--Observations upon Formic Acid, and
its Combinations with the Salifiable Bases, 283
SECT. XLI.--Observations upon the Bombic Acid,
and its Combinations with the Salifiable Bases, 284
TABLE of the Combinations of the Sebacic Acid, 285
SECT. XLII.--Observations upon the Sebacic Acid,
and its Combinations with the Salifiable Bases, 286
SECT. XLIII.--Observations upon the Lithic Acid,
and its Combinations with the Salifiable Bases, 287
TABLE of the Combinations of the Prussic Acid, 288
SECT. XLIV.--Observations upon the Prussic Acid,
and its Combinations with the Salifiable Bases, 289
PART III.
Description of the Instruments and Operations
of Chemistry, 291
INTRODUCTION, 291
CHAP. I.--Of the Instruments necessary for determining
the Absolute and Specific Gravities of
Solid and Liquid Bodies, 295
CHAP. II.--Of Gazometry, or the Measurement
of the Weight and Volume of Aëriform Substances, 304
SECT. I.--Of the Pneumato-chemical Apparatus, ibid.
SECT. II.--Of the Gazometer, 308
SECT. III.--Some other methods for Measuring
the Volume of Gasses, 319
SECT. IV.--Of the method of Separating the different
Gasses from each other, 323
SECT. V.--Of the necessary Corrections of the Volume
of Gasses, according to the Pressure of
the Atmosphere, 328
SECT. VI.--Of the Correction relative to the Degrees
of the Thermometer, 335
SECT. VII.--Example for Calculating the Corrections
relative to the Variations of Pressure and
Temperature, 337
SECT. VIII.--Method of determining the Weight
of the different Gasses, 340
CHAP. III.--Description of the Calorimeter, or
Apparatus for measuring Caloric, 343
CHAP. IV.--Of the Mechanical Operations for
Division of Bodies, 357
SECT. I.--Of Trituration, Levigation, and Pulverization, ibid.
SECT. II.--Of Sifting and Washing Powdered
Substances, 361
SECT. III.--Of Filtration, 363
SECT. IV.--Of Decantation, 365
CHAP. V.--Of Chemical means for Separating the
Particles of Bodies from each other without
Decomposition, and for Uniting them again, 367
SECT. I.--Of the Solution of Salts, 368
SECT. II.--Of Lixiviation, 373
SECT. III.--Of Evaporation, 375
SECT. IV.--Of Cristallization, 379
SECT. V.--Of Simple Distillation, 384
SECT. VI.--Of Sublimation, 388
CHAP. VI.--Of Pneumato-chemical Distillations,
Metallic Dissolutions, and some other operations
which require very complicated instruments, 390
SECT. I.--Of Compound and Pneumato-chemical
Distillations, ibid.
SECT. II.--Of Metallic Dissolutions, 398
SECT. III.--Apparatus necessary in Experiments
upon Vinous and Putrefactive Fermentations, 401
SECT. IV.--Apparatus for the Decomposition of
Water, 404
CHAP. VII.--Of the Composition and Use of
Lutes, 407
CHAP. VIII.--Of Operations upon Combustion
and Deflagration, 414
SECT. I.--Of Combustion in general, ibid.
SECT. II.--Of the Combustion of Phosphorus, 418
SECT. III.--Of the Combustion of Charcoal, 422
SECT. IV.--Of the Combustion of Oils, 426
SECT. V.--Of the Combustion of Alkohol, 433
SECT. VI.--Of the Combustion of Ether, 435
SECT. VII.--Of the Combustion of Hydrogen
Gas, and the Formation of Water, 437
SECT. VIII.--Of the Oxydation of Metals, 441
CHAP. IX.--Of Deflagration, 452
CHAP. X.--Of the Instruments necessary for Operating
upon Bodies in very high Temperatures, 460
SECT. I.--Of Fusion, ibid.
SECT. II.--Of Furnaces, 462
SECT. III.--Of increasing the Action of Fire, by
using Oxygen Gas instead of Atmospheric Air, 474
APPENDIX.
No. I.--TABLE for Converting Lines, or Twelfth
Parts of an Inch, and Fractions of Lines, into
Decimal Fractions of the Inch, 481
No. II.--TABLE for Converting the Observed
Heighth of Water in the Jars of the Pneumato-Chemical
Apparatus, expressed in Inches and
Decimals, into Corresponding Heighths of Mercury, 482
No. III.--TABLE for Converting the Ounce
Measures used by Dr Priestley into French and
English Cubical Inches, 483
No. IV.--TABLE for Reducing the Degrees of
Reaumeur's Thermometer into its corresponding
Degrees of Fahrenheit's Scale, 484
No. V.--ADDITIONAL.--RULES for Converting
French Weights and Measures into correspondent
English Denominations, 485
No. VI.--TABLE of the Weights of the different
Gasses, at 28 French inches, or 29.84 English
inches barometrical pressure, and at 10° (54.5°)
of temperature, expressed in English measure
and English Troy weight, 490
No. VII.--TABLES of the Specific Gravities of
different bodies, 491
No. VIII.--ADDITIONAL.--RULES for Calculating
the Absolute Gravity in English Troy
Weight of a Cubic Foot and Inch, English
Measure, of any Substance whose Specific Gravity
is known, 505
No. IX.--TABLES for Converting Ounces, Drams,
and Grains, Troy, into Decimals of the Troy
Pound of 12 Ounces, and for Converting Decimals
of the Pound Troy into Ounces, &c. 508
No. X.--TABLE of the English Cubical Inches and
Decimals corresponding to a determinate Troy
Weight of Distilled Water at the Temperature
of 55°, calculated from Everard's experiment, 511
ELEMENTS
OF
CHEMISTRY.
PART I.
Of the Formation and Decomposition of Aëriform Fluids--of the
Combustion of Simple Bodies--and the Formation of Acids.
CHAP. I.
_Of the Combinations of Caloric, and the Formation of Elastic Aëriform
Fluids._
That every body, whether solid or fluid, is augmented in all its
dimensions by any increase of its sensible heat, was long ago fully
established as a physical axiom, or universal proposition, by the
celebrated Boerhaave. Such facts as have been adduced for controverting
the generality of this principle offer only fallacious results, or, at
least, such as are so complicated with foreign circumstances as to
mislead the judgment: But, when we separately consider the effects, so
as to deduce each from the cause to which they separately belong, it is
easy to perceive that the separation of particles by heat is a constant
and general law of nature.
When we have heated a solid body to a certain degree, and have thereby
caused its particles to separate from each other, if we allow the body
to cool, its particles again approach each other in the same proportion
in which they were separated by the increased temperature; the body
returns through the same degrees of expansion which it before extended
through; and, if it be brought back to the same temperature from which
we set out at the commencement of the experiment, it recovers exactly
the same dimensions which it formerly occupied. But, as we are still
very far from being able to arrive at the degree of absolute cold, or
deprivation of all heat, being unacquainted with any degree of coldness
which we cannot suppose capable of still farther augmentation, it
follows, that we are still incapable of causing the ultimate particles
of bodies to approach each other as near as is possible; and,
consequently, that the particles of all bodies do not touch each other
in any state hitherto known, which, tho' a very singular conclusion, is
yet impossible to be denied.
It is supposed, that, since the particles of bodies are thus continually
impelled by heat to separate from each other, they would have no
connection between themselves; and, of consequence, that there could be
no solidity in nature, unless they were held together by some other
power which tends to unite them, and, so to speak, to chain them
together; which power, whatever be its cause, or manner of operation, we
name Attraction.
Thus the particles of all bodies may be considered as subjected to the
action of two opposite powers, the one repulsive, the other attractive,
between which they remain in equilibrio. So long as the attractive force
remains stronger, the body must continue in a state of solidity; but if,
on the contrary, heat has so far removed these particles from each
other, as to place them beyond the sphere of attraction, they lose the
adhesion they before had with each other, and the body ceases to be
solid.
Water gives us a regular and constant example of these facts; whilst
below Zero[2] of the French thermometer, or 32° of Fahrenheit, it
remains solid, and is called ice. Above that degree of temperature, its
particles being no longer held together by reciprocal attraction, it
becomes liquid; and, when we raise its temperature above 80°, (212°) its
particles, giving way to the repulsion caused by the heat, assume the
state of vapour or gas, and the water is changed into an aëriform fluid.
The same may be affirmed of all bodies in nature: They are either solid
or liquid, or in the state of elastic aëriform vapour, according to the
proportion which takes place between the attractive force inherent in
their particles, and the repulsive power of the heat acting upon these;
or, what amounts to the same thing, in proportion to the degree of heat
to which they are exposed.
It is difficult to comprehend these phenomena, without admitting them as
the effects of a real and material substance, or very subtile fluid,
which, insinuating itself between the particles of bodies, separates
them from each other; and, even allowing the existence of this fluid to
be hypothetical, we shall see in the sequel, that it explains the
phenomena of nature in a very satisfactory manner.
This substance, whatever it is, being the cause of heat, or, in other
words, the sensation which we call _warmth_ being caused by the
accumulation of this substance, we cannot, in strict language,
distinguish it by the term _heat_; because the same name would then very
improperly express both cause and effect. For this reason, in the memoir
which I published in 1777[3], I gave it the names of _igneous fluid_ and
_matter of heat_. And, since that time, in the work[4] published by Mr
de Morveau, Mr Berthollet, Mr de Fourcroy, and myself, upon the
reformation of chemical nomenclature, we thought it necessary to banish
all periphrastic expressions, which both lengthen physical language, and
render it more tedious and less distinct, and which even frequently does
not convey sufficiently just ideas of the subject intended. Wherefore,
we have distinguished the cause of heat, or that exquisitely elastic
fluid which produces it, by the term of _caloric_. Besides, that this
expression fulfils our object in the system which we have adopted, it
possesses this farther advantage, that it accords with every species of
opinion, since, strictly speaking, we are not obliged to suppose this to
be a real substance; it being sufficient, as will more clearly appear in
the sequel of this work, that it be considered as the repulsive cause,
whatever that may be, which separates the particles of matter from each
other; so that we are still at liberty to investigate its effects in an
abstract and mathematical manner.
In the present state of our knowledge, we are unable to determine
whether light be a modification of caloric, or if caloric be, on the
contrary, a modification of light. This, however, is indisputable, that,
in a system where only decided facts are admissible, and where we avoid,
as far as possible, to suppose any thing to be that is not really known
to exist, we ought provisionally to distinguish, by distinct terms, such
things as are known to produce different effects. We therefore
distinguish light from caloric; though we do not therefore deny that
these have certain qualities in common, and that, in certain
circumstances, they combine with other bodies almost in the same manner,
and produce, in part, the same effects.
What I have already said may suffice to determine the idea affixed to
the word _caloric_; but there remains a more difficult attempt, which
is, to give a just conception of the manner in which caloric acts upon
other bodies. Since this subtile matter penetrates through the pores of
all known substances; since there are no vessels through which it cannot
escape, and, consequently, as there are none which are capable of
retaining it, we can only come at the knowledge of its properties by
effects which are fleeting, and difficultly ascertainable. It is in
these things which we neither see nor feel, that it is especially
necessary to guard against the extravagancy of our imagination, which
forever inclines to step beyond the bounds of truth, and is very
difficultly restrained within the narrow line of facts.
We have already seen, that the same body becomes solid, or fluid, or
aëriform, according to the quantity of caloric by which it is
penetrated; or, to speak more strictly, according as the repulsive force
exerted by the caloric is equal to, stronger, or weaker, than the
attraction of the particles of the body it acts upon.
But, if these two powers only existed, bodies would become liquid at an
indivisible degree of the thermometer, and would almost instantaneously
pass from the solid state of aggregation to that of aëriform elasticity.
Thus water, for instance, at the very moment when it ceases to be ice,
would begin to boil, and would be transformed into an aëriform fluid,
having its particles scattered indefinitely through the surrounding
space. That this does not happen, must depend upon the action of some
third power. The pressure of the atmosphere prevents this separation,
and causes the water to remain in the liquid state till it be raised to
80° of temperature (212°) above zero of the French thermometer, the
quantity of caloric which it receives in the lowest temperature being
insufficient to overcome the pressure of the atmosphere.
Whence it appears that, without this atmospheric pressure, we should not
have any permanent liquid, and should only be able to see bodies in that
state of existence in the very instant of melting, as the smallest
additional caloric would instantly separate their particles, and
dissipate them through the surrounding medium. Besides, without this
atmospheric pressure, we should not even have any aëriform fluids,
strictly speaking, because the moment the force of attraction is
overcome by the repulsive power of the caloric, the particles would
separate themselves indefinitely, having nothing to give limits to their
expansion, unless their own gravity might collect them together, so as
to form an atmosphere.
Simple reflection upon the most common experiments is sufficient to
evince the truth of these positions. They are more particularly proved
by the following experiment, which I published in the Memoirs of the
French Academy for 1777, p. 426.
Having filled with sulphuric ether[5] a small narrow glass vessel, A,
(Plate VII. Fig. 17.), standing upon its stalk P, the vessel, which is
from twelve to fifteen lines diameter, is to be covered by a wet
bladder, tied round its neck with several turns of strong thread; for
greater security, fix a second bladder over the first. The vessel should
be filled in such a manner with the ether, as not to leave the smallest
portion of air between the liquor and the bladder. It is now to be
placed under the recipient BCD of an air-pump, of which the upper part B
ought to be fitted with a leathern lid, through which passes a wire EF,
having its point F very sharp; and in the same receiver there ought to
be placed the barometer GH. The whole being thus disposed, let the
recipient be exhausted, and then, by pushing down the wire EF, we make a
hole in the bladder. Immediately the ether begins to boil with great
violence, and is changed into an elastic aëriform fluid, which fills the
receiver. If the quantity of ether be sufficient to leave a few drops in
the phial after the evaporation is finished, the elastic fluid produced
will sustain the mercury in the barometer attached to the air-pump, at
eight or ten inches in winter, and from twenty to twenty-five in
summer[6]. To render this experiment more complete, we may introduce a
small thermometer into the phial A, containing the ether, which will
descend considerably during the evaporation.
The only effect produced in this experiment is, the taking away the
weight of the atmosphere, which, in its ordinary state, presses on the
surface of the ether; and the effects resulting from this removal
evidently prove, that, in the ordinary temperature of the earth, ether
would always exist in an aëriform state, but for the pressure of the
atmosphere, and that the passing of the ether from the liquid to the
aëriform state is accompanied by a considerable lessening of heat;
because, during the evaporation, a part of the caloric, which was before
in a free state, or at least in equilibrio in the surrounding bodies,
combines with the ether, and causes it to assume the aëriform state.
The same experiment succeeds with all evaporable fluids, such as
alkohol, water, and even mercury; with this difference, that the
atmosphere formed in the receiver by alkohol only supports the attached
barometer about one inch in winter, and about four or five inches in
summer; that formed by water, in the same situation, raises the mercury
only a few lines, and that by quicksilver but a few fractions of a line.
There is therefore less fluid evaporated from alkohol than from ether,
less from water than from alkohol, and still less from mercury than from
either; consequently there is less caloric employed, and less cold
produced, which quadrates exactly with the results of these experiments.
Another species of experiment proves very evidently that the aëriform
state is a modification of bodies dependent on the degree of
temperature, and on the pressure which these bodies undergo. In a Memoir
read by Mr de la Place and me to the Academy in 1777, which has not been
printed, we have shown, that, when ether is subjected to a pressure
equal to twenty-eight inches of the barometer, or about the medium
pressure of the atmosphere, it boils at the temperature of about 32°
(104°), or 33° (106.25°), of the thermometer. Mr de Luc, who has made
similar experiments with spirit of wine, finds it boils at 67°
(182.75°). And all the world knows that water boils at 80° (212°). Now,
boiling being only the evaporation of a liquid, or the moment of its
passing from the fluid to the aëriform state, it is evident that, if we
keep ether continually at the temperature of 33° (106.25°), and under
the common pressure of the atmosphere, we shall have it always in an
elastic aëriform state; and that the same thing will happen with alkohol
when above 67° (182.75°), and with water when above 80° (212°); all
which are perfectly conformable to the following experiment[7].
I filled a large vessel ABCD (Plate VII. Fig. 16.) with water, at 35°
(110.75°), or 36° (113°); I suppose the vessel transparent, that we may
see what takes place in the experiment; and we can easily hold the hands
in water at that temperature without inconvenience. Into it I plunged
some narrow necked bottles F, G, which were filled with the water, after
which they were turned up, so as to rest on their mouths on the bottom
of the vessel. Having next put some ether into a very small matrass,
with its neck a b c, twice bent as in the Plate, I plunged this
matrass into the water, so as to have its neck inserted into the mouth
of one of the bottles F. Immediately upon feeling the effects of the
heat communicated to it by the water in the vessel ABCD it began to
boil; and the caloric entering into combination with it, changed it into
elastic aëriform fluid, with which I filled several bottles
successively, F, G, &c.
This is not the place to enter upon the examination of the nature and
properties of this aëriform fluid, which is extremely inflammable; but,
confining myself to the object at present in view, without anticipating
circumstances, which I am not to suppose the reader to know, I shall
only observe, that the ether, from this experiment, is almost only
capable of existing in the aëriform state in our world; for, if the
weight of our atmosphere was only equal to between 20 and 24 inches of
the barometer, instead of 28 inches, we should never be able to obtain
ether in the liquid state, at least in summer; and the formation of
ether would consequently be impossible upon mountains of a moderate
degree of elevation, as it would be converted into gas immediately upon
being produced, unless we employed recipients of extraordinary strength,
together with refrigeration and compression. And, lastly, the
temperature of the blood being nearly that at which ether passes from
the liquid to the aëriform state, it must evaporate in the primae viae,
and consequently it is very probable the medical properties of this
fluid depend chiefly upon its mechanical effect.
These experiments succeed better with nitrous ether, because it
evaporates in a lower temperature than sulphuric ether. It is more
difficult to obtain alkohol in the aëriform state; because, as it
requires 67° (182.75°) to reduce it to vapour, the water of the bath
must be almost boiling, and consequently it is impossible to plunge the
hands into it at that temperature.
It is evident that, if water were used in the foregoing experiment, it
would be changed into gas, when exposed to a temperature superior to
that at which it boils. Although thoroughly convinced of this, Mr de la
Place and myself judged it necessary to confirm it by the following
direct experiment. We filled a glass jar A, (Plate VII. Fig. 5.) with
mercury, and placed it with its mouth downwards in a dish B, likewise
filled with mercury, and having introduced about two gross of water into
the jar, which rose to the top of the mercury at CD; we then plunged the
whole apparatus into an iron boiler EFGH, full of boiling sea-water of
the temperature of 85° (123.25°), placed upon the furnace GHIK.
Immediately upon the water over the mercury attaining the temperature of
80° (212°), it began to boil; and, instead of only filling the small
space ACD, it was converted into an aëriform fluid, which filled the
whole jar; the mercury even descended below the surface of that in the
dish B; and the jar must have been overturned, if it had not been very
thick and heavy, and fixed to the dish by means of iron-wire.
Immediately after withdrawing the apparatus from the boiler, the vapour
in the jar began to condense, and the mercury rose to its former
station; but it returned again to the aëriform state a few seconds after
replacing the apparatus in the boiler.
We have thus a certain number of substances, which are convertible into
elastic aëriform fluids by degrees of temperature, not much superior to
that of our atmosphere. We shall afterwards find that there are several
others which undergo the same change in similar circumstances, such as
muriatic or marine acid, ammoniac or volatile alkali, the carbonic acid
or fixed air, the sulphurous acid, &c. All of these are permanently
elastic in or about the mean temperature of the atmosphere, and under
its common pressure.
All these facts, which could be easily multiplied if necessary, give me
full right to assume, as a general principle, that almost every body in
nature is susceptible of three several states of existence, solid,
liquid, and aëriform, and that these three states of existence depend
upon the quantity of caloric combined with the body. Henceforwards I
shall express these elastic aëriform fluids by the generic term _gas_;
and in each species of gas I shall distinguish between the caloric,
which in some measure serves the purpose of a solvent, and the
substance, which in combination with the caloric, forms the base of the
gas.
To these bases of the different gases, which are hitherto but little
known, we have been obliged to assign names; these I shall point out in
Chap. IV. of this work, when I have previously given an account of the
phenomena attendant upon the heating and cooling of bodies, and when I
have established precise ideas concerning the composition of our
atmosphere.
We have already shown, that the particles of every substance in nature
exist in a certain state of equilibrium, between that attraction which
tends to unite and keep the particles together, and the effects of the
caloric which tends to separate them. Hence the caloric not only
surrounds the particles of all bodies on every side, but fills up every
interval which the particles of bodies leave between each other. We may
form an idea of this, by supposing a vessel filled with small spherical
leaden bullets, into which a quantity of fine sand is poured, which,
insinuating into the intervals between the bullets, will fill up every
void. The balls, in this comparison, are to the sand which surrounds
them exactly in the same situation as the particles of bodies are with
respect to the caloric; with this difference only, that the balls are
supposed to touch each other, whereas the particles of bodies are not in
contact, being retained at a small distance from each other, by the
caloric.
If, instead of spherical balls, we substitute solid bodies of a
hexahedral, octohedral, or any other regular figure, the capacity of the
intervals between them will be lessened, and consequently will no longer
contain the same quantity of sand. The same thing takes place, with
respect to natural bodies; the intervals left between their particles
are not of equal capacity, but vary in consequence of the different
figures and magnitude of their particles, and of the distance at which
these particles are maintained, according to the existing proportion
between their inherent attraction, and the repulsive force exerted upon
them by the caloric.
In this manner we must understand the following expression, introduced
by the English philosophers, who have given us the first precise ideas
upon this subject; _the capacity of bodies for containing the matter of
heat_. As comparisons with sensible objects are of great use in
assisting us to form distinct notions of abstract ideas, we shall
endeavour to illustrate this, by instancing the phenomena which take
place between water and bodies which are wetted and penetrated by it,
with a few reflections.
If we immerge equal pieces of different kinds of wood, suppose cubes of
one foot each, into water, the fluid gradually insinuates itself into
their pores, and the pieces of wood are augmented both in weight and
magnitude: But each species of wood will imbibe a different quantity of
water; the lighter and more porous woods will admit a larger, the
compact and closer grained will admit of a lesser quantity; for the
proportional quantities of water imbibed by the pieces will depend upon
the nature of the constituent particles of the wood, and upon the
greater or lesser affinity subsisting between them and water. Very
resinous wood, for instance, though it may be at the same time very
porous, will admit but little water. We may therefore say, that the
different kinds of wood possess different capacities for receiving
water; we may even determine, by means of the augmentation of their
weights, what quantity of water they have actually absorbed; but, as we
are ignorant how much water they contained, previous to immersion, we
cannot determine the absolute quantity they contain, after being taken
out of the water.
The same circumstances undoubtedly take place, with bodies that are
immersed in caloric; taking into consideration, however, that water is
an incompressible fluid, whereas caloric is, on the contrary, endowed
with very great elasticity; or, in other words, the particles of caloric
have a great tendency to separate from each other, when forced by any
other power to approach; this difference must of necessity occasion
very considerable diversities in the results of experiments made upon
these two substances.
Having established these clear and simple propositions, it will be very
easy to explain the ideas which ought to be affixed to the following
expressions, which are by no means synonimous, but possess each a strict
and determinate meaning, as in the following definitions:
_Free caloric_, is that which is not combined in any manner with any
other body. But, as we live in a system to which caloric has a very
strong adhesion, it follows that we are never able to obtain it in the
state of absolute freedom.
_Combined caloric_, is that which is fixed in bodies by affinity or
elective attraction, so as to form part of the substance of the body,
even part of its solidity.
By the expression _specific caloric_ of bodies, we understand the
respective quantities of caloric requisite for raising a number of
bodies of the same weight to an equal degree of temperature. This
proportional quantity of caloric depends upon the distance between the
constituent particles of bodies, and their greater or lesser degrees of
cohesion; and this distance, or rather the space or void resulting from
it, is, as I have already observed, called the _capacity of bodies for
containing caloric_.
_Heat_, considered as a sensation, or, in other words, sensible heat, is
only the effect produced upon our sentient organs, by the motion or
passage of caloric, disengaged from the surrounding bodies. In general,
we receive impressions only in consequence of motion, and we might
establish it as an axiom, _That_, WITHOUT MOTION, THERE IS NO SENSATION.
This general principle applies very accurately to the sensations of heat
and cold: When we touch a cold body, the caloric which always tends to
become in equilibrio in all bodies, passes from our hand into the body
we touch, which gives us the feeling or sensation of cold. The direct
contrary happens, when we touch a warm body, the caloric then passing
from the body into our hand, produces the sensation of heat. If the hand
and the body touched be of the same temperature, or very nearly so, we
receive no impression, either of heat or cold, because there is no
motion or passage of caloric; and thus no sensation can take place,
without some correspondent motion to occasion it.
When the thermometer rises, it shows, that free caloric is entering into
the surrounding bodies: The thermometer, which is one of these, receives
its share in proportion to its mass, and to the capacity which it
possesses for containing caloric. The change therefore which takes place
upon the thermometer, only announces a change of place of the caloric
in those bodies, of which the thermometer forms one part; it only
indicates the portion of caloric received, without being a measure of
the whole quantity disengaged, displaced, or absorbed.
The most simple and most exact method for determining this latter point,
is that described by Mr de la Place, in the Memoirs of the Academy, No.
1780, p. 364; a summary explanation of which will be found towards the
conclusion of this work. This method consists in placing a body, or a
combination of bodies, from which caloric is disengaging, in the midst
of a hollow sphere of ice; and the quantity of ice melted becomes an
exact measure of the quantity of caloric disengaged. It is possible, by
means of the apparatus which we have caused to be constructed upon this
plan, to determine, not as has been pretended, the capacity of bodies
for containing heat, but the ratio of the increase or diminution of
capacity produced by determinate degrees of temperature. It is easy with
the same apparatus, by means of divers combinations of experiments, to
determine the quantity of caloric requisite for converting solid
substances into liquids, and liquids into elastic aëriform fluids; and,
_vice versa_, what quantity of caloric escapes from elastic vapours in
changing to liquids, and what quantity escapes from liquids during their
conversion into solids. Perhaps, when experiments have been made with
sufficient accuracy, we may one day be able to determine the
proportional quantity of caloric, necessary for producing the several
species of gasses. I shall hereafter, in a separate chapter, give an
account of the principal results of such experiments as have been made
upon this head.
It remains, before finishing this article, to say a few words relative
to the cause of the elasticity of gasses, and of fluids in the state of
vapour. It is by no means difficult to perceive that this elasticity
depends upon that of caloric, which seems to be the most eminently
elastic body in nature. Nothing is more readily conceived, than that one
body should become elastic by entering into combination with another
body possessed of that quality. We must allow that this is only an
explanation of elasticity, by an assumption of elasticity, and that we
thus only remove the difficulty one step farther, and that the nature of
elasticity, and the reason for caloric being elastic, remains still
unexplained. Elasticity in the abstract is nothing more than that
quality of the particles of bodies by which they recede from each other
when forced together. This tendency in the particles of caloric to
separate, takes place even at considerable distances. We shall be
satisfied of this, when we consider that air is susceptible of
undergoing great compression, which supposes that its particles were
previously very distant from each other; for the power of approaching
together certainly supposes a previous distance, at least equal to the
degree of approach. Consequently, those particles of the air, which are
already considerably distant from each other, tend to separate still
farther. In fact, if we produce Boyle's vacuum in a large receiver, the
very last portion of air which remains spreads itself uniformly through
the whole capacity of the vessel, however large, fills it completely
throughout, and presses every where against its sides: We cannot,
however, explain this effect, without supposing that the particles make
an effort to separate themselves on every side, and we are quite
ignorant at what distance, or what degree of rarefaction, this effort
ceases to act.
Here, therefore, exists a true repulsion between the particles of
elastic fluids; at least, circumstances take place exactly as if such a
repulsion actually existed; and we have very good right to conclude,
that the particles of caloric mutually repel each other. When we are
once permitted to suppose this repelling force, the _rationale_ of the
formation of gasses, or aëriform fluids, becomes perfectly simple; tho'
we must, at the same time, allow, that it is extremely difficult to form
an accurate conception of this repulsive force acting upon very minute
particles placed at great distances from each other.
It is, perhaps, more natural to suppose, that the particles of caloric
have a stronger mutual attraction than those of any other substance, and
that these latter particles are forced asunder in consequence of this
superior attraction between the particles of the caloric, which forces
them between the particles of other bodies, that they may be able to
reunite with each other. We have somewhat analogous to this idea in the
phenomena which occur when a dry sponge is dipt into water: The sponge
swells; its particles separate from each other; and all its intervals
are filled up by the water. It is evident, that the sponge, in the act
of swelling, has acquired a greater capacity for containing water than
it had when dry. But we cannot certainly maintain, that the introduction
of water between the particles of the sponge has endowed them with a
repulsive power, which tends to separate them from each other; on the
contrary, the whole phenomena are produced by means of attractive
powers; and these are, _first_, The gravity of the water, and the power
which it exerts on every side, in common with all other fluids; _2dly_,
The force of attraction which takes place between the particles of the
water, causing them to unite together; _3dly_, The mutual attraction of
the particles of the sponge with each other; and, _lastly_, The
reciprocal attraction which exists between the particles of the sponge
and those of the water. It is easy to understand, that the explanation
of this fact depends upon properly appreciating the intensity of, and
connection between, these several powers. It is probable, that the
separation of the particles of bodies, occasioned by caloric, depends in
a similar manner upon a certain combination of different attractive
powers, which, in conformity with the imperfection of our knowledge, we
endeavour to express by saying, that caloric communicates a power of
repulsion to the particles of bodies.
FOOTNOTES:
[2] Whenever the degree of heat occurs in this work, it is stated by the
author according to Reaumur's scale. The degrees within brackets are the
correspondent degrees of Fahrenheit's scale, added by the translator. E.
[3] Collections of the French Academy of Sciences for that year, p. 420.
[4] Chemical Nomenclature.
[5] As I shall afterwards give a definition, and explain the properties
of the liquor called _ether_, I shall only premise here, that it is a
very volatile inflammable liquor, having a considerably smaller specific
gravity than water, or even spirit of wine.--A.
[6] It would have been more satisfactory if the Author had specified the
degrees of the thermometer at which these heights of the mercury in the
barometer are produced.
[7] Vide Memoirs of the French Academy, anno 1780, p. 335.--A.
CHAP. II.
_General Views relative to the Formation and Composition of our
Atmosphere._
These views which I have taken of the formation of elastic aëriform
fluids or gasses, throw great light upon the original formation of the
atmospheres of the planets, and particularly that of our earth. We
readily conceive, that it must necessarily consist of a mixture of the
following substances: _First_, Of all bodies that are susceptible of
evaporation, or, more strictly speaking, which are capable of retaining
the state of aëriform elasticity in the temperature of our atmosphere,
and under a pressure equal to that of a column of twenty-eight inches of
quicksilver in the barometer; and, _secondly_, Of all substances,
whether liquid or solid, which are capable of being dissolved by this
mixture of different gasses.
The better to determine our ideas relating to this subject, which has
not hitherto been sufficiently considered, let us, for a moment,
conceive what change would take place in the various substances which
compose our earth, if its temperature were suddenly altered. If, for
instance, we were suddenly transported into the region of the planet
Mercury, where probably the common temperature is much superior to that
of boiling water, the water of the earth, and all the other fluids which
are susceptible of the gasseous state, at a temperature near to that of
boiling water, even quicksilver itself, would become rarified; and all
these substances would be changed into permanent aëriform fluids or
gasses, which would become part of the new atmosphere. These new species
of airs or gasses would mix with those already existing, and certain
reciprocal decompositions and new combinations would take place, until
such time as all the elective attractions or affinities subsisting
amongst all these new and old gasseous substances had operated fully;
after which, the elementary principles composing these gasses, being
saturated, would remain at rest. We must attend to this, however, that,
even in the above hypothetical situation, certain bounds would occur to
the evaporation of these substances, produced by that very evaporation
itself; for as, in proportion to the increase of elastic fluids, the
pressure of the atmosphere would be augmented, as every degree of
pressure tends, in some measure, to prevent evaporation, and as even the
most evaporable fluids can resist the operation of a very high
temperature without evaporating, if prevented by a proportionally
stronger compression, water and all other liquids being able to sustain
a red heat in Papin's digester; we must admit, that the new atmosphere
would at last arrive at such a degree of weight, that the water which
had not hitherto evaporated would cease to boil, and, of consequence,
would remain liquid; so that, even upon this supposition, as in all
others of the same nature, the increasing gravity of the atmosphere
would find certain limits which it could not exceed. We might even
extend these reflections greatly farther, and examine what change might
be produced in such situations upon stones, salts, and the greater part
of the fusible substances which compose the mass of our earth. These
would be softened, fused, and changed into fluids, &c.: But these
speculations carry me from my object, to which I hasten to return.
By a contrary supposition to the one we have been forming, if the earth
were suddenly transported into a very cold region, the water which at
present composes our seas, rivers, and springs, and probably the greater
number of the fluids we are acquainted with, would be converted into
solid mountains and hard rocks, at first diaphanous and homogeneous,
like rock crystal, but which, in time, becoming mixed with foreign and
heterogeneous substances, would become opake stones of various colours.
In this case, the air, or at least some part of the aëriform fluids
which now compose the mass of our atmosphere, would doubtless lose its
elasticity for want of a sufficient temperature to retain them in that
state: They would return to the liquid state of existence, and new
liquids would be formed, of whose properties we cannot, at present, form
the most distant idea.
These two opposite suppositions give a distinct proof of the following
corollaries: _First_, That _solidity_, _liquidity_, and _aëriform
elasticity_, are only three different states of existence of the same
matter, or three particular modifications which almost all substances
are susceptible of assuming successively, and which solely depend upon
the degree of temperature to which they are exposed; or, in other words,
upon the quantity of caloric with which they are penetrated[8]. _2dly_,
That it is extremely probable that air is a fluid naturally existing in
a state of vapour; or, as we may better express it, that our atmosphere
is a compound of all the fluids which are susceptible of the vaporous
or permanently elastic state, in the usual temperature, and under the
common pressure. _3dly_, That it is not impossible we may discover, in
our atmosphere, certain substances naturally very compact, even metals
themselves; as a metallic substance, for instance, only a little more
volatile than mercury, might exist in that situation.
Amongst the fluids with which we are acquainted, some, as water and
alkohol, are susceptible of mixing with each other in all proportions;
whereas others, on the contrary, as quicksilver, water, and oil, can
only form a momentary union; and, after being mixed together, separate
and arrange themselves according to their specific gravities. The same
thing ought to, or at least may, take place in the atmosphere. It is
possible, and even extremely probable, that, both at the first creation,
and every day, gasses are formed, which are difficultly miscible with
atmospheric air, and are continually separating from it. If these gasses
be specifically lighter than the general atmospheric mass, they must, of
course, gather in the higher regions, and form strata that float upon
the common air. The phenomena which accompany igneous meteors induce me
to believe, that there exists in the upper parts of our atmosphere a
stratum of inflammable fluid in contact with those strata of air which
produce the phenomena of the aurora borealis and other fiery meteors.--I
mean hereafter to pursue this subject in a separate treatise.
FOOTNOTES:
[8] The degree of pressure which they undergo must be taken into
account. E.
CHAP. III.
_Analysis of Atmospheric Air, and its Division into two Elastic Fluids;
the one fit for Respiration, the other incapable of being respired._
From what has been premised, it follows, that our atmosphere is composed
of a mixture of every substance capable of retaining the gasseous or
aëriform state in the common temperature, and under the usual pressure
which it experiences. These fluids constitute a mass, in some measure
homogeneous, extending from the surface of the earth to the greatest
height hitherto attained, of which the density continually decreases in
the inverse ratio of the superincumbent weight. But, as I have before
observed, it is possible that this first stratum is surmounted by
several others consisting of very different fluids.
Our business, in this place, is to endeavour to determine, by
experiments, the nature of the elastic fluids which compose the inferior
stratum of air which we inhabit. Modern chemistry has made great
advances in this research; and it will appear by the following details
that the analysis of atmospherical air has been more rigorously
determined than that of any other substance of the class. Chemistry
affords two general methods of determining the constituent principles of
bodies, the method of analysis, and that of synthesis. When, for
instance, by combining water with alkohol, we form the species of liquor
called, in commercial language, brandy or spirit of wine, we certainly
have a right to conclude, that brandy, or spirit of wine, is composed of
alkohol combined with water. We can produce the same result by the
analytical method; and in general it ought to be considered as a
principle in chemical science, never to rest satisfied without both
these species of proofs.
We have this advantage in the analysis of atmospherical air, being able
both to decompound it, and to form it a new in the most satisfactory
manner. I shall, however, at present confine myself to recount such
experiments as are most conclusive upon this head; and I may consider
most of these as my own, having either first invented them, or having
repeated those of others, with the intention of analysing atmospherical
air, in perfectly new points of view.
I took a matrass (A, fig. 14. plate II.) of about 36 cubical inches
capacity, having a long neck B C D E, of six or seven lines internal
diameter, and having bent the neck as in Plate IV. Fig. 2. so as to
allow of its being placed in the furnace M M N N, in such a manner that
the extremity of its neck E might be inserted under a bell-glass F G,
placed in a trough of quicksilver R R S S; I introduced four ounces of
pure mercury into the matrass, and, by means of a syphon, exhausted the
air in the receiver F G, so as to raise the quicksilver to L L, and I
carefully marked the height at which it stood by pasting on a slip of
paper. Having accurately noted the height of the thermometer and
barometer, I lighted a fire in the furnace M M N N, which I kept up
almost continually during twelve days, so as to keep the quicksilver
always almost at its boiling point. Nothing remarkable took place during
the first day: The Mercury, though not boiling, was continually
evaporating, and covered the interior surface of the vessels with small
drops, at first very minute, which gradually augmenting to a sufficient
size, fell back into the mass at the bottom of the vessel. On the second
day, small red particles began to appear on the surface of the mercury,
which, during the four or five following days, gradually increased in
size and number; after which they ceased to increase in either respect.
At the end of twelve days, seeing that the calcination of the mercury
did not at all increase, I extinguished the fire, and allowed the
vessels to cool. The bulk of air in the body and neck of the matrass,
and in the bell-glass, reduced to a medium of 28 inches of the
barometer and 10° (54.5°) of the thermometer, at the commencement of the
experiment was about 50 cubical inches. At the end of the experiment the
remaining air, reduced to the same medium pressure and temperature, was
only between 42 and 43 cubical inches; consequently it had lost about
1/6 of its bulk. Afterwards, having collected all the red particles,
formed during the experiment, from the running mercury in which they
floated, I found these to amount to 45 grains.
I was obliged to repeat this experiment several times, as it is
difficult in one experiment both to preserve the whole air upon which we
operate, and to collect the whole of the red particles, or calx of
mercury, which is formed during the calcination. It will often happen in
the sequel, that I shall, in this manner, give in one detail the results
of two or three experiments of the same nature.
The air which remained after the calcination of the mercury in this
experiment, and which was reduced to 5/6 of its former bulk, was no
longer fit either for respiration or for combustion; animals being
introduced into it were suffocated in a few seconds, and when a taper
was plunged into it, it was extinguished as if it had been immersed into
water.
In the next place, I took the 45 grains of red matter formed during this
experiment, which I put into a small glass retort, having a proper
apparatus for receiving such liquid, or gasseous product, as might be
extracted: Having applied a fire to the retort in a furnace, I observed
that, in proportion as the red matter became heated, the intensity of
its colour augmented. When the retort was almost red hot, the red matter
began gradually to decrease in bulk, and in a few minutes after it
disappeared altogether; at the same time 41-1/2 grains of running
mercury were collected in the recipient, and 7 or 8 cubical inches of
elastic fluid, greatly more capable of supporting both respiration and
combustion than atmospherical air, were collected in the bell-glass.
A part of this air being put into a glass tube of about an inch
diameter, showed the following properties: A taper burned in it with a
dazzling splendour, and charcoal, instead of consuming quietly as it
does in common air, burnt with a flame, attended with a decrepitating
noise, like phosphorus, and threw out such a brilliant light that the
eyes could hardly endure it. This species of air was discovered almost
at the same time by Mr Priestley, Mr Scheele, and myself. Mr Priestley
gave it the name of _dephlogisticated air_, Mr Scheele called it
_empyreal air_. At first I named it _highly respirable air_, to which
has since been substituted the term of _vital air_. We shall presently
see what we ought to think of these denominations.
In reflecting upon the circumstances of this experiment, we readily
perceive, that the mercury, during its calcination, absorbs the
salubrious and respirable part of the air, or, to speak more strictly,
the base of this respirable part; that the remaining air is a species of
mephitis, incapable of supporting combustion or respiration; and
consequently that atmospheric air is composed of two elastic fluids of
different and opposite qualities. As a proof of this important truth, if
we recombine these two elastic fluids, which we have separately obtained
in the above experiment, viz. the 42 cubical inches of mephitis, with
the 8 cubical inches of respirable air, we reproduce an air precisely
similar to that of the atmosphere, and possessing nearly the same power
of supporting combustion and respiration, and of contributing to the
calcination of metals.
Although this experiment furnishes us with a very simple means of
obtaining the two principal elastic fluids which compose our atmosphere,
separate from each other, yet it does not give us an exact idea of the
proportion in which these two enter into its composition: For the
attraction of mercury to the respirable part of the air, or rather to
its base, is not sufficiently strong to overcome all the circumstances
which oppose this union. These obstacles are the mutual adhesion of the
two constituent parts of the atmosphere for each other, and the elective
attraction which unites the base of vital air with caloric; in
consequence of these, when the calcination ends, or is at least carried
as far as is possible, in a determinate quantity of atmospheric air,
there still remains a portion of respirable air united to the mephitis,
which the mercury cannot separate. I shall afterwards show, that, at
least in our climate, the atmospheric air is composed of respirable and
mephitic airs, in the proportion of 27 and 73; and I shall then discuss
the causes of the uncertainty which still exists with respect to the
exactness of that proportion.
Since, during the calcination of mercury, air is decomposed, and the
base of its respirable part is fixed and combined with the mercury, it
follows, from the principles already established, that caloric and light
must be disengaged during the process: But the two following causes
prevent us from being sensible of this taking place: As the calcination
lasts during several days, the disengagement of caloric and light,
spread out in a considerable space of time, becomes extremely small for
each particular moment of that time, so as not to be perceptible; and,
in the next place, the operation being carried on by means of fire in a
furnace, the heat produced by the calcination itself becomes confounded
with that proceeding from the furnace. I might add the respirable part
of the air, or rather its base, in entering into combination with the
mercury, does not part with all the caloric which it contained, but
still retains a part of it after forming the new compound; but the
discussion of this point, and its proofs from experiment, do not belong
to this part of our subject.
It is, however, easy to render this disengagement of caloric and light
evident to the senses, by causing the decomposition of air to take place
in a more rapid manner. And for this purpose, iron is excellently
adapted, as it possesses a much stronger affinity for the base of
respirable air than mercury. The elegant experiment of Mr Ingenhouz,
upon the combustion of iron, is well known. Take a piece of fine iron
wire, twisted into a spiral, (BC, Plate IV. Fig. 17.) fix one of its
extremities B into the cork A, adapted to the neck of the bottle DEFG,
and fix to the other extremity of the wire C, a small morsel of tinder.
Matters being thus prepared, fill the bottle DEFG with air deprived of
its mephitic part; then light the tinder, and introduce it quickly with
the wire upon which it is fixed, into the bottle which you stop up with
the cork A, as is shown in the figure (17 Plate IV.) The instant the
tinder comes into contact with the vital air it begins to burn with
great intensity; and, communicating the inflammation to the iron-wire,
it too takes fire, and burns rapidly, throwing out brilliant sparks,
which fall to the bottom of the vessel in rounded globules, which become
black in cooling, but retain a degree of metallic splendour. The iron
thus burnt is more brittle even than glass, and is easily reduced into
powder, and is still attractable by the magnet, though not so powerfully
as it was before combustion. As Mr Ingenhouz has neither examined the
change produced on iron, nor upon the air by this operation, I have
repeated the experiment under different circumstances, in an apparatus
adapted to answer my particular views, as follows.
Having filled a bell-glass (A, Plate IV. Fig. 3.) of about six pints
measure, with pure air, or the highly respirable part of air, I
transported this jar by means of a very flat vessel, into a quicksilver
bath in the bason BC, and I took care to render the surface of the
mercury perfectly dry both within and without the jar with blotting
paper. I then provided a small capsule of china-ware D, very flat and
open, in which I placed some small pieces of iron, turned spirally, and
arranged in such a way as seemed most favourable for the combustion
being communicated to every part. To the end of one of these pieces of
iron was fixed a small morsel of tinder, to which was added about the
sixteenth part of a grain of phosphorus, and, by raising the bell-glass
a little, the china capsule, with its contents, were introduced into the
pure air. I know that, by this means, some common air must mix with the
pure air in the glass; but this, when it is done dexterously, is so very
trifling, as not to injure the success of the experiment. This being
done, a part of the air is sucked out from the bell-glass, by means of a
syphon GHI, so as to raise the mercury within the glass to EF; and, to
prevent the mercury from getting into the syphon, a small piece of paper
is twisted round its extremity. In sucking out the air, if the motion of
the lungs only be used, we cannot make the mercury rise above an inch or
an inch and a half; but, by properly using the muscles of the mouth, we
can, without difficulty, cause it to rise six or seven inches.
I next took an iron wire, (MN, Plate IV. Fig. 16.) properly bent for the
purpose, and making it red hot in the fire, passed it through the
mercury into the receiver, and brought it in contact with the small
piece of phosphorus attached to the tinder. The phosphorus instantly
takes fire, which communicates to the tinder, and from that to the iron.
When the pieces have been properly arranged, the whole iron burns, even
to the last particle, throwing out a white brilliant light similar to
that of Chinese fireworks. The great heat produced by this combustion
melts the iron into round globules of different sizes, most of which
fall into the China cup; but some are thrown out of it, and swim upon
the surface of the mercury. At the beginning of the combustion, there is
a slight augmentation in the volume of the air in the bell-glass, from
the dilatation caused by the heat; but, presently afterwards, a rapid
diminution of the air takes place, and the mercury rises in the glass;
insomuch that, when the quantity of iron is sufficient, and the air
operated upon is very pure, almost the whole air employed is absorbed.
It is proper to remark in this place, that, unless in making experiments
for the purpose of discovery, it is better to be contented with burning
a moderate quantity of iron; for, when this experiment is pushed too
far, so as to absorb much of the air, the cup D, which floats upon the
quicksilver, approaches too near the bottom of the bell-glass; and the
great heat produced, which is followed by a very sudden cooling,
occasioned by the contact of the cold mercury, is apt to break the
glass. In which case, the sudden fall of the column of mercury, which
happens the moment the least flaw is produced in the glass, causes such
a wave, as throws a great part of the quicksilver from the bason. To
avoid this inconvenience, and to ensure success to the experiment, one
gross and a half of iron is sufficient to burn in a bell-glass, which
holds about eight pints of air. The glass ought likewise to be strong,
that it may be able to bear the weight of the column of mercury which it
has to support.
By this experiment, it is not possible to determine, at one time, both
the additional weight acquired by the iron, and the changes which have
taken place in the air. If it is wished to ascertain what additional
weight has been gained by the iron, and the proportion between that and
the air absorbed, we must carefully mark upon the bell-glass, with a
diamond, the height of the mercury, both before and after the
experiment[9]. After this, the syphon (GH, Pl. IV. fig. 3.) guarded, as
before, with a bit of paper, to prevent its filling with mercury, is to
be introduced under the bell-glass, having the thumb placed upon the
extremity, G, of the syphon, to regulate the passage of the air; and by
this means the air is gradually admitted, so as to let the mercury fall
to its level. This being done, the bell-glass is to be carefully
removed, the globules of melted iron contained in the cup, and those
which have been scattered about, and swim upon the mercury, are to be
accurately collected, and the whole is to be weighed. The iron will be
found in that state called _martial ethiops_ by the old chemists,
possessing a degree of metallic brilliancy, very friable, and readily
reducible into powder, under the hammer, or with a pestle and mortar. If
the experiment has succeeded well, from 100 grains of iron will be
obtained 135 or 136 grains of ethiops, which is an augmentation of 35
per cent.
If all the attention has been paid to this experiment which it deserves,
the air will be found diminished in weight exactly equal to what the
iron has gained. Having therefore burnt 100 grains of iron, which has
acquired an additional weight of 35 grains, the diminution of air will
be found exactly 70 cubical inches; and it will be found, in the sequel,
that the weight of vital air is pretty nearly half a grain for each
cubical inch; so that, in effect, the augmentation of weight in the one
exactly coincides with the loss of it in the other.
I shall observe here, once for all, that, in every experiment of this
kind, the pressure and temperature of the air, both before and after the
experiment, must be reduced, by calculation, to a common standard of 10°
(54.5°) of the thermometer, and 28 inches of the barometer. Towards the
end of this work, the manner of performing this very necessary reduction
will be found accurately detailed.
If it be required to examine the nature of the air which remains after
this experiment, we must operate in a somewhat different manner. After
the combustion is finished, and the vessels have cooled, we first take
out the cup, and the burnt iron, by introducing the hand through the
quicksilver, under the bell-glass; we next introduce some solution of
potash, or caustic alkali, or of the sulphuret of potash, or such other
substance as is judged proper for examining their action upon the
residuum of air. I shall, in the sequel, give an account of these
methods of analysing air, when I have explained the nature of these
different substances, which are only here in a manner accidentally
mentioned. After this examination, so much water must be let into the
glass as will displace the quicksilver, and then, by means of a shallow
dish placed below the bell-glass, it is to be removed into the common
water pneumato-chemical apparatus, where the air remaining may be
examined at large, and with great facility.
When very soft and very pure iron has been employed in this experiment,
and, if the combustion has been performed in the purest respirable or
vital air, free from all admixture of the noxious or mephitic part, the
air which remains after the combustion will be found as pure as it was
before; but it is difficult to find iron entirely free from a small
portion of charry matter, which is chiefly abundant in steel. It is
likewise exceedingly difficult to procure the pure air perfectly free
from some admixture of mephitis, with which it is almost always
contaminated; but this species of noxious air does not, in the smallest
degree, disturb the result of the experiment, as it is always found at
the end exactly in the same proportion as at the beginning.
I mentioned before, that we have two ways of determining the constituent
parts of atmospheric air, the method of analysis, and that by synthesis.
The calcination of mercury has furnished us with an example of each of
these methods, since, after having robbed the respirable part of its
base, by means of the mercury, we have restored it, so as to recompose
an air precisely similar to that of the atmosphere. But we can equally
accomplish this synthetic composition of atmospheric air, by borrowing
the materials of which it is composed from different kingdoms of nature.
We shall see hereafter that, when animal substances are dissolved in the
nitric acid, a great quantity of gas is disengaged, which extinguishes
light, and is unfit for animal respiration, being exactly similar to the
noxious or mephitic part of atmospheric air. And, if we take 73 parts,
by weight, of this elastic fluid, and mix it with 27 parts of highly
respirable air, procured from calcined mercury, we will form an elastic
fluid precisely similar to atmospheric air in all its properties.
There are many other methods of separating the respirable from the
noxious part of the atmospheric air, which cannot be taken notice of in
this part, without anticipating information, which properly belongs to
the subsequent chapters. The experiments already adduced may suffice for
an elementary treatise; and, in matters of this nature, the choice of
our evidences is of far greater consequence than their number.
I shall close this article, by pointing out the property which
atmospheric air, and all the known gasses, possess of dissolving water,
which is of great consequence to be attended to in all experiments of
this nature. Mr Saussure found, by experiment, that a cubical foot of
atmospheric air is capable of holding 12 grains of water in solution:
Other gasses, as the carbonic acid, appear capable of dissolving a
greater quantity; but experiments are still wanting by which to
determine their several proportions. This water, held in solution by
gasses, gives rise to particular phenomena in many experiments, which
require great attention, and which has frequently proved the source of
great errors to chemists in determining the results of their
experiments.
FOOTNOTES:
[9] It will likewise be necessary to take care that the air contained in
the glass, both before and after the experiment, be reduced to a common
temperature and pressure, otherwise the results of the following
calculations will be fallacious.--E.
CHAP. IV.
_Nomenclature of the several Constituent Parts of Atmospheric Air._
Hitherto I have been obliged to make use of circumlocution, to express
the nature of the several substances which constitute our atmosphere,
having provisionally used the terms of _respirable_ and _noxious_, or
_non-respirable parts of the air_. But the investigations I mean to
undertake require a more direct mode of expression; and, having now
endeavoured to give simple and distinct ideas of the different
substances which enter into the composition of the atmosphere, I shall
henceforth express these ideas by words equally simple.
The temperature of our earth being very near to that at which water
becomes solid, and reciprocally changes from solid to fluid, and as this
phenomenon takes place frequently under our observation, it has very
naturally followed, that, in the languages of at least every climate
subjected to any degree of winter, a term has been used for signifying
water in the state of solidity, when deprived of its caloric. The same,
however, has not been found necessary with respect to water reduced to
the state of vapour by an additional dose of caloric; since those
persons who do not make a particular study of objects of this kind, are
still ignorant that water, when in a temperature only a little above the
boiling heat, is changed into an elastic aëriform fluid, susceptible,
like all other gasses, of being received and contained in vessels, and
preserving its gasseous form so long as it remains at the temperature of
80° (212°), and under a pressure not exceeding 28 inches of the
mercurial barometer. As this phenomenon has not been generally observed,
no language has used a particular term for expressing water in this
state[10]; and the same thing occurs with all fluids, and all
substances, which do not evaporate in the common temperature, and under
the usual pressure of our atmosphere.
For similar reasons, names have not been given to the liquid or concrete
states of most of the aëriform fluids: These were not known to arise
from the combination of caloric with certain bases; and, as they had not
been seen either in the liquid or solid states, their existence, under
these forms, was even unknown to natural philosophers.
We have not pretended to make any alteration upon such terms as are
sanctified by ancient custom; and, therefore, continue to use the words
_water_ and _ice_ in their common acceptation: We likewise retain the
word _air_, to express that collection of elastic fluids which composes
our atmosphere; but we have not thought it necessary to preserve the
same respect for modern terms, adopted by latter philosophers, having
considered ourselves as at liberty to reject such as appeared liable to
occasion erroneous ideas of the substances they are meant to express,
and either to substitute new terms, or to employ the old ones, after
modifying them in such a manner as to convey more determinate ideas. New
words have been drawn, chiefly from the Greek language, in such a manner
as to make their etymology convey some idea of what was meant to be
represented; and these we have always endeavoured to make short, and of
such a nature as to be changeable into adjectives and verbs.
Following these principles, we have, after Mr Macquer's example,
retained the term _gas_, employed by Vanhelmont, having arranged the
numerous class of elastic aëriform fluids under that name, excepting
only atmospheric air. _Gas_, therefore, in our nomenclature, becomes a
generic term, expressing the fullest degree of saturation in any body
with caloric; being, in fact, a term expressive of a mode of existence.
To distinguish each species of gas, we employ a second term from the
name of the base, which, saturated with caloric, forms each particular
gas. Thus, we name water combined to saturation with caloric, so as to
form an elastic fluid, _aqueous gas_; ether, combined in the same
manner, _etherial gas_; the combination of alkohol with caloric, becomes
_alkoholic gas_; and, following the same principles, we have _muriatic
acid gas_, _ammoniacal gas_, and so on of every substance susceptible of
being combined with caloric, in such a manner as to assume the gasseous
or elastic aëriform state.
We have already seen, that the atmospheric air is composed of two
gasses, or aëriform fluids, one of which is capable, by respiration, of
contributing to animal life, and in which metals are calcinable, and
combustible bodies may burn; the other, on the contrary, is endowed with
directly opposite qualities; it cannot be breathed by animals, neither
will it admit of the combustion of inflammable bodies, nor of the
calcination of metals. We have given to the base of the former, or
respirable portion of the air, the name of _oxygen_, from [Greek: oxys]
_acidum_, and [Greek: geinomas], _gignor_; because, in reality, one of
the most general properties of this base is to form acids, by combining
with many different substances. The union of this base with caloric we
term _oxygen gas_, which is the same with what was formerly called
_pure_, or _vital air_. The weight of this gas, at the temperature of
10° (54.50), and under a pressure equal to 28 inches of the barometer,
is half a grain for each cubical inch, or one ounce and a half to each
cubical foot.
The chemical properties of the noxious portion of atmospheric air being
hitherto but little known, we have been satisfied to derive the name of
its base from its known quality of killing such animals as are forced to
breathe it, giving it the name of _azote_, from the Greek privitive
particle [Greek: a] and [Greek: xaê], vita; hence the name of the
noxious part of atmospheric air is _azotic gas_; the weight of which, in
the same temperature, and under the same pressure, is 1 oz. 2 gros
and 48 grs. to the cubical foot, or 0.4444 of a grain to the cubical
inch. We cannot deny that this name appears somewhat extraordinary; but
this must be the case with all new terms, which cannot be expected to
become familiar until they have been some time in use. We long
endeavoured to find a more proper designation without success; it was at
first proposed to call it _alkaligen gas_, as, from the experiments of
Mr Berthollet, it appears to enter into the composition of ammoniac, or
volatile alkali; but then, we have as yet no proof of its making one of
the constituent elements of the other alkalies; beside, it is proved to
compose a part of the nitric acid, which gives as good reason to have
called it _nitrigen_. For these reasons, finding it necessary to reject
any name upon systematic principles, we have considered that we run no
risk of mistake in adopting the terms of _azote_, and _azotic gas_,
which only express a matter of fact, or that property which it
possesses, of depriving such animals as breathe it of their lives.
I should anticipate subjects more properly reserved for the subsequent
chapters, were I in this place to enter upon the nomenclature of the
several species of gasses: It is sufficient, in this part of the work,
to establish the principles upon which their denominations are founded.
The principal merit of the nomenclature we have adopted is, that, when
once the simple elementary substance is distinguished by an appropriate
term, the names of all its compounds derive readily, and necessarily,
from this first denomination.
FOOTNOTES:
[10] In English, the word _steam_ is exclusively appropriated to water
in the state of vapour. E.
CHAP. V.
_Of the Decomposition of Oxygen Gas by Sulphur, Phosphorus, and
Charcoal--and of the Formation of Acids in general._
In performing experiments, it is a necessary principle, which ought
never to be deviated from, that they be simplified as much as possible,
and that every circumstance capable of rendering their results
complicated be carefully removed. Wherefore, in the experiments which
form the object of this chapter, we have never employed atmospheric air,
which is not a simple substance. It is true, that the azotic gas, which
forms a part of its mixture, appears to be merely passive during
combustion and calcination; but, besides that it retards these
operations very considerably, we are not certain but it may even alter
their results in some circumstances; for which reason, I have thought it
necessary to remove even this possible cause of doubt, by only making
use of pure oxygen gas in the following experiments, which show the
effects produced by combustion in that gas; and I shall advert to such
differences as take place in the results of these, when the oxygen gas,
or pure vital air, is mixed, in different proportions, with azotic gas.
Having filled a bell-glass (A. Pl. iv. fig. 3), of between five and six
pints measure, with oxygen gas, I removed it from the water trough,
where it was filled, into the quicksilver bath, by means of a shallow
glass dish slipped underneath, and having dried the mercury, I
introduced 61-1/4 grains of Kunkel's phosphorus in two little China
cups, like that represented at D, fig. 3. under the glass A; and that I
might set fire to each of the portions of phosphorus separately, and to
prevent the one from catching fire from the other, one of the dishes was
covered with a piece of flat glass. I next raised the quicksilver in the
bell-glass up to E F, by sucking out a sufficient portion of the gas by
means of the syphon G H I. After this, by means of the crooked iron wire
(fig. 16.), made red hot, I set fire to the two portions of phosphorus
successively, first burning that portion which was not covered with the
piece of glass. The combustion was extremely rapid, attended with a very
brilliant flame, and considerable disengagement of light and heat. In
consequence of the great heat induced, the gas was at first much
dilated, but soon after the mercury returned to its level, and a
considerable absorption of gas took place; at the same time, the whole
inside of the glass became covered with white light flakes of concrete
phosphoric acid.
At the beginning of the experiment, the quantity of oxygen gas, reduced,
as above directed, to a common standard, amounted to 162 cubical inches;
and, after the combustion was finished, only 23-1/4 cubical inches,
likewise reduced to the standard, remained; so that the quantity of
oxygen gas absorbed during the combustion was 138-3/4 cubical inches,
equal to 69.375 grains.
A part of the phosphorus remained unconsumed in the bottom of the cups,
which being washed on purpose to separate the acid, weighed about 16-1/4
grains; so that about 45 grains of phosphorus had been burned: But, as
it is hardly possible to avoid an error of one or two grains, I leave
the quantity so far qualified. Hence, as nearly 45 grains of phosphorus
had, in this experiment, united with 69.375 grains of oxygen, and as no
gravitating matter could have escaped through the glass, we have a right
to conclude, that the weight of the substance resulting from the
combustion in form of white flakes, must equal that of the phosphorus
and oxygen employed, which amounts to 114.375 grains. And we shall
presently find, that these flakes consisted entirely of a solid or
concrete acid. When we reduce these weights to hundredth parts, it will
be found, that 100 parts of phosphorus require 154 parts of oxygen for
saturation, and that this combination will produce 254 parts of concrete
phosphoric acid, in form of white fleecy flakes.
This experiment proves, in the most convincing manner, that, at a
certain degree of temperature, oxygen possesses a stronger elective
attraction, or affinity, for phosphorus than for caloric; that, in
consequence of this, the phosphorus attracts the base of oxygen gas from
the caloric, which, being set free, spreads itself over the surrounding
bodies. But, though this experiment be so far perfectly conclusive, it
is not sufficiently rigorous, as, in the apparatus described, it is
impossible to ascertain the weight of the flakes of concrete acid which
are formed; we can therefore only determine this by calculating the
weights of oxygen and phosphorus employed; but as, in physics, and in
chemistry, it is not allowable to suppose what is capable of being
ascertained by direct experiment, I thought it necessary to rep at this
experiment, as follows, upon a larger scale, and by means of a different
apparatus.
I took a large glass baloon (A. Pl. iv. fig. 4.) with an opening three
inches diameter, to which was fitted a crystal stopper ground with
emery, and pierced with two holes for the tubes yyy, xxx. Before
shutting the baloon with its stopper, I introduced the support BC,
surmounted by the china cup D, containing 150 grs. of phosphorus; the
stopper was then fitted to the opening of the baloon, luted with fat
lute, and covered with slips of linen spread with quick-lime and white
of eggs: When the lute was perfectly dry, the weight of the whole
apparatus was determined to within a grain, or a grain and a half. I
next exhausted the baloon, by means of an air pump applied to the tube
XXX, and then introduced oxygen gas by means of the tube yyy, having a
stop cock adapted to it. This kind of experiment is most readily and
most exactly performed by means of the hydro-pneumatic machine described
by Mr Meusnier and me in the Memoirs of the Academy for 1782, pag. 466.
and explained in the latter part of this work, with several important
additions and corrections since made to it by Mr Meusnier. With this
instrument we can readily ascertain, in the most exact manner, both the
quantity of oxygen gas introduced into the baloon, and the quantity
consumed during the course of the experiment.
When all things were properly disposed, I set fire to the phosphorus
with a burning glass. The combustion was extremely rapid, accompanied
with a bright flame, and much heat; as the operation went on, large
quantities of white flakes attached themselves to the inner surface of
the baloon, so that at last it was rendered quite opake. The quantity
of these flakes at last became so abundant, that, although fresh oxygen
gas was continually supplied, which ought to have supported the
combustion, yet the phosphorus was soon extinguished. Having allowed the
apparatus to cool completely, I first ascertained the quantity of oxygen
gas employed, and weighed the baloon accurately, before it was opened. I
next washed, dried, and weighed the small quantity of phosphorus
remaining in the cup, on purpose to determine the whole quantity of
phosphorus consumed in the experiment; this residuum of the phosphorus
was of a yellow ochrey colour. It is evident, that by these several
precautions, I could easily determine, 1st, the weight of the phosphorus
consumed; 2d, the weight of the flakes produced by the combustion; and,
3d, the weight of the oxygen which had combined with the phosphorus.
