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Title: A Dictionary of Arts, Manufactures and Mines - containing a clear exposition of their principles and practice
Author: Ure, Andrew
Language: English
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Transcriber’s Notes
Italicised texts in the original work have been transcribed between
_underscores_; small capitals have been transcribed as CAPITALS.
Superscript c is transcribed as ^{c}. ● and ○ represent a solid and an
open circle with a vertical line, respectively. [S] represents a letter
S rotated 90 degrees. In ([26 × 2] + [40 × 2]) the original work has a
horizontal line over the numbers between the square brackets.
More Transcriber’s notes may be found at the end of this text.
A
DICTIONARY
OF
ARTS, MANUFACTURES,
AND
MINES:
CONTAINING
A CLEAR EXPOSITION OF THEIR PRINCIPLES
AND PRACTICE.
BY
ANDREW URE, M.D.
F.R.S. M.G.S. M.A.S. LOND.; M. ACAD. N.S. PHILAD.; S. PH. SOC. N.
GERM. HANOV.; MULII. ETC. ETC.
ILLUSTRATED WITH TWELVE HUNDRED AND FORTY
ENGRAVINGS ON WOOD.
Second Edition.
LONDON:
PRINTED FOR
LONGMAN, ORME, BROWN, GREEN, & LONGMANS,
PATERNOSTER-ROW.
1840.
LONDON:
Printed by A. SPOTTISWOODE,
New-Street-Square.
PREFACE.
It is the business of operative industry to produce, transform, and
distribute all such material objects as are suited to satisfy the wants
of mankind. The primary production of these objects is assigned to the
husbandman, the fisherman, and the miner; their transformation to the
manufacturer and artisan; and their distribution to the engineer,
shipwright, and sailor.[1] The unworked or raw materials are
derived,--1. from the organic processes of vegetables and animals,
conducted either without or with the fostering care of man; 2. from the
boundless stores of mineral and metallic wealth, arranged upon or within
the surface of the earth by the benignant Parent of our being, in the
fittest condition to exercise our physical and intellectual powers in
turning them to the uses of life.
[1] For correct and copious information upon _agricultural_
production, I have great pleasure in referring my readers to Mr.
Loudon’s elaborate _Encyclopedias of Agriculture, Gardening, and
Plants_; and for _mercantile_ production and distribution, to Mr.
M’Culloch’s excellent _Dictionary of Commerce and Commercial
Navigation_.
The task which I have undertaken in the present work, is to describe and
explain the transformations of these primary materials, by mechanical
and chemical agencies, into general objects of exchangeable value;
leaving, on the one hand, to the mechanical engineer, that of
investigating the motive powers of transformation and transport; and, on
the other hand, to the handicraftsman, that of tracing their
modifications into objects of special or local demand. Contemplated in
this view, an art or manufacture may be defined to be that species of
industry which effects a certain change in a substance, to suit it for
the general market, by combining its parts in a new order and form,
through mechanical or chemical means. Iron will serve the purpose of
illustrating the nature of the distinctions here laid down, between
mechanical engineering; arts and manufactures; and handicraft trades.
The engineer perforates the ground with a shaft, or a drift, to the
level of the ore, erects the pumps for drainage, the ventilating, and
hoisting apparatus, along with the requisite steam or water power; he
constructs the roads, the bridges, canals, railways, harbours, docks,
cranes, &c., subservient to the transport of the ore and metal; he
mounts the steam or water power, and bellows for working the
blast-furnaces, the forges, and the cupolas; his principal end and aim
on all occasions being to overcome the forces of inertia, gravity, and
cohesion. The ores extracted and sorted by the miner, and transported by
the engineer to the smelting station, are there skilfully blended by the
iron-master (manufacturer), who treats them in a furnace appropriately
constructed, along with their due proportions of flux and fuel, whereby
he reduces them to cast iron of certain quality, which he runs off at
the right periods into rough pigs or regular moulds; he then transforms
this crude metal, by mechanical and chemical agencies, into bar and
plate iron of various sizes and shapes, fit for the general market; he
finally converts the best of the bars into steel, by the cementation
furnace, the forge, and the tilt-hammer; or the best of the plates into
tin-plate. When farther worked by definite and nearly uniform processes
into objects of very general demand in all civilized countries, these
iron and steel bars still belong to the domain of manufactures; as, for
example, when made into anchors, chain-cables, files, nails, needles,
wire, &c.; but when the iron is fashioned, into ever varying and
capricious forms, they belong either to the general business of the
founder and cutler, or to the particular calling of some handicraft, as
the locksmith, gratesmith, coachsmith, gunsmith, tinman, &c.
Such are the principles which have served to guide me in selecting
articles for the present volume. By them, as a clue, I have endeavoured
to hold a steady course through the vast and otherwise perplexing
labyrinth of arts, manufactures, and mines; avoiding alike engineering
and mechanical arts, which cause no change in the texture or
constitution of matter,--and handicraft operations, which are multiform,
capricious, and hardly susceptible of scientific investigation. In fact,
had such topics been introduced into the volume, it would have presented
a miscellaneous farrago of incongruous articles, too numerous to allow
of their being expounded in a manner either interesting or instructive
to the manufacturer and the metallurgist. I readily acknowledge,
however, that I have not been able to adhere always so rigorously as I
could have wished to the above rule of selection; having been
constrained by intelligent and influential friends to introduce a few
articles which I would gladly have left to the mechanical engineer. Of
these _Printing_ is one, which, having had no provision made for it in
my original plan, was too hastily compiled to admit of my describing,
with suitable figures, the flat-printing automatic machine of Mr.
Spottiswoode, wherewith the pages of this volume were worked off; a
mechanism which I regard as the most elegant, precise, and productive,
hitherto employed to execute the best style of letter press.
I have embodied in this work the results of my long experience as a
Professor of Practical Science. Since the year 1805, when I entered at
an early age upon the arduous task of conducting the schools of
chemistry and manufactures in the Andersonian Institution, up to the
present day, I have been assiduously engaged in the study and
improvement of most of the chemical and many of the mechanical arts.
Consulted professionally by proprietors of factories, workshops, and
mines, of various descriptions, both in this country and abroad,
concerning derangements in their operations, or defects in their
products, I have enjoyed peculiar opportunities of becoming familiar
with their minutest details, and have frequently had the good fortune to
rectify what was amiss, or to supply what was wanting. Of the stores of
information thus acquired, I have availed myself on the present
occasion; careful, meanwhile, to neglect no means of knowledge which my
extensive intercourse with foreign nations affords.
I therefore humbly hope that this work will prove a valuable
contribution to the literature of science, serving--
_In the first place_, to instruct the Manufacturer, Metallurgist, and
Tradesman, in the principles of their respective processes, so as to
render them in reality the masters of their business, and to emancipate
them from a state of bondage to operatives, too commonly the slaves of
blind prejudice and vicious routine.
_Secondly_, to afford to Merchants, Brokers, Drysalters, Druggists, and
Officers of the Revenue, characteristic descriptions of the commodities
which pass through their hands.
_Thirdly_, by exhibiting some of the finest developments of chemistry
and physics, to lay open an excellent practical school to students of
these kindred sciences.
_Fourthly_, to teach Capitalists, who may be desirous of placing their
funds in some productive bank of industry, to select judiciously among
plausible claimants.
_Fifthly_, to enable Gentlemen of the Law to become well acquainted with
the nature of those patent schemes which are so apt to give rise to
litigation.
_Sixthly_, to present to our Legislators such a clear exposition of our
staple manufactures, as may dissuade them from enacting laws which
obstruct industry, or cherish one branch of it to the injury of many
others: and,
_Lastly_, to give the General Reader, intent chiefly on intellectual
cultivation, a view of many of the noblest achievements of science, in
effecting those grand transformations of matter to which Great Britain
owes her paramount wealth, rank, and power among the kingdoms.
The latest statistics of every important object of manufacture is given,
from the best, and, usually, from official authority, at the end of each
article.[2]
[2] The statistics of agriculture, trade, and manufactures is ably and
fully discussed in Mr. M’Culloch’s _Dictionary_ already referred to.
The following summary of our manufactures is extracted from Mr.
Macqueen’s _General Statistics of the British Empire_, published in
1836. It shows the amount of capital embarked in the various
departments of manufacturing industry, and of the returns of that
capital:--
+----------------------------------+-----------+-----------+
| | Capital. | Produce. |
| +-----------+-----------+
| | _£_ | _£_ |
|Cotton manufactures | 40,973,872| 52,513,586|
|Woollen ditto | 36,000,000| 44,250,000|
|Silk ditto | 8,000,000| 10,000,000|
|Linen ditto | 12,000,000| 15,421,186|
|Leather ditto | 13,000,000| 16,000,000|
|Iron ditto, to making pig iron| 10,000,000| 7,098,000|
|Ditto, hardware, cutlery, &c. | 25,000,000| 31,072,600|
|Copper and brass ditto | 3,600,000| 4,673,186|
|China, glass, &c. | 8,600,000| 10,892,794|
|Paper, furniture, books, &c. | 10,000,000| 14,000,000|
|Spirits (British), ales, soap, &c.| 37,600,000| 47,163,847|
|Sundries additional | | 9,000,000|
| +-----------+-----------+
| Totals |204,773,872|262,085,199|
+----------------------------------+-----------+-----------+
In consequence of an arrangement with Mr. William Newton, patent agent,
and proprietor of the _London Journal of Arts, Sciences, and
Manufactures_, I have been permitted to enrich this Dictionary with many
interesting descriptions and illustrative figures of modern patent
inventions and improvements, which I could not otherwise have presented
to my readers. Mr. Newton has lately enhanced the value of his Journal
by annexing to it a _catalogue raisonnée_, entitled “An Analytical Index
to the Subjects contained in the 23 Volumes,” which constitute the first
and second series. The subsequent 13 volumes, of his Conjoined Series,
are of still superior interest; and the whole form a vast storehouse of
Mechanical and Chemical Invention.
Although I am conscious of having used much diligence for many years in
collecting information for this work, from every quarter within my
reach, the utmost pains in preparing it for publication, and incessant
vigilance during its passage through the press, yet I am fully aware
that it must contain several errors and defects. These I shall study to
rectify, should the Public deem this volume worthy of a supplement. In
this hope, I earnestly solicit the suggestions of my readers; trusting
that ere long our Post Office system will cease to be such an obstacle
as it has long been to the collection and diffusion of useful knowledge,
and a tax upon science which the remuneration of its literature cannot
by any means bear.
Since this book is not a Methodical Treatise, but a Dictionary, one
extensive subject may be necessarily dispersed through many articles.
Thus, for example, information upon the manufacture of _Colours_ will be
found under azure; black pigment; bone-black; bronze; brown dye;
calico-printing; carmine; carthamus; chromium; cochineal; crayons;
dyeing; enamels; gold; gilding; gamboge; gray dye; green dye; green
paints; indigo; kermes; lac dye; lakes; madder; massicot; mercury,
periodide of; Naples yellow; orange dye; orpiment; paints, grinding of;
ochres; paper-hangings; pastes; pearl white; Persian berries; pottery
pigments; Prussian blue; purple of Cassius; red lead; rouge; Scheele’s
green; Schweinfurth green; stained glass; terra di Sienna; ultramarine;
umber; verditer; vermilion; vitrifiable colours, weld, white lead; woad;
yellow, king’s.
A casual consulter of the Dictionary, who did not advert to this
distribution, might surmise it to be most deficient, where it is in
reality most copious.
The elaborate and costly Encyclopedias, and Dictionaries of Arts, which
have appeared from time to time in this country, and abroad, have, for
the most part, treated of the mechanical manufactures, more fully and
correctly than of the chemical. The operations of the former are, in
fact, tolerably obvious and accessible to the inspection of the curious;
nor are they difficult to transfer into a book, with the aid of a
draughtsman, even by a person but moderately versed in their principles.
But those of the latter are not unfrequently involved in complicated
manipulations, and depend, for their success, upon a delicate play of
affinities, not to be understood without an operative familiarity with
the processes themselves. Having enjoyed the best opportunities of
studying the chemical arts upon the greatest scale in this kingdom and
on the Continent, I may venture, without the imputation of arrogance, to
claim for my work, in this respect, more precision and copiousness than
its predecessors possess. I have gone as far in describing several
curious processes, hitherto veiled in mystery, as I felt warranted,
without breach of confidence, to go; regarding it as a sacred duty never
to publish any secret whatever, without the consent of its proprietor.
During my numerous tours through the factory districts of Great Britain,
France, &c., many suggestions, however, have been presented to my mind,
which I am quite at liberty to communicate in private, or carry into
execution, in other districts too remote to excite injurious competition
against the original inventors. I am also possessed of many plans of
constructing manufactories, of which the limits of this volume did not
permit me to avail myself, but which I am ready to furnish, upon
moderate terms, to proper applicants. I conclude by pointing attention
to the very insecure tenure by which patents for chemical or
chemico-mechanical inventions are held; of which there is hardly one on
record which may not be readily evaded by a person skilled in the
resources of practical chemistry, or which could stand the ordeal of a
court of law directed by an experienced chemist. The specifications of
such patents stand in need of a thorough reform; being for the most part
not only discreditable and delusive to the patentees, but calculated to
involve them in one of the greatest of evils--a chancery suit.
LONDON:
13. Charlotte Street, Bedford Square,
March 1. 1839.
DR. URE is preparing for publication, in one large volume, 8vo.,
CHEMISTRY IN THEORY AND PRACTICE; embodying a New System of Research, of
such facility and precision, as will enable chemical manufacturers of
every class, medical practitioners, metallurgists, farmers, merchants,
brokers, druggists, drysalters, officers of the revenue, as well as
general students, to analyze their respective objects in much less time
than is usually required at present by professional chemists. A
descriptive Index will be annexed for converting this systematic work
into a Dictionary of Chemical Science.
A
DICTIONARY
OF
ARTS, MANUFACTURES, AND MINES.
ABB-WOOL. Among clothiers, this term signifies the _woof_ or _weft_.
ACETATE. (_Acétate_, Fr.; _Essigsäure_, Germ.) Any saline compound of
which the acetic is the acid constituent; as acetate of soda, of iron,
of copper, &c.
ACETATE OF ALUMINA, see RED LIQUOR and MORDANT; of COPPER, see COPPER;
of IRON, see IRON; of LEAD, see LEAD; of LIME, see PYROLIGNOUS ACID.
ACETIC ACID (_Acide Acétique_, Fr.; _Essigsäure_, Germ.) is the name of
the sour principle which exists in vinegar. It occurs, ready formed, in
several products of the vegetable kingdom, and is generated during the
spontaneous fermentation of many vegetable and animal juices. The
_sambucus nigra_, or black elder, the _phœnix dactilifera_, and the
_rhus typhinus_ are plants which afford a notable quantity of vinegar.
It is found, likewise, in the sweat, urine, milk, and stomach of
animals. All infusions of animal or vegetable matters in water, when
exposed for some time to the air, at a moderate temperature, ferment
into vinegar; and most vegetables, when subjected to decomposition by
fire, give off condensable vapours of acetic acid. All liquids
containing alcohol are susceptible of passing into the state of vinegar;
but the pre-existence of alcohol is not necessary to this change, as we
learn from the acetification of vegetable soups, infusion of cabbage,
starch--paste, &c.
Vinegar may be distinguished into four varieties, according to the mode
of its production, though all of them are capable of being converted, by
chemical means, into one identical acetic acid. 1. Wine vinegar. 2. Malt
vinegar. 3. Sugar vinegar. 4. Wood vinegar, or pyrolignous acid.
Fermentation is the source of the acid in the first three varieties.
Here alcohol is first generated, and is next converted into vinegar by
the influence of the air at a genial temperature; a change which will be
investigated under FERMENTATION. But the conversion of spirit of wine
into acetic acid may be demonstrated by direct experiment. When the
vapour of alcohol is brought into contact in the atmosphere with the
black powder obtained by mixing muriate of platina, potash, and alcohol,
vinegar is rapidly formed at the expense of the alcohol. In Germany,
where crude alcohol bears a low price, the manufacture of vinegar has
been arranged upon that principle, which, as throwing some light on the
process of acetification, I shall briefly describe. See PLATINUM _for
the mode of preparing the above powder_.
Under a large case, which for experimental purposes may be made of
glass, several saucer-shaped dishes of pottery or wood are to be placed
in rows, upon shelves over each other, a few inches apart. A portion of
the black platina powder moistened being suspended over each dish, let
as much vinous spirits be put into them as the oxygen of the included
air shall be adequate to acidify. This quantity may be inferred from the
fact, that 1000 cubic inches of air can oxygenate 110 grains of absolute
alcohol, converting them into 122 grains of absolute acetic acid, and
64-1/2 grains of water.
The above simple apparatus is to be set in a light place (in sunshine,
if convenient), at a temperature of from 68° to 86° Fahr., and the
evaporation of the alcohol is to be promoted by hanging several leaves
of porous paper in the case, with their bottom edges dipped in the
spirit. In the course of a few minutes, a most interesting phenomenon
will be perceived. The mutual action of the platina and the alcohol will
be displayed by an increase of temperature, and a generation of acid
vapours, which, condensing on the sides of the glass-case, trickle in
streams to the bottom. This striking transformation continues till all
the oxygen of the air be consumed. If we wish, then, to renew the
process, we must open the case for a little, and replenish it with air.
With a box of 12 cubic feet in capacity, and with a provision of 7 or 8
ounces of the platina powder we can, in the course of a day, convert
one pound of alcohol into pure acetic acid, fit for every purpose,
culinary or chemical. With from 20 to 30 pounds of the platina powder
(which does not waste), we may transform, daily, nearly 300 pounds of
bad spirits into the finest vinegar. Though our revenue laws preclude
the adoption of this elegant process upon the manufacturing scale in
this country, it may be regarded as one of the greatest triumphs of
chemistry, where art has rivalled nature in one of her most mysterious
operations.
To readers acquainted with chemical symbols, the following numerical
representation of the conversion of alcohol into acetic acid may be
acceptable:--
580·64 parts by weight of alcohol = H¹² C⁴ O² consist of
74·88 of hydrogen = H¹²
305·76 of carbon = C⁴
200·00 of oxygen = O²
If we combine with this mixture, 400 parts of oxygen = O⁴, we have,--
of water = 337·44 = H⁶ O³
acetic acid = 643·20 = H⁶ C⁴ O³
Hence, in this formation of vinegar, 100 parts by weight of alcohol take
68·89 parts of oxygen; and there are produced 58·11 parts of water, and
110·78 of acetic acid.
These beautiful experiments prove, that when in a mere mixture of
alcohol and water, under the influence of the atmospheric air and heat,
some vinegar comes to be formed after a considerable time, the same
formation of vinegar takes place in a similar, but more effective,
manner, when a ferment is present, which acts here in a somewhat
analogous way to the platina powder in the preceding case. Several
azotized substances serve as re-agents towards the acetous
fermentation,--such as vinegar ready-made, vinegar-yeast, or lees,
barley bread, leaven, beer barm, and similar vegetable matters, which
contain gluten. The best and purest ferment is, however, vinegar itself.
With this ferment we must conjoin, as an essential condition of
acetification, the free access of atmospheric air.
It is a well-known fact, that spirituous liquors, as weak brandy, wine,
and beer, &c., may be preserved for years in close vessels, without
undergoing the acetous fermentation, even when they repose upon a layer
of lees. It is equally well known, that these very liquors, if they
stand for some time in open vessels, become readily sour, especially if
exposed, also, to a somewhat high temperature. If we fill a flask with
common brandy, and subject it, without a stopper, to the influence of
air and warmth, the contained liquor may, at the end of many weeks,
discover no sensible acidity: if we add to the same brandy a ferment,
and stop the flask air-tight, everything will still remain unchanged;
but if we leave a portion of air in the flask, or leave it uncorked,
vinegar will soon make its appearance in the brandy.
If we investigate the nature of the air which remains over brandy in the
act of acetification, we shall find that it consists entirely of
carbonic acid and azote, the oxygen being absorbed and combined in the
acetic acid and water formed.
Since this absorption of oxygen from the air can take place only at the
surface of the fermenting liquors, we thus see the necessity and the
practical importance of amplifying that surface, in order to accelerate
and complete the acetification, by multiplying the points of contact
between the alcohol and the oxygen. The essence of the new German method
of rapid acetification depends upon this principle.
Temperature has also a remarkable influence on the formation of vinegar.
The acid fermentation proceeds very feebly in the cold, but takes an
accelerated pace as the heat is raised. It would even appear that
spirituous vapours brought by themselves in contact with atmospheric
air, without the aid of any ferment, are capable of being converted into
acetic acid, since it has happened in the rectification of brandy, in a
still furnished with a large capital and adopter pipe into which air was
allowed to enter, that vinegar made its appearance. Hence, warmth does
not seem to act as a promoter of the combination of alcohol with oxygen
in a merely chemical point of view, but it acts, so to speak,
physically. Over the warm liquor a stratum of spirit vapour appears to
float, which, coming there into conflict with the atmospherical oxygen,
probably causes the generation of some acetic acid, and thus accelerates
the operation, much more than by the mere contact of the oxygen with the
liquid surface.
When we expose any spirituous liquors, as wine, beer, &c., with the
requisite ferment, to the external air, at a temperature of from 64° to
68° Fahr., the fluid, however clear before, becomes soon turbid;
filamentous slimy particles begin to appear moving in the middle and on
the sides of the vessel, and then form a scum on the top of the liquor.
When this scum has acquired a certain thickness and consistence, it
falls in a sediment to the bottom. The Germans call it the vinegar
_mother_, as it serves to excite acetification in fresh liquors.
Meanwhile, the liquor has become warmer than the surrounding air, and
the vinegar process betrays itself by diffusing a peculiar aroma in the
apartment. Whenever all the alcohol present has been converted into
acetic acid, the liquor comes into a state of repose; its temperature
sinks to the pitch of the atmosphere; it becomes bright, and is the
article well known by its taste and smell under the name of vinegar.
Genuine wine or raisin vinegar differs from that formed either from
apples, or sugar, beer, &c., in containing wine-stone or tartar; by
which peculiarity it may be distinguished, except in those cases where
crude tartar has been artificially added to the other vinegars, as a
disguise. Barley-malt vinegar contains some phosphoric acid, in the
state of phosphate of lime or magnesia, derived from the grain.
After these general observations upon acetification, we shall now
proceed to describe the processes for manufacturing vinegar on the
commercial scale.
1. _Wine vinegar._--The first consideration with a vinegar maker is a
good fermenting room, in which the wines may be exposed to a steady
temperature, with an adequate supply of atmospherical air. As this air
is soon deprived of its oxygenous constituent, facilities ought to be
provided for a renewal of it by moderate ventilation. The air holes for
this purpose ought to be so contrived that they may be shut up when the
temperature begins to fall too low, or in windy weather. The best mode
of communicating the proper warmth to a chamber of this kind is by means
of fire-flues or hot water pipes, running along its floor at the sides
and ends, as in a hothouse; the fireplace being on the outside, so that
no dust may be created by it within. The flue is best made of bricks,
and may have a cross section of 10 or 12 inches by 15 deep. The soot
deposited, even when coals are burned, will find ample space in the
bottom of the flue, without interfering essentially with the draught,
for a very long period, if it be made of the above dimensions.
Low-roofed apartments are preferable to high ones; and those built with
thick walls, of imperfectly conducting materials, such as bricks, lined
with lath and plaster work. Should the chamber, however, have a high
ceiling, the fermenting tuns must be raised to a suitable height on
scaffolding, so as to benefit by the warmest air. Sometimes the vinegar
vessels are placed at different levels; in which case the upper ones
acetify their contents much sooner than the under, unless they are
emptied and filled alternately, which is a good plan.
Orleans is the place most famous for vinegars. The building there
destined to their manufacture is called a _vinaigrerie_, and is placed,
indifferently, either on the ground floor or the floor above it; but it
has always a southern exposure, to receive the influence of the
sunbeams. The vessels employed for carrying on the fermentation are
casks, called _mothers_. Formerly they were of a large capacity,
containing about 460 litres (115 gallons, Eng.); but at the present day
they are barrels of half that capacity, or somewhat less than an old
English hogshead. It is now known that the wine passes sooner into
vinegar the smaller the mass operated upon, the more extensive its
contact with the air, and the more genial its warmth. These casks were
formerly arranged in three ranks by means of massive scaffolding; they
are now set in four ranks, but they rest on much smaller rafters,
sustained by uprights, and can be packed closer together. The casks,
which are laid horizontally, are pierced at the upper surface of their
front end with two holes: one, to which the name of _eye_ is given, is
two inches in diameter; it serves for putting in the charge, and drawing
off the vinegar when it is made; the other hole is much smaller, and is
placed immediately alongside; it is merely an air hole, and is necessary
to allow the air to escape, because the funnel completely fills the
other hole in the act of filling the cask.
When new vessels are mounted in a vinegar work, they must be one third
filled with the best vinegar that can be procured, which becomes the
true _mother_ of the vinegar to be made; because it is upon this portion
that the wine to be acidified is successively added. At the ordinary
rate of work, they put at first upon the _mother_, which occupies one
third of the vessel, a _broc_ of 10 litres of red or white wine; eight
days afterwards they add a second _broc_; then a third, and a fourth,
always observing the same interval of time, 8 days. After this last
charge, they draw off about 40 litres of vinegar, and then recommence
the successive additions.
It is necessary that the vessel be always one third empty if we wish the
acetification to go on steadily; but as a portion of the tartar and the
lees forms and accumulates in the lower part of the cask, so as
eventually to counteract the fermentation, the time arrives when it is
requisite to interrupt it, in order to remove this residuum, by clearing
out all the contents. The whole materials must be renovated every 10
years; but the casks, if well made and repaired, will serve for 25
years.
We have mentioned a definite period at which the vinegar may be drawn
off; but that was on the supposition that the process had all the
success we could wish: there are circumstances, difficult to appreciate,
which modify its progress, as we shall presently show. We ought,
therefore, before discharging the vinegar, to test and see if the
fermentation has been complete. We proceed as follows: we plunge into
the liquor a white stick or rod, bent at one end, and then draw it out
in a horizontal direction: if it be covered with a white thick froth, to
which is given the name of _work_ (_travail_), we judge that the
operation is terminated; but if the work, instead of being white and
pearly, be red, the manufacturers regard the fermentation to be
unfinished, and they endeavour to make it advance, by adding fresh wine,
or by increasing the heat of the apartment.
It is not always easy to explain why the fermentation does not go on as
rapidly in one case as in another. There are even certain things which
seem at present to be entirely inexplicable. It happens sometimes, for
example, that although all the vessels have been equally charged, and
with the same wine, yet the fermentation does not form in the same
manner in the whole; it will move rapidly in some, be languid, or
altogether inert, in others. This is a very puzzling anomaly; which has
been ascribed to electrical and other obscure causes, because it is not
owing to want of heat, the casks in the warmest positions being
frequently in fault; nor to the timber of the cask. It, however,
paralyses the process so completely that the most expert vinegar makers
have nothing else for it, when this accident happens, than to empty
entirely what they call the lazy cask, and to fill it with their best
vinegar. The fermentation now begins, and proceeds as well in it as in
the others. See FERMENTATION.
We must here make an important remark, relatively to the temperature
which should prevail in the fermentation room. In many chemical works we
find it stated, that the heat should not exceed 18° R., or 65° Fahr.,
for fear of obtaining bad products. But the vinegar makers constantly
keep up the heat at from 24° to 25° R., 75° to 77° F.; when the
acetification advances much more rapidly, and the vinegar is equally
strong. The best proof of this heat not being too high is, that under
it, the vessels in the upper part of the room, work best and quickest.
In Orleans, cast-iron stoves and wood fuel are used for communicating
the requisite warmth.
Before pouring the wine into the _mothers_, it is clarified in the
following manner. There are tuns which can contain from 12 to 15 pieces
of wine. Their upper end has at its centre an opening of four or five
inches diameter, which may be closed afterwards with a wooden cover;
this opening is for the purpose of receiving a large funnel. The inside
of the tun is filled with chips of beechwood, well pressed down. The
wine is poured upon these chips, allowed to remain for some time, and
then gently drawn off by a pipe in the lower part of the vessel. The
lees are deposited upon the chips, and the wine runs off quite clear.
However, it happens sometimes, notwithstanding this precaution, that the
vinegar, after it is made, requires to be clarified, more particularly
if the wine employed had been weak. The vinegar must be filtered in the
same way; and it derives an advantage from it, as the products of
different casks get thereby mixed and made uniform.
By this Orleans method several weeks elapse before the acetification is
finished; but a plan has been lately devised in Germany to quicken
greatly the acid fermentation by peculiar constructions. This system is
called, the _quick_ vinegar work, because it will complete the process
in the course of 2 or 3 days, or even in a shorter time. It depends,
chiefly, upon the peculiar construction of the fermenting vessels,
whereby the vinous liquor is exposed on a vastly expanded surface to the
action of the atmospheric air.
An oaken tub, somewhat narrower at the bottom than the top, from 6 to 7
feet high and 3 feet in diameter, is furnished with a well-fitted
grooved, but loose, cover. About half a foot from its mouth, the tub has
a strong oak or beech hoop fitted to its inside surface, sufficiently
firm to support a second cover, also well fitted, but moveable. The
space under this second cover is destined to contain the vinous liquor,
and in order to bring it very amply into contact with the atmosphere,
the following contrivances have been resorted to: This cover is
perforated, like a sieve, with small holes, of from 1 to 2 lines in
diameter, and about 1-1/2 inch apart. Through each of these holes a wick
of pack-thread or cotton is drawn, about 6 inches long, which is
prevented from falling through by a knot on its upper end, while its
under part hangs free in the lower space. The wicks must be just so
thick as to allow of the liquor poured above the cover passing through
the holes in drops. The edges of the lid must be packed with tow or hemp
to prevent the liquor running down through the interval.
The whole lower compartment is now to be filled with chips of beechwood
up to nearly the perforated cover. The liquor, as it trickles through
the holes, diffuses itself over the chips, and, sinking slowly, collects
at the bottom of the tub. The chips should be prepared for this purpose
by being repeatedly scalded in boiling water, then dried, and imbued
with hot vinegar. The same measures may also be adopted for the tub. To
provide for the renewal of the air, the tub is perforated at about a
foot from its bottom with eight holes, set equally apart round the
circumference, two thirds of an inch wide, and sloping down, through
which the air may enter into this lower compartment, without the
trickling liquor being allowed to flow out. In order that the foul air
which has become useless may escape, four large holes are pierced in
the sieve cover, at equal distances asunder and from the centre, whose
united areas are rather smaller than the total areas of the holes in the
side of the tub. Into these four holes open glass tubes must be
inserted, so as to stand some inches above the cover, and to prevent any
of the liquor from running through them. The proper circulation of the
air takes place through these draught holes. This air may afterwards
pass off through a hole of 2-1/2 inches diameter in the uppermost cover,
in which a funnel is placed for the supply of liquor as it is wanted to
keep up the percolation.
The temperature of the fermenting compartment is ascertained by means of
a thermometer, whose bulb is inserted in a hole through its side, and
fastened by a perforated cork. The liquor collected in the under vessel
runs off by a syphon inserted near its bottom, the leg of which turns up
to nearly the level of the ventilating air pipes before it is bent
outwards and downwards. Thus the liquor will begin to flow out of the
under compartment only when it stands in it a little below the sieve
cover, and then it will run slowly off at the inclined mouth of the
syphon, at a level of about 3 inches below the lower end of the glass
tubes. There is a vessel placed below, upon the ground, to receive it.
The tub itself is supported upon a wooden frame, or a pier of brickwork,
a foot or 18 inches high.
A tub constructed like the above is called a GRADUATION VESSEL, which
see. It is worked in the following way:--The vinegar room must be, in
the first place, heated to from 100° to 110° F., or till the thermometer
in the graduation vessel indicates at least 77°. The heat may then be
modified. We now pour through the uppermost cover of the tub a mixture,
warmed to 144° F., of 8 parts proof spirits, 25 parts soft water, 15
parts of good vinegar, and as much clear wine or beer. The water should
be first heated, and then the vinegar, spirits, and wine may be added to
it. Of this mixture, so much should be poured in as is necessary to
cover over the second lid, 2 or 3 inches deep, with the liquor; after
which, the rest may be poured slowly in, as it is wanted.
When the liquor has run for the first time through the graduation
vessel, it is not yet sufficiently acidified; but the weak vinegar
collected in the exterior receiving cistern must be a second time, and,
if need be, a third time, passed through the graduation tub, in order to
convert all the alcohol into acetic acid. In general, we may remark,
that the stronger the vinous liquor the more difficult and tedious is
its conversion into vinegar, but it is so much the stronger. To lessen
this difficulty somewhat, it would be well not to put all the spirits at
first into the wash, or mixed liquors, but to add a little more of it at
the second and the third running, especially when we desire to have very
strong vinegar.
After the graduation vessel has been some days at work, it is no longer
necessary to add vinegar to the mixture of spirits and water, since the
sides of the graduation tub, the beech chips, and the packthreads, are
all impregnated with the ferment, and supply its place. The mixture
must, however, be always maintained at the temperature of 100°.
Instead of the above mixture of brandy, water, and wine, we may employ,
according to Dingler, a clear fermented wort of malt, mixed with a
little spirits. The perfect vinegar, which collects in the receiving
cistern, may be immediately racked off into the store casks for sale.
It has been objected to this process, that, in consequence of the
mixture of saccharine and glutinous materials, which are contained in
beer or worts, along with the acetous fermentation, there is also,
partially, a vinous fermentation, and much carbonic acid, thereby
disengaged, so as to obstruct the acetification. This obstruction may be
remedied by a freer circulation of air, or by the exposure of quicklime
in the chamber. It is a more substantial objection, that, from the
addition of beer, &c., more lees, or dregs, are deposited in the
graduation tub, whereby a more frequent cleansing of it, and of the
beech chips, with a loss of time and vinegar, becomes necessary. The
only mode of obviating this difficulty is, to take well-clarified
fermented wash.
Another evil attendant on the quick process is, the evaporation of the
spirituous liquors. Since, in the graduation tub, there is a temperature
of 110°, it is impossible to avoid a loss of spirit from the circulation
and efflux of the air. The air, indeed, that issues from the top hole in
the uppermost cover, might be conducted over an extensive surface of
fresh water, where its spirit would be condensed in a great measure.
But, after all, this fear of great loss is, I believe, groundless;
because the spirit is rapidly acidified by the oxygen of the air, and
thereby rapidly loses its volatility.
The supply of the warm wash should be drawn from a cistern placed near
the ceiling, where the temperature of the apartment is hottest; and it
may be replenished from the partly acetified liquor in the cistern on
the floor. With this view, two cisterns should be placed above, so that
one of them may always contain liquor sufficiently hot, and thus the
process will suffer no interruption.
When malt wash is used for this quick process, the resulting vinegar
must be clarified in a tun with beech chips, as above described. In two
or three days the impurities will be deposited, and the fine vinegar may
be racked off.
The following prescription, for preparing what he calls malt wine, is
given by Dr. Kastner. Eighty pounds of pale barley malt, and 40 pounds
of pale wheat malt, are to be crushed together. These 120 pounds are to
be infused with 150 quarts of water, at the temperature of 122° Fahr.,
afterwards with 300 quarts of boiling water, and the whole body is to be
mashed thoroughly, till all the lumps disappear. It is then to be left
at rest in a large covered tub, for two or three hours, to allow the
grains to settle down, from which the wort is to be drawn off. When it
has fallen to the temperature of 64° Fahr., 15 pounds of good yeast are
to be stirred in, and it must now be left for two or three days to
ferment, in a loosely covered tun. When the vinous fermentation has
taken place, the clear liquor must be drawn off by a tap hole, a little
above the bottom, so as to leave the lees and scum in the tun. This malt
wine, he adds, may be kept for a long time in close vessels, and is
always ready for making quick vinegar.
2. _Malt Vinegar._--The greater part of British vinegar is made from
malt, by the following process:--1 boll of good barley malt, properly
crushed, is to be mashed with water at 160° Fahr. The first water should
have that temperature; the second must be hotter than 160°, and the
third water, for the extraction of all the soluble matter, may be
boiling hot. Upon the whole, not more than 100 gallons of wort should be
extracted. After the liquor has cooled to 75° Fahr., 3 or 4 gallons of
beer yeast are poured in, and well mixed with a proper stirrer. In 36 or
40 hours, according to the temperature of the air, and the fermenting
quality of the wash, it is racked off into casks, which are laid upon
their sides in the fermenting apartment of the vinegar work, which
should be kept at a temperature of 70° at least; in summer partly by the
heat of the sun, but in general by the agency of proper stoves, as above
described. The bung-holes should be left open, and the casks should not
be full, in order that the air may act over an extensive surface of the
liquor. It would be proper to secure a freer circulation to the air, by
boring a hole in each end of the cask, near its upper edge. As the
liquor, by evaporation, would be generally a few degrees colder than the
air of the apartment, a circulation of air would be established in at
the bung-hole, and out by the end holes. By the ordinary methods, three
months are required to make this vinegar marketable, or fit for the
manufacture of sugar of lead.
In making vinegar for domestic purposes, the casks are usually set on
their ends; and they have, sometimes, a false bottom, pierced with
holes, placed about a foot above the true one. On this bottom, a
quantity of _rape_, or the refuse raisins, &c. from the making of
British wines, is laid. The malt liquor has a proper quantity of yeast
added to it. In about 24 hours it becomes warm, and is then racked off
into another similar cask. After some time, this racking process is
discontinued, and the vinegar is allowed to complete its fermentation
quietly. The proper temperature must always be kept up, by placing the
cask in a warm situation. A little wine-stone (_argal_) added to the
malt wash, would make the vinegar liker that made from wine. Sometimes a
little isinglass is employed to clarify vinegar. A portion of sulphuric
acid is often added to it.
3. _Sugar vinegar._--By pursuing the following plan, an excellent sugar
vinegar may be made. In 158 quarts of boiling water dissolve 10 pounds
of sugar, and 6 pounds of wine-stone; put the solution into a fermenting
cask, and when it is cooled to the temperature of from 75° to 80°, add 4
quarts of beer yeast to it. Stir the mixture well, then cover the vessel
loosely, and expose it for 6 or 8 days to the vinous fermentation, at a
temperature of from 70° to 75° Fahr. When it has become clear, draw off
the vinous liquor, and either acetify it in the graduation tub above
described, or by the common vinegar process. Before it is finished, we
should add to it 12 quarts of strong spirits (brandy), and 15 quarts of
good vinegar, to complete the acetous fermentation. With a graduation
tub which has been used, this addition of vinegar is unnecessary.
The following simpler prescription for making sugar vinegar deserves
attention. For every gallon of hot water take 18 ounces of sugar; and
when the syrup has cooled to 75°, add 4 per cent., by measure, of yeast.
When the vinous fermentation is pretty well advanced, in the course of 2
or 3 days, rack off the clear wash from the lees into a proper cask, and
add 1 ounce of wine-stone, and 1 of crushed raisins, for every gallon of
water. Expose it in a proper manner, and for a proper time, to the
acetifying process; and then rack off the vinegar, and fine it upon
beech chips. It should be afterwards put into bottles, which are to be
well corked.
Vinegar obtained by the preceding methods has always a yellowish or
brownish colour. It may be rendered colourless by distillation. For
nicer chemical purposes, this is done in a glass retort; but on a large
scale, it is usually performed in a clean copper still, furnished with a
capital and worm-refrigeratory, either of silver or block tin. It is
volatile at the boiling temperature of water; and if the process be
carried on briskly, it will not sensibly corrode the copper. But we can
never obtain, in this way, a strong article; for, as soon as the vinegar
gets concentrated to a certain degree, we cannot force off the
remainder by heat, for fear of giving it an empyreumatic odour; because
the gluten, colouring matter, &c. begin to adhere to the bottom of the
still. We are, therefore, obliged to suspend the operation at the very
time when the acid is acquiring strength. It has been also proposed to
concentrate vinegar by the process of congelation; but much of it
remains entangled among the frozen water; and common distilled vinegar
is so weak, that it congeals in one mass.
[Illustration: _Fig._ 1.]
Before the process for pyrolignous acid, or wood vinegar, was known,
there was only one method of obtaining strong vinegar practised by
chemists; and it is still followed by some operators, to prepare what is
called radical or aromatic vinegar. This consists in decomposing, by
heat alone, the crystallised binacetate of copper, commonly, but
improperly, called distilled verdigris. With this view, we take a
stoneware retort, (_fig._ 1.) of a size suited to the quantity we wish
to operate upon; and coat it with a mixture of fire clay and horsedung,
to make it stand the heat better. When this coating is dry, we introduce
into the retort the crystallised acetate slightly bruised, but very dry;
we fill it as far as it will hold without spilling when the beak is
considerably inclined. We then set it in a proper furnace. We attach to
its neck an adopter pipe, and two or three globes with opposite
tubulures, and a last globe with a vertical tubulure. The apparatus is
terminated by a Welter’s tube, with a double branch; the shorter issues
from the last globe, and the other dips into a flask filled with
distilled vinegar. Every thing being thus arranged, we lute the joinings
with a putty made of pipeclay and linseed oil, and cover them with glue
paper. Each globe is placed in a separate basin of cold water, or the
whole may be put into an oblong trough, through which a constant stream
of cold water is made to flow. The tubes must be allowed a day to dry.
Next day we proceed to the distillation, tempering the heat very nicely
at the beginning, and increasing it by very slow degrees till we see the
drops follow each other pretty rapidly from the neck of the retort, or
the end of the adopter tube. The vapours which pass over are very hot,
whence a series of globes are necessary to condense them. We should
renew, from time to time, the water of the basins, and keep moist pieces
of cloth upon the globes; but this demands great care, especially if the
fire be a little too brisk, for the vessels become, in that case, so
hot, that they would infallibly be broken, if touched suddenly with cold
water. It is always easy for us to regulate this operation, according to
the emission of gas from the extremity of the apparatus. When the air
bubbles succeed each other with great rapidity, we must damp the fire.
The liquor which passes in the first half hour is weakest; it proceeds,
in some measure, from a little water sometimes left in the crystals,
which when well made, however, ought to be anhydrous. A period arrives
towards the middle of the process when we see the extremity of the beak
of the retort, and of the adopter, covered with crystals of a lamellar
or needle shape, and of a pale green tint. By degrees these crystals are
carried into the condensed liquid by the acid vapours, and give a colour
to the product. These crystals are merely some of the cupreous salt
forced over by the heat. As the process approaches its conclusion, we
find more difficulty in raising the vapours; and we must then augment
the intensity of the heat, in order to continue their disengagement.
Finally, we judge that the process is altogether finished, when the
globes become cold, notwithstanding the furnace is at the hottest, and
when no more vapours are evolved. The fire may then be allowed to go
out, and the retort to cool.
As the acid thus obtained is slightly tinged with copper, it must be
rectified before bringing it into the market. For this purpose we may
make use of the same apparatus, only substituting for the stoneware
retort a glass one, placed in a sand bath. All the globes ought to be
perfectly clean and dry. The distillation is to be conducted in the
usual way. If we divide the product into thirds, the first yields the
feeblest acid, and the third the strongest. We should not push the
process quite to dryness, because there remains in the last portions
certain impurities, which would injure the flavour of the acid.
The total acid thus obtained forms nearly one half of the weight of the
acetate employed, and the residuum forms three tenths; so that about two
tenths of the acid have been decomposed by the heat, and are lost. As
the oxide of copper is readily reduced to the metallic state, its oxygen
goes to the elements of one part of the acid, and forms water, which
mingles with the products of carbonic acid, carburetted hydrogen, and
carbonic oxide gases which are disengaged; and there remains in the
retort some charcoal mixed with metallic copper. These two combustibles
are in such a state of division, that the residuum is pyrophoric. Hence
it often takes fire the moment of its being removed from the cold
retort. The very considerable loss experienced in this operation has
induced chemists to try different methods to obtain all the acid
contained in the acetate. Thus, for example, a certain addition of
sulphuric acid has been prescribed; but, besides that the radical
vinegar obtained in this way always contains sulphurous acid, from which
it is difficult to free it, it is thereby deprived of that spirit called
the _pyro-acetic_, which tempers the sharpness of its smell, and gives
it an agreeable aroma. It is to be presumed, therefore, that the
preceding process will continue to be preferred for making aromatic
vinegar. Its odour is often further modified by essential oils, such as
those of rosemary, lavender, &c.
4. _Pyrolignous Acid, or Wood Vinegar._--The process for making this
acid is founded upon the general property of heat, to separate the
elements of vegetable substances, and to unite them anew in another
order, with the production of compounds which did not exist in the
bodies subjected to its action. The respective proportion of these
products varies, not only in the different substances, but also in the
same substance, according as the degree of heat has been greater or
less, or conducted with more or less skill. When we distil a vegetable
body in a close vessel, we obtain at first the included water, or that
of vegetation; there is next formed another portion of water, at the
expense of the oxygen and hydrogen of the body; a proportional quantity
of charcoal is set free, and, with the successive increase of the heat,
a small portion of charcoal combines with the oxygen and hydrogen to
form acetic acid. This was considered, for some time, as a peculiar
acid, and was accordingly called _pyrolignous_ acid. As the proportion
of carbon becomes preponderant, it combines with the other principles,
and then some empyreumatic oil is volatilised, of little colour, but
which becomes thicker, and of a darker tint, always getting more loaded
with carbon.
Several elastic fluids accompany these different products. Carbonic acid
comes over, but in small quantity, much carburetted hydrogen, and,
towards the end, a considerable proportion of carbonic oxide. The
remainder of the charcoal, which could not be carried off in these
several combinations, is found in the retort, and preserves, usually,
the form of the vegetable body which furnished it. Since mankind have
begun to reason on the different operations of the arts, and to raise
them to a level with scientific researches they have introduced into
several branches of manufacture a multitude of improvements, of which,
formerly, they would hardly have deemed them susceptible. Thus, in
particular, the process for carbonising wood has been singularly
meliorated, and in reference to the preceding observations, advantage
has been derived from several products that formerly were not even
collected.
[Illustration: _Fig._ 2.]
The apparatus employed for obtaining crude vinegar from wood, by the
agency of heat, are large iron cylinders. In this country they are made
of cast iron, and are laid horizontally in the furnace; in France, they
are made of sheet iron riveted together, and they are set upright in the
fire. _Fig._ 2. will give an accurate idea of the British plan, which is
much the same as that adopted for decomposing pit coal in gas works,
only that the cylinders for the pyrolignous acid manufacture are
generally larger, being frequently 4 feet in diameter, and 6 or 8 feet
long, and built horizontally in brickwork, so that the flame of one
furnace may play around two of them. It would, probably, answer better,
if their size were brought nearer the dimensions of the gas-light
retorts, and if the whole system of working them were assimilated to
that of coal gas.
The following arrangement is adopted in an excellent establishment in
Glasgow, where the above large cylinders are 6 feet long, and both ends
of them project a very little beyond the brickwork. One end has a disc
or round plate of cast iron, well fitted, and firmly bolted to it, from
the centre of which disc an iron tube, about 6 inches diameter, proceeds
and enters, at a right angle, the main tube of refrigeration. The
diameter of this tube may be from 9 to 14 inches, according to the
number of cylinders. The other end of the cylinder is called the mouth
of the retort; this is closed by a disc of iron, smeared round its edge
by clay lute, and secured in its place by fir wedges. The charge of wood
for such a cylinder is about 8 cwt. The hard woods--oak, ash, birch, and
beech--are alone used; fir does not answer. The heat is kept up during
the day-time, and the furnace is allowed to cool during the night. Next
morning, the door is opened, the charcoal removed, and a new charge of
wood is introduced. The average product of crude vinegar called
pyrolignous acid, is 35 gallons. It is much contaminated with tar, is of
a deep brown colour, and has a sp. gr. of 1·025. Its total weight is
therefore about 300 lbs., but the residuary charcoal is found to weigh
no more than one fifth of the wood employed; hence nearly one half of
the ponderable matter of the wood is dissipated in incondensable gases.
Count Rumford states, that the charcoal is equal in weight to more than
four tenths of the wood from which it is made. The count’s error seems
to have arisen from the slight heat of an oven to which his wood was
exposed in a glass cylinder. The result now given, is the experience of
an eminent manufacturing chemist.
The crude pyrolignous acid is rectified by a second distillation in a
copper still, in the body of which about 20 gallons of viscid tarry
matter are left from every 100. It has now become a transparent brown
vinegar, having a considerably empyreumatic smell, and a sp. gr. of
1·013. Its acid powers are superior to those of the best household
vinegar, in the proportion of three to two. By redistillation,
saturation with quicklime, evaporation of the liquid acetate to dryness,
and conversion into acetate of soda by sulphate of soda, the
empyreumatic matter is so completely dissipated, that on decomposing the
pure acetate of soda by sulphuric acid, a perfectly colourless and
grateful vinegar rises in distillation. Its strength will be
proportionable to the concentration of the decomposing acid.
The acetic acid of the chemist may be prepared also in the following
modes:--1. Two parts of fused acetate of potash, with one of the
strongest oil of vitriol, yield, by slow distillation from a glass
retort into a refrigerated receiver, concentrated acetic acid. A small
portion of sulphurous acid, which contaminates it, may be removed by
redistillation from a little acetate of lead. 2. Or four parts of good
sugar of lead, with one part of sulphuric acid, treated in the same way,
afford a slightly weaker acetic acid. 3. Gently calcined sulphate of
iron, or green vitriol, mixed with sugar of lead, in the proportion of 1
of the former to 2-1/2 of the latter, or with acetate of copper, and
carefully distilled from a porcelain retort into a cool receiver, may be
also considered an economical process. But that with binacetate of
copper above described, is preferable to any of these.
[Illustration: _Fig._ 3.]
The manufacture of pyrolignous acid is conducted in the following way in
France. Into large cylindrical vessels (_fig._ 3.) made of rivetted
sheet iron, and having at their top and side a small sheet iron
cylinder, the wood intended for making charcoal is introduced. To the
upper part of this vessel a cover of sheet iron, B, is adapted, which is
fixed with bolts. This vessel, thus closed, represents, as we see, a
vast retort. When it is prepared, as we have said, it is lifted by means
of a swing crane, C, and placed in a furnace, D, (_fig._ 4.) of a form
relative to that of the vessel, and the opening of the furnace is
covered with a dome, E, made of masonry or brickwork. The whole being
thus arranged, heat is applied in the furnace at the bottom. The
moisture of the wood is first dissipated, but by degrees the liquor
ceases to be transparent, and becomes sooty. An adopter tube, A, is then
fitted to the lateral cylinder. This adopter enters into another tube at
the same degree of inclination which commences the condensing apparatus.
The means of condensation vary according to the localities. In certain
works they cool by means of air, by making the vapour pass through a
long series of cylinders, or sometimes, even, through a series of casks
connected together; but most usually water is used for condensing, when
it can be easily procured in abundance. The most simple apparatus
employed for this purpose consists of two cylinders, F, F, (_fig._ 4.)
the one within the other, and which leave between them a sufficient
space to allow a considerable body of water to circulate along and cool
the vapours. This double cylinder is adapted to the distilling vessel,
and placed at a certain inclination. To the first double tube, F, F, a
second, and sometimes a third, entirely similar, are connected, which,
to save space, return upon themselves in a zigzag fashion. The water is
set in circulation by an ingenious means now adopted in many different
manufactories. From the lower extremity, G, of the system of condensers,
a perpendicular tube rises, whose length should be a little more than
the most elevated point of the system. The water, furnished by a
reservoir, L, enters by means of the perpendicular tube through the
lower part of the system, and fills the whole space between the double
cylinders. When the apparatus is in action, the vapours, as they
condense, raise the temperature of the water, which, by the column in L
G, is pressed to the upper part of the cylinders, and runs over by the
spout K. To this point a very short tube is attached, which is bent
towards the ground, and serves as an overflow.
[Illustration: _Fig._ 4.]
The condensing apparatus is terminated by a conduit in bricks covered
and sunk in the ground. At the extremity of this species of gutter is a
bent tube, E, which discharges the liquid product into the first
cistern. When it is full, it empties itself, by means of an overflow
pipe, into a great reservoir; the tube which terminates the gutter
plunges into the liquid, and thus intercepts communication with the
inside of the apparatus. The disengaged gas is brought back by means of
pipes M L, from one of the sides of the conduit to the under part of the
ash pit of the furnace. These pipes are furnished with stopcocks M, at
some distance in front of the furnace, for the purpose of regulating the
jet of the gas, and interrupting, at pleasure, communication with the
inside of the apparatus. The part of the pipes which terminates in the
furnace rises perpendicularly several inches above the ground, and is
expanded like the rose of a watering can, N. The gas, by means of this
disposition, can distribute itself uniformly under the vessel, without
suffering the pipe which conducts it to be obstructed by the fuel or the
ashes.
The temperature necessary to effect the carbonisation is not
considerable: however, at the last it is raised so high as to make the
vessels red hot; and the duration of the process is necessarily
proportional to the quantity of wood carbonised. For a vessel which
shall contain about 5 meters cube (nearly 6 cubic yds.), 8 hours of fire
is sufficient. It is known that the carbonisation is complete by the
colour of the flame of the gas: it is first of a yellowish red; it
becomes afterwards blue, when more carbonic oxide than carbonic hydrogen
is evolved; and towards the end it becomes entirely white,--a
circumstance owing, probably, to the furnace being more heated at this
period, and the combustion being more complete. There is still another
means of knowing the state of the process, to which recourse is more
frequently had; that is the cooling of the first tubes, which are not
surrounded with water: a few drops of this fluid are thrown upon their
surface, and if they evaporate quietly, it is judged that the
calcination is sufficient. The adopter tube is then unluted, and is slid
into its junction pipe; the orifices are immediately stopped with plates
of iron and plaster loam. The brick cover, E, of the furnace is first
removed by means of the swing crane, then the cylinder itself is lifted
out and replaced immediately by another one previously charged. When the
cylinder which has been taken out of the furnace is entirely cooled, its
cover is removed, and the charcoal is emptied. Five cubic meters of wood
furnish about 7 chaldrons (voies) and a half of charcoal. (For
modifications of the wood-vinegar apparatus, see CHARCOAL and
PYROLIGNOUS ACID.)
The different qualities of wood employed in this operation give nearly
similar product in reference to the acid; but this is not the case with
the charcoal, for it is better the harder the wood; and it has been
remarked, that wood long exposed to the air furnishes a charcoal of a
worse quality than wood carbonised soon after it is cut.
Having described the kind of apparatus employed to obtain pyrolignous
acid, I shall now detail the best mode of purifying it. This acid has a
reddish brown colour; it holds in solution a portion of empyreumatic oil
and of the tar which were formed at the same time; another portion of
these products is in the state of a simple mixture; the latter may be
separated by repose alone. It is stated, above, that the distilling
apparatus terminates in a subterranean reservoir, where the products of
all the vessels are mixed. A common pump communicates with the
reservoir, and sinks to its very bottom, in order that it may draw off
only the stratum of tar, which, according to its greater density,
occupies the lower part. From time to time the pump is worked to remove
the tar as it is deposited. The reservoir has at its top an overflow
pipe, which discharges the clearest acid into a cistern, from which it
is taken by means of a second pump.
The pyrolignous acid thus separated from the undissolved tar is
transferred from this cistern into large sheet iron boilers, where its
saturation is effected either by quicklime or by chalk; the latter of
which is preferable, as the lime is apt to take some of the tar into
combination. The acid parts by saturation with a new portion of the tar,
which is removed by skimmers. The neutral solution is then allowed to
rest for a sufficient time to let its clear parts be drawn off by
decantation.
The acetate of lime thus obtained indicates by the hydrometer, before
being mixed with the waters of edulcoration, a degree corresponding to
the acidimetric degree of the acid employed. This solution must be
evaporated till it reaches a specific gravity of 1·114 (15° Baumé),
after which there is added to it a saturated solution of sulphate of
soda. The acids exchange bases; sulphate of lime precipitates, and
acetate of soda remains in solution. In some manufactures, instead of
pursuing the above plan, the sulphate of soda is dissolved in the hot
pyrolignous acid, which is afterwards saturated with chalk or lime. By
this means no water need be employed to dissolve the sulphate, and
accordingly the liquor is obtained in a concentrated form without
evaporation. In both modes the sulphate of lime is allowed to settle,
and the solution of acetate of soda is decanted. The residuum is set
aside to be edulcorated, and the last waters are employed for washing
fresh portions.
The acetate of soda which results from this double decomposition is
afterwards evaporated till it attains to the density of 1·225 or 1·23,
according to the season. This solution is poured into large
crystallising vessels, from which, at the end of 3 or 4 days, according
to their capacity, the mother waters are decanted, and a first
crystallisation is obtained of rhomboidal prisms, which are highly
coloured and very bulky. Their facettes are finely polished, and their
edges very sharp. The mother waters are submitted to successive
evaporations and crystallisations till they refuse to crystallise, and
they are then burnt to convert them into carbonate of soda.
To avoid guesswork proportions, which are always injurious, by the loss
of time which they occasion, and by the bad results to which they often
lead, we should determine experimentally, beforehand, the quantities
absolutely necessary for the reciprocal decomposition, especially when
we change the acid or the sulphate. But it may be remarked that,
notwithstanding all the precautions we can take, there is always a
notable quantity of sulphate of soda and acetic acid, which disappear
totally in this decomposition. This arises from the circumstance that
sulphate of soda and acetate of lime do not completely decompose each
other, as I have ascertained by experiments on a very considerable
scale; and thus a portion of each of them is always lost with the mother
waters. It might be supposed that by calcining the acetate of lime we
could completely destroy its empyreumatic oil; but, though I have made
many experiments, with this view I never could obtain an acetate capable
of affording a tolerable acid. Some manufacturers prefer to make the
acetate of soda by direct saturation of the acid with the alkali, and
think that the higher price of this substance is compensated by the
economy of time and fuel which it produces.
The acetate of soda is easily purified by crystallisations and
torrefaction; the latter process, when well conducted, freeing it
completely from every particle of tar. This torrefaction, to which the
name of fusion may be given, requires great care and dexterity. It is
usually done in shallow cast iron boilers of a hemispherical shape.
During all the time that the heat of about 500° Fahr. is applied, the
fused mass must be diligently worked with rakes; an operation which
continues about 24 hours for half a ton of materials. We must carefully
avoid raising the temperature so high as to decompose the acetate, and
be sure that the heat is equally distributed; for if any point of the
mass enters into decomposition, it is propagated with such rapidity, as
to be excessively difficult to stop its progress in destroying the
whole. The heat should never be so great as to disengage any smoke, even
when the whole acetate is liquefied. When there is no more frothing up,
and the mass flows like oil, the operation is finished. It is now
allowed to cool in a body, or it may be ladled out into moulds, which is
preferable.
When the acetate is dissolved in water, the charcoaly matter proceeding
from the decomposition of the tar must be separated by filtration, or by
boiling up the liquor to the specific gravity 1·114, when the
carbonaceous matter falls to the bottom. On evaporating the clear
liquor, we obtain an acetate perfectly fine, which yields beautiful
crystals on cooling. In this state of purity it is decomposed by
sulphuric acid, in order to separate its acetic acid.
This last operation, however simple it appears, requires no little care
and skill. The acetate of soda crystallised and ground is put into a
copper, and the necessary quantity of sulphuric acid of 1·842 (about 35
per cent. of the salt) to decompose almost, but not all, the acetate, is
poured on. The materials are left to act on each other; by degrees the
acetic acid quits its combination, and swims upon the surface; the
greater part of the resulting sulphate of soda falls in a pulverulent
form, or in small granular crystals, to the bottom. Another portion
remains dissolved in the liquid, which has a specific gravity of 1·08.
By distillation we separate this remainder of the sulphate, and finally
obtain acetic acid, having a specific gravity of 1·05, an agreeable
taste and smell, though towards the end it becomes a little
empyreumatic, and coloured; for which reason, the last portions must be
kept apart. The acid destined for table use ought to be distilled in an
alembic whose capital and condensing worm are of silver; and to make it
very fine, it may be afterwards infused over a little washed bone-black.
It is usually obtained in a pretty concentrated state; but when we wish
to give it the highest degree of concentration, we mix with it a
quantity of dry muriate of lime, and distil anew. This acid may be
afterwards exposed to congelation, when the strongest will crystallise.
It is decanted, and the crystals are melted by exposing them to a
temperature of from 60° to 70° Fahr.; this process is repeated till the
acid congeals without remainder, at the temperature of 55° Fahr. It has
then attained its maximum strength, and has a specific gravity of 1·063.
We shall add an observation on the above mode of decomposing the acetate
of soda by sulphuric acid. Many difficulties are experienced in this
process, if the sulphuric acid be poured on in small quantities at a
time; for then such acrid fumes of acetic acid are disengaged, that the
workmen are obliged to retire. This inconvenience may be saved by adding
all the sulphuric acid at once; it occupies the lower part of the
vessel, and decomposes only the portion of the acetate in contact with
it; the heat evolved in consequence of this reaction is diffused through
a great mass, and produces no sensible effect. When the sulphuric acid
forms an opening, or a species of little crater, the workman, by means
of a rake, depresses the acetate into it by degrees, and then the
decomposition proceeds as slowly as he desires.
The acetic acid, like the nitric, chloric, and some others, has not
hitherto been obtained free from water, and the greatest degree of
concentration which we have been able to give it is that in which it
contains only the quantity of water equivalent to the atomic weight of
another oxidized body; a quantity which amounts to 14·89 per cent. The
processes prescribed for preparing concentrated acetic acid sometimes
tend to deprive it of that water without which it could not exist:
hence, in all such cases, there is a part of the acid itself decomposed
to furnish the water necessary to the constitution of the remainder. The
constituent principles of the decomposed portion then form a peculiar,
intoxicating, highly inflammatory liquid, called the PYRO-ACETIC SPIRIT.
The most highly concentrated acid of 1·063 becomes denser by the
addition of a certain quantity of water up to a certain point. According
to Berzelius, the prime equivalent of this acid is 643·189, oxygen being
reckoned 100. Now, the above strongest acid consists of one prime of
acid, and one of water = 1124·79. When it contains three atoms of water,
that is, 337·437 parts to 643·189, or 34·41 to 65·59 in 100, it then has
taken its maximum density of 1·075; after which the further addition of
water diminishes its specific gravity, as the following table of
Mollerat shows. His supposed anhydrous or dry acid contains, at 1·0630,
0·114 parts of water.
_Table of Acetic Acid._
+----------+--------+
| Water in |Specific|
|100 parts.|gravity.|
+----------+--------+
| 0·00 | 1·0630 |
| 8·37 | 1·0742 |
| 17·00 | 1·0770 |
| 23·00 | 1·0791 |
| 28·10 | 1·0763 |
| 33·83 | 1·0742 |
| 37·60 | 1·0728 |
| 47·00 | 1·0658 |
| 50·00 | 1·0637 |
| 51·80 | 1·063 |
+----------+--------+
Acetic acid readily takes fire when it is heated in open vessels to the
boiling point, and it burns with a blue flame, nearly like alcohol. It
must be kept in close vessels, otherwise it loses its strength, by
attracting humidity from the air. When concentrated, it is used only as
a scent, or pungent exciter of the olfactory organs, in sickness and
fainting fits. Its anti-epidemic qualities are apocryphal. What is met
with in the shops under the name of salts of vinegar is nothing but
sulphate of potash, put up in small phials, and impregnated with acetic
acid, sometimes rendered aromatic with oil of rosemary or lavender.
Acetic acid, in its dry state, as it exists in fused acetate of potash
or soda, is composed of
47·536 carbon
5·822 hydrogen
46·642 oxygen
-------
100·000
And its symbol by Berzelius is H⁶ C⁴ O³ = A. We must bear in mind that
his atomic weight for hydrogen is only one half of the number usually
assigned to it by British chemists, in consequence of his making water a
compound of two atoms of hydrogen and one of oxygen.
When the vapour of acetic acid is made to traverse a red-hot tube of
iron, it is converted into water, carbonic acid, carburetted hydrogen,
but chiefly pyro-acetic spirit. Acetic acid is a solvent of several
organic products; such as camphor, gluten, gum-resins, resins, the
fibrine of blood, the white of egg, &c.
It is an important problem to ascertain the purity and strength of
vinegar. Spurious acidity is too often given to it by cheaper acids,
such as the sulphuric and the nitric. The former, may most surely be
detected by the nitrate of baryta, or even by acetate of lead, which
occasion a white precipitate in such adulterated vinegar. For the case
of nitric, which is more insidious, the proper test is, a bit of gold
leaf, wetted with a few drops of muriatic acid. If the leaf dissolves,
on heating the mixture in a watch glass, we may be sure that nitric acid
is present.
Specific gravity, if determined by a sensible hydrometer, is a good test
of the strength of the genuine vinegar; and the following table of
Messrs. Taylor is nearly correct, or sufficiently so for commercial
transactions.
Revenue proof vinegar, called by the English manufacturer No. 24., has a
specific gravity of
1·0085 and contains of real acid in 100-- 5
1·0170 10
1·0257 15
1·0320 20
1·0470 30
1·0580 40
An excise duty of 2_d._ is levied on every gallon of the above proof
vinegar. Its strength is not, however, estimated directly by its
specific gravity, but by the specific gravity which it assumes when
saturated with quicklime. The decimal fraction of the specific gravity
of the calcareous acetate is very nearly the double of that of the pure
vinegar; or, 1·009 in vinegar becomes 1·018 in acetate of lime. The
vinegar of malt contains so much mucilage or gluten, that when it has
only the same acid strength as the above, it has a density of 1·0014,
but it becomes only 1·023 when converted into acetate of lime: indeed,
0·005 of its density is due to mucilaginous matter. This fact shows the
fallacy of trusting to the hydrometer for determining the strength of
vinegars, which may be more or less loaded with vegetable gluten. The
proper test of this, as of all other acids, is, the quantity of alkaline
matter which a given weight or measure of it will saturate. For this
purpose the bicarbonate of potash, commonly called, in the London shops,
carbonate, may be employed very conveniently. As it is a very uniform
substance, and its atomic weight, by the hydrogen radix, is 100·584,
while the atomic weight of acetic acid, by the same radix, is 51·563, if
we estimate 2 grains of the bicarbonate as equivalent to 1 of the real
acid, we shall commit no appreciable error. Hence, a solution of the
carbonate containing 200 grains in 100 measures, will form an acetimeter
of the most perfect and convenient kind; for the measures of test liquid
expended in saturating any measure,--for instance, an ounce or 1000
grains of acid,--will indicate the number of grains of real acetic acid
in that quantity. Thus, 1000 grains of the above proof, would require 50
measures of the acetimetrical alkaline solution, showing that it
contains 50 grains of real acetic acid in 1000, or 5 per cent.
It is common to add to purified wood vinegar, a little acetic ether, or
caramelised (burnt) sugar to colour it, also, in France, even wine, to
flavour it. Its blanching effect upon red cabbage, which it has been
employed to pickle, is owing to a little sulphurous acid. This may be
removed by redistillation with peroxide of manganese. Indeed, Stoltze
professes to purify the pyrolignous acid solely by distilling it with
peroxide of manganese, and then digesting it with bruised wood charcoal;
or by distilling it with a mixture of sulphuric acid and manganese. But
much acid is lost in this case by the formation of acetate of that
metal.
Birch and beech afford most Pyrolignous acid, and pine the least. It is
exclusively employed in the arts, for most purposes of which it need not
be very highly purified. It is much used in calico printing, for
preparing acetate of iron called IRON LIQUOR, and acetate of alumina,
called RED LIQUOR; which see. It serves also to make sugar of lead; yet
when it contains its usual quantity, after rectification, of tarry
matter, the acetate of lead will hardly crystallise, but forms
cauliflower concretions. This evil may be remedied, I believe, by
boiling the saline solution with a very little nitric acid, which causes
the precipitation of a brown granular substance, and gives the liquor a
reddish tinge. The solution being afterwards treated with bruised
charcoal, becomes colourless, and furnishes regular crystals of acetate
or sugar of lead.
Pyrolignous acid possesses, in a very eminent degree, anti-putrescent
properties. Flesh steeped in it for a few hours may be afterwards dried
in the air without corrupting; but it becomes hard, and somewhat
leather-like: so that this mode of preservation does not answer well for
butcher’s meat. Fish are sometimes cured with it. See PYRO-ACETIC
SPIRIT; PYROXILIC ETHER; PYROXOLIC SPIRIT; PYROLIGNOUS ACID and
VINEGAR.
ACETIMETER. An apparatus for determining the strength of vinegar. See
the conclusion of the preceding article for a description of my simple
method of acetimetry.
ACETONE. The new chemical name of pyro-acetic spirit.
ACID OF ARSENIC. (_Acide Arsenique_, Fr.; _Arseniksäure_, Germ.)
ACIDS. A class of chemical substances characterised by the property of
combining with and neutralising the alkaline and other bases, and of
thereby forming a peculiar class of bodies called salts. The acids which
constitute objects of special manufacture for commercial purposes are
the following:--acetic, arsenious, carbonic, chromic, citric, malic,
muriatic, nitric, oxalic, phosphoric, sulphuric, tartaric, which see.
ACROSPIRE. (_Plumule_, Fr.; _Blattkeim_, Germ.) That part of a
germinating seed which botanists call the plumula, or plumes. See BEER
and MALT.
ADDITIONS. Such articles as are added to the fermenting wash of the
distiller are distinguished by this trivial name.
ADIPOCIRE. Fr. (_Fettwachs_, Germ.) The fatty matter generated in dead
bodies buried under peculiar circumstances. In 1786 and 1787, when the
churchyard of the _Innocents_, at Paris, was cleaned out, and the bones
transported to the catacombs, it was discovered that not a few of the
_cadavres_ were converted into a saponaceous white substance, more
especially many of those which had been interred for fifteen years in
one pit, to the amount of 1500, in coffins closely packed together.
These bodies were flattened, in consequence of their mutual pressure;
and, though they generally retained their shape, there was deposited
round the bones of several a grayish white, somewhat soft, flexible
substance. Fourcroy presented to the Academy of Sciences, in 1789, a
comprehensive memoir upon this phenomenon, which appeared to prove that
the fatty body was an ammoniacal soap, containing phosphate of lime;
that the fat was similar to spermaceti, as it assumed on slow cooling a
foliated crystalline structure; as also to wax, as, when rapidly cooled,
it became granular: hence he called it _Adipocire_. Its melting point
was 52·5° C. (126·5° Fahr.). He likewise compared this soap to the fat
of gall-stones, and supposed it to be a natural product of the slow
decomposition of all animal matter, except bones, nails, and hairs.
This substance was again examined by Chevreul in 1812, and was found by
him to contain margaric acid, oleic acid, combined with a yellow
colouring, odorous matter, besides ammonia, a little lime, potash, oxide
of iron, salts of lactic acid, an azotized substance; and was therefore
considered as a combination of margaric and oleic acids, in variable
proportions (whence arose its variable fusibility), but that it was not
analogous with either spermaceti or cholesterine (gallstones). These fat
acids are obviously generated by the reaction of the ammonia upon the
margarine and oleine, though they eventually lose the greater part of
that volatile alkali.
According to the views of both Gay Lussac and Chevreul, this _adipocire_
proceeds solely from the pre-existing fat of the dead body, and not from
the flesh, tendons, or cartilages, as had been previously imagined;
which had led to some expensive and abortive attempts, upon the great
scale of manufacture, to convert the dead bodies of cattle into
adipocire, for the purposes of the candle-maker or soap-boiler, by
exposing them for some time to the action of moisture.
Von Hartkol made experiments during 25 years upon this subject, from
which he inferred, that there is no formation of adipocire in bodies
buried in dry ground; that in moist earth the fat of the dead body does
not increase, but changes into a fetid saponaceous substance, incapable
of being worked into either soap or candles; that the dead bodies of
_mammalia_ immersed in running water, leave behind after 3 years a pure
fat, which is more abundant from young than from old animals; that the
intestines afford more fat than the muscles; that from this fat, without
any purification, candles may be made, as void of smell, as hard, and as
white, as from bleached wax; that from cadavers immersed for 3 years in
stagnant water, more fat is procured than from those in running water,
but that it needs to be purified before it can be made into soap or
candles.
The cause of the difference between Hartkol’s and Chevreul’s results
cannot be assigned, as the latter has not published his promised remarks
upon the subject. At any rate, dead animal matter can be worked up more
profitably than in making artificial _adipocire_.
ADIT. The horizontal entrance of a mine. It is sometimes called the
drift. See MINING and METALLURGY.
ADULTERATION. The debasing any product of manufacture, especially
chemical, by the introduction of cheap materials. The art of
ascertaining the genuineness of the several products will be taught
under the specific objects of manufacture.
ÆTHER. See ETHER.
AFFINITY. The chemical term denoting the peculiar attractive force which
produces the combination of dissimilar substances; such as of an alkali
with an acid, or of sulphur with a metal.
AGARIC. A species of boletus or fungus, which grows in dunghills; with
the salts of iron it affords a black dye. It is said to be convertible
into a kind of china ink.
AGATE. A siliceous mineral which is cut into seals and other forms for
the coarser kinds of jewellery. See GEM.
AIR. See VENTILATION.
ALABASTER, is a stone usually white, and soft enough to be scratched by
iron. There are two kinds of it: the gypseous, which is merely a natural
semi-crystalline sulphate of lime; and the calcareous alabaster, which
is a carbonate of lime. The oriental alabaster is always of the latter
kind, and is most esteemed, because it is agreeably variegated with
lively colours, and especially with zones of honey-yellow, yellow-brown,
red, &c.; it is, moreover, susceptible of taking a marble polish.
The fineness of the grain of alabaster, the uniformity of its texture,
the beauty of its polished surface, and its semi-transparency, are the
qualities which render it valuable to the sculptor and to the
manufacturer of ornamental toys.
The limestone alabaster is frequently found as a yellowish-white deposit
in certain fountains. The most celebrated spring of this kind is that of
the baths of San Filippo, in Tuscany. The water, almost boiling hot,
runs over an enormous mass of stalactites, which it has formed, and
holds the carbonate of lime in solution by means of sulphuretted
hydrogen (according to M. Alexandre Brongniart), which escapes by
contact of the atmosphere. Advantage has been taken of this property to
make _basso relievos_ of considerable hardness, by placing moulds of
sulphur very obliquely, or almost upright, in wooden tubs open at the
bottom. These tubs are surmounted at the top with a large wooden cross.
The water of the spring, after having deposited in an external conduit
or cistern the coarser sediment, is made to flow upon this wooden cross,
where it is scattered into little streamlets, and thence lets fall, upon
the sulphur casts, a precipitate so much the finer the more nearly
vertical the mould. From one to four months are required for this
operation, according to the thickness of the deposited crust. By
analogous processes, the artists have succeeded in moulding vases,
figures of animals, and other objects, in relief, of every different
form, which require only to be trimmed a little, and afterwards
polished.
The common alabaster is composed of sulphuric acid and lime, though some
kinds of it effervesce with acids, and therefore contain some carbonate
of lime. This alabaster occurs in many different colours, and of very
different degrees of hardness, but it is always softer than marble. It
forms, usually, the lowest beds of the gypsum quarries. The sculptors
prefer the hardest, the whitest, and those of a granular texture, like
Carrara marble, and so like that they can only be distinguished by the
hardness.
The alabaster is worked with the same tools as marble; and as it is many
degrees softer, it is so much the more easily cut; but it is more
difficult to polish, from its little solidity. After it has been
fashioned into the desired form, and smoothed down with pumice stone, it
is polished with a pap-like mixture of chalk, soap, and milk; and, last
of all, finished by friction with flannel. It is apt to acquire a
yellowish tinge.
Besides the harder kinds, employed for the sculpture of large figures,
there is a softer alabaster, pure white and semi-transparent, from which
small ornamental objects are made, such as boxes, vases, lamps, stands
of time-pieces, &c. This branch of business is much prosecuted in
Florence, Leghorn, Milan, &c., and employs a great many turning lathes.
Of all the alabasters the Florentine merits the preference, on account
of its beauty and uniformity, so that it may be fashioned into figures
of considerable size; for which purpose there are large work-shops where
it is cut with steel saws into blocks and masses of various shapes.
Other sorts of gypsum, such as that of Salzburg and Austria, contain
sand veins, and hard nodules, and require to be quarried by cleaving and
blasting operations, which are apt to crack it, and unfit it for all
delicate objects of sculpture. It is, besides, of a gray shade, and
often stained with darker colours.
The alabaster best adapted for the fine arts is pretty white when newly
broken, and becomes whiter on the surface by drying. It may be easily
cut with the knife or chisel, and formed into many pleasing shapes by
suitable steel tools. It is worked either by the hand alone, or with the
aid of a turning lathe. The turning tools should not be too thin or
sharp-edged; but such as are employed for ivory and brass are most
suitable for alabaster, and are chiefly used to shave and to scratch the
surface. The objects which cannot be turned may be fashioned by the
rasping tools, or with minute files, such as variegated foliage. Fine
chisels and graving tools are also used for the better pieces of
statuary.
For polishing such works, a peculiar process is required: pumice stone,
in fine powder, serves to smooth down the surfaces very well, but it
soils the whiteness of the alabaster. To take away the unevennesses and
roughnesses dried shave-grass (_equisetum_) answers best. Frictions with
this plant and water polish down the asperities left by the chisel: the
fine streaks left by the grass may be removed by rubbing the pieces with
slaked lime, finely pulverised and sifted, made into a paste, or putty,
with water. The polish and satin-lustre of the surface are communicated
by friction, first with soap-water and lime, and finally with powdered
and elutriated talc or French chalk.
Such articles as consist of several pieces are joined by a cement
composed of quicklime and white of egg, or of well-calcined and
well-sifted Paris plaster, mixed with the least possible quantity of
water.
Alabaster objects are liable to become yellow by keeping, and are
especially injured by smoke, dust, &c. They may be in some measure
restored by washing with soap and water, then with clear water, and
again polished with shave-grass. Grease spots may be removed either by
rubbing with talc powder, or with oil of turpentine.
The surface of alabaster may be etched by covering over the parts that
are not to be touched with a solution of wax in oil of turpentine,
thickened with white lead, and immersing the articles in pure water
after the varnish has set. The action of the water is continued from 20
to 50 hours, more or less, according to the depth to which the etching
is to be cut. After removing the varnish with oil of turpentine, the
etched places, which are necessarily deprived of their polish, should be
rubbed with a brush dipped in finely-powdered gypsum, which gives a kind
of opacity, contrasting well with the rest of the surface.
Alabaster may be stained either with metallic solutions, with spirituous
tinctures of dyeing plants, or with coloured oils, in the same way as
marbles.
This substance has been hardened, it is said, by exposing it to the heat
of a baker’s oven for 10 or 20 hours, after taking it out of the quarry,
and giving it the figure, roughly, which it is intended to have. After
this exposure, it must be dipped for two minutes in running water; when
it is cold, it must be dipped a second time for the same period. On
being exposed to the air for a few days, alabaster so treated acquires a
marble-like hardness. I doubt the truth of this statement.
ALBUM GRÆCUM. The white dung of dogs, sometimes used to soften leather
in the process of dressing it after the depilatory action of lime.
ALCARAZZAS. A species of porous earthenware, made in Spain, for cooling
liquors. See POTTERY.
ALCOHOL. The well-known intoxicating liquor procured by distillation
from various vegetable juices, and infusions of a saccharine nature,
which have undergone the vinous fermentation. Common alcohol, or proof
spirit, as it is called, contains about one half its weight of water. It
may be concentrated till its specific gravity becomes so low as 0·825,
by simple redistillation at a steam or water-bath heat; but to make it
stronger, we must mix with it, in the still or retort, dry carbonate of
potash, muriate of lime, or some other substances strongly attractive of
water, and then it may be obtained of a specific gravity so low as 0·791
at 16° Reaumur (68° Fahr.), water being 1·000. At 0·825, it contains,
still, 11 per cent. of water; and in this state it is as volatile as
absolute alcohol, on account of the inferior density of the aqueous
vapour, compared to the alcoholic. Indeed, according to Yelin and Fuchs,
the boiling point of anhydrous alcohol is higher than of that which
contains 2 or 3 per cent. of water; hence, in the distillation of
alcohol of 94 per cent., the first portions that come over are more
aqueous than the following. Absolute alcohol has its boiling point at
168-1/2° Fahr.: but when it holds more than 6 per cent. of water, the
first portions that come over are richest in alcohol, and the
temperature of the boiling point, or of the spirituous vapour, is always
higher the longer the distillation continues. According to Gröning’s
researches, the following temperatures of the alcoholic vapours
correspond to the accompanying contents of alcohol in per centage of
volume, which are disengaged in the boiling of the spirituous liquid.
+------------+-----------+-----------+
| |Alcoholic |Alcoholic |
|Temperature.|content of |content of |
| |the vapour.|the boiling|
| | |liquid. |
+------------+-----------+-----------+
|Fahr. 170·0 | 93 | 92 |
| 171·8 | 92 | 90 |
| 172 | 91 | 85 |
| 172·8 | 90-1/2 | 80 |
| 174 | 90 | 70 |
| 174·6 | 89 | 70 |
| 176 | 87 | 65 |
| 178·3 | 85 | 50 |
| 180·8 | 82 | 40 |
| 183 | 80 | 35 |
| 185 | 78 | 30 |
| 187·4 | 76 | 25 |
| 189·8 | 71 | 20 |
| 192·0 | 68 | 18 |
| 164 | 66 | 15 |
| 196·4 | 61 | 12 |
| 198·6 | 55 | 10 |
| 201 | 50 | 7 |
| 203 | 42 | 5 |
| 205·4 | 36 | 3 |
| 207·7 | 28 | 2 |
| 210 | 13 | 1 |
| 212 | 0 | 0 |
+------------+-----------+-----------+
Gröning undertook this investigation in order to employ the thermometer
as an alcoholmeter in the distillation of spirits; for which purpose he
thrust the bulb of the thermometer through a cork, inserted into a tube
fixed in the capital of the still. The state of the barometer ought also
to be considered in making comparative experiments of this kind. Since,
by this method, the alcoholic content may be compared with the
temperature of the vapour that passes over at any time, so, also, the
contents of the whole distillation may be found approximately; and the
method serves as a convenient means of making continual observations on
the progress of the distillation.
The temperature, corresponding to a certain per centage of alcohol in
vapour, suggests the employment of a convenient method for obtaining, at
one process, a spirit as free from water as it can be made by mere
distillation. We place over the top of the capital a water-bath, and
lead up through it a spiral pipe from the still, which there passes
obliquely downwards, and proceeds to the refrigeratory. If this bath be
maintained, by a constant influx of cold water, at a certain
temperature, only the alcoholic vapour corresponding to that temperature
will pass over, and the rest will be recondensed and returned into the
still. If we keep the temperature of the water at 174°, for example, the
spirituous vapour which passes over will contain 90 per cent. of
absolute alcohol, according to the preceding table. The skilful use of
this principle constitutes the main improvement in modern distilleries.
See DISTILLATION and STILL.
Another method for concentrating alcohol is that discovered by
Sömmering, founded upon the property of ox bladders to allow water to
pass through and evaporate out of them, but not to permit alcohol to
transpire, or only in a slight degree. Hence, if an ox’s bladder is
filled with spirit of wine, well tied at the mouth, and suspended in a
warm place, the water will continually exhale, and the alcohol will
become nearly anhydrous; for in this way alcohol of 97 or 98 per cent.
may be obtained.
According to Sömmering, we should take for this purpose the bladder of
an ox or a calf, soak it for some time in water, then inflate it and
free it from the fat and the attached vessels; which is to be also done
to the other surface, by turning it inside out. After it is again
inflated and dried, we must smear over the outer side twice, and the
inner side four times, with a solution of isinglass, by which its
texture is made closer, and the concentration of the alcohol goes on
better. A bladder so prepared may serve more than a hundred times. It
must be charged with the spirits to be concentrated, leaving a small
space vacant, it is then to be tightly bound at the mouth, and suspended
in a warm situation, at a temperature of 122° Fahr., over a sand-bath,
or in the neighbourhood of an oven. The surface of the bladder remains
moist with the water, as long as the sp. gr. of the contained spirit is
greater than 0·952. Weak spirit loses its water quicker than strong; but
in from 6 to 12 hours the alcohol may be concentrated, when a suitable
heat is employed. This economical method is particularly applicable in
obtaining alcohol for the preparation of varnishes. When the alcohol is
to serve for other purposes, it must be freed, by distillation, from
certain matters dissolved out of the bladder. Alcohol may likewise be
strengthened, as Sömmering has ascertained when the vessel that contains
the spirit is bound over with a bladder which does not come into contact
with the liquid. Thus, too, all other liquors containing alcohol and
water, as wine, cider, &c., may be made more spirituous.
To procure absolute alcohol, we must take chloride of calcium recently
fused, reduce it to coarse powder, and mix it with its own weight of
spirit of wine, of sp. gr. 0·833, in a bottle, which is to be well
stoppered, and to be agitated till the salt is dissolved. The clear
solution is to be poured into a retort, and half of the volume of the
alcohol employed, or so much as has the sp. gr. 0·791 at 68° Fahr., is
to be distilled off at a gentle heat. Quicklime has also been employed
for the same purpose, but it is less powerful and convenient. Alcohol,
nearly free from water, may be obtained without distillation, by adding
dry carbonate of potash to a spirit of wine, of sp. gr. 0·825. The water
combines with the potash, and falls to the bottom in a dense liquid,
while the pure spirit floats on the surface. This contains however a
little alkali, which can only be separated by distillation.
Anhydrous alcohol is composed by weight of 52·66 carbon, 12·90 hydrogen,
and 34·44 of oxygen. It has a very powerful attraction for water, and
absorbs it from the atmosphere; therefore it must be kept in well-closed
vessels. It also robs vegetable and animal bodies of their moisture; and
hence common alcohol is employed for preserving anatomical preparations.
Alcohol is a solvent for many substances: resins, essential oils,
camphor, are abundantly dissolved by it, forming varnishes, perfumed
spirits, &c. The solution of a resin or essential oil in alcohol becomes
milky on the addition of water, which, by its attraction for alcohol,
separates these substances. Several salts, especially the deliquescent,
are dissolved by it, and some of them give a colour to its flame; thus,
the solutions of the salts of strontia in alcohol burn with a crimson
flame, those of copper and borax green, lime reddish, and baryta yellow.
When water is mixed with alcohol, heat and a condensation of volume are
the result; these effects being greatest with 54 per cent. of alcohol
and 46 of water, and thence decreasing with a greater proportion of
water. For alcohol which contains 90 per cent. of water, this
condensation amounts to 1·94 per cent. of the volume; for 80 per cent.,
2·87; for 70 per cent., 3·44; for 60 per cent., 3·73; for 40 per cent.,
3·44; for 30 per cent., 2·72; for 20 per cent., 1·72; for 10 per cent.,
0·72. Hence, to estimate the quantity of alcohol in any spirit it is
necessary that the specific gravity be ascertained for each determinate
proportion of alcohol and water that are mixed together. When this is
done, we may, by means of an areometer constructed for liquids lighter
than water, determine the strength of the spirit, either by a scale of
specific gravities or by an arbitrary graduation corresponding to
certain commercial objects, and thus we may determine the per centage of
alcohol in whisky or brandy of any strength or purity. An areometer
intended for this use has been called an alcoholmeter, in particular
when the scale of it is so graduated that, instead of the specific
gravity, it indicates immediately the per centage of anhydrous alcohol
in a given weight or volume of the liquid. The scale graduated according
to the per centage of pure alcohol by weight, constitutes the
alcoholmeter of Richter; and that by the per centage in volume, the
alcoholmeter of Tralles and Gay Lussac.
As liquors are sold in general by the measure, not by the weight, it is
convenient, therefore, to know the alcoholic content of the mixtures in
the per centage by volume. Tralles has constructed new tables upon the
principles of those of Gilpin, in which the proportion is given by
volume, and anhydrous alcohol is assumed for the basis; which, at 60°
Fahr., has a specific gravity of 0·7939 compared with water at its
maximum density, or a specific gravity 0·7946 compared with water of the
temperature of 60° Fahr. Gilpin’s alcohol of 0·825 contains 92·6 per
cent. by volume of anhydrous alcohol.
The following table exhibits the per centage of anhydrous alcohol by
volume, at a temperature of 60° Fahr., in correspondence with the
specific gravities of the spirits, water being considered at 60° Fahr.
to have a specific gravity of 0·9991.
Alcoholmetrical Table of Tralles.
+------------+------------+----------+
|Alcohol in | Specific |Difference|
|100 measures| gravity | of the |
| of spirit. |at 60° Fahr.| sp. gr. |
+------------+------------+----------+
| 0 | 9991 | |
| 1 | 9976 | 15 |
| 2 | 9961 | 15 |
| 3 | 9947 | 14 |
| 4 | 9933 | 14 |
| 5 | 9919 | 14 |
| 6 | 9906 | 13 |
| 7 | 9893 | 13 |
| 8 | 9881 | 12 |
| 9 | 9869 | 12 |
| 10 | 9857 | 12 |
| 11 | 9845 | 12 |
| 12 | 9834 | 11 |
| 13 | 9823 | 11 |
| 14 | 9812 | 11 |
| 15 | 9802 | 10 |
| 16 | 9791 | 11 |
| 17 | 9781 | 10 |
| 18 | 9771 | 10 |
| 19 | 9761 | 10 |
| 20 | 9751 | 10 |
| 21 | 9741 | 10 |
| 22 | 9731 | 10 |
| 23 | 9720 | 11 |
| 24 | 9710 | 10 |
| 25 | 9700 | 10 |
| 26 | 9689 | 11 |
| 27 | 9679 | 10 |
| 28 | 9668 | 11 |
| 29 | 9657 | 11 |
| 30 | 9646 | 11 |
| 31 | 9634 | 12 |
| 32 | 9622 | 12 |
| 33 | 9609 | 13 |
| 34 | 9596 | 13 |
| 35 | 9583 | 13 |
| 36 | 9570 | 13 |
| 37 | 9556 | 14 |
| 38 | 9541 | 15 |
| 39 | 9526 | 15 |
| 40 | 9510 | 16 |
| 41 | 9494 | 16 |
| 42 | 9478 | 16 |
| 43 | 9461 | 17 |
| 44 | 9444 | 17 |
| 45 | 9427 | 17 |
| 46 | 9409 | 18 |
| 47 | 9391 | 18 |
| 48 | 9373 | 18 |
| 49 | 9354 | 19 |
| 50 | 9335 | 19 |
| 51 | 9315 | 20 |
| 52 | 9295 | 20 |
| 53 | 9275 | 20 |
| 54 | 9254 | 21 |
| 55 | 9234 | 20 |
| 56 | 9213 | 21 |
| 57 | 9192 | 21 |
| 58 | 9170 | 22 |
| 59 | 9148 | 22 |
| 60 | 9126 | 22 |
| 61 | 9104 | 22 |
| 62 | 9082 | 22 |
| 63 | 9059 | 23 |
| 64 | 9036 | 23 |
| 65 | 9013 | 23 |
| 66 | 8989 | 24 |
| 67 | 8965 | 24 |
| 68 | 8941 | 24 |
| 69 | 8917 | 24 |
| 70 | 8892 | 25 |
| 71 | 8867 | 25 |
| 72 | 8842 | 25 |
| 73 | 8817 | 25 |
| 74 | 8791 | 26 |
| 75 | 8765 | 26 |
| 76 | 8739 | 26 |
| 77 | 8712 | 27 |
| 78 | 8685 | 27 |
| 79 | 8658 | 27 |
| 80 | 8631 | 27 |
| 81 | 8603 | 28 |
| 82 | 8575 | 28 |
| 83 | 8547 | 28 |
| 84 | 8518 | 29 |
| 85 | 8488 | 30 |
| 86 | 8458 | 30 |
| 87 | 8428 | 30 |
| 88 | 8397 | 31 |
| 89 | 8365 | 32 |
| 90 | 8332 | 33 |
| 91 | 8299 | 33 |
| 92 | 8265 | 34 |
| 93 | 8230 | 35 |
| 94 | 8194 | 36 |
| 95 | 8157 | 37 |
| 96 | 8118 | 39 |
| 97 | 8077 | 41 |
| 98 | 8034 | 43 |
| 99 | 7988 | 46 |
| 100 | 7939 | 49 |
+------------+------------+----------+
_Remarks on the preceding Table of Alcohol._
The third column of this table exhibits the differences of the specific
gravities, which give the denominator of the fraction for such densities
as are not found sufficiently near in the table; and the difference of
their numerators is the next greatest to the density found in the table.
For example: if the specific gravity of the liquor found for 60° Fahr. =
9605 (the per centage will be between 33 and 34), the difference from
9609 (which is the next greatest number in the table) = 4, and the
fraction is 4/13; therefore the true per centage is 33-4/13. From the
construction of this table the per centage of alcohol by weight may also
be found. For instance: we multiply the number representing the
_volumes_ of alcohol (given in the table for any determinate specific
gravity of the mixture) by the specific gravity of the pure alcohol,
that is, by 7939, and the product is the number of pounds of alcohol in
so many pounds as the specific gravity multiplied by 100 gives. Thus, in
the mixture of 9510 specific gravity, there are 40 measures of alcohol;
hence there are also in 95,100 pounds of this spirit 7939 + 40 = 31·756
pounds of alcohol; and in 100 pounds of the spirits of 0·9510 specific
gravity, 33·39 pounds of alcohol are contained.
As the preceding table gives the true alcoholic content when the portion
of spirit under trial has the normal temperature of 60° Fahr., the
following table gives the per centage of alcohol for the specific
gravities corresponding to the accompanying temperatures.
For example: if we have a spirituous liquor at 80° Fahr., whose specific
gravity is 0·9342, the alcohol present is 45 per cent. of the volume, or
that specific gravity at that temperature is equal to the specific
gravity 0·9427 at the normal temperature of 60° Fahr. This table may
also be employed for every degree of the thermometer and every per
centage, so as to save computation for the intervals. It is evident from
inspection that a difference of 5° Fahr. in the temperature changes the
specific gravity of the liquor by a difference nearly equal to 1 volume
per cent. of alcohol; thus at 35° and 85° Fahr. the very same specific
gravity of the liquor shows nearly 10 volumes per cent. of alcohol more
or less; the same, for example, at 60 and 40 per cent.
+-------+-----------------------------------------------------------+
|Alcohol| Temperature. |
| per +----+----+----+----+----+----+----+----+----+----+----+----+
| cent. | 30°| 35°| 40°| 45°| 50°| 55°| 60°| 65°| 70°| 75°| 80°| 85°|
| | F.| F.| F.| F.| F.| F.| F.| F.| F.| F.| F.| F.|
+-------+----+----+----+----+----+----+----+----+----+----+----+----+
| 0 |9994|9997|9997|9998|9997|9994|9991|9987|9991|9976|9970|9962|
| 5 |9924|9926|9926|9926|9925|9922|9919|9915|9909|9903|9897|9889|
| 10 |9868|9869|9868|9867|9865|9861|9857|9852|9845|9839|9831|9823|
| 15 |9823|9822|9820|9817|9813|9807|9802|9796|9788|9779|9771|9761|
| 20 |9786|9782|9777|9772|9766|9759|9751|9743|9733|9722|9711|9700|
| 25 |9753|9746|9738|9729|9720|9709|9700|9690|9678|9665|9652|9638|
| 30 |9717|9707|9695|9684|9672|9659|9646|9632|9618|9603|9588|9572|
| 35 |9671|9658|9644|9629|9614|9599|9583|9566|9549|9532|9514|9495|
| 40 |9615|9598|9581|9563|9546|9528|9510|9491|9472|9452|9433|9412|
| 45 |9544|9525|9506|9486|9467|9447|9427|9406|9385|9364|9342|9320|
| 50 |9460|9440|9420|9399|9378|9356|9335|9313|9290|9267|9244|9221|
| 55 |9368|9347|9325|9302|9279|9256|9234|9211|9187|9163|9139|9114|
| 60 |9267|9245|9222|9198|9174|9150|9126|9102|9076|9051|9026|9000|
| 65 |9162|9138|9113|9088|9063|9038|9013|8988|8962|8936|8909|8882|
| 70 |9046|9021|8996|8970|8944|8917|8892|8866|8839|8812|8784|8756|
| 75 |8925|8899|8873|8847|8820|8792|8765|8738|8710|8681|8652|8622|
| 80 |8798|8771|8744|8716|8688|8659|8631|8602|8573|8544|8514|8483|
| 85 |8663|8635|8606|8577|8547|8517|8488|8458|8427|8396|8365|8333|
| 90 |8517|8486|8455|8425|8395|8363|8322|8300|8268|8236|8204|8171|
+-------+----+----+----+----+----+----+----+----+----+----+----+----+
The importance of extreme accuracy in determining the density of
alcoholic mixtures in the United Kingdom, on account of the great
revenue derived from them to the State, and their consequent high price
in commerce, induced the Lords of the Treasury a few years ago to
request the Royal Society to examine the construction and mode of
applying the instrument now in use for ascertaining and charging the
duty on spirits. This instrument, which is known and described in the
law as Sikes’s hydrometer, possesses, in many respects, decided
advantages over those formerly in use. The committee of the Royal
Society state, that a definite mixture of alcohol and water is as
invariable in its value as absolute alcohol can be; and can be more
readily, and with equal accuracy, identified by that only quality or
condition to which recourse can be had in practice, namely, specific
gravity. The committee further proposed, that the standard spirit be
that which, consisting of alcohol and water alone, shall have a specific
gravity of 0·92 at the temperature of 62° Fahr., water being unity at
the same temperature; or, in other words, that it shall at 62° weigh
92/100 or 23/25 of an equal bulk of water at the same temperature.
This standard is rather weaker than the old proof, which was 12/13, or
0·923; or in the proportion of nearly 1·1 gallon of the present proof
spirit per cent. The proposed standard will contain nearly one half by
weight of absolute alcohol. The hydrometer ought to be so graduated as
to give the indication of strength; not upon an arbitrary scale, but in
terms of specific gravity at the temperature of 62°.
The committee recommend the construction of an equation table, which
shall indicate the same strength of spirit at every temperature. Thus in
standard spirit at 62° the hydrometer would indicate 920, which in this
table would give proof spirit. If that same spirit were cooled to 40°,
the hydrometer would indicate some higher number; but which, being
combined in the table with the temperature as indicated by the
thermometer, should still give proof or standard spirit as the result.
It is considered advisable, in this and the other tables, not to express
the quality of the spirit by any number over or under proof, but to
indicate at once the number of gallons of standard spirit contained in,
or equivalent to, 100 gallons of the spirit under examination. Thus,
instead of saying 23 over proof, it is proposed to insert 123; and in
place of 35·4 under proof, to insert its difference to 100, or 64·6.
It has been considered expedient to recommend a second table to be
constructed, so as to show the bulk of spirit of any strength at any
temperature, relative to a standard bulk of 100 gallons at 62°. In this
table a spirit which had diminished in volume, at any given temperature,
0·7 per cent., for example, would be expressed by 99·3; and a spirit
which had increased at any given temperature 0·7 per cent., by 100·7.
When a sample of spirit, therefore, has been examined by the hydrometer
and thermometer, these tables will give first the proportion of standard
spirit at the observed temperature, and next the change of bulk of such
spirit from what it would be at the standard temperature. Thus, at the
temperature of 51°, and with an indication (sp. gr.) of 8240, 100
gallons of the spirit under examination would be shown by the first
table to be equal to 164·8 gallons of standard spirit of that
temperature; and by the second table it would appear that 99·3 gallons
of the same spirit would become 100 at 62°, or in reality contain the
164·8 gallons of spirit in that state only in which it is to be taxed.
But as it is considered that neither of these tables can alone be used
for charging the duty (for neither can express the actual quantity of
spirit of a specific gravity of 0·92 at 62° in 100 gallons of stronger
or weaker spirit at temperatures above or below 62°), it is considered
essential to have a third table, combining the two former, and
expressing this relation directly, so that upon mere inspection it shall
indicate the proportion of standard spirit in 100 gallons of that under
examination in its then present state. In this table the quantities
should be set down in the actual number of gallons of standard spirit at
62°, equivalent to 100 of the spirit under examination; and the column
of quantities may be expressed by the term _value_, as it in reality
expresses the proportion of the only valuable substance present. As this
will be the only table absolutely necessary to be used with the
instrument for the purposes of the excise, it may, perhaps, be thought
unnecessary to print the former two.
The following specimen table has been given by the committee:--
+-------------------------------++----------------------------+
| Temperature 45°. || Temperature 75°. |
+--------------+---------+------++-----------+---------+------+
|Indication.[3]|Strength.|Value.||Indication.|Strength.|Value.|
+--------------+---------+------++-----------+---------+------+
| 9074 | 114·5 | || 8941 | 114·5 | |
| 7 | 114·3 | || 4 | 114·3 | |
| 9 | 114·2 | || 5 | 114·2 | |
| 81 | 114·0 | || 8 | 114·0 | |
| 3 | 113·9 | || 9 | 113·9 | |
| 5 | 113·7 | || 52 | 113·7 | |
| 6 | 113·6 | || 3 | 113·6 | |
| 9 | 113·4 | || 6 | 113·4 | |
| 90 | 113·3 | || 7 | 113·3 | |
| 3 | 113·1 | || 9 | 113·1 | |
+--------------+---------+------++-----------+---------+------+
[3] By specific gravity.
The mixture of alcohol and water, taken as spirit in Mr. Gilpin’s
tables, is that of which the specific gravity is 0·825 at 60° Fahr.,
water being unity at the same temperature. The specific gravity of water
at 60° being 1000, at 62° it is 99,981. Hence, in order to compare the
specific gravities given by Mr. Gilpin with those which would result
when the specific gravity of water at 62° is taken at unity, all the
former numbers must be divided by 99,981.
Table of the Specific Gravities of different Mixtures, by Weight, of
Alcohol and Water, at different Temperatures; constructed by Mr. Gilpin,
for the use of the British Revenue on Spirits.