This experiment gave very nearly the same results with the former, as it
proved that the phosphorus, during its combustion, had absorbed a little
more than one and a half its weight of oxygen; and I learned with more
certainty, that the weight of the new substance, produced in the
experiment, exactly equalled the sum of the weights of the phosphorus
consumed, and oxygen absorbed, which indeed was easily determinable _a
priori_. If the oxygen gas employed be pure, the residuum after
combustion is as pure as the gas employed; this proves that nothing
escapes from the phosphorus, capable of altering the purity of the
oxygen gas, and that the only action of the phosphorus is to separate
the oxygen from the caloric, with which it was before united.
I mentioned above, that when any combustible body is burnt in a hollow
sphere of ice, or in an apparatus properly constructed upon that
principle, the quantity of ice melted during the combustion is an exact
measure of the quantity of caloric disengaged. Upon this head, the
memoir given by M. de la Place and me, Aº. 1780, p. 355, may be
consulted. Having submitted the combustion of phosphorus to this trial,
we found that one pound of phosphorus melted a little more than 100
pounds of ice during its combustion.
The combustion of phosphorus succeeds equally well in atmospheric air as
in oxygen gas, with this difference, that the combustion is vastly
slower, being retarded by the large proportion of azotic gas mixed with
the oxygen gas, and that only about one-fifth part of the air employed
is absorbed, because as the oxygen gas only is absorbed, the proportion
of the azotic gas becomes so great toward the close of the experiment,
as to put an end to the combustion.
I have already shown, that phosphorus is changed by combustion into an
extremely light, white, flakey matter; and its properties are entirely
altered by this transformation: From being insoluble in water, it
becomes not only soluble, but so greedy of moisture, as to attract the
humidity of the air with astonishing rapidity; by this means it is
converted into a liquid, considerably more dense, and of more specific
gravity than water. In the state of phosphorus before combustion, it had
scarcely any sensible taste, by its union with oxygen it acquires an
extremely sharp and sour taste: in a word, from one of the class of
combustible bodies, it is changed into an incombustible substance, and
becomes one of those bodies called acids.
This property of a combustible substance to be converted into an acid,
by the addition of oxygen, we shall presently find belongs to a great
number of bodies: Wherefore, strict logic requires that we should adopt
a common term for indicating all these operations which produce
analogous results; this is the true way to simplify the study of
science, as it would be quite impossible to bear all its specifical
details in the memory, if they were not classically arranged. For this
reason, we shall distinguish this conversion of phosphorus into an acid,
by its union with oxygen, and in general every combination of oxygen
with a combustible substance, by the term of _oxygenation_: from which
I shall adopt the verb to _oxygenate_, and of consequence shall say,
that in _oxygenating_ phosphorus we convert it into an acid.
Sulphur is likewise a combustible body, or, in other words, it is a body
which possesses the power of decomposing oxygen gas, by attracting the
oxygen from the caloric with which it was combined. This can very easily
be proved, by means of experiments quite similar to those we have given
with phosphorus; but it is necessary to premise, that in these
operations with sulphur, the same accuracy of result is not to be
expected as with phosphorus; because the acid which is formed by the
combustion of sulphur is difficultly condensible, and because sulphur
burns with more difficulty, and is soluble in the different gasses. But
I can safely assert, from my own experiments, that sulphur in burning
absorbs oxygen gas; that the resulting acid is considerably heavier than
the sulphur burnt; that its weight is equal to the sum of the weights of
the sulphur which has been burnt, and of the oxygen absorbed; and,
lastly that this acid is weighty, incombustible, and miscible with water
in all proportions: The only uncertainty remaining upon this head, is
with regard to the proportions of sulphur and of oxygen which enter into
the composition of the acid.
Charcoal, which, from all our present knowledge regarding it, must be
considered as a simple combustible body, has likewise the property of
decomposing oxygen gas, by absorbing its base from the caloric: But the
acid resulting from this combustion does not condense in the common
temperature; under the pressure of our atmosphere, it remains in the
state of gas, and requires a large proportion of water to combine with
or be dissolved in. This acid has, however, all the known properties of
other acids, though in a weaker degree, and combines, like them, with
all the bases which are susceptible of forming neutral salts.
The combustion of charcoal in oxygen gas, may be effected like that of
phosphorus in the bell-glass, (A. Pl. IV. fig. 3.) placed over mercury:
but, as the heat of red hot iron is not sufficient to set fire to the
charcoal, we must add a small morsel of tinder, with a minute particle
of phosphorus, in the same manner as directed in the experiment for the
combustion of iron. A detailed account of this experiment will be found
in the memoirs of the academy for 1781, p. 448. By that experiment it
appears, that 28 parts by weight of charcoal require 72 parts of oxygen
for saturation, and that the aëriform acid produced is precisely equal
in weight to the sum of the weights of the charcoal and oxygen gas
employed. This aëriform acid was called fixed or fixable air by the
chemists who first discovered it; they did not then know whether it was
air resembling that of the atmosphere, or some other elastic fluid,
vitiated and corrupted by combustion; but since it is now ascertained to
be an acid, formed like all others by the oxygenation of its peculiar
base, it is obvious that the name of fixed air is quite ineligible[11].
By burning charcoal in the apparatus mentioned p. 60, Mr de la Place and
I found that one lib. of charcoal melted 96 libs. 6 oz. of ice;
that, during the combustion, 2 libs. 9 oz. 1 gros. 10 grs. of
oxygen were absorbed, and that 3 libs. 9 oz. 1 gros. 10 grs. of
acid gas were formed. This gas weighs 0.695 parts of a grain for each
cubical inch, in the common standard temperature and pressure mentioned
above, so that 34,242 cubical inches of acid gas are produced by the
combustion of one pound of charcoal.
I might multiply these experiments, and show by a numerous succession of
facts, that all acids are formed by the combustion of certain
substances; but I am prevented from doing so in place, by the plan
which I have laid down, of proceeding only from facts already
ascertained, to such as are unknown, and of drawing my examples only
from circumstances already explained. In the mean time, however, the
three examples above cited may suffice for giving a clear and accurate
conception of the manner in which acids are formed. By these it may be
clearly seen, that oxygen is an element common to them all, which
constitutes their acidity; and that they differ from each other,
according to the nature of the oxygenated or acidified substance. We
must therefore, in every acid, carefully distinguish between the
acidifiable, base, which Mr de Morveau calls the radical, and the
acidifiing principle or oxygen.
FOOTNOTES:
[11] It may be proper to remark, though here omitted by the author,
that, in conformity with the general principles of the new nomenclature,
this acid is by Mr Lavoisier and his coleagues called the carbonic acid,
and when in the aëriform state carbonic acid gas. E.
CHAP. VI.
_Of the Nomenclature of Acids in general, and particularly of those
drawn from Nitre and Sea-Salt._
It becomes extremely easy, from the principles laid down in the
preceding chapter, to establish a systematic nomenclature for the acids:
The word _acid_, being used as a generic term, each acid falls to be
distinguished in language, as in nature, by the name of its base or
radical. Thus, we give the generic name of acids to the products of the
combustion or oxygenation of phosphorus, of sulphur, and of charcoal;
and these products are respectively named, the _phosphoric acid_, the
_sulphuric acid_, and the _carbonic acid_.
There is however, a remarkable circumstance in the oxygenation of
combustible bodies, and of a part of such bodies as are convertible into
acids, that they are susceptible of different degrees of saturation with
oxygen, and that the resulting acids, though formed by the union of the
same elements, are possessed of different properties, depending upon
that difference of proportion. Of this, the phosphoric acid, and more
especially the sulphuric, furnishes us with examples. When sulphur is
combined with a small proportion of oxygen, it forms, in this first or
lower degree of oxygenation, a volatile acid, having a penetrating
odour, and possessed of very particular qualities. By a larger
proportion of oxygen, it is changed into a fixed, heavy acid, without
any odour, and which, by combination with other bodies, gives products
quite different from those furnished by the former. In this instance,
the principles of our nomenclature seem to fail; and it seems difficult
to derive such terms from the name of the acidifiable base, as shall
distinctly express these two degrees of saturation, or oxygenation,
without circumlocution. By reflection, however, upon the subject, or
perhaps rather from the necessity of the case, we have thought it
allowable to express these varieties in the oxygenation of the acids, by
simply varying the termination of their specific names. The volatile
acid produced from sulphur was anciently known to Stahl under the name
of _sulphurous_ acid[12]. We have preserved that term for this acid
from sulphur under-saturated with oxygen; and distinguish the other, or
completely saturated or oxygenated acid, by the name of _sulphuric_
acid. We shall therefore say, in this new chemical language, that
sulphur, in combining with oxygen, is susceptible of two degrees of
saturation; that the first, or lesser degree, constitutes sulphurous
acid, which is volatile and penetrating; whilst the second, or higher
degree of saturation, produces sulphuric acid, which is fixed and
inodorous. We shall adopt this difference of termination for all the
acids which assume several degrees of saturation. Hence we have a
phosphorous and a phosphoric acid, an acetous and an acetic acid; and so
on, for others in similar circumstances.
This part of chemical science would have been extremely simple, and the
nomenclature of the acids would not have been at all perplexed, as it is
now in the old nomenclature, if the base or radical of each acid had
been known when the acid itself was discovered. Thus, for instance,
phosphorus being a known substance before the discovery of its acid,
this latter was rightly distinguished by a term drawn from the name of
its acidifiable base. But when, on the contrary, an acid happened to be
discovered before its base, or rather, when the acidifiable base from
which it was formed remained unknown, names were adopted for the two,
which have not the smallest connection; and thus, not only the memory
became burthened with useless appellations, but even the minds of
students, nay even of experienced chemists, became filled with false
ideas, which time and reflection alone is capable of eradicating. We may
give an instance of this confusion with respect to the acid sulphur: The
former chemists having procured this acid from the vitriol of iron, gave
it the name of the vitriolic acid from the name of the substance which
produced it; and they were then ignorant that the acid procured from
sulphur by combustion was exactly the same.
The same thing happened with the aëriform acid formerly called _fixed
air_; it not being known that this acid was the result of combining
charcoal with oxygen, a variety of denominations have been given to it,
not one of which conveys just ideas of its nature or origin. We have
found it extremely easy to correct and modify the ancient language with
respect to these acids proceeding from known bases, having converted the
name of _vitriolic acid_ into that of _sulphuric_, and the name of
_fixed air_ into that of _carbonic acid_; but it is impossible to follow
this plan with the acids whose bases are still unknown; with these we
have been obliged to use a contrary plan, and, instead of forming the
name of the acid from that of its base, have been forced to denominate
the unknown base from the name of the known acid, as happens in the case
of the acid which is procured from sea salt.
To disengage this acid from the alkaline base with which it is combined,
we have only to pour sulphuric acid upon sea-salt, immediately a brisk
effervescence takes place, white vapours arise, of a very penetrating
odour, and, by only gently heating the mixture, all the acid is driven
off. As, in the common temperature and pressure of our atmosphere, this
acid is naturally in the state of gas, we must use particular
precautions for retaining it in proper vessels. For small experiments,
the most simple and most commodious apparatus consists of a small retort
G, (Pl. V. Fig. 5.), into which the sea-salt is introduced, well
dried[13], we then pour on some concentrated sulphuric acid, and
immediately introduce the beak of the retort under little jars or
bell-glasses A, (same Plate and Fig.), previously filled with
quicksilver. In proportion as the acid gas is disengaged, it passes into
the jar, and gets to the top of the quicksilver, which it displaces.
When the disengagement of the gas slackens, a gentle heat is applied to
the retort, and gradually increased till nothing more passes over. This
acid gas has a very strong affinity with water, which absorbs an
enormous quantity of it, as is proved by introducing a very thin layer
of water into the glass which contains the gas; for, in an instant, the
whole acid gas disappears, and combines with the water.
This latter circumstance is taken advantage of in laboratories and
manufactures, on purpose to obtain the acid of sea-salt in a liquid
form; and for this purpose the apparatus (Pl. IV. Fig. 1.) is employed.
It consists, 1st, of a tubulated retort A, into which the sea-salt, and
after it the sulphuric acid, are introduced through the opening H; 2d,
of the baloon or recipient c, b, intended for containing the small
quantity of liquid which passes over during the process; and, 3d, of a
set of bottles, with two mouths, L, L, L, L, half filled with water,
intended for absorbing the gas disengaged by the distillation. This
apparatus will be more amply described in the latter part of this work.
Although we have not yet been able, either to compose or to decompound
this acid of sea-salt, we cannot have the smallest doubt that it, like
all other acids, is composed by the union of oxygen with an acidifiable
base. We have therefore called this unknown substance the _muriatic
base_, or _muriatic radical_, deriving this name, after the example of
Mr Bergman and Mr de Morveau, from the Latin word _muria_, which was
anciently used to signify sea-salt. Thus, without being able exactly to
determine the component parts of _muriatic acid_, we design, by that
term, a volatile acid, which retains the form of gas in the common
temperature and pressure of our atmosphere, which combines with great
facility, and in great quantity, with water, and whose acidifiable base
adheres so very intimately with oxygen, that no method has hitherto been
devised for separating them. If ever this acidifiable base of the
muriatic acid is discovered to be a known substance, though now unknown
in that capacity, it will be requisite to change its present
denomination for one analogous with that of its base.
In common with sulphuric acid, and several other acids, the muriatic is
capable of different degrees of oxygenation; but the excess of oxygen
produces quite contrary effects upon it from what the same circumstance
produces upon the acid of sulphur. The lower degree of oxygenation
converts sulphur into a volatile gasseous acid, which only mixes in
small proportions with water, whilst a higher oxygenation forms an acid
possessing much stronger acid properties, which is very fixed and cannot
remain in the state of gas but in a very high temperature, which has no
smell, and which mixes in large proportion with water. With muriatic
acid, the direct reverse takes place; an additional saturation with
oxygen renders it more volatile, of a more penetrating odour, less
miscible with water, and diminishes its acid properties. We were at
first inclined to have denominated these two degrees of saturation in
the same manner as we had done with the acid of sulphur, calling the
less oxygenated _muriatous acid_, and that which is more saturated with
oxygen _muriatic acid_: But, as this latter gives very particular
results in its combinations, and as nothing analogous to it is yet known
in chemistry, we have left the name of muriatic acid to the less
saturated, and give the latter the more compounded appellation of
_oxygenated muriatic acid_.
Although the base or radical of the acid which is extracted from nitre
or saltpetre be better known, we have judged proper only to modify its
name in the same manner with that of the muriatic acid. It is drawn from
nitre, by the intervention of sulphuric acid, by a process similar to
that described for extracting the muriatic acid, and by means of the
same apparatus (Pl. IV. Fig. 1.). In proportion as the acid passes over,
it is in part condensed in the baloon or recipient, and the rest is
absorbed by the water contained in the bottles L,L,L,L; the water
becomes first green, then blue, and at last yellow, in proportion to
the concentration of the acid. During this operation, a large quantity
of oxygen gas, mixed with a small proportion of azotic gas, is
disengaged.
This acid, like all others, is composed of oxygen, united to an
acidifiable base, and is even the first acid in which the existence of
oxygen was well ascertained. Its two constituent elements are but weakly
united, and are easily separated, by presenting any substance with which
oxygen has a stronger affinity than with the acidifiable base peculiar
to this acid. By some experiments of this kind, it was first discovered
that azote, or the base of mephitis or azotic gas, constituted its
acidifiable base or radical; and consequently that the acid of nitre was
really an azotic acid, having azote for its base, combined with oxygen.
For these reasons, that we might be consistent with our principles, it
appeared necessary, either to call the acid by the name of _azotic_, or
to name the base _nitric radical_; but from either of these we were
dissuaded, by the following considerations. In the _first_ place, it
seemed difficult to change the name of nitre or saltpetre, which has
been universally adopted in society, in manufactures, and in chemistry;
and, on the other hand, azote having been discovered by Mr Berthollet to
be the base of volatile alkali, or ammoniac, as well as of this acid,
we thought it improper to call it nitric radical. We have therefore
continued the term of azote to the base of that part of atmospheric air
which is likewise the nitric and ammoniacal radical; and we have named
the acid of nitre, in its lower and higher degrees of oxygenation,
_nitrous acid_ in the former, and _nitric acid_ in the latter state;
thus preserving its former appellation properly modified.
Several very respectable chemists have disapproved of this deference for
the old terms, and wished us to have persevered in perfecting a new
chemical language, without paying any respect for ancient usage; so
that, by thus steering a kind of middle course, we have exposed
ourselves to the censures of one sect of chemists, and to the
expostulations of the opposite party.
The acid of nitre is susceptible of assuming a great number of separate
states, depending upon its degree of oxygenation, or upon the
proportions in which azote and oxygen enter into its composition. By a
first or lowest degree of oxygenation, it forms a particular species of
gas, which we shall continue to name _nitrous gas_; this is composed
nearly of two parts, by weight, of oxygen combined with one part of
azote; and in this state it is not miscible with water. In this gas, the
azote is by no means saturated with oxygen, but, on the contrary, has
still a very great affinity for that element, and even attracts it from
atmospheric air, immediately upon getting into contact with it. This
combination of nitrous gas with atmospheric air has even become one of
the methods for determining the quantity of oxygen contained in air, and
consequently for ascertaining its degree of salubrity.
This addition of oxygen converts the nitrous gas into a powerful acid,
which has a strong affinity with water, and which is itself susceptible
of various additional degrees of oxygenation. When the proportions of
oxygen and azote is below three parts, by weight, of the former, to one
of the latter, the acid is red coloured, and emits copious fumes. In
this state, by the application of a gentle heat, it gives out nitrous
gas; and we term it, in this degree of oxygenation, _nitrous acid_. When
four parts, by weight, of oxygen, are combined with one part of azote,
the acid is clear and colourless, more fixed in the fire than the
nitrous acid, has less odour, and its constituent elements are more
firmly united. This species of acid, in conformity with our principles
of nomenclature, is called _nitric acid_.
Thus, nitric acid is the acid of nitre, surcharged with oxygen; nitrous
acid is the acid of nitre surcharged with azote; or, what is the same
thing, with nitrous gas; and this latter is azote not sufficiently
saturated with oxygen to possess the properties of an acid. To this
degree of oxygenation, we have afterwards, in the course of this work,
given the generical name of _oxyd_[14].
FOOTNOTES:
[12] The term formerly used by the English chemists for this acid was
written _sulphureous_; but we have thought proper to spell it as above,
that it may better conform with the similar terminations of nitrous,
carbonous, &c. to be used hereafter. In general, we have used the
English terminations _ic_ and _ous_ to translate the terms of the Author
which end with _ique_ and _cux_, with hardly any other alterations.--E.
[13] For this purpose, the operation called _decrepitation_ is used,
which consists in subjecting it to nearly a red heat, in a proper
vessel, so as to evaporate all its water of crystallization.--E.
[14] In strict conformity with the principles of the new nomenclature,
but which the Author has given his reasons for deviating from in this
instance, the following ought to have been the terms for azote, in its
several degrees of oxygenation: Azote, azotic gas, (azote combined with
caloric), azotic oxyd gas, nitrous acid, and nitric acid.--E.
CHAP. VII.
_Of the Decomposition of Oxygen Gas by means of Metals, and the
Formation of Metallic Oxyds._
Oxygen has a stronger affinity with metals heated to a certain degree
than with caloric; in consequence of which, all metallic bodies,
excepting gold, silver, and platina, have the property of decomposing
oxygen gas, by attracting its base from the caloric with which it was
combined. We have already shown in what manner this decomposition takes
place, by means of mercury and iron; having observed, that, in the case
of the first, it must be considered as a kind of gradual combustion,
whilst, in the latter, the combustion is extremely rapid, and attended
with a brilliant flame. The use of the heat employed in these operations
is to separate the particles of the metal from each other, and to
diminish their attraction of cohesion or aggregation, or, what is the
same thing, their mutual attraction for each other.
The absolute weight of metallic substances is augmented in proportion to
the quantity of oxygen they absorb; they, at the same time, lose their
metallic splendour, and are reduced into an earthy pulverulent matter.
In this state metals must not be considered as entirely saturated with
oxygen, because their action upon this element is counterbalanced by the
power of affinity between it and caloric. During the calcination of
metals, the oxygen is therefore acted upon by two separate and opposite
powers, that of its attraction for caloric, and that exerted by the
metal, and only tends to unite with the latter in consequence of the
excess of the latter over the former, which is, in general, very
inconsiderable. Wherefore, when metallic substances are oxygenated in
atmospheric air, or in oxygen gas, they are not converted into acids
like sulphur, phosphorus, and charcoal, but are only changed into
intermediate substances, which, though approaching to the nature of
salts, have not acquired all the saline properties. The old chemists
have affixed the name of _calx_ not only to metals in this state, but to
every body which has been long exposed to the action of fire without
being melted. They have converted this word _calx_ into a generical
term, under which they confound calcareous earth, which, from a neutral
salt, which it really was before calcination, has been changed by fire
into an earthy alkali, by _losing_ half of its weight, with metals
which, by the same means, have joined themselves to a new substance,
whose quantity often _exceeds_ half their weight, and by which they
have been changed almost into the nature of acids. This mode of
classifying substances of so very opposite natures, under the same
generic name, would have been quite contrary to our principles of
nomenclature, especially as, by retaining the above term for this state
of metallic substances, we must have conveyed very false ideas of its
nature. We have, therefore, laid aside the expression _metallic calx_
altogether, and have substituted in its place the term _oxyd_, from the
Greek word [Greek: oxys].
By this may be seen, that the language we have adopted is both copious
and expressive. The first or lowest degree of oxygenation in bodies,
converts them into _oxyds_; a second degree of additional oxygenation
constitutes the class of acids, of which the specific names, drawn from
their particular bases, terminate in _ous_, as the _nitrous_ and
_sulphurous_ acids; the third degree of oxygenation changes these into
the species of acids distinguished by the termination in ic, as the
_nitric_ and _sulphuric_ acids; and, lastly, we can express a fourth, or
highest degree of oxygenation, by adding the word _oxygenated_ to the
name of the acid, as has been already done with the _oxygenated
muriatic_ acid.
We have not confined the term _oxyd_ to expressing the combinations of
metals with oxygen, but have extended it to signify that first degree of
oxygenation in all bodies, which, without converting them into acids,
causes them to approach to the nature of salts. Thus, we give the name
of _oxyd of sulphur_ to that soft substance into which sulphur is
converted by incipient combustion; and we call the yellow matter left by
phosphorus, after combustion, by the name of _oxyd of phosphorus_. In
the same manner, nitrous gas, which is azote in its first degree of
oxygenation, is the _oxyd of azote_. We have likewise oxyds in great
numbers from the vegetable and animal kingdoms; and I shall show, in the
sequel, that this new language throws great light upon all the
operations of art and nature.
We have already observed, that almost all the metallic oxyds have
peculiar and permanent colours. These vary not only in the different
species of metals, but even according to the various degrees of
oxygenation in the same metal. Hence we are under the necessity of
adding two epithets to each oxyd, one of which indicates the metal
_oxydated_[15], while the other indicates the peculiar colour of the
oxyd. Thus, we have the black oxyd of iron, the red oxyd of iron, and
the yellow oxyd of iron; which expressions respectively answer to the
old unmeaning terms of martial ethiops, colcothar, and rust of iron, or
ochre. We have likewise the gray, yellow, and red oxyds of lead, which
answer to the equally false or insignificant terms, ashes of lead,
massicot, and minium.
These denominations sometimes become rather long, especially when we
mean to indicate whether the metal has been oxydated in the air, by
detonation with nitre, or by means of acids; but then they always convey
just and accurate ideas of the corresponding object which we wish to
express by their use. All this will be rendered perfectly clear and
distinct by means of the tables which are added to this work.
FOOTNOTES:
[15] Here we see the word oxyd converted into the verb _to oxydate_,
_oxydated_, _oxydating_, after the same manner with the derivation of
the verb _to oxygenate_, _oxygenated_, _oxygenating_, from the word
_oxygen_. I am not clear of the absolute necessity of this second verb
here first introduced, but think, in a work of this nature, that it is
the duty of the translator to neglect every other consideration for the
sake of strict fidelity to the ideas of his author.--E.
CHAP. VIII.
_Of the Radical Principle of Water, and of its Decomposition by Charcoal
and Iron._
Until very lately, water has always been thought a simple substance,
insomuch that the older chemists considered it as an element. Such it
undoubtedly was to them, as they were unable to decompose it; or, at
least, since the decomposition which took place daily before their eyes
was entirely unnoticed. But we mean to prove, that water is by no means
a simple or elementary substance. I shall not here pretend to give the
history of this recent, and hitherto contested discovery, which is
detailed in the Memoirs of the Academy for 1781, but shall only bring
forwards the principal proofs of the decomposition and composition of
water; and, I may venture to say, that these will be convincing to such
as consider them impartially.
_Experiment First._
Having fixed the glass tube EF, (Pl. vii. fig. 11.) of from 8 to 12
lines diameter, across a furnace, with a small inclination from E to F,
lute the superior extremity E to the glass retort A, containing a
determinate quantity of distilled water, and to the inferior extremity
F, the worm SS fixed into the neck of the doubly tubulated bottle H,
which has the bent tube KK adapted to one of its openings, in such a
manner as to convey such aëriform fluids or gasses as may be disengaged,
during the experiment, into a proper apparatus for determining their
quantity and nature.
To render the success of this experiment certain, it is necessary that
the tube EF be made of well annealed and difficultly fusible glass, and
that it be coated with a lute composed of clay mixed with powdered
stone-ware; besides which, it must be supported about its middle by
means of an iron bar passed through the furnace, lest it should soften
and bend during the experiment. A tube of China-ware, or porcellain,
would answer better than one of glass for this experiment, were it not
difficult to procure one so entirely free from pores as to prevent the
passage of air or of vapours.
When things are thus arranged, a fire is lighted in the furnace EFCD,
which is supported of such a strength as to keep the tube EF red hot,
but not to make it melt; and, at the same time, such a fire is kept up
in the furnace VVXX, as to keep the water in the retort A continually
boiling.
In proportion as the water in the retort A is evaporated, it fills the
tube EF, and drives out the air it contained by the tube KK; the aqueous
gas formed by evaporation is condensed by cooling in the worm SS, and
falls, drop by drop, into the tubulated bottle H. Having continued this
operation until all the water be evaporated from the retort, and having
carefully emptied all the vessels employed, we find that a quantity of
water has passed over into the bottle H, exactly equal to what was
before contained in the retort A, without any disengagement of gas
whatsoever: So that this experiment turns out to be a simple
distillation; and the result would have been exactly the same, if the
water had been run from one vessel into the other, through the tube EF,
without having undergone the intermediate incandescence.
_Experiment Second._
The apparatus being disposed, as in the former experiment, 28 grs. of
charcoal, broken into moderately small parts, and which has previously
been exposed for a long time to a red heat in close vessels, are
introduced into the tube EF. Every thing else is managed as in the
preceding experiment.
The water contained in the retort A is distilled, as in the former
experiment, and, being condensed in the worm, falls into the bottle H;
but, at the same time, a considerable quantity of gas is disengaged,
which, escaping by the tube KK, is received in a convenient apparatus
for that purpose. After the operation is finished, we find nothing but a
few atoms of ashes remaining in the tube EF; the 28 grs. of charcoal
having entirely disappeared.
When the disengaged gasses are carefully examined, they are sound to
weigh 113.7 grs.[16]; these are of two kinds, viz. 144 cubical inches
of carbonic acid gas, weighing 100 grs. and 380 cubical inches of a
very light gas, weighing only 13.7 grs. which takes fire when in
contact with air, by the approach of a lighted body; and, when the water
which has passed over into the bottle H is carefully examined, it is
found to have lost 85.7 grs. of its weight. Thus, in this experiment,
85.7 grs. of water, joined to 28 grs. of charcoal, have combined in
such a way as to form 100 grs. of carbonic acid, and 13.7 grs. of a
particular gas capable of being burnt.
I have already shown, that 100 grs. of carbonic acid gas consists of
72 grs. of oxygen, combined with 28 grs. of charcoal; hence the 28
grs. of charcoal placed in the glass tube have acquired 72 grs. of
oxygen from the water; and it follows, that 85.7 grs. of water are
composed of 72 grs. of oxygen, combined with 13.7 grs. of a gas
susceptible of combustion. We shall see presently that this gas cannot
possibly have been disengaged from the charcoal, and must, consequently,
have been produced from the water.
I have suppressed some circumstances in the above account of this
experiment, which would only have complicated and obscured its results
in the minds of the reader. For instance, the inflammable gas dissolves
a very small part of the charcoal, by which means its weight is somewhat
augmented, and that of the carbonic gas proportionally diminished.
Altho' the alteration produced by this circumstance is very
inconsiderable; yet I have thought it necessary to determine its effects
by rigid calculation, and to report, as above, the results of the
experiment in its simplified state, as if this circumstance had not
happened. At any rate, should any doubts remain respecting the
consequences I have drawn from this experiment, they will be fully
dissipated by the following experiments, which I am going to adduce in
support of my opinion.
_Experiment Third._
The apparatus being disposed exactly as in the former experiment, with
this difference, that instead of the 28 grs. of charcoal, the tube EF
is filled with 274 grs. of soft iron in thin plates, rolled up
spirally. The tube is made red hot by means of its furnace, and the
water in the retort A is kept constantly boiling till it be all
evaporated, and has passed through the tube EF, so as to be condensed in
the bottle H.
No carbonic acid gas is disengaged in this experiment, instead of which
we obtain 416 cubical inches, or 15 grs. of inflammable gas, thirteen
times lighter than atmospheric air. By examining the water which has
been distilled, it is found to have lost 100 grs. and the 274 grs.
of iron confined in the tube are found to have acquired 85 grs.
additional weight, and its magnitude is considerably augmented. The iron
is now hardly at all attractable by the magnet; it dissolves in acids
without effervescence; and, in short, it is converted into a black oxyd,
precisely similar to that which has been burnt in oxygen gas.
In this experiment we have a true _oxydation_ of iron, by means of
water, exactly similar to that produced in air by the assistance of
heat. One hundred grains of water having been decomposed, 85 grs. of
oxygen have combined with the iron, so as to convert it into the state
of black oxyd, and 15 grs. of a peculiar inflammable gas are
disengaged: From all this it clearly follows, that water is composed of
oxygen combined with the base of an inflammable gas, in the respective
proportions of 85 parts, by weight of the former, to 15 parts of the
latter.
Thus water, besides the oxygen, which is one of its elements in common
with many other substances, contains another element as its constituent
base or radical, and for which we must find an appropriate term. None
that we could think of seemed better adapted than the word _hydrogen_,
which signifies the _generative principle of water_, from [Greek: ydor]
_aqua_, and [Greek: geinomas] _gignor_[17]. We call the combination of
this element with caloric _hydrogen gas_; and the term hydrogen
expresses the base of that gas, or the radical of water.
This experiment furnishes us with a new combustible body, or, in other
words, a body which has so much affinity with oxygen as to draw it from
its connection with caloric, and to decompose air or oxygen gas. This
combustible body has itself so great affinity with caloric, that, unless
when engaged in a combination with some other body, it always subsists
in the aëriform or gasseous state, in the usual temperature and pressure
of our atmosphere. In this state of gas it is about 1/13 of the weight
of an equal bulk of atmospheric air; it is not absorbed by water, though
it is capable of holding a small quantity of that fluid in solution, and
it is incapable of being used for respiration.
As the property this gas possesses, in common with all other combustible
bodies, is nothing more than the power of decomposing air, and carrying
off its oxygen from the caloric with which it was combined, it is easily
understood that it cannot burn, unless in contact with air or oxygen
gas. Hence, when we set fire to a bottle full of this gas, it burns
gently, first at the neck of the bottle, and then in the inside of it,
in proportion as the external air gets in: This combustion is slow and
successive, and only takes place at the surface of contact between the
two gasses. It is quite different when the two gasses are mixed before
they are set on fire: If, for instance, after having introduced one part
of oxygen gas into a narrow mouthed bottle, we fill it up with two
parts of hydrogen gas, and bring a lighted taper, or other burning body,
to the mouth of the bottle, the combustion of the two gasses takes place
instantaneously with a violent explosion. This experiment ought only to
be made in a bottle of very strong green glass, holding not more than a
pint, and wrapped round with twine, otherwise the operator will be
exposed to great danger from the rupture of the bottle, of which the
fragments will be thrown about with great force.
If all that has been related above, concerning the decomposition of
water, be exactly conformable to truth;--if, as I have endeavoured to
prove, that substance be really composed of hydrogen, as its proper
constituent element, combined with oxygen, it ought to follow, that, by
reuniting these two elements together, we should recompose water; and
that this actually happens may be judged of by the following experiment.
_Experiment Fourth._
I took a large cristal baloon, A, Pl. iv. fig. 5. holding about 30
pints, having a large opening, to which was cemented the plate of copper
BC, pierced with four holes, in which four tubes terminate. The first
tube, H h, is intended to be adapted to an air pump, by which the
baloon is to be exhausted of its air. The second tube gg, communicates,
by its extremity MM, with a reservoir of oxygen gas, with which the
baloon is to be filled. The third tube d D d', communicates, by its
extremity d NN, with a reservoir of hydrogen gas. The extremity d' of
this tube terminates in a capillary opening, through which the hydrogen
gas contained in the reservoir is forced, with a moderate degree of
quickness, by the pressure of one or two inches of water. The fourth
tube contains a metallic wire GL, having a knob at its extremity L,
intended for giving an electrical spark from L to d', on purpose to set
fire to the hydrogen gas: This wire is moveable in the tube, that we may
be able to separate the knob L from the extremity d' of the tube D d'.
The three tubes d D d', gg, and H h, are all provided with stop-cocks.
That the hydrogen gas and oxygen gas may be as much as possible deprived
of water, they are made to pass, in their way to the baloon A, through
the tubes MM, NN, of about an inch diameter, and filled with salts,
which, from their deliquescent nature, greedily attract the moisture of
the air: Such are the acetite of potash, and the muriat or nitrat of
lime[18]. These salts must only be reduced to a coarse powder, lest
they run into lumps, and prevent the gasses from geting through their
interstices.
We must be provided before hand with a sufficient quantity of oxygen
gas, carefully purified from all admixture of carbonic acid, by long
contact with a solution of potash[19].
We must likewise have a double quantity of hydrogen gas, carefully
purified in the same manner by long contact with a solution of potash in
water. The best way of obtaining this gas free from mixture is, by
decomposing water with very pure soft iron, as directed in Exp. 3. of
this chapter.
Having adjusted every thing properly, as above directed, the tube H h is
adapted to an air-pump, and the baloon A is exhausted of its air. We
next admit the oxygen gas so as to fill the baloon, and then, by means
of pressure, as is before mentioned, force a small stream of hydrogen
gas through its tube D d', which we immediately set on fire by an
electric spark. By means of the above described apparatus, we can
continue the mutual combustion of these two gasses for a long time, as
we have the power of supplying them to the baloon from their reservoirs,
in proportion as they are consumed. I have in another place[20] given a
description of the apparatus used in this experiment, and have explained
the manner of ascertaining the quantities of the gasses consumed with
the most scrupulous exactitude.
In proportion to the advancement of the combustion, there is a
deposition of water upon the inner surface of the baloon or matrass A:
The water gradually increases in quantity, and, gathering into large
drops, runs down to the bottom of the vessel. It is easy to ascertain
the quantity of water collected, by weighing the baloon both before and
after the experiment. Thus we have a twofold verification of our
experiment, by ascertaining both the quantities of the gasses employed,
and of the water formed by their combustion: These two quantities must
be equal to each other. By an operation of this kind, Mr Meusnier and I
ascertained that it required 85 parts, by weight, of oxygen, united to
15 parts of hydrogen, to compose 100 parts of water. This experiment,
which has not hitherto been published, was made in presence of a
numerous committee from the Royal Academy. We exerted the most
scrupulous attention to its accuracy; and have reason to believe that
the above propositions cannot vary a two hundredth part from absolute
truth.
From these experiments, both analytical and synthetic, we may now affirm
that we have ascertained, with as much certainty as is possible in
physical or chemical subjects, that water is not a simple elementary
substance, but is composed of two elements, oxygen and hydrogen; which
elements, when existing separately, have so strong affinity for caloric,
as only to subsist under the form of gas in the common temperature and
pressure of our atmosphere.
This decomposition and recomposition of water is perpetually operating
before our eyes, in the temperature of the atmosphere, by means of
compound elective attraction. We shall presently see that the phenomena
attendant upon vinous fermentation, putrefaction, and even vegetation,
are produced, at least in a certain degree, by decomposition of water.
It is very extraordinary that this fact should have hitherto been
overlooked by natural philosophers and chemists: Indeed, it strongly
proves, that, in chemistry, as in moral philosophy, it is extremely
difficult to overcome prejudices imbibed in early education, and to
search for truth in any other road than the one we have been accustomed
to follow.
I shall finish this chapter by an experiment much less demonstrative
than those already related, but which has appeared to make more
impression than any other upon the minds of many people. When 16 ounces
of alkohol are burnt in an apparatus[21] properly adapted for collecting
all the water disengaged during the combustion, we obtain from 17 to 18
ounces of water. As no substance can furnish a product larger than its
original bulk, it follows, that something else has united with the
alkohol during its combustion; and I have already shown that this must
be oxygen, or the base of air. Thus alkohol contains hydrogen, which is
one of the elements of water; and the atmospheric air contains oxygen,
which is the other element necessary to the composition of water. This
experiment is a new proof that water is a compound substance.
FOOTNOTES:
[16] In the latter part of this work will be found a particular account
of the processes necessary for separating the different kinds of gasses,
and for determining their quantities.--A.
[17] This expression Hydrogen has been very severely criticised by some,
who pretend that it signifies engendered by water, and not that which
engenders water. The experiments related in this chapter prove, that,
when water is decomposed, hydrogen is produced, and that, when hydrogen
is combined with oxygen, water is produced: So that we may say, with
equal truth, that water is produced from hydrogen, or hydrogen is
produced from water.--A.
[18] See the nature of these salts in the second part of this book.--A.
[19] By potash is here meant, pure or caustic alkali, deprived of
carbonic acid by means of quick-lime: In general, we may observe here,
that all the alkalies and earths must invariably be considered as in
their pure or caustic state, unless otherwise expressed.--E. The method
of obtaining this pure alkali of potash will be given in the sequel.--A.
[20] See the third part of this work.--A.
[21] See an account of this apparatus in the third part of this
work.--A.
CHAP. IX.
_Of the quantities of Caloric disengaged from different species of
Combustion._
We have already mentioned, that, when any body is burnt in the center of
a hollow sphere of ice and supplied with air at the temperature of zero
(32°), the quantity of ice melted from the inside of the sphere becomes
a measure of the relative quantities of caloric disengaged. Mr de la
Place and I gave a description of the apparatus employed for this kind
of experiment in the Memoirs of the Academy for 1780, p. 355; and a
description and plate of the same apparatus will be found in the third
part of this work. With this apparatus, phosphorus, charcoal, and
hydrogen gas, gave the following results:
One pound of phosphorus melted 100 libs. of ice.
One pound of charcoal melted 96 libs. 8 oz.
One pound of hydrogen gas melted 295 libs. 9 oz. 3-1/2 gros.
As a concrete acid is formed by the combustion of phosphorus, it is
probable that very little caloric remains in the acid, and,
consequently, that the above experiment gives us very nearly the whole
quantity of caloric contained in the oxygen gas. Even if we suppose the
phosphoric acid to contain a good deal of caloric, yet, as the
phosphorus must have contained nearly an equal quantity before
combustion, the error must be very small, as it will only consist of the
difference between what was contained in the phosphorus before, and in
the phosphoric acid after combustion.
I have already shown in Chap. V. that one pound of phosphorus absorbs
one pound eight ounces of oxygen during combustion; and since, by the
same operation, 100 lib. of ice are melted, it follows, that the
quantity of caloric contained in one pound of oxygen gas is capable of
melting 66 libs. 10 oz. 5 gros 24 grs. of ice.
One pound of charcoal during combustion melts only 96 libs. 8 oz. of
ice, whilst it absorbs 2 libs. 9 oz. 1 gros 10 grs. of oxygen.
By the experiment with phosphorus, this quantity of oxygen gas ought to
disengage a quantity of caloric sufficient to melt 171 libs. 6 oz. 5
gros of ice; consequently, during this experiment, a quantity of
caloric, sufficient to melt 74 libs. 14 oz. 5 gros of ice
disappears. Carbonic acid is not, like phosphoric acid, in a concrete
state after combustion but in the state of gas, and requires to be
united with caloric to enable it to subsist in that state; the quantity
of caloric missing in the last experiment is evidently employed for that
purpose. When we divide that quantity by the weight of carbonic acid,
formed by the combustion of one pound of charcoal, we find that the
quantity of caloric necessary for changing one pound of carbonic acid
from the concrete to the gasseous state, would be capable of melting 20
libs. 15 oz. 5 gros of ice.
We may make a similar calculation with the combustion of hydrogen gas
and the consequent formation of water. During the combustion of one
pound of hydrogen gas, 5 libs. 10 oz. 5 gros 24 grs. of oxygen
gas are absorbed, and 295 libs. 9 oz. 3-1/2 gros of ice are
melted. But 5 libs. 10 oz. 5 gros 24 grs. of oxygen gas, in
changing from the aëriform to the solid state, loses, according to the
experiment with phosphorus, enough of caloric to have melted 377 libs.
12 oz. 3 gros of ice. There is only disengaged, from the same
quantity of oxygen, during its combustion with hydrogen gas, as much
caloric as melts 295 libs. 2 oz. 3-1/2 gros; wherefore there
remains in the water at Zero (32°), formed, during this experiment, as
much caloric as would melt 82 libs. 9 oz. 7-1/2 gros of ice.
Hence, as 6 libs. 10 oz. 5 gros 24 grs. of water are formed from
the combustion of one pound of hydrogen gas with 5 libs. 10 oz. 5
gros 24 grs. of oxygen, it follows that, in each pound of water, at
the temperature of Zero, (32°), there exists as much caloric as would
melt 12 libs. 5 oz. 2 gros 48 grs. of ice, without taking into
account the quantity originally contained in the hydrogen gas, which we
have been obliged to omit, for want of data to calculate its quantity.
From this it appears that water, even in the state of ice, contains a
considerable quantity of caloric, and that oxygen, in entering into that
combination, retains likewise a good proportion.
From these experiments, we may assume the following results as
sufficiently established.
_Combustion of Phosphorus._
From the combustion of phosphorus, as related in the foregoing
experiments, it appears, that one pound of phosphorus requires 1 lib.
8 oz. of oxygen gas for its combustion, and that 2 libs. 8 oz. of
concrete phosphoric acid are produced.
The quantity of caloric disengaged by the
combustion of one pound of phosphorus, expressed
by the number of pounds of ice melted
during that operation, is 100.00000.
The quantity disengaged from each pound of
oxygen, during the combustion of phosphorus,
expressed in the same manner, is 66.66667.
The quantity disengaged during the formation
of one pound of phosphoric acid, 40.00000.
The quantity remaining in each pound of phosphoric
acid, 0.00000(A).
[Note A: We here suppose the phosphoric acid not to contain any caloric,
which is not strictly true; but, as I have before observed, the quantity
it really contains is probably very small, and we have not given it a
value, for want of a sufficient data to go upon.--A.]
_Combustion of Charcoal._
In the combustion of one pound of charcoal, 2 libs. 9 oz. 1 gros
10 grs. of oxygen gas are absorbed, and 3 libs. 9 oz. 1 gros 10
grs. of carbonic acid gas are formed.
Caloric, disengaged daring the combustion
of one pound of charcoal, 96.50000(A).
Caloric disengaged during the combustion of
charcoal, from each pound of oxygen gas
absorbed, 37.52823.
Caloric disengaged during the formation of
one pound of carbonic acid gas, 27.02024.
Caloric retained by each pound of oxygen
after the combustion, 29.13844.
Caloric necessary for supporting one pound
of carbonic acid in the state of gas, 20.97960.
[Note A: All these relative quantities of caloric are expressed by the
number of pounds of ice, and decimal parts, melted during the several
operations.--E.]
_Combustion of Hydrogen Gas._
In the combustion of one pound of hydrogen gas, 5 libs. 10 oz. 5
gros 24 grs. of oxygen gas are absorbed, and 6 libs. 10 oz. 5
gros 24 grs. of water are formed.
Caloric from each lib. of hydrogen gas, 295.58950.
Caloric from each lib. of oxygen gas, 52.16280.
Caloric disengaged during the formation of each pound of water, 44.33840.
Caloric retained by each lib. of oxygen after
combustion with hydrogen, 14.50386.
Caloric retained by each lib. of water at
the temperature of Zero (32°), 12.32823.
_Of the Formation of Nitric Acid._
When we combine nitrous gas with oxygen gas, so as to form nitric or
nitrous acid a degree of heat is produced, which is much less
considerable than what is evolved during the other combinations of
oxygen; whence it follows that oxygen, when it becomes fixed in nitric
acid, retains a great part of the heat which it possessed in the state
of gas. It is certainly possible to determine the quantity of caloric
which is disengaged during the combination of these two gasses, and
consequently to determine what quantity remains after the combination
takes place. The first of these quantities might be ascertained, by
making the combination of the two gasses in an apparatus surrounded by
ice; but, as the quantity of caloric disengaged is very inconsiderable,
it would be necessary to operate upon a large quantity of the two gasses
in a very troublesome and complicated apparatus. By this consideration,
Mr de la Place and I have hitherto been prevented from making the
attempt. In the mean time, the place of such an experiment may be
supplied by calculations, the results of which cannot be very far from
truth.
Mr de la Place and I deflagrated a convenient quantity of nitre and
charcoal in an ice apparatus, and found that twelve pounds of ice were
melted by the deflagration of one pound of nitre. We shall see, in the
sequel, that one pound of nitre is composed, as under, of
Potash 7 oz. 6 gros 51.84 grs. = 4515.84 grs.
Dry acid 8 1 21.16 = 4700.16.
The above quantity of dry acid is composed of
Oxygen 6 oz. 3 gros 66.34 grs. = 3738.34 grs.
Azote 1 5 25.82 = 961.82.
By this we find that, during the above deflagration, 2 gros 1-1/3
gr. of charcoal have suffered combustion, alongst with 3738.34 grs.
or 6 oz. 3 gros 66.34 grs. of oxygen. Hence, since 12 libs. of
ice were melted during the combustion, it follows, that one pound of
oxygen burnt in the same manner would have melted 29.58320 libs. of
ice. To which the quantity of caloric, retained by a pound of oxygen
after combining with charcoal to form carbonic acid gas, being added,
which was already ascertained to be capable of melting 29.13844 libs.
of ice, we have for the total quantity of caloric remaining in a pound
of oxygen, when combined with nitrous gas in the nitric acid 58.72164;
which is the number of pounds of ice the caloric remaining in the oxygen
in that state is capable of melting.
We have before seen that, in the state of oxygen gas, it contained at
least 66.66667; wherefore it follows that, in combining with azote to
form nitric acid, it only loses 7.94502. Farther experiments upon this
subject are necessary to ascertain how far the results of this
calculation may agree with direct fact. This enormous quantity of
caloric retained by oxygen in its combination into nitric acid, explains
the cause of the great disengagement of caloric during the
deflagrations of nitre; or, more strictly speaking, upon all occasions
of the decomposition of nitric acid.
_Of the Combustion of Wax._
Having examined several cases of simple combustion, I mean now to give a
few examples of a more complex nature. One pound of wax-taper being
allowed to burn slowly in an ice apparatus, melted 133 libs. 2 oz.
5-1/3 gros of ice. According to my experiments in the Memoirs of the
Academy for 1784, p. 606, one pound of wax-taper consists of 13 oz. 1
gros 23 grs. of charcoal, and 2 oz. 6 gros 49 grs. of
hydrogen.
By the foregoing experiments, the above
quantity of charcoal ought to melt 79.39390 libs. of ice;
and the hydrogen should melt 52.37605
---------
In all 131.76995 libs.
Thus, we see the quantity of caloric disengaged from a burning taper, is
pretty exactly conformable to what was obtained by burning separately a
quantity of charcoal and hydrogen equal to what enters into its
composition. These experiments with the taper were several times
repeated, so that I have reason to believe them accurate.
_Combustion of Olive Oil._
We included a burning lamp, containing a determinate quantity of
olive-oil, in the ordinary apparatus, and, when the experiment was
finished, we ascertained exactly the quantities of oil consumed, and of
ice melted; the result was, that, during the combustion of one pound of
olive-oil, 148 libs. 14 oz. 1 gros of ice were melted. By my
experiments in the Memoirs of the Academy for 1784, and of which the
following Chapter contains an abstract, it appears that one pound of
olive-oil consists of 12 oz. 5 gros 5 grs. of charcoal, and 3
oz. 2 gros 67 grs. of hydrogen. By the foregoing experiments, that
quantity of charcoal should melt 76.18723 libs. of ice, and the
quantity of hydrogen in a pound of the oil should melt 62.15053 libs.
The sum of these two gives 138.33776 libs. of ice, which the two
constituent elements of the oil would have melted, had they separately
suffered combustion, whereas the oil really melted 148.88330 libs.
which gives an excess of 10.54554 in the result of the experiment above
the calculated result, from data furnished by former experiments.
This difference, which is by no means very considerable, may arise from
errors which are unavoidable in experiments of this nature, or it may be
owing to the composition of oil not being as yet exactly ascertained. It
proves, however, that there is a great agreement between the results of
our experiments, respecting the combination of caloric, and those which
regard its disengagement.
The following desiderata still remain to be determined, viz. What
quantity of caloric is retained by oxygen, after combining with metals,
so as to convert them into oxyds; What quantity is contained by
hydrogen, in its different states of existence; and to ascertain, with
more precision than is hitherto attained, how much caloric is disengaged
during the formation of water, as there still remain considerable doubts
with respect to our present determination of this point, which can only
be removed by farther experiments. We are at present occupied with this
inquiry; and, when once these several points are well ascertained, which
we hope they will soon be, we shall probably be under the necessity of
making considerable corrections upon most of the results of the
experiments and calculations in this Chapter. I did not, however,
consider this as a sufficient reason for withholding so much as is
already known from such as may be inclined to labour upon the same
subject. It is difficult, in our endeavours to discover the principles
of a new science, to avoid beginning by guess-work; and it is rarely
possible to arrive at perfection from the first setting out.
CHAP. X.
_Of the Combination of Combustible Substances with each other._
As combustible substances in general have a great affinity for oxygen,
they ought likewise to attract, or tend to combine with each other;
_quae sunt eadem uni tertio, sunt eadem inter se_; and the axiom is
found to be true. Almost all the metals, for instance, are capable of
uniting with each other, and forming what are called _alloys_[22], in
common language. Most of these, like all combinations, are susceptible
of several degrees of saturation; the greater number of these alloys are
more brittle than the pure metals of which they are composed, especially
when the metals alloyed together are considerably different in their
degrees of fusibility. To this difference in fusibility, part of the
phenomena attendant upon _alloyage_ are owing, particularly the property
of iron, called by workmen _hotshort_. This kind of iron must be
considered as an alloy, or mixture of pure iron, which is almost
infusible, with a small portion of some other metal which fuses in a
much lower degree of heat. So long as this alloy remains cold, and both
metals are in the solid state, the mixture is malleable; but, if heated
to a sufficient degree to liquify the more fusible metal, the particles
of the liquid metal, which are interposed between the particles of the
metal remaining solid, must destroy their continuity, and occasion the
alloy to become brittle. The alloys of mercury, with the other metals,
have usually been called _amalgams_, and we see no inconvenience from
continuing the use of that term.
Sulphur, phosphorus, and charcoal, readily unite with metals.
Combinations of sulphur with metals are usually named _pyrites_. Their
combinations with phosphorus and charcoal are either not yet named, or
have received new names only of late; so that we have not scrupled to
change them according to our principles. The combinations of metal and
sulphur we call _sulphurets_, those with phosphorus _phosphurets_, and
those formed with charcoal _carburets_. These denominations are extended
to all the combinations into which the above three substances enter,
without being previously oxygenated. Thus, the combination of sulphur
with potash, or fixed vegetable alkali, is called _sulphuret of potash_;
that which it forms with ammoniac, or volatile alkali, is termed
_sulphuret of ammoniac_.
Hydrogen is likewise capable of combining with many combustible
substances. In the state of gas, it dissolves charcoal, sulphur,
phosphorus, and several metals; we distinguish these combinations by the
terms, _carbonated hydrogen gas_, _sulphurated hydrogen gas_, and
_phosphorated hydrogen gas_. The sulphurated hydrogen gas was called
_hepatic air_ by former chemists, or _foetid air from sulphur_, by Mr
Scheele. The virtues of several mineral waters, and the foetid smell of
animal excrements, chiefly arise from the presence of this gas. The
phosphorated hydrogen gas is remarkable for the property, discovered by
Mr Gengembre, of taking fire spontaneously upon getting into contact
with atmospheric air, or, what is better, with oxygen gas. This gas has
a strong flavour, resembling that of putrid fish; and it is very
probable that the phosphorescent quality of fish, in the state of
putrefaction, arises from the escape of this species of gas. When
hydrogen and charcoal are combined together, without the intervention of
caloric, to bring the hydrogen into the state of gas, they form oil,
which is either fixed or volatile, according to the proportions of
hydrogen and charcoal in its composition. The chief difference between
fixed or fat oils drawn from vegetables by expression, and volatile or
essential oils, is, that the former contains an excess of charcoal,
which is separated when the oils are heated above the degree of boiling
water; whereas the volatile oils, containing a just proportion of these
two constituent ingredients, are not liable to be decomposed by that
heat, but, uniting with caloric into the gasseous state, pass over in
distillation unchanged.
In the Memoirs of the Academy for 1784, p. 593. I gave an account of my
experiments upon the composition of oil and alkohol, by the union of
hydrogen with charcoal, and of their combination with oxygen. By these
experiments, it appears that fixed oils combine with oxygen during
combustion, and are thereby converted into water and carbonic acid. By
means of calculation applied to the products of these experiments, we
find that fixed oil is composed of 21 parts, by weight, of hydrogen
combined with 79 parts of charcoal. Perhaps the solid substances of an
oily nature, such as wax, contain a proportion of oxygen, to which they
owe their state of solidity. I am at present engaged in a series of
experiments, which I hope will throw great light upon this subject.
It is worthy of being examined, whether hydrogen in its concrete state,
uncombined with caloric, be susceptible of combination with sulphur,
phosphorus, and the metals. There is nothing that we know of, which, _a
priori_, should render these combinations impossible; for combustible
bodies being in general susceptible of combination with each other,
there is no evident reason for hydrogen being an exception to the rule:
However, no direct experiment as yet establishes either the possibility
or impossibility of this union. Iron and zinc are the most likely, of
all the metals, for entering into combination with hydrogen; but, as
these have the property of decomposing water, and as it is very
difficult to get entirely free from moisture in chemical experiments, it
is hardly possible to determine whether the small portions of hydrogen
gas, obtained in certain experiments with these metals, were previously
combined with the metal in the state of solid hydrogen, or if they were
produced by the decomposition of a minute quantity of water. The more
care we take to prevent the presence of water in these experiments, the
less is the quantity of hydrogen gas procured; and, when very accurate
precautions are employed, even that quantity becomes hardly sensible.
However this inquiry may turn out respecting the power of combustible
bodies, as sulphur, phosphorus, and metals, to absorb hydrogen, we are
certain that they only absorb a very small portion; and that this
combination, instead of being essential to their constitution, can only
be considered as a foreign substance, which contaminates their purity.
It is the province of the advocates[23] for this system to prove, by
decisive experiments, the real existence of this combined hydrogen,
which they have hitherto only done by conjectures founded upon
suppositions.
FOOTNOTES:
[22] This term _alloy_, which we have from the language of the arts,
serves exceedingly well for distinguishing all the combinations or
intimate unions of metals with each other, and is adopted in our new
nomenclature for that purpose.--A.
[23] By these are meant the supporters of the phlogistic theory, who at
present consider hydrogen, or the base of inflammable air, as the
phlogiston of the celebrated Stahl.--E.
CHAP. XI.
_Observations upon Oxyds and Acids with several Bases--and upon the
Composition of Animal and Vegetable Substances._
We have, in Chap. V. and VIII. examined the products resulting from the
combustion of the four simple combustible substances, sulphur,
phosphorus, charcoal, and hydrogen: We have shown, in Chap. X that the
simple combustible substances are capable of combining with each other
into compound combustible substances, and have observed that oils in
general, and particularly the fixed vegetable oils, belong to this
class, being composed of hydrogen and charcoal. It remains, in this
chapter, to treat of the oxygenation of these compound combustible
substances, and to show that there exist acids and oxyds having double
and triple bases. Nature furnishes us with numerous examples of this
kind of combinations, by means of which, chiefly, she is enabled to
produce a vast variety of compounds from a very limited number of
elements, or simple substances.
It was long ago well known, that, when muriatic and nitric acids were
mixed together, a compound acid was formed, having properties quite
distinct from those of either of the acids taken separately. This acid
was called _aqua regia_, from its most celebrated property of dissolving
gold, called _king of metals_ by the alchymists. Mr Berthollet has
distinctly proved that the peculiar properties of this acid arise from
the combined action of its two acidifiable bases; and for this reason we
have judged it necessary to distinguish it by an appropriate name: That
of _nitro-muriatic_ acid appears extremely applicable, from its
expressing the nature of the two substances which enter into its
composition.
This phenomenon of a double base in one acid, which had formerly been
observed only in the nitro-muriatic acid, occurs continually in the
vegetable kingdom, in which a simple acid, or one possessed of a single
acidifiable base, is very rarely found. Almost all the acids procurable
from this kingdom have bases composed of charcoal and hydrogen, or of
charcoal, hydrogen, and phosphorus, combined with more or less oxygen.
All these bases, whether double or triple, are likewise formed into
oxyds, having less oxygen than is necessary to give them the properties
of acids. The acids and oxyds from the animal kingdom are still more
compound, as their bases generally consist of a combination of
charcoal, phosphorus, hydrogen, and azote.
As it is but of late that I have acquired any clear and distinct notions
of these substances, I shall not, in this place, enlarge much upon the
subject, which I mean to treat of very fully in some memoirs I am
preparing to lay before the Academy. Most of my experiments are already
performed; but, to be able to give exact reports of the resulting
quantities, it is necessary that they be carefully repeated, and
increased in number: Wherefore, I shall only give a short enumeration of
the vegetable and animal acids and oxyds, and terminate this article by
a few reflections upon the composition of vegetable and animal bodies.
Sugar, mucus, under which term we include the different kinds of gums,
and starch, are vegetable oxyds, having hydrogen and charcoal combined,
in different proportions, as their radicals or bases, and united with
oxygen, so as to bring them to the state of oxyds. From the state of
oxyds they are capable of being changed into acids by the addition of a
fresh quantity of oxygen; and, according to the degrees of oxygenation,
and the proportion of hydrogen and charcoal in their bases, they form
the several kinds of vegetable acids.
It would be easy to apply the principles of our nomenclature to give
names to these vegetable acids and oxyds, by using the names of the two
substances which compose their bases: They would thus become
hydro-carbonous acids and oxyds: In this method we might indicate which
of their elements existed in excess, without circumlocution, after the
manner used by Mr Rouelle for naming vegetable extracts: He calls these
extracto-resinous when the extractive matter prevails in their
composition, and resino-extractive when they contain a larger proportion
of resinous matter. Upon that plan, and by varying the terminations
according to the formerly established rules of our nomenclature, we have
the following denominations: Hydro-carbonous, hydro-carbonic;
carbono-hydrous, and carbono-hydric oxyds. And for the acids:
Hydro-carbonous, hydro carbonic, oxygenated hydro-carbonic;
carbono-hydrous, carbono-hydric, and oxygenated carbono-hydric. It is
probable that the above terms would suffice for indicating all the
varieties in nature, and that, in proportion as the vegetable acids
become well understood, they will naturally arrange themselves under
these denominations. But, though we know the elements of which these are
composed, we are as yet ignorant of the proportions of these
ingredients, and are still far from being able to class them in the
above methodical manner; wherefore, we have determined to retain the
ancient names provisionally. I am somewhat farther advanced in this
inquiry than at the time of publishing our conjunct essay upon chemical
nomenclature; yet it would be improper to draw decided consequences from
experiments not yet sufficiently precise: Though I acknowledge that this
part of chemistry still remains in some degree obscure, I must express
my expectations of its being very soon elucidated.
I am still more forcibly necessitated to follow the same plan in naming
the acids, which have three or four elements combined in their bases; of
these we have a considerable number from the animal kingdom, and some
even from vegetable substances. Azote, for instance, joined to hydrogen
and charcoal, form the base or radical of the Prussic acid; we have
reason to believe that the same happens with the base of the Gallic
acid; and almost all the animal acids have their bases composed of
azote, phosphorus, hydrogen, and charcoal. Were we to endeavour to
express at once all these four component parts of the bases, our
nomenclature would undoubtedly be methodical; it would have the property
of being clear and determinate; but this assemblage of Greek and Latin
substantives and adjectives, which are not yet universally admitted by
chemists, would have the appearance of a barbarous language, difficult
both to pronounce and to be remembered. Besides, this part of chemistry
being still far from that accuracy it must arrive to, the perfection of
the science ought certainly to precede that of its language; and we must
still, for some time, retain the old names for the animal oxyds and
acids. We have only ventured to make a few slight modifications of these
names, by changing the termination into _ous_, when we have reason to
suppose the base to be in excess, and into _ic_, when we suspect the
oxygen predominates.
The following are all the vegetable acids hitherto known:
1. Acetous acid.
2. Acetic acid.
3. Oxalic acid.
4. Tartarous acid.
5. Pyro-tartarous acid.
6. Citric acid.
7. Malic acid.
8. Pyro-mucous acid.
9. Pyro-lignous acid.
10. Gallic acid.
11. Benzoic acid.
12. Camphoric acid.
13. Succinic acid.
Though all these acids, as has been already said, are chiefly, and
almost entirely, composed of hydrogen, charcoal, and oxygen, yet,
properly speaking, they contain neither water carbonic acid nor oil, but
only the elements necessary for forming these substances. The power of
affinity reciprocally exerted by the hydrogen, charcoal, and oxygen, in
these acids, is in a state of equilibrium only capable of existing in
the ordinary temperature of the atmosphere; for, when they are heated
but a very little above the temperature of boiling water, this
equilibrium is destroyed, part of the oxygen and hydrogen unite, and
form water; part of the charcoal and hydrogen combine into oil; part of
the charcoal and oxygen unite to form carbonic acid; and, lastly, there
generally remains a small portion of charcoal, which, being in excess
with respect to the other ingredients, is left free. I mean to explain
this subject somewhat farther in the succeeding chapter.
The oxyds of the animal kingdom are hitherto less known than those from
the vegetable kingdom, and their number is as yet not at all determined.
The red part of the blood, lymph, and most of the secretions, are true
oxyds, under which point of view it is very important to consider them.
We are only acquainted with six animal acids, several of which, it is
probable, approach very near each other in their nature, or, at least,
differ only in a scarcely sensible degree. I do not include the
phosphoric acid amongst these, because it is found in all the kingdoms
of nature. They are,
1. Lactic acid.
2. Saccholactic acid.
3. Bombic acid.
4. Formic acid.
5. Sebacic acid.
6. Prussic acid.
The connection between the constituent elements of the animal oxyds and
acids is not more permanent than in those from the vegetable kingdom, as
a small increase of temperature is sufficient to overturn it. I hope to
render this subject more distinct than has been done hitherto in the
following chapter.
CHAP. XII.