+------+-------+-------+-------+-------+-------+-------+-------+
|Tem- | Pure | 100 | 100 | 100 | 100 | 100 | 100 |
|pera- | Alco- |Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|
|ture, | hol. | 5 | 10 | 15 | 20 | 25 | 30 |
|Fahr. | | Water.| Water.| Water.| Water.| Water.| Water.|
+------+-------+-------+-------+-------+-------+-------+-------+
|_Deg._| | | | | | | |
| 30 |0·83896|0·84995|0·85957|0·86825|0·87585|0·88282|0·88921|
| 35 | ·83672| ·84769| ·85729| ·86587| ·87357| ·88059| ·88701|
| 40 | ·83445| ·84539| ·85507| ·86361| ·87184| ·87838| ·88481|
| 45 | ·83214| ·84310| ·85277| ·86131| ·86905| ·87613| ·88255|
| 50 | ·82977| ·84076| ·85042| ·85902| ·86676| ·87384| ·88030|
| 55 | ·82736| ·83834| ·84802| ·85664| ·86441| ·87150| ·87796|
| 60 | ·82500| ·83599| ·84568| ·85430| ·86208| ·86918| ·87569|
| 65 | ·82262| ·83362| ·84334| ·85193| ·85976| ·86686| ·87337|
| 70 | ·82023| ·83124| ·84092| ·84951| ·85736| ·86451| ·87105|
| 75 | ·81780| ·82878| ·83851| ·84710| ·85496| ·86212| ·86864|
| 80 | ·81530| ·82631| ·83603| ·84467| ·85248| ·85966| ·86622|
| 85 | ·81291| ·82396| ·83371| ·84243| ·85036| ·85757| ·86411|
| 90 | ·81044| ·82150| ·83126| ·84001| ·84797| ·85518| ·86172|
| 95 | ·80794| ·81900| ·82877| ·83753| ·84550| ·85272| ·85928|
| 100 | ·80548| ·81657| ·82630| ·83513| ·84038| ·85031| ·85688|
+------+-------+-------+-------+-------+-------+-------+-------+
+------+-------+-------+-------+-------+--------+-------+-------+
|Tem- | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
|pera- |Alcohol|Alcohol|Alcohol|Alcohol|Alcohol |Alcohol|Alcohol|
|ture, | 35 | 40 | 45 | 50 | 55 | 60 | 65 |
|Fahr. | Water.| Water.| Water.| Water.| Water. | Water.| Water.|
+------+-------+-------+-------+-------+--------+-------+-------+
|_Deg._| | | | | | | |
| 30 |0·89511|0·90054|0·90558|0·91023|0·91449 |0·91847|0·92217|
| 35 | ·89294| ·89839| ·90345| ·90811| ·91241 | ·91640| ·92009|
| 40 | ·89073| ·89617| ·90127| ·90596| ·91026 | ·91428| ·91799|
| 45 | ·88849| ·89396| ·89909| ·90380| ·90812 | ·91211| ·91584|
| 50 | ·88626| ·89174| ·89684| ·90160| ·90596 | ·90997| ·91370|
| 55 | ·88393| ·88945| ·89458| ·89933| ·90367 | ·90768| ·91144|
| 60 | ·88169| ·88720| ·89232| ·89707| ·90144 | ·90549| ·90927|
| 65 | ·87938| ·88490| ·89006| ·89479| ·89920 | ·90328| ·90707|
| 70 | ·87705| ·88254| ·88773| ·89252| ·89695 | ·90104| ·90484|
| 75 | ·87466| ·88018| ·88538| ·89018| ·89464 | ·89872| ·90252|
| 80 | ·87228| ·87776| ·88301| ·88781| ·89225 | ·89639| ·90021|
| 85 | ·87021| ·87590| ·88120| ·88609| ·89043 | ·89460| ·89843|
| 90 | ·86787| ·87360| ·87889| ·88376| ·88817 | ·89230| ·89617|
| 95 | ·86542| ·87114| ·87654| ·88146| ·88588 | ·89003| ·89390|
| 100 | ·86302| ·86879| ·87421| ·87915| ·883671| ·88769| ·89158|
+------+-------+-------+-------+-------+--------+-------+-------+
+------+-------+-------+-------+-------+-------+-------+-------+
|Tem- | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
|pera- |Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|
|ture, | 70 | 75 | 80 | 85 | 90 | 95 | 100 |
|Fahr. | Water.| Water.| Water.| Water.| Water.| Water.| Water.|
+------+-------+-------+-------+-------+-------+-------+-------+
|_Deg._| | | | | | | |
| 30 |0·92563|0·92889|0·93191|0·93474|0·93741|0·93991|0·94222|
| 35 | ·92355| ·92680| ·92986| ·93274| ·93541| ·93790| ·94025|
| 40 | ·92151| ·92476| ·92783| ·93072| ·93341| ·93592| ·93827|
| 45 | ·91937| ·92264| ·92570| ·92859| ·93131| ·93382| ·93621|
| 50 | ·91723| ·92051| ·92358| ·92647| ·92919| ·93177| ·93419|
| 55 | ·91502| ·91837| ·92145| ·92436| ·92707| ·92963| ·93208|
| 60 | ·91287| ·91622| ·91933| ·92225| ·92499| ·92758| ·93002|
| 65 | ·91066| ·91400| ·91715| ·92010| ·92283| ·92546| ·92794|
| 70 | ·90847| ·91181| ·91493| ·91793| ·92069| ·92333| ·92580|
| 75 | ·90617| ·90952| ·91270| ·91569| ·91849| ·92111| ·92364|
| 80 | ·90385| ·90723| ·91046| ·91340| ·91622| ·91891| ·92142|
| 85 | ·90209| ·90558| ·90882| ·91186| ·91465| ·91729| ·91969|
| 90 | ·89988| ·90342| ·90688| ·90967| ·91248| ·91511| ·91751|
| 95 | ·89763| ·90119| ·90443| ·90747| ·91029| ·91290| ·91531|
| 100 | ·89536| ·89889| ·90215| ·90522| ·90805| ·91066| ·91310|
+------+-------+-------+-------+-------+-------+-------+-------+
+------+-------+-------+-------+-------+-------+-------+-------+
|Tem- | 95 | 90 | 85 | 80 | 75 | 70 | 65 |
|pera- |Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|
|ture, | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
|Fahr. | Water.| Water.| Water.| Water.| Water.| Water.| Water.|
+------+-------+-------+-------+-------+-------+-------+-------+
|_Deg._| | | | | | | |
| 30 |0·94447|0·94675|0·94920|0·95173|0·95429|0·95681|0·95944|
| 35 | ·94249| ·94484| ·94734| ·94988| ·95246| ·95502| ·95772|
| 40 | ·94058| ·94295| ·94547| ·94802| ·95060| ·95328| ·95602|
| 45 | ·93860| ·94096| ·94348| ·94605| ·94871| ·95143| ·95423|
| 50 | ·93658| ·93897| ·94149| ·94414| ·94683| ·94958| ·95243|
| 55 | ·93452| ·93696| ·93948| ·94213| ·94486| ·94767| ·95057|
| 60 | ·93247| ·93493| ·93749| ·94018| ·94296| ·94579| ·94876|
| 65 | ·93040| ·93285| ·93546| ·93822| ·94099| ·94388| ·94689|
| 70 | ·92828| ·93076| ·93337| ·93616| ·93898| ·94193| ·94500|
| 75 | ·92613| ·92865| ·93132| ·93413| ·93695| ·93989| ·94301|
| 80 | ·92393| ·92646| ·92917| ·93201| ·93488| ·93785| ·94102|
+------+-------+-------+-------+-------+-------+-------+-------+
+------+-------+-------+-------+-------+-------+-------+-------+
|Tem- | 60 | 55 | 50 | 45 | 40 | 35 | 30 |
|pera- |Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|
|ture, | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
|Fahr. | Water.| Water.| Water.| Water.| Water.| Water.| Water.|
+------+-------+-------+-------+-------+-------+-------+-------+
|_Deg._| | | | | | | |
| 30 |0·96209|0·96470|0·96719|0·96967|0·97200|0·97418|0·97635|
| 35 | ·96048| ·96315| ·96579| ·96840| ·97086| ·97319| ·97556|
| 40 | ·95879| ·96159| ·96434| ·96706| ·96967| ·97220| ·97472|
| 45 | ·95703| ·95993| ·96280| ·96563| ·96840| ·97110| ·97384|
| 50 | ·95534| ·95831| ·96126| ·96420| ·96708| ·96995| ·97284|
| 55 | ·95357| ·95662| ·95966| ·96272| ·96575| ·96877| ·97181|
| 60 | ·95181| ·95493| ·95804| ·96122| ·96437| ·96752| ·97074|
| 65 | ·95000| ·95318| ·95635| ·95962| ·96288| ·96620| ·96959|
| 70 | ·94813| ·95139| ·95469| ·95802| ·96143| ·96484| ·96836|
| 75 | ·94623| ·94957| ·95292| ·95638| ·95987| ·96344| ·96708|
| 80 | ·94431| ·94768| ·95111| ·95467| ·95826| ·96192| ·96568|
+------+-------+-------+-------+-------+-------+-------+-------+
+------+-------+-------+-------+-------+-------+
|Tem- | 25 | 20 | 15 | 10 | 5 |
|pera- |Alcohol|Alcohol|Alcohol|Alcohol|Alcohol|
|ture, | 100 | 100 | 100 | 100 | 100 |
|Fahr. | Water.| Water.| Water.| Water.| Water.|
+------+-------+-------+-------+-------+-------+
|_Deg._| | | | | |
| 30 |0·97860|0·98108|0·98412|0·98804|0·99334|
| 35 | ·97801| ·98076| ·98397| ·98804| ·99344|
| 40 | ·97737| ·98033| ·98373| ·98795| ·99345|
| 45 | ·97666| ·97980| ·98338| ·98774| ·99338|
| 50 | ·97589| ·97920| ·98293| ·98745| ·99316|
| 55 | ·97500| ·97847| ·98239| ·98702| ·99284|
| 60 | ·97410| ·97771| ·98176| ·98654| ·99244|
| 65 | ·97309| ·97688| ·98106| ·98594| ·99194|
| 70 | ·97203| ·97596| ·98028| ·98527| ·99134|
| 75 | ·97086| ·97495| ·97943| ·98454| ·99066|
| 80 | ·96963| ·97385| ·97845| ·98367| ·98991|
+------+-------+-------+-------+-------+-------+
Experiments were made, by direction of the committee, to verify Gilpin’s
tables, which showed that the error introduced in ascertaining the
strength of spirits by tables founded on Gilpin’s numbers must be quite
insensible in the practice of the revenue. The discrepancies thus
detected, on a mixture of a given strength, did not amount in any one
instance to unity in the fourth place of decimals. From a careful
inspection of such documents the committee are of opinion, that Gilpin’s
tables possess a degree of accuracy far surpassing what could be
expected, and sufficiently perfect for all practical or scientific
purposes.
The following table is given by Mr. Lubbock, for converting the
_apparent_ specific gravity, or _indication_, into true specific
gravity:--
+-----+-----------------------------------------+-----+
|Indi-| - Temperature + |Indi-|
| ca- +------+------+------+------+------+------+ ca- |
|tion.| 30° | 32° | 37° | 42° | 47° | 52° |tion.|
+-----+------+------+------+------+------+------+-----+
| ·82 |·00083|·00078|·00065|·00052|·00039|·00025| ·82 |
| ·83 |·00084|·00079|·00066|·00052|·00039|·00026| ·83 |
| ·84 |·00085|·00080|·00066|·00053|·00039|·00026| ·84 |
| ·85 |·00086|·00081|·00067|·00054|·00040|·00026| ·85 |
| ·86 |·00087|·00082|·00068|·00054|·00040|·00027| ·86 |
| ·87 |·00088|·00083|·00069|·00055|·00041|·00027| ·87 |
| ·88 |·00089|·00084|·00070|·00055|·00041|·00027| ·88 |
| ·89 |·00090|·00085|·00070|·00055|·00042|·00028| ·89 |
| ·90 |·00091|·00085|·00071|·00056|·00042|·00028| ·90 |
| ·91 |·00092|·00086|·00072|·00057|·00043|·00028| ·91 |
| ·92 |·00093|·00087|·00073|·00058|·00043|·00029| ·92 |
| ·93 |·00094|·00088|·00073|·00059|·00044|·00029| ·93 |
| ·94 |·00095|·00089|·00074|·00059|·00044|·00029| ·94 |
| ·95 |·00096|·00090|·00075|·00060|·00045|·00029| ·95 |
| ·96 |·00097|·00091|·00076|·00060|·00045|·00030| ·96 |
| ·97 |·00098|·00092|·00077|·00061|·00046|·00030| ·97 |
| ·98 |·00099|·00093|·00077|·00062|·00046|·00030| ·98 |
| ·99 |·00100|·00094|·00078|·00062|·00047|·00031| ·99 |
|1·00 |·00101|·00095|·00079|·00063|·00047|·00031|1·00 |
+-----+------+------+------+------+------+------+-----+
+-----+-----------------------------------------+-----+
|Indi-| - Temperature + |Indi-|
| ca- +------+------+------+------+------+------+ ca- |
|tion.| 57° | 62° | 67° | 72° | 77° | 80° |tion.|
+-----+------+------+------+------+------+------+-----+
| ·82 |·00012| |·00011|·00024|·00035|·00042| ·82 |
| ·83 |·00012| |·00012|·00024|·00036|·00042| ·83 |
| ·84 |·00013| |·00012|·00024|·00036|·00043| ·84 |
| ·85 |·00013| |·00012|·00025|·00037|·00043| ·85 |
| ·86 |·00013| |·00012|·00025|·00037|·00044| ·86 |
| ·87 |·00013| |·00012|·00025|·00037|·00044| ·87 |
| ·88 |·00013| |·00012|·00026|·00038|·00045| ·88 |
| ·89 |·00013| |·00012|·00026|·00038|·00045| ·89 |
| ·90 |·00014| |·00013|·00026|·00039|·00046| ·90 |
| ·91 |·00014| |·00013|·00026|·00039|·00046| ·91 |
| ·92 |·00014| |·00013|·00027|·00040|·00047| ·92 |
| ·93 |·00014| |·00013|·00027|·00040|·00047| ·93 |
| ·94 |·00014| |·00013|·00027|·00040|·00048| ·94 |
| ·95 |·00014| |·00013|·00028|·00041|·00048| ·95 |
| ·96 |·00014| |·00013|·00028|·00041|·00049| ·96 |
| ·97 |·00015| |·00014|·00028|·00042|·00049| ·97 |
| ·98 |·00015| |·00014|·00028|·00042|·00050| ·98 |
| ·99 |·00015| |·00014|·00029|·00043|·00050| ·99 |
|1·00 |·00015| | | | | |1·00 |
+-----+------+------+------+------+------+------+-----+
[Illustration: _Fig._ 5.]
The hydrometer constructed, under the directions of the Commissioners of
Excise, by Mr. Bate, has a scale of 4 inches in length divided into 100
parts, and 9 weights. It has thus a range of 900 divisions, and
expresses specific gravities at the temperature of 62° Fahr. In order to
render this instrument so accurate a measurer of the specific gravity,
at the standard temperature, as to involve no error of an appreciable
amount, Mr. Bate has constructed the weights (which in this instrument
are immersed in the fluid of different specific gravities) so that each
successive weight should have an increase of bulk over the preceding
weight equal to that part of the stem occupied by the scale, and an
increase of weight sufficient to take the whole of the scale, and no
more, down to the liquid. This arrangement requires great accuracy of
workmanship, and enhances the price of the instrument. But it allows of
increased strength in the ball, where it is very much required, and it
gives, upon inspection only, the indication (apparent specific gravity)
by which the general table is to be examined and the result ascertained.
_Fig._ 5. represents this instrument and two of its nine ballast
weights. It comprehends all specific gravities between 820 and 1000. It
indicates true specific gravity with almost perfect accuracy at the
temperature of 62° Fahr.; but it does not exclude other instruments from
being used in conjunction with tables. The latter are, in fact,
independent of the instrument, and may be used with gravimeters, or any
instrument affording indications by specific gravity at a given
temperature.
The commercial value of spirituous liquors being much lower in France
than in England, a less sensible instrument becomes sufficient for the
wants of that country. Baumé’s and Cartier’s hydrometers, with short
arbitrary scales, are very much employed, but they have been lately
superseded by an ingenious and ready instrument contrived by M. Gay
Lussac, and called by him an _alcoomètre_. He takes for the term of
comparison pure alcohol by volume, at the temperature of 15° Cent., and
represents the strength of it by 100 _centimes_, or by unity.
Consequently, the strength of a spirituous liquid is the number of
centimes in volume of pure alcohol which that liquid contains at the
temperature of 15° Cent. The instrument is formed like a common
hydrometer, and is graduated for the temperature of 15° Cent. Its scale
is divided into 100 parts or degrees, each of which denotes a centime of
alcohol; the division 0 at the bottom of the stem corresponds to pure
water, and the division 100 at its top, to pure alcohol. When immersed
in a spirituous liquor at 15° Cent. (59° Fahr.) it announces its
strength directly. For example: if in spirits supposed at the
temperature of 15° Cent. it sinks to the division 50, it indicates that
the strength of this liquor is 50 per cent., or that it contains 50
centimes of pure alcohol. In our new British proof spirit, it would sink
to nearly 57, indicating 57 by volume of pure alcohol, allowing for
condensation, or 50 by weight. A table of correction is given for
temperature, which he calls “Table of real strength of spirituous
liquors.” The first vertical column of this table contains the
temperatures, from 0° to 30° Cent., and the first horizontal line the
indications of the alcoomètre. In the same table we have most
ingeniously inserted a correction for the volume of the spirits when the
temperature differs from 15° Cent. If we take 1000 litres or gallons,
measured at the temperature of 2°, of a spirituous liquor whose apparent
strength is 44^{c}; its real strength at 15° will from the preceding
mode of correction be 49^{c}. On heating this liquid to 15°, in order to
find its real specific gravity or strength, its bulk will become
greater; and, instead of 1000 litres or gallons, which it measured at
2°, we shall have 1009 at 15° C. This number is inscribed in smaller
characters in the same square cell with the real force, precisely under
49^{c}. All the numbers in small characters, printed under each _real
strength_, indicate the volume which 1000 litres of a spirituous liquor
would have, when measured at the temperature at which its apparent
strength is taken. In the above example, the quantity in litres or
gallons of pure alcohol contained in 1000 litres or gallons of the
spirits, measured at the temperature of 2°, will be, therefore,--1009
lit. × 0·49 = 494 lit. 41.
This quantity of pure alcohol, thus estimated, is called _richness of
spirit in alcohol_, or simply _richness_.
Let us take an example similar to the preceding, but at a higher
temperature than 15° Cent. Suppose we have 1000 litres measured, at the
temperature of 25°, of spirits whose apparent strength is 53^{c}, what
is the real quantity of pure alcohol which this spirit contains at the
temperature of 15°? We shall find in the table, first of all, that the
real strength of the spirits is 49^{c}·3. As to its bulk or volume, it
is very clear that the 1000 litres in cooling from 25° to 15°, will
occupy a smaller space. This volume will be 993 litres; it is inscribed
directly below 49^{c}·3, the real strength. We shall therefore have of
pure alcohol, contained in the 1000 litres of spirits, measured at the
temperature of 25°, or their _richness_, 993 lit. × 0·493 = 489 lit. 55.
Alcometrical Table of real Strength, by M. Gay Lussac.
+-------+------+------+------+------+------+------+------+------+
|Temper-|31^{c}|32^{c}|33^{c}|34^{c}|35^{c}|36^{c}|37^{c}|38^{c}|
| ature | | | | | | | | |
| C. | | | | | | | | |
+-------+------+------+------+------+------+------+------+------+
| _Deg._| | | | | | | | |
| 10 | 33·0 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
| | 1002 | 1002 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 |
| +------+------+------+------+------+------+------+------+
| 11 | 32·6 | 33·6 | 34·6 | 35·6 | 36·6 | 37·6 | 38·6 | 39·6 |
| | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 12 | 32·2 | 33·2 | 34·2 | 35·2 | 36·2 | 37·2 | 38·2 | 39·2 |
| | 1001 | 1001 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 13 | 31·8 | 32·8 | 33·8 | 34·8 | 35·8 | 36·8 | 37·8 | 38·8 |
| | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+------+------+------+------+
| 14 | 31·4 | 32·4 | 33·4 | 34·4 | 35·4 | 36·4 | 37·4 | 38·4 |
| | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+------+------+------+------+
| 15 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 |
| | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
| +------+------+------+------+------+------+------+------+
| 16 | 30·6 | 31·6 | 32·5 | 33·5 | 34·5 | 35·5 | 36·5 | 37·5 |
| | 1000 | 1000 | 999 | 999 | 999 | 999 | 999 | 999 |
| +------+------+------+------+------+------+------+------+
| 17 | 30·2 | 31·2 | 32·1 | 33·1 | 34·1 | 35·1 | 36·1 | 37·1 |
| | 999 | 999 | 999 | 999 | 999 | 999 | 999 | 999 |
| +------+------+------+------+------+------+------+------+
| 18 | 29·8 | 30·8 | 31·7 | 32·7 | 33·7 | 34·7 | 35·7 | 36·7 |
| | 999 | 999 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 19 | 29·4 | 30·4 | 31·3 | 32·3 | 33·3 | 34·3 | 35·3 | 36·3 |
| | 998 | 998 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 20 | 29 | 30 | 30·9 | 31·9 | 32·9 | 33·9 | 34·9 | 35·9 |
| | 998 | 998 | 997 | 997 | 997 | 997 | 997 | 997 |
| +------+------+------+------+------+------+------+------+
| 21 | 28·6 | 29·6 | 30·5 | 31·5 | 32·5 | 33·5 | 34·5 | 35·5 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 997 | 996 |
| +------+------+------+------+------+------+------+------+
| 22 | 28·2 | 29·2 | 30·1 | 31·1 | 32·1 | 33·1 | 34·1 | 35·1 |
| | 997 | 997 | 996 | 996 | 996 | 996 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 23 | 27·8 | 28·8 | 29·7 | 30·7 | 31·7 | 32·7 | 33·7 | 34·7 |
| | 996 | 996 | 996 | 996 | 996 | 996 | 996 | 995 |
| +------+------+------+------+------+------+------+------+
| 24 | 27·4 | 28·4 | 29·3 | 30·3 | 31·3 | 32·3 | 33·3 | 34·3 |
| | 996 | 996 | 995 | 995 | 995 | 995 | 995 | 995 |
| +------+------+------+------+------+------+------+------+
| 25 | 27 | 28 | 28·9 | 29·9 | 30·9 | 31·9 | 32·9 | 33·9 |
| | 995 | 995 | 995 | 995 | 995 | 994 | 994 | 994 |
+-------+------+------+------+------+------+------+------+------+
+-------+------+------+------+------+------+------+------+------+
|Temper-|39^{c}|40^{c}|41^{c}|42^{c}|43^{c}|44^{c}|45^{c}|46^{c}|
| ature | | | | | | | | |
| C. | | | | | | | | |
+-------+------+------+------+------+------+------+------+------+
| _Deg._| | | | | | | | |
| 10 | 41 | 42 | 43 | 44 | 45 | 46 | 46·9 | 47·9 |
| | 1003 | 1003 | 1003 | 1004 | 1004 | 1004 | 1004 | 1004 |
| +------+------+------+------+------+------+------+------+
| 11 | 40·6 | 41·6 | 42·6 | 43·6 | 44·6 | 45·6 | 46·6 | 47·6 |
| | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 |
| +------+------+------+------+------+------+------+------+
| 12 | 40·2 | 41·2 | 42·2 | 43·2 | 44·2 | 45·2 | 46·2 | 47·2 |
| | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 13 | 39·8 | 40·8 | 41·8 | 42·8 | 43·8 | 44·8 | 45·8 | 46·8 |
| | 1001 | 1001 | 1001 | 1001 | 1001 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 14 | 39·4 | 40·4 | 41·4 | 42·4 | 43·4 | 44·4 | 45·4 | 46·4 |
| | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+------+------+------+------+
| 15 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 |
| | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
| +------+------+------+------+------+------+------+------+
| 16 | 38·5 | 39·5 | 40·6 | 41·6 | 42·6 | 43·6 | 44·6 | 45·6 |
| | 999 | 999 | 999 | 999 | 999 | 999 | 999 | 999 |
| +------+------+------+------+------+------+------+------+
| 17 | 38·1 | 39·1 | 40·2 | 41·2 | 42·2 | 43·2 | 44·9 | 45·2 |
| | 999 | 999 | 999 | 999 | 999 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 18 | 37·7 | 38·7 | 39·8 | 40·8 | 41·8 | 42·8 | 43·8 | 44·9 |
| | 998 | 998 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 19 | 37·3 | 38·3 | 39·4 | 40·4 | 41·4 | 42·5 | 43·5 | 44·5 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 997 | 997 |
| +------+------+------+------+------+------+------+------+
| 20 | 36·9 | 37·9 | 39 | 40 | 41 | 42·1 | 43·1 | 44·1 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 21 | 36·5 | 37·5 | 38·6 | 39·6 | 40·6 | 41·7 | 42·7 | 43·7 |
| | 996 | 996 | 996 | 996 | 996 | 996 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 22 | 36·1 | 37·1 | 38·2 | 39·2 | 40·2 | 41·3 | 42·3 | 43·3 |
| | 996 | 996 | 996 | 995 | 995 | 995 | 995 | 995 |
| +------+------+------+------+------+------+------+------+
| 23 | 35·7 | 36·7 | 37·8 | 38·8 | 39·8 | 40·9 | 41·9 | 42·9 |
| | 995 | 995 | 995 | 995 | 995 | 994 | 994 | 994 |
| +------+------+------+------+------+------+------+------+
| 24 | 35·3 | 36·3 | 37·4 | 38·4 | 39·4 | 40·5 | 41·5 | 42·5 |
| | 995 | 994 | 994 | 994 | 994 | 994 | 994 | 994 |
| +------+------+------+------+------+------+------+------+
| 25 | 34·9 | 35·9 | 37 | 38 | 39 | 40·1 | 42·1 | 42·2 |
| | 994 | 994 | 994 | 994 | 993 | 993 | 993 | 993 |
+-------+------+------+------+------+------+------+------+------+
+-------+------+------+------+------+------+------+------+------+
|Temper-|47^{c}|48^{c}|49^{c}|50^{c}|51^{c}|52^{c}|53^{c}|54^{c}|
| ature | | | | | | | | |
| C. | | | | | | | | |
+-------+------+------+------+------+------+------+------+------+
| _Deg._| | | | | | | | |
| 10 | 48·9 | 49·9 | 50·9 | 51·8 | 52·8 | 53·8 | 54·8 | 55·8 |
| | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 |
| +------+------+------+------+------+------+------+------+
| 11 | 48·6 | 49·5 | 50·5 | 51·5 | 52·5 | 53·5 | 54·4 | 55·4 |
| | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 |
| +------+------+------+------+------+------+------+------+
| 12 | 48·2 | 49·2 | 50·2 | 51·1 | 52·1 | 53·1 | 54·1 | 55 |
| | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 13 | 47·8 | 48·8 | 49·8 | 50·8 | 51·8 | 52·7 | 53·7 | 54·7 |
| | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 14 | 47·4 | 48·4 | 49·4 | 50·4 | 51·4 | 52·3 | 53·3 | 54·3 |
| | 1001 | 1001 | 1001 | 1000 | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+------+------+------+------+
| 15 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 |
| | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
| +------+------+------+------+------+------+------+------+
| 16 | 46·6 | 47·6 | 48·6 | 49·6 | 50·6 | 51·6 | 52·6 | 53·6 |
| | 999 | 999 | 999 | 999 | 999 | 999 | 999 | 999 |
| +------+------+------+------+------+------+------+------+
| 17 | 46·2 | 47·2 | 48·2 | 49·2 | 50·3 | 51·3 | 52·3 | 53·3 |
| | 998 | 998 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 18 | 45·9 | 46·9 | 47·9 | 48·9 | 49·9 | 50·9 | 51·9 | 52·9 |
| | 998 | 998 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 19 | 45·5 | 46·5 | 47·5 | 48·5 | 49·5 | 50·6 | 51·6 | 52·6 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 997 | 997 |
| +------+------+------+------+------+------+------+------+
| 20 | 45·1 | 46·1 | 47·2 | 48·2 | 49·2 | 50·2 | 51·2 | 52·2 |
| | 996 | 996 | 996 | 996 | 996 | 996 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 21 | 44·8 | 45·8 | 46·8 | 47·8 | 48·8 | 49·8 | 50·8 | 51·8 |
| | 996 | 996 | 995 | 995 | 995 | 995 | 995 | 995 |
| +------+------+------+------+------+------+------+------+
| 22 | 44·3 | 45·3 | 46·4 | 47·4 | 48·4 | 49·4 | 50·4 | 51·4 |
| | 995 | 995 | 995 | 995 | 995 | 995 | 995 | 994 |
| +------+------+------+------+------+------+------+------+
| 23 | 43·9 | 44·9 | 46 | 47 | 48 | 49·1 | 50·1 | 51·1 |
| | 994 | 994 | 994 | 994 | 994 | 994 | 994 | 994 |
| +------+------+------+------+------+------+------+------+
| 24 | 43·6 | 44·6 | 45·6 | 46·6 | 47·6 | 48·7 | 49·7 | 50·7 |
| | 994 | 994 | 993 | 993 | 993 | 993 | 993 | 693 |
| +------+------+------+------+------+------+------+------+
| 25 | 43·2 | 44·2 | 45·2 | 46·3 | 47·3 | 48·3 | 49·3 | 50·3 |
| | 993 | 993 | 993 | 993 | 993 | 993 | 993 | 992 |
+-------+------+------+------+------+------+------+------+------+
+-------+------+------+------+------+------+------+------+------+
|Temper-|55^{c}|56^{c}|57^{c}|58^{c}|59^{c}|60^{c}|61^{c}|62^{c}|
| ature | | | | | | | | |
| C. | | | | | | | | |
+-------+------+------+------+------+------+------+------+------+
| _Deg._| | | | | | | | |
| 10 | 56·8 | 57·8 | 58·8 | 59·7 | 60·7 | 61·7 | 62·7 | 63·7 |
| | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 |
| +------+------+------+------+------+------+------+------+
| 11 | 56·4 | 57·4 | 58·4 | 59·4 | 60·4 | 61·4 | 62·4 | 63·4 |
| | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 |
| +------+------+------+------+------+------+------+------+
| 12 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 |
| | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 13 | 55·7 | 56·7 | 57·7 | 58·7 | 59·7 | 60·7 | 61·7 | 62·7 |
| | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 14 | 55·3 | 56·3 | 57·3 | 58·3 | 59·3 | 60·3 | 61·3 | 62·3 |
| | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+------+------+------+------+
| 15 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 |
| | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
| +------+------+------+------+------+------+------+------+
| 16 | 54·6 | 55·6 | 56·6 | 57·6 | 58·6 | 59·6 | 60·6 | 61·7 |
| | 999 | 999 | 999 | 999 | 999 | 999 | 999 | 999 |
| +------+------+------+------+------+------+------+------+
| 17 | 54·3 | 55·3 | 56·3 | 57·3 | 58·3 | 59·3 | 60·3 | 61·3 |
| | 998 | 998 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 18 | 53·9 | 54·9 | 55·9 | 56·9 | 57·9 | 58·9 | 59·9 | 61 |
| | 998 | 998 | 998 | 997 | 997 | 997 | 997 | 997 |
| +------+------+------+------+------+------+------+------+
| 19 | 53·6 | 54·6 | 55·6 | 56·6 | 57·6 | 58·6 | 59·6 | 60·6 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 997 | 997 |
| +------+------+------+------+------+------+------+------+
| 20 | 53·2 | 54·2 | 55·2 | 56·2 | 57·2 | 58·2 | 59·2 | 60·3 |
| | 996 | 996 | 996 | 996 | 996 | 996 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 21 | 52·9 | 53·9 | 54·9 | 55·9 | 56·9 | 57·9 | 58·9 | 59·9 |
| | 995 | 995 | 995 | 995 | 995 | 995 | 995 | 995 |
| +------+------+------+------+------+------+------+------+
| 22 | 52·5 | 53·5 | 54·5 | 55·5 | 56·5 | 57·5 | 58·5 | 59·5 |
| | 994 | 994 | 994 | 994 | 994 | 994 | 994 | 994 |
| +------+------+------+------+------+------+------+------+
| 23 | 52·1 | 53·1 | 54·1 | 55·1 | 56·1 | 57·1 | 58·1 | 59·2 |
| | 994 | 994 | 994 | 993 | 993 | 993 | 993 | 993 |
| +------+------+------+------+------+------+------+------+
| 24 | 51·8 | 52·8 | 53·8 | 54·8 | 55·8 | 56·8 | 57·8 | 58·9 |
| | 993 | 993 | 993 | 993 | 993 | 992 | 992 | 992 |
| +------+------+------+------+------+------+------+------+
| 25 | 51·4 | 52·4 | 53·4 | 54·4 | 55·5 | 56·5 | 57·5 | 58·5 |
| | 992 | 992 | 992 | 992 | 992 | 992 | 992 | 992 |
+-------+------+------+------+------+------+------+------+------+
+-------+------+------+------+------+------+------+------+------+
|Temper-|63^{c}|64^{c}|65^{c}|66^{c}|67^{c}|68^{c}|69^{c}|70^{c}|
| ature | | | | | | | | |
| C. | | | | | | | | |
+-------+------+------+------+------+------+------+------+------+
| _Deg._| | | | | | | | |
| 10 | 64·7 | 65·7 | 66·7 | 67·6 | 68·6 | 69·6 | 70·6 | 71·6 |
| | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 |
| +------+------+------+------+------+------+------+------+
| 11 | 64·4 | 65·4 | 66·4 | 67·3 | 68·3 | 69·3 | 70·3 | 71·3 |
| | 1003 | 1003 | 1003 | 1003 | 1003 | 1004 | 1004 | 1004 |
| +------+------+------+------+------+------+------+------+
| 12 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 |
| | 1002 | 1002 | 1002 | 1002 | 1003 | 1003 | 1003 | 1003 |
| +------+------+------+------+------+------+------+------+
| 13 | 63·7 | 64·7 | 65·7 | 66·7 | 67·7 | 68·7 | 69·6 | 70·6 |
| | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 14 | 63·3 | 64·3 | 65·3 | 66·3 | 67·3 | 68·3 | 69·3 | 70·3 |
| | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+------+------+------+------+
| 15 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 |
| | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
| +------+------+------+------+------+------+------+------+
| 16 | 62·7 | 63·7 | 64·7 | 65·7 | 66·7 | 67·7 | 68·7 | 69·7 |
| | 999 | 999 | 999 | 999 | 999 | 999 | 999 | 999 |
| +------+------+------+------+------+------+------+------+
| 17 | 62·3 | 63·3 | 64·3 | 65·3 | 66·3 | 67·3 | 68·3 | 69·3 |
| | 998 | 998 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 18 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 997 | 997 |
| +------+------+------+------+------+------+------+------+
| 19 | 61·6 | 62·7 | 63·7 | 64·7 | 65·7 | 66·7 | 67·7 | 68·7 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 20 | 61·3 | 62·3 | 63·3 | 64·3 | 65·4 | 66·4 | 67·4 | 68·4 |
| | 996 | 996 | 996 | 996 | 996 | 996 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 21 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68·1 |
| | 995 | 995 | 995 | 995 | 995 | 995 | 995 | 995 |
| +------+------+------+------+------+------+------+------+
| 22 | 60·6 | 61·6 | 62·7 | 63·7 | 64·7 | 65·7 | 66·7 | 67·7 |
| | 994 | 994 | 994 | 994 | 994 | 994 | 994 | 994 |
| +------+------+------+------+------+------+------+------+
| 23 | 60·2 | 61·3 | 62·3 | 63·3 | 64·3 | 65·4 | 66·4 | 67·4 |
| | 993 | 993 | 993 | 993 | 993 | 993 | 993 | 993 |
| +------+------+------+------+------+------+------+------+
| 24 | 59·9 | 61 | 62 | 63 | 64 | 65 | 66 | 67·1 |
| | 992 | 992 | 992 | 992 | 992 | 992 | 992 | 992 |
| +------+------+------+------+------+------+------+------+
| 25 | 59·5 | 60·6 | 61·6 | 62·6 | 63·7 | 64·7 | 65·7 | 66·7 |
| | 992 | 991 | 991 | 991 | 991 | 991 | 991 | 991 |
+-------+------+------+------+------+------+------+------+------+
+-------+------+------+------+------+------+------+------+------+
|Temper-|71^{c}|72^{c}|73^{c}|74^{c}|75^{c}|76^{c}|77^{c}|78^{c}|
| ature | | | | | | | | |
| C. | | | | | | | | |
+-------+------+------+------+------+------+------+------+------+
| _Deg._| | | | | | | | |
| 10 | 72·6 | 73·5 | 74·5 | 75·5 | 76·5 | 77·5 | 78·5 | 79·5 |
| | 1004 | 1004 | 1005 | 1005 | 1005 | 1005 | 1005 | 1005 |
| +------+------+------+------+------+------+------+------+
| 11 | 72·3 | 73·2 | 74·2 | 75·2 | 76·2 | 77·2 | 78·2 | 79·2 |
| | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 |
| +------+------+------+------+------+------+------+------+
| 12 | 72 | 72·9 | 73·9 | 74·9 | 75·9 | 76·9 | 77·9 | 78·9 |
| | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 |
| +------+------+------+------+------+------+------+------+
| 13 | 71·6 | 72·6 | 73·6 | 74·6 | 75·6 | 76·6 | 77·6 | 78·6 |
| | 1002 | 1002 | 1002 | 1002 | 1092 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 14 | 71·3 | 72·3 | 73·3 | 74·3 | 75·3 | 76·3 | 77·3 | 78·3 |
| | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+------+------+------+------+
| 15 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 |
| | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
| +------+------+------+------+------+------+------+------+
| 16 | 70·7 | 71·7 | 72·7 | 73·7 | 74·7 | 75·7 | 76·7 | 77·7 |
| | 999 | 999 | 999 | 999 | 999 | 999 | 999 | 999 |
| +------+------+------+------+------+------+------+------+
| 17 | 70·3 | 71·3 | 72·3 | 73·3 | 74·3 | 75·4 | 76·4 | 77·4 |
| | 998 | 998 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 18 | 70 | 71 | 72 | 73 | 74 | 75·1 | 76·1 | 77·1 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 997 | 997 |
| +------+------+------+------+------+------+------+------+
| 19 | 69·7 | 70·7 | 71·7 | 72·7 | 73·7 | 74·7 | 75·8 | 76·8 |
| | 996 | 996 | 996 | 996 | 996 | 996 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 20 | 69·4 | 70·4 | 71·4 | 72·4 | 73·4 | 74·4 | 75·5 | 76·5 |
| | 996 | 996 | 995 | 995 | 995 | 995 | 995 | 995 |
| +------+------+------+------+------+------+------+------+
| 21 | 69·1 | 70·1 | 71·1 | 72·1 | 73·1 | 74·1 | 75·2 | 76·2 |
| | 995 | 995 | 995 | 994 | 994 | 994 | 994 | 994 |
| +------+------+------+------+------+------+------+------+
| 22 | 68·8 | 69·8 | 70·8 | 71·8 | 72·8 | 73·8 | 74·8 | 75·9 |
| | 994 | 994 | 994 | 994 | 993 | 993 | 993 | 993 |
| +------+------+------+------+------+------+------+------+
| 23 | 68·4 | 69·4 | 70·5 | 71·5 | 72·5 | 73·5 | 74·5 | 75·5 |
| | 993 | 993 | 993 | 993 | 992 | 992 | 992 | 992 |
| +------+------+------+------+------+------+------+------+
| 24 | 68·1 | 69·1 | 70·1 | 71·2 | 72·2 | 73·2 | 74·2 | 75·2 |
| | 992 | 992 | 992 | 992 | 992 | 992 | 992 | 991 |
| +------+------+------+------+------+------+------+------+
| 25 | 67·8 | 68·8 | 69·8 | 70·8 | 71·8 | 72·8 | 73·9 | 74·9 |
| | 991 | 991 | 991 | 991 | 991 | 991 | 991 | 991 |
+-------+------+------+------+------+------+------+------+------+
+-------+------+------+------+------+------+------+------+------+
|Temper-|79^{c}|80^{c}|81^{c}|82^{c}|83^{c}|84^{c}|85^{c}|86^{c}|
| ature | | | | | | | | |
| C. | | | | | | | | |
+-------+------+------+------+------+------+------+------+------+
| _Deg._| | | | | | | | |
| 10 | 80·5 | 81·5 | 82·4 | 83·4 | 84·4 | 85·4 | 86·4 | 87·4 |
| | 1005 | 1005 | 1005 | 1005 | 1005 | 1005 | 1005 | 1005 |
| +------+------+------+------+------+------+------+------+
| 11 | 80·2 | 81·2 | 82·2 | 83·1 | 84·1 | 85·1 | 86·1 | 87·1 |
| | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 | 1004 |
| +------+------+------+------+------+------+------+------+
| 12 | 79·9 | 80·9 | 81·9 | 82·9 | 83·9 | 84·8 | 85·8 | 86·8 |
| | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 | 1003 |
| +------+------+------+------+------+------+------+------+
| 13 | 79·6 | 80·6 | 81·6 | 82·6 | 83·6 | 84·6 | 85·5 | 86·5 |
| | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+------+------+------+------+
| 14 | 79·3 | 80·3 | 81·3 | 82·3 | 83·3 | 84·3 | 85·3 | 86·3 |
| | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+------+------+------+------+
| 15 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 |
| | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
| +------+------+------+------+------+------+------+------+
| 16 | 78·7 | 79·7 | 80·7 | 81·7 | 82·7 | 83·7 | 84·7 | 85·7 |
| | 999 | 999 | 999 | 999 | 999 | 999 | 999 | 999 |
| +------+------+------+------+------+------+------+------+
| 17 | 78·4 | 79·4 | 80·4 | 81·4 | 82·4 | 83·4 | 84·4 | 85·4 |
| | 998 | 998 | 998 | 998 | 998 | 998 | 998 | 998 |
| +------+------+------+------+------+------+------+------+
| 18 | 78·1 | 79·1 | 80·1 | 81·1 | 82·1 | 83·1 | 84·1 | 85·2 |
| | 997 | 997 | 997 | 997 | 997 | 997 | 997 | 997 |
| +------+------+------+------+------+------+------+------+
| 19 | 77·8 | 78·8 | 79·8 | 80·8 | 81·9 | 82·9 | 83·9 | 84·9 |
| | 996 | 996 | 996 | 996 | 996 | 996 | 996 | 996 |
| +------+------+------+------+------+------+------+------+
| 20 | 77·5 | 78·5 | 79·5 | 80·5 | 81·6 | 82·6 | 83·6 | 84·6 |
| | 995 | 995 | 995 | 995 | 995 | 995 | 995 | 995 |
| +------+------+------+------+------+------+------+------+
| 21 | 77·2 | 78·2 | 79·2 | 80·2 | 81·3 | 82·3 | 83·3 | 84·3 |
| | 994 | 994 | 994 | 994 | 994 | 994 | 994 | 994 |
| +------+------+------+------+------+------+------+------+
| 22 | 76·9 | 77·9 | 78·9 | 79·9 | 81 | 82 | 83 | 84 |
| | 993 | 993 | 993 | 993 | 993 | 993 | 993 | 993 |
| +------+------+------+------+------+------+------+------+
| 23 | 76·6 | 77·6 | 78·6 | 79·6 | 80·7 | 81·7 | 82·7 | 83·8 |
| | 992 | 992 | 992 | 992 | 992 | 992 | 992 | 992 |
| +------+------+------+------+------+------+------+------+
| 24 | 76·3 | 77·3 | 78·3 | 79·3 | 80·4 | 81·4 | 82·4 | 83·5 |
| | 991 | 991 | 991 | 991 | 991 | 991 | 991 | 991 |
| +------+------+------+------+------+------+------+------+
| 25 | 76 | 77 | 78 | 79 | 80·1 | 81·1 | 82·1 | 83·2 |
| | 991 | 991 | 991 | 991 | 990 | 990 | 990 | 990 |
+-------+------+------+------+------+------+------+------+------+
+-------+------+------+------+------+
|Temper-|87^{c}|88^{c}|89^{c}|90^{c}|
| ature | | | | |
| C. | | | | |
+-------+------+------+------+------+
| _Deg._| | | | |
| 10 | 88·3 | 89·3 | 90·2 | 91·2 |
| | 1005 | 1005 | 1005 | 1005 |
| +------+------+------+------+
| 11 | 88 | 89 | 90 | 91 |
| | 1004 | 1004 | 1004 | 1004 |
| +------+------+------+------+
| 12 | 87·8 | 88·7 | 89·7 | 90·7 |
| | 1003 | 1003 | 1003 | 1003 |
| +------+------+------+------+
| 13 | 87·5 | 88·5 | 89·5 | 90·5 |
| | 1002 | 1002 | 1002 | 1002 |
| +------+------+------+------+
| 14 | 87·3 | 88·2 | 89·2 | 90·2 |
| | 1001 | 1001 | 1001 | 1001 |
| +------+------+------+------+
| 15 | 87 | 88 | 89 | 90 |
| | 1000 | 1000 | 1000 | 1000 |
| +------+------+------+------+
| 16 | 86·7 | 87·7 | 88·7 | 89·7 |
| | 999 | 999 | 999 | 999 |
| +------+------+------+------+
| 17 | 86·4 | 87·4 | 88·4 | 89·5 |
| | 998 | 998 | 998 | 998 |
| +------+------+------+------+
| 18 | 86·2 | 87·2 | 88·2 | 89·2 |
| | 997 | 997 | 997 | 997 |
| +------+------+------+------+
| 19 | 85·9 | 86·9 | 87·9 | 88·9 |
| | 996 | 996 | 996 | 996 |
| +------+------+------+------+
| 20 | 85·6 | 86·6 | 87·7 | 88·7 |
| | 995 | 995 | 995 | 995 |
| +------+------+------+------+
| 21 | 85·3 | 86·4 | 87·4 | 88·4 |
| | 994 | 994 | 994 | 994 |
| +------+------+------+------+
| 22 | 85 | 86·1 | 87·1 | 88·2 |
| | 993 | 993 | 993 | 993 |
| +------+------+------+------+
| 23 | 84·8 | 85·8 | 86·8 | 87·9 |
| | 992 | 992 | 992 | 992 |
| +------+------+------+------+
| 24 | 84·5 | 85·5 | 86·5 | 87·6 |
| | 991 | 991 | 991 | 991 |
| +------+------+------+------+
| 25 | 84·2 | 85·2 | 86·3 | 87·4 |
| | 990 | 990 | 990 | 990 |
+-------+------+------+------+------+
I consider the preceding table, which I have extracted from the longer
tables of M. Gay Lussac, as an important addition to the resources of
British dealers and manufacturing chemists. With the aid of his little
instrument, which may be got for a trifle from its ingenious maker, M.
Collardeau, Rue Faubourg St. Martin, at Paris, or constructed by one of
the London hydrometer artists, the per centage of real alcohol, and the
real value of any spirituous liquor, may be determined to sufficient
nicety for most purposes, in a far easier manner than by any instruments
now used in this country. It has been adopted by the Swedish government,
with M. Gay Lussac’s tables.
M. Gay Lussac’s table gives, by inspection, the true bulk of the spirits
as corrected for temperature; that is, their volume, if of the normal
temperature of 15° Cent. (59° Fahr.). Now this is important information;
for, if a person buys 1000 gallons of spirits in hot weather, and pays
for them exactly according to their strength corrected for temperature,
he will not have 1000 gallons when the weather is in its mean state. He
may lose, in this way, several gallons without being aware of it from
his hydrometer.
Sometimes, after moist autumns, when damaged grain abounds, the alcohol
distilled from its fermented wash contains a peculiar volatile body.
When we apply our nose to this species of spirits in its hot state, the
volatile substance dissolved in it irritates the eyes and nostrils: it
has very nearly the same smell as an alcoholic solution of cyanogen, as
any chemist may discover by standing near the discharge pipe of the
refrigeratory worm of a raw-grain whisky still. Such spirits intoxicate
more strongly than pure spirits of the same strength, and excite, in
many persons, even temporary frenzy. It is a volatile fatty matter, of a
very fetid odour, when obtained by itself, as I have procured it in cold
weather at some of the great distilleries in Scotland. It does not
combine with bases. At the end of a few months, it spontaneously
decomposes in the spirits, and leaves them in a less nauseous and
noxious state. By largely diluting the spirits with water, and
distilling at a moderate temperature, the greater part of this oil may
be separated. Part of it comes over with the strongest alcohol, and part
with the latter runnings, which are called by the distillers strong and
weak feints. The intermediate portion is purer spirit. The feints are
always more or less opalescent, or become so on dilution with water, and
then throw up an oily pellicle upon their surface. The charcoals of
light wood, such as pine or willow, well calcined, and infused in
sufficient quantity with the spirits prior to rectification, will
deprive them of the greater part of that oily contamination. Animal
charcoal, well calcined, has also been found useful; but it must be
macerated for some time with the empyreumatic spirits, before
distillation. Another mode of separating that offensive oil is, to
agitate the impure spirits with a quantity of a fat oil, such as olive
oil, or oil of almonds, to decant off the oil, and re-distil the spirits
with a little water.
Some foreign chemists direct empyreumatic or rank spirits, to be
rectified with the addition of chloride of lime. I have tried this
method in every way, and on a considerable scale, but never found the
spirits to be improved by it. They were rather deteriorated. See
_Brandy_, _Distillation_, _Fermentation_, _Gin_, _Rum_, _Whisky_.
Anhydrous or absolute alcohol, when swallowed, acts as a mortal poison,
not only by its peculiar stimulus on the nervous system, but by its
abstracting the aqueous particles from the soft tissue of the stomach,
with which it comes in contact, so as to destroy its organisation.
Alcohol of 0·812 consists, by experiments, of 3 atoms of carbon, 6 of
hydrogen, and 2 of oxygen; absolute alcohol consists, probably, of 2 of
carbon, 3 of hydrogen, and 1 of oxygen.
ALE. The fermented infusion of pale malted barley, usually combined with
infusion of hops. See BEER.
ALEMBIC, a STILL; which see.
ALEMBROTH, salt of. The salt of wisdom, of the alchemists; a compound of
bichloride of mercury and sal ammoniac, from which the old white
precipitate of mercury is made.
ALGAROTH, powder of. A compound of oxide and chloride of antimony, being
a precipitate obtained by pouring water into the acidulous chloride of
that metal.
ALIZARINE. See MADDER.
ALKALI. A class of chemical bodies, distinguished chiefly by their
solubility in water, and their power of neutralising acids, so as to
form saline compounds. The alkalis of manufacturing importance are,
ammonia, potash, soda, and quinia. These alkalis change the purple
colour of red cabbage and radishes to a green, the reddened tincture of
litmus to a purple, and the colour of turmeric and many other yellow
dyes to a brown. Even when combined with carbonic acid, the first three
alkalis exercise this discolouring power, which the alkaline earths,
lime and barytes, do not. The same three alkalis have an acrid, and
somewhat urinous taste; the first two are energetic solvents of animal
matter; and the three combine with oils, so as to form soaps. They unite
with water in every proportion, and also with alcohol; and the first
three combine with water after being carbonated.
ALKALIMETER. An instrument for measuring the alkaline force or purity of
any of the alkalis of commerce. It is founded on the principle, that the
quantity of real alkali present in any sample, is proportional to the
quantity of acid which a given weight of it can neutralize. See the
individual alkalis, POTASH, and SODA.
ALKANA, is the name of the root and leaves of _Lausania inermis_, which
have been long employed in the East, to dye the nails, teeth, hair,
garments, &c. The leaves, ground and mixed with a little limewater,
serve for dyeing the tails of horses in Persia and Turkey.
ALKANET, the root of. (_Anchusa tinctoria._) A species of bugloss,
cultivated chiefly in the neighbourhood of Montpellier. It affords a
fine red colour to alcohol and oils; but a dirty red to water. Its
principal use is for colouring ointments, cheeses, and _pommades_. The
spirituous tincture gives to white marble a beautiful deep stain.
ALLIGATION. An arithmetical formula, useful, on many occasions, for
ascertaining the proportion of constituents in a mixture, when they have
undergone no change of volume by chemical action. When alcoholic liquors
are mixed with water, there is a condensation of bulk, which renders
that arithmetical rule inapplicable. The same thing holds, in some
measure, in the union of metals by fusion. See ALLOY.
ALLOY. (_Alliage_, Fr.; _Legirung_, Germ.) This term formerly signified
a compound of gold and silver, with some metal of inferior value, but it
now means any compound of any two or more metals whatever. Thus, bronze
is an alloy of copper and tin; brass, an alloy of copper and zinc; and
type metal, an alloy of lead and antimony. All the alloys possess
metallic lustre, even when cut or broken to pieces; they are opaque; are
excellent conductors of heat and electricity; are frequently susceptible
of crystallising; are more or less ductile, malleable, elastic, and
sonorous. An alloy which consists of metals differently fusible is
usually malleable in the cold, and brittle when hot, as is exemplified
with brass and gong metal.
Many alloys consist of definite or equivalent proportions of the simple
component metals, though some alloys seem to form in any proportion,
like combinations of salt or sugar with water. It is probable that
peculiar properties belong to the equivalent or atomic ratio, as is
exemplified in the superior quality of brass made in that proportion.
One metal does not alloy indifferently with every other metal, but it is
governed in this respect by peculiar affinities; thus, silver will
hardly unite with iron, but it combines readily with gold, copper, and
lead. In comparing the alloys with their constituent metals, the
following differences may be noted; in general, the ductility of the
alloy is less than that of the separate metals, and sometimes in a very
remarkable degree; on the contrary, the alloy is usually harder than the
mean hardness of its constituents. The mercurial alloys or amalgams are,
perhaps, exceptions to this rule.
The specific gravity is rarely the mean between that of each of its
constituents, but is sometimes greater and sometimes less, indicating,
in the former case, an approximation, and in the latter, a recedure, of
the particles from each other in the act of their union. The following
tables of binary alloys exhibit this circumstance in experimental
detail:--
Alloys having a density Alloys having a density
greater than the mean of less than the mean of
their constituents. their constituents.
Gold and zinc Gold and silver
Gold and tin Gold and iron
Gold and bismuth Gold and lead
Gold and antimony Gold and copper
Gold and cobalt Gold and iridium
Silver and zinc Gold and nickel
Silver and lead Silver and copper
Silver and tin Silver and lead
Silver and bismuth Iron and bismuth
Silver and antimony Iron and antimony
Copper and zinc Iron and lead
Copper and tin Tin and lead
Copper and palladium Tin and palladium
Copper and bismuth Tin and antimony
Lead and antimony Nickel and arsenic
Platinum and molybdenum Zinc and antimony.
Palladium and bismuth.
It would be hardly possible to infer the melting point of an alloy from
that of each of its constituent metals; but, in general, the fusibility
is increased by mutual affinity in their state of combination. Of this,
a remarkable instance is afforded in the fusible metal consisting of 8
parts of bismuth, 5 of lead, and 3 of tin, which melts at the heat of
boiling water or 212° Fahr., though the melting point deduced from the
mean of its components should be 514°. This alloy may be rendered still
more fusible by adding a very little mercury to it, when it forms an
excellent material for certain anatomical injections, and for filling
the hollows of carious teeth. Nor do the colours of alloys depend, in
any considerable degree, upon those of the separate metals; thus, the
colour of copper, instead of being rendered paler by a large addition of
zinc, is thereby converted into the rich-looking pinchbeck metal.
By means of alloys, we multiply, as it were, the numbers of useful
metals, and sometimes give usefulness to such as are separately of
little value. Since these compounds can be formed only by fusion, and
since many metals are apt to oxidise readily at their melting
temperature, proper precautions must be taken in making alloys to
prevent this occurrence, which is incompatible with their formation.
Thus, in combining tin and lead, rosin or grease is usually put on the
surface of the melting metals, the carbon produced by the decomposition
of which protects them, in most cases, sufficiently from oxidisement.
When we wish to combine tin with iron, as in the tinning of cast-iron
tea kettles, we rub sal ammoniac upon the surfaces of the hot metals in
contact with each other, and thus exclude the atmospheric oxygen by
means of its fumes. When there is a notable difference in the specific
gravities of the metals which we wish to combine, we often find great
difficulties in obtaining homogeneous alloys; for each metal may tend to
assume the level due to its density, as is remarkably exemplified in
alloys of gold and silver made without adequate stirring of the melting
metals. If the mass be large, and slow of cooling after it is cast in an
upright cylindrical form, the metals sometimes separate, to a certain
degree, in the order of their densities. Thus, in casting large bells
and cannons with copper alloys, the bottom of the casting is apt to
contain too much copper and the top too much tin, unless very dexterous
manipulation in mixing the fused materials have been employed
immediately before the instant of pouring out the melted mass. When such
inequalities are observed, the objects are broken and re-melted, after
which they form a much more homogeneous alloy. This artifice of a double
melting is often had recourse to, and especially in casting the alloys
for the specula of telescopes.
When we wish to alloy three or more metals, we often experience
difficulties, either because one of the metals is more oxidable, or
denser, or more fusible, than the others, or because there is no direct
affinity between two of the metals. In the latter predicament, we shall
succeed better by combining the three metals, first in pairs, for
example, and then melting the two pairs together. Thus, it is difficult
to unite iron with bronze directly; but if, instead of iron, we use tin
plate, we shall immediately succeed, and the bronze, in this manner,
acquires valuable qualities from the iron. Thus, also, to render brass
better adapted for certain purposes, a small quantity of lead ought to
be added to it, but this cannot be done directly with advantage: it is
better to melt the lead first along with the zinc, and then to add this
alloy to the melting copper, or the copper to that alloy, and fuse them
together.