_Of the Decomposition of Vegetable and Animal Substances by the Action
of Fire._
Before we can thoroughly comprehend what takes place during the
decomposition of vegetable substances by fire, we must take into
consideration the nature of the elements which enter into their
composition, and the different affinities which the particles of these
elements exert upon each other, and the affinity which caloric possesses
with them. The true constituent elements of vegetables are hydrogen,
oxygen, and charcoal: These are common to all vegetables, and no
vegetable can exist without them: Such other substances as exist in
particular vegetables are only essential to the composition of those in
which they are found, and do not belong to vegetables in general.
Of these elements, hydrogen and oxygen have a strong tendency to unite
with caloric, and be converted into gas, whilst charcoal is a fixed
element, having but little affinity with caloric. On the other hand,
oxygen, which, in the usual temperature, tends nearly equally to unite
with hydrogen and with charcoal, has a much stronger affinity with
charcoal when at the red heat[24], and then unites with it to form
carbonic acid.
Although we are far from being able to appreciate all these powers of
affinity, or to express their proportional energy by numbers, we are
certain, that, however variable they may be when considered in relation
to the quantity of caloric with which they are combined, they are all
nearly in equilibrium in the usual temperature of the atmosphere; hence
vegetables neither contain oil[25], water, nor carbonic acid, tho' they
contain all the elements of these substances. The hydrogen is neither
combined with the oxygen nor with the charcoal, and reciprocally; the
particles of these three substances form a triple combination, which
remains in equilibrium whilst undisturbed by caloric but a very slight
increase of temperature is sufficient to overturn this structure of
combination.
If the increased temperature to which the vegetable is exposed does not
exceed the heat of boiling water, one part of the hydrogen combines with
the oxygen, and forms water, the rest of the hydrogen combines with a
part of the charcoal, and forms volatile oil, whilst the remainder of
the charcoal, being set free from its combination with the other
elements, remains fixed in the bottom of the distilling vessel.
When, on the contrary, we employ a red heat, no water is formed, or, at
least, any that may have been produced by the first application of the
heat is decomposed, the oxygen having a greater affinity with the
charcoal at this degree of heat, combines with it to form carbonic acid,
and the hydrogen being left free from combination with the other
elements, unites with caloric, and escapes in the state of hydrogen gas.
In this high temperature, either no oil is formed, or, if any was
produced during the lower temperature at the beginning of the
experiment, it is decomposed by the action of the red heat. Thus the
decomposition of vegetable matter, under a high temperature, is produced
by the action of double and triple affinities; while the charcoal
attracts the oxygen, on purpose to form carbonic acid, the caloric
attracts the hydrogen, and converts it into hydrogen gas.
The distillation of every species of vegetable substance confirms the
truth of this theory, if we can give that name to a simple relation of
facts. When sugar is submitted to distillation, so long as we only
employ a heat but a little below that of boiling water, it only loses
its water of cristallization, it still remains sugar, and retains all
its properties; but, immediately upon raising the heat only a little
above that degree, it becomes blackened, a part of the charcoal
separates from the combination, water slightly acidulated passes over
accompanied by a little oil, and the charcoal which remains in the
retort is nearly a third part of the original weight of the sugar.
The operation of affinities which take place during the decomposition,
by fire, of vegetables which contain azote, such as the cruciferous
plants, and of those containing phosphorus, is more complicated; but, as
these substances only enter into the composition of vegetables in very
small quantities, they only, apparently, produce slight changes upon the
products of distillation; the phosphorus seems to combine with the
charcoal, and, acquiring fixity from that union, remains behind in the
retort, while the azote, combining with a part of the hydrogen, forms
ammoniac, or volatile alkali.
Animal substances, being composed nearly of the same elements with
cruciferous plants, give the same products in distillation, with this
difference, that, as they contain a greater quantity of hydrogen and
azote, they produce more oil and more ammoniac. I shall only produce one
fact as a proof of the exactness with which this theory explains all the
phenomena which occur during the distillation of animal substances,
which is the rectification and total decomposition of volatile animal
oil, commonly known by the name of Dippel's oil. When these oils are
procured by a first distillation in a naked fire they are brown, from
containing a little charcoal almost in a free state; but they become
quite colourless by rectification. Even in this state the charcoal in
their composition has so slight a connection with the other elements as
to separate by mere exposure to the air. If we put a quantity of this
animal oil, well rectified, and consequently clear, limpid, and
transparent, into a bell-glass filled with oxygen gas over mercury, in a
short time the gas is much diminished, being absorbed by the oil, the
oxygen combining with the hydrogen of the oil forms water, which sinks
to the bottom, at the same time the charcoal which was combined with the
hydrogen being set free, manifests itself by rendering the oil black.
Hence the only way of preserving these oils colourless and transparent,
is by keeping them in bottles perfectly full and accurately corked, to
hinder the contact of air, which always discolours them.
Successive rectifications of this oil furnish another phenomenon
confirming our theory. In each distillation a small quantity of charcoal
remains in the retort, and a little water is formed by the union of the
oxygen contained in the air of the distilling vessels with the hydrogen
of the oil. As this takes place in each successive distillation, if we
make use of large vessels and a considerable degree of heat, we at last
decompose the whole of the oil, and change it entirely into water and
charcoal. When we use small vessels, and especially when we employ a
slow fire, or degree of heat little above that of boiling water, the
total decomposition of these oils, by repeated distillation, is greatly
more tedious, and more difficultly accomplished. I shall give a
particular detail to the Academy, in a separate memoir, of all my
experiments upon the decomposition of oil; but what I have related above
may suffice to give just ideas of the composition of animal and
vegetable substances, and of their decomposition by the action of fire.
FOOTNOTES:
[24] Though this term, red heat, does not indicate any absolutely
determinate degree of temperature, I shall use it sometimes to express a
temperature considerably above that of boiling water.--A.
[25] I must be understood here to speak of vegetables reduced to a
perfectly dry state; and, with respect to oil, I do not mean that which
is procured by expression either in the cold, or in a temperature not
exceeding that of boiling water; I only allude to the empyreumatic oil
procured by distillation with a naked fire, in a heat superior to the
temperature of boiling water; which is the only oil declared to be
produced by the operation of fire. What I have published upon this
subject in the Memoirs of the Academy for 1786 may be consulted.--A.
CHAP. XIII.
_Of the Decomposition of Vegetable Oxyds by the Vinous Fermentation._
The manner in which wine, cyder, mead, and all the liquors formed by the
spiritous fermentation, are produced, is well known to every one. The
juice of grapes or of apples being expressed, and the latter being
diluted with water, they are put into large vats, which are kept in a
temperature of at least 10° (54.5°) of the thermometer. A rapid
intestine motion, or fermentation, very soon takes place, numerous
globules of gas form in the liquid and burst at the surface; when the
fermentation is at its height, the quantity of gas disengaged is so
great as to make the liquor appear as if boiling violently over a fire.
When this gas is carefully gathered, it is found to be carbonic acid
perfectly pure, and free from admixture with any other species of air or
gas whatever.
When the fermentation is completed, the juice of grapes is changed from
being sweet, and full of sugar, into a vinous liquor which no longer
contains any sugar, and from which we procure, by distillation, an
inflammable liquor, known in commerce under the name of Spirit of Wine.
As this liquor is produced by the fermentation of any saccharine matter
whatever diluted with water, it must have been contrary to the
principles of our nomenclature to call it spirit of wine rather than
spirit of cyder, or of fermented sugar; wherefore, we have adopted a
more general term, and the Arabic word _alkohol_ seems extremely proper
for the purpose.
This operation is one of the most extraordinary in chemistry: We must
examine whence proceed the disengaged carbonic acid and the inflammable
liquor produced, and in what manner a sweet vegetable oxyd becomes thus
converted into two such opposite substances, whereof one is combustible,
and the other eminently the contrary. To solve these two questions, it
is necessary to be previously acquainted with the analysis of the
fermentable substance, and of the products of the fermentation. We may
lay it down as an incontestible axiom, that, in all the operations of
art and nature, nothing is created; an equal quantity of matter exists
both before and after the experiment; the quality and quantity of the
elements remain precisely the same; and nothing takes place beyond
changes and modifications in the combination of these elements. Upon
this principle the whole art of performing chemical experiments
depends: We must always suppose an exact equality between the elements
of the body examined and those of the products of its analysis.
Hence, since from must of grapes we procure alkohol and carbonic acid, I
have an undoubted right to suppose that must consists of carbonic acid
and alkohol. From these premises, we have two methods of ascertaining
what passes during vinous fermentation, by determining the nature of,
and the elements which compose, the fermentable substances, or by
accurately examining the produces resulting from fermentation; and it is
evident that the knowledge of either of these must lead to accurate
conclusions concerning the nature and composition of the other. From
these considerations, it became necessary accurately to determine the
constituent elements of the fermentable substances; and, for this
purpose, I did not make use of the compound juices of fruits, the
rigorous analysis of which is perhaps impossible, but made choice of
sugar, which is easily analysed, and the nature of which I have already
explained. This substance is a true vegetable oxyd with two bases,
composed of hydrogen and charcoal brought to the state of an oxyd, by a
certain proportion of oxygen; and these three elements are combined in
such a way, that a very slight force is sufficient to destroy the
equilibrium of their connection. By a long train of experiments, made
in various ways, and often repeated, I ascertained that the proportion
in which these ingredients exist in sugar, are nearly eight parts of
hydrogen, 64 parts of oxygen, and 28 parts of charcoal, all by weight,
forming 100 parts of sugar.
Sugar must be mixed with about four times its weight of water, to render
it susceptible of fermentation; and even then the equilibrium of its
elements would remain undisturbed, without the assistance of some
substance, to give a commencement to the fermentation. This is
accomplished by means of a little yeast from beer; and, when the
fermentation is once excited, it continues of itself until completed. I
shall, in another place, give an account of the effects of yeast, and
other ferments, upon fermentable substances. I have usually employed 10
libs. of yeast, in the state of paste, for each 100 libs. of sugar,
with as much water as is four times the weight of the sugar. I shall
give the results of my experiments exactly as they were obtained,
preserving even the fractions produced by calculation.
TABLE I. _Materials of Fermentation._
libs. oz. gros grs.
Water 400 0 0 0
Sugar 100 0 0 0
Yeast in paste, 10 libs. { Water 7 3 6 44
composed of { Dry yeast 2 12 1 28
----------------------
Total 510
TABLE II. _Constituent Elements of the Materials of Fermentation._
libs. oz. gros grs.
407 libs. 3 oz. 6 gros 44 grs. { Hydrogen 61 1 2 71.40
of water, composed of { Oxygen 346 2 3 44.60
{ Hydrogen 8 0 0 0
100 libs. sugar, composed of { Oxygen 64 0 0 0
{ Charcoal 28 0 0 0
{ Hydrogen 0 4 5 9.30
2 libs. 12 oz. 1 gros 28 grs. of { Oxygen 1 10 2 28.76
dry yeast, composed of { Charcoal 0 12 4 59
{ Azote 0 0 5 2.94
-----------------------
Total weight 510 0 0 0
TABLE III. _Recapitulation of these Elements._
libs. oz. gros grs.
Oxygen:
of the water 340 0 0 0 }
of the water } libs. oz. gros grs.
in the yeast 6 2 3 44.60 } 411 12 6 1.36
of the sugar 64 0 0 0 }
of the dry yeast 1 10 2 28.76 }
Hydrogen:
of the water 60 0 0 0 }
of the water }
in the yeast 1 1 2 71.40 } 69 6 0 8.70
of the sugar 8 0 0 0 }
of the dry yeast 0 4 5 9.30 }
Charcoal:
of the sugar 28 0 0 0 }
of the yeast 0 12 4 59.00 } 28 12 4 59.00
Azote of the yeast - - - - } 0 0 5 2.94
--------------------------
In all 510 0 0 0
Having thus accurately determined the nature and quantity of the
constituent elements of the materials submitted to fermentation, we have
next to examine the products resulting from that process. For this
purpose, I placed the above 510 libs. of fermentable liquor in a
proper[26] apparatus, by means of which I could accurately determine the
quantity and quality of gas disengaged during the fermentation, and
could even weigh every one of the products separately, at any period of
the process I judged proper. An hour or two after the substances are
mixed together, especially if they are kept in a temperature of from 15°
(65.75°) to 18° (72.5°) of the thermometer, the first marks of
fermentation commence; the liquor turns thick and frothy, little
globules of air are disengaged, which rise and burst at the surface; the
quantity of these globules quickly increases, and there is a rapid and
abundant production of very pure carbonic acid, accompanied with a scum,
which is the yeast separating from the mixture. After some days, less or
more according to the degree of heat, the intestine motion and
disengagement of gas diminish; but these do not cease entirely, nor is
the fermentation completed for a considerable time. During the process,
35 libs. 5 oz. 4 gros 19 grs. of dry carbonic acid are
disengaged, which carry alongst with them 13 libs. 14 oz. 5 gros
of water. There remains in the vessel 460 libs. 11 oz. 6 gros 53
grs. of vinous liquor, slightly acidulous. This is at first muddy, but
clears of itself, and deposits a portion of yeast. When we separately
analise all these substances, which is effected by very troublesome
processes, we have the results as given in the following Tables. This
process, with all the subordinate calculations and analyses, will be
detailed at large in the Memoirs of the Academy.
TABLE IV. _Product of Fermentation._
libs. oz. gros grs.
35 libs. 5 oz. 4 gros 19 grs. { Oxygen 25 7 1 34
of carbonic acid, composed of { Charcoal 9 14 2 57
408 libs. 15 oz. 5 gros 14 grs. { Oxygen 347 10 0 59
of water, composed of { Hydrogen 61 5 4 27
{ Oxygen, combined
{ with hydrogen 31 6 1 64
{ Hydrogen, combined
57 libs. 11 oz. 1 gros 58 grs. { with oxygen 5 8 5 3
of dry alkohol, composed of { Hydrogen, combined
{ with charcoal 4 0 5 0
{ Charcoal, combined
{ with hydrogen 16 11 5 63
2 libs. 8 oz. of dry acetous { Hydrogen 0 2 4 0
acid, composed of { Oxygen 1 11 4 0
{ Charcoal 0 10 0 0
4 libs. 1 oz. 4 gros 3 grs. { Hydrogen 0 5 1 67
of residuum of sugar, { Oxygen 2 9 7 27
composed of { Charcoal 1 2 2 53
{ Hydrogen 0 2 2 41
1 lib. 6 oz. 0 gros 5 grs. { Oxygen 0 13 1 14
of dry yeast, composed of { Charcoal 0 6 2 30
{ Azote 0 0 2 37
--- -----------------
510 libs. Total 510 0 0 0
TABLE V. _Recapitulation of the Products._
----------------------------------------------------------------------------
libs. oz. gros grs.
409 libs. 10 oz. 0 gros 54 grs. { Water 347 10 0 59
of oxygen contained in the { Carbonic acid 25 7 1 34
{ Alkohol 31 6 1 64
{ Acetous acid 1 11 4 0
{ Residuum of sugar 2 9 7 27
{ Yeast 0 13 1 14
28 libs. 12 oz. 5 gros 59 grs. { Carbonic acid 9 14 2 57
of charcoal contained { Alkohol 16 11 5 63
in the { Acetous acid 0 10 0 0
{ Residuum of sugar 1 2 2 53
{ Yeast 0 6 2 30
{ Water 61 5 4 27
71 libs. 8 oz. 6 gros 66 grs. { Water of the alkohol 5 8 5 3
of hydrogen contained { Combined with the
in the { charcoal of the alko. 4 0 5 0
{ Acetous acid 0 2 4 0
{ Residuum of sugar 0 5 1 67
{ Yeast 0 2 2 41
2 gros 37 grs. of azote in the yeast 0 0 2 37
--- ---------------
510 libs. Total 510 0 0 0
In these results, I have been exact, even to grains; not that it is
possible, in experiments of this nature, to carry our accuracy so far,
but as the experiments were made only with a few pounds of sugar, and
as, for the sake of comparison, I reduced the results of the actual
experiments to the quintal or imaginary hundred pounds, I thought it
necessary to leave the fractional parts precisely as produced by
calculation.
When we consider the results presented by these tables with attention,
it is easy to discover exactly what occurs during fermentation. In the
first place, out of the 100 libs. of sugar employed, 4 libs. 1 oz.
4 gros 3 grs. remain, without having suffered decomposition; so
that, in reality, we have only operated upon 95 libs. 14 oz. 3
gros 69 grs. of sugar; that is to say, upon 61 libs. 6 oz. 45
grs. of oxygen, 7 libs. 10 oz. 6 gros 6 grs. of hydrogen, and
26 libs. 13 oz. 5 gros 19 grs. of charcoal. By comparing these
quantities, we find that they are fully sufficient for forming the whole
of the alkohol, carbonic acid and acetous acid produced by the
fermentation. It is not, therefore, necessary to suppose that any water
has been decomposed during the experiment, unless it be pretended that
the oxygen and hydrogen exist in the sugar in that state. On the
contrary, I have already made it evident that hydrogen, oxygen and
charcoal, the three constituent elements of vegetables, remain in a
state of equilibrium or mutual union with each other which subsists so
long as this union remains undisturbed by increased temperature, or by
some new compound attraction; and that then only these elements
combine, two and two together, to form water and carbonic acid.
The effects of the vinous fermentation upon sugar is thus reduced to the
mere separation of its elements into two portions; one part is
oxygenated at the expence of the other, so as to form carbonic acid,
whilst the other part, being deoxygenated in favour of the former, is
converted into the combustible substance alkohol; therefore, if it were
possible to reunite alkohol and carbonic acid together, we ought to form
sugar. It is evident that the charcoal and hydrogen in the alkohol do
not exist in the state of oil, they are combined with a portion of
oxygen, which renders them miscible with water; wherefore these three
substances, oxygen, hydrogen, and charcoal, exist here likewise in a
species of equilibrium or reciprocal combination; and in fact, when they
are made to pass through a red hot tube of glass or porcelain, this
union or equilibrium is destroyed, the elements become combined, two and
two, and water and carbonic acid are formed.
I had formally advanced, in my first Memoirs upon the formation of
water, that it was decomposed in a great number of chemical experiments,
and particularly during the vinous fermentation. I then supposed that
water existed ready formed in sugar, though I am now convinced that
sugar only contains the elements proper for composing it. It may be
readily conceived, that it must have cost me a good deal to abandon my
first notions, but by several years reflection, and after a great number
of experiments and observations upon vegetable substances, I have fixed
my ideas as above.
I shall finish what I have to say upon vinous fermentation, by
observing, that it furnishes us with the means of analysing sugar and
every vegetable fermentable matter. We may consider the substances
submitted to fermentation, and the products resulting from that
operation, as forming an algebraic equation; and, by successively
supposing each of the elements in this equation unknown, we can
calculate their values in succession, and thus verify our experiments by
calculation, and our calculation by experiment reciprocally. I have
often successfully employed this method for correcting the first results
of my experiments, and to direct me in the proper road for repeating
them to advantage. I have explained myself at large upon this subject,
in a Memoir upon vinous fermentation already presented to the Academy,
and which will speedily be published.
FOOTNOTES:
[26] The above apparatus is described in the Third Part.--A.
CHAP. XIV.
_Of the Putrefactive Fermentation._
The phenomena of putrefaction are caused, like those of vinous
fermentation, by the operation of very complicated affinities. The
constituent elements of the bodies submitted to this process cease to
continue in equilibrium in the threefold combination, and form
themselves anew into binary combinations[27], or compounds, consisting
of two elements only; but these are entirely different from the results
produced by the vinous fermentation. Instead of one part of the hydrogen
remaining united with part of the water and charcoal to form alkohol, as
in the vinous fermentation, the whole of the hydrogen is dissipated,
during putrefaction, in the form of hydrogen gas, whilst, at the same
time, the oxygen and charcoal, uniting with caloric, escape in the form
of carbonic acid gas; so that, when the whole process is finished,
especially if the materials have been mixed with a sufficient quantity
of water, nothing remains but the earth of the vegetable mixed with a
small portion of charcoal and iron. Thus putrefaction is nothing more
than a complete analysis of vegetable substance, during which the whole
of the constituent elements is disengaged in form of gas, except the
earth, which remains in the state of mould[28].
Such is the result of putrefaction when the substances submitted to it
contain only oxygen, hydrogen, charcoal and a little earth. But this
case is rare, and these substances putrify imperfectly and with
difficulty, and require a considerable time to complete their
putrefaction. It is otherwise with substances containing azote, which
indeed exists in all animal matters, and even in a considerable number
of vegetable substances. This additional element is remarkably
favourable to putrefaction; and for this reason animal matter is mixed
with vegetable, when the putrefaction of these is wished to be hastened.
The whole art of forming composts and dunghills, for the purposes of
agriculture, consists in the proper application of this admixture.
The addition of azote to the materials of putrefaction not only
accelerates the process, that element likewise combines with part of
the hydrogen, and forms a new substance called _volatile alkali_ or
_ammoniac_. The results obtained by analysing animal matters, by
different processes, leave no room for doubt with regard to the
constituent elements of ammoniac; whenever the azote has been previously
separated from these substances, no ammoniac is produced; and in all
cases they furnish ammoniac only in proportion to the azote they
contain. This composition of ammoniac is likewise fully proved by Mr
Berthollet, in the Memoirs of the Academy for 1785, p. 316. where he
gives a variety of analytical processes by which ammoniac is decomposed,
and its two elements, azote and hydrogen, procured separately.
I already mentioned in Chap. X. that almost all combustible bodies were
capable of combining with each other; hydrogen gas possesses this
quality in an eminent degree, it dissolves charcoal, sulphur, and
phosphorus, producing the compounds named _carbonated hydrogen gas_,
_sulphurated hydrogen gas_, and _phosphorated hydrogen gas_. The two
latter of these gasses have a peculiarly disagreeable flavour; the
sulphurated hydrogen gas has a strong resemblance to the smell of rotten
eggs, and the phosphorated smells exactly like putrid fish. Ammoniac has
likewise a peculiar odour, not less penetrating, or less disagreeable,
than these other gasses. From the mixture of these different flavours
proceeds the fetor which accompanies the putrefaction of animal
substances. Sometimes ammoniac predominates, which is easily perceived
by its sharpness upon the eyes; sometimes, as in feculent matters, the
sulphurated gas is most prevalent; and sometimes, as in putrid herrings,
the phosphorated hydrogen gas is most abundant.
I long supposed that nothing could derange or interrupt the course of
putrefaction; but Mr Fourcroy and Mr Thouret have observed some peculiar
phenomena in dead bodies, buried at a certain depth, and preserved to a
certain degree, from contact with air; having found the muscular flesh
frequently converted into true animal fat. This must have arisen from
the disengagement of the azote, naturally contained in the animal
substance, by some unknown cause, leaving only the hydrogen and charcoal
remaining, which are the elements proper for producing fat or oil. This
observation upon the possibility of converting animal substances into
fat may some time or other lead to discoveries of great importance to
society. The faeces of animals, and other excrementitious matters, are
chiefly composed of charcoal and hydrogen, and approach considerably to
the nature of oil, of which they furnish a considerable quantity by
distillation with a naked fire; but the intolerable foetor which
accompanies all the products of these substances prevents our expecting
that, at least for a long time, they can be rendered useful in any other
way than as manures.
I have only given conjectural approximations in this Chapter upon the
composition of animal substances, which is hitherto but imperfectly
understood. We know that they are composed of hydrogen, charcoal, azote,
phosphorus, and sulphur, all of which, in a state of quintuple
combination, are brought to the state of oxyd by a larger or smaller
quantity of oxygen. We are, however, still unacquainted with the
proportions in which these substances are combined, and must leave it to
time to complete this part of chemical analysis, as it has already done
with several others.
FOOTNOTES:
[27] Binary combinations are such as consist of two simple elements
combined together. Ternary, and quaternary, consist of three and four
elements.--E.
[28] In the Third Part will be given the description of an apparatus
proper for being used in experiments of this kind.--A.
CHAP. XV.
_Of the Acetous Fermentation._
The acetous fermentation is nothing more than the acidification or
oxygenation of wine[29], produced in the open air by means of the
absorption of oxygen. The resulting acid is the acetous acid, commonly
called Vinegar, which is composed of hydrogen and charcoal united
together in proportions not yet ascertained, and changed into the acid
state by oxygen. As vinegar is an acid, we might conclude from analogy
that it contains oxygen, but this is put beyond doubt by direct
experiments: In the first place, we cannot change wine into vinegar
without the contact of air containing oxygen; secondly, this process is
accompanied by a diminution of the volume of the air in which it is
carried on from the absorption of its oxygen; and, thirdly, wine may be
changed into vinegar by any other means of oxygenation.
Independent of the proofs which these facts furnish of the acetous acid
being produced by the oxygenation of wine, an experiment made by Mr
Chaptal, Professor of Chemistry at Montpellier, gives us a distinct view
of what takes place in this process. He impregnated water with about its
own bulk of carbonic acid from fermenting beer, and placed this water in
a cellar in vessels communicating with the air, and in a short time the
whole was converted into acetous acid. The carbonic acid gas procured
from beer vats in fermentation is not perfectly pure, but contains a
small quantity of alkohol in solution, wherefore water impregnated with
it contains all the materials necessary for forming the acetous acid.
The alkohol furnishes hydrogen and one portion of charcoal, the carbonic
acid furnishes oxygen and the rest of the charcoal, and the air of the
atmosphere furnishes the rest of the oxygen necessary for changing the
mixture into acetous acid. From this observation it follows, that
nothing but hydrogen is wanting to convert carbonic acid into acetous
acid; or more generally, that, by means of hydrogen, and according to
the degree of oxygenation, carbonic acid may be changed into all the
vegetable acids; and, on the contrary, that, by depriving any of the
vegetable acids of their hydrogen, they may be converted into carbonic
acid.
Although the principal facts relating to the acetous acid are well
known, yet numerical exactitude is still wanting, till furnished by more
exact experiments than any hitherto performed; wherefore I shall not
enlarge any farther upon the subject. It is sufficiently shown by what
has been said, that the constitution of all the vegetable acids and
oxyds is exactly conformable to the formation of vinegar; but farther
experiments are necessary to teach us the proportion of the constituent
elements in all these acids and oxyds. We may easily perceive, however,
that this part of chemistry, like all the rest of its divisions, makes
rapid progress towards perfection, and that it is already rendered
greatly more simple than was formerly believed.
FOOTNOTES:
[29] The word Wine, in this chapter, is used to signify the liquor
produced by the vinous fermentation, whatever vegetable substance may
have been used for obtaining it.--E.
CHAP. XVI.
_Of the Formation of Neutral Salts, and of their different Bases._
We have just seen that all the oxyds and acids from the animal and
vegetable kingdoms are formed by means of a small number of simple
elements, or at least of such as have not hitherto been susceptible of
decomposition, by means of combination with oxygen; these are azote,
sulphur, phosphorus, charcoal, hydrogen, and the muriatic radical[30].
We may justly admire the simplicity of the means employed by nature to
multiply qualities and forms, whether by combining three or four
acidifiable bases in different proportions, or by altering the dose of
oxygen employed for oxydating or acidifying them. We shall find the
means no less simple and diversified, and as abundantly productive of
forms and qualities, in the order of bodies we are now about to treat
of.
Acidifiable substances, by combining with oxygen, and their consequent
conversion into acids, acquire great susceptibility of farther
combination; they become capable of uniting with earthy and metallic
bodies, by which means neutral salts are formed. Acids may therefore be
considered as true _salifying_ principles, and the substances with which
they unite to form neutral salts may be called _salifiable_ bases: The
nature of the union which these two principles form with each other is
meant as the subject of the present chapter.
This view of the acids prevents me from considering them as salts,
though they are possessed of many of the principal properties of saline
bodies, as solubility in water, &c. I have already observed that they
are the result of a first order of combination, being composed of two
simple elements, or at least of elements which act as if they were
simple, and we may therefore rank them, to use the language of Stahl, in
the order of _mixts_. The neutral salts, on the contrary, are of a
secondary order of combination, being formed by the union of two _mixts_
with each other, and may therefore be termed _compounds_. Hence I shall
not arrange the alkalies[31] or earths in the class of salts, to which
I allot only such as are composed of an oxygenated substance united to
a base.
I have already enlarged sufficiently upon the formation of acids in the
preceding chapter, and shall not add any thing farther upon that
subject; but having as yet given no account of the salifiable bases
which are capable of uniting with them to form neutral salts, I mean, in
this chapter, to give an account of the nature and origin of each of
these bases. These are potash, soda, ammoniac, lime, magnesia, barytes,
argill[32], and all the metallic bodies.
§ 1. _Of Potash._
We have already shown, that, when a vegetable substance is submitted to
the action of fire in distilling vessels, its component elements,
oxygen, hydrogen, and charcoal, which formed a threefold combination in
a state of equilibrium, unite, two and two, in obedience to affinities
which act conformable to the degree of heat employed. Thus, at the
first application of the fire, whenever the heat produced exceeds the
temperature of boiling water, part of the oxygen and hydrogen unite to
form water; soon after the rest of the hydrogen, and part of the
charcoal, combine into oil; and, lastly, when the fire is pushed to the
red heat, the oil and water, which had been formed in the early part of
the process, become again decomposed, the oxygen and charcoal unite to
form carbonic acid, a large quantity of hydrogen gas is set free, and
nothing but charcoal remains in the retort.
A great part of these phenomena occur during the combustion of
vegetables in the open air; but, in this case, the presence of the air
introduces three new substances, the oxygen and azote of the air and
caloric, of which two at least produce considerable changes in the
results of the operation. In proportion as the hydrogen of the
vegetable, or that which results from the decomposition of the water, is
forced out in the form of hydrogen gas by the progress of the fire, it
is set on fire immediately upon getting in contact with the air, water
is again formed, and the greater part of the caloric of the two gasses
becoming free produces flame. When all the hydrogen gas is driven out,
burnt, and again reduced to water, the remaining charcoal continues to
burn, but without flame; it is formed into carbonic acid, which carries
off a portion of caloric sufficient to give it the gasseous form; the
rest of the caloric, from the oxygen of the air, being set free,
produces the heat and light observed during the combustion of charcoal.
The whole vegetable is thus reduced into water and carbonic acid, and
nothing remains but a small portion of gray earthy matter called ashes,
being the only really fixed principles which enter into the constitution
of vegetables.
The earth, or rather ashes, which seldom exceeds a twentieth part of the
weight of the vegetable, contains a substance of a particular nature,
known under the name of fixed vegetable alkali, or potash. To obtain it,
water is poured upon the ashes, which dissolves the potash, and leaves
the ashes which are insoluble; by afterwards evaporating the water, we
obtain the potash in a white concrete form: It is very fixed even in a
very high degree of heat. I do not mean here to describe the art of
preparing potash, or the method of procuring it in a state of purity,
but have entered upon the above detail that I might not use any word not
previously explained.
The potash obtained by this process is always less or more saturated
with carbonic acid, which is easily accounted for: As the potash does
not form, or at least is not set free, but in proportion as the
charcoal of the vegetable is converted into carbonic acid by the
addition of oxygen, either from the air or the water, it follows, that
each particle of potash, at the instant of its formation, or at least of
its liberation, is in contact with a particle of carbonic acid, and, as
there is a considerable affinity between these two substances, they
naturally combine together. Although the carbonic acid has less affinity
with potash than any other acid, yet it is difficult to separate the
last portions from it. The most usual method of accomplishing this is to
dissolve the potash in water; to this solution add two or three times
its weight of quick-lime, then filtrate the liquor and evaporate it in
close vessels; the saline substance left by the evaporation is potash
almost entirely deprived of carbonic acid. In this state it is soluble
in an equal weight of water, and even attracts the moisture of the air
with great avidity; by this property it furnishes us with an excellent
means of rendering air or gas dry by exposing them to its action. In
this state it is soluble in alkohol, though not when combined with
carbonic acid; and Mr Berthollet employs this property as a method of
procuring potash in the state of perfect purity.
All vegetables yield less or more of potash in consequence of
combustion, but it is furnished in various degrees of purity by
different vegetables; usually, indeed, from all of them it is mixed
with different salts from which it is easily separable. We can hardly
entertain a doubt that the ashes, or earth which is left by vegetables
in combustion, pre-existed in them before they were burnt, forming what
may be called the skeleton, or osseous part of the vegetable. But it is
quite otherwise with potash; this substance has never yet been procured
from vegetables but by means of processes or intermedia capable of
furnishing oxygen and azote, such as combustion, or by means of nitric
acid; so that it is not yet demonstrated that potash may not be a
produce from these operations. I have begun a series of experiments upon
this object, and hope soon to be able to give an account of their
results.
§ 2. _Of Soda._
Soda, like potash, is an alkali procured by lixiviation from the ashes
of burnt plants, but only from those which grow upon the sea-side, and
especially from the herb _kali_, whence is derived the name _alkali_,
given to this substance by the Arabians. It has some properties in
common with potash, and others which are entirely different: In general,
these two substances have peculiar characters in their saline
combinations which are proper to each, and consequently distinguish them
from each other; thus soda, which, as obtained from marine plants, is
usually entirely saturated with carbonic acid, does not attract the
humidity of the atmosphere like potash, but, on the contrary,
desiccates, its cristals effloresce, and are converted into a white
powder having all the properties of soda, which it really is, having
only lost its water of cristallization.
Hitherto we are not better acquainted with the constituent elements of
soda than with those of potash, being equally uncertain whether it
previously existed ready formed in the vegetable or is a combination of
elements effected by combustion. Analogy leads us to suspect that azote
is a constituent element of all the alkalies, as is the case with
ammoniac; but we have only slight presumptions, unconfirmed by any
decisive experiments, respecting the composition of potash and soda.
§ 3. _Of Ammoniac._
We have, however, very accurate knowledge of the composition of
ammoniac, or volatile alkali, as it is called by the old chemists. Mr
Berthollet, in the Memoirs of the Academy for 1784, p. 316. has proved
by analysis, that 1000 parts of this substance consist of about 807
parts of azote combined with 193 parts of hydrogen.
Ammoniac is chiefly procurable from animal substances by distillation,
during which process the azote and hydrogen necessary to its formation
unite in proper proportions; it is not, however, procured pure by this
process, being mixed with oil and water, and mostly saturated with
carbonic acid. To separate these substances it is first combined with an
acid, the muriatic for instance, and then disengaged from that
combination by the addition of lime or potash. When ammoniac is thus
produced in its greatest degree of purity it can only exist under the
gasseous form, at least in the usual temperature of the atmosphere, it
has an excessively penetrating smell, is absorbed in large quantities by
water, especially if cold and assisted by compression. Water thus
saturated with ammoniac has usually been termed volatile alkaline fluor;
we shall call it either simply ammoniac, or liquid ammoniac, and
ammoniacal gas when it exists in the aëriform state.
§ 4. _Of Lime, Magnesia, Barytes, and Argill._
The composition of these four earths is totally unknown, and, until by
new discoveries their constituent elements are ascertained, we are
certainly authorised to consider them as simple bodies. Art has no share
in the production of these earths, as they are all procured ready
formed from nature; but, as they have all, especially the three first,
great tendency to combination, they are never found pure. Lime is
usually saturated with carbonic acid in the state of chalk, calcarious
spars, most of the marbles, &c.; sometimes with sulphuric acid, as in
gypsum and plaster stones; at other times with fluoric acid forming
vitreous or fluor spars; and, lastly, it is found in the waters of the
sea, and of saline springs, combined with muriatic acid. Of all the
salifiable bases it is the most universally spread through nature.
Magnesia is found in mineral waters, for the most part combined with
sulphuric acid; it is likewise abundant in sea-water, united with
muriatic acid; and it exists in a great number of stones of different
kinds.
Barytes is much less common than the three preceding earths; it is found
in the mineral kingdom, combined with sulphuric acid, forming heavy
spars, and sometimes, though rarely, united to carbonic acid.
Argill, or the base of alum, having less tendency to combination than
the other earths, is often found in the state of argill, uncombined with
any acid. It is chiefly procurable from clays, of which, properly
speaking, it is the base, or chief ingredient.
§ 5. _Of Metallic Bodies._
The metals, except gold, and sometimes silver, are rarely found in the
mineral kingdom in their metallic state, being usually less or more
saturated with oxygen, or combined with sulphur, arsenic, sulphuric
acid, muriatic acid, carbonic acid, or phosphoric acid. Metallurgy, or
the docimastic art, teaches the means of separating them from these
foreign matters; and for this purpose we refer to such chemical books as
treat upon these operations.
We are probably only acquainted as yet with a part of the metallic
substances existing in nature, as all those which have a stronger
affinity to oxygen, than charcoal possesses, are incapable of being
reduced to the metallic state, and, consequently, being only presented
to our observation under the form of oxyds, are confounded with earths.
It is extremely probable that barytes, which we have just now arranged
with earths, is in this situation; for in many experiments it exhibits
properties nearly approaching to those of metallic bodies. It is even
possible that all the substances we call earths may be only metallic
oxyds, irreducible by any hitherto known process.
Those metallic bodies we are at present acquainted with, and which we
can reduce to the metallic or reguline state, are the following
seventeen:
1. Arsenic.
2. Molybdena.
3. Tungstein.
4. Manganese.
5. Nickel.
6. Cobalt.
7. Bismuth.
8. Antimony.
9. Zinc.
10. Iron.
11. Tin.
12. Lead.
13. Copper.
14. Mercury.
15. Silver.
16. Platina.
17. Gold.
I only mean to consider these as salifiable bases, without entering at
all upon the consideration of their properties in the arts, and for the
uses of society. In these points of view each metal would require a
complete treatise, which would lead me far beyond the bounds I have
prescribed for this work.
FOOTNOTES:
[30] I have not ventured to omit this element, as here enumerated with
the other principles of animal and vegetable substances, though it is
not at all taken notice of in the preceding chapters as entering into
the composition of these bodies.--E.
[31] Perhaps my thus rejecting the alkalies from the class of salts may
be considered as a capital defect in the method I have adopted, and I am
ready to admit the charge; but this inconvenience is compensated by so
many advantages, that I could not think it of sufficient consequence to
make me alter my plan.--A.
[32] Called Alumine by Mr Lavoisier; but as Argill has been in a manner
naturalized to the language for this substance by Mr Kirwan, I have
ventured to use it in preference.--E.
CHAP. XVII.
_Continuation of the Observations upon Salifiable Bases, and the
Formation of Neutral Salts._
It is necessary to remark, that earths and alkalies unite with acids to
form neutral salts without the intervention of any medium, whereas
metallic substances are incapable of forming this combination without
being previously less or more oxygenated; strictly speaking, therefore,
metals are not soluble in acids, but only metallic oxyds. Hence, when we
put a metal into an acid for solution, it is necessary, in the first
place, that it become oxygenated, either by attracting oxygen from the
acid or from the water; or, in other words, that a metal cannot be
dissolved in an acid unless the oxygen, either of the acid, or of the
water mixed with it, has a stronger affinity to the metal than to the
hydrogen or the acidifiable base; or, what amounts to the same thing,
that no metallic solution can take place without a previous
decomposition of the water, or the acid in which it is made. The
explanation of the principal phenomena of metallic solution depends
entirely upon this simple observation, which was overlooked even by the
illustrious Bergman.
The first and most striking of these is the effervescence, or, to speak
less equivocally, the disengagement of gas which takes place during the
solution; in the solutions made in nitric acid this effervescence is
produced by the disengagement of nitrous gas; in solutions with
sulphuric acid it is either sulphurous acid gas or hydrogen gas,
according as the oxydation of the metal happens to be made at the
expence of the sulphuric acid or of the water. As both nitric acid and
water are composed of elements which, when separate, can only exist in
the gasseous form, at least in the common temperature of the atmosphere,
it is evident that, whenever either of these is deprived of its oxygen,
the remaining element must instantly expand and assume the state of gas;
the effervescence is occasioned by this sudden conversion from the
liquid to the gasseous state. The same decomposition, and consequent
formation of gas, takes place when solutions of metals are made in
sulphuric acid: In general, especially by the humid way, metals do not
attract all the oxygen it contains; they therefore reduce it, not into
sulphur, but into sulphurous acid, and as this acid can only exist as
gas in the usual temperature, it is disengaged, and occasions
effervescence.
The second phenomenon is, that, when the metals have been previously
oxydated, they all dissolve in acids without effervescence: This is
easily explained; because, not having now any occasion for combining
with oxygen, they neither decompose the acid nor the water by which, in
the former case, the effervescence is occasioned.
A third phenomenon, which requires particular consideration, is, that
none of the metals produce effervescence by solution in oxygenated
muriatic acid. During this process the metal, in the first place,
carries off the excess of oxygen from the oxygenated muriatic acid, by
which it becomes oxydated, and reduces the acid to the state of ordinary
muriatic acid. In this case there is no production of gas, not that the
muriatic acid does not tend to exist in the gasseous state in the common
temperature, which it does equally with the acids formerly mentioned,
but because this acid, which otherwise would expand into gas, finds more
water combined with the oxygenated muriatic acid than is necessary to
retain it in the liquid form; hence it does not disengage like the
sulphurous acid, but remains, and quietly dissolves and combines with
the metallic oxyd previously formed from its superabundant oxygen.
The fourth phenomenon is, that metals are absolutely insoluble in such
acids as have their bases joined to oxygen by a stronger affinity than
these metals are capable of exerting upon that acidifying principle.
Hence silver, mercury, and lead, in their metallic states, are insoluble
in muriatic acid, but, when previously oxydated, they become readily
soluble without effervescence.
From these phenomena it appears that oxygen is the bond of union between
metals and acids; and from this we are led to suppose that oxygen is
contained in all substances which have a strong affinity with acids:
Hence it is very probable the four eminently salifiable earths contain
oxygen, and their capability of uniting with acids is produced by the
intermediation of that element. What I have formerly noticed relative to
these earths is considerably strengthened by the above considerations,
viz. that they may very possibly be metallic oxyds, with which oxygen
has a stronger affinity than with charcoal, and consequently not
reducible by any known means.
All the acids hitherto known are enumerated in the following table, the
first column of which contains the names of the acids according to the
new nomenclature, and in the second column are placed the bases or
radicals of these acids, with observations.
_Names of the Acids._ _Names of the Bases, with Observations._
1. Sulphurous }Sulphur.
2. Sulphuric }
3. Phosphorous }Phosphorus.
4. Phosphoric }
5. Muriatic }Muriatic radical or base, hitherto unknown.
6. Oxygenated muriatic }
7. Nitrous }
8. Nitric }Azote.
9. Oxygenated nitric }
10. Carbonic Charcoal
}The bases or radicals of all these acids
11. Acetous }seem to be formed by a combination
12. Acetic }of charcoal and hydrogen;
13. Oxalic }and the only difference seems to be
14. Tartarous }owing to the different proportions in
15. Pyro-tartarous }which these elements combine to form
16. Citric }their bases, and to the different doses
17. Malic }of oxygen in their acidification. A
18. Pyro-lignous }connected series of accurate experiments
19. Pyro-mucous }is still wanted upon this subject.
20. Gallic }Our knowledge of the bases of
21. Prussic }these acids is hitherto imperfect; we
22. Benzoic }only know that they contain hydrogen
23. Succinic }and charcoal as principal elements,
24. Camphoric }and that the prussic acid contains
25. Lactic }azote.
26. Saccholactic }
27. Bombic }The base of these and all acids
28. Formic }procured from animal substances seems
29. Sebacic }to consist of charcoal, hydrogen,
}phosphorous, and azote.
30. Boracic }The bases of these two are hitherto
31. Fluoric }entirely unknown.
32. Antimonic Antimony.
33. Argentic Silver.
34. Arseniac(A) Arsenic.
35. Bismuthic Bismuth.
36. Cobaltic Cobalt.
37. Cupric Copper.
38. Stannic Tin.
39. Ferric Iron.
40. Manganic Manganese.
41. Mercuric(B) Mercury.
42. Molybdic Molybdena.
43. Nickolic Nickel.
44. Auric Gold.
45. Platinic Platina.
46. Plumbic Lead.
47. Tungstic Tungstein.
48. Zincic Zinc.
[Note A: This term swerves a little from the rule in making the name of
this acid terminate in _ac_ instead of _ic_. The base and acid are
distinguished in French by _arsenic_ and _arsenique_; but, having chosen
the English termination _ic_ to translate the French _ique_, I was
obliged to use this small deviation.--E.]
[Note B: Mr Lavoisier has hydrargirique; but mercurius being used for
the base or metal, the name of the acid, as above, is equally regular,
and less harsh.--E.]
In this list, which contains 48 acids, I have enumerated 17 metallic
acids hitherto very imperfectly known, but upon which Mr Berthollet is
about to publish a very important work. It cannot be pretended that all
the acids which exist in nature, or rather all the acidifiable bases,
are yet discovered; but, on the other hand, there are considerable
grounds for supposing that a more accurate investigation than has
hitherto been attempted will diminish the number of the vegetable acids,
by showing that several of these, at present considered as distinct
acids, are only modifications of others. All that can be done in the
present state of our knowledge is, to give a view of chemistry as it
really is, and to establish fundamental principles, by which such bodies
as may be discovered in future may receive names, in conformity with one
uniform system.
The known salifiable bases, or substances capable of being converted
into neutral salts by union with acids, amount to 24; viz. 3 alkalies, 4
earths, and 17 metallic substances; so that, in the present state of
chemical knowledge, the whole possible number of neutral salts amounts
to 1152[33]. This number is upon the supposition that the metallic acids
are capable of dissolving other metals, which is a new branch of
chemistry not hitherto investigated, upon which depends all the metallic
combinations named _vitreous_. There is reason to believe that many of
these supposable saline combinations are not capable of being formed,
which must greatly reduce the real number of neutral salts producible by
nature and art. Even if we suppose the real number to amount only to
five or six hundred species of possible neutral salts, it is evident
that, were we to distinguish them, after the manner of the ancients,
either by the names of their first discoverers, or by terms derived from
the substances from which they are procured, we should at last have such
a confusion of arbitrary designations, as no memory could possibly
retain. This method might be tolerable in the early ages of chemistry,
or even till within these twenty years, when only about thirty species
of salts were known; but, in the present times, when the number is
augmenting daily, when every new acid gives us 24 or 48 new salts,
according as it is capable of one or two degrees of oxygenation, a new
method is certainly necessary. The method we have adopted, drawn from
the nomenclature of the acids, is perfectly analogical, and, following
nature in the simplicity of her operations, gives a natural and easy
nomenclature applicable to every possible neutral salt.
In giving names to the different acids, we express the common property
by the generical term _acid_, and distinguish each species by the name
of its peculiar acidifiable base. Hence the acids formed by the
oxygenation of sulphur, phosphorus, charcoal, &c. are called _sulphuric
acid_, _phosphoric acid_, _carbonic acid_, &c. We thought it likewise
proper to indicate the different degrees of saturation with oxygen, by
different terminations of the same specific names. Hence we distinguish
between sulphurous and sulphuric, and between phosphorous and phosphoric
acids, &c.
By applying these principles to the nomenclature of neutral salts, we
give a common term to all the neutral salts arising from the combination
of one acid, and distinguish the species by adding the name of the
salifiable base. Thus, all the neutral salts having sulphuric acid in
their composition are named _sulphats_; those formed by the phosphoric
acid, _phosphats_, &c. The species being distinguished by the names of
the salifiable bases gives us _sulphat of potash_, _sulphat of soda_,
_sulphat of ammoniac_, _sulphat of lime_, _sulphat of iron_, &c. As we
are acquainted with 24 salifiable bases, alkaline, earthy, and metallic,
we have consequently 24 sulphats, as many phosphats, and so on through
all the acids. Sulphur is, however, susceptible of two degrees of
oxygenation, the first of which produces sulphurous, and the second,
sulphuric acid; and, as the neutral salts produced by these two acids,
have different properties, and are in fact different salts, it becomes
necessary to distinguish these by peculiar terminations; we have
therefore distinguished the neutral salts formed by the acids in the
first or lesser degree of oxygenation, by changing the termination _at_
into _ite_, as _sulphites_, _phosphites_[34], &c. Thus, oxygenated or
acidified sulphur, in its two degrees of oxygenation is capable of
forming 48 neutral salts, 24 of which are sulphites, and as many
sulphats; which is likewise the case with all the acids capable of two
degrees of oxygenation[35].
It were both tiresome and unnecessary to follow these denominations
through all the varieties of their possible application; it is enough to
have given the method of naming the various salts, which, when once well
understood, is easily applied to every possible combination. The name of
the combustible and acidifiable body being once known, the names of the
acid it is capable of forming, and of all the neutral combinations the
acid is susceptible of entering into, are most readily remembered. Such
as require a more complete illustration of the methods in which the new
nomenclature is applied will, in the Second Part of this book, find
Tables which contain a full enumeration of all the neutral salts, and,
in general, all the possible chemical combinations, so far as is
consistent with the present state of our knowledge. To these I shall
subjoin short explanations, containing the best and most simple means of
procuring the different species of acids, and some account of the
general properties of the neutral salts they produce.
I shall not deny, that, to render this work more complete, it would have
been necessary to add particular observations upon each species of salt,
its solubility in water and alkohol, the proportions of acid and of
salifiable base in its composition, the quantity of its water of
cristallization, the different degrees of saturation it is susceptible
of, and, finally, the degree of force or affinity with which the acid
adheres to the base. This immense work has been already begun by Messrs
Bergman, Morveau, Kirwan, and other celebrated chemists, but is hitherto
only in a moderate state of advancement, even the principles upon which
it is founded are not perhaps sufficiently accurate.
These numerous details would have swelled this elementary treatise to
much too great a size; besides that, to have gathered the necessary
materials, and to have completed all the series of experiments
requisite, must have retarded the publication of this book for many
years. This is a vast field for employing the zeal and abilities of
young chemists, whom I would advise to endeavour rather to do well than
to do much, and to ascertain, in the first place, the composition of the
acids, before entering upon that of the neutral salts. Every edifice
which is intended to resist the ravages of time should be built upon a
sure foundation; and, in the present state of chemistry, to attempt
discoveries by experiments, either not perfectly exact, or not
sufficiently rigorous, will serve only to interrupt its progress,
instead of contributing to its advancement.
FOOTNOTES:
[33] This number excludes all triple salts, or such as contain more than
one salifiable base, all the salts whose bases are over or under
saturated with acid, and those formed by the nitro-muriatic acid.--E.
[34] As all the specific names of the acids in the new nomenclature are
adjectives, they would have applied severally to the various salifiable
bases, without the invention of other terms, with perfect distinctness.
Thus, _sulphurous potash_, and _sulphuric potash_, are equally distinct
as _sulphite of potash_, and _sulphat of potash_; and have the advantage
of being more easily retained in the memory, because more naturally
arising from the acids themselves, than the arbitrary terminations
adopted by Mr Lavoisier.--E.
[35] There is yet a third degree of oxygenation of acids, as the
oxygenated muriatic and oxygenated nitric acids. The terms applicable to
the neutral salts resulting from the union of these acids with
salifiable bases is supplied by the Author in the Second Part of this
Work. These are formed by prefixing the word _oxygenated_ to the name of
the salt produced by the second degree of oxygenation. Thus,
_oxygenated_ muriat of potash, _oxygenated_ nitrat of soda, &c.--E.
PART II.
Of the Combination of Acids with Salifiable Bases, and of the Formation
of Neutral Salts.
INTRODUCTION.
If I had strictly followed the plan I at first laid down for the conduct
of this work, I would have confined myself, in the Tables and
accompanying observations which compose this Second Part, to short
definitions of the several known acids, and abridged accounts of the
processes by which they are obtainable, with a mere nomenclature or
enumeration of the neutral salts which result from the combination of
these acids with the various salifiable bases. But I afterwards found
that the addition of similar Tables of all the simple substances which
enter into the composition of the acids and oxyds, together with the
various possible combinations of these elements, would add greatly to
the utility of this work, without being any great increase to its size.
These additions, which are all contained in the twelve first sections of
this Part, and the Tables annexed to these, form a kind of
recapitulation of the first fifteen Chapters of the First Part: The rest
of the Tables and Sections contain all the saline combinations.
It must be very apparent that, in this Part of the Work, I have borrowed
greatly from what has been already published by Mr de Morveau in the
First Volume of the _Encyclopedie par ordre des Matières_. I could
hardly have discovered a better source of information, especially when
the difficulty of consulting books in foreign languages is considered. I
make this general acknowledgment on purpose to save the trouble of
references to Mr de Morveau's work in the course of the following part
of mine.
TABLE OF SIMPLE SUBSTANCES.
Simple substances belonging to all the kingdoms of nature, which may be
considered as the elements of bodies.
_New Names._ _Correspondent old Names._
Light Light.
Caloric {Heat.
{Principle or element of heat.
{Fire. Igneous fluid.
{Matter of fire and of heat.
Oxygen {Dephlogisticated air.
{Empyreal air.
{Vital air, or
{Base of vital air.
Azote {Phlogisticated air or gas.
{Mephitis, or its base.
Hydrogen {Inflammable air or gas,
{or the base of inflammable air.
Oxydable and Acidifiable simple Substance not Metallic.
_New Names._ _Correspondent old names._
Sulphur }
Phosphorous }The same names.
Charcoal }
Muriatic radical }
Fluoric radical }Still unknown.
Boracic radical }
Oxydable and Acidifiable simple Metallic Bodies
_New Names._ _Correspondent Old Names._
Antimony } { Antimony.
Arsenic } { Arsenic.
Bismuth } { Bismuth.
Cobalt } { Cobalt.
Copper } { Copper.
Gold } { Gold.
Iron } { Iron.
Lead } Regulus of { Lead.
Manganese } { Manganese.
Mercury } { Mercury.
Molybdena } { Molybdena.
Nickel } { Nickel.
Platina } { Platina.
Silver } { Silver.
Tin } { Tin.
Tungstein } { Tungstein.
Zinc } { Zinc.
Salifiable simple Earthy Substances.
_New Names._ _Correspondent old Names._
Lime {Chalk, calcareous earth.
{Quicklime.
Magnesia {Magnesia, base of Epsom salt.
{Calcined or caustic magnesia.
Barytes Barytes, or heavy earth.
Argill Clay, earth of alum.
Silex Siliceous or vitrifiable earth.
SECT. I.--_Observations upon the Table of Simple Substances._
The principle object of chemical experiments is to decompose natural
bodies, so as separately to examine the different substances which enter
into their composition. By consulting chemical systems, it will be found
that this science of chemical analysis has made rapid progress in our
own times. Formerly oil and salt were considered as elements of bodies,
whereas later observation and experiment have shown that all salts,
instead of being simple, are composed of an acid united to a base. The
bounds of analysis have been greatly enlarged by modern discoveries[36];
the acids are shown to be composed of oxygen, as an acidifying principle
common to all, united in each to a particular base. I have proved what
Mr Haffenfratz had before advanced, that these radicals of the acids
are not all simple elements, many of them being, like the oily
principle, composed of hydrogen and charcoal. Even the bases of neutral
salts have been proved by Mr Berthollet to be compounds, as he has shown
that ammoniac is composed of azote and hydrogen.
Thus, as chemistry advances towards perfection, by dividing and
subdividing, it is impossible to say where it is to end; and these
things we at present suppose simple may soon be found quite otherwise.
All we dare venture to affirm of any substance is, that it must be
considered as simple in the present state of our knowledge, and so far
as chemical analysis has hitherto been able to show. We may even presume
that the earths must soon cease to be considered as simple bodies; they
are the only bodies of the salifiable class which have no tendency to
unite with oxygen; and I am much inclined to believe that this proceeds
from their being already saturated with that element. If so, they will
fall to be considered as compounds consisting of simple substances,
perhaps metallic, oxydated to a certain degree. This is only hazarded as
a conjecture; and I trust the reader will take care not to confound what
I have related as truths, fixed on the firm basis of observation and
experiment, with mere hypothetical conjectures.
The fixed alkalies, potash, and soda, are omitted in the foregoing
Table, because they are evidently compound substances, though we are
ignorant as yet what are the elements they are composed of.
TABLE _of compound oxydable and acidifiable bases._
_Names of the radicals._
Oxydable or acidifiable { Nitro-muriatic radical or
base, from the mineral { base of the acid formerly
kingdom. { called aqua regia.
{ Tartarous radical or base.
{ Malic. }
{ Citric. }
{ Pyro-lignous. }
Oxydable or acidifiable { Pyro-mucous. }
hydro-carbonous or { Pyro-tartarous. }
carbono-hydrous radicals { Oxalic. }
from the vegetable { Acetous. }
kingdom. { Succinic. } Radicals
{ Benzoic. }
{ Camphoric. }
{ Gallic. }
}
Oxydable or acidifiable { Lactic. }
radicals from the animal { Saccholactic. }
kingdom, which { Formic. }
mostly contain azote, { Bombic. }
and frequently phosphorus. { Sebacic. }
{ Lithic. }
{ Prussic. }
_Note._--The radicals from the vegetable kingdom are converted by a
first degree of oxygenation into vegetable oxyds, such as sugar, starch,
and gum or mucus: Those of the animal kingdom by the same means form
animal oxyds, as lymph, &c.--A.
SECT. II.--_Observations upon the Table of Compound Radicals._
The older chemists being unacquainted with the composition of acids, and
not suspecting them to be formed by a peculiar radical or base for each,
united to an acidifying principle or element common to all, could not
consequently give any name to substances of which they had not the most
distant idea. We had therefore to invent a new nomenclature for this
subject, though we were at the same time sensible that this nomenclature
must be susceptible of great modification when the nature of the
compound radicals shall be better understood[37].
The compound oxydable and acidifiable radicals from the vegetable and
animal kingdoms, enumerated in the foregoing table, are not hitherto
reducible to systematic nomenclature, because their exact analysis is as
yet unknown. We only know in general, by some experiments of my own, and
some made by Mr Hassenfratz, that most of the vegetable acids, such as
the tartarous, oxalic, citric, malic, acetous, pyro-tartarous, and
pyromucous, have radicals composed of hydrogen and charcoal, combined
in such a way as to form single bases, and that these acids only differ
from each other by the proportions in which these two substances enter
into the composition of their bases, and by the degree of oxygenation
which these bases have received. We know farther, chiefly from the
experiments of Mr Berthollet, that the radicals from the animal kingdom,
and even some of those from vegetables, are of a more compound nature,
and, besides hydrogen and charcoal, that they often contain azote, and
sometimes phosphorus; but we are not hitherto possessed of sufficiently
accurate experiments for calculating the proportions of these several
substances. We are therefore forced, in the manner of the older
chemists, still to name these acids after the substances from which they
are procured. There can be little doubt that these names will be laid
aside when our knowledge of these substances becomes more accurate and
extensive; the terms _hydro-carbonous_, _hydro-carbonic_,
_carbono-hydrous_, and _carbono hydric_[38], will then become
substituted for those we now employ, which will then only remain as
testimonies of the imperfect state in which this part of chemistry was
transmitted to us by our predecessors.
It is evident that the oils, being composed of hydrogen and charcoal
combined, are true carbono-hydrous or hydro-carbonous radicals; and,
indeed, by adding oxygen, they are convertible into vegetable oxyds and
acids, according to their degrees of oxygenation. We cannot, however,
affirm that oils enter in their entire state into the composition of
vegetable oxyds and acids; it is possible that they previously lose a
part either of their hydrogen or charcoal, and that the remaining
ingredients no longer exist in the proportions necessary to constitute
oils. We still require farther experiments to elucidate these points.
Properly speaking, we are only acquainted with one compound radical from
the mineral kingdom, the nitro-muriatic, which is formed by the
combination of azote with the muriatic radical. The other compound
mineral acids have been much less attended to, from their producing less
striking phenomena.
SECT. III.--_Observations upon the Combinations of Light and Caloric
with different Substances._
I have not constructed any table of the combinations of light and
caloric with the various simple and compound substances, because our
conceptions of the nature of these combinations are not hitherto
sufficiently accurate. We know, in general, that all bodies in nature
are imbued, surrounded, and penetrated in every way with caloric, which
fills up every interval left between their particles; that, in certain
cases, caloric becomes fixed in bodies, so as to constitute a part even
of their solid substance, though it more frequently acts upon them with
a repulsive force, from which, or from its accumulation in bodies to a
greater or lesser degree, the transformation of solids into fluids, and
of fluids to aëriform elasticity, is entirely owing. We have employed
the generic name _gas_ to indicate this aëriform state of bodies
produced by a sufficient accumulation of caloric; so that, when we wish
to express the aëriform state of muriatic acid, carbonic acid, hydrogen,
water, alkohol, &c. we do it by adding the word _gas_ to their names;
thus muriatic acid gas, carbonic acid gas, hydrogen gas, aqueous gas,
alkoholic gas, &c.
The combinations of light, and its mode of acting upon different bodies,
is still less known. By the experiments of Mr Berthollet, it appears to
have great affinity with oxygen, is susceptible of combining with it,
and contributes alongst with caloric to change it into the state of gas.
Experiments upon vegetation give reason to believe that light combines
with certain parts of vegetables, and that the green of their leaves,
and the various colours of their flowers, is chiefly owing to this
combination. This much is certain, that plants which grow in darkness
are perfectly white, languid, and unhealthy, and that to make them
recover vigour, and to acquire their natural colours, the direct
influence of light is absolutely necessary. Somewhat similar takes place
even upon animals: Mankind degenerate to a certain degree when employed
in sedentary manufactures, or from living in crowded houses, or in the
narrow lanes of large cities; whereas they improve in their nature and
constitution in most of the country labours which are carried on in the
open air. Organization, sensation, spontaneous motion, and all the
operations of life, only exist at the surface of the earth, and in
places exposed to the influence of light. Without it nature itself would
be lifeless and inanimate. By means of light, the benevolence of the
Deity hath filled the surface of the earth with organization, sensation,
and intelligence. The fable of Promotheus might perhaps be considered as
giving a hint of this philosophical truth, which had even presented
itself to the knowledge of the ancients. I have intentionally avoided
any disquisitions relative to organized bodies in this work, for which
reason the phenomena of respiration, sanguification, and animal heat,
are not considered; but I hope, at some future time, to be able to
elucidate these curious subjects.
[Trancriber's note: The following table is presented in four sections to
comply with 75 character line limitation.]
TABLE of the binary Combinations of Oxygen with simple Substances
------------+----------------+-----------------------------------------+
|Names of |First degree of oxygenation. |
|the simple +--------------------+--------------------+
|substances. |New Names. |Ancient Names. |
+----------------+--------------------+--------------------+
{Caloric |Oxygen gas {Vital or |
{ | {dephlogisticated |
{ | {air |
{ | { |
{Hydrogen. |Water(A). | |
{ | | |
{Azote {Nitrous oxyd, or }Nitrous gas or air |
{ {base of nitrous gas } |
{ | | |
{Charcoal {Oxyd of charcoal, or}Unknown |
Combinations{ {carbonic oxyd } |
of oxygen { | | |
with {Sulphur |Oxyd of sulphur |Soft sulphur |
simple { | | |
non-metallic{Phosphorus |Oxyd of phosphorus {Residuum from the }
substances. { | {combustion of }
{ | {phosphorus }
{ | | |
{Muriatic radical}Muriatic oxyd |Unknown |
{ | | |
{Fluoric radical }Fluoric oxyd |Unknown |
{ | | |
{Boracic radical }Boracic oxyd |Unknown |
------------------------------------------------------------------------
{Antimony |Grey oxyd of |Grey calx of |
{ |antimony |antimony |
{ | | |
{Silver |Oxyd of silver |Calx of silver |
{ | | |
{Arsenic |Grey oxyd of arsenic|Grey calx of arsenic|
{ | | |
{Bismuth |Grey oxyd of bismuth|Grey calx of bismuth|
{ | | |
{ | | |
{Cobalt |Grey oxyd of cobalt |Grey calx of cobalt |
{ | | |
{Copper |Brown oxyd of copper|Brown calx of copper{
{ | | {
{Tin |Grey oxyd of tin |Grey calx of tin |
{ | | |
{Iron |Black oxyd of iron |Martial ethiops {
Combinations{ | | |
of oxygen {Manganese |Black oxyd of |Black calx of |
with the { |manganese |manganese |
simple { | | |
metallic {Mercury |Black oxyd of |Ethiops mineral(B) {
substances. { |mercury | {
{ | | |
{Molybdena |Oxyd of molybdena |Calx of molybdena |
{ | | |
{Nickel |Oxyd of nickel |Calx of nickel |
{ | | |
{Gold |Yellow oxyd of gold |Yellow calx of gold |
{ | | |
{Platina |Yellow oxyd of |Yellow calx of |
{ |platina |platina |
{ | | |
{Lead |Grey oxyd of lead |Grey calx of lead {
{ | | {
{Tungstein |Oxyd of Tungstein |Calx of Tungstein {
{ | | |
{Zinc |Grey oxyd of zinc |Grey calx of zinc |
------------+----------------+--------------------+--------------------+
------------+----------------+-----------------------------------------+
|Names of |Second degree of oxygenation. |
|the simple +--------------------+--------------------+
|substances. |New Names. |Ancient Names. |
+----------------+--------------------+--------------------+
{Caloric | | |
{ | | |
{Hydrogen. | | |
{ | | |
{Azote {Nitrous acid |Smoaking nitrous |
{ { |acid |
{ | | |
{Charcoal {Carbonous acid |Unknown |
Combinations{ { | |
of oxygen {Sulphur |Sulphurous acid |Sulphureous acid |
with simple { | | |
non-metallic{Phosphorus |Phosphorous acid {Volatile acid of }
substances. { | {phosphorus }
{ | | |
{Muriatic radical}Muriatous acid |Unknown |
{ | | |
{Fluoric radical }Fluorous acid |Unknown |
{ | | |
{Boracic radical }Boracous acid |Unknown |
------------------------------------------------------------------------
{Antimony |White oxyd of {White calx of }
{ |antimony {antimony }
{ | {diaphoretic antimony}
{ | | |
{Silver | | |
{ | | |
{Arsenic |White oxyd of |White calx of |
{ |arsenic |arsenic |
{ | | |
{Bismuth |White oxyd of |White calx of |
{ |bismuth |bismuth |
{ | | |
{Cobalt | | |
{ | | |
{Copper |Blue and green oxyds}Blue and green |
{ |of copper }calces of copper |
{ | | |
{Tin |White oxyd of tin {White calx of tin, }
{ | {or putty of tin }
{ | | |
{Iron |Yellow and red oxyds}Ochre and rust of |
{ |of iron }iron |
Combinations{ | | |
of oxygen {Manganese |White oxyd of |White calx of |
with the { |manganese |manganese |
simple { | | |
metallic {Mercury |Yellow and red oxyds{Turbith mineral, }
substances. { |of mercury {red precipitate, }
{ | {calcinated mercury, }
{ | {precipitate per se }
{ | | |
{Molybdena | | |
{ | | |
{Nickel | | |
{ | | |
{Gold |Red oxyd of gold {Red calx of gold, }
{ | {purple precipitate }
{ | |of cassius |
{ | | |
{Platina | | |
{ | | |
{Lead |Yellow and red oxyds}Massicot and minium |
{ |of lead } |
{ | | |
{Tungstein | | |
{ | | |
{Zinc |White oxyd of zinc {White calx of zinc, }
{ | {pompholix }
------------+----------------+--------------------+--------------------+
------------+----------------+-----------------------------------------+
|Names of |Third degree of oxygenation. |
|the simple +--------------------+--------------------+
|substances. |New Names. |Ancient Names. |
+----------------+--------------------+--------------------+
{Caloric | | |
{ | | |
{Hydrogen. | | |
{ | | |
{Azote {Nitric acid {Pale, or not }
{ { {smoaking nitrous }
{ | {acid |
{ | | |
Combinations{Charcoal {Carbonic acid |Fixed air |
of oxygen { | | |
with {Sulphur |Sulphuric acid |Vitriolic acid |
simple { | | |
non-metallic{Phosphorus |Phosphoric acid |Phosphoric acid |
substances. { | | |
{Muriatic radical}Muriatic acid |Marine acid |
{ | | |
{Fluoric radical }Fluoric acid |Unknown till lately |
{ | | |
{Boracic radical }Boracic acid {Homberg's sedative |
{ } {salt |
------------------------------------------------------------------------
{Antimony |Antimonic acid | |
{ | | |
{Silver |Argentic acid | |
{ | | |
{Arsenic |Arseniac acid |Acid of arsenic |
{ | | |
{Bismuth |Bismuthic acid | |
{ | | |
{Cobalt |Cobaltic acid | |
{ | | |
{Copper |Cupric acid | |
{ | | |
{Tin |Stannic acid | |
{ | | |
{Iron |Ferric acid | |
Combinations{ | | |
of oxygen {Manganese |Manganesic acid | |
with the { | | |
simple { | | |
metallic {Mercury |Mercuric acid | |
substances. { | | |
{Molybdena |Molybdic acid |Acid of molybdena {
{ | | |
{Nickel |Nickelic acid | |
{ | | |
{Gold |Auric acid | |
{ | | |
{Platina |Platinic acid | |
{ | | |
{Lead |Plumbic acid | |
{ | | |
{Tungstein |Tungstic acid |Acid of Tungstein {
{ | | |
{Zinc |Zincic acid | |
------------+----------------+--------------------+--------------------+
------------+----------------+------------------------------------------+
|Names of |Fourth degree of oxygenation. |
|the simple +---------------------+--------------------+
|substances. |New Names. |Ancient Names. |
+----------------+---------------------+--------------------+
{Caloric | | |
{ | | |
{Hydrogen. | | |
{ | | |
{Azote {Oxygenated nitric |Unknown |
{ {acid | |
{ | | |
{Charcoal {Oxygenated carbonic |Unknown |
Combinations{ {acid | |
of oxygen { | | |
with {Sulphur |Oxygenated sulphuric |Unknown |
simple { |acid | |
non-metallic{Phosphorus |Oxygenated phosphoric|Unknown |
substances. { |acid | |
{ | | |
{Muriatic radical}Oxygenated muriatic {Dephlogisticated |
{ |acid |marine acid |
{ | | |
{Fluoric radical } | |
{ | | |
{Boracic radical } | |
{ } | |
------------------------------------------------------------------------
{Antimony | | |
{ | | |
{Silver | | |
{ | | |
{Arsenic |Oxygenated arseniac |Unknown |
{ |acid | |
{ | | |
{Bismuth | | |
{ | | |
{Cobalt | | |
{ | | |
{Copper | | |
{ | | |
{Tin | | |
{ | | |
{Iron | | |
{ | | |
Combinations{ | | |
of oxygen {Manganese | | |
with the { | | |
simple { | | |
metallic {Mercury | | |
substances. { | | |
{Molybdena |Oxygenated molybdic |Unknown |
{ |acid | |
{Nickel | | |
{ | | |
{Gold | | |
{ | | |
{Platina | | |
{ | | |
{Lead | | |
{ | | |
{Tungstein |Oxygenated Tungstic }Unknown |
{ |acid | |
{ | | |
{Zinc | | |
------------+----------------+---------------------+--------------------+
[Note A: Only one degree of oxygenation of hydrogen is hitherto
known.--A.]
[Note B: Ethiops mineral is the sulphuret of mercury; this should have
been called black precipitate of mercury.--E.]
SECT. IV.--_Observations upon the Combinations of Oxygen with the simple
Substances._
Oxygen forms almost a third of the mass of our atmosphere, and is
consequently one of the most plentiful substances in nature. All the
animals and vegetables live and grow in this immense magazine of oxygen
gas, and from it we procure the greatest part of what we employ in
experiments. So great is the reciprocal affinity between this element
and other substances, that we cannot procure it disengaged from all
combination. In the atmosphere it is united with caloric, in the state
of oxygen gas, and this again is mixed with about two thirds of its
weight of azotic gas.
Several conditions are requisite to enable a body to become oxygenated,
or to permit oxygen to enter into combination with it. In the first
place, it is necessary that the particles of the body to be oxygenated
shall have less reciprocal attraction with each other than they have for
the oxygen, which otherwise cannot possibly combine with them. Nature,
in this case, may be assisted by art, as we have it in our power to
diminish the attraction of the particles of bodies almost at will by
heating them, or, in other words, by introducing caloric into the
interstices between their particles; and, as the attraction of these
particles for each other is diminished in the inverse ratio of their
distance, it is evident that there must be a certain point of distance
of particles when the affinity they possess with each other becomes less
than that they have for oxygen, and at which oxygenation must
necessarily take place if oxygen be present.
We can readily conceive that the degree of heat at which this phenomenon
begins must be different in different bodies. Hence, on purpose to
oxygenate most bodies, especially the greater part of the simple
substances, it is only necessary to expose them to the influence of the
air of the atmosphere in a convenient degree of temperature. With
respect to lead, mercury, and tin, this needs be but little higher than
the medium temperature of the earth; but it requires a more considerable
degree of heat to oxygenate iron, copper, &c. by the dry way, or when
this operation is not assisted by moisture. Sometimes oxygenation takes
place with great rapidity, and is accompanied by great sensible heat,
light, and flame; such is the combustion of phosphorus in atmospheric
air, and of iron in oxygen gas. That of sulphur is less rapid; and the
oxygenation of lead, tin, and most of the metals, takes place vastly
slower, and consequently the disengagement of caloric, and more
especially of light, is hardly sensible.
Some substances have so strong an affinity with oxygen, and combine with
it in such low degrees of temperature, that we cannot procure them in
their unoxygenated state; such is the muriatic acid, which has not
hitherto been decomposed by art, perhaps even not by nature, and which
consequently has only been found in the state of acid. It is probable
that many other substances of the mineral kingdom are necessarily
oxygenated in the common temperature of the atmosphere, and that being
already saturated with oxygen, prevents their farther action upon that
element.
There are other means of oxygenating simple substances besides exposure
to air in a certain degree of temperature, such as by placing them in
contact with metals combined with oxygen, and which have little affinity
with that element. The red oxyd of mercury is one of the best substances
for this purpose, especially with bodies which do not combine with that
metal. In this oxyd the oxygen is united with very little force to the
metal, and can be driven out by a degree of heat only sufficient to make
glass red hot; wherefore such bodies as are capable of uniting with
oxygen are readily oxygenated, by means of being mixed with red oxyd of
mercury, and moderately heated. The same effect may be, to a certain
degree, produced by means of the black oxyd of manganese, the red oxyd
of lead, the oxyds of silver, and by most of the metallic oxyds, if we
only take care to choose such as have less affinity with oxygen than the
bodies they are meant to oxygenate. All the metallic reductions and
revivifications belong to this class of operations, being nothing more
than oxygenations of charcoal, by means of the several metallic oxyds.
The charcoal combines with the oxygen and with caloric, and escapes in
form of carbonic acid gas, while the metal remains pure and revivified,
or deprived of the oxygen which before combined with it in the form of
oxyd.
All combustible substances may likewise be oxygenated by means of mixing
them with nitrat of potash or of soda, or with oxygenated muriat of
potash, and subjecting the mixture to a certain degree of heat; the
oxygen, in this case, quits the nitrat or the muriat, and combines with
the combustible body. This species of oxygenation requires to be
performed with extreme caution, and only with very small quantities;
because, as the oxygen enters into the composition of nitrats, and more
especially of oxygenated muriats, combined with almost as much caloric
as is necessary for converting it into oxygen gas, this immense quantity
of caloric becomes suddenly free the instant of the combination of the
oxygen with the combustible body, and produces such violent explosions
as are perfectly irresistible.
By the humid way we can oxygenate most combustible bodies, and convert
most of the oxyds of the three kingdoms of nature into acids. For this
purpose we chiefly employ the nitric acid, which has a very slight hold
of oxygen, and quits it readily to a great number of bodies by the
assistance of a gentle heat. The oxygenated muriatic acid may be used
for several operations of this kind, but not in them all.
I give the name of _binary_ to the combinations of oxygen with the
simple substances, because in these only two elements are combined. When
three substances are united in one combination I call it _ternary_, and
_quaternary_ when the combination consists of four substances united.
TABLE _of the combinations of Oxygen with the compound radicals._
_Names of the radicals._ _Names of the resulting acids._
_New nomenclature._ _Old nomenclature._
Nitro muriatic} Nitro muriatic acid Aqua regia.
radical }
(A)
Tartaric Tartarous acid Unknown till lately.
Malic Malic acid Ditto.
Citric Citric acid Acid of lemons.
Pyro-lignous Pyro-lignous acid Empyreumatic acid of wood.
Pyro-mucous Pyro-mucous acid Empyr. acid of sugar.
Pyro-tartarous Pyro-tartarous acid Empyr. acid of tartar.
Oxalic Oxalic acid Acid of sorel.
Acetic {Acetous acid Vinegar, or acid of vinegar.
{Acetic acid Radical vinegar.
Succinic Succinic acid Volatile salt of amber.
Benzoic Benzotic acid Flowers of benzoin.
Camphoric Camphoric acid Unknown till lately.
Gallic Gallic acid {The astringent principle
{of vegetables.
(B)
Lactic Lactic acid Acid of sour whey.
Saccholactic Saccholactic acid Unknown till lately.
Formic Formic acid Acid of ants.
Bombic Bombic acid Unknown till lately.
Sebacic Sebacic acid Ditto.
Lithic Lithic acid Urinary calculus.
Prussic Prussic acid Colouring matter of Prussian blue.
[Note A: These radicals by a first degree of oxygenation form vegetable
oxyds, as sugar, starch, mucus, &c.--A.]
[Note B: These radicals by a first degree of oxygenation form the animal
oxyds, as lymph, red part of the blood, animal secretions, &c.--A.]
SECT. V.--_Observations upon the Combinations of Oxygen with the
Compound Radicals._
I published a new theory of the nature and formation of acids in the
Memoirs of the Academy for 1776, p. 671. and 1778, p. 535. in which I
concluded, that the number of acids must be greatly larger than was till
then supposed. Since that time, a new field of inquiry has been opened
to chemists; and, instead of five or six acids which were then known,
near thirty new acids have been discovered, by which means the number of
known neutral salts have been increased in the same proportion. The
nature of the acidifiable bases, or radicals of the acids, and the
degrees of oxygenation they are susceptible of, still remain to be
inquired into. I have already shown, that almost all the oxydable and
acidifiable radicals from the mineral kingdom are simple, and that, on
the contrary, there hardly exists any radical in the vegetable, and more
especially in the animal kingdom, but is composed of at least two
substances, hydrogen and charcoal, and that azote and phosphorus are
frequently united to these, by which we have compound radicals of two,
three, and four bases or simple elements united.
From these observations, it appears that the vegetable and animal oxyds
and acids may differ from each other in three several ways: 1st,
According to the number of simple acidifiable elements of which their
radicals are composed: 2dly, According to the proportions in which these
are combined together: And, 3dly, According to their different degrees
of oxygenation: Which circumstances are more than sufficient to explain
the great variety which nature produces in these substances. It is not
at all surprising, after this, that most of the vegetable acids are
convertible into each other, nothing more being requisite than to change
the proportions of the hydrogen and charcoal in their composition, and
to oxygenate them in a greater or lesser degree. This has been done by
Mr Crell in some very ingenious experiments, which have been verified
and extended by Mr Hassenfratz. From these it appears, that charcoal and
hydrogen, by a first oxygenation, produce tartarous acid, oxalic acid by
a second degree, and acetous or acetic acid by a third, or higher
oxygenation; only, that charcoal seems to exist in a rather smaller
proportion in the acetous and acetic acids. The citric and malic acids
differ little from the preceding acids.
Ought we then to conclude that the oils are the radicals of the
vegetable and animal acids? I have already expressed my doubts upon
this subject: 1st, Although the oils appear to be formed of nothing but
hydrogen and charcoal, we do not know if these are in the precise
proportion necessary for constituting the radicals of the acids: 2dly,
Since oxygen enters into the composition of these acids equally with
hydrogen and charcoal, there is no more reason for supposing them to be
composed of oil rather than of water or of carbonic acid. It is true
that they contain the materials necessary for all these combinations,
but then these do not take place in the common temperature of the
atmosphere; all the three elements remain combined in a state of
equilibrium, which is readily destroyed by a temperature only a little
above that of boiling water[39].
TABLE _of the Binary Combinations of Azote with the Simple Substances._
_Simple Substances._ _Results of the Combinations._
_New Nomenclature._ _Old Nomenclature._
Caloric Azotic gas Phlogisticated air, or Mephitis.
Hydrogen Ammoniac Volatile alkali.
{Nitrous oxyd Base of Nitrous gas.
{Nitrous acid Smoaking nitrous acid.
Oxygen {Nitric acid Pale nitrous acid.
{Oxygenated nitric acid Unknown.
{This combination is hitherto unknown; should it
{ever be discovered, it will be called, according to
Charcoal {the principles of our nomenclature, Azuret of
{Charcoal. Charcoal dissolves in azotic gas, and
{forms carbonated azotic gas.
Phosphorus. Azuret of phosphorus. Still unknown.
{Azuret of sulphur. Still unknown. We know
Sulphur {that sulphur dissolves in azotic gas, forming
{sulphurated azotic gas.
{Azote combines with charcoal and hydrogen, and
Compound {sometimes with phosphorus, in the compound
radicals {oxydable and acidifiable bases, and is generally
{contained in the radicals of the animal acids.
{Such combinations are hitherto unknown; if ever
Metallic {discovered, they will form metallic azurets, as
substances {azuret of gold, of silver, &c.
Lime {
Magnesia {
Barytes {Entirely unknown. If ever discovered, they will
Argill {form azuret of lime, azuret of magnesia, &c.
Potash {
Soda {
SECT. VI.--_Observations upon the Combinations of Azote with the Simple
Substances._
Azote is one of the most abundant elements; combined with caloric it
forms azotic gas, or mephitis, which composes nearly two thirds of the
atmosphere. This element is always in the state of gas in the ordinary
pressure and temperature, and no degree of compression or of cold has
been hitherto capable of reducing it either to a solid or liquid form.
This is likewise one of the essential constituent elements of animal
bodies, in which it is combined with charcoal and hydrogen, and
sometimes with phosphorus; these are united together by a certain
portion of oxygen, by which they are formed into oxyds or acids
according to the degree of oxygenation. Hence the animal substances may
be varied, in the same way with vegetables, in three different manners:
1st, According to the number of elements which enter into the
composition of the base or radical: 2dly, According to the proportions
of these elements: 3dly, According to the degree of oxygenation.
When combined with oxygen, azote forms the nitrous and nitric oxyds and
acids; when with hydrogen, ammoniac is produced. Its combinations with
the other simple elements are very little known; to these we give the
name of Azurets, preserving the termination in _uret_ for all
nonoxygenated compounds. It is extremely probable that all the alkaline
substances may hereafter be found to belong to this genus of azurets.
The azotic gas may be procured from atmospheric air, by absorbing the
oxygen gas which is mixed with it by means of a solution of sulphuret of
potash, or sulphuret of lime. It requires twelve or fifteen days to
complete this process, during which time the surface in contact must be
frequently renewed by agitation, and by breaking the pellicle which
forms on the top of the solution. It may likewise be procured by
dissolving animal substances in dilute nitric acid very little heated.
In this operation, the azote is disengaged in form of gas, which we
receive under bell glasses filled with water in the pneumato-chemical
apparatus. We may procure this gas by deflagrating nitre with charcoal,
or any other combustible substance; when with charcoal, the azotic gas
is mixed with carbonic acid gas, which may be absorbed by a solution of
caustic alkali, or by lime water, after which the azotic gas remains
pure. We can procure it in a fourth manner from combinations of ammoniac
with metallic oxyds, as pointed out by Mr de Fourcroy: The hydrogen of
the ammoniac combines with the oxygen of the oxyd, and forms water,
whilst the azote being left free escapes in form of gas.
The combinations of azote were but lately discovered: Mr Cavendish first
observed it in nitrous gas and acid, and Mr Berthollet in ammoniac and
the prussic acid. As no evidence of its decomposition has hitherto
appeared, we are fully entitled to consider azote as a simple elementary
substance.
TABLE _of the Binary Combinations of Hydrogen with Simple Substances._
_Simple_ _Resulting Compounds._
_Substances._ _New Nomenclature._ _Old Names._
Caloric Hydrogen gas Inflammable air.
Azote Ammoniac Volatile Alkali.
Oxygen Water Water.
Sulphur {Hydruret of sulphur, or }
{sulphuret of hydrogen } Hitherto unknown (A).
Phosphorus {Hydruret of phosphorus, or }
{phosphuret of hydrogen }
Charcoal {Hydro-carbonous, or } Not known till lately.
{carbono-hydrous radicals(B)}
Metallic {Metallic hydrurets(C), as } Hitherto unknown.
substances, {hydruret of iron, &c. }
as iron, &c. { }
[Note A: These combinations take place in the state of gas, and form,
respectively, sulphurated and phosphorated oxygen gas--A.]
[Note B: This combination of hydrogen with charcoal includes the fixed
and volatile oils, and forms the radicals of a considerable part of the
vegetable and animal oxyds and acids. When it takes place in the state
of gas it forms carbonated hydrogen gas.--A.]
[Note C: None of these combinations are known, and it is probable that
they cannot exist, at least in the usual temperature of the atmosphere,
owing to the great affinity of hydrogen for caloric.--A.]
SECT. VII.--_Observations upon Hydrogen, and its Combinations with
Simple Substances._
Hydrogen, as its name expresses, is one of the constituent elements of
water, of which it forms fifteen hundredth parts by weight, combined
with eighty-five hundredth parts of oxygen. This substance, the
properties and even existence of which was unknown till lately, is very
plentifully distributed in nature, and acts a very considerable part in
the processes of the animal and vegetable kingdoms. As it possesses so
great affinity with caloric as only to exist in the state of gas, it is
consequently impossible to procure it in the concrete or liquid state,
independent of combination.
To procure hydrogen, or rather hydrogen gas, we have only to subject
water to the action of a substance with which oxygen has greater
affinity than it has to hydrogen; by this means the hydrogen is set
free, and, by uniting with caloric, assumes the form of hydrogen gas.
Red hot iron is usually employed for this purpose: The iron, during the
process, becomes oxydated, and is changed into a substance resembling
the iron ore from the island of Elba. In this state of oxyd it is much
less attractible by the magnet, and dissolves in acids without
effervescence.
Charcoal, in a red heat, has the same power of decomposing water, by
attracting the oxygen from its combination with hydrogen. In this
process carbonic acid gas is formed, and mixes with the hydrogen gas,
but is easily separated by means of water or alkalies, which absorb the
carbonic acid, and leave the hydrogen gas pure. We may likewise obtain
hydrogen gas by dissolving iron or zinc in dilute sulphuric acid. These
two metals decompose water very slowly, and with great difficulty, when
alone, but do it with great ease and rapidity when assisted by sulphuric
acid; the hydrogen unites with caloric during the process, and is
disengaged in form of hydrogen gas, while the oxygen of the water unites
with the metal in the form of oxyd, which is immediately dissolved in
the acid, forming a sulphat of iron or of zinc.
Some very distinguished chemists consider hydrogen as the _phlogiston_
of Stahl; and as that celebrated chemist admitted the existence of
phlogiston in sulphur, charcoal, metals, &c. they are of course obliged
to suppose that hydrogen exists in all these substances, though they
cannot prove their supposition; even if they could, it would not avail
much, since this disengagement of hydrogen is quite insufficient to
explain the phenomena of calcination and combustion. We must always
recur to the examination of this question, "Are the heat and light,
which are disengaged during the different species of combustion,
furnished by the burning body, or by the oxygen which combines in all
these operations?" And certainly the supposition of hydrogen being
disengaged throws no light whatever upon this question. Besides, it
belongs to those who make suppositions to prove them; and, doubtless, a
doctrine which without any supposition explains the phenomena as well,
and as naturally, as theirs does by supposition, has at least the
advantage of greater simplicity[40].
TABLE _of the Binary Combinations of Sulphur with Simple Substances._
_Simple_ _Resulting Compounds._
_Substances._ _New Nomenclature._ _Old Nomenclature._
Caloric Sulphuric gas
{ Oxyd of sulphur Soft sulphur.
Oxygen { Sulphurous acid Sulphureous acid.
{ Sulphuric acid Vitriolic acid.
Hydrogen Sulphuret of hydrogen }
Azote azote } Unknown Combinations.
Phosphorus phosphorus }
Charcoal charcoal }
Antimony antimony Crude antimony.
Silver silver
Arsenic arsenic Orpiment, realgar.
Bismuth bismuth
Cobalt cobalt
Copper copper Copper pyrites.
Tin tin
Iron iron Iron pyrites.
Manganese manganese
Mercury mercury Ethiops mineral, cinnabar.
Molybdena molybdena
Nickel nickel
Gold gold
Platina platina
Lead lead Galena.
Tungstein tungstein
Zinc zinc Blende.
{ Alkaline liver of sulphur
Potash potash { with fixed vegetable alkali.
{ Alkaline liver of sulphur
Soda soda { with fixed mineral
{ alkali.
{ Volatile liver of sulphur,
Ammoniac ammoniac { smoaking liquor
{ of Boyle.
Lime lime Calcareous liver of sulphur.
Magnesia magnesia Magnesian liver of sulphur.
Barytes barytes Barytic liver of sulphur.
Argill argill Yet unknown.
SECT. VIII.--_Observations on Sulphur, and its Combinations._
Sulphur is a combustible substance, having a very great tendency to
combination; it is naturally in a solid state in the ordinary
temperature, and requires a heat somewhat higher than boiling water to
make it liquify. Sulphur is formed by nature in a considerable degree of
purity in the neighbourhood of volcanos; we find it likewise, chiefly in
the state of sulphuric acid, combined with argill in aluminous schistus,
with lime in gypsum, &c. From these combinations it may be procured in
the state of sulphur, by carrying off its oxygen by means of charcoal in
a red heat; carbonic acid is formed, and escapes in the state of gas;
the sulphur remains combined with the clay, lime, &c. in the state of
sulphuret, which is decomposed by acids; the acid unites with the earth
into a neutral salt, and the sulphur is precipitated.
TABLE _of the Binary Combinations of Phosphorus with the Simple
Substances._
_Simple Substances._ _Resulting Compounds._
Caloric Phosphoric gas.
{ Oxyd of phosphorus.
Oxygen { Phosphorous acid.
{ Phosphoric acid.
Hydrogen Phosphuret of hydrogen.
Azote Phosphuret of azote.
Sulphur Phosphuret of Sulphur.
Charcoal Phosphuret of charcoal.
Metallic substances Phosphuret of metals(A).
Potash }
Soda }
Ammoniac } Phosphuret of Potash,
Lime } Soda, &c.(B)
Barytes }
Magnesia }
Argill }
[Note A: Of all these combinations of phosphorus with metals, that with
iron only is hitherto known, forming the substance formerly called
Siderite; neither is it yet ascertained whether, in this combination,
the phosphorus be oxygenated or not.--A.]
[Note B: These combinations of phosphorus with the alkalies and earths
are not yet known; and, from the experiments of Mr Gengembre, they
appear to be impossible--A.]
SECT. IX.--_Observations upon Phosphorus, and its Combinations._
Phosphorus is a simple combustible substance, which was unknown to
chemists till 1667, when it was discovered by Brandt, who kept the
process secret; soon after Kunkel found out Brandt's method of
preparation, and made it public. It has been ever since known by the
name of Kunkel's phosphorus. It was for a long time procured only from
urine; and, though Homberg gave an account of the process in the Memoirs
of the Academy for 1692, all the philosophers of Europe were supplied
with it from England. It was first made in France in 1737, before a
committee of the Academy at the Royal Garden. At present it is procured
in a more commodious and more oeconomical manner from animal bones,
which are real calcareous phosphats, according to the process of Messrs
Gahn, Scheele, Rouelle, &c. The bones of adult animals being calcined to
whiteness, are pounded, and passed through a fine silk sieve; pour upon
the fine powder a quantity of dilute sulphuric acid, less than is
sufficient for dissolving the whole. This acid unites with the
calcareous earth of the bones into a sulphat of lime, and the phosphoric
acid remains free in the liquor. The liquid is decanted off, and the
residuum washed with boiling water; this water which has been used to
wash out the adhering acid is joined with what was before decanted off,
and the whole is gradually evaporated; the dissolved sulphat of lime
cristallizes in form of silky threads, which are removed, and by
continuing the evaporation we procure the phosphoric acid under the
appearance of a white pellucid glass. When this is powdered, and mixed
with one third its weight of charcoal, we procure very pure phosphorus
by sublimation. The phosphoric acid, as procured by the above process,
is never so pure as that obtained by oxygenating pure phosphorus either
by combustion or by means of nitric acid; wherefore this latter should
always be employed in experiments of research.
Phosphorus is found in almost all animal substances, and in some plants
which give a kind of animal analysis. In all these it is usually
combined with charcoal, hydrogen, and azote, forming very compound
radicals, which are, for the most part, in the state of oxyds by a first
degree of union with oxygen. The discovery of Mr Hassenfratz, of
phosphorus being contained in charcoal, gives reason to suspect that it
is more common in the vegetable kingdom than has generally been
supposed: It is certain, that, by proper processes, it may be procured
from every individual of some of the families of plants.
As no experiment has hitherto given reason to suspect that phosphorus is
a compound body, I have arranged it with the simple or elementary
substances. It takes fire at the temperature of 32° (104°) of the
thermometer.
TABLE _of the Binary Combinations of Charcoal._
_Simple_
_Substances._ _Resulting Compounds._
{ Oxyd of charcoal Unknown.
Oxygen { Carbonic acid Fixed air, chalky acid.
Sulphur Carburet of sulphur }
Phosphorus Carburet of phosphorus } Unknown.
Azote Carburet of azote }
{ Carbono-hydrous radical
Hydrogen { Fixed and volatile oils
{ Of these only the carburets of
Metallic substances Carburets of metals { iron and zinc are known, and
{ were formerly called Plumbago.
Alkalies and earths Carburet of potash, &c. Unknown.
SECT. X.--_Observations upon Charcoal, and its Combinations with Simple
Substances._
As charcoal has not been hitherto decomposed, it must, in the present
state of our knowledge, be considered as a simple substance. By modern
experiments it appears to exist ready formed in vegetables; and I have
already remarked, that, in these, it is combined with hydrogen,
sometimes with azote and phosphorus, forming compound radicals, which
may be changed into oxyds or acids according to their degree of
oxygenation.
To obtain the charcoal contained in vegetable or animal substances, we
subject them to the action of fire, at first moderate, and afterwards
very strong, on purpose to drive off the last portions of water, which
adhere very obstinately to the charcoal. For chemical purposes, this is
usually done in retorts of stone-ware or porcellain, into which the
wood, or other matter, is introduced, and then placed in a reverberatory
furnace, raised gradually to its greatest heat: The heat volatilizes, or
changes into gas, all the parts of the body susceptible of combining
with caloric into that form, and the charcoal, being more fixed in its
nature, remains in the retort combined with a little earth and some
fixed salts.
In the business of charring wood, this is done by a less expensive
process. The wood is disposed in heaps, and covered with earth, so as to
prevent the access of any more air than is absolutely necessary for
supporting the fire, which is kept up till all the water and oil is
driven off, after which the fire is extinguished by shutting up all the
air-holes.
We may analyse charcoal either by combustion in air, or rather in oxygen
gas, or by means of nitric acid. In either case we convert it into
carbonic acid, and sometimes a little potash and some neutral salts
remain. This analysis has hitherto been but little attended to by
chemists; and we are not even certain if potash exists in charcoal
before combustion, or whether it be formed by means of some unknown
combination during that process.
SECT. XI.--_Observations upon the Muriatic, Fluoric, and Boracic
Radicals, and their Combinations._
As the combinations of these substances, either with each other, or with
the other combustible bodies, are hitherto entirely unknown, we have
not attempted to form any table for their nomenclature. We only know
that these radicals are susceptible of oxygenation, and of forming the
muriatic, fluoric, and boracic acids, and that in the acid state they
enter into a number of combinations, to be afterwards detailed.
Chemistry has hitherto been unable to disoxygenate any of them, so as to
produce them in a simple state. For this purpose, some substance must be
employed to which oxygen has a stronger affinity than to their radicals,
either by means of single affinity, or by double elective attraction.
All that is known relative to the origin of the radicals of these acids
will be mentioned in the sections set apart for considering their
combinations with the salifiable bases.
SECT. XII.--_Observations upon the Combinations of Metals with each
other._
Before closing our account of the simple or elementary substances, it
might be supposed necessary to give a table of alloys or combinations of
metals with each other; but, as such a table would be both exceedingly
voluminous and very unsatisfactory, without going into a series of
experiments not yet attempted, I have thought it adviseable to omit it
altogether. All that is necessary to be mentioned is, that these alloys
should be named according to the metal in largest proportion in the
mixture or combination; thus the term _alloy of gold and silver_, or
gold alloyed with silver, indicates that gold is the predominating
metal.
Metallic alloys, like all other combinations, have a point of
saturation. It would even appear, from the experiments of Mr de la
Briche, that they have two perfectly distinct degrees of saturation.
TABLE _of the Combinations of Azote in the state of Nitrous Acid with
the Salifiable Bases, arranged according to the affinities of these
Bases with the Acid_.
_Names of the bases._ _Names of the neutral salts._
_New nomenclature._ _Notes._
Barytes Nitrite of barytes. {
Potash potash. { These salts are only
Soda soda. { known of late, and
Lime lime. { have received no particular
Magnesia magnesia. { name in the old
Ammoniac ammoniac. { nomenclature.
Argill argill. {
{ As metals dissolve both in nitrous and
Oxyd of zinc zinc. { nitric acids, metallic salts must of
iron iron. { consequence be formed having
manganese manganese. { different degrees of oxygenation.
cobalt cobalt. { Those wherein the metal is
nickel nickel. { least oxygenated must be
lead lead. { called Nitrites, when more so,
tin tin. { Nitrats; but the limits of this
copper copper. { distinction are difficultly
bismuth bismuth. { ascertainable. The older
antimony antimony. { chemists were not acquainted
arsenic arsenic. { with any of these salts.
mercury mercury. {
silver { It is extremely probable that gold, silver
gold { and platina only form nitrats, and cannot subsist
platina { in the state of nitrites.
TABLE _of the Combinations of Azote, completely saturated with Oxygen,
in the state of Nitric Acid, with the Salifiable Bases, in the order of
the affinity with the Acid_.
_Bases._ _Names of the resulting neutral salts._
_New nomenclature._ _Old nomenclature._
Barytes Nitrat of barytes Nitre, with a base of heavy earth.
Potash potash Nitre, saltpetre. Nitre with base of potash.
Soda soda { Quadrangular nitre. Nitre with base of
{ mineral alkali.
{ Calcareous nitre. Nitre with
Lime lime { calcareous base. Mother water
{ of nitre, or saltpetre.
Magnesia magnesia Magnesian nitre. Nitre with base of magnesia.
Ammoniac ammoniac Ammoniacal nitre.
{ Nitrous alum. Argillaceous nitre. Nitre
Argill argill { with base of earth of alum.
Oxyd of zinc zinc Nitre of zinc.
iron iron Nitre of iron. Martial nitre. Nitrated iron.
manganese manganese Nitre of manganese.
cobalt cobalt Nitre of cobalt.
nickel nickel Nitre of nickel.
lead lead Saturnine nitre. Nitre of lead.
tin tin Nitre of tin.
copper copper Nitre of copper or of Venus.
bismuth bismuth Nitre of bismuth.
antimony antimony Nitre of antimony.
arsenic arsenic Arsenical nitre.
mercury mercury Mercurial nitre.
silver silver Nitre of silver or luna. Lunar caustic.
gold gold Nitre of gold.
platina platina Nitre of platina.
SECT. XIII.--_Observations upon the Nitrous and Nitric Acids, and their
Combinations._
The nitrous and nitric acids are procured from a neutral salt long known
in the arts under the name of _saltpetre_. This salt is extracted by
lixiviation from the rubbish of old buildings, from the earth of
cellars, stables, or barns, and in general of all inhabited places. In
these earths the nitric acid is usually combined with lime and magnesia,
sometimes with potash, and rarely with argill. As all these salts,
excepting the nitrat of potash, attract the moisture of the air, and
consequently would be difficultly preserved, advantage is taken, in the
manufactures of saltpetre and the royal refining house, of the greater
affinity of the nitric acid to potash than these other bases, by which
means the lime, magnesia, and argill, are precipitated, and all these
nitrats are reduced to the nitrat of potash or saltpetre[41].
The nitric acid is procured from this salt by distillation, from three
parts of pure saltpetre decomposed by one part of concentrated
sulphuric acid, in a retort with Woulfe's apparatus, (Pl. IV. fig. 1.)
having its bottles half filled with water, and all its joints carefully
luted. The nitrous acid passes over in form of red vapours surcharged
with nitrous gas, or, in other words, not saturated with oxygen. Part of
the acid condenses in the recipient in form of a dark orange red liquid,
while the rest combines with the water in the bottles. During the
distillation, a large quantity of oxygen gas escapes, owing to the
greater affinity of oxygen to caloric, in a high temperature, than to
nitrous acid, though in the usual temperature of the atmosphere this
affinity is reversed. It is from the disengagement of oxygen that the
nitric acid of the neutral salt is in this operation converted into
nitrous acid. It is brought back to the state of nitric acid by heating
over a gentle fire, which drives off the superabundant nitrous gas, and
leaves the nitric acid much diluted with water.
Nitric acid is procurable in a more concentrated state, and with much
less loss, by mixing very dry clay with saltpetre. This mixture is put
into an earthern retort, and distilled with a strong fire. The clay
combines with the potash, for which it has great affinity, and the
nitric acid passes over, slightly impregnated with nitrous gas. This is
easily disengaged by heating the acid gently in a retort, a small
quantity of nitrous gas passes over into the recipient, and very pure
concentrated nitric acid remains in the retort.
We have already seen that azote is the nitric radical. If to 20-1/2
parts, by weight, of azote 43-1/2 parts of oxygen be added, 64 parts of
nitrous gas are formed; and, if to this we join 36 additional parts of
oxygen, 100 parts of nitric acid result from the combination.
Intermediate quantities of oxygen between these two extremes of
oxygenation produce different species of nitrous acid, or, in other
words, nitric acid less or more impregnated with nitrous gas. I
ascertained the above proportions by means of decomposition; and, though
I cannot answer for their absolute accuracy, they cannot be far removed
from truth. Mr Cavendish, who first showed by synthetic experiments that
azote is the base of nitric acid, gives the proportions of azote a
little larger than I have done; but, as it is not improbable that he
produced the nitrous acid and not the nitric, that circumstance explains
in some degree the difference in the results of our experiments.
As, in all experiments of a philosophical nature, the utmost possible
degree of accuracy is required, we must procure the nitric acid for
experimental purposes, from nitre which has been previously purified
from all foreign matter. If, after distillation, any sulphuric acid is
suspected in the nitric acid, it is easily separated by dropping in a
little nitrat of barytes, so long as any precipitation takes place; the
sulphuric acid, from its greater affinity, attracts the barytes, and
forms with it an insoluble neutral salt, which falls to the bottom. It
may be purified in the same manner from muriatic acid, by dropping in a
little nitrat of silver so long as any precipitation of muriat of silver
is produced. When these two precipitations are finished, distill off
about seven-eighths of the acid by a gentle heat, and what comes over is
in the most perfect degree of purity.
The nitric acid is one of the most prone to combination, and is at the
same time very easily decomposed. Almost all the simple substances, with
the exception of gold, silver, and platina, rob it less or more of its
oxygen; some of them even decompose it altogether. It was very anciently
known, and its combinations have been more studied by chemists than
those of any other acid. These combinations were named _nitres_ by
Messrs Macquer and Beaumé; but we have changed their names to nitrats
and nitrites, according as they are formed by nitric or by nitrous acid,
and have added the specific name of each particular base, to distinguish
the several combinations from each other.
TABLE _of the Combinations of Sulphuric Acid with the Salifiable Bases,
in the order of affinity._
_Names of the bases._ _Resulting compounds._
_New nomenclature._ _Old nomenclature._
Barytes Sulphat of barytes Heavy spar. Vitriol of heavy earth.
Potash potash {Vitriolated tartar. Sal
{ de duobus. Arcanum
{ duplicatam.
Soda soda Glauber's salt.
Lime lime Selenite, gypsum, calcareous vitriol.
Magnesia magnesia Epsom salt, sedlitz salt, magnesian vitriol.
Ammoniac ammoniac Glauber's secret sal ammoniac.
Argill argill Alum.
Oxyd of zinc zinc {White vitriol, goslar
{ vitriol, white coperas,
{ vitriol of zinc.
iron iron {Green coperas, green
{ vitriol, martial vitriol,
{ vitriol of iron.
manganese manganese Vitriol of manganese.
cobalt cobalt Vitriol of cobalt.
nickel nickel Vitriol of nickel.
lead lead Vitriol of lead.
tin tin Vitriol of tin.
copper copper {Blue coperas, blue vitriol,
{ Roman vitriol,
{ vitriol of copper.
bismuth bismuth Vitriol of bismuth.
antimony antimony Vitriol of antimony.
arsenic arsenic Vitriol of arsenic.
mercury mercury Vitriol of mercury.
silver silver Vitriol of silver.
gold gold Vitriol of gold.
platina platina Vitriol of platina.
SECT. XIV.--_Observations upon Sulphuric Acid and its Combinations._
For a long time this acid was procured by distillation from sulphat of
iron, in which sulphuric acid and oxyd of iron are combined, according
to the process described by Basil Valentine in the fifteenth century;
but, in modern times, it is procured more oeconomically by the
combustion of sulphur in proper vessels. Both to facilitate the
combustion, and to assist the oxygenation of the sulphur, a little
powdered saltpetre, nitrat of potash, is mixed with it; the nitre is
decomposed, and gives out its oxygen to the sulphur, which contributes
to its conversion into acid. Notwithstanding this addition, the sulphur
will only continue to burn in close vessels for a limited time; the
combination ceases, because the oxygen is exhausted, and the air of the
vessels reduced almost to pure azotic gas, and because the acid itself
remains long in the state of vapour, and hinders the progress of
combustion.
In the manufactories for making sulphuric acid in the large way, the
mixture of nitre and sulphur is burnt in large close built chambers
lined with lead, having a little water at the bottom for facilitating
the condensation of the vapours. Afterwards, by distillation in large
retorts with a gentle heat, the water passes over, slightly impregnated
with acid, and the sulphuric acid remains behind in a concentrated
state. It is then pellucid, without any flavour, and nearly double the
weight of an equal bulk of water. This process would be greatly
facilitated, and the combustion much prolonged, by introducing fresh air
into the chambers, by means of several pairs of bellows directed towards
the flame of the sulphur, and by allowing the nitrous gas to escape
through long serpentine canals, in contact with water, to absorb any
sulphuric or sulphurous acid gas it might contain.
By one experiment, Mr Berthollet found that 69 parts of sulphur in
combustion, united with 31 parts of oxygen, to form 100 parts of
sulphuric acid; and, by another experiment, made in a different manner,
he calculates that 100 parts of sulphuric acid consists of 72 parts
sulphur, combined with 28 parts of oxygen, all by weight.
This acid, in common with every other, can only dissolve metals when
they have been previously oxydated; but most of the metals are capable
of decomposing a part of the acid, so as to carry off a sufficient
quantity of oxygen, to render themselves soluble in the part of the acid
which remains undecomposed. This happens with silver, mercury, iron, and
zinc, in boiling concentrated sulphuric acid; they become first
oxydated by decomposing part of the acid, and then dissolve in the other
part; but they do not sufficiently disoxygenate the decomposed part of
the acid to reconvert it into sulphur; it is only reduced to the state
of sulphurous acid, which, being volatilised by the heat, flies off in
form of sulphurous acid gas.
Silver, mercury, and all the other metals except iron and zinc, are
insoluble in diluted sulphuric acid, because they have not sufficient
affinity with oxygen to draw it off from its combination either with the
sulphur, the sulphurous acid, or the hydrogen; but iron and zinc, being
assisted by the action of the acid, decompose the water, and become
oxydated at its expence, without the help of heat.
TABLE _of the Combinations of the Sulphurous Acid with the Salifiable
Bases, in the order of affinity._
_Names of the Bases._ _Names of the Neutral Salts._
Barytes Sulphite of barytes.
Potash potash.
Soda soda.
Lime lime.
Magnesia magnesia.
Ammoniac ammoniac.
Argill argill.
Oxyd of zinc zinc.
iron iron.
manganese manganese.
cobalt cobalt.
nickel nickel.
lead lead.
tin tin.
copper copper.
bismuth bismuth.
antimony antimony.
arsenic arsenic.
mercury mercury.
silver silver.
gold gold.
platina platina.
_Note._--The only one of these salts known to the old chemists was the
sulphite of potash, under the name of _Stahl's sulphureous salt_. So
that, before our new nomenclature, these compounds must have been named
_Stahl's sulphureous salt_, having base of fixed vegetable alkali, and
so of the rest.
In this Table we have followed Bergman's order of affinity of the
sulphuric acid, which is the same in regard to the earths and alkalies,
but it is not certain if the order be the same for the metallic
oxyds.--A.
SECT. XV.--_Observations upon Sulphurous Acid, and its Combinations._
The sulphurous acid is formed by the union of oxygen with sulphur by a
lesser degree of oxygenation than the sulphuric acid. It is procurable
either by burning sulphur slowly, or by distilling sulphuric acid from
silver, antimony, lead, mercury, or charcoal; by which operation a part
of the oxygen quits the acid, and unites to these oxydable bases, and
the acid passes over in the sulphurous state of oxygenation. This acid,
in the common pressure and temperature of the air, can only exist in
form of gas; but it appears, from the experiments of Mr Clouet, that, in
a very low temperature, it condenses, and becomes fluid. Water absorbs a
great deal more of this gas than of carbonic acid gas, but much less
than it does of muriatic acid gas.
That the metals cannot be dissolved in acids without being previously
oxydated, or by procuring oxygen, for that purpose, from the acids
during solution, is a general and well established fact, which I have
perhaps repeated too often. Hence, as sulphurous acid is already
deprived of great part of the oxygen necessary for forming the sulphuric
acid, it is more disposed to recover oxygen, than to furnish it to the
greatest part of the metals; and, for this reason, it cannot dissolve
them, unless previously oxydated by other means. From the same principle
it is that the metallic oxyds dissolve without effervescence, and with
great facility, in sulphurous acid. This acid, like the muriatic, has
even the property of dissolving metallic oxyds surcharged with oxygen,
and consequently insoluble in sulphuric acid, and in this way forms true
sulphats. Hence we might be led to conclude that there are no metallic
sulphites, were it not that the phenomena which accompany the solution
of iron, mercury, and some other metals, convince us that these metallic
substances are susceptible of two degrees of oxydation, during their
solution in acids. Hence the neutral salt in which the metal is least
oxydated must be named _sulphite_, and that in which it is fully
oxydated must be called _sulphat_. It is yet unknown whether this
distinction is applicable to any of the metallic sulphats, except those
of iron and mercury.
TABLE _of the Combinations of Phosphorous and Phosphoric Acids, with the
Salifiable Bases, in the Order of Affinity._
_Names of the_ _Names of the Neutral Salts formed by_
_Bases._ _Phosphorous Acid,_ _Phosphoric Acid._
Phosphites of(B) Phosphats of(C)
Lime lime lime.
Barytes barytes barytes.
Magnesia magnesia magnesia.
Potash potash potash.
Soda soda soda.
Ammoniac ammoniac ammoniac.
Argill argill argill.
Oxyds of(A)
zinc zinc zinc.
iron iron iron.
manganese manganese manganese.
cobalt cobalt cobalt.
nickel nickel nickel.
lead lead lead.
tin tin tin.
copper copper copper.
bismuth bismuth bismuth.
antimony antimony antimony.
arsenic arsenic arsenic.
mercury mercury mercury.
silver silver silver.
gold gold gold.
platina platina platina.
[Note A: The existence of metallic phosphites supposes that metals are
susceptible of solution in phosphoric acid at different degrees of
oxygenation, which is not yet ascertained.--A.]
[Note B: All the phosphites were unknown till lately, and consequently
have not hitherto received names.--A.]
[Note C: The greater part of the phosphats were only discovered of late,
and have not yet been named.--A.]
SECT. XVI.--_Observations upon Phosphorous and Phosphoric Acids, and
their Combinations._
Under the article Phosphorus, Part II. Sect. X. we have already given a
history of the discovery of that singular substance, with some
observations upon the mode of its existence in vegetable and animal
bodies. The best method of obtaining this acid in a state of purity is
by burning well purified phosphorus under bell-glasses, moistened on the
inside with distilled water; during combustion it absorbs twice and a
half its weight of oxygen; so that 100 parts of phosphoric acid is
composed of 28-1/2 parts of phosphorus united to 71-1/2 parts of oxygen.
This acid may be obtained concrete, in form of white flakes, which
greedily attract the moisture of the air, by burning phosphorus in a dry
glass over mercury.
To obtain phosphorous acid, which is phosphorus less oxygenated than in
the state of phosphoric acid, the phosphorus must be burnt by a very
slow spontaneous combustion over a glass-funnel leading into a crystal
phial; after a few days, the phosphorus is found oxygenated, and the
phosphorous acid, in proportion as it forms, has attracted moisture from
the air, and dropped into the phial. The phosphorous acid is readily
changed into phosphoric acid by exposure for a long time to the free
air; it absorbs oxygen from the air, and becomes fully oxygenated.
As phosphorus has a sufficient affinity for oxygen to attract it from
the nitric and muriatic acids, we may form phosphoric acid, by means of
these acids, in a very simple and cheap manner. Fill a tubulated
receiver, half full of concentrated nitric acid, and heat it gently,
then throw in small pieces of phosphorus through the tube, these are
dissolved with effervescence and red fumes of nitrous gas fly off; add
phosphorus so long as it will dissolve, and then increase the fire under
the retort to drive off the last particles of nitric acid; phosphoric
acid, partly fluid and partly concrete, remains in the retort.
TABLE _of the Combinations of Carbonic Acid, with the Salifiable Bases,
in the Order of Affinity._
_Names of_ _Resulting Neutral Salts._
_Bases_ _New Nomenclature._ _Old Nomenclature._
Barytes Carbonates of barytes(A) Aërated or effervescent heavy earth.
Lime lime {Chalk, calcareous spar,
{ Aërated calcareous earth.
Potash potash {Effervescing or aërated fixe
{ vegetable alkali, mephitis of
{ potash.
Soda soda {Aërated or effervescing fixed mineral
{ alkali, mephitic soda.
Magnesia magnesia {Aërated, effervescing, mild, or
{ mephitic magnesia.
Ammoniac ammoniac {Aërated, effervescing, mild, or
{ mephitic volatile alkali.
Argill argill {Aërated or effervescing argillaceous
{ earth, or earth of alum.
Oxyds of
zinc zinc Zinc spar, mephitic or aërated zinc.
iron iron Sparry iron-ore, mephitic or aërated iron.
manganese manganese Aërated manganese.
cobalt cobalt Aërated cobalt.
nickel nickel Aërated nickel.
lead lead Sparry lead-ore, or aërated lead.
tin tin Aërated tin.
copper copper Aërated copper.
bismuth bismuth Aërated bismuth.
antimony antimony Aërated antimony.
arsenic arsenic Aërated arsenic.
mercury mercury Aërated mercury.
silver silver Aërated silver.
gold gold Aërated gold.
platina platina Aërated platina.
[Note A: As these salts have only been understood of late, they have
not, properly speaking, any old names. Mr Morveau, in the First Volume
of the Encyclopedia, calls them _Mephites_; Mr Bergman gives them the
name of _aërated_; and Mr de Fourcroy, who calls the carbonic acid
_chalky acid_, gives them the name of _chalks_.--A]
SECT. XVII.--_Observations upon Carbonic Acid, and its Combinations._
Of all the known acids, the carbonic is the most abundant in nature; it
exists ready formed in chalk, marble, and all the calcareous stones, in
which it is neutralized by a particular earth called _lime_. To
disengage it from this combination, nothing more is requisite than to
add some sulphuric acid, or any other which has a stronger affinity for
lime; a brisk effervescence ensues, which is produced by the
disengagement of the carbonic acid which assumes the state of gas
immediately upon being set free. This gas, incapable of being condensed
into the solid or liquid form by any degree of cold or of pressure
hitherto known, unites to about its own bulk of water, and thereby forms
a very weak acid. It may likewise be obtained in great abundance from
saccharine matter in fermentation, but is then contaminated by a small
portion of alkohol which it holds in solution.
As charcoal is the radical of this acid, we may form it artificially, by
burning charcoal in oxygen gas, or by combining charcoal and metallic
oxyds in proper proportions; the oxygen of the oxyd combines with the
charcoal, forming carbonic acid gas, and the metal being left free,
recovers its metallic or reguline form.
We are indebted for our first knowledge of this acid to Dr Black, before
whose time its property of remaining always in the state of gas had made
it to elude the researches of chemistry.
It would be a most valuable discovery to society, if we could decompose
this gas by any cheap process, as by that means we might obtain, for
economical purposes, the immense store of charcoal contained in
calcareous earths, marbles, limestones, &c. This cannot be effected by
single affinity, because, to decompose the carbonic acid, it requires a
substance as combustible as charcoal itself, so that we should only make
an exchange of one combustible body for another not more valuable; but
it may possibly be accomplished by double affinity, since this process
is so readily performed by Nature, during vegetation, from the most
common materials.
TABLE _of the Combinations of Muriatic Acid, with the Salifiable Bases,
in the Order of Affinity._
_Names of the_ _Resulting Neutral Salts._
_bases._ _New nomenclature._ _Old nomenclature._
Barytes. Muriat of {Sea-salt, having base of
barytes { heavy earth.
Potash potash {Febrifuge salt of Sylvius:
{ Muriated vegetable fixed
{ alkali.
Soda soda Sea-salt.
Lime lime Muriated lime. Oil of lime.
Magnesia magnesia {Marine Epsom salt. Muriated magnesia.
Ammoniac ammoniac Sal ammoniac.
Argill argill {Muriated alum, sea-salt
{ with base of earth of alum.
Oxyd of
zinc zinc Sea-salt of, or muriatic zinc.
iron iron Salt of iron, Martial sea-salt.
manganese manganese Sea-salt of manganese.
cobalt cobalt Sea-salt of cobalt.
nickel nickel Sea-salt of nickel.
lead lead Horny-lead. Plumbum corneum.
tin smoaking of tin Smoaking liquor of Libavius.
solid of tin Solid butter of tin.
copper copper Sea-salt of copper.
bismuth bismuth Sea-salt of bismuth.
antimony antimony Sea-salt of antimony.
arsenic arsenic Sea-salt of arsenic.
{sweet of mercury {Sweet sublimate of mercury,
{ { calomel, aquila alba.
mercury { {
{corrosive of {Corrosive sublimate of
{ mercury { mercury.
silver silver Horny silver, argentum corneum, luna cornea.
gold gold Sea-salt of gold.
platina platina Sea-salt of platina.
TABLE _Of the Combinations of Oxygenated Muriatic Acid, with the
Salifiable Bases, in the Order of Affinity._
_Names of the Neutral Salts by_
_Names of the Bases._ _the new Nomenclature._
Oxygenated muriat of
Barytes barytes.
Potash potash.
Soda soda.
Lime lime.
Magnesia magnesia.
Argill argill.
Oxyd of
zinc zinc.
iron iron.
manganese manganese.
cobalt cobalt.
nickel nickel.
lead lead.
tin tin.
copper copper.
bismuth bismuth.
antimony antimony.
arsenic arsenic.
mercury mercury.
silver silver.
gold gold.
platina platina.
This order of salts, entirely unknown to the ancient chemists, was
discovered in 1786 by Mr Berthollet.--A.
SECT. XIX.--_Observations upon Muriatic and Oxygenated Muriatic Acids,
and their Combinations._
Muriatic acid is very abundant in the mineral kingdom naturally combined
with different salifiable bases, especially with soda, lime, and
magnesia. In sea-water, and the water of several lakes, it is combined
with these three bases, and in mines of rock-salt it is chiefly united
to soda. This acid does not appear to have been hitherto decomposed in
any chemical experiment; so that we have no idea whatever of the nature
of its radical, and only conclude, from analogy with the other acids,
that it contains oxygen as its acidifying principle. Mr Berthollet
suspects the radical to be of a metallic nature; but, as Nature appears
to form this acid daily, in inhabited places, by combining miasmata with
aëriform fluids, this must necessarily suppose a metallic gas to exist
in the atmosphere, which is certainly not impossible, but cannot be
admitted without proof.
The muriatic acid has only a moderate adherence to the salifiable bases,
and can readily be driven from its combination with these by sulphuric
acid. Other acids, as the nitric, for instance, may answer the same
purpose; but nitric acid being volatile, would mix, during
distillation, with the muriatic. About one part of sulphuric acid is
sufficient to decompose two parts of decrepitated sea-salt. This
operation is performed in a tubulated retort, having Woulfe's apparatus,
(Pl. IV. Fig. 1.), adapted to it. When all the junctures are properly
lured, the sea-salt is put into the retort through the tube, the
sulphuric acid is poured on, and the opening immediately closed with its
ground crystal stopper. As the muriatic acid can only subsist in the
gaseous form in the ordinary temperature, we could not condense it
without the presence of water. Hence the use of the water with which the
bottles in Woulfe's apparatus are half filled; the muriatic acid gas,
driven off from the sea-salt in the retort, combines with the water, and
forms what the old chemists called _smoaking spirit of salt_, or
_Glauber's spirit of sea-salt_, which we now name _muriatic acid_.
The acid obtained by the above process is still capable of combining
with a farther dose of oxygen, by being distilled from the oxyds of
manganese, lead, or mercury, and the resulting acid, which we name
_oxygenated muriatic acid_, can only, like the former, exist in the
gasseous form, and is absorbed, in a much smaller quantity by water.
When the impregnation of water with this gas is pushed beyond a certain
point, the superabundant acid precipitates to the bottom of the vessels
in a concrete form. Mr Berthollet has shown that this acid is capable
of combining with a great number of the salifiable bases; the neutral
salts which result from this union are susceptible of deflagrating with
charcoal, and many of the metallic substances; these deflagrations are
very violent and dangerous, owing to the great quantity of caloric which
the oxygen carries alongst with it into the composition of oxygenated
muriatic acid.
TABLE _of the Combinations of Nitro-muriatic Acid with the Salifiable
Bases, in the Order of Affinity, so far as is known._
_Names of the Bases._ _Names of the Neutral Salts._
Argill Nitro-muriat of argill.
Ammoniac ammoniac.
Oxyd of
antimony antimony.
silver silver.
arsenic arsenic.
Barytes barytes.
Oxyd of
bismuth bismuth.
Lime lime.
Oxyd of
cobalt cobalt.
copper copper.
tin tin.
iron iron.
Magnesia magnesia.
Oxyd of
manganese manganese.
mercury mercury.
molybdena molybdena.
nickel nickel.
gold gold.
platina platina.
lead lead.
Potash potash.
Soda soda.
Oxyd of
tungstein tungstein.
zinc zinc.
_Note._--Most of these combinations, especially those with the earths
and alkalies, have been little examined, and we are yet to learn whether
they form a mixed salt in which the compound radical remains combined,
or if the two acids separate, to form two distinct neutral salts.--A.
SECT. XX.--_Observations upon the Nitro-Muriatic Acid, and its
Combinations._
The nitro-muriatic acid, formerly called _aqua regia_, is formed by a
mixture of nitric and muriatic acids; the radicals of these two acids
combine together, and form a compound base, from which an acid is
produced, having properties peculiar to itself, and distinct from those
of all other acids, especially the property of dissolving gold and
platina.
In dissolutions of metals in this acid, as in all other acids, the
metals are first oxydated by attracting a part of the oxygen from the
compound radical. This occasions a disengagement of a particular species
of gas not hitherto described, which may be called _nitro-muriatic gas_;
it has a very disagreeable smell, and is fatal to animal life when
respired; it attacks iron, and causes it to rust; it is absorbed in
considerable quantity by water, which thereby acquires some slight
characters of acidity. I had occasion to make these remarks during a
course of experiments upon platina, in which I dissolved a considerable
quantity of that metal in nitro-muriatic acid.
I at first suspected that, in the mixture of nitric and muriatic acids,
the latter attracted a part of the oxygen from the former, and became
converted into oxygenated muriatic acid, which gave it the property of
dissolving gold; but several facts remain inexplicable upon this
supposition. Were it so, we must be able to disengage nitrous gas by
heating this acid, which however does not sensibly happen. From these
considerations, I am led to adopt the opinion of Mr Berthollet, and to
consider nitro-muriatic acid as a single acid, with a compound base or
radical.
TABLE _of the Combinations of Fluoric Acid, with the Salifiable Bases,
in the Order of Affinity._
_Names of the Bases._ _Names of the Neutral Salts._
Lime Fluat of lime.
Barytes barytes.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Oxyd of
zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
arsenic arsenic.
bismuth bismuth.
mercury mercury.
silver silver.
gold gold.
platina platina.
And by the dry way,
Argill Fluat of argill.
_Note._--These combinations were entirely unknown to the old chemists,
and consequently have no names in the old nomenclature.--A.
SECT. XXI.--_Observations upon the Fluoric Acid, and its Combinations._
Fluoric exists ready formed by Nature in the fluoric spars[42], combined
with calcareous earth, so as to form an insoluble neutral salt. To
obtain it disengaged from that combination, fluor spar, or fluat of
lime, is put into a leaden retort, with a proper quantity of sulphuric
acid, a recipient likewise of lead, half full of water, is adapted, and
fire is applied to the retort. The sulphuric acid, from its greater
affinity, expels the fluoric acid which passes over and is absorbed by
the water in the receiver. As fluoric acid is naturally in the gasseous
form in the ordinary temperature, we can receive it in a
pneumato-chemical apparatus over mercury. We are obliged to employ
metallic vessels in this process, because fluoric acid dissolves glass
and silicious earth, and even renders these bodies volatile, carrying
them over with itself in distillation in the gasseous form.
We are indebted to Mr Margraff for our first acquaintance with this
acid, though, as he could never procure it free from combination with a
considerable quantity of silicious earth, he was ignorant of its being
an acid sui generis. The Duke de Liancourt, under the name of Mr
Boulanger, considerably increased our knowledge of its properties; and
Mr Scheele seems to have exhausted the subject. The only thing remaining
is to endeavour to discover the nature of the fluoric radical, of which
we cannot hitherto form any ideas, as the acid does not appear to have
been decomposed in any experiment. It is only by means of compound
affinity that experiments ought to be made with this view, with any
probability of success.
TABLE _of the Combinations of Boracic Acid, with the Salifiable Bases,
in the Order of Affinity._
_Bases._ _Neutral Salts._
Lime Borat of lime.
Barytes barytes.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Oxyd of
zinc zinc.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
mercury mercury.
Argill argill.
_Note._--Most of these combinations were neither known nor named by the
old chemists. The boracic acid was formerly called _sedative salt_, and
its compounds _borax_, with base of fixed vegetable alkali, &c.--A.
SECT. XXII.--_Observations upon Boracic Add and its Combinations._
This is a concrete acid, extracted from a salt procured from India
called _borax_ or _tincall_. Although borax has been very long employed
in the arts, we have as yet very imperfect knowledge of its origin, and
of the methods by which it is extracted and purified; there is reason to
believe it to be a native salt, found in the earth in certain parts of
the east, and in the water of some lakes. The whole trade of borax is in
the hands of the Dutch, who have been exclusively possessed of the art
of purifying it till very lately, that Messrs L'Eguillier of Paris have
rivalled them in the manufacture; but the process still remains a secret
to the world.
By chemical analysis we learn that borax is a neutral salt with excess
of base, consisting of soda, partly saturated with a peculiar acid long
called _Homberg's sedative salt_, now _the boracic acid_. This acid is
found in an uncombined state in the waters of certain lakes. That of
Cherchiais in Italy contains 94-1/2 grains in each pint of water.