We have said that the difference of fusibility was often an obstacle to
metallic combination; but this circumstance may also be turned to
advantage in decomposing certain alloys by the process called
_eliquation_. By this means silver may be separated from copper, if a
considerable quantity of lead be first alloyed with the said copper;
this alloy is next exposed to a heat just sufficient to melt the lead,
which then sweats out, so to speak, from the pores of the copper, and
carries along with it the greater part of the silver, for which it has a
strong affinity. The lead and the silver are afterwards separated from
each other, in virtue of their very different oxidability, by the action
of heat and air.
One of the alloys most useful to the arts is brass; it is more ductile
and less easily oxidised than even its copper constituent,
notwithstanding the opposite nature of the zinc. This alloy may exist in
many different proportions, under which it has different names, as
tombac, similor, pinchbeck, &c. Copper and tin form, also, a compound of
remarkable utility, known under the names of hard brass, for the bushes,
steps, and bearings of the axles, arbours, and spindles in machinery;
and of bronze, bell-metal, &c. Gold and silver, in their pure state, are
too soft and flexible to form either vessels or coins of sufficient
strength and durability; but when alloyed with a little copper, they
acquire the requisite hardness and stiffness for these and other
purposes.
When we have occasion to unite several pieces of the same or of
different metals, we employ the process called _soldering_, which
consists in fixing together the surfaces by means of an interposed
alloy, which must be necessarily more fusible than the metal or metals
to be joined. That alloy must also consist of metals which possess a
strong affinity for the substances to be soldered together. Hence each
metal would seem to require a particular kind of solder, which is, to a
certain extent, true. Thus, the solder for gold trinkets and plate is an
alloy of gold and silver, or gold and copper; that of silver trinkets,
is an alloy of silver and copper; that of copper is either fine tin, for
pieces that must not be exposed to the fire, or a brassy alloy called
hard solder, of which the zinc forms a considerable proportion. The
solder of lead and tinplate is an alloy of lead and tin, and that of tin
is the same alloy with a little bismuth. Tinning, gilding, and silvering
may also be reckoned a species of alloys, since the tin, gold, and
silver are superficially united in these cases to other metals.
Metallic alloys possess usually more tenacity than could be inferred
from their constituents; thus, an alloy of twelve parts of lead with one
of zinc has a tenacity double that of zinc. Metallic alloys are much
more easily oxidised than the separate metals, a phenomenon which may be
ascribed to the increase of affinity for oxygen which results from the
tendency of the one of the oxides to combine with the other. An alloy of
tin and lead heated to redness takes fire, and continues to burn for
some time like a piece of bad turf.
Every alloy is, in reference to the arts and manufactures, a new metal,
on account of its chemical and physical properties. A vast field here
remains to be explored. Not above sixty alloys have been studied by the
chemists out of many hundred which may be made; and of these very few
have yet been practically employed. Very slight modifications often
constitute very valuable improvements upon metallic bodies. Thus, the
brass most esteemed by turners at the lathe contains from two to three
per cent. of lead; but such brass does not work well under the hammer;
and, reciprocally, the brass which is best under the hammer is too tough
for turning.
That metallic alloys tend to be formed in definite proportions of their
constituents is clear from the circumstance that the native gold of the
auriferous sands is an alloy with silver, in the ratios of 1 atom of
silver united to 4, 5, 6, 12 atoms of gold, but never with a fractional
part of an atom. Also, in making an amalgam of 1 part of silver with 12
or 15 of mercury, and afterwards squeezing the mixture through chamois
leather, the amalgam separates into 2 parts: one, containing a small
proportion of silver and much mercury, passes through the skin; and the
other, formed of 1 of silver and 8 of mercury, is a compound in definite
proportions, which crystallises readily, and remains in the knot of the
bag. An analogous separation takes place in the tinning of mirrors; for
on loading them with the weights, a liquid amalgam of tin is squeezed
out, while another amalgam remains in a solid form composed of tin and
mercury in uniform atomic proportions. But, as alloys are generally
soluble, so to speak, in each other, this definiteness of combination is
masked and disappears in most cases.
M. Chaudet has made some experiments on the means of detecting the
metals of alloys by the cupelling furnace, and they promise useful
applications. The testing depends upon the appearances exhibited by the
metals and their alloys when heated on a cupel. Pure tin, when heated
this way, fuses, becomes of a greyish black colour, fumes a little,
exhibits incandescent points on its surface, and leaves an oxide, which,
when withdrawn from the fire, is at first lemon-yellow, but when cold,
white. Antimony melts, preserves its brilliancy, fumes, and leaves the
vessel coloured lemon-yellow when hot, but colourless when cold, except
a few spots of a rose tint. Zinc burns brilliantly, forming a cone of
oxide; and the oxide, much increased in volume, is, when hot, greenish,
but when cold, perfectly white. Bismuth fumes, becomes covered with a
coat of melted oxide, part of which sublimes, and the rest enters the
pores of the cupel; when cold, the cupel is of a fine yellow colour,
with spots of a greenish hue. Lead resembles bismuth very much; the cold
cupel is of a lemon-yellow colour. Copper melts, and becomes covered
with a coat of black oxide; sometimes spots of a rose tint remain on the
cupel.
Alloys.--Tin 75, antimony 25, melt, become covered with a coat of black
oxide, have very few incandescent points; when cold, the oxide is nearly
black, in consequence of the action of the antimony: a 1/400 part of
antimony may be ascertained in this way in the alloy. An alloy of
antimony, containing tin, leaves oxide of tin in the cupel: a 1/100 part
of tin may be detected in this way. An alloy of tin and zinc gives an
oxide which, whilst hot, is of a green tint, and resembles philosophic
wool in appearance. An alloy containing 99 tin, 1 zinc, did not present
the incandescent points of pure tin, and gave an oxide of greenish tint
when cold. Tin 95, bismuth 5 parts, gave an oxide of a grey colour. Tin
and lead give an oxide of a rusty brown colour. An alloy of lead and
tin, containing only 1 per cent. of the latter metal, when heated, does
not expose a clean surface, like lead, but is covered at times with
oxide of tin. Tin 75, and copper 25, did not melt, gave a black oxide:
if the heat be much elevated, the under part of the oxide is white, and
is oxide of tin; the upper is black, and comes from the copper. The
cupel becomes of a rose colour. If the tin be impure from iron, the
oxide produced by it is marked with spots of a rust colour.
The degree of affinity between metals may be in some measure estimated
by the greater or less facility with which, when of different degrees of
fusibility or volatility, they unite, or with which they can, after
union, be separated by heat. The greater or less tendency to separate
into differently proportioned alloys, by long-continued fusion, may also
give some information upon this subject. Mr. Hatchett remarked, in his
elaborate researches on metallic alloys, that gold made standard with
the usual precautions, by silver, copper, lead, antimony, &c., and then
cast, after long fusion, into vertical bars, was by no means an uniform
compound; but that the top of the bar, corresponding to the metal at the
bottom of the crucible, contained the larger proportion of gold. Hence,
for a more thorough combination, two red-hot crucibles should be
employed, and the liquefied metals should be alternately poured from the
one into the other. To prevent unnecessary oxidisement from the air, the
crucibles should contain, besides the metal, a mixture of common salt
and pounded charcoal. The metallic alloy should also be occasionally
stirred up with a rod of pottery ware.
The most direct evidence of a chemical change having been effected in
alloys is, when the compound melts at a lower temperature than the mean
of its ingredients. Iron, which is nearly infusible, acquires almost the
fusibility of gold when alloyed with this precious metal. The analogy is
here strong with the increase of solubility which salts acquire by
mixture, as is exemplified in the difficulty of crystallising residuums
of saline solutions, or mother waters, as they are called.
In common cases the specific gravity affords a good criterion whereby to
judge of the proportion of two metals in an alloy. But a very fallacious
rule has been given in some respectable works for computing the specific
gravity that should result from the alloying of given quantities of two
metals of known densities, supposing no chemical condensation or
expansion of volume to take place. Thus, it has been taught, that if
gold and copper be united in equal weights, the computed specific
gravity is merely the arithmetical mean between the numbers denoting the
two specific gravities. Whereas, the specific gravity of any alloy must
be computed by dividing the sum of the two weights by the sum of the two
volumes, compared, for conveniency sake, to water reckoned unity. Or, in
another form, the rule may be stated thus:--Multiply the sum of the
weights into the products of the two specific-gravity numbers for a
numerator; and multiply each specific gravity-number into the weight of
the other body, and add the two products together for a denominator. The
quotient obtained by dividing the said numerator by the denominator, is
the truly computed mean specific gravity of the alloy. On comparing with
that density, the density found by experiment, we shall see whether
expansion or condensation of volume has attended the metallic
combination. Gold having a specific gravity of 19·36, and copper of
8·87, when they are alloyed in equal weights, give, by the fallacious
rule of the arithmetical mean of the densities (19·36 + 8·87)/2 = 14·11;
whereas the rightly computed mean density is only 12·16. It is evident
that, on comparing the first result with experiment, we should be led to
infer that there had been a prodigious condensation of volume, though
expansion has actually taken place. Let W, w be the two weights; P, p
the two specific gravities, then M, the mean specific gravity, is given
by the formula--
(W + w) P p (P - p)²
M = ----------- ∴ 2Δ = - -------- =
P w + p W P + p
twice the error of the arithmetical mean; which is therefore always in
excess.
ALMOND. (_Amande_, Fr.; _Mandel_, Germ.) There are two kinds of almond
which do not differ in chemical composition, only that the bitter, by
some mysterious reaction of its constituents, generates in the act of
distillation a quantity of a volatile oil, which contains hydrocyanic
acid. Vogel obtained from bitter almonds 8·5 per cent. of husks. After
pounding the kernels, and heating them to coagulate the albumen, he
procured, by expression, 28 parts of an unctuous oil, which did not
contain the smallest particle of hydrocyanic acid. The whole of the oil
could not be extracted in this way. The expressed mass, treated with
boiling water, afforded sugar and gum, and, in consequence of the heat,
some of that acid. The sugar constitutes 6·5 per cent. and the gum 3.
The vegetable albumen extracted, by means of caustic potash, amounted to
30 parts: the vegetable fibre to only 5. The poisonous aromatic oil,
according to Robiquet and Boutron-Charlard, does not exist ready-formed
in the bitter almond, but seems to be produced under the influence of
ebullition with water. These chemists have shown that bitter almonds
deprived of their unctuous oil by the press, when treated first by
alcohol, and then by water, afford to neither of these liquids any
volatile oil. But alcohol dissolves out a peculiar white crystalline
body, without smell, of a sweetish taste at first, and afterwards
bitter, to which they gave the name of _amygdaline_. This substance does
not seem convertible into volatile oil.
Sweet almonds by the analysis of Boullay, consist of 54 parts of the
bland almond oil, 6 of uncrystallisable sugar, 3 of gum, 24 of vegetable
albumen, 24 of woody fibre, 5 of husks, 3·5 of water, 0·5 of acetic
acid, including loss. We thus see that sweet almonds contain nearly
twice as much oil as bitter almonds do.
ALMOND OIL. A bland fixed oil, obtained usually from bitter almonds by
the action of a hydraulic press, either in the cold, or aided by hot
iron plates. See OIL.
ALOE. A series of trials has been made within a few years at Paris to
ascertain the comparative strength of cables made of hemp and of the
aloe from Algiers; and they are said to have all turned to the advantage
of the aloe. Of cables of equal size, that made of aloe raised a weight
of 2,000 kilogrammes (2 tons nearly); that made of hemp, a weight of
only 400 kilogrammes. At the exposition of objects of national industry,
two years ago, in Brussels, I saw aloe cordage placarded, as being far
preferable to hempen. See ROPE.
ALUDEL. A pear-shaped vessel open at either end, of which a series are
joined for distilling mercury in Spain. See MERCURY.
ALUM. (_Alun_, Fr.; _Alaum_, Germ.) A saline body, consisting of the
earth of clay, called alumina by the chemists, combined with sulphuric
acid and potash, or sulphuric acid and ammonia, into a triple compound.
It occurs in the crystallised form of octahedrons, has an acerb subacid
taste, and reddens the blue colour of litmus or red cabbage.
Alum works existed many centuries ago at Roccha, formerly called Edessa,
in Syria, whence the ancient name of Roch alum given to this salt. It
was afterwards made at Foya Nova, near Smyrna, and in the neighbourhood
of Constantinople. The Genoese, and other trading people of Italy,
imported alum from these places into western Europe, for the use of the
dyers of red cloth. About the middle of the fifteenth century, alum
began to be manufactured at La Tolfa, Viterbo, and Volaterra, in Italy;
after which time the importation of oriental alum was prohibited by the
pope, as detrimental to the interests of his dominions. The manufacture
of this salt was extended to Germany at the beginning of the sixteenth
century, and to England at a somewhat later period, by Sir Thomas
Chaloner, in the reign of Elizabeth. In its pure state, it does not seem
to have been known to the ancients; for Pliny, in speaking of something
like plumose alum, says, that it struck a black colour with pomegranate
juice, which shows that the green vitriol was not separated from it. The
_stypteria_ of Dioscorides, and the _alumen_ of Pliny, comprehended,
apparently, a variety of saline substances, of which sulphate of iron,
as well as alumina, was probably a constituent part. Pliny, indeed,
says, that a substance called in Greek Ὑγρα, or watery, probably from
its very soluble nature, which was milk-white, was used for dyeing wool
of bright colours. This may have been the mountain butter of the German
mineralogists, which is a native sulphate of alumina, of a soft texture,
waxy lustre, and unctuous to the touch.
The only alum manufactories now worked in Great Britain, are those of
Whitby, in England, and of Hurlett and Campsie, near Glasgow, in
Scotland; and these derive the acid and earthy constituents of the salt
from a mineral called alum slate. This mineral has a bluish or
greenish-black colour, emits sulphurous fumes when heated, and acquires
thereby an aluminous taste. The alum manufactured in Great Britain
contains potash as its alkaline constituent; that made in France
contains, commonly, ammonia, either alone, or with variable quantities
of potash. Alum may in general be examined by water of ammonia, which
separates from its watery solutions its earthy basis, in the form of a
light flocculent precipitate. If the solution be dilute, this
precipitate will float long as an opalescent cloud.
If we dissolve alum in 20 parts of water, and drop this solution slowly
into water or caustic ammonia till this be nearly, but not entirely,
saturated, a bulky white precipitate will fall down, which, when
properly washed with water, is pure aluminous earth or clay, and dried
forms 10·82 per cent. of the weight of the alum. If this earth, while
still moist, be dissolved in dilute sulphuric acid, it will constitute,
when as neutral as possible, the sulphate of alumina, which requires
only two parts of cold water for its solution. If we now decompose this
solution, by pouring into it water of ammonia, there appears an
insoluble white powder, which is subsulphate of alumina, or basic alum;
and contains three times as much earth as exists in the neutral
sulphate. If, however, we pour into the solution of the neutral sulphate
of alumina a solution of sulphate of potash, a white powder will fall if
the solutions be concentrated, which is true _alum_; but if the
solutions be dilute, by evaporating their mixture, and cooling it,
crystals of alum will be obtained.
When newly precipitated alumina is boiled in a solution of alum, a
portion of the earth enters into combination with the salt, constituting
an insoluble compound, which falls in the form of a white powder. The
same combination takes place, if we decompose a boiling hot solution of
alum with a solution of potash, till the mixture appears nearly neutral
by litmus paper. This insoluble or basic alum exists native in the
alum-stone of Tolfa, near Civita Vecchia, and it consists in 100 parts
of 19·72 parts of sulphate of potash, 61·99 basic sulphate of alumina,
and 18·29 water. When this mineral is treated with a due quantity of
sulphuric acid, it dissolves, and is converted into the crystallisable
alum of commerce.
These experimental facts develope the principles of the manufacture of
alum, which is prosecuted under various modifications, for its important
uses in the arts. Alum seldom occurs ready-formed in nature;
occasionally, as an efflorescence on stones, and in certain mineral
waters in the East Indies. The alum of European commerce is fabricated
artificially, either from the alum schists or stones, or from clay. The
mode of manufacture differs according to the nature of these earthy
compounds. Some of them, such as the alum stone, contain all the
elements of the salt, but mixed with other matters, from which it must
be freed. The schists contain only the elements of two of the
constituents, namely, clay and sulphur, which are convertible into
sulphate of alumina, and this may be then made into alum by adding the
alkaline ingredient. To this class belong the alum slates, and other
analogous schists, containing brown coal.
1. _Manufacture of Alum from the Alum Stone._--The alum-stone is a rare
mineral, being found in moderate quantity at Tolfa, and in larger in
Hungary, at Bereghszasz, and Muszag, where it forms entire beds in a
hard substance, partly characterised by numerous cavities, containing
drusy crystallisations of alum-stone or basic alum. The larger lumps
contain more or fewer flints disseminated through them, and are,
according to their quality, either picked out to make alum, or are
thrown away. The sorted pieces are roasted or calcined, by which
operation apparently the hydrate of alumina, associated with the
sulphate of alumina, loses its water, and, as burnt clay, loses its
affinity for alum. It becomes, therefore, free; and during the
subsequent exposure to the weather the stone gets disintegrated, and the
alum becomes soluble in water.
The calcination is performed in common lime-kilns in the ordinary way.
In the regulation of the fire it is requisite, here, as with gypsum, to
prevent any fusion or running together of the stones, or even any
disengagement of sulphuric or sulphurous acids, which would cause a
corresponding defalcation in the product of alum. For this reason the
contact of the ignited stones with carbonaceous matter ought to be
avoided.
The calcined alum-stones, piled in heaps from 2 to 3 feet high, are to
be exposed to the weather, and meanwhile they must be continually kept
moist by sprinkling them with water. As the water combines with the alum
the stones crumble down, and fall, eventually, into a pasty mass, which
must be lixiviated with warm water, and allowed to settle in a large
cistern. The clear supernatant liquor, being drawn off, must be
evaporated, and then crystallised. A second crystallisation finishes the
process, and furnishes a marketable alum. Thus the Roman alum is made,
which is covered with a fine red film of peroxide of iron.
2. _Alum Manufacture from Alum Schist._--The greater portion of the alum
found in British commerce is made from alum-slate and analogous
minerals. This slate contains more or less iron pyrites, mixed with
coaly or bituminous matter, which is occasionally so abundant as to
render them somewhat combustible. In the strata of brown coal and
bituminous wood, where the upper layers lie immediately under clay beds,
they consist of the coaly substance rendered impure with clay and
pyrites. This triple mixture constitutes the essence of all good alum
schists, and it operates spontaneously towards the production of
sulphate of alumina. The coal serves to make the texture open, and to
allow the air and moisture to penetrate freely, and to change the
sulphur and iron present into acid and oxide. When these schists are
exposed to a high temperature in contact with air, the pyrites loses one
half of its sulphur, in the form of sublimed sulphur or sulphurous acid,
and becomes a black sulphuret of iron, which speedily attracts oxygen,
and changes to sulphate of iron, or green vitriol. The brown coal
schists contain, commonly, some green vitriol crystals spontaneously
formed in them. The sulphate of iron transfers its acid to the clay,
progressively, as the iron, by the action of the air with a little
elevation of temperature, becomes peroxidised; whereby sulphate of
alumina is produced. A portion of the green vitriol remains, however,
undecomposed, and so much the more as there may happen to be less of
other salifiable bases present in the clay slate. Should a little
magnesia or lime be present, the vitriol gets more completely
decomposed, and a portion of Epsom salt and gypsum is produced.
The manufacture of alum from alum schists may be distributed under the
six following heads:--1. The preparation of the alum slate. 2. The
lixiviation of the slate. 3. The evaporation of the lixivium. 4. The
addition of the saline ingredients, or the precipitation of the alum. 5.
The washing of the aluminous salts; and 6. The crystallisation.
1. _Preparation of the Alum Slate._--Some alum slates are of such a
nature that, being piled in heaps in the open air, and moistened from
time to time, they get spontaneously hot, and by degrees fall into a
pulverulent mass, ready to be lixiviated. The greater part, however,
require the process of ustulation, from which they derive many
advantages. The cohesion of the dense slates is thereby so much impaired
that their decomposition becomes more rapid; the decomposition of the
pyrites is quickened by the expulsion of a portion of the sulphur; and
the ready-formed green vitriol is partly decomposed by the heat, with a
transference of its sulphuric acid to the clay, and the production of
sulphate of alumina.
Such alum-slates as contain too little bitumen or coal for the roasting
process must be interstratified with layers of small coal or brushwood
over an extensive surface. At Whitby the alum rock, broken into small
pieces, is laid upon a horizontal bed of fuel, composed of brushwood;
but at Hurlett small coal is chiefly used for the lower bed. When about
four feet of the rock is piled on, fire is set to the bottom in various
parts; and whenever the mass is fairly kindled, more rock is placed over
the top. At Whitby this piling process is continued till the calcining
heap is raised to the height of 90 or 100 feet. The horizontal area is
also augmented at the same time till it forms a great bed nearly 200
feet square, having therefore about 100,000 yards of solid measurement.
The rapidity of the combustion is tempered by plastering up the crevices
with small schist moistened. When such an immense mass is inflamed, the
heat is sure to rise too high, and an immense waste of sulphur and
sulphuric acid must ensue. This evil has been noticed at the Whitby
works. At Hurlett the height to which the heap is piled is only a few
feet, while the horizontal area is expanded; which is a much more
judicious arrangement. At Whitby 130 tons of calcined schist produce on
an average 1 ton of alum. In this humid climate it would be advisable to
pile up on the top of the horizontal strata of brushwood or coal, and
schist, a pyramidal mass of schist, which having its surface plastered
smooth, with only a few air-holes, will protect the mass from the rains,
and at the same time prevent the combustion from becoming too vehement.
Should heavy rains supervene, a gutter must be scooped out round the
pile for receiving the aluminous lixivium, and conducting it into the
reservoir.
It may be observed, that certain alum schists contain abundance of
combustible matter, to keep up a suitable calcining heat after the fire
is once kindled; and therefore nothing is needed but the first layer of
brushwood, which, in this case, may be laid over the first bed of the
bituminous schist.
A continual, but very slow, heat, with a smothered fire, is most
beneficial for the ustulation of alum slate. When the fire is too brisk,
the sulphuret of iron may run with the earthy matters into a species of
slag, or the sulphur will be dissipated in vapour, by both of which
accidents the product of alum will be impaired. Those bituminous alum
schists which have been used as fuel under steam boilers have suffered
such a violent combustion that their ashes yield almost no alum. Even
the best regulated calcining piles are apt to burn too briskly in high
winds, and should have their draught-holes carefully stopped under such
circumstances. It may be laid down as a general rule, that the slower
the combustion the richer the roasted ore will be in sulphate of
alumina. When the calcination is complete, the heap diminishes to one
half its original bulk; it is covered with a light reddish ash, and is
open and porous in the interior, so that the air can circulate freely
throughout the mass. To favour this access of air, the masses should not
be too lofty; and in dry weather a little water should be occasionally
sprinkled on them, which, by dissolving away some of the saline matter,
will make the interior more open to the atmosphere.
When the calcined mineral becomes thoroughly cold, we may proceed to the
lixiviation. But as, from the first construction of the piles or beds
till their complete calcination, many weeks, or even months, may elapse,
care ought to be taken to provide a sufficient number or extent of them,
so as to have an adequate supply of material for carrying on the
lixiviating and crystallising processes during the course of the year,
or at least during the severity of the winter season, when the
calcination may be suspended, and the lixiviation becomes
unsatisfactory. The beds are known to be sufficiently decomposed by the
efflorescence of the salt which appears upon the stones, from the strong
aluminous taste of the ashes, and from the appropriate chemical test of
lixiviating an aliquot average portion of the mass, and seeing how much
alum it will yield to solution of muriate or sulphate of potash.
2. _The Lixiviation._--The lixiviation is best performed in stone-built
cisterns; those of wood, however strong at first, are soon decomposed,
and need repairs. They ought to be erected in the neighbourhood of the
calcining heaps, to save the labour of transport, and so arranged that
the solutions from the higher cisterns may spontaneously flow into the
lower. In this point of view, a sloping terrace is the best situation
for an alum work. In the lowest part of this terrace, and in the
neighbourhood of the boiling-house, there ought to be two or more large
deep tanks, for holding the crude lixivium, and they should be protected
from the rain by a proper shed. Upon a somewhat higher level the
cisterns of the clear lixivium may be placed. Into the highest range of
cisterns the calcined mineral is to be put, taking care to lay the
largest lumps at the bottom, and to cover them with lighter ashes. A
sufficient quantity of water is now to be run over it, and allowed to
rest for some time. The lixivium may then be drawn off, by a stopcock
connected with a pipe at the bottom of the cistern, and run into another
cistern at a somewhat lower level. Fresh water must now be poured on the
partly exhausted schist, and allowed to remain for a sufficient time.
This lixivium, being weak, should be run off into a separate tank. In
some cases a third addition of fresh water may be requisite, and the
weak lixivium which is drawn off may be reserved for a fresh portion of
calcined mineral. In order to save evaporation, it is always requisite
to strengthen weak leys by employing them instead of water for fresh
portions of calcined schist. Upon the ingenious disposition and form of
these lixiviating cisterns much of the economy and success of an alum
work depend. The hydrometer should be always used to determine the
degree of concentration which the solutions acquire.
The lixiviated stone being thus exhausted of its soluble ingredients, is
to be removed from the cisterns, and piled up in a heap in any
convenient place, where it may be left either spontaneously to
decompose, or, after drying, may be subjected to another calcination.
The density of the solution may be brought, upon an average, up to the
sp. gr. of from 1·09 to 1·15. The latter density may always be obtained
by pumping up the weaker solutions upon fresh calcined _mine_. This
strong liquor is then drawn off, when the sulphate of lime, the oxide of
iron, and the earths are deposited. It is of advantage to leave the
liquor exposed for some time, whereby the green vitriol may pass into a
persulphate of iron with the deposition of some oxide, while the
liberated acid may combine with some of the clay present, so as to
increase the quantity of sulphate of alumina. The manufacture of alum is
the more imperfect, as the quantity of sulphate of iron left
undecomposed is greater, and therefore every expedient ought to be tried
to convert the sulphate of iron into sulphate of alumina.
3. _The evaporation of the Schist Lixivium._--As the aluminous liquors,
however well settled at first, are apt, on the great scale, to deposit
earthy matters in the course of their concentration by heat, they are
best evaporated by a surface fire, such as that employed at Hurlett and
Campsie. A water-tight stone cistern must be built, having a layer of
well rammed clay behind the flags or tiles which line its bottom and
sides. This cistern may be 4 or 6 feet wide, 2 or 3 feet deep, and 30 or
40 feet long, and it is covered in by an arch of stone or brickwork. At
one extremity of this tunnel, or covered canal, a fire-grate is set, and
at the other a lofty chimney is erected. The cistern being filled to the
brim with the alum ley, a strong fire is kindled in the reverberatory
grate, and the flame and hot air are forced to sweep along the surface
of the liquor, so as to keep it in constant ebullition, and to carry off
the aqueous parts in vapour. The soot which is condensed in the process
falls to the bottom, and leaves the body of the liquor clear. As the
concentration goes on, more of the rough lixivium is run in from the
settling cistern, placed on a somewhat higher level, till the whole gets
charged with a clear liquor of a specific gravity sufficiently high for
transferring into the proper lead boilers.
At Whitby, the lead pans are 10 feet long, 4 feet 9 inches wide, 2 feet
2 inches deep at the one end, and 2 feet 8 inches deep at the other.
This increase of depth and corresponding slope, facilitates the
decantation of the concentrated lixivium by means of a syphon, applied
at the lower end. The bottom of the pan is supported by a series of
parallel iron bars, placed very near each other. In these lead pans the
liquor is concentrated, at a brisk boiling heat, by means of the flame
of a flue beneath them. Every morning the pans are emptied into a
settling cistern of stone or lead. The specific gravity of the liquor
should be about 1·4 or 1·5, being a saturated solution of the saline
matters present. The proper degree of density must vary, however, with
different kinds of lixivia, and according to the different views of the
manufacturer. For a liquor which consists of two parts of sulphate of
alumina, and one part of sulphate of iron, a specific gravity of 1·25
may be sufficient; but for a solution which contains two parts of
sulphate of iron to one of sulphate of alumina, so that the green
vitriol must be withdrawn first of all by crystallisation, a specific
gravity of 1·4 may be requisite.
The construction of an evaporating furnace well adapted to the
concentration of aluminous and other crude lixivia, is described under
SODA. The liquor basin may be made of tiles or flags puddled in clay,
and secured at the seams with a good _hydraulic_ cement. A mortar made
of quicklime mixed with the exhausted schist in powder, and iron
turnings, is said to answer well for this purpose. Sometimes over the
reverberatory furnace a flat pan is laid, instead of the arched top,
into which the crude liquor is put for neutralisation and partial
concentration. In Germany, such a pan is made of copper, because iron
would waste too fast, and lead would be apt to melt. From this
preparation basin the under evaporating trough is gradually supplied
with hot liquor. At one side of this lower trough, there is sometimes a
door, through which the sediment may be raked out as it accumulates upon
the bottom. Such a contrivance is convenient for this mode of
evaporation, and it permits, also, any repairs to be readily made; but,
indeed, an apparatus of this kind, well mounted at first, will serve for
many years.
In the course of the final concentration of the liquors, it is customary
to add some of the mother waters of a former process, the quantity of
which must be regulated by a proper analysis and knowledge of their
contents. If these mother waters contain much free sulphuric acid, from
the peroxidation of their sulphate of iron, they may prove useful in
dissolving a portion of the alumina of the sediment which is always
present in greater or less quantity.
4. _The precipitation of the Alum by adding Alkaline Salts._--As a
general rule, it is most advantageous to separate, first of all, from
the concentrated clear liquors, the alum in the state of powder or small
crystals, by addition of the proper alkaline matter, and to leave the
mingled foreign salts, such as the sulphate of iron or magnesia, in
solution, instead of trying to abstract these salts by a previous
crystallisation. In this way we not only simplify and accelerate the
manufacture of alum, and leave the mother waters to be worked up at any
convenient season, but we also avoid the risk of withdrawing any of the
sulphate of alumina with the sulphate of iron or magnesia. On this
account, the concentration of the liquor ought not to be pushed so far
as that, when it gets cold, it should throw out crystals, but merely to
the verge of this point. This density may be determined by suitable
experiments.
The clear liquor should now be run off into the precipitation cistern,
and have the proper quantity of sulphate or muriate of potash, or impure
sulphate or carbonate of ammonia added to it. The sulphate of potash,
which is the best precipitant, forms 18·34 parts out of 100 of
crystallised alum; and therefore that quantity of it, or its equivalent
in muriate of potash, or other potash or ammoniacal salts, must be
introduced into the aluminous liquor. Since sulphate of potash takes 10
parts of cold water to dissolve it, but is much more soluble in boiling
water, and since the precipitation of alum is more abundant the more
concentrated the mingled solutions are, it would be prudent to add the
sulphate solution as hot as may be convenient; but, as muriate of potash
is fully three times more soluble in cold water, it is to be preferred
as a precipitant, when it can be procured at a cheap rate. It has, also,
the advantage of decomposing the sulphate of iron present into a
muriate, a salt very difficult of crystallisation, and, therefore, less
apt to contaminate the crystals of alum. The quantity of alkaline salts
requisite to precipitate the alum, in a granular powder, from the
lixivium, depends on their richness in potash or ammonia, on the one
hand, and on the richness of the liquors in sulphate of alumina on the
other; and it must be ascertained, for each large quantity of product,
by a preliminary experiment in a precipitation glass. Here, an aliquot
measure of the aluminous liquor being taken, the liquid precipitant must
be added in successive portions, as long as it causes any cloud, when
the quantity added will be indicated by the graduation of the vessel. A
very exact approximation is not practicable upon the great scale; but,
as the mother waters are afterwards mixed together in one cistern, any
excess of the precipitant, at one time, is corrected by excess of
aluminous sulphate at another, and the resulting alum meal is collected
at the bottom. When the precipitated saline powder is thoroughly settled
and cooled, the supernatant mother water must be drawn off by a pump, or
rather a syphon or stopcock, into a lower cistern. The more completely
this drainage is effected, the more easily and completely will the alum
be purified.
This mother liquor has, generally, a specific gravity of 1·4 at a medium
temperature of the atmosphere, and consists of a saturated solution of
sulphate or muriate of black and red oxide of iron, with sulphate of
magnesia, in certain localities, and muriate of soda, when the soaper’s
salt has been used as a precipitant, as also a saturated solution of
sulphate of alumina. By adding some of it, from time to time, to the
fresh lixivia, a portion of that sulphate is converted into alum; but,
eventually, the mother water must be evaporated, so as to obtain from it
a crop of ferruginous crystals; after which it becomes capable, once
more, of giving up its alum to the alkaline precipitants.
When the aluminous lixivia contain a great deal of sulphate of iron, it
may be good policy to withdraw a portion of it by crystallisation before
precipitating the alum. With this view, the liquors must be evaporated
to the density of 1·4, and then run off into crystallising stone
cisterns. After the green vitriol has concreted, the liquor should be
pumped back into the evaporating pan, and again brought to the density
of 1·4. On adding to it, now, the alkaline precipitants, the alum will
fall down from this concentrated solution, in a very minute crystalline
powder, very easy to wash and purify. But this method requires more
vessels and manipulation than the preceding, and should only be had
recourse to from necessity; since it compels us to carry on the
manufacture of both the valuable alum and the lower priced salts at the
same time; moreover, the copperas extracted at first from the schist
liquors carries with it, as we have said, a portion of the sulphate of
alumina, and acquires thereby a dull aspect; whereas the copperas
obtained after the separation of the alum is of a brilliant appearance.
5. _The washing, or edulcoration, of the Alum Powder._--This crystalline
pulverulent matter has a brownish colour, from the admixture of the
ferruginous liquors; but it may be freed from it by washing with very
cold water, which dissolves not more than one sixteenth of its weight of
alum. After stirring the powder and the water well together, the former
must be allowed to settle, and then the washing must be drawn off. A
second washing will render the alum nearly pure. The less water is
employed, and the more effectually it is drained off, the more complete
is the process. The second water may be used in the first washing of
another portion of alum powder, in the place of pure water. These
washings may be added to the schist lixivia.
6. _The crystallisation._--The washed alum is put into a lead pan, with
just enough water to dissolve it at a boiling heat; fire is applied, and
the solution is promoted by stirring. Whenever it is dissolved in a
saturated state, it is run off into the crystallising vessels, which are
called _roching_ casks. These casks are about five feet high, three feet
wide in the middle, somewhat narrower at the ends; they are made of very
strong staves, nicely fitted to each other, and held together by strong
iron hoops, which are driven on _pro tempore_, so that they may be
easily knocked off again, in order to take the staves asunder. The
concentrated solution, during its slow cooling in these close vessels,
forms large regular crystals, which hang down from the top, and project
from the sides, while a thick layer or cake lines the whole interior of
the cask. At the end of eight or ten days, more or less, according to
the weather, the hoops and staves are removed, when a cask of apparently
solid alum is disclosed to view. The workman now pierces this mass with
a pickaxe at the side near the bottom, and allows the mother water of
the interior to run off on the sloping stone floor into a proper
cistern, whence it is taken and added to another quantity of washed
powder to be crystallised with it. The alum is next broken into lumps,
exposed in a proper place to dry, and is then put into the finished bing
for the market. There is sometimes a little insoluble basic alum
(subsulphate) left at the bottom of the cask. This being mixed with the
former mother liquors, gets sulphuric acid from them; or, being mixed
with a little sulphuric acid, it is equally converted into alum.
When, instead of potash or its salts, the ammoniacal salts are used, or
putrid urine, with the aluminous lixivia, ammoniacal alum is produced,
which is perfectly similar to the potash alum in its appearance and
properties. At a gentle heat both lose their water of crystallisation,
amounting to 45-1/2 per cent. for the potash alum, and 48 for the
ammoniacal. The quantity of acid is the same in both, as, also, very
nearly the quantity of alumina, as the following analyses will show:
Potash alum. Ammonia alum.
Sulphate of potash 18·34 Sulphate of ammonia 12·88
Sulphate of alumina 36·20 Sulphate of alumina 38·64
Water 45·46 Water 48·48
------ ------
100·00 100·00
------ ------
Or otherwise, Potash alum. Ammonia alum.
1 atom sulphate of potash 1089·07 1 atom sulphate of ammonia 716·7
1 alumina 2149·80 1 alumina 2149·8
24 water 2669·52 24 water 2699·5
------- ------
5938·39 5566·0
------- ------
Or, Potash alum. Ammonia alum.
Alumina 10·82 Alumina 11·90
Potash 9·94 Ammonia 3·89
Sulphuric Acid 33·77 Sulphuric acid 36·10
Water 45·47 Water 48·11
------ ------
100·00 100·00
------ ------
When heated pretty strongly, the ammoniacal alum loses its sulphuric
acid and ammonia, and only the earth remains. This is a very convenient
process for procuring pure alumina. Ammoniacal alum is easily
distinguished from the other by the smell of ammonia which it exhales
when triturated with quicklime. The Roman alum, made from alum stone,
possesses most of the properties of the schist-made alums, but it has a
few peculiar characters: it crystallises always in opaque cubes, whereas
the common alum crystallises in transparent octahedrons. It is probable
that Roman alum is a sulphate of alumina and potash, with a slight
excess of the earthy ingredient. It is permanent when dissolved in cold
water; for after a slow evaporation it is recovered in a cubical form.
But when it is dissolved in water heated to 110° Fahr. and upwards, or
when its solution is heated above this pitch, subsulphate of alumina
falls, and on evaporation octahedral crystals of common alum are
obtained. The exact composition of the Roman alum has not been
determined, as far as I know. It probably differs from the other also in
its water of crystallisation. The Roman alum contains, according to MM.
Thenard and Roard, only 1/2200 of sulphate of iron, while the common
commercial alums contain 1/1000. It may be easily purified by solution,
granulation, crystallisation, and washing, as has been already
explained.
Alum is made extensively in France from an artificial sulphate of
alumina. For this purpose clays are chosen as free as possible from
carbonate of lime and oxide of iron. They are calcined in a
reverberatory furnace, in order to expel the water, to peroxidise the
iron, and to render the alumina more easily acted on by the acid. The
expulsion of the water renders the clay porous and capable of absorbing
the sulphuric acid by capillary attraction. The peroxidation of the iron
renders it less soluble in the sulphuric acid; and the silica of the
clay, by reacting on the alumina, impairs its aggregation, and makes it
more readily attracted by the acid. The clay should, therefore, be
moderately calcined; but not so as to indurate it like pottery ware, for
it would then suffer a species of siliceous combination which would make
it resist the action of acids. The clay is usually calcined in a
reverberatory furnace, the flame of which serves thereafter to heat two
evaporating pans and a basin for containing a mixture of the calcined
clay and sulphuric acid. As soon as the clay has become friable in the
furnace it is taken out, reduced to powder, and passed through a fine
sieve. With 100 parts of the pulverised clay, 45 parts of sulphuric
acid, of sp. gr. 1·45, are well mixed, in a stone basin, arched over
with brickwork. The flame and hot air of a reverberatory furnace are
made to play along the mixture, in the same way as described for
evaporating the schist liquors. See SODA. The mixture, being stirred
from time to time, is, at the end of a few days, to be raked out, and to
be set aside in a warm place, for the acid to work on the clay, during
six or eight weeks. At the end of this time it must be washed, to
extract the sulphate of alumina. With this view, it may be treated like
the roasted alum ores above described. If potash alum is to be formed,
this sulphate of alumina is evaporated to the specific gravity of 1·38;
but if ammonia alum, to the specific gravity of only 1·24; because the
sulphate of ammonia, being soluble in twice its weight of water, will
cause a precipitation of pulverulent alum from a weaker solution of
sulphate of alumina than the less soluble sulphate of potash could do.
The alum stone, from which the Roman alum is made, contains potash. The
following analysis of _alunite_, by M. Cordier, places this fact in a
clear light:--
Sulphate of potash 18·53
Sulphate of alumina 38·50
Hydrate of alumina 42·97
------
100·00
------
To transform this compound into alum, it is merely necessary to abstract
the hydrate of alumina. The ordinary alum stone, however, is rarely so
pure as the above analysis would seem to show; for it contains a mixture
of other substances; and the above are in different proportions.
Alum is very extensively employed in the arts, most particularly in
dyeing, lake making, dressing sheep-skins, pasting paper, in clarifying
liquors, &c. Its purity for the dyer may be tested by prussiate of
potash, which will give solution of alum a blue tint in a few minutes if
it contain even a very minute portion of iron. A bit of nut-gall is also
a good test of iron.
AMADOU. The French name of the spongy combustible substance, called in
German _zunderschwamm_, prepared from a species of agaric, the _boletus
igniarius_, a kind of mushroom, which grows on the trunks of old oaks,
ashes, beeches, &c. It must be plucked in the months of August and
September. It is prepared by removing the outer bark with a knife, and
separating carefully the spongy substance of a yellow brown colour,
which lies within it, from the ligneous matter below. This substance is
cut into thin slices, and beat with a mallet to soften it, till it can
be easily pulled asunder between the fingers. In this state the
_boletus_ is a valuable substance for stopping oozing hemorrhages, and
some other surgical purposes. To convert it into tinder it must receive
a finishing preparation, which consists in boiling it in a strong
solution of nitre; drying it, beating it anew, and putting it a second
time into the solution. Sometimes, indeed, to render it very
inflammable, it is imbued with gunpowder, whence the distinction of
black and brown amadou.
All the puff balls of the lycopodium genus of plants, which have a
fleshy or filamentous structure, yield a tinder quite ready for soaking
in gunpowder water. The Hindoos employ a leguminous plant, which they
call _solu_, for the same purpose. Its thick spongy stem, being reduced
to charcoal, takes fire like amadou.
AMALGAM. When mercury is alloyed with any metal, the compound is called
an amalgam of that metal; as, for example, an amalgam of tin, bismuth,
&c.
AMALGAMATION. This is a process used extensively in extracting silver
and gold from certain of their ores, founded on the property which
mercury has to dissolve these metals as disseminated in the minerals,
and thus to separate them from the earthy matters. See MERCURY,
METALLURGY, and SILVER.
AMBER. (_Succin_, Fr.; _Bernstein_, Germ.) A mineral solid, of a yellow
colour of various shades, which burns quite away with flame, and
consists of carbon, hydrogen, and oxygen, in nearly the same
proportions, and the same state of combination, as vegetable resin. Its
specific gravity varies, by my trials, from 1·080 to 1·085. It becomes
negatively and powerfully electrical by friction. When applied to a
lighted candle it takes fire, swells considerably, and exhales a white
smoke of a pungent odour; but does not run into drops. Copal, which
resembles it in several respects, differs in being softer, and in
melting into drops at the flame; and mellite, or honey-stone, which is a
mineral of a similar colour, becomes white when laid on a red-hot coal.
The texture of amber is resino-vitreous, its fracture conchoidal, and
lustre glassy. It is perfectly homogeneous; sufficiently hard to scratch
gypsum, and to take a fine polish. It is, however, scratched by
calcareous spar. When amber is distilled in a retort, crystalline
needles of succinic acid sublime into the dome, and oil of amber drops
from the beak into the receiver. Fossil resins, such as that of
Highgate, found in the London clay formation, do not afford succinic
acid by heat; nor does copal. Amber is occasionally found of a whitish
and brownish colour.
The most interesting fact relative to this vegeto-mineral is its
geological position, which is very characteristic and well determined.
It is found almost uniformly in separate nodules, disseminated in the
sand, clay, or fragments of lignite of the plastic clay, and lignite
formation, situated between the _calcaire grossier_ (crag limestone) of
the tertiary strata above, and the white chalk below. The size of these
nodules varies from a nut to a man’s head; but this magnitude is very
rare in true amber. It does not occur either in continuous beds, like
the chalk flints, nor in veins; but it lies at one time in the earthy or
friable strata, which accompany or include the lignites; at another,
entangled in the lignites themselves; and is associated with the
minerals which constitute this formation, principally the pyrites, the
most abundant of all. The pieces of amber found in the sands, and other
formations evidently alluvial, those met with on the sea-coasts of
certain countries, and especially Pomerania, come undoubtedly from the
above geological formation; for the organic matters found still adhering
to the amber leave no doubt as to its primitive place. Amber does not,
therefore, belong to any postdiluvian or modern soil, since its native
bed is covered by three or four series of strata, often of considerable
thickness, and well characterised; proceeding upwards from the plastic
clay which includes the amber: these are, the crag limestone, the bone
gypsum, with its marls, the marly limestone, the upper marl sandstone,
which covers it, and, lastly, the freshwater or lacustrine formation,
often so thick, and composed of calcareous and siliceous rocks.
The amber bed is not, however, always covered with all these strata; and
it is even rare to see a great mass of one of them above the ground
which contains it; because, were it buried under such strata, it would
be difficult to meet with such circumstances as would lay it
spontaneously open to the day. But by comparing observations made in
different places, relatively to the patches of these formations, which
cover the amber deposits, we find that no other mineral formations have
been ever seen among them except those above detailed, and thus learn
that its geological locality is completely determined.
The proper yellow amber, therefore, or the Borussic, from the country
where it has been most abundantly found, belongs to the plastic clay
formation, intermediate, in England, between the chalk and the London
clay. It is sometimes interposed in thin plates between the layers of
the lignites, but more towards the bark of the fibrous lignites, which
retain the form of the wood, than towards the middle of the trunk of the
tree; a position analogous to that of the resinous matters in our
existing ligneous vegetables. The fibrous lignites which thus contain
amber belong to the dicotyledinous woods. Hence that substance seems to
have been formed during the life of the vegetable upon which it is now
encrusted. It must be remembered that the grounds containing the amber
are often replete with the sulphates of iron, alumina, and lime, or at
least with the pyritous elements of these salts. Some specimens of amber
have a surface figured with irregular meshes, indicating a sort of
shrinkage from consolidation, and consequently a matter that was at one
time fluid, viscid, or merely soft. From optical examination, Dr.
Brewster has concluded amber to be of vegetable origin.
The different bodies included in the amber, distinguishable from its
transparence, demonstrate, indeed, in the most convincing manner, its
primitive state of liquidity or softness. These bodies have long
exercised the skill of naturalists. They are generally insects, or
remains of insects, and sometimes leaves, stalks, or other portions of
vegetables. Certain families of insects occur more abundantly than
others. Thus the _hymenoptera_, or insects with four naked membranaceous
wings, as the bee and wasp, and the _diptera_, or insects with two
wings, as gnats, flies, gadflies, &c.; then come the spider tribe; some
_coleoptera_ (insects with crustaceous shells or elytra, which shut
together, and form a longitudinal suture down the back,) or beetles,
principally those which live on trees; such as the _elaterides_, or
leapers, and the _chrysomelida_. The lepidoptera, or insects with four
membranaceous wings, and pterigostea covered with mail-like scales, are
very rare in amber. We perceive from this enumeration, which results
from the labours of Germar, Schweiger, &c., that the insects enveloped
in this resinous matter are in general such as sit on the trunks of
trees, or live in the fissures of their bark. Hitherto, it has not been
found possible to refer them to any living species; but it has been
observed in general that they resemble more the insects of hot climates
than those of the temperate zones.
The districts where amber occurs in a condition fit for mining
operations are not numerous; but those in which it is met with in small
scattered bits are very abundant. Its principal exploitation is in
Eastern Prussia, on the coasts of the Baltic sea, from Memel to
Dantzick, particularly in the neighbourhood of Konigsberg, along the
shore which runs north and south from Grossdirschheim to Pillau, and in
several other places near Dantzick.
It is collected upon this coast in several ways; 1. In the beds of small
streams which run near the villages, and in rounded fragments without
bark, or in the sand-banks of rivers, in pieces thrown back by the sea,
and rounded by the waves. 2. If the pieces thrown up by the waters are
not numerous, the fishers, clothed in a leather dress, wade into the sea
up to the neck, seek to discover the amber by looking along its surface,
and seize it with bag nets, hung at the end of very long poles. They
conclude that a great deal of amber has been detached from the cliffs by
the sea, when many pieces of lignite (wood coal) are seen afloat. This
mode of collecting amber is not free from danger, and the fishers,
therefore, advance in troops, to lend each other aid in case of
accident; but their success, even thus, is most precarious. 3. The third
method of searching for amber is a real mining operation: it consists in
digging pits upon the borders of the sandy downs, sometimes to a depth
of more than 130 feet. 4. The last mode is by exploring the precipitous
sea cliffs in boats, and detaching masses of loose soil from them with
long poles terminating in iron hooks; a very hazardous employment. They
search the cliffs with great care at the level, where the amber nodules
commonly lie, and loosen the seams with their hooks; in which business
the boats are sometimes broken against the precipices, or sunk by an
avalanche of rubbish.
Amber occurs in Sicily, disseminated in beds of clay and marl, which lie
below the crag limestone. It is accompanied with bitumen; and, though a
scanty deposit, it is mined for sale. The pieces are coated with a kind
of whitish bark, present a variety of colours, and include many insects.
Amber is found in a great many places in the sandy districts of Poland,
at a very great distance from the sea, where it is mixed with cones of
the pine. In Saxony it is met with in the neighbourhood of Pretsch and
Wittemberg, in a bituminous clay mingled with lignite. At the embouchure
of the Jenissey, in Siberia, it occurs likewise along with lignite; as
also in Greenland.
Fine amber is considerably valued for making ornamental objects, and the
coarser kinds for certain uses in chemistry, medicine, and the arts. The
oriental nations prize more highly than the people of Europe trinkets
made of amber; and hence the chief commerce of the Pomeranian article is
with Turkey. The Prussian government is said to draw an annual revenue
of 17,000 dollars from amber. A good piece of a pound weight fetches 50
dollars. A mass weighing 13 pounds was picked up not long since in
Prussia, for which 5000 dollars were offered, and which would bring, in
the opinion of the Armenian merchants, from 30,000 to 40,000 dollars at
Constantinople. At one time it was customary to bake the opaque pieces
of amber in sand, at a gentle heat, for several hours, in order to make
it transparent, or to digest it in hot rapeseed oil, with the same view;
but how far these processes were advantageous does not appear.
When amber is to be worked into trinkets, it is first split on a leaden
plate at a lathe (see GEMS, _Cutting of_), and then smoothed into shape
on a Swedish whetstone. It is polished on the lathe with chalk and
water, or vegetable oil, and finished by friction with flannel. In these
processes the amber is apt to become highly electrical, very hot, and
even to fly into fragments. Hence, the artists work the pieces time
about, so as to keep each of them cool, and feebly excited. The men are
often seized with nervous tremors in their wrists and arms from the
electricity. Pieces of amber may be neatly joined by smearing their
edges with linseed oil, and pressing them strongly together, while they
are held over a charcoal fire. Solid specimens of amber, reported to
have been altogether fused by a particular application of heat, are now
shown in the royal cabinet of Dresden.
A strong and durable _varnish_ is made by dissolving amber in drying
linseed oil. For this purpose, however, the amber must be previously
heated in an iron pot, over a clear red fire, till it soften and be
semi-liquefied. The oil, previously heated, is to be now poured in, with
much stirring, in the proportion of 10 ounces to the pound of amber;
and after the incorporation is complete, and the liquid somewhat cooled,
a pound of oil of turpentine must be added. Some persons prescribe 2
ounces of melted shellac, though by this means they are apt to deepen
the colour, already rendered too dark by the roasting.
The fine black varnish of the coachmakers is said to be prepared by
melting 16 ounces of amber in an iron pot, adding to it half a pint of
drying linseed oil, boiling hot, of powdered resin and asphaltum 3
ounces each: when the materials are well united, by stirring over the
fire, they are to be removed, and, after cooling for some time, a pint
of warm oil of turpentine is to be introduced.
The _oil of amber_ enters into the composition of the old perfume called
_eau de luce_; and is convertible, by the action of a small quantity of
strong nitric acid, into a viscid mass like shoemakers’ rosin, which has
a strong odour of musk, and, under the name of artificial musk, has been
prescribed, in alcoholic solution, as a remedy against hooping cough,
and other spasmodic diseases.
Acid of amber (_succinic acid_) is a delicate reagent, in chemistry, for
separating red oxide of iron from compound metallic solutions.
AMBERGRIS. (_Ambregric_, Fr.; _Ambra_, Germ.).--A morbid secretion of
the liver of the spermaceti whale (physeter macrocephalus), found
usually swimming upon the sea. It occurs upon the coasts of Coromandel,
Japan, the Moluccas, and Madagascar, and has sometimes been extracted
from the rectum of whales in the South Sea fishery. It has a gray-white
colour, often with a black streak, or is marbled, yellow and black; has
a strong but rather agreeable smell, a fatty taste, is lighter than
water, melts at 60° C. (140° F.), dissolves readily in absolute alcohol,
in ether, and in both fat and volatile oils. It contains 85% of the
fragrant substance called _ambreine_. This is extracted from ambergris
by digestion with alcohol of 0·827, filtering the solution, and leaving
it to spontaneous evaporation. It is thus obtained in the form of
delicate white tufts: which are convertible into ambreic acid by the
action of nitric acid. Ambergris is used in perfumery.
AMIANTHUS. A mineral in silky filaments, called also ASBESTUS.
AMMONIA. A chemical compound, called also _volatile alkali_. This
substance, in its purest state, is a highly pungent gas, possessed of
all the mechanical properties of the air, but very condensable with
water. It consists of 3 volumes of hydrogen and 1 of azote condensed
into two volumes; and hence its density is 0·591, atmospheric air being
1·000. By strong compression and refrigeration it may be liquefied into
a fluid, whose specific gravity is 0·76 compared to water 1·000.
Ammonia gas is composed by weight of 82·53 azote and 17·47 hydrogen in
100 parts. It is obtained by mixing muriate of ammonia, commonly called
sal ammoniac, with quicklime, in a retort or still, applying a moderate
heat, and receiving the gas either over mercury for chemical
experiments, or in water to make liquid ammonia for the purposes of
medicine and the arts. Woulfe’s apparatus is commonly employed for this
condensation.
Ammonia is generated in a great many operations, and especially in the
decomposition of many organic substances, by fire or fermentation. Urine
left to itself for a few days is found to contain much carbonate of
ammonia, and hence this substance was at one time collected in great
quantities for the manufacture of certain salts of ammonia, and is still
used for its alkaline properties in making alum, scouring wool, &c. When
woollen rags, horns, bones, and other animal substances are decomposed
in close vessels by fire, they evolve a large quantity of ammonia, which
distils over in the form of a carbonate. The main source of ammonia now
in this country, for commercial purposes, is the coal gas works. A large
quantity of watery fluid is condensed in their tar pits, which contains,
chiefly ammonia combined with sulphuretted hydrogen and carbonic acid.
When this water is saturated with muriatic acid and evaporated it yields
muriate of ammonia, or sal ammoniac, somewhat impure, which is
afterwards purified by sublimation. See CARBONATE OF AMMONIA and SAL
AMMONIAC.
The soot of chimnies where coal is burned contains both sulphate and
carbonate of ammonia, and was extensively employed, at one time, to
manufacture these salts.
In making water of ammonia on the great scale, a cast iron still should
be preferred, and equal weights of quicklime and sal ammoniac should be
brought to the consistence of a pap, with water, before the heat is
applied. In this case, a refrigeratory worm or globe should be
interposed between the adopter tube of the capital of the still and the
bottles of Woulfe’s apparatus. The muriate of lime, or chloride of
calcium, which is left in the still when the whole ammonia is expelled,
is of no value. Water is capable of condensing easily about one third of
its weight of ammonia gas, or 460 times its bulk. The following table of
the quantity of ammonia in 100 parts by weight of its aqueous
combinations, at successive densities, is the result of very careful
experiments made by me, and recorded in the Philosophical Magazine for
March, 1821.
_Table of Water of Ammonia or Volatile Alkali, by Dr. Ure._
+------+-------+------+-----------+--------+-------------------------+
|Water |Ammonia|Water | Specific | Mean | |
| of | in | in |gravity by |specific| Equivalent primes. |
|0·900.| 100. | 100. |experiment.|gravity.| |
+------+-------+------+-----------+--------+-------------------------+
| 100 |26·500 |73·500| 0·9000 | | |
| 95 |25·175 |74·825| 0·9045 |0·90452 | _Wat. Am._|
| 90 |23·850 |76·150| 0·9090 |0·90909 | 24 + 76, 6 to 1 |
| 85 |22·525 |77·475| 0·9133 |0·91370 | |
| 80 |21·200 |78·800| 0·9177 |0·91838 | 21·25 + 78·75, 7 to 1 |
| 75 |19·875 |80·125| 0·9227 |0·92308 | |
| 70 |18·550 |81·450| 0·9275 |0·92780 | 19·1 + 80·9, 8 to 1 |
| 65 |17·225 |82·775| 0·9320 |0·93264 | 17·35 + 82·65, 9 to 1 |
| 60 |15·900 |84·100| 0·9363 |0·93750 | 15·9 + 84·1, 10 to 1 |
| 55 |14·575 |85·425| 0·9410 |0·94241 | 14·66 + 85·34, 11 to 1 |
| 50 |13·250 |86·750| 0·9455 |0·94737 | 13·60 + 86·40, 12 to 1 |
| 45 |11·925 |88·075| 0·9510 |0·95238 | 11·9 + 88·1, 14 to 1 |
| 40 |10·600 |89·400| 0·9564 |0·95744 | 11·2 + 88·8, 15 to 1 |
| 35 | 9·275 |90·725| 0·9614 |0·96256 | |
| 30 | 7·950 |92·050| 0·9662 |0·96774 | 8·63 + 91·37, 20 to 1 |
| 25 | 6·625 |93·375| 0·9716 |0·97297 | 7 + 93, 25 to 1 |
| 20 | 5·300 |94·700| 0·9768 |0·97826 | 6 + 94, 30 to 1 |
| 15 | 3·975 |96·025| 0·9828 |0·98360 | 4·5 + 95·5, 40 to 1 |
| 10 | 2·650 |97·350| 0·9887 |0·98900 | 3 + 97, 60 to 1 |
| 5 | 1·325 |98·675| 0·9945 |0·99447 | |
+------+-------+------+-----------+--------+-------------------------+
AMMONIAC, gum-resin. This is the inspissated juice of an umbelliferous
plant (the _dorema armeniacum_) which grows in Persia. It comes to us
either in small white tears clustered together, or in brownish lumps,
containing many impurities. It possesses a peculiar smell, somewhat like
that of assafœtida, and a bitterish taste. It is employed in medicine.
Its only use in the arts is for forming a cement to join broken pieces
of china and glass, which may be prepared as follows: Take isinglass 1
ounce, distilled water 6 ounces, boil together down to 3 ounces, and add
1-1/2 ounce of strong spirit of wine;--boil this mixture for a minute or
two; strain it; add, while hot, first, half an ounce of a milky emulsion
of gum ammoniac, and then five drams of an alcoholic solution of resin
mastic. This resembles a substance sold in the London shops, under the
name of _diamond cement_. The recipe was given me by a respectable
dispensing chemist.
AMORPHOUS. _Without shape._ Said of mineral and other substances which
occur in forms not easy to be defined.
ANALYSIS. The art of resolving a compound substance or machine into its
constituent parts. Every manufacturer should so study this art, in the
proper treatises, and schools of Chemistry or Mechanics, as to enable
him properly to understand and regulate his business.
[Illustration: 6]
ANCHOR. (_Ancre_, Fr.; _Anker_, Germ.) An iron hook of considerable
weight and strength, for enabling a ship to lay hold of the ground, and
fix itself in a certain situation by means of a rope called the cable.
It is an instrument of the greatest importance to the navigator, since
upon its taking and keeping hold depends his safety upon many
occasions, especially near a lee shore, where he might be otherwise
stranded or shipwrecked. Anchors are generally made of wrought iron,
except among nations who cannot work this metal well, and who therefore
use copper. The mode in which an anchor operates will be understood from
inspection of _fig._ 6., where, from the direction of the strain, it is
obvious that the anchor cannot move without ploughing up the ground in
which its hook or fluke is sunk. When this, however, unluckily takes
place, from the nature of the ground, from the mode of insertion of the
anchor, or from the violence of the winds or currents, it is called
_dragging the anchor_. When the hold is good, the cable or the buried
arm will sooner break than the ship will drive. Anchors are of different
sizes, and have different names, according to the purposes they serve;
thus there are, _sheet_, _best bower_, _small bower_, _spare_, _stream_,
and _kedge anchors_. Ships of the first class have seven anchors, and
smaller vessels, such as brigs and schooners, three.
[Illustration: 7]
The manufacture of anchors requires great knowledge of the structure of
iron, and skill in the art of working it. I shall give, here, a brief
notice of the improved system introduced by Mr. Perring, clerk of the
cheque at Plymouth, in which the proportions of the parts are admirably
adapted to the strains they are likely to suffer. In _fig._ 7. A is the
_shank_; B, the _arm_ or _fluke_; C, the _palm_; D, the _blade_; E, the
_square_; F, the _nut_; G, the _ring_; H, the _crown_.
Formerly the shank was made of a number of square iron rods, laid
parallel together in a cylindrical form, and bound by iron hoops. When
they were welded into one bar, the exterior rods could not fail to be
partially burned and wasted by the strong heat. Mr. Perring abated this
evil by using bars of the whole breadth of the shank, and placing them
right over each other, hooping them and welding them together at two
heats into one solid mass. To any one who has seen the working of
puddled iron, with a heavy mill hammer, this operation will not appear
difficult.
He formed the crown with bars similarly distributed with those of the
shank. His mode of uniting the flukes to the crown is probably the most
valuable part of his invention. The bars and half the breadth of the
anchor are first welded separately, and then placed side by side, where
the upper half is worked into one mass, while the lower part is left
disunited, but has carrier iron bars, or _porters_, as these
prolongation rods are commonly called, welded to the extremity of each
portion. The lower part is now heated and placed in the clamping
machine, which is merely an iron plate firmly bolted to a mass of
timber, and bearing upon its surface four iron pins. One end of the
crown is placed between the first of these pins, and passed under an
iron strap; the other end is brought between the other pins, and is bent
by the leverage power of the elongated rods or porters.
Thus a part of the arm being formed out of the crown gives much greater
security that a true union of fibres is effected, than when the junction
was made merely by a short scarf.
The angular opening upon the side opposite B H, _fig._ 7., is filled
with the _chock_, formed of short iron bars placed upright. When this
has been firmly welded, the truss-piece is brought over it. This piece
is made of plates similar to the above, except that their edges are here
horizontal. The truss-piece is half the breadth of the arm; so that when
united to the crown, it constitutes, with the other parts, the total
breadth of the arms at those places.
The shank is now shut upon the crown; the square is formed, and the nuts
welded to it; the hole is punched out for the ring, and the shank is
then fashioned.
The blade is made much in the way above described. In making the palm,
an iron rod is first bent into the approximate form, notching it so that
it may more readily take the desired shape. To one end a _porter_ rod is
fastened, by which the palm is carried and turned round in the fire
during the progress of the fabrication. Iron plates are next laid side
by side upon the rod, and the joint at the middle is broken by another
plate laid over it. When the mass is worked, its under side is filled up
by similar plates, and the whole is completely welded; pieces being
added to the sides, if necessary, to form the angles of the palm. The
blade is then shut on to the palm, after which the part of the arm
attached to the blade is united to that which constitutes the crown. The
smith-work of the anchor is now finished.
The junction, or shutting on, as the workmen call it, of the several
members of an anchor, is effected by an instrument called a _monkey_,
which is merely a mass of iron raised to a certain height, between
parallel uprights, as in the pile engine or vertical ram, and let fall
upon the metal previously brought to a welding heat.
The _monkey_ and the _hercules_, both silly, trivial names, are similar
instruments, and are usually worked, like a portable pile engine, by the
hands of several labourers, pulling separate ropes. Many other modes of
manufacturing anchors have been devised, in which mechanical power is
more extensively resorted to.
The upper end of the shank F (_fig._ 7.) is squared to receive and hold
the stock steadily, and keep it from turning. To prevent it shifting
along, there are two knobs or tenon-like projections. The point of the
angle H, between the arms and the shank, is sometimes called the throat.
The arm B C generally makes an angle of 56° with the shank A; it is
either round or polygonal, and about half the length of the shank.
The _stock_ of the anchor (_fig._ 6.) is made of oak. It consists of two
beams which embrace the _square_, and are firmly united by iron bolts
and hoops, as shown in the figure. The stock is usually somewhat longer
than the shank, has in the middle a thickness about one-twelfth of its
length, but tapers at its under side to nearly one half this thickness
at the extremities. In small anchors the stock is frequently made of
iron; but in this case it does not embrace the anchor, but goes through
a hole made in the square, which is swelled out on purpose.
The weight of anchors for different vessels is proportioned to the
tonnage; a good rule being to make the anchor in hundredweights
one-twentieth of the number of tons of the burden. Thus a ship of 1000
tons would require a sheet anchor of 50 cwts. Ships of war are provided
with somewhat heavier anchors.
Several new forms and constructions of anchors were proposed under Mr.
Piper’s patent of November, 1822, by the adoption of which great
advantages as to strength were anticipated over every other form or
construction previously made.
The particular object was to preserve such a disposition of the fibres
of the metal as should afford the greatest possible strength; in doing
which the crossing or bending of the fibres at the junctions of the
shank, flukes, and crown, where great strength is required, has been
avoided as much as possible, so that the fibres are not disturbed or
injured.
In this respect most anchors are defective; for in connecting the shanks
to the crown-pieces, the grain of the metal is either crossed, or so
much curved, as to strain the fibre, and consequently induce a weakness
where the greatest strength is required. And, further, the very
considerable thicknesses of metal which are to be brought into immediate
contact by means of the hammer in forging anchors upon the old
construction, render it highly probable that faulty places may be left
within the mass, though they be externally imperceptible. Mr. Piper’s
leading principle was, that the fibre of the metal should run nearly
straight in all the parts where strength is particularly required.
[Illustration: 8]
_Fig._ 8. shows an anchor with one tumbling fluke, which passes through
the forked or branched part of the shank. The lower part of this anchor,
answering to the crown, has a spindle through it, upon which the fluke
turns, and a pin is there introduced for the purpose of confining the
fluke when in a holding position. This shank is formed of a solid piece
of wrought iron, the fibres of which run straight, and at the crown
holes are pierced, which merely bulge the metal without bending the
fibres round so as to strain them. The arm and fluke, also, are formed
of one piece punched through without curling or crossing the fibre, and
the spindle which holds the arm to the crown is likewise straight. This
spindle extends some distance on each side of the anchor, and is
intended to answer the purpose of a stock; for when either of the ends
of the spindle comes in contact with the ground, the anchor will be
thrown over into a holding position; or an iron stock may be introduced
near the shackle, instead of these projecting ends. In the descent of
the anchor, the fluke will fall over towards that side which is nearest
the ground, and will there be ready to take hold when the anchor is
drawn forward.
[Illustration: 9]
_Fig._ 9. is another anchor upon the same principle, but slightly varied
in form from the last. In this the forked part of the shank is closer
than in the former, and there are two arms or flukes connected to the
crown-pieces, one of which falls into its holding position as the anchor
comes to the ground, and is held at its proper angle by the other fluke
stopping against the shank.
[Illustration: 10]
_Fig._ 10. represents another variation in the form of these improved
anchors, having two tumbling flukes, which are both intended to take
hold of the ground at the same time. The shank is here, as before, made
without crossing the grain of the iron, and the eyes for admitting the
bolt at the crown and at the shackle are punched out of the solid, not
formed by welding or turning the iron round. In this form a guard is
introduced at the crown, to answer the purpose of a stock, by turning
the flukes over into a holding position. The arms and flukes are made,
as before described, of the straight fibre of the iron punched through,
and the flukes are fixed to the spindle, which passes through the
crown-piece.
[Illustration: 11]
_Fig._ 11. has a shank without any fork, but formed straight throughout;
the guard here is an elongated frame of iron, for the same purpose as a
stock, and is, with the tumbling flukes, fastened to the spindle, which
passes through the crown of the anchor, and causes the flukes to fall
into their holding position.
The principles of these new anchors are considered to consist in shanks
which are made of straight lengths of metal, and finished so that the
fibres of the iron shall not be injured by cross-shuts or uncertain
welding; also each arm and palm is made in one solid piece, and finished
in straight lines, so that the fibres will not be altered, and the
shaft-pin or spindle will also be in one straight line; and this is the
improvement claimed. These anchors being made in separate pieces, give a
great advantage to the workman to execute each part perfectly; for he
will not have such heavy weights to lift when hot, which will render
these anchors much stronger, with less weight; and if any accident
should happen to them, any part may be taken separate from the others to
be repaired, and several of those parts of the anchor which may be
likely to break may be carried on board, in case of accident. This
anchor is so contrived that one of thirty hundred weight may be taken to
pieces and put together again, by one man, in twenty minutes; it may
also be dismounted, and stowed in any part of the ship, in as little
room as straight bars of iron, and speedily put together again.
[Illustration: 12]
The anchor (_fig._ 12.) patented by Mr. Brunton, in February, 1822, has
its stock introduced at the crown part, for the purpose of turning it
over into a holding position. The shank is perforated through the solid,
in two places, with elliptical apertures, for the purpose of giving it a
greater stability, and more effectually resisting the strain to which
the anchor may be subjected. The stock is a cylindrical iron rod, held
at its extremities by lateral braces, which are bolted to the shank.
_Fig._ 12. shows the form of the anchor. The shank is seen upright, with
one of the flukes projecting in its front; the horizontal iron stock is
at bottom; and the oblique braces are bolted to both shank and stock.
The ends of the stock, from the shoulder, are formed dove-tailed, and
oval in the vertical direction, and are protruded through apertures in
the braces, also oval, but in the horizontal direction, and counter
sunk. When the ends of the stock have been thus introduced through the
holes, the braces are securely bolted to the shank; the ends of the
stock are then spread, by hammering into the counter-sunk holes of the
braces, and by that means they are made firm.
An anchor of this description is considered by the patentee to possess
considerable advantage, particularly in point of stability, over the
ordinary construction of anchors, and is economical, inasmuch as a less
weight of metal will give, upon this plan, an equal degree of strength.
An ingenious form of anchor was made the subject of a patent, by
Lieutenant Rodgers, of the Royal Navy, in 1828, and was afterwards
modified by him in a second patent, obtained in August, 1829. The whole
of the parts of the anchor are to be bound together by means of iron
bands or hoops, in place of bolts or pins.
[Illustration: 13 14 15 16]
_Fig._ 13. is a side view of a complete anchor, formed upon his last
improved construction, and _fig._ 14., a plan of the same; _fig._ 15.,
an end view of the crown and flukes, or arms; _fig._ 16. represents the
two principal iron plates, _a_, _a_, of which the shank is constructed,
but so as to form parts of the stump arms to which the flukes are to be
connected.
The crown piece is to be welded to the stump piece, _c c_, _fig._ 16.,
as well as to the end _l_ of the centre piece _h h_, and the scarfs _m
m_ are to be cut to receive the arms or flukes. Previously, however, to
uniting the arms or flukes with the stump arms, the crown and throat of
the anchor are to be strengthened, by the application of the crown slabs
_n n_, _fig._ 16., which are to be welded upon each side of the crown,
overlapping the end of the pillar _h_, and the throat or knees of the
stump arms and the crown piece. The stump arms are then to be
strengthened in a similar manner, by the thin flat pieces _p p_, which
are to be welded upon each side. The palms are united to the flukes in
the usual way, and the flukes are also united to the stump arms by means
of the long scarfs _m m_. When the shank of the anchor has been thus
formed, and united with the flukes, the anchor smith’s work may be said
to be complete.
[Illustration: 17]
Another of the improvements in the construction of anchors, claimed
under this patent, consists in a new method of affixing the stock upon
the shank of the anchor, which is effected in the following manner: in
_fig._ 14. the stock is shown affixed to the anchor; in _fig._ 17. it is
shown detached. It may be made either of one or two pieces of timber, as
may be found most convenient. It is, however, to be observed that the
stock is to be completed before fitting on to the shank. After the stock
is shaped, a hole is to be made through the middle of it, to fit that
part of the shank to which it is to be affixed. Two stock plates are
then to be let in, one on each side of the stock, and made fast by
counter sunk nails and straps, or hoops; other straps or hoops of iron
are also to be placed round the stock, as usual.
In place of nuts, formed upon the shank of the anchor, it is proposed to
secure the stock by means of a hoop and a key, shown above and below J,
in _fig._ 14. By this contrivance, the stock is prevented from going
nearer to the crown of the anchor than it ought to do, and the key
prevents it from sliding towards the shackle.
Since fitting the stock to the shank of an anchor, by this method,
prevents the use of a ring, as in the ordinary manner, the patentee says
that he in all cases substitutes a shackle for the ring, and which is
all that is required for a chain cable; but, when a hempen cable is to
be used, he connects a ring to the usual shackle, by means of a joining
shackle, as in _figs._ 13. and 14.
Mr. Rodgers proposes, under another patent, dated July, 1833, to alter
the size and form of the palms; having found from experience that
anchors with small palms will not only hold better than with large ones,
but that the arms of the anchor, even without any palms, have been found
to take more secure hold of the ground than anchors of the old
construction, of similar weight and length. He has, accordingly, fixed
upon one-fifth of the length of the arm, as a suitable proportion for
the length or depth of the palm. He makes the palms, also, broader than
they are long or deep.
ANIMÉ. A resin of a pale brown yellow colour, transparent and brittle.
It exudes from the courbaril of Cayenne, a tree which grows also in
various parts of South America. It occurs in pieces of various sizes,
and it often contains so many insects belonging to living species, as to
have merited its name, as being animated. It contains about a fifth of
one per cent. of a volatile oil, which gives it an agreeable odour.
Alcohol does not dissolve the genuine animé, as I have ascertained by
careful experiments; nor does caoutchoucine; but a mixture of the two,
in equal parts, softens it into a tremulous jelly, though it will not
produce a liquid solution. When reduced to this state, the insects can
be easily picked out, without injury to their most delicate parts.
The specific gravity of the different specimens of animé which I tried,
varied from 1·054 to 1·057. When exposed to heat, in a glass retort over
a spirit flame, it softens, and, by careful management, it may be
brought into liquid fusion, without discolouration. It then exhales a
few white vapours, of an ambrosiacal odour, which being condensed in
water, and the liquid being tested, is found to be succinic acid.
_Author._
It is extensively used by the varnish makers, who fuse it at a pretty
high heat, and in this state combine it with their oils, or other
varnishes.
ANKER. A liquid measure of Amsterdam, which contains 32 gallons English.
ANNEALING or NEALING. (_Le recuit_, Fr.; _das anlassen_, Germ.) A
process by which glass is rendered less frangible; and metals, which
have become brittle, either in consequence of fusion, or long-continued
hammering, are again rendered malleable. When a glass vessel is allowed
to cool immediately after being made, it will often sustain the shock of
a pistol-bullet, or any other blunt body falling into it from a
considerable height; while a small splinter of flint, or an angular
fragment of quartz, dropped gently into it, makes it sometimes
immediately, sometimes after a few minutes, fly to pieces with great
violence. This extreme fragility is prevented by annealing, or placing
the vessels in an oven, where they take several hours or even some days
to cool. Similar phenomena are exhibited in a higher degree by
glass-tears, or Prince Rupert’s drops. They are procured by letting
drops of melted glass fall into cold water. Their form resembles that of
a pear, rounded at one extremity, and tapering to a very slender tail at
the other. If a part of the tail be broken off, the whole drop flies to
pieces with a loud explosion; and yet the tail of a drop may be cut away
by a glass-cutter’s wheel, or the thick end may be struck smartly with
a hammer, without the fear of sustaining any injury. When heated to
redness, and permitted to cool gradually in the open air, they lose
these peculiarities, and do not differ sensibly from common glass.
The properties of unannealed glass depend on a peculiar structure,
extending uniformly through its whole substance; and the bursting of a
glass drop by breaking off the tail, or of an unannealed glass vessel,
by dropping a piece of flint into it, arises from a crack being thus
begun, which afterwards extends its ramifications in different
directions throughout the glass.
When metals have been extended to a certain degree under the hammer,
they become brittle, and incapable of being further extended without
cracking. In this case the workman restores their malleability by
annealing, or heating them red-hot. The rationale of this process seems
to be, that the hammering and extension of the metal destroy the kind of
arrangement which the particles of the metal had previous to the
hammering; and that the annealing, by softening the metal, enables it to
recover its original structure.
Of late years a mode has been discovered of rendering cast iron
malleable, without subjecting it to the action of puddling. The process
is somewhat similar to that employed in annealing glass. The metal is
kept for several hours at a temperature a little below its fusing point,
and then allowed to cool slowly. In this manner vessels are made of cast
iron which can sustain considerable violence, without being broken. See
STEEL, softening of.
ANNOTTO. (_Rocou_, or _roucou_, Fr.; _orleans_, Germ.) A somewhat dry
and hard paste, brown without, and red within. It is usually imported in
cakes of two or three pounds weight, wrapped up in leaves of large
reeds, packed in casks, from America, where it is prepared from the
seeds of a certain tree, the _bixa orellana_, of Linnæus.
The pods of the tree being gathered, their seeds are taken out and
bruised; they are then transferred to a vat, which is called the
steeper, where they are mixed with as much water as covers them. Here
the substance is left for several weeks, or even months; it is now
squeezed through sieves placed above the steeper, that the water
containing the colouring matter in suspension may return, into the vat.
The residuum is preserved under the leaves of the anana (pine-apple)
tree, till it becomes hot by fermentation. It is again subjected to the
same operation, and this treatment is continued till no more colour
remains.
The substance thus extracted is passed through sieves, in order to
separate the remainder of the seeds, and the colour is allowed to
subside. The precipitate is boiled in coppers till it be reduced to a
consistent paste; it is then suffered to cool, and dried in the shade.
Instead of this long and painful labour, which occasions diseases by the
putrefaction induced, and which affords a spoiled product, Leblond
proposes simply to wash the seeds of annotto till they be entirely
deprived of their colour, which lies wholly on their surface; to
precipitate the colour by means of vinegar or lemon juice, and to boil
it up in the ordinary manner, or to drain it in bags, as is practised
with indigo.
The experiments which Vauquelin made on the seeds of annotto imported by
Leblond, confirmed the efficacy of the process which he proposed; and
the dyers ascertained that the annotto obtained in this manner was worth
at least four times more than that of commerce; that, moreover, it was
more easily employed; that it required less solvent; that it gave less
trouble in the copper, and furnished a purer colour.
Annotto dissolves better and more readily in alcohol than in water, when
it is introduced into the yellow varnishes for communicating an orange
tint.
The decoction of annotto in water has a strong peculiar odour, and a
disagreeable taste. Its colour is yellowish-red, and it remains a little
turbid. An alkaline solution renders its orange-yellow clearer and more
agreeable, while a small quantity of a whitish substance is separated
from it, which remains suspended in the liquid. If annotto be boiled in
water along with an alkali, it dissolves much better than when alone,
and the liquid has an orange hue.
The acids form with this liquor an orange-coloured precipitate, soluble
in alkalies, which communicate to it a deep orange colour. The
supernatant liquor retains only a pale yellow hue.
When annotto is used as a dye, it is always mixed with alkali, which
facilitates its solution, and gives it a colour inclining less to red.
The annotto is cut in pieces, and boiled for some instants in a copper
with its own weight of crude pearl ashes, provided the shade wanted do
not require less alkali. The cloths may be thereafter dyed in this bath,
either by these ingredients alone, or by adding others to modify the
colour; but annotto is seldom used for woollen, because the colours
which it gives are too fugitive, and may be obtained by more permanent
dyes. Hellot employed it to dye a stuff, prepared with alum and tartar;
but the colour acquired had little permanence. It is almost solely used
for silks.
For silks intended to become aurora and orange, it is sufficient to
scour them at the rate of 20 per cent. of soap. When they have been well
cleansed, they are immersed in a bath prepared with water, to which is
added a quantity of alkaline solution of annotto, more or less
considerable according to the shade that may be wanted. This bath should
have a mean temperature, between that of tepid and boiling water.
When the silk has become uniform, one of the hanks is taken out, washed,
and wrung, to see if the colour be sufficiently full; if it be not so,
more solution of annotto is added, and the silk is turned again round
the sticks: the solution keeps without alteration.
When the desired shade is obtained, nothing remains but to wash the
silk, and give it two beetlings at the river, in order to free it from
the redundant annotto, which would injure the lustre of the colour.
When raw silks are to be dyed, those naturally white are chosen, and
dyed in the annotto bath, which should not be more than tepid, or even
cold, in order that the alkali may not attack the gum of the silk, and
deprive it of the elasticity which it is desirable for it to preserve.
What has been now said regards the silks to which the aurora shades are
to be given; but to make an orange hue, which contains more red than the
aurora, it is requisite, after dyeing with annotto, to redden the silks
with vinegar, alum, or lemon juice. The acid, by saturating the alkali
employed for dissolving the annotto, destroys the shade of yellow that
the alkali had given, and restores it to its natural colour, which
inclines a good deal to red.
For the deep shades, the practice at Paris, as Macquer informs us, is to
pass the silks through alum; and if the colour be not red enough, they
are passed through a faint bath of brazil wood. At Lyons, the dyers who
use carthamus, sometimes employ old baths of this ingredient for dipping
the deep oranges.
When the orange hues have been reddened by alum, they must be washed at
the river; but it is not necessary to beetle them, unless the colour
turns out too red.
Shades may be obtained also by a single operation, which retain a
reddish tint, employing for the annotto bath a less proportion of alkali
than has been pointed out.
Guhliche recommends to avoid heat in the preparation of annotto. He
directs it to be placed in a glass vessel, or in a glazed earthen one;
to cover it with a solution of pure alkali; to leave the mixture at rest
for 24 hours; to decant the liquor, filter it, and add water repeatedly
to the residuum, leaving the mixture each time at rest for two or three
days, till the water is no longer coloured; to mix all these liquors,
and preserve the whole for use in a well-stopped vessel.
He macerates the silk for 12 hours in a solution of alum, at the rate of
an eighth of this salt for one part of silk, or in a water rendered
acidulous by the aceto-citric acid above described; and he wrings it
well on its coming out of this bath.
Silk thus prepared is put into the annotto bath quite cold. It is kept
in agitation there till it has taken the shade sought for; or the liquor
may be maintained at a heat far below ebullition. On being taken out of
the bath, the silk is to be washed and dried in the shade.
For lighter hues, a liquor less charged with colour is taken; and a
little of the acid liquid which has served for the mordant may be added,
or the dyed silk may be passed through the acidulous water.
We have seen the following preparation employed for cotton velvet:--one
part of quicklime, one of potash, two of soda.
Of these a ley is formed, in which one part of annotto is dissolved; and
the mixture is boiled for an hour and a half. This bath affords the
liveliest and most brilliant auroras. The buff (chamois) fugitive dye is
also obtained with this solution. For this purpose only a little is
wanted; but we must never forget, that the colours arising from annotto
are all fugitive.
Dr. John found in the pulp surrounding the unfermented fresh seeds,
which are about the size of little peas, 28 parts of colouring resinous
matter, 26·5 of vegetable gluten, 20 of ligneous fibre, 20 of colouring
extractive matter, 4 formed of matters analogous to vegetable gluten and
extractive, and a trace of spicy and acid matters.
The Gloucestershire cheese is coloured with annotto, in the proportion
of one cwt. to an ounce of the dye.
When used in calico-printing, it is usually mixed with potash or ammonia
and starch.
It is an appropriate substance for tingeing varnishes, oils, spirits,
&c.
The import duty upon annotto is 1_s._ per cwt. for flag, and 4_s._ for
other sorts. In 1834, 252,981 lbs. were imported; and in 1835, 163,421
lbs. The revenue from this drug in these two years, was 180_l._ and
98_l._ respectively.
ANTHRACITE, from ανθραξ, coal, is a species of coal found in the
transition rock formation, and is often called stone coal. It has a
grayish black, or iron black colour, an imperfectly metallic lustre,
conchoidal fracture, and a specific gravity of from 1·4 to 1·6, being,
therefore, much denser than the coal of the proper coal measures. It
consists wholly of carbon, with a small and variable proportion of
iron, silica, and alumina. It is difficult to kindle in separate masses,
and burns when in heaps or grates without smell or smoke, leaving
sometimes an earthy residuum. It has been little explored or worked in
the old world; but is extensively used in the United States of America,
and has become of late years a most valuable mineral to that country,
where it is burned in peculiar grates, adapted to its difficult
combustion. In Pennsylvania the anthracite coal formation has been
traced through a tract many miles in width, and extending across the two
entire counties of Luzerne and Schuylkill. At Maunch Chunk, upon the
Lehigh, 800 men were employed so far back as 1825, in digging this coal.
In that year 750,000 bushels were dispatched for Philadelphia. It is
worked there with little cost or labour, being situated on hills from
300 to 600 feet above the level of the neighbouring rivers and canals,
and existing in nearly horizontal beds, of from 15 to 40 feet in
thickness, covered by only a few feet of gravelly loam. At Portsmouth,
in Rhode Island, an extensive stratum of this coal has been worked, with
some interruptions, for 20 years; and more recently a mine of anthracite
has been opened at Worcester, in Massachusetts, at the head of the
Blackstone canal. It has been of late employed in South Wales, for
smelting iron, and in a cupola blast furnace, by Mr. Crane.
ANTIGUGGLER. A small syphon of metal, which is inserted into the mouths
of casks, or large bottles, called carboys, to admit air over the liquor
contained in them, and thus to facilitate their being emptied without
agitation or a guggling noise.
ANTIMONY. (_Antimoine_, Fr.; _Spiessglanz_, or _Spiessglass_, Ger.) The
only ore of this metal found in sufficient abundance to be smelted, is
the sulphuret, formerly called crude antimony. It occurs generally in
masses, consisting of needles closely aggregated, of a metallic lustre,
a lead-gray colour, inclining to steel-gray, which is unchanged in the
streak. The needles are extremely brittle, and melt even in the flame of
a candle, with the exhalation of a sulphureous smell. The powder of this
sulphuret is very black, and was employed by women in ancient times to
stain their eyebrows and eyelids. This ore consists in 100 parts of
72·86 metal, and 27·14 sulphur. Specific gravity from 4·13 to 4·6.
The veins of sulphuret of antimony occur associated with gangues of
quartz, sulphate of barytes, and carbonate of lime; those of Allémont
occur in the numerous fissures of a mica schist, evidently primitive.
In treating the ore to obtain the metal, the first object is to separate
the gangue, which was formerly done by filling crucibles with the mixed
materials, placing them on the hearth of an oven, and exposing them to a
moderate heat. As the sulphuret easily melts, it ran out through a hole
in the bottom of the crucible into a pot placed beneath, and out of the
reach of the fire. But the great loss from breakage of the crucibles,
has caused another method to be adopted. In this the broken ore, being
sorted, is laid on the bottom of a concave reverberatory hearth, where
it is reduced.
[Illustration: 18 19]
_Figs._ 18. 19. represent a wind or flame furnace, for the reduction of
antimony. The hearth is formed of sand and clay solidly beat together,
and slopes from all sides towards the middle, where it is connected with
the orifice _a_, which is closed with dense coal-ashes; _b_ is the air
channel up through the bridge; _c_, the door for introducing the
prepared ore, and running off the slags; _d_, the bridge; _e_, the
grate; _f_, the fire or fuel-door; _g_, the chimney. With 2 or 3 cwt. of
ore, the smelting process is completed in from 8 to 10 hours. The metal
thus obtained is not pure enough, but must be fused under coal dust, in
portions of 20 or 30 pounds, in crucibles, placed upon a reverberatory
hearth.
To obtain antimony free from iron, it should be fused with some
antimonic oxide in a crucible, whereby the iron is oxidized and
separated. The presence of arsenic in antimony is detected by the garlic
smell, emitted by such an alloy when heated at the blow-pipe; or,
better, by igniting it with nitre in a crucible; in which case,
insoluble antimonite and antimoniate of potash will be formed along with
soluble arseniate. Water digested upon the mixture, filtered, and then
tested with nitrate of silver, will afford the brown-red precipitate
characteristic of arsenic acid.
According to Berthier, the following materials afford, in smelting, an
excellent product of antimony: 100 parts of sulphuret; 60 of
hammerschlag (protoxide of iron from the shingling or rolling mills); 45
to 50 of carbonate of soda; and 10 of charcoal powder. From 65 to 70
parts of metallic antimony or regulus should be obtained. Glauber salts
may be used instead of soda. For another mode of smelting antimony, at
Malbosc, in the department of Ardèche, in France, see LIQUATION.
In the works where antimonial ores are smelted, by means of tartar
(argol), the alkaline scoriæ, which cover the metallic ingots, are not
rejected as useless, for they hold a certain quantity of antimonial
oxide in combination; a property of the potash flux, which is propitious
to the purity of the metal. These scoriæ, consisting of sulphuret of
potassium and antimonite of potash, being treated with water, undergo a
reciprocal decomposition; the elements of the water act on those of the
sulphuret, and the resulting alkaline hydro-sulphuret re-acts on the
antimonial solution, so as to form a species of _kermes mineral_, which
precipitates. This is dried, and sold at a low price as a veterinary
medicine, under the name of _kermes_, by the dry way.
Metallic antimony, as obtained by the preceding process, is the antimony
of commerce, but is not absolutely pure; containing frequently minute
portions of iron, lead, and even arsenic; the detection and separation
of which belong to the sciences of chemistry and pharmacy. Antimony is a
brittle metal, of a silvery white colour, with a tinge of blue, a
lamellar texture, and crystalline fracture. When heated at the blowpipe,
it melts with great readiness, and diffuses white vapours, possessing
somewhat of a garlic smell. If thrown in this melted state on a sheet of
flat paper, the globule sparkles, and bursts into a multitude of small
spheroids, which retain their incandescence for a long time, and run
about on the paper, leaving traces of the white oxide produced during
the combustion. When this oxide is fused with borax, or other vitrifying
matter, it imparts a yellow colour to it. Metallic antimony, treated
with hot nitric acid and in a concentrated state, is converted into a
powder, called antimonious acid, which is altogether insoluble in the
ordinary acid menstrua; a property by which the chemist can separate
that metal from lead, iron, copper, bismuth, and silver. According to
Bergman, the specific gravity of antimony is 6·86; but Haidinger makes
the Swedish native metal only 6·646. The alchemists had conceived the
most brilliant hopes of this metal; the facility with which it is
alloyed with gold, since its fumes alone render this most ductile metal
immediately brittle, led them to assign to it a royal lineage, and to
distinguish it by the title of _regulus_, or the little king.
Its chief employment now is in medicine, and in making the alloys called
type metal, stereotype metal, music plates, and Britannia-metal; the
first consisting of 6 of lead and 2 of antimony; the second of 6 of lead
and 1 of antimony; the third of lead, tin, and antimony; and the fourth
also of lead, tin, and antimony, with occasionally a little copper and
bismuth.--For Glass of antimony, see PASTES.
ANTISEPTICS. Substances which counteract the spontaneous decomposition
of animal and vegetable substances. These are chiefly culinary salt,
nitre, spices, and sugar, which operate partly by inducing a change in
the animal or vegetable fibres, and partly by rendering the aqueous
constituent unsusceptible of decomposition. See PROVISIONS, CURING OF.
ANVIL. A mass of iron, having a smooth and nearly flat top surface of
steel; upon which blacksmiths, and various other artificers, forge
metals with the hammer. The common anvil is usually made of seven
pieces: 1, the core, or body; 2, 3, 4, 5, the four corner pieces which
serve to enlarge its base; 6, the projecting end, which has a square
hole for the reception of the tail or shank of a chisel on which iron
bars may be cut through; and 7, the beak, or horizontal cone round which
rods or slips of metal may be turned into a circular form, as in making
rings. These 6 pieces are welded separately to the first, or core, and
then hammered into an uniform body. In manufacturing large anvils two
hearths are needed, in order to bring each of the two pieces to be
welded, to a proper heat by itself; and several men are employed in
working them together briskly in the welding state, by heavy swing
hammers. The steel facing is applied by welding in the same manner. The
anvil is then hardened by heating it to a cherry red, and plunging it
into cold water; a running stream being preferable to a pool or cistern.
The facing should not be too thick a plate, for, when such, it is apt to
crack in the hardening. The face of the anvil is now smoothed upon a
grindstone, and finally polished with emery and crocus, for all delicate
purposes of art.
The blacksmith, in general, sets his anvil loosely upon a wooden block,
and in preference on the root of an oak. But the cutlers and file-makers
fasten their anvils to a large block of stone; which is an advantage,
for the more firmly and solidly this tool is connected to the earth, the
more efficacious will be the blows of the hammer on any object placed
upon it.
AQUAFORTIS. Nitric acid, somewhat dilute, was so named by the alchemists
on account of its strong solvent and corrosive operation upon many
mineral, vegetable, and animal substances. See NITRIC ACID.
AQUA REGIA. The name given by the alchemists to that mixture of nitric
and muriatic acids which was best fitted to dissolve gold, styled by
them the king of the metals. It is now called _nitro-muriatic acid_.
AQUA VITÆ. The name very absurdly given to alcohol, when used as an
intoxicating beverage. It has been the _aqua mortis_ to myriads of the
human race; and will, probably, ere long destroy all the native tribes
of North America and Australia.
ARCHIL. A violet red paste used in dyeing, of which the substance called
_cudbear_ in Scotland (from _Cuthbert_, its first preparer in that
form), is a modification. Two kinds of archil are distinguished in
commerce, the _archil_ plant of the Canaries, and that of Auvergne. The
first is most esteemed: it is prepared from the _lichen rocellus_, which
grows on rocks adjoining the sea in the Canary and Cape de Verde
Islands, in Sardinia, Minorca, &c., as well as on the rocks of Sweden.
The second species is prepared from the _lichen parellus_, which grows
on the basaltic rocks of Auvergne.
There are several other species of lichen which might be employed in
producing an analogous dye, were they prepared, like the preceding, into
the substance called _archil_. Hellot gives the following method for
discovering if they possess this property. A little of the plant is to
be put into a glass vessel; it is to be moistened with ammonia and
lime-water in equal parts; a little muriate of ammonia (sal ammoniac) is
added; and the small vessel is corked. If the plant be of a nature to
afford a red dye, after three or four days, the small portion of liquid,
which will run off on inclining the vessel, now opened, will be tinged
of a crimson red, and the plant itself will have assumed this colour. If
the liquor or the plant does not take this colour, nothing need be hoped
for; and it is useless to attempt its preparation on the great scale.
Lewis says, however, that he has tested in this way a great many mosses,
and that most of them afforded him a yellow or reddish brown colour; but
that he obtained from only a small number a liquor of a deep red, which
communicated to cloth merely a yellowish-red colour.
Prepared archil gives out its colour very readily to water, ammonia, and
alcohol. Its solution in alcohol is used for filling spirit-of-wine
thermometers; and when these thermometers are well freed from air, the
liquor loses its colour in some years, as Abbé Nollet observed. The
contact of air restores the colour, which is destroyed anew, in vacuo,
in process of time. The watery infusion loses its colour, by the
privation of air, in a few days; a singular phenomenon, which merits new
researches.
The infusion of archil is of a crimson bordering on violet. As it
contains ammonia, which has already modified its natural colour, the
fixed alkalies can produce little change on it, only deepening the
colour a little, and making it more violet. Alum forms in it a
precipitate of a brown red; and the supernatant liquid retains a
yellowish-red colour. The solution of tin affords a reddish precipitate,
which falls down slowly; the supernatant liquid retains a feeble red
colour. The other metallic salts produce precipitates which offer
nothing remarkable.
The watery solution of archil applied to cold marble, penetrates it,
communicating a beautiful violet colour, or a blue bordering on purple,
which resists the air much longer than the archil colours applied to
other substances. Dufay says, that he has seen marble tinged with this
colour preserve it without alteration at the end of two years.
To dye with archil, the quantity of this substance deemed necessary,
according to the quantity of wool or stuff to be dyed, and according to
the shade to which they are to be brought, is to be diffused in a bath
of water as soon as it begins to grow warm. The bath is then heated till
it be ready to boil, and the wool or stuff is passed through it without
any other preparation, except keeping that longest in, which is to have
the deepest shade. A fine gridelin, bordering upon violet, is thereby
obtained; but this colour has no permanence. Hence archil is rarely
employed with any other view than to modify, heighten, and give lustre
to the other colours. Hellot says, that having employed archil on wool
boiled with tartar and alum, the colour resisted the air no more than
what had received no preparation. But he obtained from herb archil
(_l’orseille d’herbe_) a much more durable colour, by putting in the
bath some solution of tin. The archil thereby loses its natural colour,
and assumes one approaching more or less to scarlet, according to the
quantity of solution of tin employed. This process must be executed in
nearly the same manner as that of scarlet, except that the dyeing may be
performed in a single bath.
Archil is frequently had recourse to for varying the different shades
and giving them lustre; hence it is used for violets, lilacs, mallows,
and rosemary flowers. To obtain a deeper tone, as for the deep _soupes
au vin_, sometimes a little alkali or milk of lime is mixed with it. The
suites of this browning may also afford agates, rosemary flowers, and
other delicate colours, which cannot be obtained so beautiful by other
processes. Alum cannot be substituted for this purpose; it not only does
not give this lustre, but it degrades the deep colours.
The herb-archil is preferable to the archil of Auvergne, from the
greater bloom which it communicates to the colours, and from the larger
quantity of colouring matter. It has, besides, the advantage of bearing
ebullition. The latter, moreover, does not answer with alum, which
destroys the colour; but the herb archil has the inconvenience of dyeing
in an irregular manner, unless attention be given to pass the cloth
through hot water as soon as it comes out of the dye.
Archil alone is not used for dyeing silk, unless for lilacs; but silk is
frequently passed through a bath of archil, either before dyeing it in
other baths or after it has been dyed, in order to modify different
colours, or to give them lustre. Examples of this will be given in
treating of the compound colours. It is sufficient here to point out how
white silks are passed through the archil bath. The same process is
performed with a bath more or less charged with this colour, for silks
already dyed.
Archil, in a quantity proportioned to the colour desired, is to be
boiled in a copper. The clear liquid is to be run off quite hot from the
archil bath, leaving the sediment at the bottom, into a tub of proper
size, in which the silks, newly scoured with soap, are to be turned
round on the skein-sticks with much exactness, till they have attained
the wished-for shade. After this they must receive one beetling at the
river.
Archil is in general a very useful ingredient in dyeing; but as it is
rich in colour, and communicates an alluring bloom, dyers are often
tempted to abuse it, and to exceed the proportions that can add to the
beauty without at the same time injuring in a dangerous manner the
permanence of the colours. Nevertheless, the colour obtained when
solution of tin is employed, is less fugitive than without this
addition: it is red, approaching to scarlet. Tin appears to be the only
ingredient which can increase its durability. The solution of tin may be
employed, not only in the dyeing bath, but for the preparation of the
silk. In this case, by mixing the archil with other colouring
substances, dyes may be obtained which have lustre with sufficient
durability.
We have spoken of the colour of the archil as if it were natural to it;
but it is, really, due to an alkaline combination. The acids make it
pass to red, either by saturating the alkali, or by substituting
themselves for the alkali.
The lichen which produces archil is subjected to another preparation, to
make turnsole (litmus). This article is made in Holland. The lichen
comes from the Canary Islands, and also from Sweden. It is reduced to a
fine powder by means of a mill, and a certain proportion of potash is
mixed with it. The mixture is watered with urine, and allowed to suffer
a species of fermentation. When this has arrived at a certain degree,
carbonate of lime in powder is added, to give consistence and weight to
the paste, which is afterwards reduced into small parallelopipeds that
are carefully dried.
The latest researches on the lichens, as objects of manufacture, are
those of Westring of Stockholm. He examined 150 species, among which he
found several which might be rendered useful. He recommends that the
colouring matter should be extracted in the places where they grow,
which would save a vast expense in curing, package, carriage, and waste.
He styles the colouring substance itself cutbear, persio, or turnsole;
and distributes the lichens as follows:--1st. Those which left to
themselves, exposed to moderate heat and moisture, may be fixed without
a mordant upon wool or silk; such are the L. _cinereus_, _æmatonta_,
_ventosus_, _corallinus_, _westringii_, _saxatilis_, _conspassus_,
_barbatus_, _plicatus_, _vulpinus_, &c.
2. Those which develop a colouring matter fixable likewise without
mordant, but which require boiling and a complicated preparation; such
are the lichens _subcarneus_, _dillenii_, _farinaceus_, _jubatus_,
_furfuraceus_, _pulmonareus_, _cornigatus_, _cocciferus_, _digitatus_,
_ancialis_, _aduncus_, &c. Saltpetre or sea-salt are requisite to
improve the lustre and fastness of the dye given by this group to silk.
3. Those which require a peculiar process to develop their colour; such
as those which become purple through the agency of stale urine or
ammonia. Westring employed the following mode of testing:--He put three
or four drachms of the dried and powdered lichen into a flask; moistened
it with three or four measures of cold spring water; put the stuff to be
dyed into the mixture, and left the flask in a cool place. Sometimes he
added a little salt, saltpetre, quicklime, or sulphate of copper. If no
colour appeared, he then moistened the lichen with water containing one
twentieth of sal ammoniac, and one tenth of quicklime, and set the
mixture aside in a cool place from eight to fourteen days. There
appeared in most cases a reddish or violet coloured tint. Thus the
_lichen cinereus_ dyed silk a deep carmelite, and wool a light
carmelite; the _l. physodes_ gave a yellowish-gray; the _pustulatus_, a
rose red; _sanguinarius_, gray; _tartareus_, found on the rocks of
Norway, Scotland, and England, dyes a crimson-red. In Jutland, cutbear
is made from it, by grinding the dry lichen, sifting it, then setting it
to ferment in a close vessel with ammonia. The lichen must be of the
third year’s growth to yield an abundant dye; and that which grows near
the sea is the best. It loses half its weight by drying. A single person
may gather from twenty to thirty pounds a day in situations where it
abounds. No less than 2,239,685 pounds were manufactured at
Christiansand, Flekkefiort, and Fakrsund, in Norway, in the course of
the six years prior to 1812. Since more solid dyes of the same shade
have been invented, the archil has gone much into disuse. Federigo, of
Florence, who revived its use at the beginning of the fourteenth
century, made such an immense fortune by its preparation, that his
family became one of the grandees of that city, under the name of
Oricellarii, or Rucellarii. For more than a century Italy possessed the
exclusive art of making archil, obtaining the lichens from the islands
of the Mediterranean. According to an official report of 1831, Teneriffe
furnished annually 500 quintals (cwts.) of lichen; the Canary Isles,
400; Fuerta Santura, 300; Lancerot, 300; Gomera, 300; isle of Ferro,
800. This business belonged to the crown, and brought it a revenue of
1500 piastres. The farmers paid from 15 to 20 reals for the right to
gather each quintal. At that time the quintal fetched in the London
market 4_l._ sterling.
Archil is perhaps too much used in some cloth factories of England, to
the discredit of our dyes. It is said, that by its aid one third of the
indigo may be saved in the blue vat; but the colour is so much the more
perishable. The fine soft tint induced upon much of the black cloth by
means of archil is also deceptive. One half-pound of cutbear will dye
one pound of woollen cloth. A crimson red is obtained by adding to the
decoction of archil a little salt of tin (muriate), and passing the
cloth through the bath, after it has been prepared by a mordant of tin
and tartar. It must be afterwards passed through hot water.
ARDENT SPIRIT. Alcohol of moderate strength.
AREOMETER OF BAUMÉ. This scale is much used by the French authors.
Specific Gravity Numbers corresponding with Baumé’s Areometric Degrees.
+-----------------------------------------+---------------------------+
| Liquids denser than Water. | Less dense than Water. |
+------+------+------+------+------+------+------+------+------+------+
| | Spe- | | Spe- | | Spe- | | Spe- | | Spe- |
| De- |cific | De- |cific | De- |cific | De- |cific | De- |cific |
|grees.|gravi-|grees.|gravi-|grees.|gravi-|grees.|gravi-|grees.|gravi-|
| | ty. | | ty. | | ty. | | ty. | | ty. |
+------+------+------+------+------+------+------+------+------+------+
| 0 |1·0000| 26 |1·2063| 52 |1·5200| 10 |1·0000| 36 |0·8488|
| 1 |1·0066| 27 |1·2160| 53 |1·5353| 11 |0·9932| 37 |0·8439|
| 2 |1·0133| 28 |1·2258| 54 |1·5510| 12 |0·9865| 38 |0·8391|
| 3 |1·0201| 29 |1·2358| 55 |1·5671| 13 |0·9799| 39 |0·8313|
| 4 |1·0270| 30 |1·2459| 56 |1·5833| 14 |0·9733| 40 |0·8295|
| 5 |1·0340| 31 |1·2562| 57 |1·6000| 15 |0·9669| 41 |0·8249|
+------+------+------+------+------+------+------+------+------+------+
| 6 |1·0411| 32 |1·2667| 58 |1·6170| 16 |0·9605| 42 |0·8202|
| 7 |1·0483| 33 |1·2773| 59 |1·6344| 17 |0·9542| 43 |0·8156|
| 8 |1·0556| 34 |1·2881| 60 |1·6522| 18 |0·9480| 44 |0·8111|
| 9 |1·0630| 35 |1·2992| 61 |1·6705| 19 |0·9420| 45 |0·8066|
| 10 |1·0704| 36 |1·3103| 62 |1·6889| 20 |0·9359| 46 |0·8022|
+------+------+------+------+------+------+------+------+------+------+
| 11 |1·0780| 37 |1·3217| 63 |1·7079| 21 |0·9300| 47 |0·7978|
| 12 |1·0857| 38 |1·3333| 64 |1·7273| 22 |0·9241| 48 |0·7935|
| 13 |1·0935| 39 |1·3451| 65 |1·7471| 23 |0·9183| 49 |0·7892|
| 14 |1·1014| 40 |1·3571| 66 |1·7674| 24 |0·9125| 50 |0·7849|
| 15 |1·1095| 41 |1·3694| 67 |1·7882| 25 |0·9068| 51 |0·7807|
+------+------+------+------+------+------+------+------+------+------+
| 16 |1·1176| 42 |1·3818| 68 |1·8095| 26 |0·9012| 52 |0·7766|
| 17 |1·1259| 43 |1·3945| 69 |1·8313| 27 |0·8957| 53 |0·7725|
| 18 |1·1343| 44 |1·4074| 70 |1·8537| 28 |0·8902| 54 |0·7684|
| 19 |1·1428| 45 |1·4206| 71 |1·8765| 29 |0·8848| 55 |0·7643|
| 20 |1·1515| 46 |1·4339| 72 |1·9000| 30 |0·8795| 56 |0·7604|
+------+------+------+------+------+------+------+------+------+------+
| 21 |1·1603| 47 |1·4476| 73 |1·9241| 31 |0·8742| 57 |0·7656|
| 22 |1·1692| 48 |1·4615| 74 |1·9487| 32 |0·8690| 58 |0·7526|
| 23 |1·1783| 49 |1·4758| 75 |1·9740| 33 |0·8639| 59 |0·7487|
| 24 |1·1875| 50 |1·4902| 76 |2·0000| 34 |0·8588| 60 |0·7449|
| 25 |1·1968| 51 |1·4951| | | 35 |0·8538| 61 |0·7411|
+------+------+------+------+------+------+------+------+------+------+
ARGILLACEOUS EARTH. The earth of clay, called in chemistry alumina,
because it is obtained in greatest purity from alum.