To obtain boracic acid, dissolve some borax in boiling water, filtrate
the solution, and add sulphuric acid, or any other having greater
affinity to soda than the boracic acid; this latter acid is separated,
and is procured in a crystalline form by cooling. This acid was long
considered as being formed during the process by which it is obtained,
and was consequently supposed to differ according to the nature of the
acid employed in separating it from the soda; but it is now universally
acknowledged that it is identically the same acid, in whatever way
procured, provided it be properly purified from mixture of other acids,
by warning, and by repeated solution and cristallization. It is soluble
both in water and alkohol, and has the property of communicating a green
colour to the flame of that spirit. This circumstance led to a suspicion
of its containing copper, which is not confirmed by any decisive
experiment. On the contrary, if it contain any of that metal, it must
only be considered as an accidental mixture. It combines with the
salifiable bases in the humid way; and though, in this manner, it is
incapable of dissolving any of the metals directly, this combination is
readily affected by compound affinity.
The Table presents its combinations in the order of affinity in the
humid way; but there is a considerable change in the order when we
operate via sicca; for, in that case, argill, though the last in our
list, must be placed immediately after soda.
The boracic radical is hitherto unknown; no experiments having as yet
been able to decompose the acid; We conclude, from analogy with the
other acids, that oxygen exists in its composition as the acidifying
principle.
TABLE _of the Combinations of Arseniac Acid, with the Salifiable Bases,
in the Order of Affinity._
_Bases._ _Neutral Salts._
Lime Arseniat of lime.
Barytes barytes.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Oxyd of
zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
bismuth bismuth.
mercury mercury.
antimony antimony.
silver silver.
gold gold.
platina platina.
Argill argill.
_Note._--This order of salts was entirely unknown to the antient
chemists. Mr Macquer, in 1746, discovered the combinations of arseniac
acid with potash and soda, to which he gave the name of _arsenical
neutral salts_.--A.
SECT. XXIII.--_Observations upon Arseniac Acid, and its Combinations._
In the Collections of the Academy for 1746, Mr Macquer shows that, when
a mixture of white oxyd of arsenic and nitre are subjected to the action
of a strong fire, a neutral salt is obtained, which he calls _neutral
salt of arsenic_. At that time, the cause of this singular phenomenon,
in which a metal acts the part of an acid, was quite unknown; but more
modern experiments teach that, during this process, the arsenic becomes
oxygenated, by carrying off the oxygen of the nitric acid; it is thus
converted into a real acid, and combines with the potash. There are
other methods now known for oxygenating arsenic, and obtaining its acid
free from combination. The most simple and most effectual of these is as
follows: Dissolve white oxyd of arsenic in three parts, by weight, of
muriatic acid; to this solution, in a boiling state, add two parts of
nitric acid, and evaporate to dryness. In this process the nitric acid
is decomposed, its oxygen unites with the oxyd of arsenic, and converts
it into an acid, and the nitrous radical flies off in the state of
nitrous gas; whilst the muriatic acid is converted by the heat into
muriatic acid gas, and may be collected in proper vessels. The arseniac
acid is entirely freed from the other acids employed during the process
by heating it in a crucible till it begins to grow red; what remains is
pure concrete arseniac acid.
Mr Scheele's process, which was repeated with great success by Mr
Morveau, in the laboratory at Dijon, is as follows: Distil muriatic acid
from the black oxyd of manganese, this converts it into oxygenated
muriatic acid, by carrying off the oxygen from the manganese, receive
this in a recipient containing white oxyd of arsenic, covered by a
little distilled water; the arsenic decomposes the oxygenated muriatic
acid, by carrying off its supersaturation of oxygen, the arsenic is
converted into arseniac acid, and the oxygenated muriatic acid is
brought back to the state of common muriatic acid. The two acids are
separated by distillation, with a gentle heat increased towards the end
of the operation, the muriatic acid passes over, and the arseniac acid
remains behind in a white concrete form.
The arseniac acid is considerably less volatile than white oxyd of
arsenic; it often contains white oxyd of arsenic in solution, owing to
its not being sufficiently oxygenated; this is prevented by continuing
to add nitrous acid, as in the former process, till no more nitrous gas
is produced. From all these observations I would give the following
definition of arseniac acid. It is a white concrete metallic acid,
formed by the combination of arsenic with oxygen, fixed in a red heat,
soluble in water, and capable of combining with many of the salifiable
bases.
SECT. XXIV.--_Observations upon Molybdic Acid, and its Combinations with
Acidifiable Bases[43]._
Molybdena is a particular metallic body, capable of being oxygenated, so
far as to become a true concrete acid[44]. For this purpose, one part
ore of molybdena, which is a natural sulphuret of that metal, is put
into a retort, with five or six parts nitric acid, diluted with a
quarter of its weight of water, and heat is applied to the retort; the
oxygen of the nitric acid acts both upon the molybdena and the sulphur,
converting the one into molybdic, and the other into sulphuric acid;
pour on fresh quantities of nitric acid so long as any red fumes of
nitrous gas escape; the molydbena is then oxygenated as far as is
possible, and is found at the bottom of the retort in a pulverulent
form, resembling chalk. It must be washed in warm water, to separate any
adhering particles of sulphuric acid; and, as it is hardly soluble, we
lose very little of it in this operation. All its combinations with
salifiable bases were unknown to the ancient chemists.
TABLE _of the Combinations of Tungstic Acid with the Salifiable Bases._
_Bases._ _Neutral Salts._
Lime Tungstat of lime.
Barytes barytes.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Argill argill.
Oxyd of antimony(A), &c. antimony(B), &c.
[Note A: The combinations with metallic oxyds were set down by Mr
Lavoisier in alphabetical order; their order of affinity being unknown,
I have omitted them, as serving no purpose.--E.]
[Note B: All these salts were unknown to the ancient chemists.--A.]
SECT. XXV.--_Observations upon Tungstic Acid, and its Combinations._
Tungstein is a particular metal, the ore of which has frequently been
confounded with that of tin. The specific gravity of this ore is to
water as 6 to 1; in its form of cristallization it resembles the
garnet, and varies in colour from a pearl-white to yellow and reddish;
it is found in several parts of Saxony and Bohemia. The mineral called
_Wolfram_, which is frequent in the mines of Cornwal, is likewise an ore
of this metal. In all these ores the metal is oxydated; and, in some of
them, it appears even to be oxygenated to the state of acid, being
combined with lime into a true tungstat of lime.
To obtain the acid free, mix one part of ore of tungstein with four
parts of carbonat of potash, and melt the mixture in a crucible, then
powder and pour on twelve parts of boiling water, add nitric acid, and
the tungstic acid precipitates in a concrete form. Afterwards, to insure
the complete oxygenation of the metal, add more nitric acid, and
evaporate to dryness, repeating this operation so long as red fumes of
nitrous gas are produced. To procure tungstic acid perfectly pure, the
fusion of the ore with carbonat of potash must be made in a crucible of
platina, otherwise the earth of the common crucibles will mix with the
products, and adulterate the acid.
TABLE _of the Combinations of Tartarous Acid, with the Salifiable Bases,
in the Order of Affinity._
_Bases._ _Neutral Salts._
Lime Tartarite of lime.
Barytes barytes.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Argill argill.
Oxyd of
zinc zinc.
iron iron.
manganese manganese.
cobalt cobalt.
nickel nickel.
lead lead.
tin tin.
copper copper.
bismuth bismuth.
antimony antimony.
arsenic arsenic.
silver silver.
mercury mercury.
gold gold.
platina platina.
SECT. XXVI.--_Observations upon Tartarous Acid, and its Combinations._
Tartar, or the concretion which fixes to the inside of vessels in which
the fermentation of wine is completed, is a well known salt, composed of
a peculiar acid, united in considerable excess to potash. Mr Scheele
first pointed out the method of obtaining this acid pure. Having
observed that it has a greater affinity to lime than to potash, he
directs us to proceed in the following manner. Dissolve purified tartar
in boiling water, and add a sufficient quantity of lime till the acid be
completely saturated. The tartarite of lime which is formed, being
almost insoluble in cold water, falls to the bottom, and is separated
from the solution of potash by decantation; it is afterwards washed in
cold water, and dried; then pour on some sulphuric acid, diluted with
eight or nine parts of water, digest for twelve hours in a gentle heat,
frequently stirring the mixture; the sulphuric acid combines with the
lime, and the tartarous acid is left free. A small quantity of gas, not
hitherto examined, is disengaged during this process. At the end of
twelve hours, having decanted off the clear liquor, wash the sulphat of
lime in cold water, which add to the decanted liquor, then evaporate
the whole, and the tartarous acid is obtained in a concrete form. Two
pounds of purified tartar, by means of from eight to ten ounces of
sulphuric acid, yield about eleven ounces of tartarous acid.
As the combustible radical exists in excess, or as the acid from tartar
is not fully saturated with oxygen, we call it _tartarous acid_, and the
neutral salts formed by its combinations with salifiable bases
_tartarites_. The base of the tartarous acid is a carbono-hydrous or
hydro-carbonous radical, less oxygenated than in the oxalic acid; and it
would appear, from the experiments of Mr Hassenfratz, that azote enters
into the composition of the tartarous radical, even in considerable
quantity. By oxygenating the tartarous acid, it is convertible into
oxalic, malic, and acetous acids; but it is probable the proportions of
hydrogen and charcoal in the radical are changed during these
conversions, and that the difference between these acids does not alone
consist in the different degrees of oxygenation.
The tartarous acid is susceptible of two degrees of saturation in its
combinations with the fixed alkalies; by one of these a salt is formed
with excess of acid, improperly called _cream of tartar_, which in our
new nomenclature is named _acidulous tartarite of potash_; by a second
or equal degree of saturation a perfectly neutral salt is formed,
formerly called _vegetable salt_, which we name _tartarite of potash_.
With soda this acid forms tartarite of soda, formerly called _sal de
Seignette_, or _sal polychrest of Rochell_.
SECT. XXVII.--_Observations upon Malic Acid, and its Combinations with
the Salifiable Bases[45]._
The malic acid exists ready formed in the sour juice of ripe and unripe
apples, and many other fruits, and is obtained as follows: Saturate the
juice of apples with potash or soda, and add a proper proportion of
acetite of lead dissolved in water; a double decomposition takes place,
the malic acid combines with the oxyd of lead and precipitates, being
almost insoluble, and the acetite of potash or soda remains in the
liquor. The malat of lead being separated by decantation, is washed with
cold water, and some dilute sulphuric acid is added; this unites with
the lead into an insoluble sulphat, and the malic acid remains free in
the liquor.
This acid, which is found mixed with citric and tartarous acid in a
great number of fruits, is a kind of medium between oxalic and acetous
acids being more oxygenated than the former, and less so than the
latter. From this circumstance, Mr Hermbstadt calls it _imperfect
vinegar_; but it differs likewise from acetous acid, by having rather
more charcoal, and less hydrogen, in the composition of its radical.
When an acid much diluted has been used in the foregoing process, the
liquor contains oxalic as well as malic acid, and probably a little
tartarous, these are separated by mixing lime-water with the acids,
oxalat, tartarite, and malat of lime are produced; the two former, being
insoluble, are precipitated, and the malat of lime remains dissolved;
from this the pure malic acid is separated by the acetite of lead, and
afterwards by sulphuric acid, as directed above.
TABLE _of the Combinations of Citric Acid, with the Salifiable Bases, in
the Order of Affinity(A)._
_Bases._ _Neutral Salts._
Barytes Citrat of barytes.
Lime lime.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Oxyd of
zinc zinc.
manganese manganese.
iron iron.
lead lead.
cobalt cobalt.
copper copper.
arsenic arsenic.
mercury mercury.
antimony antimony.
silver silver.
gold gold.
platina platina.
Argill argill.
[Note A: These combinations were unknown to the ancient chemists. The
order of affinity of the salifiable bases with this acid was determined
by Mr Bergman and by Mr de Breney of the Dijon Academy.--A.]
SECT. XXVIII.--_Observations upon Citric Acid, and its Combinations._
The citric acid is procured by expression from lemons, and is found in
the juices of many other fruits mixed with malic acid. To obtain it pure
and concentrated, it is first allowed to depurate from the mucous part
of the fruit by long rest in a cool cellar, and is afterwards
concentrated by exposing it to the temperature of 4 or 5 degrees below
Zero, from 21° to 23° of Fahrenheit, the water is frozen, and the acid
remains liquid, reduced to about an eighth part of its original bulk. A
lower degree of cold would occasion the acid to be engaged amongst the
ice, and render it difficultly separable. This process was pointed out
by Mr Georgius.
It is more easily obtained by saturating the lemon-juice with lime, so
as to form a citrat of lime, which is insoluble in water; wash this
salt, and pour on a proper quantity of sulphuric acid; this forms a
sulphat of lime, which precipitates and leaves the citric acid free in
the liquor.
TABLE _of the Combinations of Pyro-lignous Acid with the Salifiable
Bases, in the Order of Affinity(A)._
_Bases._ _Neutral Salts._
Lime Pyro-mucite of lime.
Barytes barytes.
Potash potash.
Soda soda.
Magnesia magnesia.
Ammoniac ammoniac.
Oxyd of
zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
arsenic arsenic.
bismuth bismuth.
mercury mercury.
antimony antimony.
silver silver.
gold gold.
platina platina.
Argill argill.
[Note A: The above affinities were determined by Messrs de Morveau and
EloI Boursier de Clervaux. These combinations were entirely unknown till
lately.--A.]
SECT. XXIX.--_Observations upon Pyro-lignous Acid, and its
Combinations._
The ancient chemists observed that most of the woods, especially the
more heavy and compact ones, gave out a particular acid spirit, by
distillation, in a naked fire; but, before Mr Goetling, who gives an
account of his experiments upon this subject in Crell's Chemical Journal
for 1779, no one had ever made any inquiry into its nature and
properties. This acid appears to be the same, whatever be the wood it is
procured from. When first distilled, it is of a brown colour, and
considerably impregnated with charcoal and oil; it is purified from
these by a second distillation. The pyro-lignous radical is chiefly
composed of hydrogen and charcoal.
SECT. XXX.--_Observations upon Pyro-tartarous Acid, and its Combinations
with the Salifiable Bases[46]._
The name of _Pyro-tartarous acid_ is given to a dilute empyreumatic acid
obtained from purified acidulous tartarite of potash by distillation in
a naked fire. To obtain it, let a retort be half filled with powdered
tartar, adapt a tubulated recipient, having a bent tube communicating
with a bell-glass in a pneumato-chemical apparatus; by gradually raising
the fire under the retort, we obtain the pyro-tartarous acid mixed with
oil, which is separated by means of a funnel. A vast quantity of
carbonic acid gas is disengaged during the distillation. The acid
obtained by the above process is much contaminated with oil, which ought
to be separated from it. Some authors advise to do this by a second
distillation; but the Dijon academicians inform us, that this is
attended with great danger from explosions which take place during the
process.
TABLE _of the Combinations of Pyro-mucous Acid, with the Salifiable
Bases, in the Order of Affinity(A)._
_Bases._ _Neutral Salts._
Potash Pyro-mucite of potash.
Soda soda.
Barytes barytes.
Lime lime.
Magnesia magnesia.
Ammoniac ammoniac.
Argill argill.
Oxyd of
zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
arsenic arsenic.
bismuth bismuth.
antimony antimony.
[Note A: All these combinations were unknown to the ancient
chemists.--A.]
SECT. XXXI.--_Observations upon Pyro-mucous Acid, and its Combinations._
This acid is obtained by distillation in a naked fire from sugar, and
all the saccharine bodies; and, as these substances swell greatly in the
fire, it is necessary to leave seven-eighths of the retort empty. It is
of a yellow colour, verging to red, and leaves a mark upon the skin,
which will not remove but alongst with the epidermis. It may be procured
less coloured, by means of a second distillation, and is concentrated by
freezing, as is directed for the citric acid. It is chiefly composed of
water and oil slightly oxygenated, and is convertible into oxalic and
malic acids by farther oxygenation with the nitric acid.
It has been pretended that a large quantity of gas is disengaged during
the distillation of this acid, which is not the case if it be conducted
slowly, by means of moderate heat.
TABLE _of the Combinations of the Oxalic Acid, with the Salifiable
Bases, in the Order of Affinity(A)._
_Bases._ _Neutral Salts._
Lime Oxalat of lime.
Barytes barytes.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Argill argill.
Oxyd of
zinc zinc.
iron iron.
manganese manganese.
cobalt cobalt.
nickel nickel.
lead lead.
copper copper.
bismuth bismuth.
antimony antimony.
arsenic arsenic.
mercury mercury.
silver silver.
gold gold.
platina platina.
[Note A: All unknown to the ancient chemists.--A.]
SECT. XXXII.--_Observations upon Oxalic Acid, and its Combinations._
The oxalic acid is mostly prepared in Switzerland and Germany from the
expressed juice of sorrel, from which it cristallizes by being left long
at rest; in this state it is partly saturated with potash, forming a
true acidulous oxalat of potash, or salt with excess of acid. To obtain
it pure, it must be formed artificially by oxygenating sugar, which
seems to be the true oxalic radical. Upon one part of sugar pour six or
eight parts of nitric acid, and apply a gentle heat; a considerable
effervescence takes place, and a great quantity of nitrous gas is
disengaged; the nitric acid is decomposed, and its oxygen unites to the
sugar: By allowing the liquor to stand at rest, cristals of pure oxalic
acid are formed, which must be dried upon blotting paper, to separate
any remaining portions of nitric acid; and, to ensure the purity of the
acid, dissolve the cristals in distilled water, and cristallize them
afresh.
+---------------+------------------+---------------------------------------
| _Bases._ | _Neutral salts._ |_Names of the resulting neutral salts_ |
| | |_according to the old nomenclature._ |
|---------------+------------------+---------------------------------------+
|Barytes |Acetite of barytes{Unknown to the ancients. Discovered by |
| | {Mr de Morveau, who calls it _barotic |
| | {acéte_. |
| | | |
|Potash | ---- potash {Secret terra foliata tartari of Muller.|
| | {Arcanum tartari of Basil Valentin and |
| | {Paracelsus. Purgative magistery of |
| | {tartar of Schroëder. Essential salt of |
| | {wine of Zwelfer. Regenerated tartar of |
| | {Tachenius. Diuretic salt of Sylvius |
| | {and Wilson. |
| | | |
|Soda | ---- soda {Foliated earth with base of mineral |
| | {alkali. Mineral or crystallisable |
| | {foliated earth. Mineral acetous salt. |
| | | |
|Lime | ---- lime {Salt of chalk, coral, or crabs eyes; |
| | {mentioned by Hartman. |
| | | |
|Magnesia | ---- magnesia |First mentioned by Mr Wenzel. |
| | | |
|Ammoniac | ---- ammoniac {Spiritus Mindereri. |
| | {Ammoniacal acetous salt. |
| | | |
|Oxyd of zinc | ---- zinc {Known to Glauber, Schwedemberg, |
| | {Respour, Pott, de Lassone, and Wenzel, |
| | {but not named. |
| | | |
| ---- manganese| ---- manganese |Unknown to the ancients. |
| | | |
| ---- iron | ---- iron {Martial vinegar. Described by Monnet, |
| | {Wenzel, and the Duke d'Ayen. |
| | | |
| ---- lead | ---- lead {Sugar, vinegar, and salt of lead or |
| | {Saturn. |
| | | |
| ---- tin | ---- tin {Known to Lemery, Margraff, Monnet, |
| | {Weslendorf, and Wenzel, but not named. |
| | | |
| ---- cobalt | ---- cobalt |Sympathetic ink of Mr Cadet. |
| | | |
| ---- copper | ---- copper {Verdigris, crystals of verditer, |
| | {verditer, distilled verdigris, crystals|
| | {of Venus or of copper. |
| | | |
| ---- nickel | ---- nickel |Unknown to the ancients. |
| | | |
| ---- arsenic | ---- arsenic {Arsenico-acetous fuming liquor, |
| | {liquid phosphorus of Mr Cadet. |
| | | |
| ---- bismuth | ---- bismuth {Sugar of bismuth of Mr Geoffroi. Known |
| | {to Gellert, Pott, Weslendorf, Bergman, |
| | {and de Morveau. |
| | | |
| ---- mercury | ---- mercury {Mercurial foliated earth, Keyser's |
| | {famous antivenereal remedy. Mentioned |
| | {by Gebaver in 1748; known to Helot, |
| | {Margraff, Baumé, Bergman, and |
| | {de Morveau. |
| | | |
| ---- antimony | ---- antimony |Unknown. |
| | | |
| ---- silver | ---- silver {Described by Margraff, Monnet, and |
| | {Wenzel; unknown to the ancients. |
| | | |
| ---- gold | ---- gold {Little known, mentioned by Schroëder |
| | {and Juncker. |
| | | |
| ---- platina | ---- platina |Unknown. |
| | | |
|Argill | ---- argill |According to Mr Wenzel, vinegar |
| | |dissolves only a very small proportion |
| | |of argill. |
+---------------+------------------+---------------------------------------+
From the liquor remaining after the first cristallization of the oxalic
acid we may obtain malic acid by refrigeration: This acid is more
oxygenated than the oxalic; and, by a further oxygenation, the sugar is
convertible into acetous acid, or vinegar.
The oxalic acid, combined with a small quantity of soda or potash, has
the property, like the tartarous acid, of entering into a number of
combinations without suffering decomposition: These combinations form
triple salts, or neutral salts with double bases, which ought to have
proper names. The salt of sorrel, which is potash having oxalic acid
combined in excess, is named acidulous oxalat of potash in our new
nomenclature.
The acid procured from sorrel has been known to chemists for more than a
century, being mentioned by Mr Duclos in the Memoirs of the Academy for
1688, and was pretty accurately described by Boerhaave; but Mr Scheele
first showed that it contained potash, and demonstrated its identity
with the acid formed by the oxygenation of sugar.
SECT. XXXIII.--_Observations upon Acetous Acid, and its Combinations._
This acid is composed of charcoal and hydrogen united together, and
brought to the state of an acid by the addition of oxygen; it is
consequently formed by the same elements with the tartarous oxalic,
citric, malic acids, and others, but the elements exist in different
proportions in each of these; and it would appear that the acetous acid
is in a higher state of oxygenation than these other acids. I have some
reason to believe that the acetous radical contains a small portion of
azote; and, as this element is not contained in the radicals of any
vegetable acid except the tartarous, this circumstance is one of the
causes of difference. The acetous acid, or vinegar, is produced by
exposing wine to a gentle heat, with the addition of some ferment: This
is usually the ley, or mother, which has separated from other vinegar
during fermentation, or some similar matter. The spiritous part of the
wine, which consists of charcoal and hydrogen, is oxygenated, and
converted into vinegar: This operation can only take place with free
access of air, and is always attended by a diminution of the air
employed in consequence of the absorption of oxygen; wherefore, it ought
always to be carried on in vessels only half filled with the vinous
liquor submitted to the acetous fermentation. The acid formed during
this process is very volatile, is mixed with a large proportion of
water, and with many foreign substances; and, to obtain it pure, it is
distilled in stone or glass vessels by a gentle fire. The acid which
passes over in distillation is somewhat changed by the process, and is
not exactly of the same nature with what remains in the alembic, but
seems less oxygenated: This circumstance has not been formerly observed
by chemists.
Distillation is not sufficient for depriving this acid of all its
unnecessary water; and, for this purpose, the best way is by exposing it
to a degree of cold from 4° to 6° below the freezing point, from 19° to
23° of Fahrenheit; by this means the aqueous part becomes frozen, and
leaves the acid in a liquid state, and considerably concentrated. In the
usual temperature of the air, this acid can only exist in the gasseous
form, and can only be retained by combination with a large proportion of
water. There are other chemical processes for obtaining the acetous
acid, which consist in oxygenating the tartarous, oxalic, or malic
acids, by means of nitric acid; but there is reason to believe the
proportions of the elements of the radical are changed during this
process. Mr Hassenfratz is at present engaged in repeating the
experiments by which these conversions are said to be produced.
The combinations of acetous acid with the various salifiable bases are
very readily formed; but most of the resulting neutral salts are not
cristallizable, whereas those produced by the tartarous and oxalic acids
are, in general, hardly soluble. Tartarite and oxalat of lime are not
soluble in any sensible degree: The malats are a medium between the
oxalats and acetites, with respect to solubility, and the malic acid is
in the middle degree of saturation between the oxalic and acetous acids.
With this, as with all the acids, the metals require to be oxydated
previous to solution.
The ancient chemists knew hardly any of the salts formed by the
combinations of acetous acid with the salifiable bases, except the
acetites of potash, soda, ammoniac, copper, and lead. Mr Cadet
discovered the acetite of arsenic[47]; Mr Wenzel, the Dijon academicians
Mr de Lassone, and Mr Proust, made us acquainted with the properties of
the other acetites. From the property which acetite of potash possesses,
of giving out ammoniac in distillation, there is some reason to suppose,
that, besides charcoal and hydrogen, the acetous radical contains a
small proportion of azote, though it is not impossible but the above
production of ammoniac may be occasioned by the decomposition of the
potash.
TABLE _of the Combinations of Acetic Acid with the Salifiable Bases, in
the order of affinity._
_Bases._ _Neutral Salts._
Barytes Acetat of barytes.
Potash potash.
Soda soda.
Lime lime.
Magnesia magnesia.
Ammoniac ammoniac.
Oxyd of zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
arsenic arsenic.
bismuth bismuth.
mercury mercury.
antimony antimony.
silver silver.
gold gold.
platina platina.
Argill argill.
_Note._--All these salts were unknown to the ancients; and even those
chemists who are most versant in modern discoveries, are yet at a lose
whether the greater part of the salts produced by the oxygenated acetic
radical belong properly to the class of acetites, or to that of
acetats.--A.
SECT. XXXIV.--_Observations upon Acetic Acid, and its Combinations._
We have given to radical vinegar the name of acetic acid, from supposing
that it consists of the same radical with that of the acetous acid, but
more highly saturated with oxygen. According to this idea, acetic acid
is the highest degree of oxygenation of which the hydro-carbonous
radical is susceptible; but, although this circumstance be extremely
probable, it requires to be confirmed by farther, and more decisive
experiments, before it be adopted as an absolute chemical truth. We
procure this acid as follows: Upon three parts acetite of potash or of
copper, pour one part of concentrated sulphuric acid, and, by
distillation, a very highly concentrated vinegar is obtained, which we
call acetic acid, formerly named radical vinegar. It is not hitherto
rigorously proved that this acid is more highly oxygenated than the
acetous acid, nor that the difference between them may not consist in a
different proportion between the elements of the radical or base.
TABLE _of the Combinations of Succinic Acid with the Salifiable Bases,
in the order of Affinity._
_Bases._ _Neutral Salts._
Barytes Succinat of barytes.
Lime lime.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Magnesia magnesia.
Argill argill.
Oxyd of zinc zinc.
iron iron.
manganese manganese.
cobalt cobalt.
nickel nickel.
lead lead.
tin tin.
copper copper.
bismuth bismuth.
antimony antimony.
arsenic arsenic.
mercury mercury.
silver silver.
gold gold.
platina platina.
_Note._--All the succinats were unknown to the ancient chemists.--A.
SECT. XXXV.--_Observations upon Succinic Acid, and its Combinations._
The succinic acid is drawn from amber by sublimation in a gentle heat,
and rises in a concrete form into the neck of the subliming vessel. The
operation must not be pushed too far, or by too strong a fire, otherwise
the oil of the amber rises alongst with the acid. The salt is dried upon
blotting paper, and purified by repeated solution and crystallization.
This acid is soluble in twenty-four times its weight of cold water, and
in a much smaller quantity of hot water. It possesses the qualities of
an acid in a very small degree, and only affects the blue vegetable
colours very slightly. The affinities of this acid, with the salifiable
bases, are taken from Mr de Morveau, who is the first chemist that has
endeavoured to ascertain them.
SECT. XXXVI.--_Observations upon Benzoic Acid, and its Combinations with
Salifiable Bases[48]._
This acid was known to the ancient chemists under the name of Flowers of
Benjamin, or of Benzoin, and was procured, by sublimation, from the gum
or resin called Benzoin: The means of procuring it, _via humida_, was
discovered by Mr Geoffroy, and perfected by Mr Scheele. Upon benzoin,
reduced to powder, pour strong lime-water, having rather an excess of
lime; keep the mixture continually stirring, and, after half an hour's
digestion, pour off the liquor, and use fresh portions of lime-water in
the same manner, so long as there is any appearance of neutralization.
Join all the decanted liquors, and evaporate, as far as possible,
without occasioning cristallization, and, when the liquor is cold, drop
in muriatic acid till no more precipitate is formed. By the former part
of the process a benzoat of lime is formed, and, by the latter, the
muriatic acid combines with the lime, forming muriat of lime, which
remains dissolved, while the benzoic acid, being insoluble,
precipitates in a concrete state.
SECT. XXXVII.--_Observations upon Camphoric Acid, and its Combinations
with Salifiable Bases[49]._
Camphor is a concrete essential oil, obtained, by sublimation, from a
species of laurus which grows in China and Japan. By distilling nitric
acid eight times from camphor, Mr Kosegarten converted it into an acid
analogous to the oxalic; but, as it differs from that acid in some
circumstances, we have thought necessary to give it a particular name,
till its nature be more completely ascertained by farther experiment.
As camphor is a carbono-hydrous or hydro-carbonous radical, it is easily
conceived, that, by oxygenation, it should form oxalic, malic, and
several other vegetable acids: This conjecture is rendered not
improbable by the experiments of Mr Kosegarten; and the principal
phenomena exhibited in the combinations of camphoric acid with the
salifiable bases, being very similar to those of the oxalic and malic
acids, lead me to believe that it consists of a mixture of these two
acids.
SECT. XXXVIII.--_Observations upon Gallic Acid, and its Combinations
with Salifiable Bases[50]._
The Gallic acid, formerly called Principle of Astringency, is obtained
from gall nuts, either by infusion or decoction with water, or by
distillation with a very gentle heat. This acid has only been attended
to within these few years. The Committee of the Dijon Academy have
followed it through all its combinations, and give the best account of
it hitherto produced. Its acid properties are very weak; it reddens the
tincture of turnsol, decomposes sulphurets, and unites to all the metals
when they have been previously dissolved in some other acid. Iron, by
this combination, is precipitated of a very deep blue or violet colour.
The radical of this acid, if it deserves the name of one, is hitherto
entirely unknown; it is contained in oak willow, marsh iris, the
strawberry, nymphea, Peruvian bark, the flowers and bark of pomgranate,
and in many other woods and barks.
SECT. XXXIX.--_Observations upon Lactic Acid, and its Combinations with
Salifiable Bases[51]._
The only accurate knowledge we have of this acid is from the works of Mr
Scheele. It is contained in whey, united to a small quantity of earth,
and is obtained as follows: Reduce whey to one eighth part of its bulk
by evaporation, and filtrate, to separate all its cheesy matter; then
add as much lime as is necessary to combine with the acid; the lime is
afterwards disengaged by the addition of oxalic acid, which combines
with it into an insoluble neutral salt. When the oxalat of lime has been
separated by decantation, evaporate the remaining liquor to the
consistence of honey; the lactic acid is dissolved by alkohol, which
does not unite with the sugar of milk and other foreign matters; these
are separated by filtration from the alkohol and acid; and the alkohol
being evaporated, or distilled off, leaves the lactic acid behind.
This acid unites with all the salifiable bases forming salts which do
not cristallize; and it seems considerably to resemble the acetous
acid.
TABLE _of the Combinations of Saccholactic Acid with the Salifiable
Bases, in the Order of Affinity._
_Bases._ _Neutral Salts._
Lime Saccholat of lime.
Barytes barytes.
Magnesia magnesia.
Potash potash.
Soda soda.
Ammoniac ammoniac.
Argill argill.
Oxyd of zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
arsenic arsenic.
bismuth bismuth.
mercury mercury.
antimony antimony.
silver silver.
_Note._--All these were unknown to the ancient chemists.--A.
SECT. XL.--_Observations upon Saccholactic Acid, and its Combinations._
A species of sugar may be extracted, by evaporation, from whey, which
has long been known in pharmacy, and which has a considerable
resemblance to that procured from sugar canes. This saccharine matter,
like ordinary sugar, may be oxygenated by means of nitric acid: For this
purpose, several portions of nitric acid are distilled from it; the
remaining liquid is evaporated, and set to cristallize, by which means
cristals of oxalic acid are procured; at the same time a very fine white
powder precipitates, which is the saccholactic acid discovered by
Scheele. It is susceptible of combining with the alkalies, ammoniac, the
earths, and even with the metals: Its action upon the latter is hitherto
but little known, except that, with them, it forms difficultly soluble
salts. The order of affinity in the table is taken from Bergman.
TABLE _of the Combinations of Formic Acid, with the Salifiable Bases, in
the Order of Affinity._
_Bases._ _Neutral Salts._
Barytes Formiat of barytes.
Potash potash.
Soda soda.
Lime lime.
Magnesia magnesia.
Ammoniac ammoniac.
Oxyd of
zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
bismuth bismuth.
silver silver.
Argill argill.
_Note._--All unknown to the ancient chemists.--A.
SECT. XLI.--_Observations upon Formic Acid, and its Combinations._
This acid was first obtained by distillation from ants, in the last
century, by Samuel Fisher. The subject was treated of by Margraff in
1749, and by Messrs Ardwisson and Ochrn of Leipsic in 1777. The formic
acid is drawn from a large species of red ants, _formica rufa, Lin._
which form large ant hills in woody places. It is procured, either by
distilling the ants with a gentle heat in a glass retort or an alembic;
or, after having washed the ants in cold water, and dried them upon a
cloth, by pouring on boiling water, which dissolves the acid; or the
acid may be procured by gentle expression from the insects, in which
case it is stronger than in any of the former ways. To obtain it pure,
we must rectify, by means of distillation, which separates it from the
uncombined oily and charry matter; and it may be concentrated by
freezing, in the manner recommended for treating the acetous acid.
SECT. XLII.--_Observations upon Bombic Acid, and its Combinations with
Acidifiable Bases[52]._
The juices of the silk worm seem to assume an acid quality when that
insect changes from a larva to a chrysalis. At the moment of its escape
from the latter to the butterfly form, it emits a reddish liquor which
reddens blue paper, and which was first attentively observed by Mr
Chaussier of the Dijon academy, who obtains the acid by infusing silk
worm chrysalids in alkohol, which dissolves their acid without being
charged with any of the gummy parts of the insect; and, by evaporating
the alkohol, the acid remains tollerably pure. The properties and
affinities of this acid are not hitherto ascertained with any precision;
and we have reason to believe that analogous acids may be procured from
other insects. The radical of this acid is probably, like that of the
other acids from the animal kingdom, composed of charcoal, hydrogen, and
azote, with the addition, perhaps, of phosphorus.
TABLE _of the Combinations of Sebacic Acid, with the Salifiable Bases,
in the Order of Affinity._
_Bases._ _Neutral Salts._
Barytes Sebat of barytes.
Potash potash.
Soda soda.
Lime lime.
Magnesia magnesia.
Ammoniac ammoniac.
Argill argill.
Oxyd of
zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
arsenic arsenic.
bismuth bismuth.
mercury mercury.
antimony antimony.
silver silver.
_Note._--All these were unknown to the ancient chemists.--A.
SECT. XLIII.--_Observations upon Sebacid Acid, and its Combinations._
To obtain the sebacic acid, let some suet be melted in a skillet over
the fire, alongst with some quick-lime in fine powder, and constantly
stirred, raising the fire towards the end of the operation, and taking
care to avoid the vapours, which are very offensive. By this process the
sebacic acid unites with the lime into a sebat of lime, which is
difficultly soluble in water; it is, however, separated from the fatty
matters with which it is mixed by solution in a large quantity of
boiling water. From this the neutral salt is separated by evaporation;
and, to render it pure, is calcined, redissolved, and again
cristallized. After this we pour on a proper quantity of sulphuric acid,
and the sebacic acid passes over by distillation.
SECT. XLIV.--_Observations upon the Lithic Acid, and its Combinations
with the Salifiable Bases[53]._
From the later experiments of Bergman and Scheele, the urinary calculus
appears to be a species of salt with an earthy basis; it is slightly
acidulous, and requires a large quantity of water for solution, three
grains being scarcely soluble in a thousand grains of boiling water, and
the greater part again cristallizes when cold. To this concrete acid,
which Mr de Morveau calls Lithiasic Acid, we give the name of Lithic
Acid, the nature and properties of which are hitherto very little known.
There is some appearance that it is an acidulous neutral salt, or acid
combined in excess with a salifiable base; and I have reason to believe
that it really is an acidulous phosphat of lime; if so, it must be
excluded from the class of peculiar acids.
TABLE _of the Combinations of the Prussic Acid with the Salifiable
Bases, in the order of affinity._
_Bases._ _Neutral Salts._
Potash Prussiat of potash.
Soda soda.
Ammoniac ammoniac.
Lime lime.
Barytes barytes.
Magnesia magnesia.
Oxyd of zinc zinc.
iron iron.
manganese manganese.
cobalt cobalt.
nickel nickel.
lead lead.
tin tin.
copper copper.
bismuth bismuth.
antimony antimony.
arsenic arsenic.
silver silver.
mercury mercury.
gold gold.
platina platina.
_Note._---All these were unknown to former chemists.--A.
_Observations upon the Prussic Acid, and its Combinations._
As the experiments which have been made hitherto upon this acid seem
still to leave a considerable degree of uncertainty with regard to its
nature, I shall not enlarge upon its properties, and the means of
procuring it pure and dissengaged from combination. It combines with
iron, to which it communicates a blue colour, and is equally susceptible
of entering into combination with most of the other metals, which are
precipitated from it by the alkalies, ammoniac, and lime, in consequence
of greater affinity. The Prussic radical, from the experiments of
Scheele, and especially from those of Mr Berthollet, seems composed of
charcoal and azote; hence it is an acid with a double base. The
phosphorus which has been found combined with it appears, from the
experiments of Mr Hassenfratz, to be only accidental.
Although this acid combines with alkalies, earths, and metals, in the
same way with other acids, it possesses only some of the properties we
have been in use to attribute to acids, and it may consequently be
improperly ranked here in the class of acids; but, as I have already
observed, it is difficult to form a decided opinion upon the nature of
this substance until the subject has been farther elucidated by a
greater number of experiments.
FOOTNOTES:
[36] See Memoirs of the Academy for 1776, p. 671. and for 1778, p.
535,--A.
[37] See Part I. Chap. XI. upon this subject.--A.
[38] See Part I. Chap. XI. upon the application of these names according
to the proportions of the two ingredients.--A
[39] See Part I. Chap. XII. upon this subject.--A.
[40] Those who wish to see what has been said upon this great chemical
question by Messrs de Morveau, Berthollet, De Fourcroy, and myself, may
consult our translation of Mr Kirwan's Essay upon Phlogiston.--A.
[41] Saltpetre is likewise procured in large quantities by lixiviating
the natural soil in some parts of Bengal, and of the Russian Ukrain.--E.
[42] Commonly called _Derbyshire spars_.--E.
[43] I have not added the Table of these combinations, as the order of
their affinity is entirely unknown; they are called _molybdats of
argil_, _antimony_, _potash_, &c.--E.
[44] This acid was discovered by Mr Scheele, to whom chemistry is
indebted for the discovery of several other acids.--A.
[45] I have omitted the Table, as the order of affinity is unknown, and
is given by Mr Lavoisier only in alphabetical order. All the
combinations of malic acid with salifiable bases, which are named
_malats_, were unknown to the ancient chemists.--E.
[46] The order of affinity of the salifiable bases with this acid is
hitherto unknown. Mr Lavoisier, from its similarity to pyro-lignous
acid, supposes the order to be the same in both; but, as this is not
ascertained by experiment, the table is omitted. All these combinations,
called _Pyro-tartarites_, were unknown till lately--E.
[47] Savans Etrangers, Vol. III.
[48] These combinations are called Benzoats of Lime, Potash, Zinc, &c.;
but, as the order of affinity is unknown, the alphabetical table is
omitted, as unnecessary.--E.
[49] These combinations, which were all unknown to the ancients, are
called Camphorats. The table is omitted, as being only in alphabetical
order.--E.
[50] These combinations, which are called Gallats, were all unknown to
the ancients; and the order of their affinity is not hitherto
established.--A.
[51] These combinations are called Lactats; they were all unknown to the
ancient chemists, and their affinities have not yet been
ascertained.--A.
[52] These combinations named Bombats were unknown to the ancient
chemists; and the affinities of the salifiable bases with the bombic
acid are hitherto undetermined.--A.
[53] All the combinations of this acid, should it finally turn out to be
one, were unknown to the ancient chemists, and its affinities with the
salifiable bases have not been hitherto determined.--A.
PART III.
Description of the Instruments and Operations of Chemistry.
INTRODUCTION.
In the two former parts of this work I designedly avoided being
particular in describing the manual operations of chemistry, because I
had found from experience, that, in a work appropriated to reasoning,
minute descriptions of processes and of plates interrupt the chain of
ideas, and render the attention necessary both difficult and tedious to
the reader. On the other hand, if I had confined myself to the summary
descriptions hitherto given, beginners could have only acquired very
vague conceptions of practical chemistry from my work, and must have
wanted both confidence and interest in operations they could neither
repeat nor thoroughly comprehend. This want could not have been
supplied from books; for, besides that there are not any which describe
the modern instruments and experiments sufficiently at large, any work
that could have been consulted would have presented these things under a
very different order of arrangement, and in a different chemical
language, which must greatly tend to injure the main object of my
performance.
Influenced by these motives, I determined to reserve, for a third part
of my work, a summary description of all the instruments and
manipulations relative to elementary chemistry. I considered it as
better placed at the end, rather than at the beginning of the book,
because I must have been obliged to suppose the reader acquainted with
circumstances which a beginner cannot know, and must therefore have read
the elementary part to become acquainted with. The whole of this third
part may therefore be considered as resembling the explanations of
plates which are usually placed at the end of academic memoirs, that
they may not interrupt the connection of the text by lengthened
description. Though I have taken great pains to render this part clear
and methodical, and have not omitted any essential instrument or
apparatus, I am far from pretending by it to set aside the necessity of
attendance upon lectures and laboratories, for such as wish to acquire
accurate knowledge of the science of chemistry. These should familiarise
themselves to the employment of apparatus, and to the performance of
experiments by actual experience. _Nihil est in intellectu quod non
prius fuerit in sensu_, the motto which the celebrated Rouelle caused to
be painted in large characters in a conspicuous part of his laboratory,
is an important truth never to be lost sight of either by teachers or
students of chemistry.
Chemical operations may be naturally divided into several classes,
according to the purposes they are intended for performing. Some may be
considered as purely mechanical, such as the determination of the weight
and bulk of bodies, trituration, levigation, searching, washing,
filtration, &c. Others may be considered as real chemical operations,
because they are performed by means of chemical powers and agents; such
are solution, fusion, &c. Some of these are intended for separating the
elements of bodies from each other, some for reuniting these elements
together; and some, as combustion, produce both these effects during the
same process.
Without rigorously endeavouring to follow the above method, I mean to
give a detail of the chemical operations in such order of arrangement as
seemed best calculated for conveying instruction. I shall be more
particular in describing the apparatus connected with modern chemistry,
because these are hitherto little known by men who have devoted much of
their time to chemistry, and even by many professors of the science.
CHAP. I.
_Of the Instruments necessary for determining the Absolute and Specific
Gravities of Solid and Liquid Bodies._
The best method hitherto known for determining the quantities of
substances submitted to chemical experiment, or resulting from them, is
by means of an accurately constructed beam and scales, with properly
regulated weights, which well known operation is called _weighing_. The
denomination and quantity of the weights used as an unit or standard for
this purpose are extremely arbitrary, and vary not only in different
kingdoms, but even in different provinces of the same kingdom, and in
different cities of the same province. This variation is of infinite
consequence to be well understood in commerce and in the arts; but, in
chemistry, it is of no moment what particular denomination of weight be
employed, provided the results of experiments be expressed in convenient
fractions of the same denomination. For this purpose, until all the
weights used in society be reduced to the same standard, it will be
sufficient for chemists in different parts to use the common pound of
their own country as the unit or standard, and to express all its
fractional parts in decimals, instead of the arbitrary divisions now in
use. By this means the chemists of all countries will be thoroughly
understood by each other, as, although the absolute weights of the
ingredients and products cannot be known, they will readily, and without
calculation, be able to determine the relative proportions of these to
each other with the utmost accuracy; so that in this way we shall be
possessed of an universal language for this part of chemistry.
With this view I have long projected to have the pound divided into
decimal fractions, and I have of late succeeded through the assistance
of Mr Fourche balance-maker at Paris, who has executed it for me with
great accuracy and judgment. I recommend to all who carry on experiments
to procure similar divisions of the pound, which they will find both
easy and simple in its application, with a very small knowledge of
decimal fractions[54].
As the usefulness and accuracy of chemistry depends entirely upon the
determination of the weights of the ingredients and products both before
and after experiments, too much precision cannot be employed in this
part of the subject; and, for this purpose, we must be provided with
good instruments. As we are often obliged, in chemical processes, to
ascertain, within a grain or less, the tare or weight of large and heavy
instruments, we must have beams made with peculiar niceness by accurate
workmen, and these must always be kept apart from the laboratory in some
place where the vapours of acids, or other corrosive liquors, cannot
have access, otherwise the steel will rust, and the accuracy of the
balance be destroyed. I have three sets, of different sizes, made by Mr
Fontin with the utmost nicety, and, excepting those made by Mr Ramsden
of London, I do not think any can compare with them for precision and
sensibility. The largest of these is about three feet long in the beam
for large weights, up to fifteen or twenty pounds; the second, for
weights of eighteen or twenty ounces, is exact to a tenth part of a
grain; and the smallest, calculated only for weighing about one gros, is
sensibly affected by the five hundredth part of a grain.
Besides these nicer balances, which are only used for experiments of
research, we must have others of less value for the ordinary purposes
of the laboratory. A large iron balance, capable of weighing forty or
fifty pounds within half a dram, one of a middle size, which may
ascertain eight or ten pounds, within ten or twelve grains, and a small
one, by which about a pound may be determined, within one grain.
We must likewise be provided with weights divided into their several
fractions, both vulgar and decimal, with the utmost nicety, and verified
by means of repeated and accurate trials in the nicest scales; and it
requires some experience, and to be accurately acquainted with the
different weights, to be able to use them properly. The best way of
precisely ascertaining the weight of any particular substance is to
weigh it twice, once with the decimal divisions of the pound, and
another time with the common subdivisions or vulgar fractions, and, by
comparing these, we attain the utmost accuracy.
By the specific gravity of any substance is understood the quotient of
its absolute weight divided by its magnitude, or, what is the same, the
weight of a determinate bulk of any body. The weight of a determinate
magnitude of water has been generally assumed as unity for this purpose;
and we express the specific gravity of gold, sulphuric acid, &c. by
saying, that gold is nineteen times, and sulphuric acid twice the weight
of water, and so of other bodies.
It is the more convenient to assume water as unity in specific
gravities, that those substances whose specific gravity we wish to
determine, are most commonly weighed in water for that purpose. Thus, if
we wish to determine the specific gravity of gold flattened under the
hammer, and supposing the piece of gold to weigh 8 oz. 4 gros 2-1/2
grs. in the air[55], it is suspended by means of a fine metallic wire
under the scale of a hydrostatic balance, so as to be entirely immersed
in water, and again weighed. The piece of gold in Mr Brisson's
experiment lost by this means 3 gros 37 grs.; and, as it is evident
that the weight lost by a body weighed in water is precisely equal to
the weight of the water displaced, or to that of an equal volume of
water, we may conclude, that, in equal magnitudes, gold weighs 4893-1/2
grs. and water 253 grs. which, reduced to unity, gives 1.0000 as the
specific gravity of water, and 19.3617 for that of gold. We may operate
in the same manner with all solid substances. We have rarely any
occasion, in chemistry, to determine the specific gravity of solid
bodies, unless when operating upon alloys or metallic glasses; but we
have very frequent necessity to ascertain that of fluids, as it is often
the only means of judging of their purity or degree of concentration.
This object may be very fully accomplished with the hydrostatic balance,
by weighing a solid body; such, for example, as a little ball of rock
cristal suspended by a very fine gold wire, first in the air, and
afterwards in the fluid whose specific gravity we wish to discover. The
weight lost by the cristal, when weighed in the liquor, is equal to that
of an equal bulk of the liquid. By repeating this operation successively
in water and different fluids, we can very readily ascertain, by a
simple and easy calculation, the relative specific gravities of these
fluids, either with respect to each other or to water. This method is
not, however, sufficiently exact, or, at least, is rather troublesome,
from its extreme delicacy, when used for liquids differing but little in
specific gravity from water; such, for instance, as mineral waters, or
any other water containing very small portions of salt in solution.
In some operations of this nature, which have not hitherto been made
public, I employed an instrument of great sensibility for this purpose
with great advantage. It consists of a hollow cylinder, A b c f, Pl.
vii. fig. 6. of brass, or rather of silver, loaded at its bottom, b c f,
with tin, as represented swimming in a jug of water, l m n o. To the
upper part of the cylinder is attached a stalk of silver wire, not more
than three fourths of a line diameter, surmounted by a little cup d,
intended for containing weights; upon the stalk a mark is made at g,
the use of which we shall presently explain. This cylinder may be made
of any size; but, to be accurate, ought at least to displace four pounds
of water. The weight of tin with which this instrument is loaded ought
to be such as will make it remain almost in equilibrium in distilled
water, and should not require more than half a dram, or a dram at most,
to make it sink to g.
We must first determine, with great precision, the exact weight of the
instrument, and the number of additional grains requisite for making it
sink, in distilled water of a determinate temperature, to the mark: We
then perform the same experiment upon all the fluids of which we wish to
ascertain the specific gravity, and, by means of calculation, reduce the
observed differences to a common standard of cubic feet, pints or
pounds, or of decimal fractions, comparing them with water. This method,
joined to experiments with certain reagents[56], is one of the best for
determining the quality of waters, and is even capable of pointing out
differences which escape the most accurate chemical analysis. I shall,
at some future period, give an account of a very extensive set of
experiments which I have made upon this subject.
These metallic hydrometers are only to be used for determining the
specific gravities of such waters as contain only neutral salts or
alkaline substances; and they may be constructed with different degrees
of ballast for alkohol and other spiritous liquors. When the specific
gravities of acid liquors are to be ascertained, we must use a glass
hydrometer, as represented Pl. vii. fig. 14[57]. This consists of a
hollow cylinder of glass, a b c f, hermetically sealed at its lower
end, and drawn out at the upper into a capillary tube a, ending in the
little cup or bason d. This instrument is ballasted with more or less
mercury, at the bottom of the cylinder introduced through the tube, in
proportion to the weight of the liquor intended to be examined: We may
introduce a small graduated slip of paper into the tube a d; and,
though these degrees do not exactly correspond to the fractions of
grains in the different liquors, they may be rendered very useful in
calculation.
What is said in this chapter may suffice, without farther enlargement,
for indicating the means of ascertaining the absolute and specific
gravities of solids and fluids, as the necessary instruments are
generally known, and may easily be procured: But, as the instruments I
have used for measuring the gasses are not any where described, I shall
give a more detailed account of these in the following chapter.
FOOTNOTES:
[54] Mr Lavoisier gives, in this part of his work, very accurate
directions for reducing the common subdivisions of the French pound into
decimal fractions, and _vice versa_, by means of tables subjoined to
this 3d part. As these instructions, and the table, would be useless to
the British chemist, from the difference between the subdivisions of the
French and Troy pounds, I have omitted them, but have subjoined in the
appendix accurate rules for converting the one into the other.--E.
[55] Vide Mr Brisson's Essay upon Specific Gravity, p. 5.--A.
[56] For the use of these reagents see Bergman's excellent treatise upon
the analysis of mineral waters, in his Chemical and Physical Essays.--E.
[57] Three or four years ago, I have seen similar glass hydrometers,
made for Dr Black by B. Knie, a very ingenious artist of this city.--E.
CHAP. II.
_Of Gazometry, or the Measurement of the Weight and Volume of Aëriform
Substances._
SECT. I.
_Description of the Pneumato-chemical Apparatus._
The French chemists have of late applied the name of _pneumato-chemical
apparatus_ to the very simple and ingenious contrivance, invented by Dr
Priestley, which is now indispensibly necessary to every laboratory.
This consists of a wooden trough, of larger or smaller dimensions as is
thought convenient, lined with plate-lead or tinned copper, as
represented in perspective, Pl. V. In Fig. 1. the same trough or cistern
is supposed to have two of its sides cut away, to show its interior
construction more distinctly. In this apparatus, we distinguish between
the shelf ABCD Fig. 1. and 2. and the bottom or body of the cistern FGHI
Fig. 2. The jars or bell-glasses are filled with water in this deep
part, and, being turned with their mouths downwards, are afterwards set
upon the shelf ABCD, as shown Plate X. Fig. 1. F. The upper parts of the
sides of the cistern above the level of the shelf are called the _rim_
or _borders_.
The cistern ought to be filled with water, so as to stand at least an
inch and a half deep upon the shelf, and it should be of such dimensions
as to admit of at least one foot of water in every direction in the
well. This size is sufficient for ordinary occasions; but it is often
convenient, and even necessary, to have more room; I would therefore
advise such as intend to employ themselves usefully in chemical
experiments, to have this apparatus made of considerable magnitude,
where their place of operating will allow. The well of my principal
cistern holds four cubical feet of water, and its shelf has a surface of
fourteen square feet; yet, in spite of this size, which I at first
thought immoderate, I am often straitened for room.
In laboratories, where a considerable number of experiments are
performed, it is necessary to have several lesser cisterns, besides the
large one, which may be called the _general magazine_; and even some
portable ones, which may be moved when necessary, near a furnace, or
wherever they may be wanted. There are likewise some operations which
dirty the water of the apparatus, and therefore require to be carried
on in cisterns by themselves.
It were doubtless considerably cheaper to use cisterns, or iron-bound
tubs, of wood simply dove-tailed, instead of being lined with lead or
copper; and in my first experiments I used them made in that way; but I
soon discovered their inconvenience. If the water be not always kept at
the same level, such of the dovetails as are left dry shrink, and, when
more water is added, it escapes through the joints, and runs out.
We employ cristal jars or bell glasses, Pl. V. Fig. 9. A. for containing
the gasses in this apparatus; and, for transporting these, when full of
gas, from one cistern to another, or for keeping them in reserve when
the cistern is too full, we make use of a flat dish BC, surrounded by a
standing up rim or border, with two handles DE for carrying it by.
After several trials of different materials, I have found marble the
best substance for constructing the mercurial pneumato-chemical
apparatus, as it is perfectly impenetrable by mercury, and is not
liable, like wood, to separate at the junctures, or to allow the mercury
to escape through chinks; neither does it run the risk of breaking, like
glass, stone-ware, or porcelain. Take a block of marble BCDE, Plate V.
Fig. 3. and 4. about two feet long, 15 or 18 inches broad, and ten
inches thick, and cause it to be hollowed out as at m n Fig. 5. about
four inches deep, as a reservoir for the mercury; and, to be able more
conveniently to fill the jars, cut the gutter T V, Fig. 3. 4. and 5. at
least four inches deeper; and, as this trench may sometimes prove
troublesome, it is made capable of being covered at pleasure by thin
boards, which slip into the grooves x y, Fig. 5. I have two marble
cisterns upon this construction, of different sizes, by which I can
always employ one of them as a reservoir of mercury, which it preserves
with more safety than any other vessel, being neither subject to
overturn, nor to any other accident. We operate with mercury in this
apparatus exactly as with water in the one before described; but the
bell-glasses must be of smaller diameter, and much stronger; or we may
use glass tubes, having their mouths widened, as in Fig. 7.; these are
called _eudiometers_ by the glass-men who sell them. One of the
bell-glasses is represented Fig. 5. A. standing in its place, and what
is called a jar is engraved Fig. 6.
The mercurial pneumato-chemical apparatus is necessary in all
experiments wherein the disengaged gasses are capable of being absorbed
by water, as is frequently the case, especially in all combinations,
excepting those of metals, in fermentation, &c.
SECT. II.
_Of the Gazometer._
I give the name of _gazometer_ to an instrument which I invented, and
caused construct, for the purpose of a kind of bellows, which might
furnish an uniform and continued stream of oxygen gas in experiments of
fusion. Mr Meusnier and I have since made very considerable corrections
and additions, having converted it into what may be called an _universal
instrument_, without which it is hardly possible to perform most of the
very exact experiments. The name we have given the instrument indicates
its intention for measuring the volume or quantity of gas submitted to
it for examination.
It consists of a strong iron beam, DE, Pl. VIII. Fig. 1. three feet
long, having at each end, D and E, a segment of a circle, likewise
strongly constructed of iron, and very firmly joined. Instead of being
poised as in ordinary balances, this beam rests, by means of a
cylindrical axis of polished steel, F, Fig. 9. upon two large moveable
brass friction-wheels, by which the resistance to its motion from
friction is considerably diminished, being converted into friction of
the second order. As an additional precaution, the parts of these wheels
which support the axis of the beam are covered with plates of polished
rock-cristal. The whole of this machinery is fixed to the top of the
solid column of wood BC, Fig. 1. To one extremity D of the beam, a scale
P for holding weights is suspended by a flat chain, which applies to the
curvature of the arc nDo, in a groove made for the purpose. To the
other extremity E of the beam is applied another flat chain, i k m, so
constructed, as to be incapable of lengthening or shortening, by being
less or more charged with weight; to this chain, an iron trivet, with
three branches, a i, c i, and h i, is strongly fixed at i, and
these branches support a large inverted jar A, of hammered copper, of
about 18 inches diameter, and 20 inches deep. The whole of this machine
is represented in perspective, Pl. VIII. Fig. 1. and Pl. IX. Fig. 2. and
4. give perpendicular sections, which show its interior structure.
Round the bottom of the jar, on its outside, is fixed (Pl. IX. Fig. 2.)
a border divided into compartments 1, 2, 3, 4, &c. intended to receive
leaden weights separately represented 1, 2, 3, Fig. 3. These are
intended for increasing the weight of the jar when a considerable
pressure is requisite, as will be afterwards explained, though such
necessity seldom occurs. The cylindrical jar A is entirely open below,
de, Pl. IX. Fig. 4.; but is closed above with a copper lid, a b c,
open at b f, and capable of being shut by the cock g. This lid, as may
be seen by inspecting the figures, is placed a few inches within the top
of the jar to prevent the jar from being ever entirely immersed in the
water, and covered over. Were I to have this instrument made over again,
I should cause the lid to be considerably more flattened, so as to be
almost level. This jar or reservoir of air is contained in the
cylindrical copper vessel, LMNO, Pl. VIII. Fig. 1. filled with water.
In the middle of the cylindrical vessel LMNO, Pl. IX. Fig. 4. are placed
two tubes st, xy, which are made to approach each other at their upper
extremities t y; these are made of such a length as to rise a little
above the upper edge LM of the vessel LMNO, and when the jar abcde
touches the bottom NO, their upper ends enter about half an inch into
the conical hollow b, leading to the stop-cock g.
The bottom of the vessel LMNO is represented Pl. IX. Fig. 3. in the
middle of which a small hollow semispherical cap is soldered, which may
be considered as the broad end of a funnel reversed; the two tubes st,
xy, Fig. 4. are adapted to this cap at s and x, and by this means
communicate with the tubes mm, nn, oo, pp, Fig. 3. which are fixed
horizontally upon the bottom of the vessel, and all of which terminate
in, and are united by, the spherical cap sx. Three of these tubes are
continued out of the vessel, as in Pl. VIII. Fig. 1. The first marked in
that figure 1, 2, 3, is inserted at its extremity 3, by means of an
intermediate stop-cock 4, to the jar V. which stands upon the shelf of a
small pneumato-chemical apparatus GHIK, the inside of which is shown Pl.
IX. Fig. 1. The second tube is applied against the outside of the vessel
LMNO from 6 to 7, is continued at 8, 9, 10, and at 11 is engaged below
the jar V. The former of these tubes is intended for conveying gas into
the machine, and the latter for conducting small quantities for trials
under jars. The gas is made either to flow into or out of the machine,
according to the degree of pressure it receives; and this pressure is
varied at pleasure, by loading the scale P less or more, by means of
weights. When gas is to be introduced into the machine, the pressure is
taken off, or even rendered negative; but, when gas is to be expelled, a
pressure is made with such degree of force as is found necessary.
The third tube 12, 13, 14, 15, is intended for conveying air or gas to
any necessary place or apparatus for combustions, combinations, or any
other experiment in which it is required.
To explain the use of the fourth tube, I must enter into some
discussions. Suppose the vessel LMNO, Pl. VIII. Fig. 1. full of water,
and the jar A partly filled with gas, and partly with water; it is
evident that the weights in the bason P may be so adjusted, as to
occasion an exact equilibrium between the weight of the bason and of the
jar, so that the external air shall not tend to enter into the jar, nor
the gas to escape from it; and in this case the water will stand exactly
at the same level both within and without the jar. On the contrary, if
the weight in the bason P be diminished, the jar will then press
downwards from its own gravity, and the water will stand lower within
the jar than it does without; in this case, the included air or gas will
suffer a degree of compression above that experienced by the external
air, exactly proportioned to the weight of a column of water, equal to
the difference of the external and internal surfaces of the water. From
these reflections, Mr Meusnier contrived a method of determining the
exact degree of pressure to which the gas contained in the jar is at any
time exposed. For this purpose, he employs a double glass syphon 19, 20,
21, 22, 23, firmly cemented at 19 and 23. The extremity 19 of this
syphon communicates freely with the water in the external vessel of the
machine, and the extremity 23 communicates with the fourth tube at the
bottom of the cylindrical vessel, and consequently, by means of the
perpendicular tube st, Pl. IX. Fig. 4. with the air contained in the
jar. He likewise cements, at 16, Pl. VIII. Fig. 1. another glass tube
16, 17, 18, which communicates at 16 with the water in the exterior
vessel LMNO, and, at its upper end 18, is open to the external air.
By these several contrivances, it is evident that the water must stand
in the tube 16, 17, 18, at the same level with that in the cistern LMNO;
and, on the contrary, that, in the branch 19, 20, 21, it must stand
higher or lower, according as the air in the jar is subjected to a
greater or lesser pressure than the external air. To ascertain these
differences, a brass scale divided into inches and lines is fixed
between these two tubes. It is readily conceived that, as air, and all
other elastic fluids, must increase in weight by compression, it is
necessary to know their degree of condensation to be enabled to
calculate their quantities, and to convert the measure of their volumes
into correspondent weights; and this object is intended to be fulfilled
by the contrivance now described.
But, to determine the specific gravity of air or of gasses, and to
ascertain their weight in a known volume, it is necessary to know their
temperature, as well as the degree of pressure under which they subsist;
and this is accomplished by means of a small thermometer, strongly
cemented into a brass collet, which screws into the lid of the jar A.
This thermometer is represented separately, Pl. VIII. Fig. 10. and in
its place 24, 25, Fig. 1. and Pl. IX. Fig. 4. The bulb is in the inside
of the jar A, and its graduated stalk rises on the outside of the lid.
The practice of gazometry would still have laboured under great
difficulties, without farther precautions than those above described.
When the jar A sinks in the water of the cistern LMNO, it must lose a
weight equal to that of the water which it displaces; and consequently
the compression which it makes upon the contained air or gas must be
proportionally diminished. Hence the gas furnished, during experiments
from the machine, will not have the same density towards the end that it
had at the beginning, as its specific gravity is continually
diminishing. This difference may, it is true, be determined by
calculation; but this would have occasioned such mathematical
investigations as must have rendered the use of this apparatus both
troublesome and difficult. Mr Meusnier has remedied this inconvenience
by the following contrivance. A square rod of iron, 26, 27, Pl. VIII.