ARGOL. Crude _tartar_; which see.
ARMS. Weapons of war. See FIRE-ARMS for an account of this manufacture.
ARRACK. A kind of intoxicating beverage made in India, by distilling the
fermented juice of the cocoa-nut, the palmyra tree, and rice in the
husk.
ARROW ROOT. The root of the _maranta arundinacea_, a plant which grows
in the West Indies, furnishes, by pounding in mortars and elutriation
through sieves, a peculiar species of starch, commonly but improperly
called arrow root. It is reckoned more nourishing than the starch of
wheat or potatoes, and is generally also freer from peculiar taste or
flavour. The fresh root consists, according to Benzon, of 0·07 of
volatile oil; 26 of starch (23 of which are obtained in the form of
powder, while the other 3 must be extracted from the parenchyma in a
paste by boiling water); 1·58 of vegetable albumen; 0·6 of a gummy
extract; 0·25 of chloride of calcium; 6 of insoluble fibrine; and 65·6
of water.
The import duty upon arrow root from our own colonies, is 1_s._ per
cwt.; from foreign parts, 2_d._ per lib. In 1835, 987,966 lbs. were
imported, of which only 6267 were exported; leaving 895,406 for home
consumption. The total revenue derived that year from arrow root, was
518_l._ See STARCH.
ARSENIC. This metal occurs native, in the state of oxide, and also
combined with sulphur under the improper name of _yellow_ and _red
arsenic_, or orpiment and realgar. Arsenic is associated with a great
many metallic ores; but it is chiefly extracted from those of cobalt, by
roasting, in which case the white oxide of arsenic, or, more correctly,
the arsenious acid is obtained. This acid is introduced occasionally in
small quantities into the materials of flint glass, either before their
fusion, or in the melting pot. It serves to peroxidize the iron oxide in
the sand, and thereby to purify the body of the glass; but an excess of
it makes the glass milky.
_Scheele’s green_ is a combination of this arsenious acid with oxide of
copper, or an arsenite of copper, and is described under this metal.
_Arseniate of potash_ is prepared, in the small way, by exposing to a
moderate heat in a crucible, a mixture of equal parts of white arsenic
and nitre in powder. After fusion, the crucible is to be cooled; the
contents being dissolved in hot water, and the solution filtered, will
afford regular crystals on cooling. According to M. Berzelius, they are
composed of arsenic acid, 63·87; potash, 26·16; and water, 9·97. It is
an acidulous salt, and is hence usually called the binarseniate, to
denote that its composition is 2 atoms of arsenic acid, and 1 of potash.
This article is prepared upon the great scale, in Saxony, by melting
nitre and arsenious acid together in a cylinder of cast-iron. A neutral
arseniate also is readily formed, by saturating the excess of acid in
the above salt with potash; it does not crystallize. The acid arseniate
is occasionally used in calico printing, for preventing certain points
of the cotton cloth from taking on the mordant; with which view it is
mixed up with gum water and pipe clay into a paste, which is applied to
such places with a block.
The extraction of arsenic from the cobalt ores, is performed at
Altenberg and Reichenstein, in Silesia, with an apparatus, excellently
contrived to protect the health of the smelters from the vapours of this
most noxious metallic sublimate.
[Illustration: 20]
[Illustration: 23]
_Figs._ 20. to 23. represent the arsenical furnaces at Altenberg. _Fig._
20. is a vertical section of the poison tower; _fig._ 21., a
longitudinal section of the subliming furnace A, with the adjoining
vault B, and the poison tower in part at _n_; _fig._ 22., the transverse
section of the furnace A, of _fig._ 21.; _fig._ 23., ground plan of the
furnace A, where the left half shows the part above, and the right the
part below the muffle or oblong retort; B´ is the upper view, B´´ the
ground plan of the vault B, of _fig._ 21.; _m_, _n_, the base of the
poison tower. In the several figures the same letters denote the same
objects: _a_ is the muffle; _b_ is its mouth for turning over the
arsenical schlich, or ground ore; _c c c_, fire draughts or flues; _d_,
an aperture for charging the muffle with fresh schlich; _e_, the smoke
chimney; _f_, two channels or flues for the ascent of the arsenious
fumes, which proceed to other two flues _g_, and then terminate both in
_h_, which conducts the fumes into the vault B. They issue by the door
_i_, into the conduit _k_, thence by _l_ into the spaces _m_, _n_, _o_,
_p_, _q_, _r_, of the tower. The incondensable gases escape by the
chimney, _s_. The cover _t_, is removed after completion of the
process, in order to push down the precipitate into the lower
compartments.
[Illustration: 22 21]
The arsenious schlichs, to the amount of 9 or 10 cwt. for one operation
(1 _roast-post_, or roasting round), are spread 2 or 3 inches thick upon
the bottom of the muffle, heated with a brisk fire to redness, then with
a gentler heat, in order to oxidize completely, before subliming, the
arsenical ore. With this view the air must have free entrance, and the
front aperture of the muffle must be left quite open. After 11 or 12
hours, the calcined materials are raked out by the mouth of the muffle,
and fresh ones are introduced by the openings indicated above, which are
closed during the sublimation.
The arsenious acid found in these passages, is not marketable till it be
re-sublimed in large iron pots, surmounted with a series of sheet iron
drums or cast-iron cylinders, upon the sides of which the arsenic is
condensed in its compact glassy form. The top cylinder is furnished with
a pipe, which terminates in a condensing chamber.
[Illustration: 24]
_Figs._ 24, 25. represent the arsenic refining furnaces at Reichenstein.
_Fig._ 24. shows at A, a vertical section of the furnace, the kettle,
and the surmounting drums or cylinders; over B it is seen in elevation;
_fig._ 25. is a ground plan of the four fireplaces. _a_ is the grate;
_b_, the ash pit; _c_, the openings for firing; _d_, the fire-place;
_e_, iron pots or kettles which are charged with the arsenious powder;
_f_, the fire flues proceeding to the common chimney _g_; _h_, iron
cylinders; _i_, caps; _k_, pipes leading to the poison vent _l_; _m_,
openings in the pipes for introducing the probing wires.
[Illustration: 25]
The conduct of the process is as follows:--The pot is filled nearly to
its brim with 3-1/2 cwt. of the arsenic meal, the cylinders are fitted
on by means of their handles, and luted together with a mixture of loam,
blood, and hair; then is applied first a gentle, and after half an hour,
a strong fire, whereby the arsenic is raised partly in the form of a
white dust, and partly in crystals; which, by the continuance of the
heat, fuse together into a homogeneous mass. If the fire be too feeble,
only a sublimate is obtained; but, if too violent, much of the arsenic
is volatilized into the pipes. The workmen judge by the heat of the
cylinders whether the operation be going on well or not. After 12 hours
the furnace is allowed to cool, provided the probe wires show that the
sublimation is over. The cylinders are then lifted off, and the
arsenious glass is detached from their inner surface. According to the
quality of the poison-flour, it yields from 3/4 to 7/8 of its weight of
the glass or enamel. Should any dark particles of metallic arsenic be
intermixed with the glass, a fresh sublimation must be had recourse to.
The following is the product in cwts. of arsenious acid, at Altenberg
and Reichenstein, in Silesia, in the years
+------------------+-----+-----+-----+-----+-----+-----+-----+-----+
| |1825.|1826.|1827.|1828.|1829.|1830.|1831.|1832.|
+------------------+-----+-----+-----+-----+-----+-----+-----+-----+
|White arsenic in a| | | | | | | | |
|glassy state | 2632| 1703| 2686| 1900| 2070| 2961| 3337| 2730|
|Sublimed arsenic | | | | | | | | |
|in powder | - | 27| 33| 31| 30| 44| 69| 38|
|Yellow arsenical | | | | | | | | |
|glass | 112| 11| 56| - | 86| 313| 60| 219|
|Red arsenical | | | | | | | | |
|glass | 3| - | - | - | 28| | | |
+------------------+-----+-----+-----+-----+-----+-----+-----+-----+
ARTESIAN WELLS. Under this name is designated a cylindrical perforation,
bored vertically down through one or more of the geological strata of
the earth, till it passes into a porous gravel bed containing water,
placed under such incumbent pressure as to make it mount up through the
perforation, either to the surface or to a height convenient for the
operation of a pump. In the first case, these wells are called spouting
or overflowing. This property is not directly proportional to the depth,
as might at first sight be supposed, but to the subjacent pressure upon
the water. We do not know exactly the period at which the borer or sound
was applied to the investigation of subterranean fountains, but we
believe the first overflowing wells were made in the ancient French
province of Artois, whence the name of Artesian. These wells, of such
importance to agriculture and manufactures, and which cost nothing to
keep them in condition, have been in use, undoubtedly, for several
centuries in the northern departments of France, and the north of Italy;
but it is not more than 50 or 60 years since they became known in
England and Germany. There are now a great many such wells in London and
its neighbourhood, perforated through the immensely thick bed of the
London clay, and even through some portions of the subjacent chalk. The
boring of such wells has given much insight into the geological
structure of many districts.
The formation of artesian wells depends on two things, essentially
distinct from each other: 1. On an acquaintance with the physical
constitution, or nature, of the mineral structure of each particular
country; and, 2. On the skilful direction of the processes by which we
can reach the water level, and of those by which we can promote its
ascent in the tube. We shall first treat of the best method of making
the well, and then offer some general remarks on the other subjects.
The operations employed for penetrating the soil are entirely similar to
those daily practised by the miner, in boring to find metallic veins;
but the well excavator must resort to peculiar expedients to prevent the
purer water, which comes from deep strata, mingling with the cruder
waters of the alluvial beds near the surface of the ground, as also to
prevent the small perforation getting eventually filled with rubbish.
The cause of overflowing wells has been ascribed to a variety of
circumstances. But, as it is now generally admitted that the numerous
springs which issue from the ground proceed from the infiltration of the
waters progressively condensed in rain, dew, snow, &c. upon the surface
of our globe, the theory of these interior streamlets becomes by no
means intricate; being analogous to that of syphons and water jets, as
expounded in the treatises of physics. The waters are diffused, after
condensation, upon the surface of the soil, and percolate downwards,
through the various pores and fissures of the geological strata, to be
again united subterraneously in veins, rills, streamlets, or expanded
films, of greater or less magnitude, or regularity. The beds traversed
by numerous disjunctions will give occasion to numerous interior
currents in all directions, which cannot be recovered, and brought to
the day; but when the ground is composed of strata of sand, or gravel
very permeable to water, separated by other strata nearly impervious to
it, reservoirs are formed to our hand, from which an abundant supply of
water may be spontaneously raised. In this case, as soon as the upper
stratum is perforated, the waters may rise, in consequence of the
hydrostatic pressure upon the lower strata, and even overflow the
surface in a constant stream, provided the level from which they proceed
be proportionally higher.
The sheets of water occur principally at the separation of two
contiguous formations; and, if the succession of the geological strata
be considered, this distribution of the water will be seen to be its
necessary consequence. In fact, the lower beds are frequently composed
of compact sandstone or limestone, and the upper beds of clay. In level
countries, the formations being almost always in horizontal-beds, the
waters which feed the artesian wells must come from districts somewhat
remote, where the strata are more elevated, as towards the secondary and
transition rocks. The copious streams condensed upon the sides of these
colder lands may be therefore regarded as the proper reservoirs of our
wells.
[Illustration: 26]
_Fig._ 26. represents the manner in which the condensed water of the
heavens distributes itself under the surface of our globe. Here we have
a geological section, showing the succession of the several formations,
and the sheets or laminæ of water that exist at their boundaries, as
well as in their sandy beds. The figure shows also very plainly that the
height to which the water reascends in the bore of a well depends upon
the height of the reservoir which supplies the sheet of water to which
the well is perforated. Thus the well A, having gone down to the aqueous
expanse A A, whose waters of supply are derived from the percolation M,
will afford rising waters, which will come to the surface; whilst in the
well B, supplied by the sheet P, the waters will spout above the
surface, and in the well C they will remain short of it. The same figure
shows that these wells often traverse sheets of water, which rise to
different heights. Thus, in the well C there are five columns of
ascending waters, which rise to heights proportional to the points
whence they take their origin. Several of these will be spouting or
overflowing, but some will remain beneath the surface.
[Illustration: 27]
The situation of the intended well being determined upon, a circular
hole is generally dug in the ground, about 6 or 8 feet deep, and 5 or 6
feet wide. In the centre of this hole the boring is carried on by two
workmen below, assisted by a labourer above, as shown in _fig._ 27.
[Illustration: 28 29]
The handle (_fig._ 28.) having a female screw in the bottom of its iron
shank, with a wooden bar or rail passing through the socket of the
shank, and a ring at top, is the general agent to which all the boring
implements are to be attached. A chisel (_fig._ 29.) is first employed,
and connected to this handle by its screw at top. If the ground is
tolerably soft, the weight of the two workmen bearing upon the cross
bar, and occasionally forcing it round, will soon cause the chisel to
penetrate; but if the ground is hard or strong, the workmen strike the
chisel down with repeated blows, so as to peck their way, often changing
their situation by walking round, which breaks the stones, or other hard
substances, that may happen to obstruct its progress.
The labour is very considerably reduced, by means of an elastic wooden
pole, placed horizontally over the well, from which a chain is brought
down, and attached to the ring of the handle. This pole is usually made
fast at one end, as a fulcrum, by being set into a heap of heavy loose
stones; at the other end the labourer above gives it a slight up and
down vibrating motion, corresponding to the beating motion of the
workmen below, by which means the elasticity of the pole in rising lifts
the handle and pecker, and thereby very considerably diminishes the
labour of the workmen. See _fig._ 27.
[Illustration: 30 31 32]
When the hole has been thus opened by a chisel, as far as its strength
would permit, the chisel is withdrawn, and a sort of cylindrical auger
(_fig._ 30.) attached to the handle (_fig._ 28.), for the purpose of
drawing up the dirt or broken stones which have been disturbed by the
chisel. A section of this auger is shown in _fig._ 31., by which the
internal valve will be seen. The auger being introduced into the hole,
and turned round by the workman, the dirt or broken stones will pass
through the aperture at bottom (shown at _fig._ 32.), and fill the
cylinder, which is then drawn up, and discharged at the top of the
auger, the valve preventing its escape at bottom.
[Illustration: 33 34 35 36 37]
In order to penetrate deeper into the ground, an iron rod, as _a_,
_fig._ 33., is now to be attached to the chisel, _fig._ 29., by screwing
on to its upper end, and the rod is also fastened to the handle, _fig._
28., by screwing into its socket. The chisel having thus become
lengthened, by the addition of the rod, it is again introduced into the
hole; and the operation of pecking or forcing it down, is carried on by
the workmen as before. When the ground has been thus perforated, as far
as the chisel and its rod will reach, they must be withdrawn, in order
again to introduce the auger, _fig._ 30., to collect and bring up the
rubbish; which is done by attaching it to the iron rod, in place of the
chisel. Thus as the hole becomes deepened, other lengths of iron rods
are added, by connecting them together, as _a b_ are in _fig._ 34. The
necessity of frequently withdrawing the rods from the holes, in order to
collect the mud, stones, or rubbish, and the great friction produced by
the rubbing of the tools against its sides, as well as the lengths of
rods augmenting in the progress of the operation, sometimes to the
extent of several hundred feet, render it extremely inconvenient, if not
impossible, to raise them by hand. A tripedal standard is, therefore,
generally constructed by three scaffolding poles tied together, over the
hole, as shown _fig._ 27., from the centre of which a wheel and axle, or
a pair of pully blocks is suspended, for the purpose of hauling up the
rods, and from which hangs the fork, _fig._ 35. This fork is to be
brought down under the shoulder, near the top of each rod, and made fast
to it by passing a pin through two little holes in the claws. The rods
are thus drawn up, about seven feet at a time, which is the usual
distance between each joint, and at every haul a fork, _fig._ 36., is
laid horizontally over the hole, with the shoulders of the lower rod
resting between its claws, by which means the rods are prevented from
sinking down into the hole again, while the upper length is unscrewed
and removed. In attaching and detaching these lengths of rod, a wrench,
_fig._ 37., is employed, by which they are turned round, and the screws
forced up to their firm bearing.
[Illustration: 38]
The boring is sometimes performed for the first sixty or a hundred feet,
by a chisel of 2-1/2 inches wide, and cleared out by a gouge of 2-1/4
diameter, and then the hole is widened by a tool, such as is shown at
_fig._ 38. This is merely a chisel, as _fig._ 29., four inches wide, but
with a guide, _a_, put on at its lower part, for the purpose of keeping
it in a perpendicular direction; the lower part is not intended to peck,
but to pass down the hole previously made, while the sides of the chisel
operate in enlarging the hole to four inches. The process, however, is
generally performed at one operation, by a chisel of four inches wide,
as _fig._ 29., and a gouge of three inches and three quarters, as _fig._
30.
It is obvious, that placing and displacing the lengths of rod, which is
done every time that the auger is required to be introduced or
withdrawn, must, of itself, be extremely troublesome, independent of the
labour of boring, but yet the operation proceeds, when no unpropitious
circumstances attend it, with a facility almost incredible. Sometimes,
however, rocks intercept the way, which require great labour to
penetrate; but this is always effected by pecking, which slowly
pulverises the stone. The most unpleasant circumstance attendant upon
this business is the occasional breaking of a rod into the hole, which
sometimes creates a delay of many days, and an incalculable labour in
drawing up the lower portion.
When the water is obtained in such quantities and of such quality as may
be required, the hole is dressed or finished by passing down it a
diamond chisel, funnel mouthed, with a triangular bit in its centre;
this makes the sides smooth previous to putting in the pipe. This chisel
is attached to rods, and to the handle, as before described; and, in its
descent, the workmen continually walk round, by which the hole is made
smooth and cylindrical. In the progress of the boring, frequent veins of
water are passed through; but, as these are small streams, and perhaps
impregnated with mineral substances, the operation is carried on until
an aperture is made into a main spring, which will flow up to the
surface of the earth. This must, of course, depend upon the level of its
source, which, if in a neighbouring hill, will frequently cause the
water to rise up, and produce a continued fountain. But if the altitude
of the distant spring happens to be below the level of the surface of
the ground where the boring is effected, it sometimes happens that a
well of considerable capacity is obliged to be dug down to that level,
in order to form a reservoir, into which the water may flow, and whence
it must be raised by a pump; while, in the former instance, a perpetual
fountain may be obtained. Hence, it will always be a matter of doubt, in
level countries, whether water can be procured, which would flow near to
or over the surface; if this cannot be effected, the process of boring
will be of little or no advantage, except as an experiment to ascertain
the fact.
In order to keep the strata pure, and uncontaminated with mineral
springs, the hole is cased, for a considerable depth, with a metallic
pipe, about a quarter of an inch smaller than the bore. This is
generally made of tin (though sometimes of copper or lead) in convenient
lengths; and, as each length is let down, it is held by a shoulder
resting in a fork, while another length is soldered to it; by which
means a continuous pipe is carried through the bore, as far as may be
found necessary, to exclude land springs, and to prevent loose earth or
sand from falling in, and choking the aperture.
Mr. John Good, of Tottenham, who had been extensively employed in boring
the earth for water, obtained a patent, in Aug. 1823, for certain
improved implements contrived by him to facilitate his useful labours; a
description of which cannot fail to be interesting.
[Illustration: 39 40 41 42]
The figures annexed exhibit these ingenious tools; _fig._ 39. is an
auger, to be connected by the screw-head to the length of rods by which
the boring is carried on. This auger is for boring in soft clay or sand;
it is cylindrical, and has a slit or opening from end to end, and a bit,
or cutting-piece at bottom. When the earth is loose or wet, an auger of
the same form is to be employed, but the slit or opening reduced in
width, or even without a slit or opening. A similar auger is used for
cutting through chalk; but the point or bit at bottom should then
project lower, and, for that purpose, some of these cylindrical augers
are made with moveable bits, to be attached by screws, which is
extremely desirable in grinding them to cutting edges. _Fig._ 40. is a
hollow conical auger, for boring loose sandy soils; it has a spiral
cutting edge coiled round it, which, as it turns, causes the loose soil
to ascend up the inclined plane, and deposit itself in the hollow
within. _Fig._ 41. is a hollow cylinder or tube, shown in section, with
a foot-valve, and a bucket to be raised by a rod and cord attached at
the top; this is a pumping tool, for the purpose of getting up water and
sand that would not rise by the auger. When this cylinder is lowered to
the bottom of the bore, the bucket is lifted up by the rod and cord, and
descends again by its own gravity, having a valve in the bucket, opening
upwards, like other lift pumps; which, at every stroke, raises a
quantity of water and sand in the cylinder equal to the stroke; the
ascent and descent of the bucket being limited by a guide-piece at the
top of the cylinder, and two small knobs upon the rod, which stop
against the cross-guide. _Fig._ 42. is a tool for getting up broken
rods. It consists of a small cylindrical piece at bottom, which the
broken rod slips through when it is lowered, and a small catch with a
knife-edge, acted upon by a back-spring. In rising, the tool takes hold
of the broken rod, and thereby enables the workmen at top to draw it up.
Another tool for the same purpose, is shown at _fig._ 43., which is like
a pair of tongs; it is intended to be slidden down the bore, and for the
broken rod to pass between the two catches, which, pressed by
back-springs, will, when drawn up, take fast hold of the broken rod.
[Illustration: 43 44 45 46]
_Fig._ 44. is a tool for widening the hole, to be connected, like all
the others, to the end of the length of rods passed down the bore; this
tool has two cutting-pieces extending on the sides at bottom, by which,
as the tool is turned round in the bore, the earth is peeled away.
_Fig._ 45. is a chisel, or punch, with a projecting piece to be used for
penetrating through stone; this chisel is, by rising and falling, made
to peck the stone, and pulverize it; the small middle part breaking it
away first, and afterwards the broad part coming into action. _Fig._ 46.
is another chisel, or punching tool, twisted on its cutting edge, which
breaks away a greater portion of the stone as it beats against it.
[Illustration: 47 48 49]
The manner of forcing down lengths of cast-iron pipe, after the bore is
formed, is shown at _fig._ 47.; the pipe is seen below in the socket, at
the end of which a block is inserted; and from this block a rod extends
upwards, upon which a weight at top slides. To this weight cords are
shown to be attached, reaching to the top of the bore; where the workmen
alternately raise the weight and let it fall, which, by striking upon
the block in its middle, beats down the pipe by a succession of strokes;
and when one length of pipe has, by these means, been forced down,
another length is introduced into the socket of the former. Another
tool for the same purpose is shown at _fig._ 48., which is formed like
an acorn; the raised part of the acorn strikes against the edge of the
pipe, and by that means, it is forced down the bore. When it happens
that an auger breaks in the hole, a tool similar to that shown at _fig._
49. is introduced; on one side of this tool a curved piece is attached,
for the purpose of a guide, to conduct it past the cylindrical auger;
and at the end of the other side is a hook, which, taking hold of the
bottom edge of the auger, enables it to be drawn up.
[Illustration: 50 51 52]
Wrought iron, copper, tin, and lead pipes, are occasionally used for
lining the bore; and as these are subject to bends and bruises, it is
necessary to introduce tools for the purpose of straightening their
sides. One of these tools is shown at _fig._ 50., which is a bow, and is
to be passed down the inside of the pipe, in order to press out any
dents. Another tool, for the same purpose, is shown at _fig._ 51., which
is a double bow, and may be turned round in the pipe for the purpose of
straightening it all the way down; at _fig._ 52., is a pair of clams,
for turning the pipe round in the hole while driving.
[Illustration: 53 54]
When loose stones lie at the bottom of the hole, which are too large to
be brought up by the cylindrical auger, and cannot be conveniently
broken, then it is proposed to introduce a triangular claw, as _fig._
53., the internal notches of which take hold of the stone, and as the
tool rises, bring it up. For raising broken rods, a tool like _fig._ 54.
is sometimes employed, which has an angular claw that slips under the
shoulder of the rod, and holds it fast while drawing up.
[Illustration: 55 56]
In raising pipes, it is necessary to introduce a tool into the inside of
the pipe, by which it will be held fast. _Fig._ 55. is a pine-apple tool
for this purpose; its surface is cut like a rasp, which passes easily
down into the pipe, but catches as it is drawn up; and by that means
brings the pipe with it. _Fig._ 56. is a spear for the same purpose,
which easily enters the pipe by springing; at the ends of its prongs
there are forks which stick into the metal as it is drawn up, and
thereby raise it.
These are the new implements, for which the patent was granted. In the
process of boring, there does not appear to be any thing new proposed;
but that these several tools are to be employed for boring, packing, and
otherwise penetrating, raising the earth, and extracting broken or
injured tools. There are also suggestions for employing long buckets,
with valves opening upward in their bottoms, for the purpose of drawing
water from these wells when the water will not flow over the surface;
also lift pumps, with a succession of buckets for the same purpose. But
as these suggestions possess little if any novelty, it cannot be
intended to claim them as parts of the patent.
ASPHALTUM. Native bitumen, so called from the lake Asphaltites.
ASSAY and ASSAYING. (_Coupellation_, Fr.; _Abtreiben auf der capelle_,
Germ.) This is the process by which the quality of gold and silver
bullion, coin, plate, or trinkets is ascertained with precision, or by
which the quantity of either or both these precious metals is determined
in any given alloy. It is, therefore, a case of chemical analysis, in
which peculiar methods are employed to attain the object in view with
accuracy and dispatch. Assaying has been also extended of late years, to
determine the quantity of palladium and platina in certain bullion and
gold dust brought from Brazil.
The art of assaying gold and silver _by the cupel_, is founded upon the
feeble affinity which these metals have for oxygen, in comparison with
copper, tin, and the other cheaper metals; and on the tendency which the
latter metals have to oxidize rapidly in contact with lead at a high
temperature, and sink with it into any porous earthy vessel in a thin
glassy or vitriform state. The porous vessel may be made either of
wood-ashes, freed from their soluble matter by washing with water; or,
preferably, of burned bones reduced to a fine powder.
The lead added to the silver or gold to be assayed, serves chiefly to
dissolve the oxidized copper, whence it appears that the quantity of
lead requisite for silver assays, ought to be directly proportional to
the quantity which the silver and copper would separately require. It
has been found by experiment, that 16 parts of lead are quite sufficient
to pass 1 of copper through the cupel; and that 3/10 of lead presents
the most suitable proportion for passing one of silver. From these
principles, however, if we should always regard the dose of lead to be
employed for any alloy as being equal to (16 × C) + (3/30 × S) we should
certainly commit an error. The phenomena of cupellation is of a more
complex nature. Long practice and delicate trials alone can guide to the
proper quantity of lead to be employed for every various state of the
alloy. The following Table contains the results of M. D’Arcet’s
elaborate experiments upon this subject:--
+---------------+--------+-------------+
| Alloy. |Lead for|Ratio of the |
+-------+-------+ 1 of |Copper to the|
|Silver.|Copper.| Alloy. | Lead. |
+-------+-------+--------+-------------+
| 1000 | 0 | 3/10| 0 |
| 950 | 50 | 3 | 1 : 60 |
| 900 | 100 | 7 | 1 : 70 |
| 800 | 200 | 10 | 1 : 50 |
| 700 | 300 | 12 | 1 : 40 |
| 600 | 400 | 14 | 1 : 35 |
| 500 | 500 |16 or 17| 1 : 32 |
| 400 | 600 |16 -- 17| 1 : 26·7 |
| 300 | 700 |16 -- 17| 1 : 22·9 |
| 200 | 800 |16 -- 17| 1 : 20 |
| 100 | 900 |16 -- 17| 1 : 17·8 |
| 0 | 1000 |16 -- 17| 1 : 16 |
+-------+-------+--------+-------------+
Bismuth may be used as a substitute for lead in cupellation; two parts
of it being nearly equivalent to three of lead. But its higher prices
will prevent its general introduction among assay masters.
We begin this assay process by weighing, in a delicate balance, a
certain weight of the metallic alloy; a gramme (= 15·444 gr.) is usually
taken in France, and 12 grains in this country. This weight is wrapped
up in a slip of lead foil or paper, should it consist of several
fragments. This small parcel, thus enveloped, is then laid in a watch
glass or a capsule of copper, and there is added to it the proportion of
lead suited to the quality of alloy to be assayed; there being less
lead, the finer the silver is presumed to be. Those who are much in the
habit of cupellation can make good guesses in this way; though it is
still guess work, and often leads to considerable error, for if too much
lead be used for the proportion of baser metal present, a portion of the
silver is wasted; but if too little, then the whole of the copper, &c.
is not carried off, and the button of fine silver remains more or less
impure. The most expert and experienced assayer by the cupel, produces
merely a series of approximate conjectural results, which fall short of
chemical demonstration and certainty in every instance. The lead must
be, in all cases, entirely free from silver, being such as has been
revived from pure litharge; otherwise errors of the most serious kind
would be occasioned in the assays.
The best cupels weigh 12-1/2 grammes, or 193 grains. The cupels allow
the fused oxides to flow through them as through a fine sieve, but are
impermeable to the particles of metals; and thus the former pass readily
down into their substance while the latter remain upon their surface; a
phenomenon owing to the circumstance of the glassy oxides moistening, as
it were, the bone-ash powder, whereas the metals can contract no
adherence with it. Hence also the liquid metals preserve a hemispherical
shape in the cupels, as quicksilver does in a cup of glass, while the
fused oxide spreads over, and penetrates their substance, like water. A
cupel may be regarded, in some measure, as a filter permeable only to
certain liquids.
If we put into a cupel, therefore, two metals, of which the one is
unalterable in the air, the other susceptible of oxidizement, and of
producing a very fusible oxide, it is obvious that, by exposing both to
a proper degree of heat, we shall succeed in separating them. We should
also succeed, though the oxide were infusible, by placing it in contact
with another one, which may render it fusible. In both cases, however,
the metal from which we wish to part the oxides must not be volatile; it
should also melt, and form a button at the heat of cupellation; for
otherwise it would continue disseminated, attached to the portion of
oxide spread over the cupel, and incapable of being collected.
The furnace and implements used for assaying in the Royal Mint and the
Goldsmiths’ Hall, in the city of London, are the following:--
[Illustration: 58 59]
A A A A, _fig._ 58., is a front elevation of an assay furnace; _a a_, a
view of one of the two iron rollers on which the furnace rests, and by
means of which it is moved forward or backward; _b_, the ash-pit; _c c_
are the ash-pit dampers, which are moved in a horizontal direction
towards each other for regulating the draught of the furnace; _d_, the
door, or opening, by which the cupels and assays are introduced into the
muffle; _e_, a moveable funnel or chimney by which the draught of the
furnace is increased. B B B B, _fig._ 59., is a perpendicular section
of _fig._ 58.; _a a_, end view of the rollers; _b_ the ash-pit; _c_ one
of the ash-pit dampers; _d_ the grate, over which is the plate upon
which the muffle rests, and which is covered with loam nearly one inch
thick; _f_ the muffle in section representing the situation of the
cupels; _g_ the mouth-plate, and upon it are laid pieces of charcoal,
which during the process are ignited, and heat the air that is allowed
to pass over the cupels, as will be more fully explained in the sequel;
_h_ the interior of the furnace, exhibiting the fuel.
The total height of the furnace is 2 feet 6-1/2 inches; from the bottom
to the grate, 6 inches; the grate, muffle, plate, and bed of loam, with
which it is covered, 3 inches; from the upper surface of the grate to
the commencement of the funnel _e_, _fig._ 58., 21-1/2 inches; the
funnel _e_, 6 inches. The square of the furnace which receives the
muffle and fuel is 11-3/4 inches by 15 inches. The external sides of the
furnace are made of plates of wrought iron, and are lined with a 2-inch
fire-brick.
[Illustration: 60]
C C C C, _fig._ 60., is a horizontal section of the furnace over the
grate, showing the width of the mouth-piece, or plate of wrought iron,
which is 6 inches, and the opening which receives the muffle-plate.
[Illustration: 61]
_Fig._ 61. represents the muffle or pot, which is 12 inches long, 6
inches broad inside; in the clear 6-3/4: in height 4-1/2 inside measure,
and nearly 5-1/2 in the clear.
[Illustration: 62]
_Fig._ 62., the muffle-plate, which is of the same size as the bottom of
the muffle.
[Illustration: 63]
_Fig._ 63. is a representation of the sliding-door of the mouth-plate,
as shewn at _d_, in _fig._ 58.
[Illustration: 64]
_Fig._ 64., a front view of the mouth-plate or piece, _d_, _fig._ 58.
[Illustration: 65]
_Fig._ 65., a representation of the mode of making, or shutting up with
pieces of charcoal, the mouth of the furnace.
_Fig._ 66., the teaser for cleaning the grate.
[Illustration: 66 67 68]
_Fig._ 67., a larger teaser, which is introduced at the top of the
furnace, for keeping a complete supply of charcoal around the muffle.
_Fig._ 68., the tongs used for charging the assays into the cups.
[Illustration: 69]
_Fig._ 69. represents a board of wood used as a register, and is divided
into 45 equal compartments, upon which the assays are placed previously
to their being introduced into the furnace. When the operation is
performed, the cupels are placed in the furnace in situations
corresponding to these assays on the board. By these means all confusion
is avoided, and without this regularity it would be impossible to
preserve the accuracy which the delicate operations of the assayer
require.
[Illustration: 70 71 72]
I shall now proceed to a description of a small assay furnace, invented
by Messrs. Anfrye and d’Arcet, of Paris. They term it, _Le Petit
Fourneau à Coupelle_. _Fig._ 70. represents this furnace, and it is
composed of a chimney or pipe of wrought iron _a_, and of the furnace B.
It is 17-1/2 inches high, and 7-1/4 inches wide. The furnace is formed
of three pieces; of a dome A; the body of the furnace B; and the ash-pit
C, which is used as the base of the furnace, _fig._ 70. and 71. The
principal piece, or body of the furnace, B, has the form of a hollow
tower, or of a hollow cylinder, flattened equally at the two opposite
sides parallel to the axis, in such a manner that the horizontal section
is elliptical. The foot which supports it is a hollow truncated cone,
flattened in like manner upon the two opposite sides, and having
consequently for its basis two ellipses of different diameters; the
smallest ought to be equal to that of the furnace, so that the bottom of
the latter may exactly fit it. The dome, which forms an arch above the
furnace, has also its base elliptical, whilst that of the superior
orifice by which the smoke goes out preserves the cylindrical form. The
tube of wrought iron is 18 inches long and 2-1/2 inches diameter, having
one of its ends a little enlarged, and slightly conical, that it may be
exactly fitted or jointed upon the upper part of the furnace dome _d_,
_fig._ 70. At the union of the conical and cylindrical parts of the
tube, there is placed a small gallery of iron, _e_, _fig._ 70, 71. See
also a plan of it, _fig._ 72. This gallery is both ingenious and useful.
Upon it are placed the cupels, which are thus annealed during the
ordinary work of the furnace, that they may be introduced into the
muffle, when it is brought into its proper degree of heat. A little
above this gallery is a door _f_, by which, if thought proper, the
charcoal could be introduced into the furnace; above that there is
placed at _g_ a throttle valve, which is used for regulating the draught
of the furnace at pleasure. Messrs. Anfrye and d’Arcet say, that, to
give the furnace the necessary degree of heat so as to work the assays
of gold, the tube must be about 18 inches above the gallery, for
annealing or heating the cupels. The circular opening _h_, in the dome,
_fig._ 70., and as seen in the section, _fig._ 71., is used to introduce
the charcoal into the furnace: it is also used to inspect the interior
of the furnace, and to arrange the charcoal round the muffle. This
opening is kept shut during the working of the furnace, with the
mouth-piece, of which the face is seen at _n_, _fig._ 71.
The section of the furnace, _fig._ 71., presents several openings, the
principal of which is that of the muffle; it is placed at _i_; it is
shut with the semicircular door _m_, _fig._ 70., and seen in the section
_m_, _fig._ 71. In front of this opening, is the table or shelf, upon
which the door of the muffle is made to advance or recede; the letter
_q_, _fig._ 71., shows the face, side, and cross section of the shelf,
which makes part of the furnace. Immediately under the shelf, is a
horizontal slit, _l_, which is pierced at the level of the upper part of
the grate, and used for the introduction of a slender rod of iron, that
the grate may be easily kept clean. This opening is shut at pleasure, by
the wedge represented at _k_, _fig._ 70. and 71.
Upon the back of the furnace is a horizontal slit _p_, _fig._ 71, which
supports the fire-brick, _s_, and upon which the end of the muffle, if
necessary, may rest; _u_, _fig._ 71., is the opening in the furnace
where the muffle is placed.
[Illustration: 73]
The plan of the grate of the furnace is an ellipse: _fig._ 73. is a
horizontal view of it. The dimensions of that ellipsis determine the
general form of the furnace, and thickness of the grate. To give
strength and solidity to the grate, it is encircled by a bar or hoop of
iron. There is a groove in which the hoop of iron is fixed. The holes of
the grate are truncated cones, having the greater base below, that the
ashes may more easily fall into the ash-pit. The letter _v_, _fig._ 71.,
shows the form of these holes. The grate is supported by a small bank or
shelf, making part of the furnace, as seen at _a_, _fig._ 71.
The ash-pit, C, has an opening _y_ in front, _fig._ 71.; and is shut
when necessary by the mouth-piece _r_, _fig._ 70. and 71.
To give strength and solidity to the furnace, it is bound with hoops of
iron, at _b_, _b_, _b_, _b_, _fig._ 70.
[Illustration: 74 75 76]
_Figs._ 74. 75. 76. are views of the muffle.
_Fig._ 77. is a view of a crucible for annealing gold.
[Illustration: 77 78 79 80]
_Figs._ 78. 79. 80. are cupels of various sizes, to be used in the
furnace. They are the same as those used by assayers in their ordinary
furnaces.
[Illustration: 81 82]
_Figs._ 81. and 82. are views of the hand-shovels, used for filling the
furnace with charcoal; they should be made of such size and form as to
fit the opening _h_, in _figs._ 70. and 71.
The smaller pincers or tongs, by which the assays are charged into the
cupels, and by which the latter are withdrawn from the furnace, as well
as the teaser for cleaning the grate of the furnace, are similar to
those used in the British Mint.
In the furnace of the Mint above described, the number of assays that
can be made at one time, is 45. The same number of cupels are put into
the muffle. The furnace is then filled with charcoal to the top, and
upon this are laid a few pieces already ignited. In the course of three
hours, a little more or less, according to circumstances, the whole is
ignited; during which period, the muffle, which is made of fire-clay, is
gradually heated to redness, and is prevented from cracking; which a
less regular or more sudden increase of temperature would not fail to
do: the cupels, also, become properly annealed. All moisture being
dispelled, they are in a fit state to receive the piece of silver or
gold to be assayed.
The greater care that is exercised in this operation, the less liable is
the assayer to accidents from the breaking of the muffle; which it is
both expensive and troublesome to fit properly into the furnace.
The cupels used in the assay process, are made of the ashes of burnt
bones (phosphate of lime). In the Royal Mint, the cores of ox-horn are
selected for this purpose; and the ashes produced are about four times
the expense of the bone-ash, used in the process of cupellation upon the
large scale. So much depends upon the accuracy of an assay of gold or
silver, where a mass of 15lbs. troy in the first, and 60lbs. troy in the
second instance, is determined by the analysis of a portion not
exceeding 20 troy grains, that every precaution which the longest
experience has suggested, is used to obtain an accurate result. Hence
the attention paid to the selection of the most proper materials for
making the cupels.
The cupels are formed in a circular mould made of cast steel, very
nicely turned, by which means they are easily freed from the mould when
struck. The bone-ash is used moistened with a quantity of water,
sufficient to make the particles adhere firmly together. The circular
mould is filled, and pressed level with its surface; after which, a
pestle or rammer, having its end nicely turned, of a globular or convex
shape, and of a size equal to the degree of concavity wished to be made
in the cupel for the reception of the assay, is placed upon the ashes in
the mould, and struck with a hammer until the cupel is properly formed.
These cupels are allowed to dry in the air for some time before they are
used. If the weather is fine, a fortnight will be sufficient.
An assay may prove defective for several reasons. Sometimes the button
or bead sends forth crystalline vegetations on its surface with such
force, as to make one suppose a portion of the silver may be thrown out
of the cupel. When the surface of the bead is dull and flat, the assay
is considered to have been too hot, and it indicates a loss of silver in
fumes. When the tint of the bead is not uniform, when its inferior
surface is bubbly, when yellow scales of oxide of lead remain on the
bottom of the cupel, and the bead adheres strongly to it, by these signs
it is judged that the assay has been too cold, and that the silver
retains some lead.
Lastly, the assay is thought to be good if the bead is of a round form,
if its upper surface is brilliant, if its lower surface is granular and
of a dead white, and if it separates readily from the cupel.
After the lead is put into the cupel, it gets immediately covered with a
coat of oxide, which resists the admission of the silver to be assayed
into the melted metal; so that the alloy cannot form. When a bit of
silver is laid on a lead bath in this predicament, we see it swim about
for a long time without dissolving. In order to avoid this result, the
silver is wrapped up in a bit of paper; and the carburetted hydrogen
generated by its combustion, reduces the film of the lead oxide, gives
the bath immediately a bright metallic lustre, and enables the two
metals readily to combine.
As the heat rises, the oxide of lead flows round about over the surface,
till it is absorbed by the cupel. When the lead is wasted to a certain
degree, a very thin film of it only remains on the silver, which causes
the iridescent appearance, like the colours of soap-bubbles; a
phenomenon, called by the old chemists, fulguration.
When the cupel cools in the progress of the assay, the oxygenation of
the lead ceases; and, instead of a very liquid vitreous oxide, an
imperfectly melted oxide is formed, which the cupel cannot absorb. To
correct a cold assay, the temperature of the furnace ought to be raised,
and pieces of paper ought to be put into the cupel, till the oxide of
lead which adheres to it, be reduced. On keeping up the heat, the assay
will resume its ordinary train.
Pure silver almost always vegetates. Some traces of copper destroy this
property, which is obviously due to the oxygen which the silver can
absorb while it is in fusion, and which is disengaged the moment it
solidifies. An excess of lead, by removing all the copper at an early
stage, tends to cause the vegetation.
The brightening is caused by the heat evolved, when the button passes
from the liquid to the solid state. Many other substances present the
same phenomenon.
In the above operation it is necessary to employ lead which is very
pure, or at least free from silver. That kind is called _poor lead_.
It has been observed at all times, that the oxide of lead carries off
with it, into the cupel, a little silver in the state of an oxide. This
effect becomes less, or even disappears, when there is some copper
remaining; and the more copper, the less chance there is of any silver
being lost. The loss of silver increases, on the other hand, with the
dose of lead. Hence the reason why it is so important to proportion the
lead with a precision which, at first sight, would appear to be
superfluous. Hence, also, the reason of the attempts which have, of late
years, been made to change the whole system of silver assays, and to
have recourse to a method exempt from the above causes of error.
M. d’Arcet, charged by the Commission of the Mint in Paris, to examine
into the justice of the reclamations made by the French silversmiths
against the public assays, ascertained that they were well founded; and
that the results of cupellation gave for the alloys between 897 and 903
thousandths (the limits of their standard coin) an inferior standard, by
from 4 to 5 thousandth parts, from the standard or title which should
result from the absolute or actual alloy.
The mode of assay shows, in fact, that an ingot, experimentally composed
of 900 thousandths of fine silver, and 100 thousandths of copper,
appears, by cupellation, to be only, at the utmost, 896 or 897
thousandths; whereas fine silver, of 1000 thousandths, comes out nearly
of its real standard. Consequently a director of the Mint, who should
compound his alloy with fine silver, would be obliged to employ 903 or
904 thousandths, in order that, by the assay in the laboratory of the
Mint, it should appear to have the standard of 900 thousandths. These 3
or 4 thousandths would be lost to him, since they would be disguised by
the mode of assay, the definitive criterion of the quantity of silver,
of which the government keeps count from the coiner of the money.
From experiments subsequently made by M. d’Arcet, it appears that silver
assays always suffer a loss of the precious metal, which varies,
however, with the standard of the alloy. It is 1 thousandth for fine
silver,
4·3 thousandths for silver of 900 thousandths,
4·9 -- for -- of 800 --
4·2 -- for -- of 500 --
and diminishes thereafter, progressively, till the alloy contains only
100 thousandths of silver, at which point the loss is only 0·4.
Assays requested by the Commission of the Paris Mint, from the assayers
of the principal Royal Mints in Europe, to which the same alloys,
synthetically compounded, were sent, afforded the results inscribed in
the following table.
+----------------------+----------+-----------------------------+
| | | Standards found for the |
| | Cities | Mathematical Alloys. |
|Names of the Assayers.|where they+---------+---------+---------+
| | reside. |950 mill.|900 mill.|800 mill.|
+----------------------+----------+---------+---------+---------+
|F. de Castenhole, Mint| | | | |
|Assayer |Vienna |946·20 |898·40 |795·10 |
|A. R. Vervaëz, Ditto |Madrid |944·40 |893·70 |789·20 |
|D. M. Cabrera, Assayer| | | | |
|in Spain |Ditto |944·40 |893·70 |788·60 |
|Assayer |Amsterdam |947·00 |895·00 |795·00 |
|Mr. Bingley, Assay | | | | |
|Master |London |946·25 |896·25 |794·25 |
|Mr. Johnson, Assayer |Ditto |933·33 |883·50 |783·33 |
|Inspector of the Mint |Utrecht |945·00 |896·50 |799·00 |
|Assayer of the Mint |Naples |945·00 |891·00 |787·00 |
|Assayer of Trade |Ditto |945·00 |891·00 |787·00 |
|Assayer of the Mint |Hamburgh |946·13/72|897·41/72|798·44/72|
|Ditto |Altona |942·1/4 |894·00 |790 |
+----------------------+----------+---------+---------+---------+
These results, as well as those in still greater numbers, obtained from
the ablest Parisian assayers, upon identical alloys of silver and
copper, prove that the mode of assay applied to them brings out the
standard too low; and further, that the quantity of silver masked or
disguised, is not uniform for these different eminent assay masters. An
alloy, for example, at the standard of 900 thousandths is judged at
M.
the Mint of Paris to have a standard of 895·6
At that of Vienna -- 898·4
-- Madrid -- 893·7
-- Naples -- 891·0
The fact thus so clearly made out of a loss in the standard of silver
bullion and coin, merits the most serious attention; and it will appear
astonishing, perhaps, that a thing recurring every day, should have
remained for so long a time in the dark. In reality, however, the fact
is not new; as the very numerous and well-made experiments of Tillet
from 1760 to 1763, which are related in the memoirs of the Academy of
Sciences, show, in the silver assays, a loss still greater than that
which was experienced lately in the laboratory of the Commission of the
French Mint. But he thought that, as the error was common to the nations
in general, it was not worth while or prudent to introduce any
innovation.
A mode of assaying, to give, with certainty, the standard of silver
bullion, should be entirely independent of the variable circumstances of
temperature, and the unknown proportions of copper, so difficult to
regulate by the mere judgment of the senses. The process by the humid
way, recommended by me to the Royal Mint in 1829, and exhibited as to
its principles before the Right Honourable John Herries, then Master, in
1830, has all the precision and certainty we could wish. It is founded
on the well-known property which silver has, when dissolved in nitric
acid, to be precipitated in a chloride of silver quite insoluble, by a
solution of sea salt, or by muriatic acid; but, instead of determining
the weight of the chloride of silver, which would be somewhat uncertain
and rather tedious, on account of the difficulty of drying it, we take
the quantity of the solution of sea salt which has been necessary for
the precipitation of the silver. To put the process in execution, a
liquor is prepared, composed of water and sea salt in such proportions
that 1000 measures of this liquor may precipitate, completely, 12 grains
of silver, perfectly pure, or of the standard 1000, previously dissolved
in nitric acid. The liquor thus prepared, gives, immediately, the true
standard of any alloy whatever, of silver and copper, by the weight of
it which may be necessary to precipitate 12 grains of this alloy. If,
for example 905 measures have been required to precipitate the 12 grains
of alloy, its standard would be 905 thousandths.
The process by the humid way is, so to speak, independent of the
operator. The manipulations are so easy; and the term of the operation
is very distinctly announced by the absence of any sensible nebulosities
on the affusion of sea salt into the silver solution, while there
remains in it 1/2 thousandth of metal. The process is not tedious, and
in experienced hands it may rival the cupel in rapidity; it has the
advantage over the cupel of being more within the reach of ordinary
operators, and of not requiring a long apprenticeship. It is
particularly useful to such assayers as have only a few assays to make
daily, as it will cost them very little time and expense.
By agitating briskly during two minutes, or thereby, the liquid rendered
milky by the precipitation of the chloride of silver, it may be
sufficiently clarified to enable us to appreciate, after a few moments
of repose, the disturbance that can be produced in it by the addition of
1000 of a grain of silver. Filtration is more efficacious than
agitation, especially when it is employed afterwards; it may be
sometimes used; but agitation, which is much more prompt, is generally
sufficient. The presence of lead and copper, or any other metal, except
mercury, has no perceptible influence on the quantity of sea salt
necessary to precipitate the silver; that is to say, the same quantity
of silver, pure or alloyed, requires for its precipitation a constant
quantity of the solution of sea salt.
Supposing that we operate upon a gramme of pure silver, the solution of
sea salt ought to be such that 100 centimetres cube may precipitate
exactly the whole silver. The standard of an alloy is given by the
number of thousandths of solution of sea salt necessary to precipitate
the silver contained in a gramme of the alloy.
When any mercury is accidentally present, which is, however, a rare
occurrence, it is made obvious by the precipitated chloride remaining
white when exposed to daylight, whereas when there is no mercury
present, it becomes speedily first grey and then purple. Silver so
contaminated must be strongly ignited in fusion before being assayed,
and its loss of weight noted. In this case, a cupel assay must be had
recourse to.
_Preparation of the Normal Solution of Sea Salt, when it is measured by
Weight._--Supposing the sea salt pure as well as the water, we have only
to take these two bodies in the proportion of 0·5427 k. of salt to
99·4573 k. of water, to have 100 k. of solution, of which 100 grammes
will precipitate exactly one gramme of silver. But instead of pure salt,
which is to be procured with difficulty, and which besides may be
altered readily by absorbing the humidity of the air, a concentrated
solution of the sea salt of commerce is to be preferred, of which a
large quantity may be prepared at a time, to be kept in reserve for use,
as it is wanted. _Instruction de Gay Lussac._
_Preparation of the Normal Solution of Sea Salt, when measured by
Volume._--The measure by weight has the advantage of being independent
of temperature, of having the same degree of precision as the balance,
and of standing in need of no correction. The measure by volume has not
all these advantages; but, by giving it sufficient precision, it is more
rapid, and is quite sufficient for the numerous daily assays of the
mint. This normal solution is so made, that a volume equal to that of
100 grammes of water, or 100 centimetres cube, at a determinate
temperature, may precipitate exactly one gramme of silver. The solution
may be kept at a constant temperature, and in this case the assay stands
in want of no correction; or if its temperature be variable, the assay
must be corrected according to its influence. These two circumstances
make no change in the principle of the process, but they are
sufficiently important to occasion some modifications in the apparatus.
Experience has decided the preference in favour of applying a correction
to a variable temperature.
We readily obtain a volume of 100 cubic centimetres by means of a
_pipette_, _fig._ 83., so gauged that when filled with water up to the
mark _a_, _b_, and well dried at its point, it will run out, at a
continuous efflux, 100 grammes of water at the temperature of 15 C. (59
Fah.). We say purposely at one efflux, because after the cessation of
the jet, the pipette may still furnish two or three drops of liquid,
which must not be counted or reckoned upon. The weight of the volume of
the normal solution, taken in this manner with suitable precautions,
will be uniform from one extreme to another, upon two centimetres and a
half, at most, or to a quarter of a thousandth, and the difference from
the mean will be obviously twice less, or one half. Let us indicate the
most simple manner of taking a measure of the normal solution of sea
salt.
[Illustration: 83 84]
After having immersed the beak _c_ of the pipette in the solution, we
apply suction by the mouth, to the upper orifice, and thereby raise the
liquid to _d_ above the circular line _a b_. We next apply neatly the
forefinger of one hand to this orifice, remove the pipette from the
liquid, and seize it as represented in _fig._ 84. The mark _a b_ being
placed at the level of the eye, we make the surface of the solution
become exactly a tangent to the plane _a b_. At the instant it becomes a
tangent, we leave the beak _c_ of the pipette open, by taking away the
finger that had been applied to it, and without changing any thing else
in the position of the hands, we empty it into the bottle which should
receive the solution, taking care to remove it whenever the efflux has
run out.
If after filling the pipette by suction, any one should find a
difficulty in applying the forefinger fast enough to the upper orifice,
without letting the liquid run down below the mark _a b_, he should
remove the pipette from the solution with its top still closed with his
tongue, then apply the middle finger of one of his hands to the lower
orifice; after which he may withdraw his tongue, and apply the
forefinger of the other hand to the orifice previously wiped. This mode
of obtaining a measure of normal solution of sea salt is very simple,
and requires no complex apparatus; but we shall indicate another
manipulation still easier, and also more exact.