Fig. 1. is raised perpendicular to the middle of the beam DE. This rod
passes through a hollow box of brass 28, which opens, and may be filled
with lead; and this box is made to slide alongst the rod, by means of a
toothed pinion playing in a rack, so as to raise or lower the box, and
to fix it at such places as is judged proper.
When the lever or beam DE stands horizontal, this box gravitates to
neither side; but, when the jar A sinks into the cistern LMNO, so as to
make the beam incline to that side, it is evident the loaded box 28,
which then passes beyond the center of suspension, must gravitate to the
side of the jar, and augment its pressure upon the included air. This is
increased in proportion as the box is raised towards 27, because the
same weight exerts a greater power in proportion to the length of the
lever by which it acts. Hence, by moving the box 28 alongst the rod 26,
27, we can augment or diminish the correction it is intended to make
upon the pressure of the jar; and both experience and calculation show
that this may be made to compensate very exactly for the loss of weight
in the jar at all degrees of pressure.
I have not hitherto explained the most important part of the use of this
machine, which is the manner of employing it for ascertaining the
quantities of the air or gas furnished during experiments. To determine
this with the most rigorous precision, and likewise the quantity
supplied to the machine from experiments, we fixed to the arc which
terminates the arm of the beam E, Pl. VIII. Fig. 1. the brass sector l
m, divided into degrees and half degrees, which consequently moves in
common with the beam; and the lowering of this end of the beam is
measured by the fixed index 29, 30, which has a Nonius giving hundredth
parts of a degree at its extremity 30.
The whole particulars of the different parts of the above described
machine are represented in Plate VIII. as follow.
Fig. 2. Is the flat chain invented by Mr Vaucanson, and employed for
suspending the scale or bason P, Fig. 1; but, as this lengthens or
shortens according as it is more or less loaded, it would not have
answered for suspending the jar A, Fig. 1.
Fig. 5. Is the chain i k m, which in Fig. 1. sustains the jar A. This
is entirely formed of plates of polished iron interlaced into each
other, and held together by iron pins. This chain does not lengthen in
any sensible degree, by any weight it is capable of supporting.
Fig. 6. The trivet, or three branched stirrup, by which the jar A is
hung to the balance, with the screw by which it is fixed in an
accurately vertical position.
Fig. 3. The iron rod 26, 27, which is fixed perpendicular to the center
of the beam, with its box 28.
Fig. 7. & 8. The friction-wheels, with the plates of rock-cristal Z, as
points of contact by which the friction of the axis of the lever of the
balance is avoided.
Fig. 4. The piece of metal which supports the axis of the
friction-wheels.
Fig. 9. The middle of the lever or beam, with the axis upon which it
moves.
Fig. 10. The thermometer for determining the temperature of the air or
gas contained in the jar.
When this gazometer is to be used, the cistern or external vessel, LMNO,
Pl. VIII. Fig. 1. is to be filled with water to a determinate height,
which should be the same in all experiments. The level of the water
should be taken when the beam of the balance stands horizontal; this
level, when the jar is at the bottom of the cistern, is increased by all
the water which it displaces, and is diminished in proportion as the jar
rises to its highest elevation. We next endeavour, by repeated trials,
to discover at what elevation the box 28 must be fixed, to render the
pressure equal in all situations of the beam. I should have said nearly,
because this correction is not absolutely rigorous; and differences of a
quarter, or even of half a line, are not of any consequence. This height
of the box 28 is not the same for every degree of pressure, but varies
according as this is of one, two, three, or more inches. All these
should be registered with great order and precision.
We next take a bottle which holds eight or ten pints, the capacity of
which is very accurately determined by weighing the water it is capable
of containing. This bottle is turned bottom upwards, full of water, in
the cistern of the pneumato chemical apparatus GHIK, Fig. 1. and is set
on its mouth upon the shelf of the apparatus, instead of the glass jar
V, having the extremity 11 of the tube 7, 8, 9, 10, 11, inserted into
its mouth. The machine is fixed at zero of pressure, and the degree
marked by the index 30 upon the sector m l is accurately observed;
then, by opening the stop-cock 8, and pressing a little upon the jar A,
as much air is forced into the bottle as fills it entirely. The degree
marked by the index upon the sector is now observed, and we calculate
what number of cubical inches correspond to each degree. We then fill a
second and third bottle, and so on, in the same manner, with the same
precautions, and even repeat the operation several times with bottles of
different sizes, till at last, by accurate attention, we ascertain the
exact gage or capacity of the jar A, in all its parts; but it is better
to have it formed at first accurately cylindrical, by which we avoid
these calculations and estimates.
The instrument I have been describing was constructed with great
accuracy and uncommon skill by Mr Meignie junior, engineer and physical
instrument-maker. It is a most valuable instrument, from the great
number of purposes to which it is applicable; and, indeed, there are
many experiments which are almost impossible to be performed without it.
It becomes expensive, because, in many experiments, such as the
formation of water and of nitric acid, it is absolutely necessary to
employ two of the same machines. In the present advanced state of
chemistry, very expensive and complicated instruments are become
indispensibly necessary for ascertaining the analysis and synthesis of
bodies with the requisite precision as to quantity and proportion; it is
certainly proper to endeavour to simplify these, and to render them less
costly; but this ought by no means to be attempted at the expence of
their conveniency of application, and much less of their accuracy.
SECT. III.
_Some other methods of measuring the volume of Gasses._
The gazometer described in the foregoing section is too costly and too
complicated for being generally used in laboratories for measuring the
gasses, and is not even applicable to every circumstance of this kind.
In numerous series of experiments, more simple and more readily
applicable methods must be employed. For this purpose I shall describe
the means I used before I was in possession of a gazometer, and which I
still use in preference to it in the ordinary course of my experiments.
Suppose that, after an experiment, there is a residuum of gas, neither
absorbable by alkali nor water, contained in the upper part of the jar
AEF, Pl. IV. Fig. 3. standing on the shelf of a pneumato-chemical
apparatus, of which we wish to ascertain the quantity, we must first
mark the height to which the mercury or water rises in the jar with
great exactness, by means of slips of paper pasted in several parts
round the jar. If we have been operating in mercury, we begin by
displacing the mercury from the jar, by introducing water in its stead.
This is readily done by filling a bottle quite full of water; having
stopped it with your finger, turn it up, and introduce its mouth below
the edge of the jar; then, turning down its body again, the mercury, by
its gravity, falls into the bottle, and the water rises in the jar, and
takes the place occupied by the mercury. When this is accomplished, pour
so much water into the cistern ABCD as will stand about an inch over the
surface of the mercury; then pass the dish BC, Pl. V. Fig. 9. under the
jar, and carry it to the water cistern, Fig. 1. and 2. We here exchange
the gas into another jar, which has been previously graduated in the
manner to be afterwards described; and we thus judge of the quantity or
volume of the gas by means of the degrees which it occupies in the
graduated jar.
There is another method of determining the volume of gas, which may
either be substituted in place of the one above described, or may be
usefully employed as a correction or proof of that method. After the air
or gas is exchanged from the first jar, marked with slips of paper, into
the graduated jar, turn up the mouth of the marked jar, and fill it with
water exactly to the marks EF, Pl. IV. Fig. 3. and by weighing the water
we determine the volume of the air or gas it contained, allowing one
cubical foot, or 1728 cubical inches, of water for each 70 pounds,
French weight.
The manner of graduating jars for this purpose is very easy, and we
ought to be provided with several of different sizes, and even several
of each size, in case of accidents. Take a tall, narrow, and strong
glass jar, and, having filled it with water in the cistern, Pl. V. Fig.
1. place it upon the shelf ABCD; we ought always to use the same place
for this operation, that the level of the shelf may be always exactly
similar, by which almost the only error to which this process is liable
will be avoided. Then take a narrow mouthed phial which holds exactly 6
oz. 3 gros 61 grs. of water, which corresponds to 10 cubical
inches. If you have not one exactly of this dimension, choose one a
little larger, and diminish its capacity to the size requisite, by
dropping in a little melted wax and rosin. This bottle serves the
purpose of a standard for gaging the jars. Make the air contained in
this bottle pass into the jar, and mark exactly the place to which the
water has descended; add another measure of air, and again mark the
place of the water, and so on, till all the water be displaced. It is of
great consequence that, during the course of this operation, the bottle
and jar be kept at the same temperature with the water in the cistern;
and, for this reason, we must avoid keeping the hands upon either as
much as possible; or, if we suspect they have been heated, we must cool
them by means of the water in the cistern. The height of the barometer
and thermometer during this experiment is of no consequence.
When the marks have been thus ascertained upon the jar for every ten
cubical inches, we engrave a scale upon one of its sides, by means of a
diamond pencil. Glass tubes are graduated in the same manner for using
in the mercurial apparatus, only they must be divided into cubical
inches, and tenths of a cubical inch. The bottle used for gaging these
must hold 8 oz. 6 gros 25 grs. of mercury, which exactly
corresponds to a cubical inch of that metal.
The method of determining the volume of air or gas, by means of a
graduated jar, has the advantage of not requiring any correction for the
difference of height between the surface of the water within the jar,
and in the cistern; but it requires corrections with respect to the
height of the barometer and thermometer. But, when we ascertain the
volume of air by weighing the water which the jar is capable of
containing, up to the marks EF, it is necessary to make a farther
correction, for the difference between the surface of the water in the
cistern, and the height to which it rises within the jar. This will be
explained in the fifth section of this chapter.
SECT. IV.
_Of the method of Separating the different Gasses from each other._
As experiments often produce two, three, or more species of gas, it is
necessary to be able to separate these from each other, that we may
ascertain the quantity and species of each. Suppose that under the jar
A, Pl. IV. Fig. 3. is contained a quantity of different gasses mixed
together, and standing over mercury, we begin by marking with slips of
paper, as before directed, the height at which the mercury stands within
the glass; then introduce about a cubical inch of water into the jar,
which will swim over the surface of the mercury: If the mixture of gas
contains any muriatic or sulphurous acid gas, a rapid and considerable
absorption will instantly take place, from the strong tendency these two
gasses have, especially the former, to combine with, or be absorbed by
water. If the water only produces a slight absorption of gas hardly
equal to its own bulk, we conclude, that the mixture neither contains
muriatic acid, sulphuric acid, or ammoniacal gas, but that it contains
carbonic acid gas, of which water only absorbs about its own bulk. To
ascertain this conjecture, introduce some solution of caustic alkali,
and the carbonic acid gas will be gradually absorbed in the course of a
few hours; it combines with the caustic alkali or potash, and the
remaining gas is left almost perfectly free from any sensible residuum
of carbonic acid gas.
After each experiment of this kind, we must carefully mark the height at
which the mercury stands within the jar, by slips of paper pasted on,
and varnished over when dry, that they may not be washed off when placed
in the water apparatus. It is likewise necessary to register the
difference between the surface of the mercury in the cistern and that in
the jar, and the height of the barometer and thermometer, at the end of
each experiment.
When all the gas or gasses absorbable by water and potash are absorbed,
water is admitted into the jar to displace the mercury; and, as is
described in the preceding section, the mercury in the cistern is to be
covered by one or two inches of water. After this, the jar is to be
transported by means of the flat dish BC, Pl. V. Fig. 9. into the water
apparatus; and the quantity of gas remaining is to be ascertained by
changing it into a graduated jar. After this, small trials of it are to
be made by experiments in little jars, to ascertain nearly the nature of
the gas in question. For instance, into a small jar full of the gas,
Fig. 8. Pl. V. a lighted taper is introduced; if the taper is not
immediately extinguished, we conclude the gas to contain oxygen gas;
and, in proportion to the brightness of the flame, we may judge if it
contain less or more oxygen gas than atmospheric air contains. If, on
the contrary, the taper be instantly extinguished, we have strong reason
to presume that the residuum is chiefly composed of azotic gas. If, upon
the approach of the taper, the gas takes fire and burns quietly at the
surface with a white flame, we conclude it to be pure hydrogen gas; if
this flame is blue, we judge it consists of carbonated hydrogen gas;
and, if it takes fire with a sudden deflagration, that it is a mixture
of oxygen and hydrogen gas. If, again, upon mixing a portion of the
residuum with oxygen gas, red fumes are produced, we conclude that it
contains nitrous gas.
These preliminary trials give some general knowledge of the properties
of the gas, and nature of the mixture, but are not sufficient to
determine the proportions and quantities of the several gasses of which
it is composed. For this purpose all the methods of analysis must be
employed; and, to direct these properly, it is of great use to have a
previous approximation by the above methods. Suppose, for instance, we
know that the residuum consists of oxygen and azotic gas mixed together,
put a determinate quantity, 100 parts, into a graduated tube of ten or
twelve lines diameter, introduce a solution of sulphuret of potash in
contact with the gas, and leave them together for some days; the
sulphuret absorbs the whole oxygen gas, and leaves the azotic gas pure.
If it is known to contain hydrogen gas, a determinate quantity is
introduced into Volta's eudiometer alongst with a known proportion of
hydrogen gas; these are deflagrated together by means of the electrical
spark; fresh portions of oxygen gas are successively added, till no
farther deflagration takes place, and till the greatest possible
diminution is produced. By this process water is formed, which is
immediately absorbed by the water of the apparatus; but, if the hydrogen
gas contain charcoal, carbonic acid is formed at the same time, which is
not absorbed so quickly; the quantity of this is readily ascertained by
assisting its absorption, by means of agitation. If the residuum
contains nitrous gas, by adding oxygen gas, with which it combines into
nitric acid, we can very nearly ascertain its quantity, from the
diminution produced by this mixture.
I confine myself to these general examples, which are sufficient to give
an idea of this kind of operations; a whole volume would not serve to
explain every possible case. It is necessary to become familiar with the
analysis of gasses by long experience; we must even acknowledge that
they mostly possess such powerful affinities to each other, that we are
not always certain of having separated them completely. In these cases,
we must vary our experiments in every possible point of view, add new
agents to the combination, and keep out others, and continue our trials,
till we are certain of the truth and exactitude of our conclusions.
SECT. V.
_Of the necessary corrections upon the volume of the Gasses, according
to the pressure of the Atmosphere._
All elastic fluids are compressible or condensible in proportion to the
weight with which they are loaded. Perhaps this law, which is
ascertained by general experience, may suffer some irregularity when
these fluids are under a degree of condensation almost sufficient to
reduce them to the liquid state, or when either in a state of extreme
rarefaction or condensation; but we seldom approach either of these
limits with most of the gasses which we submit to our experiments. I
understand this proposition of gasses being compressible, in proportion
to their superincumbent weights, as follows:
A barometer, which is an instrument generally known, is, properly
speaking, a species of syphon, ABCD, Pl. XII. Fig. 16. whose leg AB is
filled with mercury, whilst the leg CD is full of air. If we suppose the
branch CD indefinitely continued till it equals the height of our
atmosphere, we can readily conceive that the barometer is, in reality, a
sort of balance, in which a column of mercury stands in equilibrium
with a column of air of the same weight. But it is unnecessary to
prolongate the branch CD to such a height, as it is evident that the
barometer being immersed in air, the column of mercury AB will be
equally in equilibrium with a column of air of the same diameter, though
the leg CD be cut off at C, and the part CD be taken away altogether.
The medium height of mercury in equilibrium with the weight of a column
of air, from the highest part of the atmosphere to the surface of the
earth is about twenty-eight French inches in the lower parts of the city
of Paris; or, in other words, the air at the surface of the earth at
Paris is usually pressed upon by a weight equal to that of a column of
mercury twenty-eight inches in height. I must be understood in this way
in the several parts of this publication when talking of the different
gasses, as, for instance, when the cubical foot of oxygen gas is said to
weigh 1 oz. 4 gros, under 28 inches pressure. The height of this
column of mercury, supported by the pressure of the air, diminishes in
proportion as we are elevated above the surface of the earth, or rather
above the level of the sea, because the mercury can only form an
equilibrium with the column of air which is above it, and is not in the
smallest degree affected by the air which is below its level.
In what ratio does the mercury in the barometer descend in proportion to
its elevation? or, what is the same thing, according to what law or
ratio do the several strata of the atmosphere decrease in density? This
question, which has exercised the ingenuity of natural philosophers
during last century, is considerably elucidated by the following
experiment.
If we take the glass syphon ABCDE, Pl. XII. Fig. 17. shut at E, and open
at A, and introduce a few drops of mercury, so as to intercept the
communication of air between the leg AB and the leg BE, it is evident
that the air contained in BCDE is pressed upon, in common with the whole
surrounding air, by a weight or column of air equal to 28 inches of
mercury. But, if we pour 28 inches of mercury into the leg AB, it is
plain the air in the branch BCDE will now be pressed upon by a weight
equal to twice 28 inches of mercury, or twice the weight of the
atmosphere; and experience shows, that, in this case, the included air,
instead of filling the tube from B to E, only occupies from C to E, or
exactly one half of the space it filled before. If to this first column
of mercury we add two other portions of 28 inches each, in the branch
AB, the air in the branch BCDE will be pressed upon by four times the
weight of the atmosphere, or four times the weight of 28 inches of
mercury, and it will then only fill the space from D to E, or exactly
one quarter of the space it occupied at the commencement of the
experiment. From these experiments, which may be infinitely varied, has
been deduced as a general law of nature, which seems applicable to all
permanently elastic fluids, that they diminish in volume in proportion
to the weights with which they are pressed upon; or, in other words,
"_the volume of all elastic fluids is in the inverse ratio of the weight
by which they are compressed_."
The experiments which have been made for measuring the heights of
mountains by means of the barometer, confirm the truth of these
deductions; and, even supposing them in some degree inaccurate, these
differences are so extremely small, that they may be reckoned as
nullities in chemical experiments. When this law of the compression of
elastic fluids is once well understood, it becomes easily applicable to
the corrections necessary in pneumato chemical experiments upon the
volume of gas, in relation to its pressure. These corrections are of two
kinds, the one relative to the variations of the barometer, and the
other for the column of water or mercury contained in the jars. I shall
endeavour to explain these by examples, beginning with the most simple
case.
Suppose that 100 cubical inches of oxygen gas are obtained at 10°
(54.5°) of the thermometer, and at 28 inches 6 lines of the barometer,
it is required to know what volume the 100 cubical inches of gas would
occupy, under the pressure of 28 inches[58], and what is the exact
weight of the 100 inches of oxygen gas? Let the unknown volume, or the
number of inches this gas would occupy at 28 inches of the barometer, be
expressed by x; and, since the volumes are in the inverse ratio of
their superincumbent weights, we have the following statement: 100
cubical inches is to x inversely as 28.5 inches of pressure is to 28.0
inches; or directly 28 : 28.5 :: 100 : x = 101.786--cubical inches, at
28 inches barometrical pressure; that is to say, the same gas or air
which at 28.5 inches of the barometer occupies 100 cubical inches of
volume, will occupy 101.786 cubical inches when the barometer is at 28
inches. It is equally easy to calculate the weight of this gas,
occupying 100 cubical inches, under 28.5 inches of barometrical
pressure; for, as it corresponds to 101.786 cubical inches at the
pressure of 28, and as, at this pressure, and at 10° (54.5°) of
temperature, each cubical inch of oxygen gas weighs half a grain, it
follows, that 100 cubical inches, under 28.5 barometrical pressure, must
weigh 50.893 grains. This conclusion might have been formed more
directly, as, since the volume of elastic fluids is in the inverse ratio
of their compression, their weights must be in the direct ratio of the
same compression: Hence, since 100 cubical inches weigh 50 grains, under
the pressure of 28 inches, we have the following statement to determine
the weight of 100 cubical inches of the same gas as 28.5 barometrical
pressure, 28 : 50 :: 28.5 : x, the unknown quantity, = 50.893.
The following case is more complicated: Suppose the jar A, Pl. XII. Fig.
18. to contain a quantity of gas in its upper part ACD, the rest of the
jar below CD being full of mercury, and the whole standing in the
mercurial bason or reservoir GHIK, filled with mercury up to EF, and
that the difference between the surface CD of the mercury in the jar,
and EF, that in the cistern, is six inches, while the barometer stands
at 27.5 inches. It is evident from these data, that the air contained in
ACD is pressed upon by the weight of the atmosphere, diminished by the
weight of the column of mercury CE, or by 27.5 - 6 = 21.5 inches of
barometrical pressure. This air is therefore less compressed than the
atmosphere at the mean height of the barometer, and consequently
occupies more space than it would occupy at the mean pressure, the
difference being exactly proportional to the difference between the
compressing weights. If, then, upon measuring the space ACD, it is found
to be 120 cubical inches, it must be reduced to the volume which it
would occupy under the mean pressure of 28 inches. This is done by the
following statement: 120 : x, the unknown volume, :: 21.5 : 28
inversely; this gives x = 120 × 21.5 / 28 = 92.143 cubical inches.
In these calculations we may either reduce the height of the mercury in
the barometer, and the difference of level in the jar and bason, into
lines or decimal fractions of the inch; but I prefer the latter, as it
is more readily calculated. As, in these operations, which frequently
recur, it is of great use to have means of abbreviation, I have given a
table in the appendix for reducing lines and fractions of lines into
decimal fractions of the inch.
In experiments performed in the water-apparatus, we must make similar
corrections to procure rigorously exact results, by taking into account,
and making allowances for the difference of height of the water within
the jar above the surface of the water in the cistern. But, as the
pressure of the atmosphere is expressed in inches and lines of the
mercurial barometer, and, as homogeneous quantities only can be
calculated together, we must reduce the observed inches and lines of
water into correspondent heights of the mercury. I have given a table in
the appendix for this conversion, upon the supposition that mercury is
13.5681 times heavier than water.
SECT. VI.
_Of Corrections relative to the Degrees of the Thermometer._
In ascertaining the weight of gasses, besides reducing them to a mean of
barometrical pressure, as directed in the preceding section, we must
likewise reduce them to a standard thermometrical temperature; because,
all elastic fluids being expanded by heat, and condensed by cold, their
weight in any determinate volume is thereby liable to considerable
alterations. As the temperature of 10° (54.5°) is a medium between the
heat of summer and the cold of winter, being the temperature of
subterraneous places, and that which is most easily approached to at all
seasons, I have chosen that degree as a mean to which I reduce air or
gas in this species of calculation.
Mr de Luc found that atmospheric air was increased 1/215 part of its
bulk, by each degree of a mercurial thermometer, divided into 81
degrees, between the freezing and boiling points; this gives 1/211 part
for each degree of Reaumur's thermometer, which is divided into 80
degrees between these two points. The experiments of Mr Monge seem to
make this dilatation less for hydrogen gas, which he thinks is only
dilated 1/180. We have not any exact experiments hitherto published
respecting the ratio of dilatation of the other gasses; but, from the
trials which have been made, their dilatation seems to differ little
from that of atmospheric air. Hence I may take for granted, till farther
experiments give us better information upon this subject, that
atmospherical air is dilated 1/210 part, and hydrogen gas 1/190 part for
each degree of the thermometer; but, as there is still great uncertainty
upon this point, we ought always to operate in a temperature as near as
possible to the standard of 10°, (54.5°) by this means any errors in
correcting the weight or volume of gasses by reducing them to the common
standard, will become of little moment.
The calculation for this correction is extremely easy. Divide the
observed volume of air by 210, and multiply the quotient by the degrees
of temperature above or below 10° (54.5°). This correction is negative
when the actual temperature is above the standard, and positive when
below. By the use of logarithmical tables this calculation is much
facilitated[59].
SECT. VII.
_Example for calculating the Corrections relative to the Variations of
Pressure and Temperature._
CASE.
In the jar A, Pl. IV. Fig. 3. standing in a water apparatus, is
contained 353 cubical inches of air; the surface of the water within the
jar at EF is 4-1/2 inches above the water in the cistern, the barometer
is at 27 inches 9-1/2 lines, and the thermometer at 15° (65.75°). Having
burnt a quantity of phosphorus in the air, by which concrete phosphoric
acid is produced, the air after the combustion occupies 295 cubical
inches, the water within the jar stands 7 inches above that in the
cistern, the barometer is at 27 inches 9-1/4 lines, and the thermometer
at 16° (68°). It is required from these data to determine the actual
volume of air before and after combustion, and the quantity absorbed
during the process.
_Calculation before Combustion._
The air in the jar before combustion was 353 cubical inches, but it was
only under a barometrical pressure of 27 inches 9-1/2 lines; which,
reduced to decimal fractions by Tab. I. of the Appendix, gives 27.79167
inches; and from this we must deduct the difference of 4-1/2 inches of
water, which, by Tab. II. corresponds to 0.33166 inches of the
barometer; hence the real pressure of the air in the jar is 27.46001. As
the volume of elastic fluids diminish in the inverse ratio of the
compressing weights, we have the following statement to reduce the 353
inches to the volume the air would occupy at 28 inches barometrical
pressure.
353 : x, the unknown volume, :: 27.46001 : 28. Hence, x = 353 ×
27.46001 / 28 = 346.192 cubical inches, which is the volume the same
quantity of air would have occupied at 28 inches of the barometer.
The 210th part of this corrected volume is 1.65, which, for the five
degrees of temperature above the standard gives 8.255 cubical inches;
and, as this correction is subtractive, the real corrected volume of the
air before combustion is 337.942 inches.
_Calculation after Combustion._
By a similar calculation upon the volume of air after combustion, we
find its barometrical pressure 27.77083 - 0.51593 = 27.25490. Hence, to
have the volume of air under the pressure of 28 inches, 295 : x ::
27.77083 : 28 inversely; or, x = 295 x 27.25490 / 28 = 287.150. The
210th part of this corrected volume is 1.368, which, multiplied by 6
degrees of thermometrical difference, gives the subtractive correction
for temperature 8.208, leaving the actual corrected volume of air after
combustion 278.942 inches.
_Result._
The corrected volume before combustion 337.942
Ditto remaining after combustion 278.942
--------
Volume absorbed during combustion 59.000.
SECT. VIII.
_Method of determining the Absolute Gravity of the different Gasses._
Take a large balloon A, Pl. V. Fig. 10. capable of holding 17 or 18
pints, or about half a cubical foot, having the brass cap bcde
strongly cemented to its neck, and to which the tube and stop-cock f g
is fixed by a tight screw. This apparatus is connected by the double
screw represented separately at Fig. 12. to the jar BCD, Fig. 10. which
must be some pints larger in dimensions than the balloon. This jar is
open at top, and is furnished with the brass cap h i, and stop-cock l
m. One of these slop-cocks is represented separately at Fig. 11.
We first determine the exact capacity of the balloon by filling it with
water, and weighing it both full and empty. When emptied of water, it is
dried with a cloth introduced through its neck d e, and the last
remains of moisture are removed by exhausting it once or twice in an
air-pump.
When the weight of any gas is to be ascertained, this apparatus is used
as follows: Fix the balloon A to the plate of an air-pump by means of
the screw of the stop-cock f g, which is left open; the balloon is to
be exhausted as completely as possible, observing carefully the degree
of exhaustion by means of the barometer attached to the air-pump. When
the vacuum is formed, the stop-cock f g is shut, and the weight of the
balloon determined with the most scrupulous exactitude. It is then fixed
to the jar BCD, which we suppose placed in water in the shelf of the
pneumato chemical apparatus Fig. 1.; the jar is to be filled with the
gas we mean to weigh, and then, by opening the stop-cocks f g and l
m, the gas ascends into the balloon, whilst the water of the cistern
rises at the same time into the jar. To avoid very troublesome
corrections, it is necessary, during this first part of the operation,
to sink the jar in the cistern till the surfaces of the water within the
jar and without exactly correspond. The stop-cocks are again shut, and
the balloon being unscrewed from its connection with the jar, is to be
carefully weighed; the difference between this weight and that of the
exhausted balloon is the precise weight of the air or gas contained in
the balloon. Multiply this weight by 1728, the number of cubical inches
in a cubical foot, and divide the product by the number of cubical
inches contained in the balloon, the quotient is the weight of a cubical
foot of the gas or air submitted to experiment.
Exact account must be kept of the barometrical height and temperature of
the thermometer during the above experiment; and from these the
resulting weight of a cubical foot is easily corrected to the standard
of 28 inches and 10°, as directed in the preceding section. The small
portion of air remaining in the balloon after forming the vacuum must
likewise be attended to, which is easily determined by the barometer
attached to the air-pump. If that barometer, for instance, remains at
the hundredth part of the height it stood at before the vacuum was
formed, we conclude that one hundredth part of the air originally
contained remained in the balloon, and consequently that only 99/100 of
gas was introduced from the jar into the balloon.
FOOTNOTES:
[58] According to the proportion of 114 to 107, given between the French
and English foot, 28 inches of the French barometer are equal to 29.83
inches of the English. Directions will be found in the appendix for
converting all the French weights and measures used in this work into
corresponding English denominations.--E.
[59] When Fahrenheit's thermometer is employed, the dilatation by each
degree must be smaller, in the proportion of 1 to 2.25, because each
degree of Reaumur's scale contains 2.25 degrees of Fahrenheit; hence we
must divide by 472.5, and finish the rest of the calculation as
above.--E.
CHAP. III.
_Description of the Calorimeter, or Apparatus for measuring Caloric._
The calorimeter, or apparatus for measuring the relative quantities of
heat contained in bodies, was described by Mr de la Place and me in the
Memoirs of the Academy for 1780, p. 355. and from that Essay the
materials of this chapter are extracted.
If, after having cooled any body to the freezing point, it be exposed in
an atmosphere of 25° (88.25°), the body will gradually become heated,
from the surface inwards, till at last it acquire the same temperature
with the surrounding air. But, if a piece of ice be placed in the same
situation, the circumstances are quite different; it does not approach
in the smallest degree towards the temperature of the circumambient air,
but remains constantly at Zero (32°), or the temperature of melting ice,
till the last portion of ice be completely melted.
This phenomenon is readily explained; as, to melt ice, or reduce it to
water, it requires to be combined with a certain portion of caloric;
the whole caloric attracted from the surrounding bodies, is arrested or
fixed at the surface or external layer of ice which it is employed to
dissolve, and combines with it to form water; the next quantity of
caloric combines with the second layer to dissolve it into water, and so
on successively till the whole ice be dissolved or converted into water
by combination with caloric, the very last atom still remaining at its
former temperature, because the caloric has never penetrated so far as
long as any intermediate ice remained to melt.
Upon these principles, if we conceive a hollow sphere of ice at the
temperature of Zero (32°) placed in an atmosphere 10° (54.5°), and
containing a substance at any degree of temperature above freezing, it
follows, 1st, That the heat of the external atmosphere cannot penetrate
into the internal hollow of the sphere of ice; 2dly, That the heat of
the body placed in the hollow of the sphere cannot penetrate outwards
beyond it, but will be stopped at the internal surface, and continually
employed to melt successive layers of ice, until the temperature of the
body be reduced to Zero (32°), by having all its superabundant caloric
above that temperature carried off by the ice. If the whole water,
formed within the sphere of ice during the reduction of the temperature
of the included body to Zero, be carefully collected, the weight of the
water will be exactly proportional to the quantity of caloric lost by
the body in passing from its original temperature to that of melting
ice; for it is evident that a double quantity of caloric would have
melted twice the quantity of ice; hence the quantity of ice melted is a
very exact measure of the quantity of caloric employed to produce that
effect, and consequently of the quantity lost by the only substance that
could possibly have supplied it.
I have made this supposition of what would take place in a hollow sphere
of ice, for the purpose of more readily explaining the method used in
this species of experiment, which was first conceived by Mr de la Place.
It would be difficult to procure such spheres of ices and inconvenient
to make use of them when got; but, by means of the following apparatus,
we have remedied that defect. I acknowledge the name of Calorimeter,
which I have given it, as derived partly from Greek and partly from
Latin, is in some degree open to criticism; but, in matters of science,
a slight deviation from strict etymology, for the sake of giving
distinctness of idea, is excusable; and I could not derive the name
entirely from Greek without approaching too near to the names of known
instruments employed for other purposes.
The calorimeter is represented in Pl. VI. It is shown in perspective at
Fig. 1. and its interior structure is engraved in Fig. 2. and 3.; the
former being a horizontal, and the latter a perpendicular section. Its
capacity or cavity is divided into three parts, which, for better
distinction, I shall name the interior, middle, and external cavities.
The interior cavity f f f f, Fig. 4. into which the substances
submitted to experiment are put, is composed of a grating or cage of
iron wire, supported by several iron bars; its opening or mouth LM, is
covered by the lid HG, of the same materials. The middle cavity b b b
b, Fig. 2. and 3. is intended to contain the ice which surrounds the
interior cavity, and which is to be melted by the caloric of the
substance employed in the experiment. The ice is supported by the grate
m m at the bottom of the cavity, under which is placed the sieve n
n. These two are represented separately in Fig. 5. and 6.
In proportion as the ice contained in the middle cavity is melted, by
the caloric disengaged from the body placed in the interior cavity, the
water runs through the grate and sieve, and falls through the conical
funnel c c d, Fig. 3. and tube x y, into the receiver F, Fig. 1.
This water may be retained or let out at pleasure, by means of the
stop-cock u. The external cavity a a a a, Fig. 2. and 3. is filled
with ice, to prevent any effect upon the ice in the middle cavity from
the heat of the surrounding air, and the water produced from it is
carried off through the pipe ST, which shuts by means of the stop-cock
r. The whole machine is covered by the lid FF, Fig. 7. made of tin
painted with oil colour, to prevent rust.
When this machine is to be employed, the middle cavity b b b b, Fig.
2. and 3., the lid GH, Fig. 4. of the interior cavity, the external
cavity a a a a, Fig. 2. and 3. and the general lid FF, Fig. 7. are all
filled with pounded ice, well rammed, so that no void spaces remain, and
the ice of the middle cavity is allowed to drain. The machine is then
opened, and the substance submitted to experiment being placed in the
interior cavity, it is instantly closed. After waiting till the included
body is completely cooled to the freezing point, and the whole melted
ice has drained from the middle cavity, the water collected in the
vessel F, Fig. 1. is accurately weighed. The weight of the water
produced during the experiment is an exact measure of the caloric
disengaged during the cooling of the included body, as this substance is
evidently in a similar situation with the one formerly mentioned as
included in a hollow sphere of ice; the whole caloric disengaged is
stopped by the ice in the middle cavity, and that ice is preserved from
being affected by any other heat by means of the ice contained in the
general lid, Fig. 7. and in the external cavity. Experiments of this
kind last from fifteen to twenty hours; they are sometimes accelerated
by covering up the substance in the interior cavity with well drained
ice, which hastens its cooling.
The substances to be operated upon are placed in the thin iron bucket,
Fig. 8. the cover of which has an opening fitted with a cork, into which
a small thermometer is fixed. When we use acids, or other fluids capable
of injuring the metal of the instruments, they are contained in the
matras, Fig. 10. which has a similar thermometer in a cork fitted to its
mouth, and which stands in the interior cavity upon the small
cylindrical support RS, Fig. 10.
It is absolutely requisite that there be no communication between the
external and middle cavities of the calorimeter, otherwise the ice
melted by the influence of the surrounding air, in the external cavity,
would mix with the water produced from the ice of the middle cavity,
which would no longer be a measure of the caloric lost by the substance
submitted to experiment.
When the temperature of the atmosphere is only a few degrees above the
freezing point, its heat can hardly reach the middle cavity, being
arrested by the ice of the cover, Fig. 7. and of the external cavity;
but, if the temperature of the air be under the degree of freezing, it
might cool the ice contained in the middle cavity, by causing the ice
in the external cavity to fall, in the first place, below zero (32°). It
is therefore essential that this experiment be carried on in a
temperature somewhat above freezing: Hence, in time of frost, the
calorimeter must be kept in an apartment carefully heated. It is
likewise necessary that the ice employed be not under zero (32°); for
which purpose it must be pounded, and spread out thin for some time, in
a place of a higher temperature.
The ice of the interior cavity always retains a certain quantity of
water adhering to its surface, which may be supposed to belong to the
result of the experiment; but as, at the beginning of each experiment,
the ice is already saturated with as much water as it can contain, if
any of the water produced by the caloric should remain attached to the
ice, it is evident, that very nearly an equal quantity of what adhered
to it before the experiment must have run down into the vessel F in its
stead; for the inner surface of the ice in the middle cavity is very
little changed during the experiment.
By any contrivance that could be devised, we could not prevent the
access of the external air into the interior cavity when the atmosphere
was 9° or 10° (52° or 54°) above zero. The air confined in the cavity
being in that case specifically heavier than the external air, escapes
downwards through the pipe x y, Fig. 3, and is replaced by the warmer
external air, which, giving out its caloric to the ice, becomes heavier,
and sinks in its turn; thus a current of air is formed through the
machine, which is the more rapid in proportion as the external air
exceeds the internal in temperature. This current of warm air must melt
a part of the ice, and injure the accuracy of the experiment: We may, in
a great degree, guard against this source of error by keeping the
stop-cock u continually shut; but it is better to operate only when
the temperature of the external air does not exceed 3°, or at most 4°,
(39° to 41°); for we have observed, that, in this case, the melting of
the interior ice by the atmospheric air is perfectly insensible; so that
we may answer for the accuracy of our experiments upon the specific heat
of bodies to a fortieth part.
We have caused make two of the above described machines; one, which is
intended for such experiments as do not require the interior air to be
renewed, is precisely formed according to the description here given;
the other, which answers for experiments upon combustion, respiration,
&c. in which fresh quantities of air are indispensibly necessary,
differs from the former in having two small tubes in the two lids, by
which a current of atmospheric air may be blown into the interior cavity
of the machine.
It is extremely easy, with this apparatus, to determine the phenomena
which occur in operations where caloric is either disengaged or
absorbed. If we wish, for instance, to ascertain the quantity of caloric
which is disengaged from a solid body in cooling a certain number of
degrees, let its temperature be raised to 80° (212°); it is then placed
in the interior cavity f f f f, Fig. 2. and 3. of the calorimeter, and
allowed to remain till we are certain that its temperature is reduced to
zero (32°); the water produced by melting the ice during its cooling is
collected, and carefully weighed; and this weight, divided by the volume
of the body submitted to experiment, multiplied into the degrees of
temperature which it had above zero at the commencement of the
experiment, gives the proportion of what the English philosophers call
specific heat.
Fluids are contained in proper vessels, whose specific heat has been
previously ascertained, and operated upon in the machine in the same
manner as directed for solids, taking care to deduct, from the quantity
of water melted during the experiment, the proportion which belongs to
the containing vessel.
If the quantity of caloric disengaged during the combination of
different substances is to be determined, these substances are to be
previously reduced to the freezing degree by keeping them a sufficient
time surrounded with pounded ice; the mixture is then to be made in the
inner cavity of the calorimeter, in a proper vessel likewise reduced to
zero (32°); and they are kept inclosed till the temperature of the
combination has returned to the same degree: The quantity of water
produced is a measure of the caloric disengaged during the combination.
To determine the quantity of caloric disengaged during combustion, and
during animal respiration, the combustible bodies are burnt, or the
animals are made to breathe in the interior cavity, and the water
produced is carefully collected. Guinea pigs, which resist the effects
of cold extremely well, are well adapted for this experiment. As the
continual renewal of air is absolutely necessary in such experiments, we
blow fresh air into the interior cavity of the calorimeter by means of a
pipe destined for that purpose, and allow it to escape through another
pipe of the same kind; and that the heat of this air may not produce
errors in the results of the experiments, the tube which conveys it into
the machine is made to pass through pounded ice, that it may be reduced
to zero (32°) before it arrives at the calorimeter. The air which
escapes must likewise be made to pass through a tube surrounded with
ice, included in the interior cavity of the machine, and the water which
is produced must make a part of what is collected, because the caloric
disengaged from this air is part of the product of the experiment.
It is somewhat more difficult to determine the specific caloric
contained in the different gasses, on account of their small degree of
density; for, if they are only placed in the calorimeter in vessels like
other fluids, the quantity of ice melted is so small, that the result of
the experiment becomes at best very uncertain. For this species of
experiment we have contrived to make the air pass through two metallic
worms, or spiral tubes; one of these, through which the air passes, and
becomes heated in its way to the calorimeter, is contained in a vessel
full of boiling water, and the other, through which the air circulates
within the calorimeter to disengage its caloric, is placed in the
interior cavity, f f f f, of that machine. By means of a small
thermometer placed at one end of the second worm, the temperature of the
air, as it enters the calorimeter, is determined, and its temperature in
getting out of the interior cavity is found by another thermometer
placed at the other end of the worm. By this contrivance we are enabled
to ascertain the quantity of ice melted by determinate quantities of air
or gas, while losing a certain number of degrees of temperature, and,
consequently, to determine their several degrees of specific caloric.
The same apparatus, with some particular precautions, may be employed
to ascertain the quantity of caloric disengaged by the condensation of
the vapours of different liquids.
The various experiments which may be made with the calorimeter do not
afford absolute conclusions, but only give us the measure of relative
quantities; we have therefore to fix a unit, or standard point, from
whence to form a scale of the several results. The quantity of caloric
necessary to melt a pound of ice has been chosen as this unit; and, as
it requires a pound of water of the temperature of 60° (167°) to melt a
pound of ice, the quantity of caloric expressed by our unit or standard
point is what raises a pound of water from zero (32°) to 60° (167°).
When this unit is once determined, we have only to express the
quantities of caloric disengaged from different bodies by cooling a
certain number of degrees, in analogous values: The following is an easy
mode of calculation for this purpose, applied to one of our earliest
experiments.
We took 7 lib. 11 oz. 2 gros 36 grs. of plate-iron, cut into
narrow slips, and rolled up, or expressing the quantity in decimals,
7.7070319. These, being heated in a bath of boiling water to about 78°
(207.5°), were quickly introduced into the interior cavity of the
calorimeter: At the end of eleven hours, when the whole quantity of
water melted from the ice had thoroughly drained off, we found that
1.109795 pounds of ice were melted. Hence, the caloric disengaged from
the iron by cooling 78° (175.5°) having melted 1.109795 pounds of ice,
how much would have been melted by cooling 60° (135°)? This question
gives the following statement in direct proportion, 78 : 1.109795 :: 60
: x = 0.85369. Dividing this quantity by the weight of the whole iron
employed, viz. 7.7070319, the quotient 0.110770 is the quantity of ice
which would have been melted by one pound of iron whilst cooling through
60° (135°) of temperature.
Fluid substances, such as sulphuric and nitric acids, &c. are contained
in a matras, Pl. VI. Fig. 9. having a thermometer adapted to the cork,
with its bulb immersed in the liquid. The matras is placed in a bath of
boiling water, and when, from the thermometer, we judge the liquid is
raised to a proper temperature, the matras is placed in the calorimeter.
The calculation of the products, to determine the specific caloric of
these fluids, is made as above directed, taking care to deduct from the
water obtained the quantity which would have been produced by the matras
alone, which must be ascertained by a previous experiment. The table of
the results obtained by these experiments is omitted, because not yet
sufficiently complete, different circumstances having occasioned the
series to be interrupted; it is not, however, lost sight of; and we are
less or more employed upon the subject every winter.
CHAP. IV.
_Of Mechanical Operations for Division of Bodies._
SECT. I.
_Of Trituration, Levigation, and Pulverization._
These are, properly speaking, only preliminary mechanical operations for
dividing and separating the particles of bodies, and reducing them into
very fine powder. These operations can never reduce substances into
their primary, or elementary and ultimate particles; they do not even
destroy the aggregation of bodies; for every particle, after the most
accurate trituration, forms a small whole, resembling the original mass
from which it was divided. The real chemical operations, on the
contrary, such as solution, destroy the aggregation of bodies, and
separate their constituent and integrant particles from each other.
Brittle substances are reduced to powder by means of pestles and
mortars. These are of brass or iron, Pl. I. Fig. 1.; of marble or
granite, Fig. 2.; of lignum vitae, Fig. 3.; of glass, Fig. 4.; of agate,
Fig. 5.; or of porcellain, Fig. 6. The pestles for each of these are
represented in the plate, immediately below the mortars to which they
respectively belong, and are made of hammered iron or brass, of wood,
glass, porcellain, marble, granite, or agate, according to the nature of
the substances they are intended to triturate. In every laboratory, it
is requisite to have an assortment of these utensils, of various sizes
and kinds: Those of porcellain and glass can only be used for rubbing
substances to powder, by a dexterous use of the pestle round the sides
of the mortar, as it would be easily broken by reiterated blows of the
pestle.
The bottom of mortars ought to be in the form of a hollow sphere, and
their sides should have such a degree of inclination as to make the
substances they contain fall back to the bottom when the pestle is
lifted, but not so perpendicular as to collect them too much together,
otherwise too large a quantity would get below the pestle, and prevent
its operation. For this reason, likewise, too large a quantity of the
substance to be powdered ought not to be put into the mortar at one
time; and we must from time to time get rid of the particles already
reduced to powder, by means of sieves to be afterwards described.
The most usual method of levigation is by means of a flat table ABCD,
Pl. 1. Fig. 7. of porphyry, or other stone of similar hardness, upon
which the substance to be reduced to powder is spread, and is then
bruised and rubbed by a muller M, of the same hard materials, the bottom
of which is made a small portion of a large sphere; and, as the muller
tends continually to drive the substances towards the sides of the
table, a thin flexible knife, or spatula of iron, horn, wood, or ivory,
is used for bringing them back to the middle of the stone.
In large works, this operation is performed by means of large rollers of
hard stone, which turn upon each other, either horizontally, in the way
of corn-mills, or by one vertical roller turning upon a flat stone. In
the above operations, it is often requisite to moisten the substances a
little, to prevent the fine powder from flying off.
There are many bodies which cannot be reduced to powder by any of the
foregoing methods; such are fibrous substances, as woods; such as are
tough and elastic, as the horns of animals, elastic gum, &c. and the
malleable metals which flatten under the pestle, instead of being
reduced to powder. For reducing the woods to powder, rasps, as Pl. I.
Fig. 8. are employed; files of a finer kind are used for horn, and still
finer, Pl. 1. Fig. 9. and 10. for metals.
Some of the metals, though not brittle enough to powder under the
pestle, are too soft to be filed, as they clog the file, and prevent its
operation. Zinc is one of these, but it may be powdered when hot in a
heated iron mortar, or it may be rendered brittle, by alloying it with a
small quantity of mercury. One or other of these methods is used by
fire-work makers for producing a blue flame by means of zinc. Metals may
be reduced into grains, by pouring them when melted into water, which
serves very well when they are not wanted in fine powder.
Fruits, potatoes, &c. of a pulpy and fibrous nature may be reduced to
pulp by means of the grater, Pl. 1. Fig. 11.
The choice of the different substances of which these instruments are
made is a matter of importance; brass or copper are unfit for operations
upon substances to be used as food or in pharmacy; and marble or
metallic instruments must not be used for acid substances; hence mortars
of very hard wood, and those of porcelain, granite, or glass, are of
great utility in many operations.
SECT. II.
_Of Sifting and Washing Powdered Substances._
None of the mechanical operations employed for reducing bodies to powder
is capable of producing it of an equal degree of fineness throughout;
the powder obtained by the longest and most accurate trituration being
still an assemblage of particles of various sizes. The coarser of these
are removed, so as only to leave the finer and more homogeneous
particles by means of sieves, Pl. I. Fig. 12. 13. 14. 15. of different
finenesses, adapted to the particular purposes they are intended for;
all the powdered matter which is larger than the intestices of the sieve
remains behind, and is again submitted to the pestle, while the finer
pass through. The sieve Fig. 12. is made of hair-cloth, or of silk
gauze; and the one represented Fig. 13. is of parchment pierced with
round holes of a proper size; this latter is employed in the manufacture
of gun-powder. When very subtile or valuable materials are to be sifted,
which are easily dispersed, or when the finer parts of the powder may be
hurtful, a compound sieve, Fig. 15. is made use of, which consists of
the sieve ABCD, with a lid EF, and receiver GH; these three parts are
represented as joined together for use, Fig. 14.
There is a method of procuring powders of an uniform fineness,
considerably more accurate than the sieve; but it can only be used with
such substances as are not acted upon by water. The powdered substance
is mixed and agitated with water, or other convenient fluid; the liquor
is allowed to settle for a few moments, and is then decanted off; the
coarsest powder remains at the bottom of the vessel, and the finer
passes over with the liquid. By repeated decantations in this manner,
various sediments are obtained of different degrees of fineness; the
last sediment, or that which remains longed suspended in the liquor,
being the finest. This process may likewise be used with advantage for
separating substances of different degrees of specific gravity, though
of the same fineness; this last is chiefly employed in mining, for
separating the heavier metallic ores from the lighter earthy matters
with which they are mixed.
In chemical laboratories, pans and jugs of glass or earthen ware are
employed for this operation; sometimes, for decanting the liquor without
disturbing the sediment, the glass syphon ABCHI, Pl. II. Fig. 11. is
used, which may be supported by means of the perforated board DE, at the
proper depth in the vessel FG, to draw off all the liquor required into
the receiver LM. The principles and application of this useful
instrument are so well known as to need no explanation.
SECT. III.
_Of Filtration._
A filtre is a species of very fine sieve, which is permeable to the
particles of fluids, but through which the particles of the finest
powdered solids are incapable of passing; hence its use in separating
fine powders from suspension in fluids. In pharmacy, very close and fine
woollen cloths are chiefly used for this operation; these are commonly
formed in a conical shape, Pl. II. Fig. 2. which has the advantage of
uniting all the liquor which drains through into a point A, where it may
be readily collected in a narrow mouthed vessel. In large pharmaceutical
laboratories, this filtring bag is streached upon a wooden stand, Pl.
II. Fig. 1.
For the purposes of chemistry, as it is requisite to have the filtres
perfectly clean, unsized paper is substituted instead of cloth or
flannel; through this substance, no solid body, however finely it be
powdered, can penetrate, and fluids percolate through it with the
greatest readiness. As paper breaks easily when wet, various methods of
supporting it are used according to circumstances. When a large quantity
of fluid is to be filtrated, the paper is supported by the frame of
wood, Pl. II. Fig. 3. ABCD, having a piece of coarse cloth stretched
over it, by means of iron-hooks. This cloth must be well cleaned each
time it is used, or even new cloth must be employed, if there is reason
to suspect its being impregnated with any thing which can injure the
subsequent operations. In ordinary operations, where moderate quantities
of fluid are to be filtrated, different kinds of glass funnels are used
for supporting the paper, as represented Pl. II. Fig. 5. 6. and 7. When
several filtrations must be carried on at once, the board or shelf AB,
Fig. 9. supported upon stands C and D, and pierced with round holes, is
very convenient for containing the funnels.
Some liquors are so thick and clammy, as not to be able to penetrate
through paper without some previous preparation, such as clarification
by means of white of eggs, which being mixed with the liquor, coagulates
when brought to boil, and, entangling the greater part of the impurities
of the liquor, rises with them to the surface in the state of scum.
Spiritous liquors may be clarified in the same manner by means of
isinglass dissolved in water, which coagulates by the action of the
alkohol without the assistance of heat.
As most of the acids are produced by distillation, and are consequently
clear, we have rarely any occasion to filtrate them; but if, at any
time, concentrated acids require this operation, it is impossible to
employ paper, which would be corroded and destroyed by the acid. For
this purpose, pounded glass, or rather quartz or rock-cristal, broke in
pieces and grossly powdered, answers very well; a few of the larger
pieces are put in the neck of the funnel; these are covered with the
smaller pieces, the finer powder is placed over all, and the acid is
poured on at top. For the ordinary purposes of society, river-water is
frequently filtrated by means of clean washed sand, to separate its
impurities.
SECT. IV.
_Of Decantation._
This operation is often substituted instead of filtration for separating
solid particles which are diffused through liquors. These are allowed to
settle in conical vessels, ABCDE, Pl. II. Fig. 10. the diffused matters
gradually subside, and the clear fluid is gently poured off. If the
sediment be extremely light, and apt to mix again with the fluid by the
slightest motion, the syphon, Fig. 11. is used, instead of decantation,
for drawing off the clear fluid.
In experiments, where the weight of the precipitate must be rigorously
ascertained, decantation is preferable to filtration, providing the
precipitate be several times washed in a considerable proportion of
water. The weight of the precipitate may indeed be ascertained, by
carefully weighing the filtre before and after the operation; but, when
the quantity of precipitate is small, the different proportions of
moisture retained by the paper, in a greater or lesser degree of
exsiccation, may prove a material source of error, which ought carefully
to be guarded against.
CHAP. V.
_Of Chemical Means for separating the Particles of Bodies from each
other; without Decomposition, and for uniting them again._
I have already shown that there are two methods of dividing the
particles of bodies, the _mechanical_ and _chemical_. The former only
separates a solid mass into a great number of smaller masses; and for
these purposes various species of forces are employed, according to
circumstances, such as the strength of man or of animals, the weight of
water applied through the means of hydraulic engines, the expansive
power of steam, the force of the wind, &c. By all these mechanical
powers, we can never reduce substances into powder beyond a certain
degree of fineness; and the smallest particle produced in this way,
though it seems very minute to our organs, is still in fact a mountain,
when compared with the ultimate elementary particles of the pulverized
substance.
The chemical agents, on the contrary, divide bodies into their primitive
particles. If, for instance, a neutral salt be acted upon by these, it
is divided, as far as is possible, without ceasing to be a neutral salt.
In this Chapter, I mean to give examples of this kind of division of
bodies, to which I shall add some account of the relative operations.
SECT. I.
_Of the Solution of Salts._
In chemical language, the terms of _solution_ and _dissolution_ have
long been confounded, and have very improperly been indiscriminately
employed for expressing both the division of the particles of a salt in
a fluid, such as water, and the division of a metal in an acid. A few
reflections upon the effects of these two operations will suffice to
show that they ought not to be confounded together. In the solution of
salts, the saline particles are only separated from each other, whilst
neither the salt nor the water are at all decomposed; we are able to
recover both the one and the other in the same quantity as before the
operation. The same thing takes place in the solution of resins in
alkohol. During metallic dissolutions, on the contrary, a decomposition,
either of the acid, or of the water which dilutes it, always takes
place; the metal combines with oxygen, and is changed into an oxyd, and
a gasseous substance is disengaged; so that in reality none of the
substances employed remain, after the operation, in the same state they
were in before. This article is entirely confined to the consideration
of solution.
To understand properly what takes place during the solution of salts, it
is necessary to know, that, in most of these operations, two distinct
effects are complicated together, viz. solution by water, and solution
by caloric; and, as the explanation of most of the phenomena of solution
depends upon the distinction of these two circumstances, I shall enlarge
a little upon their nature.
Nitrat of potash, usually called nitre or saltpetre, contains very
little water of cristallization, perhaps even none at all; yet this salt
liquifies in a degree of heat very little superior to that of boiling
water. This liquifaction cannot therefore be produced by means of the
water of cristallization, but in consequence of the salt being very
fusible in its nature, and from its passing from the solid to the liquid
state of aggregation, when but a little raised above the temperature of
boiling water. All salts are in this manner susceptible of being
liquified by caloric, but in higher or lower degrees of temperature.
Some of these, as the acetites of potash and soda, liquify with a very
moderate heat, whilst others, as sulphat of potash, lime, &c. require
the strongest fires we are capable of producing. This liquifaction of
salts by caloric produces exactly the same phenomena with the melting of
ice; it is accomplished in each salt by a determinate degree of heat,
which remains invariably the same during the whole time of the
liquifaction. Caloric is employed, and becomes fixed during the melting
of the salt, and is, on the contrary, disengaged when the salt
coagulates. These are general phenomena which universally occur during
the passage of every species of substance from the solid to the fluid
state of aggregation, and from fluid to solid.
These phenomena arising from solution by caloric are always less or more
conjoined with those which take place during solutions in water. We
cannot pour water upon a salt, on purpose to dissolve it, without
employing a compound solvent, both water and caloric; hence we may
distinguish several different cases of solution, according to the nature
and mode of existence of each salt. If, for instance, a salt be
difficultly soluble in water, and readily so by caloric, it evidently
follows, that this salt will be difficultly soluble in cold water, and
considerably in hot water; such is nitrat of potash, and more especially
oxygenated muriat of potash. If another salt be little soluble both in
water and caloric, the difference of its solubility in cold and warm
water will be very inconsiderable; sulphat of lime is of this kind. From
these considerations, it follows, that there is a necessary relation
between the following circumstances; the solubility of a salt in cold
water, its solubility in boiling water, and the degree of temperature at
which the same salt liquifies by caloric, unassisted by water; and that
the difference of solubility in hot and cold water is so much greater in
proportion to its ready solution in caloric, or in proportion to its
susceptibility of liquifying in a low degree of temperature.
The above is a general view of solution; but, for want of particular
facts, and sufficiently exact experiments, it is still nothing more than
an approximation towards a particular theory. The means of compleating
this part of chemical science is extremely simple; we have only to
ascertain how much of each salt is dissolved by a certain quantity of
water at different degrees of temperature; and as, by the experiments
published by Mr de la Place and me, the quantity of caloric contained in
a pound of water at each degree of the thermometer is accurately known,
it will be very easy to determine, by simple experiments, the proportion
of water and caloric required for solution by each salt, what quantity
of caloric is absorbed by each at the moment of liquifaction, and how
much is disengaged at the moment of cristallization. Hence the reason
why salts are more rapidly soluble in hot than in cold water is
perfectly evident. In all solutions of salts caloric is employed; when
that is furnished intermediately from the surrounding bodies, it can
only arrive slowly to the salt; whereas this is greatly accelerated when
the requisite caloric exists ready combined with the water of solution.
In general, the specific gravity of water is augmented by holding salts
in solution; but there are some exceptions to the rule. Some time hence,
the quantities of radical, of oxygen, and of base, which constitute each
neutral salt, the quantity of water and caloric necessary for solution,
the increased specific gravity communicated to water, and the figure of
the elementary particles of the cristals, will all be accurately known.
From these all the circumstances and phenomena of cristallization will
be explained, and by these means this part of chemistry will be
compleated. Mr Seguin has formed the plan of a thorough investigation of
this kind, which he is extremely capable of executing.
The solution of salts in water requires no particular apparatus; small
glass phials of different sizes, Pl. II. Fig. 16. and 17. pans of
earthern ware, A, Fig. 1. and 2. long-necked matrasses, Fig. 14. and
pans or basons of copper or of silver, Fig. 13. and 15. answer very well
for these operations.
SECT. II.
_Of Lixiviation._
This is an operation used in chemistry and manufactures for separating
substances which are soluble in water from such as are insoluble. The
large vat or tub, Pl. II. Fig. 12. having a hole D near its bottom,
containing a wooden spiget and fosset or metallic stop-cock DE, is
generally used for this purpose. A thin stratum of straw is placed at
the bottom of the tub; over this, the substance to be lixiviated is laid
and covered by a cloth, then hot or cold water, according to the degree
of solubility of the saline matter, is poured on. When the water is
supposed to have dissolved all the saline parts, it is let off by the
stop-cock; and, as some of the water charged with salt necessarily
adheres to the straw and insoluble matters, several fresh quantities of
water are poured on. The straw serves to secure a proper passage for the
water, and may be compared to the straws or glass rods used in
filtrating, to keep the paper from touching the sides of the funnel. The
cloth which is laid over the matters under lixiviation prevents the
water from making a hollow in these substances where it is poured on,
through which it might escape without acting upon the whole mass.
This operation is less or more imitated in chemical experiments; but as
in these, especially with analytical views, greater exactness is
required, particular precautions must be employed, so as not to leave
any saline or soluble part in the residuum. More water must be employed
than in ordinary lixiviations, and the substances ought to be previously
stirred up in the water before the clear liquor is drawn off, otherwise
the whole mass might not be equally lixiviated, and some parts might
even escape altogether from the action of the water. We must likewise
employ fresh portions of water in considerable quantity, until it comes
off entirely free from salt, which we may ascertain by means of the
hydrometer formerly described.
In experiments with small quantities, this operation is conveniently
performed in jugs or matrasses of glass, and by filtrating the liquor
through paper in a glass funnel. When the substance is in larger
quantity, it may be lixiviated in a kettle of boiling water, and
filtrated through paper supported by cloth in the wooden frame, Pl. II.
Fig. 3. and 4.; and in operations in the large way, the tub already
mentioned must be used.
SECT. III.
_Of Evaporation._
This operation is used for separating two substances from each other, of
which one at least must be fluid, and whose degrees of volatility are
considerably different. By this means we obtain a salt, which has been
dissolved in water, in its concrete form; the water, by heating, becomes
combined with caloric, which renders it volatile, while the particles of
the salt being brought nearer to each other, and within the sphere of
their mutual attraction, unite into the solid state.
As it was long thought that the air had great influence upon the
quantity of fluid evaporated, it will be proper to point out the errors
which this opinion has produced. There certainly is a constant slow
evaporation from fluids exposed to the free air; and, though this
species of evaporation may be considered in some degree as a solution in
air, yet caloric has considerable influence in producing it, as is
evident from the refrigeration which always accompanies this process;
hence we may consider this gradual evaporation as a compound solution
made partly in air, and partly in caloric. But the evaporation which
takes place from a fluid kept continually boiling, is quite different in
its nature, and in it the evaporation produced by the action of the air
is exceedingly inconsiderable in comparison with that which is
occasioned by caloric. This latter species may be termed _vaporization_
rather than _evaporation_. This process is not accelerated in proportion
to the extent of evaporating surface, but in proportion to the
quantities of caloric which combine with the fluid. Too free a current
of cold air is often hurtful to this process, as it tends to carry off
caloric from the water, and consequently retards its conversion into
vapour. Hence there is no inconvenience produced by covering, in a
certain degree, the vessels in which liquids are evaporated by continual
boiling, provided the covering body be of such a nature as does not
strongly draw off the caloric, or, to use an expression of Dr
Franklin's, provided it be a bad conductor of heat. In this case, the
vapours escape through such opening as is left, and at least as much is
evaporated, frequently more than when free access is allowed to the
external air.
As during evaporation the fluid carried off by caloric is entirely lost,
being sacrificed for the sake of the fixed substances with which it was
combined, this process is only employed where the fluid is of small
value, as water, for instance. But, when the fluid is of more
consequence, we have recourse to distillation, in which process we
preserve both the fixed substance and the volatile fluid. The vessels
employed for evaporation are basons or pans of copper, silver, or lead,
Pl. II. Fig. 13. and 15. or capsules of glass, porcellain, or stone
ware, Pl. II. A, Fig. 1. and 2. Pl. III. Fig. 3 and 4. The best utensils
for this purpose are made of the bottoms of glass retorts and matrasses,
as their equal thinness renders them more fit than any other kind of
glass vessel for bearing a brisk fire and sudden alterations of heat and
cold without breaking.
As the method of cutting these glass vessels is no where described in
books, I shall here give a description of it, that they may be made by
chemists for themselves out of spoiled retorts, matrasses, and
recipients, at a much cheaper rate than any which can be procured from
glass manufacturers. The instrument, Pl. III. Fig. 5. consisting of an
iron ring AC, fixed to the rod AB, having a wooden handle D, is employed
as follows: Make the ring red hot in the fire, and put it upon the
matrass G, Fig. 6. which is to be cut; when the glass is sufficiently
heated, throw on a little cold water, and it will generally break
exactly at the circular line heated by the ring.
Small flasks or phials of thin glass are exceeding good vessels for
evaporating small quantities of fluid; they are very cheap, and stand
the fire remarkably. One or more of these may be placed upon a second
grate above the furnace, Pl. III. Fig. 2. where they will only
experience a gentle heat. By this means a great number of experiments
may be carried on at one time. A glass retort, placed in a sand bath,
and covered with a dome of baked earth, Pl. III. Fig. 1. answers pretty
well for evaporations; but in this way it is always considerably slower,
and is even liable to accidents; as the sand heats unequally, and the
glass cannot dilate in the same unequal manner, the retort is very
liable to break. Sometimes the sand serves exactly the office of the
iron ring formerly mentioned; for, if a single drop of vapour, condensed
into liquid, happens to fall upon the heated part of the vessel, it
breaks circularly at that place. When a very intense fire is necessary,
earthen crucibles may be used; but we generally use the word
_evaporation_ to express what is produced by the temperature of boiling
water, or not much higher.