In this new process the pipette is filled from the top like a bottle,
instead of being filled by suction, and it is moreover fixed. _Fig._ 85.
represents the apparatus. D and D´ are two sockets separated by a stop
cock R. The upper one, tapped interiorly, receives, by means of a cork
stopper L, the tube T, which admits the solution of sea salt. The lower
socket is cemented on to the _pipette_; it bears a small air-cock R´,
and a screw plug V, which regulates a minute opening intended to let the
air enter very slowly into the pipette. Below the stop-cock R´, a silver
tube N, of narrow diameter, soldered to the socket, leads the solution
into the _pipette_, by allowing the air, which it displaces, to escape
by the stop-cock R´. The screw plug, with the milled head V´, replaces
the ordinary screw by which the key of the stop-cock may be made to
press, with more or less force, upon its conical seat.
[Illustration: 85 86]
_Fig._ 86. represents, in a side view, the apparatus just described. We
here remark an air-cock R, and an opening _m_. At the extremity Q of the
same figure, the conical pipe T enters, with friction. It is by this
pipe that the air is sucked into the pipette, when it is to be filled
from its beak.
[Illustration: 87]
The _pipette_ is supported by two horizontal arms H K (_fig._ 87.)
moveable about a common axis A A, and capable of being drawn out or
shortened by the aid of two longitudinal slits. They are fixed steadily
by two screw nuts _e e´_, and their distance may be varied by means of
round bits of wood or cork interposed, or even by opposite screw nuts _o
o´_. The upper arm H is pierced with a hole, in which is fixed, by the
pressure of a wooden screw _v_, the socket of the _pipette_. The
corresponding hole of the lower arm is larger; and the beak of the
_pipette_ is supported in it by a cork stopper L. The apparatus is fixed
by its tail-piece P, by means of a screw to the corner of a wall, or any
other prop.
The manner of filling the pipette is very simple. We begin by applying
the fore-finger of the left hand to the lower aperture _c_; we then open
the two stop-cocks R and R´. Whenever the liquor approaches the neck of
the _pipette_, we must temper its influx, and when it has arrived at
some millimetres above the mark _a b_, we close the two stop-cocks, and
remove our forefinger. We have now nothing more to do than to regulate
the _pipette_; for which purpose the liquid must touch the line _a b_,
and must simply adhere externally to the beak of the _pipette_.
[Illustration: 88]
This last circumstance is easily adjusted. After taking away the finger
which closed the aperture _c_ of the _pipette_, we apply to this orifice
a moist sponge _m_, _fig._ 88., wrapped up in a linen rag, to absorb the
superfluous liquor as it drops out. This sponge is called the
handkerchief (_mouchoir_), by M. Gay Lussac. The _pipette_ is said to be
wiped when there is no liquor adhering to its point exteriorly.
For the convenience of operating, the handkerchief is fixed by friction
in a tube of tin plate, terminated by a cup, open at bottom to let the
droppings flow off into the cistern C, to which the tube is soldered. It
may be easily removed for the purpose of washing it; and, if necessary,
a little wedge of wood, _o_, can raise it towards the _pipette_.
To complete the adjustment of the _pipette_, the liquid must be made
merely to descend to the mark _a_, _b_. With this view, and whilst the
handkerchief is applied to the beak of the _pipette_, the air must be
allowed to enter very slowly by unscrewing the plug V, _fig._ 85.; and
at the moment of the contact the handkerchief must be removed, and the
bottle F, destined to receive the solution, must be placed below the
orifice of the _pipette_, _fig._ 88. As the motion must be made rapidly,
and without hesitation, the bottle is placed in a cylinder of tin-plate,
of a diameter somewhat greater, and forming one body with the cistern
and the handkerchief. The whole of this apparatus has for a basis a
plate of tinned iron, moveable between two wooden rulers R R, one of
which bears a groove, under which the edge of the plate slips. Its
traverses are fixed by two abutments _b b_, placed so that when it is
stopped by one of them, the beak of the _pipette_ corresponds to the
centre of the neck of the bottle, or is a tangent to the handkerchief.
This arrangement, very convenient for wiping the _pipette_ and emptying
it, gives the apparatus sufficient solidity, and allows of its being
taken away, and replaced without deranging any thing. It is obvious that
it is of advantage, when once the entry of the air into the _pipette_
has been regulated by the screw V, to leave it constantly open, because
the motion from the handkerchief to the bottle is performed with
sufficient rapidity to prevent a drop of the solution from collecting
and falling down.
[Illustration: 89]
_Temperature of the Solution._--After having described the manner of
measuring by volume the normal solution of the sea salt, we shall
indicate the most convenient means of taking the temperature. The
thermometer is placed in a tube of glass T, _fig._ 89., which the
solution traverses to arrive at the _pipette_. It is suspended in it by
a piece of cork, grooved on the four sides to afford passage to the
liquid. The scale is engraved upon the tube itself, and is repeated at
the opposite side, to fix the eye by the coincidence of this double
division at the level of the thermometric column. The tube is joined
below to another narrower one, through which it is attached by means of
a cork stopper B, in the socket of the stop-cock of the _pipette_. At
its upper part it is cemented into a brass socket, screw-tapped in the
inside, which is connected in its turn by a cock, with the extremity,
also tapped, of the tube above T, belonging to the reservoir of the
normal solution. The corks employed here as connecting links between the
parts of the apparatus, give them a certain flexibility, and allow of
their being dismounted and remounted in a very short time; but it is
indispensable to make them be traversed by a hollow tube of glass or
metal, which will hinder them from being crushed by the pressure they
are exposed to. If the precaution be taken to grease them with a little
suet and to fill their pores, they will suffer no leakage.
_Preservation of the Normal Solution of Sea Salt in metallic
Vessels._--M. Gay Lussac uses for this purpose a cylindrical vessel or
drum of copper, of a capacity of about 110 litres, having its inside
covered with a rosin and wax cement.
_Preparation of the Normal Solution of Sea Salt, measuring it by
Volume._--If the drum contains 110 litres, we should put only 105 into
it, in order that sufficient space may be left for agitating the liquor
without throwing it out. According to the principle that 100 centimetres
cube, or 1/10 of a litre of the solution should contain enough of sea
salt to precipitate a gramme of pure silver; and, admitting moreover,
13·516 for the prime equivalent of silver, and 7·335 for that of sea
salt, we shall find the quantity of pure salt that should be dissolved
in the 105 litres of water, and which corresponds to 105 × 10 = 1050
grammes of silver, to be by the following proportion:--
13·516 : 7·335 ∷ 1050 gramm. : x = 569·83 gr.
And as the solution of the sea salt of commerce, formerly mentioned,
contains approximately 250 grammes per kilogramme, we must take 2279·3
grammes of this solution to have 569·83 gram. of salt. The mixture being
perfectly made, the tubes and the _pipette_ must be several times washed
by running the solution through them, and putting it into the drum. The
standard of the solution must be determined after it has been well
agitated, supposing the temperature to remain uniform.
To arrive more conveniently at this result, we begin by preparing two
_decimes_ solutions; one of silver, and another of sea salt.
The decime solution of silver is obtained by dissolving 1 gramme of
silver in nitric acid, and diluting the solution with water till its
volume become a litre.
The decime solution of sea salt may be obtained by dissolving 0·543
grammes of pure sea salt in water, so that the solution shall occupy a
litre; but we shall prepare it even with the normal solution which we
wish to test, by mixing a measure of it with 9 measures of water; it
being understood that this solution is not rigorously equivalent to that
of silver, and that it will become so, only when the normal solution
employed for its preparation shall be finally of the true standard.
Lastly, we prepare beforehand several stoppered phials, in each of which
we dissolve 1 gramme of silver in 8 or 10 grammes of nitric acid. For
brevity’s sake we shall call these tests.
Now to investigate the standard of the normal solution, we must transfer
a _pipette_ of it into one of these test phials; and we must agitate the
liquors briskly to clarify them. After some instants of repose, we must
pour in 2 thousandths of the _decime_ solution of sea salt, which, we
suppose, will produce a precipitate. The normal liquor is consequently
too feeble; and we should expect this, since the sea salt employed was
not perfectly pure. We agitate and add 2 fresh thousandths, which will
also produce a precipitate. We continue thus by successive additions of
2 thousandths, till the last produces no precipitation. Suppose that we
have added 16 thousandths: the last two should not be reckoned, as they
produced no precipitate; the preceding two were necessary, but only in
part; that is to say, the useful thousandths added are above 12 and
below 14, or otherwise they are on an average equal to 13.
Thus, in the condition of the normal solution, we require 1013 parts of
it to precipitate one gramme of silver, while we should require only
1000. We shall find the quantity of concentrated solution of sea salt
that we should add, by noting that the quantity of solution of sea salt,
at first employed, viz. 2279·3 grammes, produced a standard of only 987
thousandths = 1000 - 13; and by using the following proportion:
987 : 2279·3 ∷ 13 : x = 30·02 grammes.
This quantity of the strong solution of salt, mixed with the normal
solution in the drum, will correct its standard, and we shall now see by
how much.
After having washed the tubes and the _pipette_, with the new solution,
we must repeat the experiment upon a fresh gramme of silver. We shall
find, for example, in proceeding only by a thousandth at a time, that
the first causes a precipitate, but not the second. The standard of the
solution is still too weak, and is comprised between 1000 and 1001; that
is to say, it may be equal to 1000-1/2, but we must make a closer
approximation.
We pour into the test bottle 2 thousandths of the _decime_ solution of
silver, which will destroy, perceptibly, two thousandths of sea salt,
and the operation will have retrograded by two thousandths; that is to
say, it will be brought back to the point at which it was first of all.
If, after having cleared up the liquor, we add half a thousandth of the
decime solution, there will necessarily be a precipitate, as we knew
beforehand, but a second will cause no turbidity. The standard of the
normal liquor will be consequently comprehended between 1000 and
1000-1/2, or equal to 1000-1/4.
We should rest content with this standard, but if we wish to correct it,
we may remark that the two quantities of solution of salt added, viz.
2279·3 gr. + 30·02 gr. = 2309·32 gr. have produced only 999·75
thousandths, and that we must add a new quantity of it corresponding to
1/4 of a thousandth. We make, therefore, the proportion
999·75 : 2309·32 ∷ 0·25 : x.
But since the first term differs very little from 1000, we may content
ourselves to have x by taking the 0·25/1000 of 2309·32, and we shall
find 0·577 gr. for the quantity of solution of sea salt to be added to
the normal solution.
It is not convenient to take exactly so small a quantity of solution of
sea salt by the balance, but we shall succeed easily by the following
process. We weigh 50 grammes of this solution, and we dilute it with
water; so that it occupies exactly half a litre, or 500 centimetres
cube. A _pipette_ of this solution, one centimetre cube in volume, will
give a decigramme of the primitive solution, and as such a small
_pipette_ is divided into twenty drops, each drop, for example, will
represent 5 milligrammes of the solution. We should arrive at quantities
smaller still by diluting the solution with a proper quantity of water;
but greater precision would be entirely needless.
The testing of the normal liquor just described, is, in reality, less
tedious than might be supposed. It deserves also to be remarked, that
liquor has been prepared for more than 1000 assays; and that, in
preparing a fresh quantity, we shall obtain directly its true standard,
or nearly so, if we bear in mind the quantities of water and solution of
salt which had been employed.
_Correction of the Standard of the Normal Solution of Sea Salt, when the
Temperature changes._--We have supposed, in determining the standard of
the normal solution of sea salt, that the temperature remained uniform.
The assays made in such circumstances, have no need of correction; but
if the temperature should change, the same measure of the solution will
not contain the same quantity of sea salt. Supposing that we have tested
the solution of the salt at the temperature of 15° C.; if, at the time
of making the experiment, the temperature is 18° C., for example, the
solution will be too weak on account of its expansion, and the _pipette_
will contain less of it by weight; if, on the contrary, the temperature
has fallen to 12°, the solution will be thereby concentrated and will
prove too strong. It is therefore proper to determine the correction
necessary to be made, for any variation of temperature.
To ascertain this point, the temperature of the solution of sea salt was
made successively to be 0°, 5°, 10°, 15°, 20°, 25°, and 30° C.; and
three _pipettes_ of the solution were weighed exactly at each of these
temperatures. The third of these weighings gave the mean weight of a
_pipette_. The corresponding weights of a _pipette_ of the solution,
were afterwards graphically interpolated from degree to degree. These
weights form the second column of the following table, intitled, _Table
of Correction for the Variations in the Temperature of the Normal
Solution of the Sea Salt_. They enable us to correct any temperature
between 0 and 30 degrees centigrade (32° and 86° Fahr.) when the
solution of sea salt has been prepared in the same limits.
Let us suppose, for example, that the solution has been made standard at
15°, and that at the time of using it, the temperature has become 18°.
We see by the second column of the table, that the weight of a measure
of the solution is 100·099 gr. at 15°, and 100·065 at 18°; the
difference 0·034 gr., is the quantity of solution less which has been
really taken; and of course we must add it to the normal measure, in
order to make it equal to one thousand _millièmes_. If the temperature
of the solution had fallen to 10 degrees, the difference of the weight
of a measure from 10 to 15 degrees would be 0·019 gr. which we must on
the contrary deduct from the measure, since it had been taken too large.
These differences of weight of a measure of solution at 15°, from that
of a measure at any other temperature, form the column 15° of the
table, where they are expressed in thousandths; they are inscribed on
the same horizontal lines as the temperatures to which each of them
relates with the sign + _plus_, when they must be added, and with the
sign - _minus_, when they must be subtracted. The columns 5°, 10°, 20°,
25°, 35°, have been calculated in the same manner for the cases in which
the normal solution may have been graduated to each of these
temperatures. Thus, to calculate the column 10, the number 100·118 has
been taken of the column of weights for a term of departure, and its
difference from all the numbers of the same column has been sought.
Table of Correction for the Variations in the Temperature of the Normal
Solution of the Sea Salt.
+-------+-------+-----+-----+-----+-----+-----+-----+
|Temper-|Weight.| 5° | 10° | 15° | 20° | 25° | 30° |
|ature. | | | | | | | |
+-------+-------+-----+-----+-----+-----+-----+-----+
| | gram. |mill.|mill.|mill.|mill.|mill.|mill.|
| 4 |100,109| 0·0|- 0·1|+ 0·1|+ 0·7|+ 1·7|+ 2·7|
| 5 |100,113| 0·0|- 0·1|+ 0·1|+ 0·7|+ 1·7|+ 2·8|
| 6 |100,115| 0·0| 0·0|+ 0·2|+ 0·8|+ 1·7|+ 2·8|
| 7 |110,118|+ 0·1| 0·0|+ 0·2|+ 0·8|+ 1·7|+ 2·8|
| 8 |100,120|+ 0·1| 0·0|+ 0·2|+ 0·8|+ 1·8|+ 2·8|
| 9 |100,120|+ 0·1| 0·0|+ 0·2|+ 0·8|+ 1·8|+ 2·8|
| 10 |100,118|+ 0·1| 0·0|+ 0·2|+ 0·8|+ 1·7|+ 2·8|
| 11 |100,116| 0·0| 0·0|+ 0·2|+ 0·8|+ 1·7|+ 2·8|
| 12 |100,114| 0·0| 0·0|+ 0·2|+ 0·8|+ 1·7|+ 2·8|
| 13 |100,110| 0·0|- 0·1|+ 0·1|+ 0·7|+ 1·7|+ 2·7|
| 14 |100,106|- 0·1|- 0·1|+ 0·1|+ 0·7|+ 1·6|+ 2·7|
| 15 |100,099|- 0·1|- 0·2|- 0·0|+ 0·6|+ 1·6|+ 2·6|
| 16 |100,090|- 0·2|- 0·3|- 0·1|+ 0·5|+ 1·5|+ 2·5|
| 17 |100,078|- 0·4|- 0·4|- 0·2|+ 0·4|+ 1·3|+ 2·4|
| 18 |100,065|- 0·5|- 0·5|- 0·3|+ 0·3|+ 1·2|+ 2·3|
| 19 |100,053|- 0·6|- 0·7|- 0·5|+ 0·1|+ 1·1|+ 2·2|
| 20 |100,039|- 0·7|- 0·8|- 0·6| 0·0|+ 1·0|+ 2·0|
| 21 |100,021|- 0·9|- 1·0|- 0·8|- 0·2|+ 0·8|+ 1·9|
| 22 |100,001|- 1·1|- 1·2|- 1·0|- 0·4|+ 0·6|+ 1·7|
| 23 | 99,983|- 1·3|- 1·4|- 1·2|- 0·6|+ 0·4|+ 1·5|
| 24 | 99,964|- 1·5|- 1·5|- 1·4|- 0·8|+ 0·2|+ 1·3|
| 25 | 99,944|- 1·7|- 1·7|- 1·6|- 1·0| 0·0|+ 1·1|
| 26 | 99,924|- 1·9|- 1·9|- 1·8|- 1·2|- 0·2|+ 0·9|
| 27 | 99,902|- 2·1|- 2·2|- 2·0|- 1·4|- 0·4|+ 0·7|
| 28 | 99,879|- 2·3|- 2·4|- 2·2|- 1·6|- 0·7|+ 0·4|
| 29 | 99,858|- 2·6|- 2·6|- 2·4|- 1·8|- 0·9|+ 0·2|
| 30 | 99,836|- 2·8|- 2·8|- 2·6|- 2·0|- 1·1| 0·0|
+-------+-------+-----+-----+-----+-----+-----+-----+
Several expedients have been employed to facilitate and abridge the
manipulations. In the first place, the phials for testing or assaying
the specimens of silver should all be of the same height and of the same
diameter. They should be numbered at their top, as well as on their
stoppers, in the order 1, 2, 3, &c. They may be ranged successively in
tens; the stoppers of the same series being placed on a support in their
proper order. Each two phials should, in their turn, be placed in a
japanned tin case (_fig._ 90.) with ten compartments duly numbered.
These compartments are cut out anteriorly to about half their height, to
allow the bottoms of the bottles to be seen. When each phial has
received its portion of alloy, through a wide-beaked funnel, there must
be poured into it about 10 grammes of nitric acid, of specific gravity
1·28, with a _pipette_, containing that quantity; it is then exposed to
the heat of a water bath, in order to facilitate the solution of the
alloy. The water bath is an oblong vessel made of tin plate, intended to
receive the phials. It has a moveable double bottom, pierced with small
holes, for the purpose of preventing the phials being broken, as it
insulates them from the bottom to which the heat is applied. The
solution is rapid; and, since it emits nitrous vapours in abundance, it
ought to be carried on under a chimney.
[Illustration: 90 91]
_The agitator._--_Fig._ 91. gives a sufficiently exact idea of it, and
may dispense with a lengthened description. It has ten cylindrical
compartments, numbered from 1 to 10. The phials, after the solution of
the alloy, are arranged in it in the order of their numbers. The
agitator is then placed within reach of the _pipette_, intended to
measure out the normal solution of sea salt, and a _pipette_ full of
this solution is put into each phial. Each is then closed with its glass
stopper, previously dipped in pure water. They are fixed in the cells of
the agitator by wooden wedges. The agitator is then suspended to a
spring R, and, seizing it with the two hands, the operator gives an
alternating rapid movement, which agitates the solution, and makes it,
in less than a minute, as limpid as water. This movement is promoted by
a spiral spring, B, fixed to the agitator and the ground; but this is
seldom made use of, because it is convenient to be able to transport the
agitator from one place to another. When the agitation is finished, the
wedges are to be taken out, and the phials are placed in order upon a
table furnished with round cells destined to receive them, and to screen
them from too free a light.
When we place the phials upon this table, we must give them a brisk
circular motion, to collect the chloride of silver scattered round their
sides; we must lift out their stoppers, and suspend them in wire rings,
or pincers. We next pour a thousandth of the decime solution into each
phial; and before this operation is terminated, there is formed in the
first phials, when there _should be_ a precipitate, a nebulous stratum,
very well marked, of about a centimetre in thickness.
At the back of the table there is a black board divided into
compartments numbered from 1 to 10, upon each of which we mark, with
chalk, the thousandths of the decime liquor put into the correspondent
phial. The thousandths of sea salt, which indicate an augmentation of
standard, are preceded by the sign +, and the thousandths of nitrate of
silver by the sign -.
When the assays are finished, the liquor of each phial is to be poured
into a large vessel, in which a slight excess of sea salt is kept; and
when it is full, the supernatant clear liquid must be run off with a
syphon.
The chloride of silver may be reduced without any perceptible loss.
After having washed it well, we immerse pieces of iron or zinc into it,
and add sulphuric acid in sufficient quantity to keep up a feeble
disengagement of hydrogen gas. The mass must not be touched. In a few
days the silver is completely reduced. This is easily recognised by the
colour and nature of the product; or by treating a small quantity of it
with water of ammonia, we shall see whether there be any chloride
unreduced; for it will be dissolved by the ammonia, and will afterwards
appear upon saturating the ammonia with an acid. The chlorine remains
associated with the iron or the zinc in a state of solution. The first
washings of the reduced silver must be made with an acidulous water, to
dissolve the oxide of iron which may have been formed, and the other
washings with common water. After decanting the water of the last
washing, we dry the mass, and add a little powdered borax to it. It must
be now fused. The silver being in a bulky powder is to be put in
successive portions into a crucible as it sinks down. The heat should be
at first moderate; but towards the end of the operation it must be
pretty strong to bring into complete fusion the silver and the scoriæ,
and to effect their complete separation. In case it should be supposed
that the whole of the silver had not been reduced by the iron or zinc, a
little carbonate of potash should be added to the borax. The silver may
also be reduced by exposing the chloride to a strong heat, in contact
with chalk and charcoal.
The following remarks by M. Gay Lussac, the author of the above method,
upon the effect of a little mercury in the humid assay, are important:--
It is well known that chloride of silver blackens the more readily as it
is exposed to an intense light, and that even in the diffused light of a
room, it becomes soon sensibly coloured. If it contains four to five
thousandths of mercury, it does not blacken; it remains of a dead white:
with three thousandths of mercury, there is no marked discolouring in
diffused light; with two thousandths it is slight; with one it is much
more marked, but still it is much less intense than with pure chloride.
With half a thousandth of mercury the difference of colour is not
remarkable, and is perceived only in a very moderate light.
But when the quantity of mercury is so small that it cannot be detected
by the difference of colour in the chloride of silver, it may be
rendered quite evident by a very simple process of concentration.
Dissolve one gramme of the silver supposed to contain 1/4 of a
thousandth of mercury, and let only 1/4 of it be precipitated, by adding
only 1/4 of the common salt necessary to precipitate it entirely. In
thus operating, the 1/4 thousandth of mercury is concentrated in a
quantity of chloride of silver four times smaller: it is as if the
silver having been entirely precipitated, four times as much mercury,
equal to two thousandths, had been precipitated with it.
In taking two grammes of silver, and precipitating only 1/4 by common
salt, the precipitate would be, with respect to the chloride of silver,
as if it amounted to four thousandths. By this process, which occupies
only five minutes, because exact weighing is not necessary, 1/10 of a
thousandth of mercury may be detected in silver.
It is not useless to observe, that in making those experiments the most
exact manner of introducing small quantities of mercury into a solution
of silver, is to weigh a minute globule of mercury, and to dissolve it
in nitric acid, diluting the solution so that it may contain as many
cubic centimetres as the globule weighs of centigrammes. Each cubic
centimetre, taken by means of a _pipette_, will contain one milligramme
of mercury.
If the ingot of silver to be assayed is found to contain a greater
quantity of mercury, one thousandth for example, the humid process ought
either to be given up in this case, or to be compared with cupellation.
When the silver contains mercury, the solution from which the mixed
chlorides are precipitated, does not readily become clear.
Silver containing mercury, put into a small crucible and mixed with lamp
black, to prevent the volatilization of the silver, was heated for three
quarters of an hour in a muffle, but the silver increased sensibly in
weight. This process for separating the mercury, therefore, failed. It
is to be observed, that mercury is the only metal which has thus the
power of disturbing the analysis by the humid way.
ASSAYING OF GOLD.--In estimating or expressing the fineness of gold, the
whole mass spoken of is supposed to weigh 24 carats of 12 grains each,
either real, or merely proportional, like the assayer’s weights; and the
pure gold is called fine. Thus, if gold be said to be 23 carats fine, it
is to be understood, that in a mass, weighing 24 carats, the quantity of
pure gold amounts to 23 carats.
In such small work as cannot be assayed by scraping off a part and
cupelling it, the assayers endeavour to ascertain its fineness or
quality by the touch. This is a method of comparing the colour and other
properties, of a minute portion of the metal, with those of small bars,
the composition of which is known. These bars are called touch needles,
and they are rubbed upon a smooth piece of black basaltes or pottery,
which, for this reason, is called the touchstone. Black flint slate will
serve the same purpose. Sets of gold needles may consist of pure gold;
of pure gold, 23-1/2 carats with 1/2 carat of silver; 23 carats of gold
with one carat of silver; 22-1/2 carats of gold with 1-1/2 carat of
silver; and so on, till the silver amounts to four carats; after which
the additions may proceed by whole carats. Other needles may be made in
the same manner, with copper instead of silver; and other sets may have
the addition, consisting either of equal parts of silver and copper, or
of such proportions as the occasions of business require. The
examination by the touch may be advantageously employed previous to
quartation, to indicate the quantity of silver necessary to be added.
In foreign countries, where trinkets and small work are required to be
submitted to the assay of the touch, a variety of needles is necessary;
but they are not much used in England. They afford, however, a degree of
information which is more considerable than might at first be expected.
The attentive assayer compares not only the colour of the stroke made
upon the touchstone by the metal under examination, with that produced
by his needle, but will likewise attend to the sensation of roughness,
dryness, smoothness, or greasiness, which the texture of the rubbed
metal excites, when abraded by the stone. When two strokes perfectly
alike in colour are made upon the stone, he may then wet them with
aquafortis, which will affect them very differently, if they be not
similar compositions; or the stone itself may be made red-hot by the
fire, or by the blowpipe, if thin black pottery be used; in which case
the phenomena of oxidation will differ, according to the nature and
quantity of the alloy. Six principal circumstances appear to affect the
operation of parting; namely, the quantity of acid used in parting, or
in the first boiling; the concentration of this acid; the time employed
in its application; the quantity of acid made use of in the _reprise_,
or second operation; its concentration; and the time during which it is
applied. From experiment it has been shown, that each of these
unfavourable circumstances might easily occasion a loss of from the half
of a thirty-second part of a carat, to two thirty-second parts. The
assayers explain their technical language by observing, that in the
whole mass consisting of twenty-four carats, this thirty-second part
denotes 1-768th part of the mass. It may easily be conceived, therefore,
that if the whole six circumstances were to exist, and be productive of
errors, falling the same way, the loss would be very considerable.
It is therefore indispensably necessary, that one uniform process should
be followed in the assays of gold; and it is a matter of astonishment,
that such an accurate process should not have been prescribed by
government for assayers, in an operation of such great commercial
importance, instead of every one being left to follow his own judgment.
The process recommended in the old French official report is as
follows:--twelve grains of the gold intended to be assayed must be mixed
with thirty grains of fine silver, and cupelled with 108 grains of lead.
The cupellation must be carefully attended to, and all the imperfect
buttons rejected. When the cupellation is ended, the button must be
reduced, by lamination, into a plate of 1-1/2 inches, or rather more, in
length, and four or five lines in breadth. This must be rolled up upon a
quill, and placed in a matrass capable of holding about three ounces of
liquid, when filled up to its narrow part. Two ounces and a half of very
pure aquafortis, of the strength of 20 degrees of Baumé’s areometer,
must then be poured upon it; and the matrass being placed upon hot
ashes, or sand, the acid must be kept gently boiling for a quarter of an
hour: the acid must then be cautiously decanted, and an additional
quantity of 1-1/2 ounces must be poured upon the metal, and slightly
boiled for twelve minutes. This being likewise carefully decanted, the
small spiral piece of metal must be washed with filtered river water, or
distilled water, by filling the matrass with this fluid. The vessel is
then to be reversed, by applying the extremity of its neck against the
bottom of a crucible of fine earth, the internal surface of which is
very smooth. The annealing must now be made, after having separated the
portion of water which had fallen into the crucible; and, lastly, the
annealed gold must be weighed. For the certainty of this operation, two
assays must be made in the same manner, together with a third assay upon
gold of twenty-four carats, or upon gold the fineness of which is
perfectly and generally known.
No conclusion must be drawn from this assay, unless the latter gold
should prove to be of the fineness of twenty-four carats exactly, or of
its known degree of fineness; for, if there be either loss or surplus,
it may be inferred, that the other two assays, having undergone the same
operation, must be subject to the same error. The operation being made
according to this process by several assayers, in circumstances of
importance, such as those which relate to large fabrications, the
fineness of the gold must not be depended upon, nor considered as
accurately known, unless all the assayers have obtained an uniform
result, without communication with each other. This identity must be
considered as referring to the accuracy of half the thirty-second part
of a carat. For, notwithstanding every possible precaution or
uniformity, it very seldom happens that an absolute agreement is
obtained between the different assays of one and the same ingot; because
the ingot itself may differ in its fineness in different parts of its
mass.
The phenomena of the cupellation of gold are the same as of silver, only
the operation is less delicate, for no gold is lost by evaporation or
penetration into the bone-ash, and therefore it bears safely the highest
heat of the assay furnace. The button of gold never vegetates, and need
not therefore be drawn out to the front of the muffle, but may be left
at the further end till the assay is complete. Copper is retained more
strongly by gold than it is by silver; so that with it 16 parts of lead
are requisite to sweat out 1 of copper; or, in general, twice as much
lead must be taken for the copper alloys of gold, as for those of
silver. When the copper is alloyed with very small quantities of gold,
cupellation would afford very uncertain results; we must then have
recourse to liquid analysis.
M. Vauquelin recommends to boil 60 parts of nitric acid at 22° Baumé, on
the spiral slip or cornet of gold and silver alloy, for twenty-five
minutes, and replace the liquid afterwards by acid of 32°, which must be
boiled on it for eight minutes. This process is free from uncertainty
when the assay is performed upon an alloy containing a considerable
quantity of copper. But this is not the case in assaying finer gold; for
then a little silver always remains in the gold. The surcharge which
occurs here is 2 or 3 thousandths; this is too much, and it is an
intolerable error when it becomes greater, which often happens. This
evil may be completely avoided by employing the following process of M.
Chaudet. He takes 0·500 of the fine gold to be assayed; cupels it with
1·500 of silver, and 1·000 of lead; forms, with the button from the
cupel, a riband or strip three inches long, which he rolls into a
cornet. He puts this into a mattrass with acid at 22° B., which he boils
for 3 or 4 minutes. He replaces this by acid of 32° B., and boils for
ten minutes; then decants off, and boils again with acid of 32°, which
must be finally boiled for 8 or 10 minutes.
Gold thus treated is very pure. He washes the cornet, and puts it entire
into a small crucible permeable to water; heats the crucible to dull
redness under the muffle, when the gold assumes the metallic lustre, and
the cornet becomes solid. It is now taken out of the crucible and
weighed.
When the alloy contains platinum, the assay presents greater
difficulties. In general, to separate the platinum from the gold with
accuracy, we must avail ourselves of a peculiar property of platinum;
when alloyed with silver, it becomes soluble in nitric acid. Therefore,
by a proper quartation of the alloy by cupellation, and boiling the
button with nitric acid, we may get a residuum of pure gold. If we were
to treat the button with sulphuric acid, however, we should dissolve
nothing but the silver. The copper is easily removed by cupellation.
Hence, supposing that we have a quaternary compound of copper, silver,
platinum, and gold, we first cupel it, and weigh the button obtained;
the loss denotes the copper. This button, treated by sulphuric acid,
will suffer a loss of weight equal to the amount of silver present. The
residuum, by quartation with silver and boiling with nitric acid, will
part with its platinum, and the gold will remain pure. For more detailed
explanations, see PLATINUM.
ATOMIC WEIGHTS or ATOMS, are the primal quantities in which the
different objects of chemistry, simple or compound, combine with each
other, referred to a common body, taken as unity. Oxygen is assumed by
some philosophers, and hydrogen by others, as the standard of
comparison. Every chemical manufacturer should be thoroughly acquainted
with the combining ratios which are, for the same two substances, not
only definite, but multiple; two great truths, upon which are founded
not merely the _rationale_ of his operations, but also the means of
modifying them to useful purposes. The discussion of the doctrine of
atomic weights, or prime equivalents, belongs to pure chemistry; but
several of its happiest applications are to be found in the processes of
art, as pursued upon the greatest scale. For many instructive examples
of this proposition, the various chemical manufactures may be consulted
in this Dictionary.
ATTAR OF ROSES. See OILS, VOLATILE, and PERFUMERY.
AURUM MUSIVUM. Mosaic gold, a preparation of tin; which see.
AUTOMATIC, a term which I have employed to designate such economic arts
as are carried on by self-acting machinery. The word “manufacture,” in
its etymological sense, means any system, or objects of industry,
executed by the hands; but in the vicissitude of language, it has now
come to signify every extensive product of art which is made by
machinery, with little or no aid of the human hand, so that the most
perfect manufacture is that which dispenses entirely with manual
labour.[4] It is in our modern cotton and flax mills that automatic
operations are displayed to most advantage; for there the elemental
powers have been made to animate millions of complex organs, infusing
into forms of wood, iron, and brass, an intelligent agency. And as the
philosophy of the fine arts, poetry, painting, and music, may be best
studied in their individual master-pieces, so may the philosophy of
manufactures in these its noblest creations.[5]
[4] Philosophy of Manufactures, p. 1.
[5] Ibid., p. 2.
The constant aim and effect of these automatic improvements in the arts
are philanthropic, as they tend to relieve the workmen either from
niceties of adjustment, which exhaust his mind and fatigue his eyes, or
from painful repetition of effort, which distort and wear out his frame.
A well arranged power-mill combines the operation of many work-people,
adult and young, in tending with assiduous skill, a system of productive
machines continuously impelled by a central force. How vastly conducive
to the commercial greatness of a nation, and the comforts of mankind,
human industry can become, when no longer proportioned in its results to
muscular effort, which is by its nature fitful and capricious, but when
made to consist in the task of guiding the work of mechanical fingers
and arms regularly impelled, with equal precision and velocity, by some
indefatigable physical agent, is apparent to every visitor of our
cotton, flax, silk, wool, and machine factories. This great era in the
useful arts is mainly due to the genius of Arkwright. Prior to the
introduction of his system, manufactures were every where feeble and
fluctuating in their development; shooting forth luxuriantly for a
season, and again withering almost to the roots like annual plants.
Their perennial growth then began, and attracted capital, in copious
streams, to irrigate the rich domains of industry. When this new career
commenced, about the year 1770, the annual consumption of cotton in
British manufactures was under four millions of pounds’ weight, and that
of the whole of Christendom was probably not more than ten millions.
Last year the consumption in Great Britain and Ireland was about two
hundred and seventy millions of pounds, and that of Europe and the
United States together, four hundred and eighty millions. In our
spacious factory apartments the benignant power of steam summons around
him his myriads of willing menials, and assigns to each the regulated
task, substituting, for painful muscular effort upon their part, the
energies of his own gigantic arm, and demanding, in return, only
attention and dexterity to correct such little aberrations as casually
occur in his workmanship. Under his auspices, and in obedience to
Arkwright’s polity, magnificent edifices, surpassing far in number,
value, usefulness, and ingenuity of construction, the boasted monuments
of Asiatic, Egyptian, and Roman despotism, have, within the short period
of fifty years, risen up in this kingdom, to show to what extent
capital, industry, and science, may augment the resources of a state,
while they meliorate the condition of its citizens. Such is the
automatic system, replete with prodigies in mechanics and political
economy, which promises, in its future growth, to become the great
minister of civilisation to the terraqueous globe, enabling this
country, as its heart, to diffuse, along with its commerce, the
life-blood of knowledge and religion to myriads of people still lying
“in the region and shadow of death.”[6] Of these truths, the present
work affords decisive evidence in almost every page.
[6] Philosophy of Manufactures, p. 18.
AUTOMATON. In the etymological sense, this word (self-working) signifies
every mechanical construction which, by virtue of a latent intrinsic
force, not obvious to common eyes, can carry on, for some time, certain
movements more or less resembling the results of animal exertion,
without the aid of external impulse. In this respect, all kinds of
clocks and watches, planetariums, common and smoke jacks, with a vast
number of the machines now employed in our cotton, silk, flax, and wool
factories, as well as in our dyeing and calico printing works, may be
denominated automatic. But the term, automaton, is, in common language,
appropriated to that class of mechanical artifices in which the
purposely concealed power is made to imitate the arbitrary or voluntary
motions of living beings. Human figures, of this kind, are sometimes
styled _Androides_, from the Greek term, _like a man_.
Although, from what we have said, clock-work is not properly placed
under the head automaton, it cannot be doubted that the art of making
clocks in its progressive improvement and extension, has given rise to
the production of automata. The most of these, in their interior
structure, as well as in the mode of applying the moving power, have a
distinct analogy with clocks; and these automata are frequently mounted
in connection with watch work. Towards the end of the 13th century,
several tower clocks, such as those at Strasburg, Lubeck, Prague,
Olmutz, had curious mechanisms attached to them. The most careful
historical inquiry proves that automata, properly speaking, are
certainly not older than _wheel_-clocks; and that the more perfect
structures of this kind are subsequent to the general introduction of
_spring_ clocks. Many accounts of ancient automata, such as the flying
doves of Archytas of Tarentum, Regiomontanus’s iron flies, the eagle
which flew towards the emperor Maximilian, in Nurenberg, in the year
1470, were deceptions, or exaggerated statements; for, three such
masterpieces of art would form now, with every aid of our improved
mechanisms, the most difficult of problems. The imitation of flying
creatures is extremely difficult, for several reasons. There is very
little space for the moving power, and the only material possessed of
requisite strength being metal, must have considerable weight. Two
automata, of the celebrated French mechanician, Vaucauson, first
exhibited in the year 1738, have been greatly admired; namely a
flute-player, five and a half feet high, with its cubical pedestal,
which played several airs upon the German flute; and that, not by any
interior tube-work, but through the actual blowing of air into the
flute, the motion of the tongue, and the skilful stopping of the holes
with the fingers; as also a duck, which imitated many motions of a
natural kind in the most extraordinary manner. This artist has had many
imitators, of whom the brothers, Droz of Chaux de Fonds, were the most
distinguished. Several very beautiful clock mechanisms of theirs are
known. One of them with a figure which draws; another playing on the
piano; a third which writes, besides numerous other combined automata.
Frederick Von Knauss completed a writing machine at Vienna, in the year
1760. It is now in the model cabinet of the Polytechnic Institute, and
consists of a globe 2 feet in diameter, containing the mechanism upon
which a figure 7 inches high sits, and writes upon a sheet of paper
fixed to a frame, whatever has been placed beforehand upon a regulating
cylinder. At the end of every line, it rises and moves its hand
sideways, in order to begin a new line.
Very complete automata have not been made of late years, because they
are very expensive; and by soon satisfying curiosity, they cease to
interest. Ingenious mechanicians find themselves better rewarded by
directing their talents to the self-acting machinery of modern
manufactures. We may notice here, however, the mechanical trumpeter of
Mälzl, at Vienna, and a similar work of Kauffmann, at Dresden. In French
Switzerland some artists continue to make minute automata which excite
no little wonder; such as singing canary birds, with various movements
of a natural kind; also little birds, sometimes hardly three quarters of
an inch long, in snuff-boxes and watches of enamelled gold. Certain
artificial figures which have been denominated automata, hardly deserve
the name; since trick and confederacy are more or less concerned in
their operation. To this head belong a number of figures apparently
speaking by mechanism; a clock which begins to strike, or to play, when
a person makes a sign of holding up his finger; this effect being
probably produced by a concealed green-finch, or other little bird,
instructed to set off the _détente_ of the wheel-work at a signal. It is
likely, also, that the chess player of Von Kempelen, which excited so
much wonder in the last century, had a concealed confederate. Likewise,
the very ingenious little figures of Tendler, father and son, which
imitated English horsemen and rope-dancers, constructed at Eisenerz, in
Styria, are probably no more true automata than the _fantoccini_, or
figures of puppets which are exhibited in great perfection in many towns
of Italy, especially at Rome.
The moving power of almost all automata is a wound-up steel spring;
because, in comparison with other means of giving motion, it takes up
the smallest room, is easiest concealed, and set a going. Weights are
seldom employed, and only in a partial way. The employment of other
moving powers is more limited; sometimes fine sand is made to fall on
the circumference of a wheel, by which the rest of the mechanism is
moved. For the same purpose water has been employed; and, when it is
made to fall into an air-chamber, it causes sufficient wind to excite
musical sounds in pipes. In particular cases quicksilver has been used,
as, for example, in the Chinese tumblers, which is only a physical
apparatus to illustrate the doctrine of the centre of gravity.
Figures are frequently constructed for playthings, which move by wheels
hardly visible. An example of this simplest kind of automaton which may
be introduced here, as illustrating the self-acting principles of
manufactures, is shown in the figure.
[Illustration: 92]
_Fig._ 92. exhibits the outlines of an automaton, representing a swan,
with suitably combined movements. The mechanism may be described, for
the sake of clearness of explanation, under distinct heads. The first
relates to the motion of the whole figure. By means of this part it
swims upon the water, in directions changed from time to time without
exterior agency. Another construction gives to the figure the faculty of
bending its neck on several occasions, and, to such an extent, that it
can plunge the bill and a portion of the head under water. Lastly, it is
made to move its head and neck slowly from side to side.
On the barrel of the spring, exterior to the usual ratchet wheel, there
is a main-wheel, marked 1, which works into the pinion of the wheel 2.
The wheel 2 moves a smaller one, shown merely in dotted lines, and on
the long axis of the latter, at either end there is a rudder, or
water-wheel, the paddles of which are denoted by the letter _a_. Both of
these rudder-wheels extend through an oblong opening in the bottom of
the figure down into the water. They turn in the direction of the arrow,
and impart a straight-forwards movement to the swan. The chamber, in
which these wheels revolve, is made water tight, to prevent moisture
being thrown upon the rest of the machinery. By the wheel 4, motion is
conveyed to the fly-pinion 5; the fly itself 6, serves to regulate the
working of the whole apparatus, and it is provided with a stop bar, not
shown in the engraving, to bring it to rest, or set it a-going at
pleasure. Here, as we may imagine, the path pursued is rectilinear, when
the rudder-wheels are made to work in a square direction. An oblique
bar, seen only in section at _b_, movable about its middle point,
carries at each end a web foot _c_, so that the direction of the bar
_b_, and of both feet towards the rudder wheels, determines the form of
the path which the figure will describe. The change of direction of that
oblique bar is effected without other agency. For this purpose, the
wheel 1 takes into the pinion 7, and this carries round the crown-wheel
8, which is fixed, with an eccentric disc 9, upon a common axis. While
the crown-wheel moves in the direction of the arrow, it turns the
smaller eccentric portion of the elliptic disc towards the lever _m_,
which, pressed upon incessantly by its spring, assumes, by degrees, the
position corresponding with the middle line of the figure, and
afterwards an oblique position; then it goes back again, and reaches its
first situation; consequently through the reciprocal turning of the bar
_h_, and the swim-foot, is determined and varied the path which the swan
must pursue. This construction is available with all automata, which
work by wheels; and it is obvious, that we may, by different forms of
the disc 9, modify, at pleasure, the direction and the velocity of the
turnings. If the disc is a circle for instance, then the changes will
take place less suddenly; if the disc has an outward and inward
curvature, upon whose edge the end of the lever presses with a roller,
the movement will take place in a serpentine line.
The neck is the part which requires the most careful workmanship. Its
outward case must be flexible, and the neck itself should therefore be
made of a tube of spiral wire, covered with leather, or with a feathered
bird-skin. The double line in the interior, where we see the triangles
_e e e_, denotes a steel spring made fast to the plate 10, which forms
the bottom of the neck; it stands loose, and needs to be merely so
strong as to keep the neck straight, or to bend it a little backwards.
It should not be equally thick in all points, but it should be weaker
where the first graceful bend is to be made; and, in general, its
stiffness ought to correspond to the curvature of the neck of this bird.
The triangles _e_ are made fast at their base to the front surface of
the spring; in the points of each there is a slit, in the middle of
which a movable roller is set, formed of a smoothly turned steel rod. A
thin catgut string _f_, runs from the upper end of the spring, where it
is fixed over all these rollers, and passes through an aperture pierced
in the middle of 10, into the inside of the rump. If the catgut be drawn
straight back towards _f_, the spring, and consequently the neck, must
obviously be bent, and so much the more, the more tightly _f_ is pulled,
and is shortened in the hollow of the neck. How this is accomplished by
the wheel-work will presently be shown. The wheel 11 receives its motion
from the pinion _s_, connected with the main wheel 1. Upon 11 there is,
moreover, the disc 12, to whose circumference a slender chain is
fastened. When the wheel 11 turns in the direction of the arrow, the
chain will be so much pulled onwards through the corresponding advance
at the point at 12, till this point has come to the place opposite to
its present situation, and, consequently, 11 must have performed half a
revolution. The other end of the chain is hung in the groove of a very
movable roller 14; and this will be turned immediately by the unwinding
of the chain upon its axis. There turns, in connection with it, however,
the large roller 13, to which the catgut _f_ is fastened; and as this is
pulled in the direction of the arrow, the neck will be bent until the
wheel 11 has made a half revolution. Then the drag ceases again to act
upon the chain and the catgut; the spring in the neck comes into play:
it becomes straight, erects the neck of the animal, and turns the
rollers 13 and 14, back into their first position.
The roller 13 is of considerable size, in order that through the slight
motion of the roller 14, a sufficient length of the catgut may be wound
off, and the requisite shortening of the neck may be effected; which
results from the proportion of the diameters of the rollers 11, 13, and
14. This part of the mechanism is attached as near to the side of the
hollow body as possible, to make room for the interior parts, but
particularly for the paddle-wheels. Since the catgut, _f_, must pass
downwards on the middle from 10, it is necessary to incline it sideways
and outwards towards 13, by means of some small rollers.
The head, constituting one piece with the neck, will be depressed by the
complete flexure of this; and the bill, being turned downwards in front
of the breast, will touch the surface of the water. The head will not be
motionless; but it is joined on both sides by a very movable hinge, with
the light ring, which forms the upper part of the clothing of the neck.
A weak spring, _g_, also fastened to the end of the neck, tends to turn
the head backwards; but in the present position it cannot do so, because
a chain at _g_, whose other end is attached to the plate 10, keeps it on
the stretch. On the bending of the neck, this chain becomes slack; the
spring _g_ comes into operation, and throws the head so far back, that,
in its natural position, it will reach the water.
Finally, to render the turning of the head and the neck practicable, the
latter is not closely connected with the rump, while the plate 10 can
turn in a cylindrical manner upon its axis, but cannot become loose
outwardly. Moreover, there is upon the axis of the wheel 1, and behind
it (shown merely as a circle in the engraving) a bevel wheel, which
works into a second similar wheel, 15, so as to turn it in a horizontal
direction. The pin 16, of the last wheel, works upon a two-armed lever
19, movable round the point _h_, and this lever moves the neck by means
of the pin 17. The shorter arm of the lever 19 has an oval aperture in
which the pin 16 stands. As soon as this, in consequence of the movement
of the bevel-wheel 15, comes into the dotted position, it pushes the
oval ring outwards on its smaller diameter, and thereby turns the lever
upon the point _h_, into the oblique direction shown by the dotted
lines. The pin 16, having come on its way right opposite to its present
position, sets the lever again straight. Then the lever, by the further
progress of the pin in its circular path, is directed outwards to the
opposite side; and, at last, when 15 has made an entire revolution, it
is quite straight. The longer arm of the lever follows, of course, these
alternating movements, so that it turns the neck upon its plate 10, by
means of the pin 17; and, as 18 denotes the bill, this comes into the
dotted position. It may be remarked in conclusion, that the drawing of
_fig._ 92. represents about half the size of which the automaton may be
constructed, and that the body may be formed of thin sheet-copper or
brass.
[Illustration: 94 95]
_Fig._ 93, 94, 95. show the plan of a third automaton. A horse which
moves its feet in a natural way, and draws a carriage with two figures
sitting in it. The man appears to drive the horse with a whip; the woman
bends forwards from him in front. The four wheels of the carriage have
no connection with the moving mechanism. In _fig._ 95., some parts are
represented upon a larger scale. The wheel 1, in _fig._ 93. operates
through the two carrier wheels upon the wheels marked 4 and 5. By means
of the axis of these two wheels, the feet are set in motion. The left
fore-foot, _a_, then the right hinder foot, move themselves backwards,
and take hold of the ground with small tacks in their hoofs, while the
two other legs are bent and raised, but no motion of the body takes
place. The carriage, however, with which the horse is connected,
advances upon its wheels. By studying the mechanism of the foot, _a_,
and the parts connected with it, we can readily understand the
principles of the movement. The axis of wheel 4 is crank-shaped, on both
sides, where it has to operate directly on the fore feet; but for each
foot, it is bent in an opposite direction, as is obvious in the front
view _fig._ 94. This crank, or properly its part furthest from the axis,
serves instead of the pin 16, in the swan, and moves like it in an oval
spot, _p_, _fig._ 93. a two-armed lever, which gives motion through
tooth-work, but not as in the swan, by means of a second pin. This
wheel-work renders the motion smoother. The above lever has its fulcrum
at _n_, _fig._ 93., about which it turns alternately, to the one and the
other side, by virtue of the rotation of the wheel 4. The toothed arch,
or the half-wheel on the under side, lays hold of a shorter lever, in a
similar arch, upon the upper joint of the foot, which is moved forwards
and backwards upon the pivot _m_. In virtue of the motions in the
direction of the arrow, the foot _a_ will move itself first obliquely
backwards, without bending, and the body will thereby bend itself
forwards. When the right hind foot makes the same motion, both the other
feet are raised and bent. The joints of the foot at _d_ and _e_ are
formed of hinges, which are so constructed that they can yield no
farther than is necessary at every oblique position of the foot. With
the continued rotation of the wheel 4, the lever turns itself about _n_,
in an inverted direction inwards, and impels the uppermost foot-joint
forwards, so that it forms an acute angle with the body in front. The
foot is now twice bent upon its joints. This takes place by the traction
of the chain _t_, which is led over rollers (as the drawing shows) to
the foot, and is there fastened. As its upper end has its fixed point in
the interior of the body, it is therefore drawn by the eccentric pin _r_
standing in the vicinity of _m_, and thus bends the foot at the hinges.
If there were space for it, a roller would answer better than a pin. By
the recedure of the uppermost joint into the first position, the tension
of the chain _t_ ceases again of itself, while the pin _r_ removes from
it, and the foot is again extended in a straight line by the small
springs operating upon its two under parts, which were previously bent
stiffly by the chain. By the aid of the figures with this explanation,
it will be apparent that all the fore feet have a similar construction,
that the proper succession of motions will be effected through the
toothed arcs, and the position of the cranks on the axis of the wheels 4
and 5, and hence the advance of the figure must follow. The wheel 6 puts
the fly 7 in motion, by means of the small wheel marked 1; on the fixed
points of the 4 chains, by means of a ratchet-wheel and a catch, the
necessary tension will again be produced when the chains have been drawn
out a little. There is sufficient room for a mechanism which could give
motion to the head and ears, were it thought necessary.
The proper cause of the motions may now be explained. In _fig._ 95.,
_a_, is a wheel connected with the wound-up spring, by which the motion
of the two human figures, and also, if desired, that of the horse may be
effected. The axis of the wheel _b_ carries a disc with pins, which
operate upon the two-armed lever with its fulcrum _e_, and thus cause
the bending of the upper part of one of the figures, which has a hinge
at _f_. On the axis of that wheel there is a second disc _c_, for giving
motion to the other figure; which, for the sake of clearness, is shown
separate, although it should sit alongside of its fellow. On the upper
end of the double-armed lever _d_, there is a cord whose other end is
connected with the moving arm, in the situation _i_, and raises it
whenever a pin in the disc presses the under part of the lever. A spring
_h_ brings the arm back into the original position, when a pin has
passed from the lever, and has left it behind. The pins at _c_ and _d_
may be set at different distances from the middle of the disc, whereby
the motions of the figures by every contact of another pin, are varied,
and are therefore not so uniform, and consequently more natural.
For the connexion of both mechanisms, namely, the carriage with the
horse, various arrangements may be adopted. Two separate traction
springs should be employed; one at _a_, _fig._ 95., in the coach-seat;
the other in the body of the horse. In the coach-seat at _b_, the fly
with its pinion, as well as a ratchet-wheel, is necessary. By means of
the shaft, the horse is placed in connexion with the waggon. It may,
however, receive its motion from the spring in the carriage, in which
case one spring will be sufficient. Upon the latter plan the following
construction maybe adopted:--To the axis of _b_, _fig._ 95., a bevel
wheel is to be attached, and from this the motion is to be transmitted
to the bottom of the carriage with the help of a second bevel wheel _s_,
connected with a third bevel wheel _t_. This again turns the wheel _u_,
whose long axis _v_ goes to the middle of the horse’s body, in an
oblique direction, through the hollow shaft. This axis carries an
endless screw 9, _fig._ 93., with very oblique threads, which works into
the little wheel 8, corresponding to the wheel 1, through an opening in
the side of the horse, and in this way sets the mechanism of the horse
a-going. With this construction of _fig._ 95., a spring of considerable
strength is necessary, or if the height of the carriage-seat does not
afford sufficient room, its breadth will answer for placing two weaker
springs alongside of each other upon a common barrel.