SECT. IV.
_Of Cristallization._
In this process the integrant parts of a solid body, separated from each
other by the intervention of a fluid, are made to exert the mutual
attraction of aggregation, so as to coalesce and reproduce a solid mass.
When the particles of a body are only separated by caloric, and the
substance is thereby retained in the liquid state, all that is necessary
for making it cristallize, is to remove a part of the caloric which is
lodged between its particles, or, in other words, to cool it. If this
refrigeration be slow, and the body be at the same time left at rest,
its particles assume a regular arrangement, and cristallization,
properly so called, takes place; but, if the refrigeration is made
rapidly, or if the liquor be agitated at the moment of its passage to
the concrete state, the cristallization is irregular and confused.
The same phenomena occur with watery solutions, or rather in those made
partly in water, and partly by caloric. So long as there remains a
sufficiency of water and caloric to keep the particles of the body
asunder beyond the sphere of their mutual attraction, the salt remains
in the fluid state; but, whenever either caloric or water is not present
in sufficient quantity, and the attraction of the particles for each
other becomes superior to the power which keeps them asunder, the salt
recovers its concrete form, and the cristals produced are the more
regular in proportion as the evaporation has been slower and more
tranquilly performed.
All the phenomena we formerly mentioned as taking place during the
solution of salts, occur in a contrary sense during their
cristallization. Caloric is disengaged at the instant of their assuming
the solid state, which furnishes an additional proof of salt being held
in solution by the compound action of water and caloric. Hence, to cause
salts to cristallize which readily liquify by means of caloric, it is
not sufficient to carry off the water which held them in solution, but
the caloric united to them must likewise be removed. Nitrat of potash,
oxygenated muriat of potash, alum, sulphat of soda, &c. are examples of
this circumstance, as, to make these salts cristallize, refrigeration
must be added to evaporation. Such salts, on the contrary, as require
little caloric for being kept in solution, and which, from that
circumstance, are nearly equally soluble in cold and warm water, are
cristallizable by simply carrying off the water which holds them in
solution, and even recover their solid state in boiling water; such are
sulphat of lime, muriat of potash and of soda, and several others.
The art of refining saltpetre depends upon these properties of salts,
and upon their different degrees of solubility in hot and cold water.
This salt, as produced in the manufactories by the first operation, is
composed of many different salts; some are deliquescent, and not
susceptible of being cristallized, such as the nitrat and muriat of
lime; others are almost equally soluble in hot and cold water, as the
muriats of potash and of soda; and, lastly, the saltpetre, or nitrat of
potash, is greatly more soluble in hot than it is in cold water. The
operation is begun, by pouring upon this mixture of salts as much water
as will hold even the least soluble, the muriats of soda and of potash,
in solution; so long as it is hot, this quantity readily dissolves all
the saltpetre, but, upon cooling, the greater part of this salt
cristallizes, leaving about a sixth part remaining dissolved, and mixed
with the nitrat of lime and the two muriats. The nitre obtained by this
process is still somewhat impregnated with other salts, because it has
been cristallized from water in which these abound: It is completely
purified from these by a second solution in a small quantity of boiling
water, and second cristallization. The water remaining after these
cristallizations of nitre is still loaded with a mixture of saltpetre,
and other salts; by farther evaporation, crude saltpetre, or
rough-petre, as the workmen call it, is procured from it, and this is
purified by two fresh solutions and cristallizations.
The deliquescent earthy salts which do not contain the nitric acid are
rejected in this manufacture; but those which consist of that acid
neutralized by an earthy base are dissolved in water, the earth is
precipitated by means of potash, and allowed to subside; the clear
liquor is then decanted, evaporated, and allowed to cristallize. The
above management for refining saltpetre may serve as a general rule for
separating salts from each other which happen to be mixed together. The
nature of each must be considered, the proportion in which each
dissolves in given quantities of water, and the different solubility of
each in hot and cold water. If to these we add the property which some
salts possess, of being soluble in alkohol, or in a mixture of alkohol
and water, we have many resources for separating salts from each other
by means of cristallization, though it must be allowed that it is
extremely difficult to render this separation perfectly complete.
The vessels used for cristallization are pans of earthen ware, A, Pl.
II. Fig. 1. and 2. and large flat dishes, Pl. III. Fig. 7. When a saline
solution is to be exposed to a slow evaporation in the heat of the
atmosphere, with free access of air, vessels of some depth, Pl. III.
Fig. 3. must be employed, that there may be a considerable body of
liquid; by this means the cristals produced are of considerable size,
and remarkably regular in their figure.
Every species of salt cristallizes in a peculiar form, and even each
salt varies in the form of its cristals according to circumstances,
which take place during cristallization. We must not from thence
conclude that the saline particles of each species are indeterminate in
their figures: The primative particles of all bodies, especially of
salts, are perfectly constant in their specific forms; but the cristals
which form in our experiments are composed of congeries of minute
particles, which, though perfectly equal in size and shape, may assume
very dissimilar arrangements, and consequently produce a vast variety of
regular forms, which have not the smallest apparent resemblance to each
other, nor to the original cristal. This subject has been very ably
treated by the Abbé Haüy, in several memoirs presented to the Academy,
and in his work upon the structure of cristals: It is only necessary to
extend generally to the class of salts the principles he has
particularly applied to some cristalized stones.
SECT. V.
_Of Simple Distillation._
As distillation has two distinct objects to accomplish, it is divisible
into simple and compound; and, in this section, I mean to confine myself
entirely to the former. When two bodies, of which one is more volatile
than the other, or has more affinity to caloric, are submitted to
distillation, our intention is to separate them from each other: The
more volatile substance assumes the form of gas, and is afterwards
condensed by refrigeration in proper vessels. In this case distillation,
like evaporation, becomes a species of mechanical operation, which
separates two substances from each other without decomposing or altering
the nature of either. In evaporation, our only object is to preserve the
fixed body, without paying any regard to the volatile matter; whereas,
in distillation, our principal attention is generally paid to the
volatile substance, unless when we intend to preserve both the one and
the other. Hence, simple distillation is nothing more than evaporation
produced in close vessels.
The most simple distilling vessel is a species of bottle or matrass, A,
Pl. III. Fig. 8. which has been bent from its original form BC to BD,
and which is then called a retort; when used, it is placed either in a
reverberatory furnace, Pl. XIII. Fig. 2. or in a sand bath under a dome
of baked earth, Pl. III. Fig. 1. To receive and condense the products,
we adapt a recipient, E, Pl. III. Fig. 9. which is luted to the retort.
Sometimes, more especially in pharmaceutical operations, the glass or
stone ware cucurbit, A, with its capital B, Pl. III. Fig. 12, or the
glass alembic and capital, Fig. 13. of one piece, is employed. This
latter is managed by means of a tubulated opening T, fitted with a
ground stopper of cristal; the capital, both of the cucurbit and
alembic, has a furrow or trench, r r, intended for conveying the
condensed liquor into the beak RS, by which it runs out. As, in almost
all distillations, expansive vapours are produced, which might burst the
vessels employed, we are under the necessity of having a small hole, T,
Fig. 9. in the balloon or recipient, through which these may find vent;
hence, in this way of distilling, all the products which are permanently
aëriform are entirely lost, and even such as difficultly lose that state
have not sufficient space to condense in the balloon: This apparatus is
not, therefore, proper for experiments of investigation, and can only be
admitted in the ordinary operations of the laboratory or in pharmacy. In
the article appropriated for compound distillation, I shall explain the
various methods which have been contrived for preserving the whole
products from bodies in this process.
As glass or earthen vessels are very brittle, and do not readily bear
sudden alterations of heat and cold, every well regulated laboratory
ought to have one or more alembics of metal for distilling water,
spiritous liquors, essential oils, &c. This apparatus consists of a
cucurbit and capital of tinned copper or brass, Pl. III. Fig. 15. and
16. which, when judged proper, may be placed in the water bath, D, Fig.
17. In distillations, especially of spiritous liquors, the capital must
be furnished with a refrigetory, SS, Fig. 16. kept continually filled
with cold water; when the water becomes heated, it is let off by the
stop-cock, R, and renewed with a fresh supply of cold water. As the
fluid distilled is converted into gas by means of caloric furnished by
the fire of the furnace, it is evident that it could not condense, and,
consequently, that no distillation, properly speaking, could take place,
unless it is made to deposit in the capital all the caloric it received
in the cucurbit; with this view, the sides of the capital must always be
preserved at a lower temperature than is necessary for keeping the
distilling substance in the state of gas, and the water in the
refrigetory is intended for this purpose. Water is converted into gas
by the temperature of 80° (212°), alkohol by 67° (182.75°), ether by 32°
(104°); hence these substances cannot be distilled, or, rather, they
will fly off in the state of gas, unless the temperature of the
refrigetory be kept under these respective degrees.
In the distillation of spiritous, and other expansive liquors, the above
described refrigetory is not sufficient for condensing all the vapours
which arise; in this case, therefore, instead of receiving the distilled
liquor immediately from the beak, TU, of the capital into a recipient, a
worm is interposed between them. This instrument is represented Pl. III.
Fig. 18. contained in a worm tub of tinned copper, it consists of a
metallic tube bent into a considerable number of spiral revolutions. The
vessel which contains the worm is kept full of cold water, which is
renewed as it grows warm. This contrivance is employed in all
distilleries of spirits, without the intervention of a capital and
refrigetory, properly so called. The one represented in the plate is
furnished with two worms, one of them being particularly appropriated to
distillations of odoriferous substances.
In some simple distillations it is necessary to interpose an adopter
between the retort and receiver, as shown Pl. III. Fig, 11. This may
serve two different purposes, either to separate two products of
different degrees of volatility, or to remove the receiver to a greater
distance from the furnace, that it may be less heated. But these, and
several other more complicated instruments of ancient contrivance, are
far from producing the accuracy requisite in modern chemistry, as will
be readily perceived when I come to treat of compound distillation.
SECT. VI.
_Of Sublimation._
This term is applied to the distillation of substances which condense in
a concrete or solid form, such as the sublimation of sulphur, and of
muriat of ammoniac, or sal ammoniac. These operations may be
conveniently performed in the ordinary distilling vessels already
described, though, in the sublimation of sulphur, a species of vessels,
named Alludels, have been usually employed. These are vessels of stone
or porcelain ware, which adjust to each other over a cucurbit containing
the sulphur to be sublimed. One of the best subliming vessels, for
substances which are not very volatile, is a flask, or phial of glass,
sunk about two thirds into a sand bath; but in this way we are apt to
lose a part of the products. When these are wished to be entirely
preserved, we must have recourse to the pneumato-chemical distilling
apparatus, to be described in the following chapter.
CHAP. VI.
_Of Pneumato-chemical Distillations, Metallic Dissolutions, and some
other operations which require very complicated instruments._
SECT. I.
_Of Compound and Pneumato-chemical Distillations._
In the preceding chapter, I have only treated of distillation as a
simple operation, by which two substances, differing in degrees of
volatility, may be separated from each other; but distillation often
actually decomposes the substances submitted to its action, and becomes
one of the most complicated operations in chemistry. In every
distillation, the substance distilled must be brought to the state of
gas, in the cucurbit or retort, by combination with caloric: In simple
distillation, this caloric is given out in the refrigeratory or in the
worm, and the substance again recovers its liquid or solid form, but the
substances submitted to compound distillation are absolutely
decompounded; one part, as for instance the charcoal they contain,
remains fixed in the retort, and all the rest of the elements are
reduced to gasses of different kinds. Some of these are susceptible of
being condensed, and of recovering their solid or liquid forms, whilst
others are permanently aëriform; one part of these are absorbable by
water, some by the alkalies, and others are not susceptible of being
absorbed at all. An ordinary distilling apparatus, such as has been
described in the preceding chapter, is quite insufficient for retaining
or for separating these diversified products, and we are obliged to have
recourse, for this purpose, to methods of a more complicated nature.
The apparatus I am about to describe is calculated for the most
complicated distillations, and may be simplified according to
circumstances. It consists of a tubulated glass retort A, Pl. IV. Fig.
1. having its beak fitted to a tubulated balloon or recipient BC; to the
upper orifice D of the balloon a bent tube DEfg is adjusted, which, at
its other extremity g, is plunged into the liquor contained in the
bottle L, with three necks xxx. Three other similar bottles are
connected with this first one, by means of three similar bent tubes
disposed in the same manner; and the farthest neck of the last bottle is
connected with a jar in a pneumato-chemical apparatus, by means of a
bent tube[60]. A determinate weight of distilled water is usually put
into the first bottle, and the other three have each a solution of
caustic potash in water. The weight of all these bottles, and of the
water and alkaline solution they contain, must be accurately
ascertained. Every thing being thus disposed, the junctures between the
retort and recipient, and of the tube D of the latter, must be luted
with fat lute, covered over with slips of linen, spread with lime and
white of egg; all the other junctures are to be secured by a lute made
of wax and rosin melted together.
When all these dispositions are completed, and when, by means of heat
applied to the retort A, the substance it contains becomes decomposed,
it is evident that the least volatile products must condense or sublime
in the beak or neck of the retort itself, where most of the concrete
substances will fix themselves. The more volatile substances, as the
lighter oils, ammoniac, and several others, will condense in the
recipient GC, whilst the gasses, which are not susceptible of
condensation by cold, will pass on by the tubes, and boil up through the
liquors in the several bottles. Such as are absorbable by water will
remain in the first bottle, and those which caustic alkali can absorb
will remain in the others; whilst such gasses as are not susceptible of
absorption, either by water or alkalies, will escape by the tube RM, at
the end of which they may be received into jars in a pneumato-chemical
apparatus. The charcoal and fixed earth, &c. which form the substance or
residuum, anciently called _caput mortuum_, remain behind in the retort.
In this manner of operating, we have always a very material proof of the
accuracy of the analysis, as the whole weights of the products taken
together, after the process is finished, must be exactly equal to the
weight of the original substance submitted to distillation. Hence, for
instance, if we have operated upon eight ounces of starch or gum arabic,
the weight of the charry residuum in the retort, together with that of
all the products gathered in its neck and the balloon, and of all the
gas received into the jars by the tube RM added to the additional weight
acquired by the bottles, must, when taken together, be exactly eight
ounces. If the product be less or more, it proceeds from error, and the
experiment must be repeated until a satisfactory result be procured,
which ought not to differ more than six or eight grains in the pound
from the weight of the substance submitted to experiment.
In experiments of this kind, I for a long time met with an almost
insurmountable difficulty, which must at last have obliged me to desist
altogether, but for a very simple method of avoiding it, pointed out to
me by Mr Hassenfratz. The smallest diminution in the heat of the
furnace, and many other circumstances inseparable from this kind of
experiments, cause frequent reabsorptions of gas; the water in the
cistern of the pneumato-chemical apparatus rushes into the last bottle
through the tube RM, the same circumstance happens from one bottle into
another, and the fluid is often forced even into the recipient C. This
accident is prevented by using bottles having three necks, as
represented in the plate, into one of which, in each bottle, a capillary
glass-tube St, st, st, st, is adapted, so as to have its lower
extremity t immersed in the liquor. If any absorption takes place,
either in the retort, or in any of the bottles, a sufficient quantity of
external air enters, by means of these tubes, to fill up the void; and
we get rid of the inconvenience at the price of having a small mixture
of common air with the products of the experiment, which is thereby
prevented from failing altogether. Though these tubes admit the external
air, they cannot permit any of the gasseous substances to escape, as
they are always shut below by the water of the bottles.
It is evident that, in the course of experiments with this apparatus,
the liquor of the bottles must rise in these tubes in proportion to the
pressure sustained by the gas or air contained in the bottles; and this
pressure is determined by the height and gravity of the column of fluid
contained in all the subsequent bottles. If we suppose that each bottle
contains three inches of fluid, and that there are three inches of water
in the cistern of the connected apparatus above the orifice of the tube
RM, and allowing the gravity of the fluids to be only equal to that of
water, it follows that the air in the first bottle must sustain a
pressure equal to twelve inches of water; the water must therefore rise
twelve inches in the tube S, connected with the first bottle, nine
inches in that belonging to the second, six inches in the third, and
three in the last; wherefore these tubes must be made somewhat more than
twelve, nine, six, and three inches long respectively, allowance being
made for oscillatory motions, which often take place in the liquids. It
is sometimes necessary to introduce a similar tube between the retort
and recipient; and, as the tube is not immersed in fluid at its lower
extremity, until some has collected in the progress of the distillation,
its upper end must be shut at first with a little lute, so as to be
opened according to necessity, or after there is sufficient liquid in
the recipient to secure its lower extremity.
This apparatus cannot be used in very accurate experiments, when the
substances intended to be operated upon have a very rapid action upon
each other, or when one of them can only be introduced in small
successive portions, as in such as produce violent effervescence when
mixed together. In such cases, we employ a tubulated retort A, Pl. VII.
Fig. 1. into which one of the substances is introduced, preferring
always the solid body, if any such is to be treated, we then lute to the
opening of the retort a bent tube BCDA, terminating at its upper
extremity B in a funnel, and at its other end A in a capillary opening.
The fluid material of the experiment is poured into the retort by means
of this funnel, which must be made of such a length, from B to C, that
the column of liquid introduced may counterbalance the resistance
produced by the liquors contained in all the bottles, Pl. IV. Fig. 1.
Those who have not been accustomed to use the above described distilling
apparatus may perhaps be startled at the great number of openings which
require luting, and the time necessary for making all the previous
preparations in experiments of this kind. It is very true that, if we
take into account all the necessary weighings of materials and products,
both before and after the experiments, these preparatory and succeeding
steps require much more time and attention than the experiment itself.
But, when the experiment succeeds properly, we are well rewarded for all
the time and trouble bestowed, as by one process carried on in this
accurate manner much more just and extensive knowledge is acquired of
the nature of the vegetable or animal substance thus submitted to
investigation, than by many weeks assiduous labour in the ordinary
method of proceeding.
When in want of bottles with three orifices, those with two may be used;
it is even possible to introduce all the three tubes at one opening, so
as to employ ordinary wide-mouthed bottles, provided the opening be
sufficiently large. In this case we must carefully fit the bottles with
corks very accurately cut, and boiled in a mixture of oil, wax, and
turpentine. These corks are pierced with the necessary holes for
receiving the tubes by means of a round file, as in Pl. IV. Fig. 8.
SECT. II.
_Of Metallic Dissolutions._
I have already pointed out the difference between solution of salts in
water and metallic dissolutions. The former requires no particular
vessels, whereas the latter requires very complicated vessels of late
invention, that we may not lose any of the products of the experiment,
and may thereby procure truly conclusive results of the phenomena which
occur. The metals, in general, dissolve in acids with effervescence,
which is only a motion excited in the solvent by the disengagement of a
great number of bubbles of air or aëriform fluid, which proceed from the
surface of the metal, and break at the surface of the liquid.
Mr Cavendish and Dr Priestley were the first inventors of a proper
apparatus for collecting these elastic fluids. That of Dr Priestley is
extremely simple, and consists of a bottle A, Pl. VII. Fig. 2. with its
cork B, through which passes the bent glass tube BC, which is engaged
under a jar filled with water in the pneumato-chemical apparatus, or
simply in a bason full of water. The metal is first introduced into the
bottle, the acid is then poured over it, and the bottle is instantly
closed with its cork and tube, as represented in the plate. But this
apparatus has its inconveniencies. When the acid is much concentrated,
or the metal much divided, the effervescence begins before we have time
to cork the bottle properly, and some gas escapes, by which we are
prevented from ascertaining the quantity disengaged with rigorous
exactness. In the next place, when we are obliged to employ heat, or
when heat is produced by the process, a part of the acid distills, and
mixes with the water of the pneumato-chemical apparatus, by which means
we are deceived in our calculation of the quantity of acid decomposed.
Besides these, the water in the cistern of the apparatus absorbs all the
gas produced which is susceptible of absorption, and renders it
impossible to collect these without loss.
To remedy these inconveniencies, I at first used a bottle with two
necks, Pl. VII. Fig. 3. into one of which the glass funnel BC is luted
so as to prevent any air escaping; a glass rod DE is fitted with emery
to the funnel, so as to serve the purpose of a stopper. When it is used,
the matter to be dissolved is first introduced into the bottle, and the
acid is then permitted to pass in as slowly as we please, by raising the
glass rod gently as often as is necessary until saturation is produced.
Another method has been since employed, which serves the same purpose,
and is preferable to the last described in some instances. This consists
in adapting to one of the mouths of the bottle A, Pl. VII. Fig. 4. a
bent tube DEFG, having a capillary opening at D, and ending in a funnel
at G. This tube is securely luted to the mouth C of the bottle. When any
liquid is poured into the funnel, it falls down to F; and, if a
sufficient quantity be added, it passes by the curvature E, and falls
slowly into the bottle, so long as fresh liquor is supplied at the
funnel. The liquor can never be forced out of the tube, and no gas can
escape through it, because the weight of the liquid serves the purpose
of an accurate cork.
To prevent any distillation of acid, especially in dissolutions
accompanied with heat, this tube is adapted to the retort A, Pl. VII.
Fig. 1. and a small tubulated recipient, M, is applied, in which any
liquor which may distill is condensed. On purpose to separate any gas
that is absorbable by water, we add the double necked bottle L, half
filled with a solution of caustic potash; the alkali absorbs any
carbonic acid gas, and usually only one or two other gasses pass into
the jar of the connected pneumato-chemical apparatus through the tube
NO. In the first chapter of this third part we have directed how these
are to be separated and examined. If one bottle of alkaline solution be
not thought sufficient, two, three, or more, may be added.
SECT. III.
_Apparatus necessary in Experiments upon Vinous and Putrefactive
Fermentations._
For these operations a peculiar apparatus, especially intended for this
kind of experiment, is requisite. The one I am about to describe is
finally adopted, as the best calculated for the purpose, after numerous
corrections and improvements. It consists of a large matrass, A, Pl. X.
fig. 1. holding about twelve pints, with a cap of brass a b, strongly
cemented to its mouth, and into which is screwed a bent tube c d,
furnished with a stop-cock e. To this tube is joined the glass
recipient B, having three openings, one of which communicates with the
bottle C, placed below it. To the posterior opening of this recipient is
fitted a glass tube g h i, cemented at g and i to collets of
brass, and intended to contain a very deliquescent concrete neutral
salt, such as nitrat or muriat of lime, acetite of potash, &c. This tube
communicates with two bottles D and E, filled to x and y with a
solution of caustic potash.
All the parts of this machine are joined together by accurate screws,
and the touching parts have greased leather interposed, to prevent any
passage of air. Each piece is likewise furnished with two stop-cocks, by
which its two extremities may be closed, so that we can weigh each
separately at any period of the operation.
The fermentable matter, such as sugar, with a proper quantity of yeast,
and diluted with water, is put into the matrass. Sometimes, when the
fermentation is too rapid, a considerable quantity of froth is produced,
which not only fills the neck of the matrass, but passes into the
recipient, and from thence runs down into the bottle C. On purpose to
collect this scum and must, and to prevent it from reaching the tube
filled with deliquescent salts, the recipient and connected bottle are
made of considerable capacity.
In the vinous fermentation, only carbonic acid gas is disengaged,
carrying with it a small proportion of water in solution. A great part
of this water is deposited in passing through the tube g h i, which is
filled with a deliquescent salt in gross powder, and the quantity is
ascertained by the augmentation of the weight of the salt. The carbonic
acid gas bubbles up through the alkaline solution in the bottle D, to
which it is conveyed by the tube k l m. Any small portion which may
not be absorbed by this first bottle is secured by the solution in the
second bottle E, so that nothing, in general, passes into the jar F,
except the common air contained in the vessels at the commencement of
the experiment.
The same apparatus answers extremely well for experiments upon the
putrefactive fermentation; but, in this case, a considerable quantity of
hydrogen gas is disengaged through the tube q r s t u, by which it is
conveyed into the jar F; and, as this disengagement is very rapid,
especially in summer, the jar must be frequently changed. These
putrefactive fermentations require constant attendance from the above
circumstance, whereas the vinous fermentation hardly needs any. By means
of this apparatus we can ascertain, with great precision, the weights of
the substances submitted to fermentation, and of the liquid and aëriform
products which are disengaged. What has been already said in Part I.
Chap. XIII. upon the products of the vinous fermentation, may be
consulted.
SECT. IV.
_Apparatus for the Decomposition of Water._
Having already given an account, in the first part of this work, of the
experiments relative to the decomposition of water, I shall avoid any
unnecessary repetitions, and only give a few summary observations upon
the subject in this section. The principal substances which have the
power of decomposing water are iron and charcoal; for which purpose,
they require to be made red hot, otherwise the water is only reduced
into vapours, and condenses afterwards by refrigeration, without
sustaining the smallest alteration. In a red heat, on the contrary, iron
or charcoal carry off the oxygen from its union with hydrogen; in the
first case, black oxyd of iron is produced, and the hydrogen is
disengaged pure in form of gas; in the other case, carbonic acid gas is
formed, which disengages, mixed with the hydrogen gas; and this latter
is commonly carbonated, or holds charcoal in solution.
A musket barrel, without its breach pin, answers exceedingly well for
the decomposition of water, by means of iron, and one should be chosen
of considerable length, and pretty strong. When too short, so as to run
the risk of heating the lute too much, a tube of copper is to be
strongly soldered to one end. The barrel is placed in a long furnace,
CDEF, Pl. VII. Fig. 11. so as to have a few degrees of inclination from
E to F; a glass retort A, is luted to the upper extremity E, which
contains water, and is placed upon the furnace VVXX. The lower extremity
F is luted to a worm SS, which is connected with the tubulated bottle H,
in which any water distilled without decomposition, during the
operation, collects, and the disengaged gas is carried by the tube KK to
jars in a pneumato-chemical apparatus. Instead of the retort a funnel
may be employed, having its lower part shut by a stop-cock, through
which the water is allowed to drop gradually into the gun-barrel.
Immediately upon getting into contact with the heated part of the iron,
the water is converted into steam, and the experiment proceeds in the
same manner as if it were furnished in vapours from the retort.
In the experiment made by Mr Meusnier and me before a committee of the
Academy, we used every precaution to obtain the greatest possible
precision in the result of our experiment, having even exhausted all the
vessels employed before we began, so that the hydrogen gas obtained
might be free from any mixture of azotic gas. The results of that
experiment will hereafter be given at large in a particular memoir.
In numerous experiments, we are obliged to use tubes of glass,
porcelain, or copper, instead of gun-barrels; but glass has the
disadvantage of being easily melted and flattened, if the heat be in the
smallest degree raised too high; and porcelain is mostly full of small
minute pores, through which the gas escapes, especially when compressed
by a column of water. For these reasons I procured a tube of brass,
which Mr de la Briche got cast and bored out of the solid for me at
Strasburg, under his own inspection. This tube is extremely convenient
for decomposing alkohol, which resolves into charcoal, carbonic acid
gas, and hydrogen gas; it may likewise be used with the same advantage
for decomposing water by means of charcoal, and in a great number of
experiments of this nature.
FOOTNOTES:
[60] The representation of this apparatus, Pl. IV. Fig. 1. will convey a
much better idea of its disposition than can possibly be given by the
most laboured description.--E.
CHAP. VII.
_Of the Composition and Application of Lutes._
The necessity of properly securing the junctures of chemical vessels to
prevent the escape of any of the products of experiments, must be
sufficiently apparent; for this purpose lutes are employed, which ought
to be of such a nature as to be equally impenetrable to the most subtile
substances, as glass itself, through which only caloric can escape.
This first object of lutes is very well accomplished by bees wax, melted
with about an eighth part of turpentine. This lute is very easily
managed, sticks very closely to glass, and is very difficultly
penetrable; it may be rendered more consistent, and less or more hard or
pliable, by adding different kinds of resinous matters. Though this
species of lute answers extremely well for retaining gasses and vapours,
there are many chemical experiments which produce considerable heat, by
which this lute becomes liquified, and consequently the expansive
vapours must very readily force through and escape.
For such cases, the following fat lute is the best hitherto discovered,
though not without its disadvantages, which shall be pointed out. Take
very pure and dry unbaked clay, reduced to a very fine powder, put this
into a brass mortar, and beat it for several hours with a heavy iron
pestle, dropping in slowly some boiled lintseed oil; this is oil which
has been oxygenated, and has acquired a drying quality, by being boiled
with litharge. This lute is more tenacious, and applies better, if amber
varnish be used instead of the above oil. To make this varnish, melt
some yellow amber in an iron laddle, by which operation it loses a part
of its succinic acid, and essential oil, and mix it with lintseed oil.
Though the lute prepared with this varnish is better than that made with
boiled oil, yet, as its additional expence is hardly compensated by its
superior quality, it is seldom used.
The above fat lute is capable of sustaining a very violent degree of
heat, is impenetrable by acids and spiritous liquors, and adheres
exceedingly well to metals, stone ware, or glass, providing they have
been previously rendered perfectly dry. But if, unfortunately, any of
the liquor in the course of an experiment gets through, either between
the glass and the lute, or between the layers of the lute itself, so as
to moisten the part, it is extremely difficult to close the opening.
This is the chief inconvenience which attends the use of fat lute, and
perhaps the only one it is subject to. As it is apt to soften by heat,
we must surround all the junctures with slips of wet bladder applied
over the luting, and fixed on by pack-thread tied round both above and
below the joint; the bladder, and consequently the lute below, must be
farther secured by a number of turns of pack-thread all over it. By
these precautions, we are free from every danger of accident; and the
junctures secured in this manner may be considered, in experiments, as
hermetically sealed.
It frequently happens that the figure of the junctures prevents the
application of ligatures, which is the case with the three-necked
bottles formerly described; and it even requires great address to apply
the twine without shaking the apparatus; so that, where a number of
junctures require luting, we are apt to displace several while securing
one. In these cases, we may substitute slips of linen, spread with white
of egg and lime mixed together, instead of the wet bladder. These are
applied while still moist, and very speedily dry and acquire
considerable hardness. Strong glue dissolved in water may answer instead
of white of egg. These fillets are usefully applied likewise over
junctures luted together with wax and rosin.
Before applying a lute, all the junctures of the vessels must be
accurately and firmly fitted to each other, so as not to admit of being
moved. If the beak of a retort is to be luted to the neck of a
recipient, they ought to fit pretty accurately; otherwise we must fix
them, by introducing short pieces of soft wood or of cork. If the
disproportion between the two be very considerable, we must employ a
cork which fits the neck of the recipient, having a circular hole of
proper dimensions to admit the beak of the retort. The same precaution
is necessary in adapting bent tubes to the necks of bottles in the
apparatus represented Pl. IV. Fig. 1. and others of a similar nature.
Each mouth of each bottle must be fitted with a cork, having a hole made
with a round file of a proper size for containing the tube. And, when
one mouth is intended to admit two or more tubes, which frequently
happens when we have not a sufficient number of bottles with two or
three necks, we must use a cork with two or three holes, Pl. IV. Fig. 8.
When the whole apparatus is thus solidly joined, so that no part can
play upon another, we begin to lute. The lute is softened by kneading
and rolling it between the fingers, with the assistance of heat, if
necessary. It is rolled into little cylindrical pieces, and applied to
the junctures, taking great care to make it apply close, and adhere
firmly, in every part; a second roll is applied over the first, so as to
pass it on each side, and so on till each juncture be sufficiently
covered; after this, the slips of bladder, or of linen, as above
directed, must be carefully applied over all. Though this operation may
appear extremely simple, yet it requires peculiar delicacy and
management; great care must be taken not to disturb one juncture whilst
luting another, and more especially when applying the fillets and
ligatures.
Before beginning any experiment, the closeness of the luting ought
always to be previously tried, either by slightly heating the retort A,
Pl. IV. Fig. 1, or by blowing in a little air by some of the
perpendicular tubes S s s s; the alteration of pressure causes a
change in the level of the liquid in these tubes. If the apparatus be
accurately luted, this alteration of level will be permanent; whereas,
if there be the smallest, opening in any of the junctures, the liquid
will very soon recover its former level. It must always be remembered,
that the whole success of experiments in modern chemistry depends upon
the exactness of this operation, which therefore requires the utmost
patience, and most attentive accuracy.
It would be of infinite service to enable chemists, especially those who
are engaged in pneumatic processes, to dispense with the use of lutes,
or at least to diminish the number necessary in complicated instruments.
I once thought of having my apparatus constructed so as to unite in all
its parts by fitting with emery, in the way of bottles with cristal
stoppers; but the execution of this plan was extremely difficult. I have
since thought it preferable to substitute columns of a few lines of
mercury in place of lutes, and have got an apparatus constructed upon
this principle, which appears capable of very convenient application in
a great number of circumstances.
It consists of a double necked bottle A, Pl. XII. Fig. 12.; the interior
neck bc communicates with the inside of the bottle, and the exterior
neck or rim de leaves an interval between the two necks, forming a
deep gutter intended to contain the mercury. The cap or lid of glass B
enters this gutter, and is properly fitted to it, having notches in its
lower edge for the passage of the tubes which convey the gas. These
tubes, instead of entering directly into the bottles as in the ordinary
apparatus, have a double bend for making them enter the gutter, as
represented in Fig. 13. and for making them fit the notches of the cap
B; they rise again from the gutter to enter the inside of the bottle
over the border of the inner mouth. When the tubes are disposed in their
proper places, and the cap firmly fitted on, the gutter is filled with
mercury, by which means the bottle is completely excluded from any
communication, excepting through the tubes. This apparatus may be very
convenient in many operations in which the substances employed have no
action upon Mercury. Pl. XII. Fig. 14. represents an apparatus upon this
principle properly fitted together.
Mr Seguin, to whose active and intelligent assistance I have been very
frequently much indebted, has bespoken for me, at the glass-houses, some
retorts hermetically united to their recipients, by which luting will be
altogether unnecessary.
CHAP. VIII.
_Of Operations upon Combustion and Deflagration._
SECT. I.
_Of Combustion in general._
Combustion, according to what has been already said in the First Part of
this Work, is the decomposition of oxygen gas produced by a combustible
body. The oxygen which forms the base of this gas is absorbed by, and
enters into, combination with the burning body, while the caloric and
light are set free. Every combustion, therefore, necessarily supposes
oxygenation; whereas, on the contrary, every oxygenation does not
necessarily imply concomitant combustion; because combustion, properly
so called, cannot take place without disengagement of caloric and light.
Before combustion can take place, it is necessary that the base of
oxygen gas should have greater affinity to the combustible body than it
has to caloric; and this elective attraction, to use Bergman's
expression, can only take place at a certain degree of temperature,
which is different for each combustible substance; hence the necessity
of giving a first motion or beginning to every combustion by the
approach of a heated body. This necessity of heating any body we mean to
burn depends upon certain considerations, which have not hitherto been
attended to by any natural philosopher, for which reason I shall enlarge
a little upon the subject in this place.
Nature is at present in a state of equilibrium, which cannot have been
attained until all the spontaneous combustions or oxygenations possible
in the ordinary degrees of temperature had taken place. Hence, no new
combustions or oxygenations can happen without destroying this
equilibrium, and raising the combustible substances to a superior degree
of temperature. To illustrate this abstract view of the matter by
example: Let us suppose the usual temperature of the earth a little
changed, and that it is raised only to the degree of boiling water; it
is evident, that, in this case, phosphorus, which is combustible in a
considerably lower degree of temperature, would no longer exist in
nature in its pure and simple state, but would always be procured in its
acid or oxygenated state, and its radical would become one of the
substances unknown to chemistry. By gradually increasing the
temperature of the earth the same circumstance would successively happen
to all the bodies capable of combustion; and, at last, every possible
combustion having taken place, there would no longer exist any
combustible body whatever, as every substance susceptible of that
operation would be oxygenated, and consequently incombustible.
There cannot therefore exist, so far as relates to us, any combustible
body, except such as are incombustible in the ordinary temperatures of
the earth; or, what is the same thing, in other words, that it is
essential to the nature of every combustible body not to possess the
property of combustion, unless heated, or raised to the degree of
temperature at which its combustion naturally takes place. When this
degree is once produced, combustion commences, and the caloric which is
disengaged by the decomposition of the oxygen gas keeps up the
temperature necessary for continuing combustion. When this is not the
case, that is, when the disengaged caloric is insufficient for keeping
up the necessary temperature, the combustion ceases: This circumstance
is expressed in common language by saying, that a body burns ill, or
with difficulty.
Although combustion possesses some circumstances in common with
distillation, especially with the compound kind of that operation, they
differ in a very material point. In distillation there is a separation
of one part of the elements of the substance from each other, and a
combination of these, in a new order, occasioned by the affinities which
take place in the increased temperature produced during distillation:
This likewise happens in combustion, but with this farther circumstance,
that a new element, not originally in the body, is brought into action;
oxygen is added to the substance submitted to the operation, and caloric
is disengaged.
The necessity of employing oxygen in the state of gas in all experiments
with combustion, and the rigorous determination of the quantities
employed, render this kind of operations peculiarly troublesome. As
almost all the products of combustion are disengaged in the state of
gas, it is still more difficult to retain them than even those furnished
during compound distillation; hence this precaution was entirely
neglected by the ancient chemists; and this set of experiments
exclusively belong to modern chemistry.
Having thus pointed out, in a general way, the objects to be had in view
in experiments upon combustion, I proceed, in the following sections of
this chapter, to describe the different instruments I have used with
this view. The following arrangement is formed, not upon the nature of
the combustible bodies, but upon that of the instruments necessary for
combustion.
SECT. II.
_Of the Combustion of Phosphorus._
In these combustions we begin by filling a jar, capable at least of
holding six pints, with oxygen gas in the water apparatus, Pl. V. Fig.
1.; when it is perfectly full, so that the gas begins to flow out below,
the jar, A, is carried to the mercury apparatus, Pl. IV. Fig. 3. We then
dry the surface of the mercury, both within and without the jar, by
means of blotting-paper, taking care to keep the paper for some time
entirely immersed in the mercury before it is introduced under the jar,
lest we let in any common air, which sticks very obstinately to the
surface of the paper. The body to be submitted to combustion, being
first very accurately weighed in nice scales, is placed in a small flat
shallow dish, D, of iron or porcelain; this is covered by the larger cup
P, which serves the office of a diving bell, and the whole is passed
through the mercury into the jar, after which the larger cup is retired.
The difficulty of passing the materials of combustion in this manner
through the mercury may be avoided by raising one of the sides of the
jar, A, for a moment, and slipping in the little cup, D, with the
combustible body as quickly as possible. In this manner of operating, a
small quantity of common air gets into the jar, but it is so very
inconsiderable as not to injure either the progress or accuracy of the
experiment in any sensible degree.
When the cup, D, is introduced under the jar, we suck out a part of the
oxygen gas, so as to raise the mercury to EF, as formerly directed, Part
I. Chap. V. otherwise, when the combustible body is set on fire, the gas
becoming dilated would be in part forced out, and we should no longer be
able to make any accurate calculation of the quantities before and after
the experiment. A very convenient mode of drawing out the air is by
means of an air-pump syringe adapted to the syphon, GHI, by which the
mercury may be raised to any degree under twenty-eight inches. Very
inflammable bodies, as phosphorus, are set on fire by means of the
crooked iron wire, MN, Pl. IV. Fig. 16. made red hot, and passed quickly
through the mercury. Such as are less easily set on fire have a small
portion of tinder, upon which a minute particle of phosphorus is fixed,
laid upon them before using the red hot iron.
In the first moment of combustion the air, being heated, rarifies, and
the mercury descends; but when, as in combustions of phosphorus and
iron, no elastic fluid is formed, absorption becomes presently very
sensible, and the mercury rises high into the jar. Great attention must
be used not to burn too large a quantity of any substance in a given
quantity of gas, otherwise, towards the end of the experiment, the cup
would approach so near the top of the jar as to endanger breaking it by
the great heat produced, and the sudden refrigeration from the cold
mercury. For the methods of measuring the volume of the gasses, and for
correcting the measures according to the heighth of the barometer and
thermometer, &c. see Chap. II. Sect. V. and VI. of this part.
The above process answers very well for burning all the concrete
substances, and even for the fixed oils: These last are burnt in lamps
under the jar, and are readily set on fire by means of tinder,
phosphorus, and hot iron. But it is dangerous for substances susceptible
of evaporating in a moderate heat, such as ether, alkohol, and the
essential oils; these substances dissolve in considerable quantity in
oxygen gas; and, when set on fire, a dangerous and sudden explosion
takes place, which carries up the jar to a great height, and dashes it
in a thousand pieces. From two such explosions some of the members of
the Academy and myself escaped very narrowly. Besides, though this
manner of operating is sufficient for determining pretty accurately the
quantity of oxygen gas absorbed, and of carbonic acid produced, as water
is likewise formed in all experiments upon vegetable and animal matters
which contain an excess of hydrogen, this apparatus can neither collect
it nor determine its quantity. The experiment with phosphorus is even
incomplete in this way, as it is impossible to demonstrate that the
weight of the phosphoric acid produced is equal to the sum of the
weights of the phosphorus burnt and oxygen gas absorbed during the
process. I have been therefore obliged to vary the instruments according
to circumstances, and to employ several of different kinds, which I
shall describe in their order, beginning with that used for burning
phosphorus.
Take a large balloon, A, Pl. IV. Fig. 4. of cristal or white glass, with
an opening, EF, about two inches and a half, or three inches, diameter,
to which a cap of brass is accurately fitted with emery, and which has
two holes for the passage of the tubes xxx, yyy. Before shutting the
balloon with its cover, place within it the stand, BC, supporting the
cup of porcelain, D, which contains the phosphorus. Then lute on the cap
with fat lute, and allow it to dry for some days, and weigh the whole
accurately; after this exhaust the balloon by means of an air-pump
connected with the tube xxx, and fill it with oxygen gas by the tube
yyy, from the gazometer, Pl. VIII. Fig. 1. described Chap. II. Sect
II. of this part. The phosphorus is then set on fire by means of a
burning-glass, and is allowed to burn till the cloud of concrete
phosphoric acid stops the combustion, oxygen gas being continually
supplied from the gazometer. When the apparatus has cooled, it is
weighed and unluted; the tare of the instrument being allowed, the
weight is that of the phosphoric acid contained. It is proper, for
greater accuracy, to examine the air or gas contained in the balloon
after combustion, as it may happen to be somewhat heavier or lighter
than common air; and this difference of weight must be taken into
account in the calculations upon the results of the experiment.
SECT. III.
_Of the Combustion of Charcoal._
The apparatus I have employed for this process consists of a small
conical furnace of hammered copper, represented in perspective, Pl. XII.
Fig. 9. and internally displayed Fig. 11. It is divided into the
furnace, ABC, where the charcoal is burnt, the grate, d e, and the
ash-hole, F; the tube, GH, in the middle of the dome of the furnace
serves to introduce the charcoal, and as a chimney for carrying off the
air which has served for combustion. Through the tube, l m n, which
communicates with the gazometer, the hydrogen gas, or air, intended for
supporting the combustion, is conveyed into the ash-hole, F, whence it
is forced, by the application of pressure to the gazometer, to pass
through the grate, d e, and to blow upon the burning charcoal placed
immediately above.
Oxygen gas, which forms 28/100 of atmospheric air, is changed into
carbonic acid gas during combustion with charcoal, whilst the azotic gas
of the air is not altered at all. Hence, after the combustion of
charcoal in atmospheric air, a mixture of carbonic acid gas and azotic
gas must remain; to allow this mixture to pass off, the tube, o p, is
adapted to the chimney, GH, by means of a screw at G, and conveys the
gas into bottles half filled with solution of caustic potash. The
carbonic acid gas is absorbed by the alkali, and the azotic gas is
conveyed into a second gazometer, where its quantity is ascertained.
The weight of the furnace, ABC, is first accurately determined, then
introduce the tube RS, of known weight, by the chimney, GH, till its
lower end S, rests upon the grate, d e, which it occupies entirely; in
the next place, fill the furnace with charcoal, and weigh the whole
again, to know the exact quantity of charcoal submitted to experiment.
The furnace is now put in its place, the tube, l m n, is screwed to
that which communicates with the gazometer, and the tube, o p, to that
which communicates with the bottles of alkaline solution. Every thing
being in readiness, the stop-cock of the gazometer is opened, a small
piece of burning charcoal is thrown into the tube, RS, which is
instantly withdrawn, and the tube, o p, is screwed to the chimney, GH.
The little piece of charcoal falls upon the grate, and in this manner
gets below the whole charcoal, and is kept on fire by the stream of air
from the gazometer. To be certain that the combustion is begun, and goes
on properly, the tube, q r s, is fixed to the furnace, having a piece
of glass cemented to its upper extremity, s, through which we can see
if the charcoal be on fire.
I neglected to observe above, that the furnace, and its appendages, are
plunged in water in the cistern, TVXY, Fig. 11. Pl. XII. to which ice
may be added to moderate the heat, if necessary; though the heat is by
no means very considerable, as there is no air but what comes from the
gazometer, and no more of the charcoal burns at one time than what is
immediately over the grate.
As one piece of charcoal is consumed another falls down into its place,
in consequence of the declivity of the sides of the furnace; this gets
into the stream of air from the grate, d e, and is burnt; and so on,
successively, till the whole charcoal is consumed. The air which has
served the purpose of the combustion passes through the mass of
charcoal, and is forced by the pressure of the gazometer to escape
through the tube, o p, and to pass through the bottles of alkaline
solution.
This experiment furnishes all the necessary data for a complete analysis
of atmospheric air and of charcoal. We know the weight of charcoal
consumed; the gazometer gives us the measure of the air employed; the
quantity and quality of gas remaining after combustion may be
determined, as it is received, either in another gazometer, or in jars,
in a pneumato-chemical apparatus; the weight of ashes remaining in the
ash-hole is readily ascertained; and, finally, the additional weight
acquired by the bottles of alkaline solution gives the exact quantity of
carbonic acid formed during the process. By this experiment we may
likewise determine, with sufficient accuracy, the proportions in which
charcoal and oxygen enter into the composition of carbonic acid.
In a future memoir I shall give an account to the Academy of a series of
experiments I have undertaken, with this instrument, upon all the
vegetable and animal charcoals. By some very slight alterations, this
machine may be made to answer for observing the principal phenomena of
respiration.
SECT. IV.
_Of the Combustion of Oils._
Oils are more compound in their nature than charcoal, being formed by
the combination of at least two elements, charcoal and hydrogen; of
course, after their combustion in common air, water, carbonic acid gas,
and azotic gas, remain. Hence the apparatus employed for their
combustion requires to be adapted for collecting these three products,
and is consequently more complicated than the charcoal furnace.
The apparatus I employ for this purpose is composed of a large jar or
pitcher A, Pl. XII. Fig. 4. surrounded at its upper edge by a rim of
iron properly cemented at DE, and receding from the jar at BC, so as to
leave a furrow or gutter xx, between it and the outside of the jar,
somewhat more than two inches deep. The cover or lid of the jar, Fig. 5.
is likewise surrounded by an iron rim f g, which adjusts into the
gutter xx, Fig. 4. which being filled with mercury, has the effect of
closing the jar hermetically in an instant, without using any lute; and,
as the gutter will hold about two inches of mercury, the air in the jar
may be made to sustain the pressure of more than two feet of water,
without danger of its escaping.
The lid has four holes, T h i k, for the passage of an equal
number of tubes. The opening T is furnished with a leather box, through
which passes the rod, Fig. 3. intended for raising and lowering the wick
of the lamp, as will be afterwards directed. The three other holes are
intended for the passage of three several tubes, one of which conveys
the oil to the lamp, a second conveys air for keeping up the combustion,
and the third carries off the air, after it has served for combustion.
The lamp in which the oil is burnt is represented Fig. 2; a is the
reservoir of oil, having a funnel by which it is filled; b c d e f g h
is a syphon which conveys the oil to the lamp 11; 7, 8, 9, 10, is the
tube which conveys the air for combustion from the gazometer to the same
lamp. The tube b c is formed externally, at its lower end b, into a
male screw, which turns in a female screw in the lid of the reservoir of
oil a; so that, by turning the reservoir one way or the other, it is
made to rise or fall, by which the oil is kept at the necessary level.
When the syphon is to be filled, and the communication formed between
the reservoir of oil and the lamp, the stop-cock c is shut, and that
at e opened, oil is poured in by the opening f at the top of the
syphon, till it rises within three or four lines of the upper edge of
the lamp, the stop-cock k is then shut, and that at c opened; the
oil is then poured in at f, till the branch b c d of the syphon is
filled, and then the stop-cock e is closed. The two branches of the
syphon being now completely filled, a communication is fully established
between the reservoir and the lamp.
In Pl. XII. Fig. 1. all the parts of the lamp 11, Fig. 2. are
represented magnified, to show them distinctly. The tube i k carries
the oil from the reservoir to the cavity a a a a, which contains the
wick; the tube 9, 10, brings the air from the gazometer for keeping up
the combustion; this air spreads through the cavity d d d d, and, by
means of the passages c c c c and b b b b, is distributed on each
side of the wick, after the principles of the lamps constructed by
Argand, Quinquet, and Lange.
To render the whole of this complicated apparatus more easily
understood, and that its description may make all others of the same
kind more readily followed, it is represented, completely connected
together for use, in Pl. XI. The gazometer P furnishes air for the
combustion by the tube and stop-cock 1, 2; the tube 2, 3, communicates
with a second gazometer, which is filled whilst the first one is
emptying during the process, that there may be no interruption to the
combustion; 4, 5, is a tube of glass filled with deliquescent salts, for
drying the air as much as possible in its passage; and the weight of
this tube and its contained salts, at the beginning of the experiment,
being known, it is easy to determine the quantity of water absorbed by
them from the air. From this deliquescent tube the air is conducted
through the pipe 5, 6, 7, 8, 9, 10, to the lamp 11, where it spreads on
both sides of the wick, as before described, and feeds the flame. One
part of this air, which serves to keep up the combustion of the oil,
forms carbonic acid gas and water, by oxygenating its elements. Part of
this water condenses upon the sides of the pitcher A, and another part
is held in solution in the air by means of caloric furnished by the
combustion. This air is forced by the compression of the gazometer to
pass through the tube 12, 13, 14, 15, into the bottle 16, and the worm
17, 18, where the water is fully condensed from the refrigeration of the
air; and, if any water still remains in solution, it is absorbed by
deliquescent salts contained in the tube 19, 20.
All these precautions are solely intended for collecting and determining
the quantity of water formed during the experiment; the carbonic acid
and azotic gas remains to be ascertained. The former is absorbed by
caustic alkaline solution in the bottles 22 and 25. I have only
represented two of these in the figure, but nine at least are requisite;
and the last of the series may be half filled with lime-water, which is
the most certain reagent for indicating the presence of carbonic acid;
if the lime-water is not rendered turbid, we may be certain that no
sensible quantity of that acid remains in the air.
The rest of the air which has served for combustion, and which chiefly
consists of azotic gas, though still mixed with a considerable portion
of oxygen gas, which has escaped unchanged from the combustion, is
carried through a third tube 28, 29, of deliquescent salts, to deprive
it of any moisture it may have acquired in the bottles of alkaline
solution and lime-water, and from thence by the tube 29, 30, into a
gazometer, where its quantity is ascertained. Small essays are then
taken from it, which are exposed to a solution of sulphuret of potash,
to ascertain the proportions of oxygen and azotic gas it contains.
In the combustion of oils the wick becomes charred at last, and
obstructs the rise of the oil; besides, if we raise the wick above a
certain height, more oil rises through its capillary tubes than the
stream of air is capable of consuming, and smoke is produced. Hence it
is necessary to be able to lengthen or shorten the wick without opening
the apparatus; this is accomplished by means of the rod 31, 32, 33, 34,
which passes through a leather-box, and is connected with the support of
the wick; and that the motion of this rod, and consequently of the wick,
may be regulated with the utmost smoothness and facility; it is moved at
pleasure by a pinnion which plays in a toothed rack. The rod, with its
appendages, are represented Pl. XII. Fig. 3. It appeared to me, that the
combustion would be assisted by surrounding the flame of the lamp with a
small glass jar open at both ends, as represented in its place in Pl.
XI.
I shall not enter into a more detailed description of the construction
of this apparatus, which is still capable of being altered and modified
in many respects, but shall only add, that when it is to be used in
experiment, the lamp and reservoir with the contained oil must be
accurately weighed, after which it is placed as before directed, and
lighted; having then formed the connection between the air in the
gazometer and the lamp, the external jar A, Pl. XI. is fixed over all,
and secured by means of the board BC and two rods of iron which connect
this board with the lid, and are screwed to it. A small quantity of oil
is burnt while the jar is adjusting to the lid, and the product of that
combustion is lost; there is likewise a small portion of air from the
gazometer lost at the same time. Both of these are of very
inconsiderable consequence in extensive experiments, and they are even
capable of being valued in our calculation of the results.
In a particular memoir, I shall give an account to the Academy of the
difficulties inseparable from this kind of experiments: These are so
insurmountable and troublesome, that I have not hitherto been able to
obtain any rigorous determination of the quantities of the products. I
have sufficient proof, however, that the fixed oils are entirely
resolved during combustion into water and carbonic acid gas, and
consequently that they are composed of hydrogen and charcoal; but I have
no certain knowledge respecting the proportions of these ingredients.
SECT. V.
_Of the Combustion of Alkohol._
The combustion of alkohol may be very readily performed in the apparatus
already described for the combustion of charcoal and phosphorus. A lamp
filled with alkohol is placed under the jar A, Pl. IV. Fig. 3. a small
morsel of phosphorus is placed upon the wick of the lamp, which is set
on fire by means of the hot iron, as before directed. This process is,
however, liable to considerable inconveniency; it is dangerous to make
use of oxygen gas at the beginning of the experiment for fear of
deflagration, which is even liable to happen when common air is
employed. An instance of this had very near proved fatal to myself, in
presence of some members of the Academy. Instead of preparing the
experiment, as usual, at the time it was to be performed, I had disposed
every thing in order the evening before; the atmospheric air of the jar
had thereby sufficient time to dissolve a good deal of the alkohol; and
this evaporation had even been considerably promoted by the height of
the column of mercury, which I had raised to EF, Pl. IV. Fig. 3. The
moment I attempted to set the little morsel of phosphorus on fire by
means of the red hot iron, a violent explosion took place, which threw
the jar with great violence against the floor of the laboratory, and
dashed it in a thousand pieces.
Hence we can only operate upon very small quantities, such as ten or
twelve grains of alkohol, in this manner; and the errors which may be
committed in experiments upon such small quantities prevents our placing
any confidence in their results. I endeavoured to prolong the
combustion, in the experiments contained in the Memoirs of the Academy
for 1784, p. 593. by lighting the alkohol first in common air, and
furnishing oxygen gas afterwards to the jar, in proportion as it
consumed; but the carbonic acid gas produced by the process became a
great hinderance to the combustion, the more so that alkohol is but
difficultly combustible, especially in worse than common air; so that
even in this way very small quantities only could be burnt.
Perhaps this combustion might succeed better in the oil apparatus, Pl.
XI.; but I have not hitherto ventured to try it. The jar A in which the
combustion is performed is near 1400 cubical inches in dimension; and,
were an explosion to take place in such a vessel, its consequences would
be very terrible, and very difficult to guard against. I have not,
however, despaired of making the attempt.
From all these difficulties, I have been hitherto obliged to confine
myself to experiments upon very small quantities of alkohol, or at least
to combustions made in open vessels, such as that represented in Pl. IX.
Fig. 5. which will be described in Section VII. of this chapter. If I am
ever able to remove these difficulties, I shall resume this
investigation.
SECT. VI.
_Of the Combustion of Ether._
Tho' the combustion of ether in close vessels does not present the same
difficulties as that of alkohol, yet it involves some of a different
kind, not more easily overcome, and which still prevent the progress of
my experiments. I endeavoured to profit by the property which ether
possesses of dissolving in atmospheric air, and rendering it inflammable
without explosion. For this purpose, I constructed the reservoir of
ether a b c d, Plate XII. Fig. 8. to which air is brought from the
gazometer by the tube 1, 2, 3, 4. This air spreads, in the first place,
in the double lid ac of the reservoir, from which it passes through
seven tubes ef, gh, ik, &c. which descend to the bottom of the
ether, and it is forced by the pressure of the gazometer to boil up
through the ether in the reservoir. We may replace the ether in this
first reservoir, in proportion as it is dissolved and carried off by the
air, by means of the supplementary reservoir E, connected by a brass
tube fifteen or eighteen inches long, and shut by a stop-cock. This
length of the connecting tube is to enable the descending ether to
overcome the resistance occasioned by the pressure of the air from the
gazometer.
The air, thus loaded with vapours of ether, is conducted by the tube 5,
6, 7, 8, 9, to the jar A, into which it is allowed to escape through a
capillary opening, at the extremity of which it is set on fire. The air,
when it has served the purpose of combustion, passes through the bottle
16, Pl. XI. the worm 17, 18, and the deliquescent tube 19, 20, after
which it passes through the alkaline bottles; in these its carbonic acid
gas is absorbed, the water formed during the experiment having been
previously deposited in the former parts of the apparatus.
When I caused construct this apparatus, I supposed that the combination
of atmospheric air and ether formed in the reservoir a b c d, Pl. XII.
Fig. 8. was in proper proportion for supporting combustion; but in this
I was mistaken; for there is a very considerable quantity of excess of
ether; so that an additional quantity of atmospheric air is necessary
to enable it to burn fully. Hence a lamp constructed upon these
principles will burn in common air, which furnishes the quantity of
oxygen necessary for combustion, but will not burn in close vessels in
which the air is not renewed. From this circumstance, my ether lamp went
out soon after being lighted and shut up in the jar A, Pl. XII. Fig. 8.
To remedy this defect, I endeavoured to bring atmospheric air to the
lamp by the lateral tube 10, 11, 12, 13, 14, 15, which I distributed
circularly round the flame; but the flame is so exceedingly rare, that
it is blown out by the gentlest possible stream of air, so that I have
not hitherto succeeded in burning ether. I do not, however, despair of
being able to accomplish it by means of some changes I am about to have
made upon this apparatus.
SECT. VII.
_Of the Combustion of Hydrogen Gas, and the Formation of Water._
In the formation of water, two substances, hydrogen and oxygen, which
are both in the aëriform state before combustion, are transformed into
liquid or water by the operation. This experiment would be very easy,
and would require very simple instruments, if it were possible to
procure the two gasses perfectly pure, so that they might burn without
any residuum. We might, in that case, operate in very small vessels,
and, by continually furnishing the two gasses in proper proportions,
might continue the combustion indefinitely. But, hitherto, chemists have
only employed oxygen gas, mixed with azotic gas; from which
circumstance, they have only been able to keep up the combustion of
hydrogen gas for a very limited time in close vessels, because, as the
residuum of azotic gas is continually increasing, the air becomes at
last so much contaminated, that the flame weakens and goes out. This
inconvenience is so much the greater in proportion as the oxygen gas
employed is less pure. From this circumstance, we must either be
satisfied with operating upon small quantities, or must exhaust the
vessels at intervals, to get rid of the residuum of azotic gas; but, in
this case, a portion of the water formed during the experiment is
evaporated by the exhaustion; and the resulting error is the more
dangerous to the accuracy of the process, that we have no certain means
of valuing it.
These considerations make me desirous to repeat the principal
experiments of pneumatic chemistry with oxygen gas entirely free from
any admixture of azotic gas; and this may be procured from oxygenated
muriat of potash. The oxygen gas extracted from this salt does not
appear to contain azote, unless accidentally, so that, by proper
precautions, it may be obtained perfectly pure. In the mean time, the
apparatus employed by Mr Meusnier and me for the combustion of hydrogen
gas, which is described in the experiment for recomposition of water,
Part I. Chap. VIII. and need not be here repeated, will answer the
purpose; when pure gasses are procured, this apparatus will require no
alterations, except that the capacity of the vessels may then be
diminished. See Pl. IV. Fig. 5.
The combustion, when once begun, continues for a considerable time, but
weakens gradually, in proportion as the quantity of azotic gas remaining
from the combustion increases, till at last the azotic gas is in such
over proportion that the combustion can no longer be supported, and the
flame goes out. This spontaneous extinction must be prevented, because,
as the hydrogen gas is pressed upon in its reservoir, by an inch and a
half of water, whilst the oxygen gas suffers a pressure only of three
lines, a mixture of the two would take place in the balloon, which would
at last be forced by the superior pressure into the reservoir of oxygen
gas. Wherefore the combustion must be stopped, by shutting the
stop-cock of the tube dDd whenever the flame grows very feeble; for
which purpose it must be attentively watched.
There is another apparatus for combustion, which, though we cannot with
it perform experiments with the same scrupulous exactness as with the
preceding instruments, gives very striking results that are extremely
proper to be shewn in courses of philosophical chemistry. It consists of
a worm EF, Pl. IX. Fig. 5. contained in a metallic cooller ABCD. To the
upper part of this worm E, the chimney GH is fixed, which is composed of
two tubes, the inner of which is a continuation of the worm, and the
outer one is a case of tin-plate, which surrounds it at about an inch
distance, and the interval is filled up with sand. At the inferior
extremity K of the inner tube, a glass tube is fixed, to which we adopt
the Argand lamp LM for burning alkohol, &c.
Things being thus disposed, and the lamp being filled with a determinate
quantity of alkohol, it is set on fire; the water which is formed during
the combustion rises in the chimney KE, and being condensed in the worm,
runs out at its extremity F into the bottle P. The double tube of the
chimney, filled with sand in the interstice, is to prevent the tube from
cooling in its upper part, and condensing the water; otherwise, it
would fall back in the tube, and we should not be able to ascertain its
quantity, and besides it might fall in drops upon the wick, and
extinguish the flame. The intention of this construction, is to keep the
chimney always hot, and the worm always cool, that the water may be
preserved in the state of vapour whilst rising, and may be condensed
immediately upon getting into the descending part of the apparatus. By
this instrument, which was contrived by Mr Meusnier, and which is
described by me in the Memoirs of the Academy for 1784, p. 593. we may,
with attention to keep the worm always cold, collect nearly seventeen
ounces of water from the combustion of sixteen ounces of alkohol.
SECT. VIII.
_Of the Oxydation of Metals._
The term _oxydation_ or _calcination_ is chiefly used to signify the
process by which metals exposed to a certain degree of heat are
converted into oxyds, by absorbing oxygen from the air. This combination
takes place in consequence of oxygen possessing a greater affinity to
metals, at a certain temperature, than to caloric, which becomes
disengaged in its free state; but, as this disengagement, when made in
common air, is slow and progressive, it is scarcely evident to the
senses. It is quite otherwise, however, when oxydation takes place in
oxygen gas; for, being produced with much greater rapidity, it is
generally accompanied with heat and light, so as evidently to show that
metallic substances are real combustible bodies.
All the metals have not the same degree of affinity to oxygen. Gold,
silver, and platina, for instance, are incapable of taking it away from
its combination with caloric, even in the greatest known heat; whereas
the other metals absorb it in a larger or smaller quantity, until the
affinities of the metal to oxygen, and of the latter to caloric, are in
exact equilibrium. Indeed, this state of equilibrium of affinities may
be assumed as a general law of nature in all combinations.
In all operations of this nature, the oxydation of metals is accelerated
by giving free access to the air; it is sometimes much assisted by
joining the action of a bellows, which directs a stream of air over the
surface of the metal. This process becomes greatly more rapid if a
stream of oxygen gas be used, which is readily done by means of the
gazometer formerly described. The metal, in this case, throws out a
brilliant flame, and the oxydation is very quickly accomplished; but
this method can only be used in very confined experiments, on account of
the expence of procuring oxygen gas. In the essay of ores, and in all
the common operations of the laboratory, the calcination or oxydation of
metals is usually performed in a dish of baked clay, Pl. IV. Fig. 6.
commonly called a _roasting test_, placed in a strong furnace. The
substances to be oxydated are frequently stirred, on purpose to present
fresh surfaces to the air.
Whenever this operation is performed upon a metal which is not volatile,
and from which nothing flies off into the surrounding air during the
process, the metal acquires additional weight; but the cause of this
increased weight during oxydation could never have been discovered by
means of experiments performed in free air; and it is only since these
operations have been performed in close vessels, and in determinate
quantities of air, that any just conjectures have been formed concerning
the cause of this phenomenon. The first method for this purpose is due
to Dr Priestley, who exposes the metal to be calcined in a porcelain cup
N, Pl. IV. Fig. 11. placed upon the stand IK, under a jar A, in the
bason BCDE, full of water; the water is made to rise up to GH, by
sucking out the air with a syphon, and the focus of a burning glass is
made to fall upon the metal. In a few minutes the oxydation takes
place, a part of the oxygen contained in the air combines with the
metal, and a proportional diminution of the volume of air is produced;
what remains is nothing more than azotic gas, still however mixed with a
small quantity of oxygen gas. I have given an account of a series of
experiments made with this apparatus in my Physical and Chemical Essays,
first published in 1773. Mercury may be used instead of water in this
experiment, whereby the results are rendered still more conclusive.
Another process for this purpose was invented by Mr Boyle, and of which
I gave an account in the Memoirs of the Academy for 1774, p. 351. The
metal is introduced into a retort, Pl. III. Fig. 20. the beak of which
is hermetically sealed; the metal is then oxydated by means of heat
applied with great precaution. The weight of the vessel, and its
contained substances, is not at all changed by this process, until the
extremity of the neck of the retort is broken; but, when that is done,
the external air rushes in with a hissing noise. This operation is
attended with danger, unless a part of the air is driven out of the
retort, by means of heat, before it is hermetically sealed, as otherwise
the retort would be apt to burst by the dilation of the air when placed
in the furnace. The quantity of air driven out may be received under a
jar in the pneumato-chemical apparatus, by which its quantity, and that
of the air remaining in the retort, is ascertained. I have not
multiplied my experiments upon oxydation of metals so much as I could
have wished; neither have I obtained satisfactory results with any metal
except tin. It is much to be wished that some person would undertake a
series of experiments upon oxydation of metals in the several gasses;
the subject is important, and would fully repay any trouble which this
kind of experiment might occasion.
As all the oxyds of mercury are capable of revivifying without addition,
and restore the oxygen gas they had before absorbed, this seemed to be
the most proper metal for becoming the subject of conclusive experiments
upon oxydation. I formerly endeavoured to accomplish the oxydation of
mercury in close vessels, by filling a retort, containing a small
quantity of mercury, with oxygen gas, and adapting a bladder half full
of the same gas to its beak; See Pl. IV. Fig. 12. Afterwards, by heating
the mercury in the retort for a very long time, I succeeded in oxydating
a very small portion, so as to form a little red oxyd floating upon the
surface of the running mercury; but the quantity was so small, that the
smallest error committed in the determination of the quantities of
oxygen gas before and after the operation must have thrown very great
uncertainty upon the results of the experiment. I was, besides,
dissatisfied with this process, and not without cause, lest any air
might have escaped through the pores of the bladder, more especially as
it becomes shrivelled by the heat of the furnace, unless covered over
with cloths kept constantly wet.
This experiment is performed with more certainty in the apparatus
described in the Memoirs of the Academy for 1775, p. 580. This consists
of a retort, A, Pl. IV. Fig. 2. having a crooked glass tube BCDE of ten
or twelve lines internal diameter, melted on to its beak, and which is
engaged under the bell glass FG, standing with its mouth downwards, in a
bason filled with water or mercury. The retort is placed upon the bars
of the furnace MMNN, Pl. IV. Fig. 2. or in a sand bath, and by means of
this apparatus we may, in the course of several days, oxydate a small
quantity of mercury in common air; the red oxyd floats upon the surface,
from which it may be collected and revivified, so as to compare the
quantity of oxygen gas obtained in revivification with the absorption
which took place during oxydation. This kind of experiment can only be
performed upon a small scale, so that no very certain conclusions can be
drawn from them[61].
The combustion of iron in oxygen gas being a true oxydation of that
metal, ought to be mentioned in this place. The apparatus employed by Mr
Ingenhousz for this operation is represented in Pl. IV. Fig. 17.; but,
having already described it sufficiently in Chap. III. I shall refer the
reader to what is said of it in that place. Iron may likewise be
oxydated by combustion in vessels filled with oxygen gas, in the way
already directed for phosphorus and charcoal. This apparatus is
represented Pl. IV. Fig. 3. and described in the fifth chapter of the
first part of this work. We learn from Mr Ingenhousz, that all the
metals, except gold, silver, and mercury, may be burnt or oxydated in
the same manner, by reducing them into very fine wire, or very thin
plates cut into narrow slips; these are twisted round with iron-wire,
which communicates the property of burning to the other metals.
Mercury is even difficultly oxydated in free air. In chemical
laboratories, this process is usually carried on in a matrass A, Pl. IV.
Fig. having a very flat body, and a very long neck BC, which vessel is
commonly called _Boyle's bell_. A quantity of mercury is introduced
sufficient to cover the bottom, and it is placed in a sand-bath, which
keeps up a constant heat approaching to that of boiling mercury. By
continuing this operation with five or six similar matrasses during
several months, and renewing the mercury from time to time, a few
ounces of red oxyd are at last obtained. The great slowness and
inconvenience of this apparatus arises from the air not being
sufficiently renewed; but if, on the other hand, too free a circulation
were given to the external air, it would carry off the mercury in
solution in the state of vapour, so that in a few days none would remain
in the vessel.
As, of all the experiments upon the oxydation of metals, those with
mercury are the most conclusive, it were much to be wished that a simple
apparatus could be contrived by which this oxydation and its results
might be demonstrated in public courses of chemistry. This might, in my
opinion, be accomplished by methods similar to those I have already
described for the combustion of charcoal and the oils; but, from other
pursuits, I have not been able hitherto to resume this kind of
experiment.
The oxyd of mercury revives without addition, by being heated to a
slightly red heat. In this degree of temperature, oxygen has greater
affinity to caloric than to mercury, and forms oxygen gas. This is
always mixed with a small portion of azotic gas, which indicates that
the mercury absorbs a small portion of this latter gas during oxydation.
It almost always contains a little carbonic acid gas, which must
undoubtedly be attributed to the foulnesses of the oxyd; these are
charred by the heat, and convert a part of the oxygen gas into carbonic
acid.
If chemists were reduced to the necessity of procuring all the oxygen
gas employed in their experiments from mercury oxydated by heat without
addition, or, as it is called, _calcined_ or _precipitated_ per se, the
excessive dearness of that preparation would render experiments, even
upon a moderate scale, quite impracticable. But mercury may likewise be
oxydated by means of nitric acid; and in this way we procure a red oxyd,
even more pure than that produced by calcination. I have sometimes
prepared this oxyd by dissolving mercury in nitric acid, evaporating to
dryness, and calcining the salt, either in a retort, or in capsules
formed of pieces of broken matrasses and retorts, in the manner formerly
described; but I have never succeeded in making it equally beautiful
with what is sold by the druggists, and which is, I believe, brought
from Holland. In choosing this, we ought to prefer what is in solid
lumps composed of soft adhering scales, as when in powder it is
sometimes adulterated with red oxyd of lead.
To obtain oxygen gas from the red oxyd of mercury, I usually employ a
porcelain retort, having a long glass tube adapted to its beak, which is
engaged under jars in the water pneumato-chemical apparatus, and I
place a bottle in the water, at the end of the tube, for receiving the
mercury, in proportion as it revives and distils over. As the oxygen gas
never appears till the retort becomes red, it seems to prove the
principle established by Mr Berthollet, that an obscure heat can never
form oxygen gas, and that light is one of its constituent elements. We
must reject the first portion of gas which comes over, as being mixed
with common air, from what was contained in the retort at the beginning
of the experiment; but, even with this precaution, the oxygen gas
procured is usually contaminated with a tenth part of azotic gas, and
with a very small portion of carbonic acid gas. This latter is readily
got rid of, by making the gas pass through a solution of caustic alkali;
but we know of no method for separating the azotic gas; its proportions
may however be ascertained, by leaving a known quantity of the oxygen
gas contaminated with it for a fortnight, in contact with sulphuret of
soda or potash, which absorbs the oxygen gas so as to convert the
sulphur into sulphuric acid, and leaves the azotic gas remaining pure.
We may likewise procure oxygen gas from black oxyd of manganese or
nitrat of potash, by exposing them to a red heat in the apparatus
already described for operating upon red oxyd of mercury; only, as it
requires such a heat as is at least capable of softening glass, we must
employ retorts of stone or of porcelain. But the purest and best oxygen
gas is what is disengaged from oxygenated muriat of potash by simple
heat. This operation is performed in a glass retort, and the gas
obtained is perfectly pure, provided that the first portions, which are
mixed with the common air of the vessels, be rejected.
FOOTNOTES:
[61] See an account of this experiment, Part. I. Chap. iii.--A.
CHAP. IX.
_Of Deflagration._
I have already shown, Part I. Chap. IX. that oxygen does not always part
with the whole of the caloric it contained in the state of gas when it
enters into combination with other bodies. It carries almost the whole
of its caloric alongst with it in entering into the combinations which
form nitric acid and oxygenated muriatic acid; so that in nitrats, and
more especially in oxygenated muriats, the oxygen is, in a certain
degree, in the state of oxygen gas, condensed, and reduced to the
smallest volume it is capable of occupying.
In these combinations, the caloric exerts a constant action upon the
oxygen to bring it back to the state of gas; hence the oxygen adheres
but very slightly, and the smallest additional force is capable of
setting it free; and, when such force is applied, it often recovers the
state of gas instantaneously. This rapid passage from the solid to the
aëriform state is called detonation, or fulmination, because it is
usually accompanied with noise and explosion. Deflagrations are commonly
produced by means of combinations of charcoal either with nitre or
oxygenated muriat of potash; sometimes, to assist the inflammation,
sulphur is added; and, upon the just proportion of these ingredients,
and the proper manipulation of the mixture, depends the art of making
gun-powder.
As oxygen is changed, by deflagration with charcoal, into carbonic acid,
instead of oxygen gas, carbonic acid gas is disengaged, at least when
the mixture has been made in just proportions. In deflagration with
nitre, azotic gas is likewise disengaged, because azote is one of the
constituent elements of nitric acid.
The sudden and instantaneous disengagement and expansion of these gasses
is not, however, sufficient for explaining all the phenomena of
deflagration; because, if this were the sole operating power, gun powder
would always be so much the stronger in proportion as the quantity of
gas disengaged in a given time was the more considerable, which does not
always accord with experiment. I have tried some kinds which produced
almost double the effect of ordinary gun powder, although they gave out
a sixth part less of gas during deflagration. It would appear that the
quantity of caloric disengaged at the moment of detonation contributes
considerably to the expansive effects produced; for, although caloric
penetrates freely through the pores of every body in nature, it can only
do so progressively, and in a given time; hence, when the quantity
disengaged at once is too large to get through the pores of the
surrounding bodies, it must necessarily act in the same way with
ordinary elastic fluids, and overturn every thing that opposes its
passage. This must, at least in part, take place when gun-powder is set
on fire in a cannon; as, although the metal is permeable to caloric, the
quantity disengaged at once is too large to find its way through the
pores of the metal, it must therefore make an effort to escape on every
side; and, as the resistance all around, excepting towards the muzzle,
is too great to be overcome, this effort is employed for expelling the
bullet.
The caloric produces a second effect, by means of the repulsive force
exerted between its particles; it causes the gasses, disengaged at the
moment of deflagration, to expand with a degree of force proportioned to
the temperature produced.
It is very probable that water is decomposed during the deflagration of
gun-powder, and that part of the oxygen furnished to the nascent
carbonic acid gas is produced from it. If so, a considerable quantity of
hydrogen gas must be disengaged in the instant of deflagration, which
expands, and contributes to the force of the explosion. It may readily
be conceived how greatly this circumstance must increase the effect of
powder, if we consider that a pint of hydrogen gas weighs only one
grain and two thirds; hence a very small quantity in weight must occupy
a very large space, and it must exert a prodigious expansive force in
passing from the liquid to the aëriform state of existence.
In the last place, as a portion of undecomposed water is reduced to
vapour during the deflagration of gun-powder, and as water, in the state
of gas, occupies seventeen or eighteen hundred times more space than in
its liquid state, this circumstance must likewise contribute largely to
the explosive force of the powder.
I have already made a considerable series of experiments upon the nature
of the elastic fluids disengaged during the deflagration of nitre with
charcoal and sulphur; and have made some, likewise, with the oxygenated
muriat of potash. This method of investigation leads to tollerably
accurate conclusions with respect to the constituent elements of these
salts. Some of the principal results of these experiments, and of the
consequences drawn from them respecting the analysis of nitric acid, are
reported in the collection of memoirs presented to the Academy by
foreign philosophers, vol. xi. p. 625. Since then I have procured more
convenient instruments, and I intend to repeat these experiments upon a
larger scale, by which I shall procure more accurate precision in their
results; the following, however, is the process I have hitherto
employed. I would very earnestly advise such as intend to repeat some of
these experiments, to be very much upon their guard in operating upon
any mixture which contains nitre, charcoal, and sulphur, and more
especially with those in which oxygenated muriat of potash is mixed with
these two materials.
I make use of pistol barrels, about six inches long, and of five or six
lines diameter, having the touch-hole spiked up with an iron nail
strongly driven in, and broken in the hole, and a little tin-smith's
solder run in to prevent any possible issue for the air. These are
charged with a mixture of known quantities of nitre and charcoal, or any
other mixture capable of deflagration, reduced to an impalpable powder,
and formed into a paste with a moderate quantity of water. Every portion
of the materials introduced must be rammed down with a rammer nearly of
the same caliber with the barrel, four or five lines at the muzzle must
be left empty, and about two inches of quick match are added at the end
of the charge. The only difficulty in this experiment, especially when
sulphur is contained in the mixture, is to discover the proper degree of
moistening; for, if the paste be too much wetted, it will not take fire,
and if too dry, the deflagration is apt to become too rapid, and even
dangerous.
When the experiment is not intended to be rigorously exact, we set fire
to the match, and, when it is just about to communicate with the charge,
we plunge the pistol below a large bell-glass full of water, in the
pneumato chemical apparatus. The deflagration begins, and continues in
the water, and gas is disengaged with less or more rapidity, in
proportion as the mixture is more or less dry. So long as the
deflagration continues, the muzzle of the pistol must be kept somewhat
inclined downwards, to prevent the water from getting into its barrel.
In this manner I have sometimes collected the gas produced from the
deflagration of an ounce and half, or two ounces, of nitre.
In this manner of operating it is impossible to determine the quantity
of carbonic acid gas disengaged, because a part of it is absorbed by the
water while passing through it; but, when the carbonic acid is absorbed,
the azotic gas remains; and, if it be agitated for a few minutes in
caustic alkaline solution, we obtain it pure, and can easily determine
its volume and weight. We may even, in this way, acquire a tollerably
exact knowledge of the quantity of carbonic acid by repeating the
experiment a great many times, and varying the proportions of charcoal,
till we find the exact quantity requisite to deflagrate the whole nitre
employed. Hence, by means of the weight of charcoal employed, we
determine the weight of oxygen necessary for saturation, and deduce the
quantity of oxygen contained in a given weight of nitre.
I have used another process, by which the results of this experiment are
considerably more accurate, which consists in receiving the disengaged
gasses in bell-glasses filled with mercury. The mercurial apparatus I
employ is large enough to contain jars of from twelve to fifteen pints
in capacity, which are not very readily managed when full of mercury,
and even require to be filled by a particular method. When the jar is
placed in the cistern of mercury, a glass syphon is introduced,
connected with a small air-pump, by means of which the air is exhausted,
and the mercury rises so as to fill the jar. After this, the gas of the
deflagration is made to pass into the jar in the same manner as directed
when water is employed.
I must again repeat, that this species of experiment requires to be
performed with the greatest possible precautions. I have sometimes seen,
when the disengagement of gas proceeded with too great rapidity, jars
filled with more than an hundred and fifty pounds of mercury driven off
by the force of the explosion, and broken to pieces, while the mercury
was scattered about in great quantities.
When the experiment has succeeded, and the gas is collected under the
jar, its quantity in general, and the nature and quantities of the
several species of gasses of which the mixture is composed, are
accurately ascertained by the methods already pointed out in the second
chapter of this part of my work. I have been prevented from putting the
last hand to the experiments I had begun upon deflagration, from their
connection with the objects I am at present engaged in; and I am in
hopes they will throw considerable light upon the operations belonging
to the manufacture of gun-powder.
CHAP. X.
_Of the Instruments necessary for Operating upon Bodies in very high
Temperatures._
SECT. I.
_Of Fusion._
We have already seen, that, by aqueous solution, in which the particles
of bodies are separated from each other, neither the solvent nor the
body held in solution are at all decomposed; so that, whenever the cause
of separation ceases, the particles reunite, and the saline substance
recovers precisely the same appearance and properties it possessed
before solution. Real solutions are produced by fire, or by introducing
and accumulating a great quantity of caloric between the particles of
bodies; and this species of solution in caloric is usually called
_fusion_.
This operation is commonly performed in vessels called crucibles, which
must necessarily be less fusible than the bodies they are intended to
contain. Hence, in all ages, chemists have been extremely solicitous to
procure crucibles of very refractory materials, or such as are capable
of resisting a very high degree of heat. The best are made of very pure
clay or of porcelain earth; whereas such as are made of clay mixed with
calcareous or silicious earth are very fusible. All the crucibles made
in the neighbourhood of Paris are of this kind, and consequently unfit
for most chemical experiments. The Hessian crucibles are tolerably good;
but the best are made of Limoges earth, which seems absolutely
infusible. We have, in France, a great many clays very fit for making
crucibles; such, for instance, is the kind used for making melting pots
at the glass-manufactory of St Gobin.
Crucibles are made of various forms, according to the operations they
are intended to perform. Several of the most common kinds are
represented Pl. VII. Fig. 7. 8. 9. and 10. the one represented at Fig.
9. is almost shut at its mouth.
Though fusion may often take place without changing the nature of the
fused body, this operation is frequently employed as a chemical means of
decomposing and recompounding bodies. In this way all the metals are
extracted from their ores; and, by this process, they are revivified,
moulded, and alloyed with each other. By this process sand and alkali
are combined to form glass, and by it likewise pastes, or coloured
stones, enamels, &c. are formed.
The action of violent fire was much more frequently employed by the
ancient chemists than it is in modern experiments. Since greater
precision has been employed in philosophical researches, the _humid_ has
been preferred to the _dry_ method of process, and fusion is seldom had
recourse to until all the other means of analysis have failed.
SECT. II.
_Of Furnaces._
These are instruments of most universal use in chemistry; and, as the
success of a great number of experiments depends upon their being well
or ill constructed, it is of great importance that a laboratory be well
provided in this respect. A furnace is a kind of hollow cylindrical
tower, sometimes widened above, Pl. XIII. Fig. 1. ABCD, which must have
at least two lateral openings; one in its upper part F, which is the
door of the fire-place, and one below, G, leading to the ash-hole.
Between these the furnace is divided by a horizontal grate, intended
for supporting the fewel, the situation of which is marked in the figure
by the line HI. Though this be the least complicated of all the chemical
furnaces, yet it is applicable to a great number of purposes. By it
lead, tin, bismuth, and, in general, every substance which does not
require a very strong fire, may be melted in crucibles; it will serve
for metallic oxydations, for evaporatory vessels, and for sand-baths, as
in Pl. III. Fig. 1. and 2. To render it proper for these purposes,
several notches, m m m m, Pl. XIII. Fig. 1. are made in its upper
edge, as otherwise any pan which might be placed over the fire would
stop the passage of the air, and prevent the fewel from burning. This
furnace can only produce a moderate degree of heat, because the quantity
of charcoal it is capable of consuming is limited by the quantity of air
which is allowed to pass through the opening G of the ash-hole. Its
power might be considerably augmented by enlarging this opening, but
then the great stream of air which is convenient for some operations
might be hurtful in others; wherefore we must have furnaces of different
forms, constructed for different purposes, in our laboratories: There
ought especially to be several of the kind now described of different
sizes.
The reverberatory furnace, Pl. XIII. Fig. 2. is perhaps more necessary.
This, like the common furnace, is composed of the ash-hole HIKL, the
fire-place KLMN, the laboratory MNOP, and the dome RRSS, with its funnel
or chimney TTVV; and to this last several additional tubes may be
adapted, according to the nature of the different experiments. The
retort A is placed in the division called the laboratory, and supported
by two bars of iron which run across the furnace, and its beak comes out
at a round hole in the side of the furnace, one half of which is cut in
the piece called the laboratory, and the other in the dome. In most of
the ready made reverberatory furnaces which are sold by the potters at
Paris, the openings both above and below are too small: These do not
allow a sufficient volume of air to pass through; hence, as the quantity
of charcoal consumed, or, what is much the same thing, the quantity of
caloric disengaged, is nearly in proportion to the quantity of air which
passes through the furnace, these furnaces do not produce a sufficient
effect in a great number of experiments. To remedy this defect, there
ought to be two openings GG to the ash-hole; one of these is shut up
when only a moderate fire is required; and both are kept open when the
strongest power of the furnace is to be exerted. The opening of the dome
SS ought likewise to be considerably larger than is usually made.
It is of great importance not to employ retorts of too large size in
proportion to the furnace, as a sufficient space ought always to be
allowed for the passage of the air between the sides of the furnace and
the vessel. The retort A in the figure is too small for the size of the
furnace, yet I find it more easy to point out the error than to correct
it. The intention of the dome is to oblige the flame and heat to
surround and strike back or reverberate upon every part of the retort,
whence the furnace gets the name of reverberatory. Without this
circumstance the retort would only be heated in its bottom, the vapours
raised from the contained substance would condense in the upper part,
and a continual cohabitation would take place without any thing passing
over into the receiver, but, by means of the dome, the retort is equally
heated in every part, and the vapours being forced out, can only
condense in the neck of the retort, or in the recipient.
To prevent the bottom of the retort from being either heated or coolled
too suddenly, it is sometimes placed in a small sand-bath of baked clay,
standing upon the cross bars of the furnace. Likewise, in many
operations, the retorts are coated over with lutes, some of which are
intended to preserve them from the too sudden influence of heat or of
cold, while others are for sustaining the glass, or forming a kind of
second retort, which supports the glass one during operations wherein
the strength of the fire might soften it. The former is made of
brick-clay with a little cow's hair beat up alongst with it, into a
paste or mortar, and spread over the glass or stone retorts. The latter
is made of pure clay and pounded stone-ware mixed together, and used in
the same manner. This dries and hardens by the fire, so as to form a
true supplementary retort capable of retaining the materials, if the
glass retort below should crack or soften. But, in experiments which are
intended for collecting gasses, this lute, being porous, is of no manner
of use.
In a great many experiments wherein very violent fire is not required,
the reverberatory furnace may be used as a melting one, by leaving out
the piece called the laboratory, and placing the dome immediately upon
the fire-place, as represented Pl. XIII. Fig. 3. The furnace represented
in Fig. 4. is very convenient for fusions; it is composed of the
fire-place and ash-hole ABD, without a door, and having a hole E, which
receives the muzzle of a pair of bellows strongly luted on, and the dome
ABGH, which ought to be rather lower than is represented in the figure.
This furnace is not capable of producing a very strong heat, but is
sufficient for ordinary operations, and may be readily moved to any part
of the laboratory where it is wanted. Though these particular furnaces
are very convenient, every laboratory must be provided with a forge
furnace, having a good pair of bellows, or, what is more necessary, a
powerful melting furnace. I shall describe the one I use, with the
principles upon which it is constructed.
The air circulates in a furnace in consequence of being heated in its
passage through the burning coals; it dilates, and, becoming lighter
than the surrounding air, is forced to rise upwards by the pressure of
the lateral columns of air, and is replaced by fresh air from all sides,
especially from below. This circulation of air even takes place when
coals are burnt in a common chaffing dish; but we can readily conceive,
that, in a furnace open on all sides, the mass of air which passes, all
other circumstances being equal, cannot be so great as when it is
obliged to pass through a furnace in the shape of a hollow tower, like
most of the chemical furnaces, and consequently, that the combustion
must be more rapid in a furnace of this latter construction. Suppose,
for instance, the furnace ABCDEF open above, and filled with burning
coals, the force with which the air passes through the coals will be in
proportion to the difference between the specific gravity of two columns
equal to AC, the one of cold air without, and the other of heated air
within the furnace. There must be some heated air above the opening AB,
and the superior levity of this ought likewise to be taken into
consideration; but, as this portion is continually coolled and carried
off by the external air, it cannot produce any great effect.
But, if we add to this furnace a large hollow tube GHAB of the same
diameter, which preserves the air which has been heated by the burning
coals from being coolled and dispersed by the surrounding air, the
difference of specific gravity which causes the circulation will then be
between two columns equal to GC. Hence, if GC be three times the length
of AC, the circulation will have treble force. This is upon the
supposition that the air in GHCD is as much heated as what is contained
in ABCD, which is not strictly the case, because the heat must decrease
between AB and GH; but, as the air in GHAB is much warmer than the
external air, it follows, that the addition of the tube must increase
the rapidity of the stream of air, that a larger quantity must pass
through the coals, and consequently that a greater degree of combustion
must take place.
We must not, however, conclude from these principles, that the length of
this tube ought to be indefinitely prolonged; for, since the heat of the
air gradually diminishes in passing from AB to GH, even from the contact
of the sides of the tube, if the tube were prolonged to a certain
degree, we would at last come to a point where the specific gravity of
the included air would be equal to the air without; and, in this case,
as the cool air would no longer tend to rise upwards, it would become a
gravitating mass, resisting the ascension of the air below. Besides, as
this air, which has served for combustion, is necessarily mixed with
carbonic acid gas, which is considerably heavier than common air, if the
tube were made long enough, the air might at last approach so near to
the temperature of the external air as even to gravitate downwards;
hence we must conclude, that the length of the tube added to a furnace
must have some limit beyond which it weakens, instead of strengthening
the force of the fire.
From these reflections it follows, that the first foot of tube added to
a furnace produces more effect than the sixth, and the sixth more than
the tenth; but we have no data to ascertain at what height we ought to
stop. This limit of useful addition is so much the farther in proportion
as the materials of the tube are weaker conductors of heat, because the
air will thereby be so much less coolled; hence baked earth is much to
be preferred to plate iron. It would be even of consequence to make the
tube double, and to fill the interval with rammed charcoal, which is one
of the worst conductors of heat known; by this the refrigeration of the
air will be retarded, and the rapidity of the stream of air consequently
increased; and, by this means, the tube may be made so much the longer.
As the fire-place is the hottest part of a furnace, and the part where
the air is most dilated in its passage, this part ought to be made with
a considerable widening or belly. This is the more necessary, as it is
intended to contain the charcoal and crucible, as well as for the
passage of the air which supports, or rather produces the combustion;
hence we only allow the interstices between the coals for the passage of
the air.
From these principles my melting furnace is constructed, which I believe
is at least equal in power to any hitherto made, though I by no means
pretend that it possesses the greatest possible intensity that can be
produced in chemical furnaces. The augmentation of the volume of air
produced during its passage through a melting furnace not being hitherto
ascertained from experiment, we are still unacquainted with the
proportions which should exist between the inferior and superior
apertures, and the absolute size of which these openings should be made
is still less understood; hence data are wanting by which to proceed
upon principle, and we can only accomplish the end in view by repeated
trials.
This furnace, which, according to the above stated rules, is in form of
an eliptical spheroid, is represented Pl. XIII. Fig. 6. ABCD; it is cut
off at the two ends by two plains, which pass, perpendicular to the
axis, through the foci of the elipse. From this shape it is capable of
containing a considerable quantity of charcoal, while it leaves
sufficient space in the intervals for the passage of the air. That no
obstacle may oppose the free access of external air, it is perfectly
open below, after the model of Mr Macquer's melting furnace, and stands
upon an iron tripod. The grate is made of flat bars set on edge, and
with considerable interstices. To the upper part is added a chimney, or
tube, of baked earth, ABFG, about eighteen feet long, and almost half
the diameter of the furnace. Though this furnace produces a greater heat
than any hitherto employed by chemists, it is still susceptible of being
considerably increased in power by the means already mentioned, the
principal of which is to render the tube as bad a conductor of heat as
possible, by making it double, and filling the interval with rammed
charcoal.
When it is required to know if lead contains any mixture of gold or
silver, it is heated in a strong fire in capsules of calcined bones,
which are called cuppels. The lead is oxydated, becomes vitrified, and
sinks into the substance of the cuppel, while the gold or silver, being
incapable of oxydation, remain pure. As lead will not oxydate without
free access of air, this operation cannot be performed in a crucible
placed in the middle of the burning coals of a furnace, because the
internal air, being mostly already reduced by the combustion into azotic
and carbonic acid gas, is no longer fit for the oxydation of metals. It
was therefore necessary to contrive a particular apparatus, in which the
metal should be at the same time exposed to the influence of violent
heat, and defended from contact with air rendered incombustible by its
passage through burning coals. The furnace intended for answering this
double purpose is called the cuppelling or essay furnace. It is usually
made of a square form, as represented Pl. XIII. Fig. 8. and 10. having
an ash-hole AABB, a fire-place BBCC, a laboratory CCDD, and a dome DDEE.
The muffle or small oven of baked earth GH, Fig. 9. being placed in the
laboratory of the furnace upon cross bars of iron, is adjusted to the
opening GG, and luted with clay softened in water. The cuppels are
placed in this oven or muffle, and charcoal is conveyed into the furnace
through the openings of the dome and fire-place. The external air enters
through the openings of the ash-hole for supporting the combustion, and
escapes by the superior opening or chimney at EE; and air is admitted
through the door of the muffle GG for oxydating the contained metal.
Very little reflection is sufficient to discover the erroneous
principles upon which this furnace is constructed. When the opening GG
is shut, the oxydation is produced slowly, and with difficulty, for want
of air to carry it on; and, when this hole is open, the stream of cold
air which is then admitted fixes the metal, and obstructs the process.
These inconveniencies may be easily remedied, by constructing the muffle
and furnace in such a manner that a stream of fresh external air should
always play upon the surface of the metal, and this air should be made
to pass through a pipe of clay kept continually red hot by the fire of
the furnace. By this means the inside of the muffle will never be
coolled, and processes will be finished in a few minutes, which at
present require a considerable space of time.
Mr Sage remedies these inconveniencies in a different manner; he places
the cuppel containing lead, alloyed with gold or silver, amongst the
charcoal of an ordinary furnace, and covered by a small porcelain
muffle; when the whole is sufficiently heated, he directs the blast of a
common pair of hand-bellows upon the surface of the metal, and completes
the cuppellation in this way with great ease and exactness.
SECT. III.
_Of increasing the Action of Fire, by using Oxygen Gas instead of
Atmospheric Air._
By means of large burning glasses, such as those of Tchirnausen and Mr
de Trudaine, a degree of heat is obtained somewhat greater than has
hitherto been produced in chemical furnaces, or even in the ovens of
furnaces used for baking hard porcelain. But these instruments are
extremely expensive, and do not even produce heat sufficient to melt
crude platina; so that their advantages are by no means sufficient to
compensate for the difficulty of procuring, and even of using them.
Concave mirrors produce somewhat more effect than burning glasses of the
same diameter, as is proved by the experiments of Messrs Macquer and
Beaumé with the speculum of the Abbé Bouriot; but, as the direction of
the reflected rays is necessarily from below upwards, the substance to
be operated upon must be placed in the air without any support, which
renders most chemical experiments impossible to be performed with this
instrument.
For these reasons, I first endeavoured to employ oxygen gas for
combustion, by filling large bladders with it, and making it pass
through a tube capable of being shut by a stop-cock; and in this way I
succeeded in causing it to support the combustion of lighted charcoal.
The intensity of the heat produced, even in my first attempt, was so
great as readily to melt a small quantity of crude platina. To the
success of this attempt is owing the idea of the gazometer, described p.
308. _et seq._ which I substituted instead of the bladders; and, as we
can give the oxygen gas any necessary degree of pressure, we can with
this instrument keep up a continued stream, and give it even a very
considerable force.
The only apparatus necessary for experiments of this kind consists of a
small table ABCD, Pl. XII. Fig. 15, with a hole F, through which passes
a tube of copper or silver, ending in a very small opening at G, and
capable of being opened or shut by the stop-cock H. This tube is
continued below the table at l m n o, and is connected with the
interior cavity of the gazometer. When we mean to operate, a hole of a
few lines deep must be made with a chizel in a piece of charcoal, into
which the substance to be treated is laid; the charcoal is set on fire
by means of a candle and blow-pipe, after which it is exposed to a
rapid stream of oxygen gas from the extremity G of the tube FG.
This manner of operating can only be used with such bodies as can be
placed, without inconvenience, in contact with charcoal, such as metals,
simple earths, &c. But, for bodies whose elements have affinity to
charcoal, and which are consequently decomposed by that substance, such
as sulphats, phosphats, and most of the neutral salts, metallic glasses,
enamels, &c. we must use a lamp, and make the stream of oxygen gas pass
through its flame. For this purpose, we use the elbowed blow-pipe ST,
instead of the bent one FG, employed with charcoal. The heat produced in
this second manner is by no means so intense as in the former way, and
is very difficultly made to melt platina. In this manner of operating
with the lamp, the substances are placed in cuppels of calcined bones,
or little cups of porcelain, or even in metallic dishes. If these last
are sufficiently large, they do not melt, because, metals being good
conductors of heat, the caloric spreads rapidly through the whole mass,
so that none of its parts are very much heated.
In the Memoirs of the Academy for 1782, p. 476. and for 1783, p. 573.
the series of experiments I have made with this apparatus may be seen at
large. The following are some of the principal results.
1. Rock cristal, or pure silicious earth, is infusible, but becomes
capable of being softened or fused when mixed with other substances.
2. Lime, magnesia, and barytes, are infusible, either when alone, or
when combined together; but, especially lime, they assist the fusion of
every other body.
3. Argill, or pure base of alum, is completely fusible _per se_ into a
very hard opake vitreous substance, which scratches glass like the
precious stones.
4. All the compound earths and stones are readily fused into a brownish
glass.
5. All the saline substances, even fixed alkali, are volatilized in a
few seconds.
6. Gold, silver, and probably platina, are slowly volatilized without
any particular phenomenon.
7. All other metallic substances, except mercury, become oxydated,
though placed upon charcoal, and burn with different coloured flames,
and at last dissipate altogether.
8. The metallic oxyds likewise all burn with flames. This seems to form
a distinctive character for these substances, and even leads me to
believe, as was suspected by Bergman, that barytes is a metallic oxyd,
though we have not hitherto been able to obtain the metal in its pure or
reguline state.
9. Some of the precious stones, as rubies, are capable of being softened
and soldered together, without injuring their colour, or even
diminishing their weights. The hyacinth, tho' almost equally fixed with
the ruby, loses its colour very readily. The Saxon and Brasilian topaz,
and the Brasilian ruby, lose their colour very quickly, and lose about a
fifth of their weight, leaving a white earth, resembling white quartz,
or unglazed china. The emerald, chrysolite, and garnet, are almost
instantly melted into an opake and coloured glass.
10. The diamond presents a property peculiar to itself; it burns in the
same manner with combustible bodies, and is entirely dissipated.
There is yet another manner of employing oxygen gas for considerably
increasing the force of fire, by using it to blow a furnace. Mr Achard
first conceived this idea; but the process he employed, by which he
thought to dephlogisticate, as it is called, atmospheric air, or to
deprive it of azotic gas, is absolutely unsatisfactory. I propose to
construct a very simple furnace, for this purpose, of very refractory
earth, similar to the one represented Pl. XIII. Fig. 4. but smaller in
all its dimensions. It is to have two openings, as at E, through one of
which the nozle of a pair of bellows is to pass, by which the heat is to
be raised as high as possible with common air; after which, the stream
of common air from the bellows being suddenly stopt, oxygen gas is to be
admitted by a tube, at the other opening, communicating with a gazometer
having the pressure of four or five inches of water. I can in this
manner unite the oxygen gas from several gazometers, so as to make eight
or nine cubical feet of gas pass through the furnace; and in this way I
expect to produce a heat greatly more intense than any hitherto known.
The upper orifice of the furnace must be carefully made of considerable
dimensions, that the caloric produced may have free issue, lest the too
sudden expansion of that highly elastic fluid should produce a dangerous
explosion.
FINIS.
APPENDIX.
No. I.
TABLE _for Converting Lines, or Twelfth Parts of an Inch, and Fractions
of Lines, into Decimal Fractions of the Inch._
Twelfth Parts Decimal Decimal
of a Line. Fractions. Lines. Fractions.
1 0.00694 1 0.08333
2 0.01389 2 0.16667
3 0.02083 3 0.25000
4 0.02778 4 0.33333
5 0.03472 5 0.41667
6 0.04167 6 0.50000
7 0.04861 7 0.58333
8 0.05556 8 0.66667
9 0.06250 9 0.75000
10 0.06944 10 0.83333
11 0.07639 11 0.91667
12 0.08333 12 1.00000
No. II.
TABLE _for Converting the Observed Heighths of Water in the Jars of the
Pneumato-Chemical Apparatus, expressed in Inches and Decimals, into
Corresponding Heighths of Mercury._
Water. Mercury. Water. Mercury.
.1 .00737 4. .29480
.2 .01474 5. .36851
.3 .02201 6. .44221
.4 .02948 7. .51591
.5 .03685 8. .58961
.6 .04422 9. .66332
.7 .05159 10. .73702
.8 .05896 11. .81072
.9 .06633 12. .88442
1. .07370 13. .96812
2. .14740 14. 1.04182
3. .22010 15. 1.11525
No. III.
TABLE _for Converting the Ounce Measures used by Dr Priestly into French
and English Cubical Inches._
Ounce French cubical English cubical
measures. inches. inches.
1 1.567 1.898
2 3.134 3.796
3 4.701 5.694
4 6.268 7.592
5 7.835 9.490
6 9.402 11.388
7 10.969 13.286
8 12.536 15.184
9 14.103 17.082
10 15.670 18.980
20 31.340 37.960
30 47.010 56.940
40 62.680 75.920
50 78.350 94.900
60 94.020 113.880
70 109.690 132.860
80 125.360 151.840
90 141.030 170.820
100 156.700 189.800
1000 1567.000 1898.000
No. IV. ADDITIONAL.
TABLE _for Reducing the Degrees of Reaumeur's Thermometer into its
corresponding Degrees of Fahrenheit's Scale._
R. F. R. F. R. F. R. F.
0 = 32 21 = 79.25 41 = 124.25 61 = 169.25
1 = 34.25 22 = 81.5 42 = 126.5 62 = 171.5
2 = 36.5 23 = 83.75 43 = 128.75 63 = 173.75
3 = 38.75 24 = 86 44 = 131 64 = 176.
4 = 41 25 = 88.25 45 = 133.25 65 = 178.25
5 = 43.25 26 = 90.5 46 = 135.5 66 = 180.5
6 = 45.5 27 = 92.75 47 = 137.75 67 = 182.75
7 = 47.75 28 = 95 48 = 140 68 = 185
8 = 50 29 = 97.25 49 = 142.25 69 = 187.25
9 = 52.25 30 = 99.5 50 = 144.5 70 = 189.5
10 = 54.5 31 = 101.75 51 = 146.75 71 = 191.75
11 = 56.75 32 = 104 52 = 149 72 = 194.
12 = 59 33 = 106.25 53 = 151.25 73 = 196.25
13 = 61.25 34 = 108.5 54 = 153.5 74 = 198.5
14 = 63.5 35 = 110.75 55 = 155.75 75 = 200.75
15 = 65.75 36 = 113 56 = 158 76 = 203
16 = 68 37 = 115.25 57 = 160.25 77 = 205.25
17 = 70.25 38 = 117.5 58 = 162.5 78 = 207.5
18 = 72.5 39 = 119.75 59 = 164.75 79 = 209.75
19 = 74.75 40 = 122 60 = 167 80 = 212
20 = 77
_Note_--Any degree, either higher or lower, than what is contained in
the above Table, may be at any time converted, by remembering that one
degree of Reaumeur's scale is equal to 2.25° of Fahrenheit; or it may be
done without the Table by the following formula, R × 9 / 4 + 32 = F;
that is, multiply the degree of Reaumeur by 9, divide the product by 4,
to the quotient add 32, and the sum is the degree of Fahrenheit.--E.
No. V. ADDITIONAL.
RULES _for converting French Weights and Measures into correspondent
English Denominations[62]._
§ 1. _Weights._
The Paris pound, poids de mark of Charlemagne, contains 9216 Paris
grains; it is divided into 16 ounces, each ounce into 8 gros, and each
gros into 72 grains. It is equal to 7561 English Troy grains.
The English Troy pound of 12 ounces contains 5760 English Troy grains,
and is equal to 7021 Paris grains.
The English averdupois pound of 16 ounces contains 7000 English Troy
grains, and is equal to 8538 Paris grains.
To reduce Paris grs. to English Troy }
grs. divide by } 1.2189
To reduce English Troy grs. to Paris }
grs. multiply by }
To reduce Paris ounces to English }
Troy, divide by }
To reduce English Troy ounces to } 1.015734
Paris, multiply by }
Or the conversion may be made by means of the following Tables.
I. _To reduce French to English Troy Weight._
The Paris pound = 7561 }
The ounce = 472.5625 } English.
The gros = 59.0703 } Troy.
The grain = .8194 } Grains.
II. _To Reduce English Troy to Paris Weight._
The English Troy pound } = 7021. }
of 12 ounces } }
The Troy ounce = 585.0830 }
The dram of 60 grs. = 73.1353 } Paris
The penny weight, or } = 29.2540 } grains.
denier, of 24 grs. } }
The scruple, of 20 grs. = 24.3784 }
III. _To Reduce English Averdupois to Paris Weight._
The averdupois pound of } }
16 ounces, or 7000 } = 8538. } Paris
Troy grains. } } grains.
The ounce = 533.6250 }
§ 2. _Long and Cubical Measures._
To reduce Paris feet or inches into }
English, multiply by } 1.065977
English feet or inches into Paris, }
divide by }
To reduce Paris cubic feet or inches }
to English, multiply by }
English cubic feet or inches to Paris, } 1.211278
divide by }
Or by means of the following tables:
IV. _To Reduce Paris Long Measure to English._
The Paris royal foot of } }
12 inches } = 12.7977 } English
The inch = 1.0659 }
The line, or 1/12 of an inch = .0888 } inches.
The 1/12 of a line = .0074 }
V. _To Reduce English Long Measure to French._
The English foot = 11.2596 }
The inch = .9383 }
The 1/8 of an inch = .1173 } Paris inches.
The 1/10 = .0938 }
The line, or 1/12 = .0782 }
VI. _To Reduce French Cube Measure to English._
The Paris } English { }
cube foot = 1.211278 } cubical { 2093.088384 }
The cubic } feet, { } inches.
inch = .000700 } or { 1.211278 }
VII. _To Reduce English Cube Measure to French._
The English cube foot, }
or 1728 cubical inches } = 1427.4864 } French
The cubical inch = .8260 } cubical
The cube tenth = .0008 } inches.
§ 3. _Measure of Capacity._
The Paris pint contains 58.145[63] English cubical inches, and the
English wine pint contains 28.85 cubical inches; or, the Paris pint
contains 2.01508 English pints, and the English pint contains .49617
Paris pints; hence,
To reduce the Paris pint to the English, }
multiply by } 2.01508.
To reduce the English pint to the }
Paris, divide by }
No. VI.
TABLE _of the Weights of the different Gasses, at 28 French inches, or
29.84 English inches barometrical pressure, and at 10° (54.5°) of
temperature, expressed in English measure and English Troy weight._
Names of the Gasses. Weight of a Weight of a
cubical inch. cubical foot.
(A) qrs. oz. dr. qrs.
Atmospheric air .32112 1 1 15
Azotic gas .30064 1 0 39.5
Oxygen gas .34211 1 1 51
Hydrogen gas .02394 0 0 41.26
Carbonic acid gas .44108 1 4 41
(B)
Nitrous gas .37000 1 2 39
Ammoniacal gas .18515 0 5 19.73
Sulphurous acid gas .71580 2 4 38
[Note A: These five were ascertained by Mr Lavoisier himself.--E.]
[Note B: The last three are inserted by Mr Lavoisier upon the authority
of Mr Kirwan.--E.]
No. VII.
_Tables_ _of the Specific Gravities of different bodies._
§ 1. _Metallic Substances._
GOLD.
Pure gold of 24 carats melted but not hammered 19.2581
The same hammered 19.3617
Gold of the Parisian standard, 22 carats fine, not hammered(A) 17.4863
The same hammered 17.5894
Gold of the standard of French coin, 21-22/32 carats fine,
not hammered 17.4022
The same coined 17.6474
Gold of the French trinket standard, 20 carats fine,
not hammered 15.7090
The same hammered 15.7746
[Note A: The same with Sterling.]
SILVER.
Pure or virgin silver, 24 deniers, not hammered 10.4743
The same hammered 10.5107
Silver of the Paris standard, 11 deniers 10 grains fine,
not hammered(B) 10.1752
The same hammered 10.3765
Silver, standard of French coin, 10 deniers 21 grains
fine, not hammered 10.0476
The same coined 10.4077
[Note B: This is 10 grs. finer than Sterling.]
PLATINA.
Crude platina in grains 15.6017
The same, after being treated with muriatic acid 16.7521
Purified platina, not hammered 19.5000
The same hammered 20.3366
The same drawn into wire 21.0417
The same passed through rollers 22.0690
COPPER AND BRASS.
Copper, not hammered 7.7880
The same wire drawn 8.8785
Brass, not hammered 8.3958
The same wire drawn 8.5441
IRON AND STEEL.
Cast iron 7.2070
Bar iron, either screwed or not 7.7880
Steel neither tempered nor screwed 7.8331
Steel screwed but not tempered 7.8404
Steel tempered and screwed 7.8180
Steel tempered and not screwed 7.8163
TIN.
Pure tin from Cornwall melted and not screwed 7.2914
The same screwed 7.2994
Malacca tin, not screwed 7.2963
The same screwed 7.3065
Molten lead 11.3523
Molten zinc 7.1908
Molten bismuth 9.8227
Molten cobalt 7.8119
Molten arsenic 5.7633
Molten nickel 7.8070
Molten antimony 6.7021
Crude antimony 4.0643
Glass of antimony 4.9464
Molybdena 4.7385
Tungstein 6.0665
Mercury 13.5681
§ 2. _Precious Stones._
White Oriental diamond 3.5212
Rose-coloured Oriental ditto 3.5310
Oriental ruby 4.2833
Spinell ditto 3.7600
Ballas ditto 3.6458
Brasillian ditto 3.5311
Oriental topas 4.0106
Ditto Pistachio ditto 4.0615
Brasillian ditto 3.5365
Saxon topas 3.5640
Ditto white ditto 3.5535
Oriental saphir 3.9941
Ditto white ditto 3.9911
Saphir of Puy 4.0769
Ditto of Brasil 3.1307
Girasol 4.0000
Ceylon jargon 4.4161
Hyacinth 3.6873
Vermillion 4.2299
Bohemian garnet 4.1888
Dodecahedral ditto 4.0627
Syrian ditto 4.0000
Volcanic ditto, with 24 sides 2.4684
Peruvian emerald 2.7755
Crysolite of the jewellers 2.7821
Ditto of Brasil 2.6923
Beryl, or Oriental aqua marine 3.5489
Occidental aqua marine 2.7227
§ 3. _Silicious Stones._
Pure rock cristal of Madagascar 2.6530
Ditto of Brasil 2.6526
Ditto of Europe, or gelatinous 2.6548
Cristallized quartz 2.6546
Amorphous ditto 2.6471
Oriental agate 2.5901
Agate onyx 2.6375
Transparent calcedony 2.6640
Carnelian 2.6137
Sardonyx 2.6025
Prase 2.5805
Onyx pebble 2.6644
Pebble of Rennes 2.6538
White jade 2.9502
Green jade 2.9660
Red jasper 2.6612
Brown ditto 2.6911
Yellow ditto 2.7101
Violet ditto 2.7111
Gray ditto 2.7640
Jasponyx 2.8160
Black prismatic hexahedral schorl 3.3852
Black spary ditto 3.3852
Black amorphous schorl, called antique basaltes 2.9225
Paving stone 2.4158
Grind stone 2.1429
Cutler's stone 2.1113
Fountainbleau stone 2.5616
Scyth stone of Auvergne 2.5638
Ditto of Lorrain 2.5298
Mill stone 2.4835
White flint 2.5941
Blackish ditto 2.5817
§ 4. _Various Stones, &c._
Opake green Italian serpentine, or gabro of the Florentines 2.4295
Coarse Briancon chalk 2.7274
Spanish chalk 2.7902
Foliated lapis ollaris of Dauphiny 2.7687
Ditto ditto from Sweden 2.8531
Muscovy talc 2.7917
Black mica 2.9004
Common schistus or slate 2.6718
New slate 2.8535
White rasor hone 2.8763
Black and white hone 3.1311
Rhombic or Iceland cristal 2.7151
Pyramidal calcareous spar 2.7141
Oriental or white antique alabaster 2.7302
Green Campan marble 2.7417
Red Campan marble 2.7242
White Carara marble 2.7168
White Parian marble 2.8376
Various kinds of calcareous stones } from 1.3864
used in France for building. } to 2.3902
Heavy spar 4.4300
White fluor 3.1555
Red ditto 3.1911
Green ditto 3.1817
Blue ditto 3.1688
Violet ditto 3.1757
Red scintilant zeolite from Edelfors 2.4868
White scintilant zeolite 2.0739
Cristallized zeolite 2.0833
Black pitch stone 2.0499
Yellow pitch stone 2.0860
Red ditto 2.6695
Blackish ditto 2.3191
Red porphyry 2.7651
Ditto of Dauphiny 2.7033
Green serpentine 2.8960
Black ditto of Dauphiny, called variolite 2.9339
Green ditto from Dauphiny 2.9883
Ophites 2.9722
Granitello 3.0626
Red Egyptian granite 2.6541
Beautiful red granite 2.7609
Granite of Girardmas 2.7163
Pumice stone .9145
Lapis obsidianus 2.3480
Pierre de Volvic 2.3205
Touch stone 2.4153
Basaltes from Giants Causeway 2.8642
Ditto prismatic from Auvergne 2.4153
Glass gall 2.8548
Bottle glass 2.7325
Green glass 2.6423
White glass 2.8922
St Gobin cristal 2.4882
Flint glass 3.3293
Borax glass 2.6070
Seves porcelain 2.1457
Limoges ditto 2.3410
China ditto 2.3847
Native sulphur 2.0332
Melted sulphur 1.9907
Hard peat 1.3290
Ambergrease .9263
Yellow transparent amber 1.0780
§ 5. _Liquids._
Distilled water 1.0000
Rain water 1.0000
Filtered water of the Seine 1.00015
Arcueil water 1.00046
Avray water 1.00043
Sea water 1.0263
Water of the Dead Sea 1.2403
Burgundy wine .9915
Bourdeaux ditto .9939
Malmsey Madeira 1.0382
Red beer 1.0338
White ditto 1.0231
Cyder 1.0181
Highly rectified alkohol .8293
Common spirits of wine .8371
Alkohol 15 pts. water 1 part. .8527
14 2 .8674
13 3 .8815
12 4 .8947
11 5 .9075
10 6 .9199
9 7 .9317
8 8 .9427
7 9 .9519
6 10 .9594
5 11 .9674
4 12 .9733
3 13 .9791
2 14 .9852
1 15 .9919
Sulphuric ether .7394
Nitric ether .9088
Muriatic ether .7298
Acetic ether .8664
Sulphuric acid 1.8409
Nitric ditto 1.2715
Muriatic ditto 1.1940
Red acetous ditto 1.0251
White acetous ditto 1.0135
Distilled ditto ditto 1.0095
Acetic ditto 1.0626
Formic ditto .9942
Solution of caustic ammoniac, or volatil alkali fluor .8970
Essential or volatile oil of turpentine .8697
Liquid turpentine .9910
Volatile oil of lavender .8938
Volatile oil of cloves 1.0363
Volatile oil of cinnamon 1.0439
Oil of olives .9153
Oil of sweet almonds .9170
Lintseed oil .9403
Oil of poppy seed .9288
Oil of beech mast .9176
Whale oil .9233
Womans milk 1.0203
Mares milk 1.0346
Ass milk 1.0355
Goats milk 1.0341
Ewe milk 1.0409
Cows milk 1.0324
Cow whey 1.0193
Human urine 1.0106
§ 6. _Resins and Gums_
Common yellow or white rosin 1.0727
Arcanson 1.0857
Galipot(A) 1.0819
Baras(A) 1.0441
Sandarac 1.0920
Mastic 1.0742
Storax 1.1098
Opake copal 1.1398
Transparent ditto 1.0452
Madagascar ditto 1.0600
Chinese ditto 1.0628
Elemi 1.0182
Oriental anime 1.0284
Occidental ditto 1.0426
Labdanum 1.1862
Ditto _in tortis_ 2.4933
Resin of guaiac 1.2289
Ditto of jallap 1.2185
Dragons blood 1.2045
Gum lac 1.1390
Tacamahaca 1.0463
Benzoin 1.0924
Alouchi(B) 1.0604
Caragna(C) 1.1244
Elastic gum .9335
Camphor .9887
Gum ammoniac 1.2071
Sagapenum 1.2008
Ivy gum(D) 1.2948
Gamboge 1.2216
Euphorbium 1.1244
Olibanum 1.1732
Myrrh 1.3600
Bdellium 1.3717
Aleppo Scamony 1.2354
Smyrna ditto 1.2743
Galbanum 1.2120
Assafoetida 1.3275
Sarcocolla 1.2684
Opoponax 1.6226
Cherry tree gum 1.4817
Gum Arabic 1.4523
Tragacanth 1.3161
Basora gum 1.4346
Acajou gum(E) 1.4456
Monbain gum(F) 1.4206
Inspissated juice of liquorice 1.7228
---- Acacia 1.5153
---- Areca 1.4573
Terra Japonica 1.3980
Hepatic aloes 1.3586
Socotrine aloes 1.3795
Inspissated juice of St John's wort 1.5263
Opium 1.3366
Indigo .7690
Arnotto .5956
Yellow wax .9648
White ditto .9686
Ouarouchi ditto(G) .8970
Cacao butter .8916
Spermaceti .9433
Beef fat .9232
Veal fat .9342
Mutton fat .9235
Tallow .9419
Hoggs fat .9368
Lard .9478
Butter .9423
[Note A: Resinous juices extracted in France from the Pine. _Vide
Bomare's Dict._]
[Note B: Odoriferous gum from the tree which produces the Cortex
Winteranus. _Bomare._]
[Note C: Resin of the tree called in Mexico Caragna, or Tree of Madness.
_Ibid._]
[Note D: Extracted in Persia and the warm countries from Hedera
terrestris.--_Bomare._]
[Note E: From a Brasilian tree of this name.--_Ibid._]
[Note F: From a tree of this name.--_Ibid._]
[Note G: The produce of the Tallow Tree of Guayana. _Vide Bomare's
Dict._]
§ 7. _Woods._
Heart of oak 60 years old 1.1700
Cork .2400
Elm trunk .6710
Ash ditto .8450
Beech .8520
Alder .8000
Maple .7550
Walnut .6710
Willow .5850
Linden .6040
Male fir .5500
Female ditto .4980
Poplar .3830
White Spanish ditto .5294
Apple tree .7930
Pear tree .6610
Quince tree .7050
Medlar .9440
Plumb tree .7850
Olive wood .9270
Cherry tree .7150
Filbert tree .6000
French box .9120
Dutch ditto 1.3280
Dutch yew .7880
Spanish ditto .8070
Spanish cypress .6440
American cedar .5608
Pomgranate tree 1.3540
Spanish mulberry tree .8970
Lignum vitae 1.3330
Orange tree .7050
_Note_--The numbers in the above Table, if the Decimal point be carried
three figures farther to the right hand, nearly express the absolute
weight of an English cube foot of each substance in averdupois ounces.
See No. VIII. of the Appendix.--E.
No. VIII. ADDITIONAL.
RULES _for Calculating the Absolute Gravity in English Troy Weight of a
Cubic Foot and Inch, English Measure, of any Substance whose Specific
Gravity is known[64]._
In 1696, Mr Everard, balance-maker to the Exchequer, weighed before the
Commissioners of the House of Commons 2145.6 cubical inches, by the
Exchequer standard foot, of distilled water, at the temperature of 55°
of Fahrenheit, and found it to weigh 1131 oz. 14 dts. Troy, of the
Exchequer standard. The beam turned with 6 grs. when loaded with 30
pounds in each scale. Hence, supposing the pound averdupois to weigh
7000 grs. Troy, a cubic foot of water weighs 62-1/2 pounds averdupois,
or 1000 ounces averdupois, wanting 106 grains Troy. And hence, if the
specific gravity of water be called 1000, the proportional specific
gravities of all other bodies will nearly express the number of
averdupois ounces in a cubic foot. Or more accurately, supposing the
specific gravity of water expressed by 1. and of all other bodies in
proportional numbers, as the cubic foot of water weighs, at the above
temperature, exactly 437489.4 grains Troy, and the cubic inch of water
253.175 grains, the absolute weight of a cubical foot or inch of any
body in Troy grains may be found by multiplying their specific gravity
by either of the above numbers respectively.
By Everard's experiment, and the proportions of the English and French
foot, as established by the Royal Society and French Academy of
Sciences, the following numbers are ascertained.
Paris grains in a Paris cube foot of water = 645511
English grains in a Paris cube foot of water = 529922
Paris grains in an English cube foot of water = 533247
English grains in an English cube foot of water = 437489.4
English grains in an English cube inch of water = 253.175
By an experiment of Picard with the measure and
weight of the Chatelet, the Paris cube foot of
water contains of Paris grains = 641326
By one of Du Hamel, made with great care = 641376
By Homberg = 641666
These show some uncertainty in measures or in weights; but the above
computation from Everard's experiment may be relied on, because the
comparison of the foot of England with that of France was made by the
joint labours of the Royal Society of London and the French Academy of
Sciences: It agrees likewise very nearly with the weight assigned by Mr
Lavoisier, 70 Paris pounds to the cubical foot of water.
No. IX.
TABLES _for Converting Ounces, Drams, and Grains, Troy, into Decimals of
the Troy Pound of 12 Ounces, and for Converting Decimals of the Pound
Troy into Ounces, &c._
I. _For Grains._
Grains = Pound.
1 .0001736
2 .0003472
3 .0005208
4 .0006944
5 .0008681
6 .0010417
7 .0012153
8 .0013889
9 .0015625
10 .0017361
20 .0034722
30 .0052083
40 .0069444
50 .0086806
60 .0104167
70 .0121528
80 .0138889
90 .0156250
100 .0173611
200 .0374222
300 .0520833
400 .0694444
500 .0868055
600 .1041666
700 .1215277
800 .1388888
900 .1562499
1000 .1736110
2000 .3472220
3000 .5208330
4000 .6944440
5000 .8680550
6000 1.0418660
7000 1.2152770
8000 1.3888880
9000 1.5624990
II. _For Drams._
Drams = Pound.
1 .0104167
2 .0208333
3 .0312500
4 .0416667
5 .0520833
6 .0625000
7 .0729167
8 .0833333
III. _For Ounces._
Ounces = Pounds.
1 .0833333
2 .1666667
3 .2500000
4 .3333333
5 .4166667
6 .5000000
7 .5833333
8 .6666667
9 .7500000
10 .8333333
11 .9166667
12 1.0000000
IV. _Decimals of the Pound into Ounces, &c._
_Tenth parts._
lib. = oz. dr. gr.
0.1 1 1 36
0.2 2 3 12
0.3 3 4 48
0.4 4 6 24
0.5 6 0 0
0.6 7 1 36
0.7 8 3 12
0.8 9 4 48
0.9 10 6 24
_Hundredth parts._
0.01 0 0 57.6
0.02 0 1 55.2
0.03 0 2 52.8
0.04 0 3 50.4
0.05 0 4 48.0
0.06 0 5 45.6
0.07 0 6 43.2
0.08 0 7 40.8
0.09 0 3 38.4
_Thousandths._
0.001 0 0 5.76
0.002 0 0 11.52
0.003 0 0 17.28
0.004 0 0 23.04
0.005 0 0 28.80
lib. = grs.
0.006 34.56
0.007 40.32
0.008 46.08
0.009 51.84
_Ten thousandth parts._
0.0001 0.576
0.0002 1.152
0.0003 1.728
0.0004 2.304
0.0005 2.880
0.0006 3.456
0.0007 4.032
0.0008 4.608
0.0009 5.184
_Hundred thousandth parts._
0.00001 0.052
0.00002 0.115
0.00003 0.173
0.00004 0.230
0.00005 0.288
0.00006 0.346
0.00007 0.403
0.00008 0.461
0.00009 0.518
No. X.
TABLE _of the English Cubical Inches and Decimals corresponding to a
determinate Troy Weight of Distilled Water at the Temperature of 55°,
calculated from Everard's experiment._
_For Grains._
Grs. Cubical inches.
1 = .0039
2 .0078
3 .0118
4 .0157
5 .0197
6 .0236
7 .0275
8 .0315
9 .0354
10 .0394
20 .0788
30 .1182
40 .1577
50 .1971
_For Drams._
Drams. Cubical inches.
1 = .2365
2 .4731
3 .7094
4 .9463
5 1.1829
6 1.4195
7 1.6561
_For Ounces._
Oz. Cubical inches.
1 = 1.8927
2 3.7855
3 5.6782
4 7.5710
5 9.4631
6 11.3565
7 13.2493
8 15.1420
9 17.0748
10 18.9276
11 20.8204
_For Pounds._
Libs. Cubical inches.
1 = 22.7131
2 45.4263
3 68.1394
4 90.8525
5 113.5657
6 136.2788
7 158.9919
8 181.7051
9 204.4183
10 227.1314
50 1135.6574
100 2271.3148
1000 22713.1488
FOOTNOTES:
[62] For the materials of this Article the Translator is indebted to
Professor Robertson.
[63] It is said, _Belidor Archit. Hydrog._ to contain 31 oz. 64 grs.
of water, which makes it 58.075 English inches; but, as there is
considerable uncertainty in the determinations of the weight of the
French cubical measure of water, owing to the uncertainty of the
standards made use of, it is better to abide by Mr Everard's measure,
which was with the Exchequer standards, and by the proportions of the
English and French foot, as established by the French Academy and Royal
Society.
[64] The whole of this and the following article was communicated to the
Translator by Professor Robinson.--E.
_THE PLATES_
[Illustration: _Plate I_]
[Illustration: _Plate I (continued)_]
[Illustration: _Plate II_]
[Illustration: _Plate II (continued)_]
[Illustration: _Plate III_]
[Illustration: _Plate III (continued)_]
[Illustration: _Plate IV_]
[Illustration: _Plate IV (continued)_]
[Illustration: _Plate V_]
[Illustration: _Plate V (continued)_]
[Illustration: _Plate VI_]
[Illustration: _Plate VI (continued)_]
[Illustration: _Plate VII_]
[Illustration: _Plate VII (continued)_]
[Illustration: _Plate VIII_]
[Illustration: _Plate VIII (continued)_]
[Illustration: _Plate IX_]
[Illustration: _Plate IX (continued)_]
[Illustration: _Plate X_]
[Illustration: _Plate X (continued)_]
[Illustration: _Plate XI_]
[Illustration: _Plate XI (continued)_]
[Illustration: _Plate XII_]
[Illustration: _Plate XII (continued)_]
[Illustration: _Plate XII (continued)_]
[Illustration: _Plate XII (continued)_]
[Illustration: _Plate XII (continued)_]
[Illustration: _Plate XIII_]
[Illustration: _Plate XIII (continued)_]
THE END.
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