AXE. A tool much used by carpenters for cleaving, and roughly
fashioning, blocks of wood. It is a flat iron wedge, with an oblong
steel edge, parallel to which, in the short base, is a hole for
receiving and holding fast the end of a strong wooden handle. In the
cooper’s _adze_, the oblong edge is at right angles to the handle, and
is slightly curved up, or inflected towards it.
AXLES, of carriages; for their latest improvements, see WHEEL CARRIAGES.
AXUNGE. Hog’s lard; see FAT and OILS.
AZOTIZED, said of certain vegetable substances, which, as containing
azote, were supposed at one time to partake, in some measure, of the
animal nature; most animal bodies being characterised by the presence of
much azote in their composition. The vegetable products, indigo,
cafeine, gluten, and many others, contain abundance of azote.
AZURE, the fine blue pigment, commonly called smalt, is a glass coloured
with oxide of cobalt, and ground to an impalpable powder.
The manufacture of azure, or smalt, has been lately improved in Sweden,
by the adoption of the following process:--
The cobalt ore is first roasted till the greater part of the arsenic is
driven off. The residuary impure black oxide is mixed with as much
sulphuric acid (concentrated) as will make it into a paste, which is
exposed at first to a moderate heat, then to a cherry-red ignition for
an hour. The sulphate thus obtained is reduced to powder, and dissolved
in water. To the solution, carbonate of potash is gradually added, in
order to separate the remaining portion of oxide of iron; the quantity
of which depends upon the previous degree of calcination. If it be not
enough oxidized, the iron is difficult to be got rid of.
When, from the colour of the precipitate, we find that the potash
separates merely carbonate of cobalt, it is allowed to settle, the
supernatant liquor is decanted, and precipitated, by means of a solution
of silicate of potash, prepared as follows:--
Ten parts of potash are carefully mixed with fifteen parts of finely
ground flints or sand, and one part of pounded charcoal. This mixture is
melted in a crucible of brick clay, an operation which requires steady
ignition during 5 or 6 hours. The mass, when melted and pulverized, may
be easily dissolved in boiling water, adding to it, by little at a time,
the glass previously ground. The filtered solution is colourless, and
keeps well in the air, if it contains one part of glass for 5 or 6 of
water. The silicate of cobalt, which precipitates upon mixing the two
solutions, is the preparation of cobalt most suitable for painting upon
porcelain, and for the manufacture of blue glass. See COBALT.
B.
BABLAH. The rind or shell which surrounds the fruit of the _mimosa
cineraria_; it comes from the East Indies, as also from Senegal, under
the name of Neb-neb. It contains gallic acid, tannin, a red colouring
matter, and an azotized substance; but the proportion of tannin is
smaller than in sumach, galls, and _knoppern_ (gall-nuts of the common
oak) in reference to that of gallic acid, which is considerable in the
bablah. It has been used, in dyeing cotton, for producing various shades
of drab; as a substitute for the more expensive astringent die-stuffs.
BAGASSE. The sugar-cane, in its dry, crushed state, as delivered from
the sugar-mill. It is much employed for fuel in the colonial
sugar-houses.
BAKING. (_Cuire_, Fr. _Backen_, Germ.) The exposure of any body to such
a heat as will dry and consolidate its parts without wasting them. Thus
wood, pottery, and porcelain, are baked, as well as bread.
BALANCE. To conduct arts, manufactures, and mines, with judgment and
success, recourse must be had, at almost every step, to a balance.
Experience proves that all material bodies, existing upon the surface of
the earth, are constantly solicited by a force which tends to bring them
to its centre, and that they actually fall towards it when they are free
to move. This force is called gravity. Though the bodies be not free,
the effort of gravity is still sensible, and the resultant of all the
actions which it exercises upon their material points, constitutes what
is popularly called their _weight_. These weights are, therefore, forces
which may be compared together, and by means of machines may be made to
correspond or be counterpoised.
To discover whether two weights be equal, we must oppose them to each
other in a machine where they act in a similar manner, and then see if
they maintain an equilibrium; for example, we fulfil this condition if
we suspend them at the two extremities of a lever, supported at its
centre, and whose arms are equal. Such is the general idea of a balance.
The beam of a good balance ought to be a bar of well-tempered steel, of
such form as to secure perfect inflexibility under any load which may be
fitly applied to its extremities. Its arms should be quite equal in
weight and length upon each side of its point of suspension; and this
point should be placed in a vertical line over the centre of gravity;
and the less distant it is from it, the more delicate will be the
balance. Were it placed exactly in that centre, the beam would not
spontaneously recover the horizontal position when it was once removed
from it. To render its indications more readily commensurable, a slender
rod or needle is fixed to it, at right angles, in the line passing
through its centres of gravity and suspension. The point, or rather
edge, of suspension, is made of perfectly hard steel, and turns upon a
bed of the same. For common uses the arms of a balance can be made
sufficiently equal to give satisfactory results; but, for the more
refined purposes of science, that equality should never be presumed nor
trusted to; and, fortunately, exact weighing is quite independent of
that equality. To weigh a body is to determine how many times the weight
of that body contains another species of known weight, as of grains or
pounds, for example. In order to find it out, let us place the
substance, suppose a piece of gold, in the left hand scale of the
balance; counterpoise it with sand or shot in the other, till the index
needle be truly vertical, or stand in the middle of its scale, proving
the beam to be horizontal. Now remove gently the piece of gold, and
substitute in its place standard multiple weights of any graduation,
English or French, till the needle again resumes the vertical position,
or till its oscillations upon either side of the zero point are equal.
These weights will represent precisely the weight of the gold, since
they are placed in the same circumstances precisely with it, and make
the same equilibrium with the weight laid in the other scale.
This method of weighing is obviously independent of the unequal length
as well as the unequal weight of the arms of the beam. For its
perfection two requisites only are indispensable. The first is that the
points of suspension should be rigorously the same in the two
operations; for the power of a given weight to turn the beam being
unequal, according as we place it at different distances from the centre
of suspension, did that point vary in the two consecutive weighings, we
would require to employ, in the second, a different weight from that of
the piece of gold, in order to form an equilibrium with the sand or shot
originally put in the opposite scale; and as there is nothing to
indicate such inequality in the states of the beam, great errors would
result from it. The best mode of securing against such inequality is to
suspend the cords of the scales from sharp-edged rings, upon knife
edges, at the ends of the beam, both made of steel so hard tempered as
to be incapable of indentation. The second condition is, that the
balance should be very sensible, that is, when in equilibrium and
loaded, it may be disturbed, and its needle may oscillate, by the
smallest weight put into either of the scales. This sensibility depends
solely upon the centre or nail of suspension; and it will be the more
perfect the less friction there is between that _knife-edge_ surface and
the plane which supports it. Both should therefore be as hard and highly
polished as possible; and should not be suffered to press against each
other, except at the time of weighing. Every delicate balance of
moderate size, moreover, should be suspended within a glass case, to
protect it from the agitations of the air, and the corroding influence
of the weather. In some balances a ball is placed upon the index or
needle, (whether that index stand above or below the beam,) which may be
made to approach or recede from the beam by a fine-threaded screw, with
the effect of varying the centre of gravity relatively to the point of
suspension, and thereby increasing, at will, either the sensibility, or
the stability of the balance. The greater the length of the arms, the
less distant the centre of gravity is beneath the centre of suspension,
the better polished its central knife-edge of 30°, the lighter the whole
balance, and the less it is loaded; the greater will be its sensibility.
In all cases the arms must be quite inflexible. A balance made by
Ramsden for the Royal Society, is capable of weighing ten pounds, and
turns with one hundredth of a grain, which is the seven-millionth part
of the weight. In pointing out this balance to me one evening, Dr.
Wollaston told me it was so delicate, that Mr. Pond, then astronomer
royal, when making some observations with it, found its indications
affected by his relative position before it, although it was inclosed in
a glass case. When he stood opposite the right arm, that end of the beam
preponderated, in consequence of its becoming expanded by the radiation
of heat from his body; and when he stood opposite the left arm, he made
this preponderate in its turn. It is probable that Mr. Pond had
previously adjusted the centres of gravity and suspension so near to
each other as to give the balance its maximum sensibility, consistent
with stability. Were these centres made to coincide, the beam, when the
weights are equal, would rest in any position, and the addition of the
smallest weight would overset the balance, and place the beam in a
vertical position, from which it would have no tendency to return. The
sensibility in this case would be the greatest possible; but the other
two requisites of level and stability would be entirely lost. The case
would be even worse if the centre of gravity were higher than the centre
of suspension, as the balance when deranged, if free, would make a
revolution of no less than a semi-circle. A balance may be made by a
fraudulent dealer to weigh falsely though its arms be equal, provided
the suspension be as low as the centre of gravity, for he has only to
toss his tea, for instance, forcibly into one scale to cause 15 ounces
of it, or thereby, to counterpoise a pound weight in the other.
Inspectors of weights, &c. are not _au fait_ to this fruitful source of
fraud among hucksters.
BALSAMS. (_Baumes_, Fr. _Balsame_, Germ.) Are native compounds of
ethereal or essential oils, with resin, and frequently benzoic acid.
Most of them have the consistence of honey; but a few are solid, or
become so by keeping. They flow either spontaneously, or by incisions
made from trees and shrubs in tropical climates. They possess peculiar
powerful smells, aromatic hot tastes, but lose their odoriferous
properties by long exposure to the air. They are insoluble in water;
soluble, to a considerable degree, in ether; and completely in alcohol.
When distilled with water, ethereal oil comes over, and resin remains in
the retort.
1. BALSAMS WITH BENZOIC ACID:--
_Balsam of Peru_ is extracted from the _myroxylon peruiferum_, a tree
which grows in Peru, Mexico, &c.; sometimes by incision, and sometimes
by evaporating the decoction of the bark and branches of the tree. The
former kind is very rare, and is imported in the husk of the cocoa nut,
whence it is called balsam _en coque_. It is brown, transparent only in
thin layers, of the consistence of thick turpentine; an agreeable smell,
an acrid and bitter taste; formed of two matters, the one liquid, the
other granular, and somewhat crystalline. In 100 parts, it contains 12
of benzoic acid, 88 of resin, with traces of a volatile oil.
The second sort, the _black_ balsam of Peru, is much more common than
the preceding, translucent, of the consistence of well-boiled syrup,
very deep red-brown colour, an almost intolerably acrid and bitter
taste, and a stronger smell than the other balsam. Stoltze regards it as
formed of 69 parts of a peculiar oil, 20·7 of a resin, little soluble in
alcohol, of 6·4 of benzoic acid, of 0·6 of extractive matter, and 0·9 of
water.
From its high price, balsam of Peru is often adulterated with copaiba,
oil of turpentine, and olive oil. One thousand parts of good balsam,
should, by its benzoic acid, saturate 75 parts of crystallised carbonate
of soda. It is employed as a perfume for pomatums, tinctures, lozenges,
sealing-wax, and for chocolate and _liqueurs_, instead of vanilla, when
this happens to be very dear.
_Liquid amber_, _Storax or Styrax_, flows from the leaves and trunk of
the _liquid amber styraciflua_, a tree which grows in Virginia,
Louisiana, and Mexico. It is brownish ash-grey, of the consistence of
turpentine, dries up readily, smells agreeably, like benzoin, has a
bitterish, sharp, burning taste; is soluble in 4 parts of alcohol, and
contains only 1·4 per cent. of benzoic acid.
Balsam of Tolu flows from the trunk of the _myroxylon toluiferum_, a
tree which grows in South America; it is, when fresh, of the consistence
of turpentine, is brownish-red, dries into a yellowish or reddish
brittle resinous mass, of a smell like benzoin; is soluble in alcohol
and ether; affords, with water, benzoic acid.
_Chinese varnish_ flows from the bark of the _Augia sinensis_; it is a
greenish yellow turpentine-like substance, smells aromatic, tastes
strong and rather astringent, in thin layers dries soon into a smooth
shining lac, and consists of resin, ethereous oil, and benzoic acid. It
is soluble in alcohol and ether; and has been employed, immemorially, in
China, for lacquering and varnishing surfaces, either alone or coloured.
2. BALSAMS WITHOUT BENZOIC ACID:--
_Copaiva balsam_, balsam of copahu or capivi, is obtained from incisions
made in the trunk of the _Copaifera officinalis_, a tree which grows in
Brazil and Cayenne. It is pale yellow, middling liquid, clear
transparent, has a bitter, sharp, hot taste; a penetrating disagreeable
smell; a specific gravity of from 0·950 to 0·996. It dissolves in
absolute alcohol, partially in spirit of wine, forms with alkalis,
crystalline compounds. It consists of 45·59 ethereous oil, 52·75 of a
yellow brittle resin, and 1·66 of a brown viscid resin. The oil contains
no oxygen, has a composition like oil of turpentine, dissolves
caoutchouc (according to Durand), but becomes oxidised in the air, into
a peculiar species of resin. This balsam is used for making paper
transparent, for certain lacquers, and in medicine.
_Mecca balsam, or opobalsam_, is obtained both by incisions of, and by
boiling, the branches and leaves of the _Balsamodendron Gileadense_, a
shrub which grows in Arabia Felix, Lesser Asia and Egypt. When fresh it
is turbid, whitish, becomes, by degrees, transparent; yellow, thickish,
and eventually solid. It smells peculiar, but agreeable; tastes bitter
and spicy; does not dissolve completely in hot spirit of wine, and
contains 10 per cent. of ethereous oil, of the spec. grav. 0·876.
_Japan lac varnish_ flows from incisions in the trunk of the _Rhus
Vernix_ (_Melanorrhea usitata_) which is cultivated in Japan, and grows
wild in North America. The juice becomes black in the air; when
purified, dissolves in very little oil; and, mixed with colouring
matter, it constitutes the celebrated varnish of the Japanese.
For Benzoin and Turpentine, see these articles in their alphabetical
places.
BANDANNA. A style of calico printing, in which white or brightly
coloured spots are produced upon a red or dark ground. It seems to have
been practised from time immemorial in India, by binding up firmly with
thread, those points of the cloth which were to remain white or yellow,
while the rest of the surface was freely subjected to the dyeing
operations.
[Illustration: 96]
The European imitations have now far surpassed, in the beauty and
precision of the design, the oriental patterns; having called into
action the refined resources of mechanical and chemical science. The
general principles of producing bright figures upon dark grounds, are
explained in the article CALICO-PRINTING; but the peculiarities of the
Bandanna printing may be conveniently introduced here. In Brande’s
Journal for July 1823, I described the Bandanna gallery of Messrs.
Monteith at Glasgow, which, when in full action some years ago, might be
reckoned the most magnificent and profitable printing apartment in the
world. The white spots were produced by a solution of chlorine, made to
percolate down through the Turkey red cotton cloth, in certain points,
defined and circumscribed by the pressure of hollow lead types in
plates, in a hydraulic press. _Fig._ 96., is an elevation of one press;
A, the top or entablature; B B, the cheeks or pillars; C, the upper
block for fastening the upper lead perforated pattern to; D, the lower
block to which the fellow pattern is affixed, and which moves up and
down with the piston of the press; E, the piston or ram; F, the sole or
base; G, the water-trough, for the discharged or spotted calico to fall
into; H, the small cistern, for the aqueous chlorine or liquor-meter,
with glass tubes for indicating the height of liquor inside of the
cistern; _e e_, glass stopcocks, for admitting the liquor into that
cistern from the general reservoir; _f f_, stopcocks for admitting water
to wash out the chlorine; _g g_, the pattern lead-plates, with screws
for setting the patterns parallel to each other; _m m_, projecting
angular pieces at each corner, perforated with a half-inch hole to
receive the four guide-pins rising from the lower plate, which serve to
secure accuracy of adjustment between the two faces of the lead pattern
plates; _h h_, two rollers which seize and pull through the discharged
pieces, and deliver them into the water-trough. To the left of D there
is a stopcock for filling the trough with water; _l_, is the waste tube
for chlorine liquor and water of washing. The contrivance for blowing a
stream of air across the cloth, through the pattern tubes, is not
represented in the figure.
Sixteen engines, similar to the above, each possessing the power of
pressing with several hundred tons, are arranged in one line, in
subdivisions of four; the spaces between each subdivision serving as
passages to allow the workmen to go readily from the front to the back
of the presses. Each occupies twenty-five feet, so that the total length
of the apartment is 100 feet.
To each press is attached a pair of patterns in lead, (or plates as they
are called,) the manner of forming which will be described in the
sequel. One of these plates is fixed to the upper block of the press.
This block is so contrived, that it rests upon a kind of universal
joint, which enables this plate to apply more exactly to the under
fellow-plate. The latter sits on the moveable part of the press,
commonly called the sill. When this is forced up, the two patterns close
on each other very nicely, by means of the guide-pins at the corners,
which are fitted with the utmost care.
The power which impels this great hydrostatic range is placed in a
separate apartment, called the machinery room. This machinery consists
of two press cylinders of a peculiar construction, having solid rams
accurately fitted to them. To each of these cylinders, three little
force-pumps, worked by a steam-engine, are connected.
The piston of the large cylinder is eight inches in diameter, and is
loaded with a top-weight of five tons. This piston can be made to rise
about two feet through a leather-stuffing or collar. The other cylinder
has a piston of only one inch in diameter, which is also loaded with a
top-weight of five tons. It is capable, like the other, of being raised
two feet through its collar.
Supposing the pistons to be at their lowest point, four of the six small
force-pumps are put in action by the steam-engine, two of them to raise
the large piston, and two the little one. In a short time, so much water
is injected into the cylinders, that the loaded pistons have arrived at
their highest points. They are now ready for working the hydrostatic
discharge-presses, the water pressure being conveyed from the one
apartment to the other, under ground, through strong copper tubes, of
small calibre.
Two valves are attached to each press, one opening a communication
between the large driving-cylinder and the cylinder of the press, the
other between the small driving-cylinder and the press. The function of
the first is simply to lift the under-block of the press into contact
with the upper-block; that of the second, is to give the requisite
compression to the cloth. A third valve is attached to the press, for
the purpose of discharging the water from its cylinder, when the press
is to be relaxed, in order to remove or draw through the cloth.
From twelve to fourteen pieces of cloth, previously dyed Turkey-red, are
stretched over each other, as parallel as possible, by a particular
machine. These parallel layers are then rolled round a wooden cylinder,
called by the workmen, a drum. This cylinder is now placed in its proper
situation at the back of the press. A portion of the fourteen layers of
cloth, equal to the area of the plates, is next drawn through between
them, by hooks attached to the two corners of the webs. On opening the
valve connected with the eight-inch driving-cylinder, the water enters
the cylinder of the press, and instantly lifts its lower block, so as to
apply the under plate with its cloth, close to the upper one. This valve
is then shut, and the other is opened. The pressure of five tons in the
one inch prime-cylinder, is now brought to bear on the piston of the
press, which is eight inches in diameter. The effective force here will,
therefore, be 5 tons × 8² = 320 tons; the areas of cylinders being to
each other, as the squares of their respective diameters. The cloth is
thus condensed between the leaden pattern-plates, with a pressure of 320
tons, in a couple of seconds;--a splendid example of automatic art.
The next step, is to admit the blanching or discharging liquor, (aqueous
chlorine, obtained by adding sulphuric acid to solution of chloride of
lime,) to the cloth. This liquor is contained in a large cistern, in an
adjoining house, from which it is run at pleasure into small lead
cisterns H attached to the presses; which cisterns have graduated index
tubes, for regulating the quantity of liquor according to the pattern of
discharge. The stopcocks on the pipes and cisterns containing this
liquor, are all made of glass.
From the measure-cistern H, the liquor is allowed to flow into the
hollows in the upper lead-plate, whence it descends on the cloth, and
percolates through it, extracting in its passage the Turkey-red dye. The
liquor is finally conveyed into the waste pipe, from a groove in the
under block. As soon as the chlorine liquor has passed through, water is
admitted in a similar manner, to wash away the chlorine; otherwise, upon
relaxing the pressure, the outline of the figure discharged would become
ragged. The passage of the discharge liquor, as well as of the water
through the cloth, is occasionally aided by a pneumatic apparatus, or
blowing machine; consisting of a large gasometer, from which air
subjected to a moderate pressure, may be allowed to issue, and act in
the direction of the liquid, upon the folds of the cloth. By an
occasional twist of the air stopcock, the workman also can ensure the
equal distribution of the discharging liquor, over the whole excavations
in the upper plate. When the demand for goods is very brisk, the air
apparatus is much employed, as it enables the workman to double his
product.
The time requisite for completing the discharging process in the first
press is sufficient to enable the other three workmen to put the
remaining fifteen presses in play. The discharger proceeds now from
press to press, admits the liquor, the air, and the water; and is
followed at a proper interval by the assistants, who relax the press,
move forwards another square of the cloth, and then restore the
pressure. Whenever the sixteenth press has been liquored, &c., it is
time to open the first press. In this routine, about ten minutes are
employed; that is 224 handkerchiefs (16 × 14) are discharged every ten
minutes. The whole cloth is drawn successively forward, to be
successively treated in the above method.
When the cloth escapes from the press, it is passed between the two
rollers in front; from which it falls into a trough of water placed
below. It is finally carried off to the washing and bleaching
department, where the lustre of both the white and the red is
considerably brightened.
By the above arrangement of presses, 1600 pieces, consisting of 12 yards
each = 19,200 yards, are converted into Bandannas in the space of ten
hours, by the labour of four workmen.
The patterns, or plates, which are put into the presses to determine the
white figures on the cloth, are made of lead in the following way. A
trellis frame of cast-iron, one inch thick, with turned-up edges,
forming a trough rather larger than the intended lead pattern, is used
as the solid ground-work. Into this trough, a lead plate about one half
inch thick, is firmly fixed by screw nails passing up from below. To the
edges of this lead plate, the borders of the piece of sheet-lead are
soldered, which covers the whole outer surface of the iron frame. Thus a
strong trough is formed, one inch deep. The upright border gives at once
great strength to the plate, and serves to confine the liquor. A thin
sheet of lead is now laid on the thick lead-plate, in the manner of a
veneer on toilette-tables, and is soldered to it round the edges. Both
sheets must be made very smooth beforehand, by hammering them on a
smooth stone table, and then finishing with a plane: the surface of the
thin sheet (now attached), is to be covered with drawing paper, pasted
on, and upon this the pattern is drawn. It is now ready for the cutter.
The first thing which he does, is to fix down with brass pins all the
parts of the pattern which are to be left solid. He now proceeds with
the little tools generally used by block-cutters, which are fitted to
the different curvatures of the pattern, and he cuts perpendicularly
quite through the thin sheet. The pieces thus detached are easily lifted
out; and thus the channels are formed which design the white figures on
the red cloth. At the bottom of the channels, a sufficient number of
small perforations are made through the thicker sheet of lead, so that
the discharging liquor may have free ingress and egress. Thus, one plate
is finished; from which, an impression is to be taken by means of
printers’ ink, on the paper pasted upon another plate. The impression is
taken in the hydrostatic press. Each pair of plates constitutes a set,
which may be put into the presses, and removed at pleasure.
BARBERRY. The root of this plant contains a yellow colouring matter,
which is soluble in water and alcohol, and is rendered brown by alkalis.
The solution is employed in the manufacture of Morocco leather.
BARILLA. A crude soda, procured by the incineration of the _salsola
soda_, a plant cultivated for this purpose in Spain, Sicily, Sardinia,
&c. Good barilla usually contains, according to my analysis, 20 per
cent. of real alkali, associated with muriates and sulphates, chiefly of
soda, some lime, and alumina, with very little sulphur. Caustic lyes
made from it, are used in the finishing process of the hard soap
manufacture. 125,068 cwts. were imported in 1835, of which only 5,807
were exported. The duty is 2_s._ per cwt. Of the above quantity, 64,174
came from Spain and the Balearic islands, 39,943 from the Canaries, and
20,432 from Italy and the Italian islands.
BARIUM, the metallic basis of Baryta.
BARK OF OAK, for tanning. Unfortunately, the Tables of Revenue published
by the Board of Trade, mix up this bark and the dyeing barks together,
and give the sum of the whole for 1835, at 826,566 cwts., of which only
2,264 were re-exported. The duty is 1_d._ per cwt. from British
possessions, and 8_d._ from other parts.
BARLEY (_Orge_, Fr. _Gerste_, Germ.) English barley is that with
two-rowed ears, or the _hordeum vulgare distichon_ of the botanists; the
Scotch beer or bigg, is the _hordeum vulgare hexastichon_. The latter
has two rows of ears, but 3 corns come from the same point, so that it
seems to be six-eared. The grains of bigg are smaller than those of
barley, and the husks thinner. The specific gravity of English barley
varies from 1·25 to 1·33; of bigg from 1·227 to 1·265; the weight of the
husk of barley is 1/6, that of bigg 2/9. 1000 parts of barley flour
contain, according to Einhof, 720 of starch, 56 sugar, 50 mucilage, 36·6
gluten, 12·3 vegetable albumen, 100 water, 2·5 phosphate of lime, 68
fibrous or ligneous matter. Sp. gravity of barley, is 1·235 by my
trials.
BARM. The yeasty top of fermenting beer. See BEER, DISTILLATION,
FERMENTATION.
BARYTA or BARYTES, one of the simple earths. It may be obtained most
easily by dissolving the native carbonate of barytes (Witherite) in
nitric acid, evaporating the neutral nitrate till crystals be formed,
draining and then calcining these in a covered platina crucible, at a
bright red heat. A less pure baryta may be obtained by igniting strongly
a mixture of the carbonate and charcoal, both in fine powder and
moistened. It is a grayish white earthy looking substance, fusible only
at the jet of the oxy-hydrogen blowpipe, has a sharp caustic taste,
corrodes the tongue and all animal matter, is poisonous even in small
quantities, has a very powerful alkaline reaction; a specific gravity of
4·0; becomes hot, and slakes violently when sprinkled with water,
falling into a fine white powder, called the hydrate of baryta, which
contains 10-1/2 per cent. of water, and dissolves in 10 parts of boiling
water. This solution lets fall abundant columnar crystals of hydrate of
baryta as it cools; but it still retains one twentieth its weight of
baryta, and is called baryta water. The above crystals contain 61 per
cent. of water, of which, by drying, they lose 50 parts. This hydrate
may be fused at a red heat without losing any more water. Of all the
bases, baryta has the strongest affinity for sulphuric acid, and is
hence employed either in the state of the above water, or in that of one
of its neutral salts, as the nitrate or muriate, to detect the presence,
and determine the quantity of that acid present in any soluble compound.
Its prime equivalent, according to Berzelius, is 956,880, oxygen being
100; or 76,676, hydrogen being 1,000. Native sulphate of baryta, or
heavy spar, is fraudulently used to adulterate white lead by the English
dealers to a shameful extent.
BASSORINE. A constituent part of a species of gum which comes from
Bassora, as also of gum tragacanth, and of some gum resins. It is
semi-transparent, difficult to pulverise, swells considerably in cold or
boiling water, and forms a thick mucilage without dissolving. Treated
with ten times its weight of nitric acid, it affords nearly 23 per cent.
of its weight of mucic acid, being much more than is obtainable from gum
arabic or cherry-tree gum. Bassorine is very soluble in water slightly
acidulated with nitric or muriatic acid. This principle is procured by
soaking gum Bassora in a great quantity of cold water, and in removing,
by a filter, all the soluble parts.
BATHS. (_Bains_, Fr. _Baden_, Germ.) Warm baths have lately come into
very general use, and they are justly considered as indispensably
necessary in all modern houses of any magnitude, as also in club-houses,
hotels, and hospitals. But the mode of constructing these baths, and of
obtaining the necessary supplies of hot and cold water, does not appear
to have undergone an improvement equal to the extension of their
employment.
The several points in regard to warm baths, are,
1. The materials of which they are constructed.
2. Their situation.
3. The supply of cold water.
4. The supply of hot water.
5. Minor comforts and conveniences.
1. As to the materials of which they are constructed.--Of these the best
are slabs of polished marble, properly bedded with good water-tight
cement, in a seasoned wooden case, and neatly and carefully united at
their respective edges. These, when originally well constructed, form a
durable, pleasant, and agreeable-looking bath; but the expense is often
objectionable, and, in upper chambers, the weight may prove
inconvenient. If of white or veined marble, they are also apt to get
yellow or discoloured by frequent use, and cannot easily be cleansed; so
that large Dutch tiles, as they are called, or square pieces of white
earthenware, are sometimes substituted; which, however, are difficultly
kept water-tight; so that, upon the whole, marble is preferable.
Where there are reasons for excluding marble, copper or tinned iron
plate is the usual material resorted to. The former is most expensive in
the outfit, but far more durable than the latter, which is, moreover,
liable to leakage at the joints, unless most carefully made. Either the
one or the other should be well covered outside and inside, with several
coats of paint, which may then be marbled, or otherwise ornamented.
Wooden tubs, square or oblong, and oval, are sometimes used for warm
baths; and are cheap and convenient, but neither elegant nor cleanly.
The wood always contracts a mouldy smell; and the difficulty and
nuisance of keeping them water-tight, and preventing shrinkage, are such
as to exclude them from all except extemporaneous application.
2. As to the situation of the bath, or the part of the house in which it
is to be placed.--In hotels, and club-houses, this is a question easily
determined: several baths are usually here required, and each should
have annexed to it, a properly warmed dressing-room. Whether they are up
stairs or down stairs, is a question of convenience, but the basement
story, in which they are sometimes placed, should always be avoided;
there is a coldness and dampness belonging to it, in almost all
weathers, which is neither agreeable nor salubrious.
In hospitals, there should be at least two or three baths on each side
of the house, (the men’s and women’s), and the supply of hot water
should be ready at a moment’s notice. The rooms in which the baths are
placed should be light and comparatively large and airy; and such
conveniences for getting into and out of the bath should be adopted, as
the sick are well known to require. The dimensions of these baths should
also be larger than usual.
In private houses, the fittest places for warm baths are dressing-rooms
annexed to the principal bed-rooms; or, where such convenience cannot be
obtained, a separate bath-room, connected with the dressing-room, and
always upon the bed-room floor. All newly-built houses should be
properly arranged for this purpose, and due attention should be paid to
the warming of the bath-room, which ought also to be properly
ventilated. A temperature of 70° may be easily kept up in it, and
sufficient ventilation is absolutely requisite, to prevent the
deposition of moisture upon the walls and furniture.
The objection which formerly prevailed, in respect to the difficulty of
obtaining adequate supplies of water, in the upper rooms, has been
entirely obviated, by having cisterns at or near the top of the house;
and we would just hint that these should be so contrived, as to be
placed out of the reach of frost; a provision of the utmost importance
in every point of view, and very easily effected in a newly-built house,
though it unfortunately happens, that architects usually regard these
matters as trifles, and treat them with neglect, as indeed they do the
warming and ventilation of buildings generally.
3. The supply of water of proper quality and quantity, is a very
important point, as connected with the present subject. The water should
be soft, clean, and pure; and as free as possible from all substances
mechanically suspended in it. In many cases, it answers to dig a well
for the exclusive supply of a large house with water. In most parts of
London this may effectually be accomplished, at a comparatively moderate
expense; and, if the well be deep enough, the water will be abundant,
soft, and pellucid. The labour of forcing it by a pump to the top of the
house, is the only drawback; this, however, is very easily done by a
horse-engine, or there are people enough about town, glad to undertake
it at a shilling a day. I am led to these remarks by observing the
filthy state of the water usually supplied, at very extravagant rates,
by the water companies. It often partakes more of the appearance of
pea-soup than of the pure element; fills our cisterns and pipes with mud
and dirt, and, even when cleared by subsidence, is extremely
unpalatable. It deposits its nastiness in the pipes connected with warm
baths, and throws down a slippery deposit upon the bottom of the vessel
itself to such an extent, as often to preclude its being used, at least
as a luxury, which a clear and clean bath really is. This inconvenience
may, in some measure, be avoided, by suffering the water to throw down
its extraneous matters upon the bottom of the cistern, and drawing our
supplies from pipes a little above it; there will, however, always be
more or less deposit in the pipes themselves; and every time the water
runs into the cistern, the grouts are stirred up, and diffused through
its mass: this, from some cause or other, has lately become an
intolerable nuisance; and he who reflects upon the miscellaneous
contents of Thames water, will not have his appetite sharpened by a
draught of the Grand Junction beverage, nor feel reanimated and
refreshed by bathing in a compound so heterogeneous and unsavoury.
4. and 5. In public bathing establishments, where numerous and constant
baths are required, the simplest and most effective means of obtaining
hot water for their supply consists in drawing it directly into the
baths from a large boiler, placed somewhere above their level. This
boiler should be supplied with proper feeding-pipes and gauges; and,
above all things, its dimensions should be ample; it should be of
wrought iron or copper, except where sea water is used, in which case
the latter metal is sometimes objectionable. The hot water should enter
the bath by a pipe at least an inch and a half in diameter; and the cold
water by one of the same dimension, or somewhat larger, so that the bath
may not be long in filling. The relative proportions of the hot and cold
water are, of course, to be adjusted by a thermometer, and every bath
should have a two-inch waste-pipe, opening about two inches from the top
of the bath, and suffering the excess of water freely to run off; so
that when a person is immersed in the bath, or when the supplies of
water are accidentally left open, there may be no danger of an overflow.
Where there is a laundry in the upper story of the house, or other
convenient place for erecting a copper and its appurtenances, a plan
similar to the above may often be conveniently adopted in private
houses, for the supply of a bath upon the principal bed-room floor. An
attempt is sometimes made to place boilers behind the fires of
dressing-rooms, or otherwise to erect them in the room itself, for the
purpose of supplying warm water; but this plan is always objectionable,
from the complexity of the means by which the supply of water is
furnished to the boiler, and often dangerous from the flues becoming
choaked with soot, and taking fire. Steam is also apt, in such cases, to
escape in quantities into the room; so that it becomes necessary to
search for other methods of heating the bath; one or two of the least
objectionable of which I shall describe.
1. A contrivance of some ingenuity consists in suffering the water for
the supply of the bath to flow from a cistern above it, through a leaden
pipe of about one inch diameter, which is conducted into the kitchen or
other convenient place where a large boiler for the supply of hot water
is required. The bath-pipe is immersed in this boiler, in which it makes
many convolutions, and, again emerging, ascends to the bath. The
operation is simply this:--the cold water passing through the
convolutions of that part of the pipe which is immersed in the boiling
water, receives there sufficient heat for the purpose required, and is
delivered in that state by the ascending pipe into the bath, which is
also supplied with cold water and waste-pipes as usual. The pipe may be
of lead, as far as the descending and ascending parts are concerned, but
the portion forming the worm, or convolutions immersed in the boiler
should be copper, in order that the water within it may receive heat
without impediment.
This plan is economical only where a large boiler is constantly kept at
work in the lower part of the house; otherwise, the trouble and expense
of heating such a boiler, for the mere purpose of the bath, render it
unavailable. The worm-pipe is also apt to become furred, upon the
outside, by the deposition of the earthy impurities of the water in
which it is immersed; it then becomes a bad conductor of heat, is
cleansed with difficulty, and the plan is rendered ineffective. This
system, however, has been adopted, in some particular cases, with
satisfaction.
2. A much more simple, economical, and independent mode of heating a
warm bath, by a fire placed at a distance from it, is the following,
which is found to answer perfectly in private houses, as well as upon a
more extended scale in large establishments. It is certainly open to
some objections, but these are overbalanced by its advantages. A
waggon-shaped boiler, holding about six gallons of water, is properly
placed over a small furnace, in any convenient and safe part of the
house, as the kitchen, scullery, servants’ hall, or wash-house. The bath
itself, of the usual dimensions and construction, is placed where it is
wanted, with a due supply of cold water from above. Two pipes issue from
within an inch of the bottom of the bath at its opposite extremities;
one at the head of the bath, about one inch, and the other at the foot,
an inch and one eighth in diameter. These tubes descend to the boiler,
the smaller one entering it at the bottom, and the larger one issuing
from its top.
Under these circumstances, supposing the pipes and boiler every where
perfectly tight, when the bath is filled, the water will descend into
and expel the air from the boiler, and completely fill it. Now, upon
making a gentle fire under the boiler, an ascending current of warm
water will necessarily pass upwards through the larger pipe which issues
from its top, and cold water will descend by the pipe which enters at
the bottom; and thus, by the establishment of currents, the whole mass
of water in the bath will become heated to the desired point; or, if
above it, the temperature may easily be lowered by the admixture of cold
water.
The advantages of this form of bath are numerous. The shorter the pipes
of communication the better, but they may extend forty or fifty feet
without any inconvenience beyond that of expense; so that there is no
obstacle to the bath being near the bed-room while the boiler is on the
basement story. There is but little time required for heating the bath;
the water in which may, if requisite, be raised to about 100° in about
half an hour from the time of lighting the fire. The consumption of fuel
is also trifling.
The following are the chief disadvantages attendant upon this plan, and
the means of obviating them:--
It is necessary, when the water has acquired its proper temperature, to
withdraw the fire from the boiler, or not to use the bath immediately,
as it may go on acquiring some heat from the boiler, so that we may
become inconveniently hot in the bath. When, therefore, this bath is
used, we may proceed as follows:--heat the water in it an hour before it
is wanted, to about 100°, and then extinguish the fire. The water will
retain its temperature, or nearly so, for three or four hours,
especially if the bath be shut up with a cover; so that when about to
use it, cold water may be admitted till the temperature is lowered to
the required point, and thus all the above inconveniences are avoided.
Another disadvantage of this bath arises from too fierce a fire being
made under the boiler, so as to occasion the water to boil within it, a
circumstance which ought always to be carefully avoided. In that case,
the steam rising in the upper part of the boiler, and into the top pipe,
condenses there, and occasions violent concussions, the noise of which
often alarms the whole house, and leads to apprehensions of explosion,
which, however, is very unlikely to occur; but the concussions thus
produced injure the pipes, and may render them leaky: so that in regard
to these, and all other baths, &c., we may remark, that the pipes should
pass up and down in such parts of the house as will not be injured if
some leakage takes place; and under the bath itself should be a
sufficiently large leaden tray with a waste-pipe, to receive and carry
off any accidental drippings, which might injure the ceilings of the
rooms below. In all newly-built houses, two or three flues should be
left in proper places for the passage of ascending and descending
water-pipes; and these flues should in some way receive at their lower
part a little warm air in winter, to prevent the pipes freezing: the
same attention should also be paid to the situation of the cisterns of
water in houses, which should be kept within the house, and always
supplied with a very ample waste-pipe, to prevent the danger of
overflow. Cisterns thus properly placed, and carefully constructed,
should be supplied from the water-mains by pipes kept under ground, till
they enter the house, and not carried across the area, or immediately
under the pavement, where they are liable to freeze.
3. Baths are sometimes heated by steam, which has several advantages: it
may either be condensed directly into the water of the bath, or, if the
bath be of copper or tinned iron, it may be conducted into a casing upon
its outside, usually called a jacket; in the latter case there must be a
proper vent for the condensed water, and for the escape of air and waste
steam. Steam is also sometimes passed through a serpentine pipe, placed
at the bottom of the bath. But none of these methods are to be
recommended for adoption in private houses, and are only advisable in
hospitals, or establishments where steam boilers are worked for other
purposes than the mere heating of baths.
Many copper and tin baths have been lately constructed in London, with a
little furnace attached to one end, and surrounded with a case or
jacket, into which the water flows and circulates backwards and forwards
till the whole mass in the bath gets heated to the due degree. One of
the best of these is that constructed by Mr. Benham, of Wigmore Street.
The bath must be placed near the fire-grate, and the smoke-pipe of the
attached furnace be conducted up the chimney a certain way to secure a
sufficient draught to maintain combustion. The above bath, well managed,
heats the water from 50° to 98° in about 20 or 25 minutes, as I have
experimentally proved. When the proper temperature is attained, the fire
must of course be extinguished.
BDELLIUM. A gum resin, produced by an unknown plant which grows in
Persia and Arabia. It comes to us in yellowish or reddish pieces, smells
faintly, like myrrh, and consists of 59 resin, 9·2 gum, 30·6 bassorine,
and 1·2 ethereous oil.
BEER. (_Bière_, Fr. _Bier_, Germ.) The fermented infusion of malted
barley, flavoured with hops, constitutes the best species of beer; but
there are many beverages of inferior quality to which this name is
given, such as spruce beer, ginger beer, molasses beer, &c.; all of
which consist of a saccharine liquor, partially advanced into the vinous
fermentation, and flavoured with peculiar substances.
The ancients were acquainted with beer, and the Romans gave it the
appropriate name of _Cerevisia_ (quasi _Ceresia_), as being the product
of corn, the gift of Ceres. The most celebrated liquor of this kind in
the old time, was the _Pelusian_ potation, so called from the town where
it was prepared at the mouth of the Nile. Aristotle speaks of the
intoxication caused by beer; and Theophrastus very justly denominated it
the _wine of barley_. We may, indeed, infer from the notices found in
historians, that drinks analogous to our beer were in use among the
ancient Gauls, Germans, and in fact almost every people of our temperate
zone; and they are still the universal beverage in every land where the
vine is not an object of rustic husbandry.
The manufacture of beer, or the art of brewing, may be conveniently
considered under five heads:--
1. An examination of the natural productions which enter into its
composition; or of barley and hops.
2. The changes which barley must undergo to fit it for making beer; or
the processes of malting and mashing.
3. The formation of a proper wort from the mashed malt and hops.
4. The fermentation of that wort; and
5. The fining, ripening, and preservation of the beer.
I. _Of the materials._
1. Barley, wheat, maize, and several other kinds of corn are capable of
undergoing those fermentative changes, by which beer may be made; but
the first substance is by far the fittest. There are two species of
barley, the _hordeum vulgare_ or common barley, having two seeds
arranged in a row on its spikes; and the _hordeum hexastichon_, in which
three seeds spring from one point, so that its double row has apparently
six seeds. The former is the proper barley, and is much the larger sized
grain; the latter is little known in England, but is much cultivated in
Scotland under the name of _bear_ or _big_; being a hardy plant adapted
to a colder country. The finer the climate in which barley grows the
denser and larger its seed, and the thinner its husk; thus the Norfolk
and Suffolk barley is distinguished in these respects from that of
Aberdeenshire. Big is a less compact grain than barley; the weight of a
Winchester bushel (2150·42 cubic inches) of the former is only about 47
libs, while that of a bushel of the latter is nearly 51 libs. Their
constituents, however, bear much the same proportion to each other.
The quality of barley is proved not only by its density when dry, but by
the increase of volume which it acquires when steeped in water. Thus,
100 measures of average English barley thereby swell into 124.
100 -- of -- Scotch ditto, 121.
100 -- of -- -- bigg or bear, 118.
Nay, 100 of very fine Suffolk barley have swollen into 183.
While 100 of an inferior Scotch bigg became no more than 109.
This circumstance indicates so nearly the probable yield of malt, that
it is carefully attended to by the officers of excise, who gauge the
steep cistern, and levy their duty in conformity with the largest
volume, 100 pounds of good barley become almost one half heavier by the
absorption of moisture; and weigh upon an average 147 pounds; the best
of course taking up most water.
By chemical analysis barley flour seems to consist of 67·18 parts of
hordeine, or starch and gluten intimately combined, 7·29 of vegetable
fibre, 1·15 of coagulated albumen, 3·52 parts of gluten, 5·21 of sugar,
4·62 of gum, 0·24 of phosphate of lime, and 9·37 of water. The loss
amounted to 1·42. To these principles should be added a peculiar
volatile oil of a concrete nature, which is obtained during the process
of distilling fermented malt wash. (See WHISKEY.) It may also be
extracted from barley flour, by the solvent action of alcohol; and never
amounts to more than a few parts in the thousand. The husk also contains
some of that fetid oil. Proust thought that he had discovered in barley
a peculiar principle, to which he gave the name of _hordeine_, and which
he separated from starch by the action of both cold and boiling water.
He found that by treating barley meal successively with water, he
obtained from 89 to 90 parts of a farinaceous substance, composed of
from 32 to 33 of starch, and from 57 to 58 of _hordeine_. Einhof
obtained from barley seeds, 70·05 of flour, 18·75 of husks or bran, and
11·20 of water.
According to Proust hordeine is a yellowish powder, not unlike fine
saw-dust. It contains no azote, for it affords no ammonia by
distillation, and is therefore very dissimilar to gluten. In the
germination of barley, which constitutes the process of malting, the
proportion of hordeine is greatly diminished by its conversion into
sugar and starch. Other chemists suppose that the _hordeine_ of Proust
is merely a mixture of the bran of the barley with starch and gluten. It
is obvious that the subject stands in need of new chemical researches.
In barley the husk constitutes from one fourth to one fifth of the whole
weight; in oats it constitutes one third; and in wheat, one tenth. From
the analysis of barley flour recently made, it appears to consist in
1000 parts: of water, 100; albumine, 22·3; sugar, 56; gum or mucilage,
50; gluten, 37·6; starch, 720; phosphate of lime, 2·5.
2. The hop, _humulus lupulus_, the female flowers of the plant. Ives
first directed attention to a yellow pulverulent substance which invests
the scales of the catkins, amounting to about one eighth of their
weight; and referred to it the valuable properties which hops impart to
beer. We may obtain this substance by drying the hops at a temperature
of 86° F., introducing them into a coarse canvass bag, and shaking it so
that the yellow powder shall pass through the pores of the canvass. This
powder bears some resemblance to lycopodium. Of the 13 parts in 100 of
this powder, 4 parts are foreign matters, derived from the scales of the
cones; leaving 9 parts of a peculiar granular substance. When distilled
with water, this substance affords two per cent. of its weight (2/10 for
100 times the weight of hops) of a volatile colourless oil, to which the
plant owes its peculiar aroma. This oil dissolves in water in
considerable quantity. It appears to contain sulphur (for it blackens
solutions of silver), and also acetate of ammonia. No less than 65 per
cent. of the yellow dust is soluble in alcohol. This solution, treated
with water and distilled, leaves a resin, which amounts to 52·5 per
cent. It has no bitter taste, and is soluble in alcohol and ether. The
watery solution from which the resin was separated contains the bitter
substance which has been called _lupuline_ by Payen and Chevallier,
mixed with a little tannin and malic acid. To obtain this in a state of
purity, the free acid must be saturated with lime, the solution
evaporated to dryness, and the residuum must be treated with ether,
which removes a little resin; after which the _lupuline_ is dissolved
out by alcohol, which leaves the malate of lime. On evaporating away the
alcohol, the lupuline remains, weighing from 8·3 to 12·5 per cent. It is
sometimes white, or slightly yellowish, and opaque, sometimes orange
yellow, and transparent. At ordinary temperatures it is inodorous, but
when heated strongly it emits the smell of hops. It possesses the
characteristic taste and bitterness of the hop. Water dissolves it only
in the proportion of 5 per cent., but it thereby acquires a pale yellow
colour. Lupuline is neither acid nor alkaline; it is acted upon neither
by the dilute acids nor alkalies, nor by the solutions of the metallic
salts: it is quite soluble in alcohol, but hardly in ether. It contains
apparently no azote, for it affords no ammonia by destructive
distillation; but only an empyreumatic oil.
The yellow dust of hops contains, moreover, traces of a fatty matter,
gum, a small quantity of an azotised substance, and several saline
combinations in minute quantity. Boiling water dissolves from 19 to 31
per cent., of the contents of the dust, of which a large proportion is
resin. Ives thought that the scales of the catkins of hops, when freed
from the yellow powder, contained no principles analogous to it; but
Payen and Chevallier have proved the contrary. The cones of hop give up
to boiling alcohol 36 per cent. of soluble matter; while the same cones,
stripped of their yellow powder, yield only 26 per cent.; and further,
these chemists found the same principles in the different parts of the
hop, but in different proportions.
The packing of the hop catkins or cones is one of the most important
operations towards the preservation of this plant; and is probably the
cause of the enormous difference in value between the English and French
hops after a few years’ keeping. The former, at the end of six years,
possess still great value, and may be sold as an article only two or
three years old; while the latter have lost the greater part of their
value in three years, and are no more saleable at the end of four. In
France, it is packed merely by tramping it with the feet in sacks. Under
this slight pressure, large interstitial spaces are left amid the mass
of the hops, through which the air freely circulates, carrying off the
essential oil, and oxygenating some of the other proximate principles,
so as to render them inert. By the English method, on the contrary, the
hops, after being well rammed into strong sacks hung in frames, are next
subjected to the action of a hydraulic press. The valuable yellow powder
thus inclosed on every side by innumerable compact scales, is completely
screened from the contact of the atmosphere, and from all its
vicissitudes of humidity. Its essential oil, in particular the basis of
its flavour, is preserved without decay.
According to the experiments of Chevallier and Payen upon the hops of
England, Flanders, the Netherlands, and the department of the Vosges,
those of the county of Kent afforded the largest cones, and were most
productive in useful secreted and soluble matters. Next to them were the
hops of Alost.
The best hops have a golden yellow colour, large cones, an agreeable
aroma; when rubbed between the hands, they leave yellow traces,
powerfully odoriferous, without any broken portions of the plant, such
as leaves, stems, and scaly fragments. When alcohol is digested on good
hops, from 9 to 12 per cent. of soluble yellow matter may be obtained by
evaporating it to dryness. This is a good test of their quality.
The best-flavoured and palest hops are packed in sacks of fine canvass,
which are called pockets, and weigh about 1-1/2 cwt. each. These are
bought by the ale brewer. The stronger-flavoured and darker-coloured
hops are packed in bags of a very coarse texture like door-mats, called
hop bags: these contain generally about 3 cwt., and are sold to the
porter and beer brewers. After the end of a year or two, hops are
reckoned to have lost much of their marketable value, and are then sold
to the second-rate porter brewers, under the name of old hops. The
finest hops are grown in the neighbourhood of Canterbury; but those of
Worcester have an agreeable mildness of flavour, greatly admired by many
ale drinkers. When the bitter and aromatic principles disappear, the
hops are no better than so much chaff; therefore, an accurate chemical
criterion of their principles would be a great benefit to the brewer.
II. _Malting._--This process consists of three successive operations;
the steeping; the couching, sweating, and flooring; and the kiln-drying.
The _steeping_ is performed in large cisterns made of wood or stone,
which being filled with clear water up to a certain height, a quantity
of barley is shot into them, and well stirred about with rakes. The good
grain is heavy, and subsides; the lighter grains, which float on the
surface, are damaged, and should be skimmed off; for they would injure
the quality of the malt, and the flavour of the beer made with it. They
seldom amount to more than two per cent. More barley is successively
emptied into the steep cistern, till the water stands only a few inches,
about five, above its surface; when this is levelled very carefully, and
every light seed is removed. The steep lasts from forty to sixty hours,
according to circumstances; new barley requiring a longer period than
old, and bigg requiring much less time than barley.
During this steep, some carbonic acid is evolved from the grains, and
combines with the water, which, at the same time, acquires a yellowish
tinge, and a strawy smell, from dissolving some of the extractive matter
of the barley husks. The grain imbibes about one half its weight of
water, and increases in size by about one-fifth. By losing this extract,
the husk becomes about one seventieth lighter in weight, and paler in
colour.
The duration of the steep depends, in some measure, upon the temperature
of the air, and is shorter in summer than in winter. In general from 40
to 48 hours will be found sufficient for sound dry grain. Steeping has
for its object to expand the farina of the barley with humidity, and
thus prepare the seed for germination, in the same way as the moisture
of the earth prepares for the growth of the radicle and plumula in seed
sown in it. Too long continuance in the steep is injurious; because it
prevents the germination at the proper time, and thereby exhausts a
portion of the vegetative power: it causes also an abstraction of
saccharine matter by the water. The maceration is known to be complete
when the grain may be easily transfixed with a needle, and is swollen to
its full size. The following is reckoned a good test:--If a barley-corn,
when pressed between the thumb and fingers, continues entire in its
husk, it is not sufficiently steeped; but if it sheds its flour upon the
fingers, it is ready. When the substance exudes in the form of a milky
juice, the steep has been too long continued, and the barley is spoiled
for germination.
In warm weather it sometimes happens that the water becomes acescent
before the grain is thoroughly swelled. This accident, which is manifest
to the taste and smell, must be immediately obviated by drawing off the
foul water through the tap at the bottom of the cistern, and replacing
it with fresh cold water. It does no harm to renew it two or three times
at one steep.
The _couch_.--The water being drawn off, and occasionally a fresh
quantity passed through, to wash away any slimy matter which may have
been generated in warm weather, the barley is now laid upon the couch
floor of stone flags, in square heaps from 12 to 16 inches high, and
left in that position for 24 hours. At this period, the bulk of the
grain being the greatest, it may be gauged by the revenue officers if
they think fit. The moisture now leaves the surface of the barley so
completely, that it imparts no dampness to the hand. By degrees,
however, it becomes warm; the temperature rising 10° above the
atmosphere, while an agreeable fruity smell is evolved. At this time, if
the hand be thrust into the heap, it not only feels warm, but it gets
bedewed with moisture. At this sweating stage, the germination begins;
the fibrils of the radicle first sprout forth from the tip of every
grain, and a white elevation appears, that soon separates into three or
more radicles, which grow rapidly larger. About a day after this
appearance, the plumula peeps forth at the same point, proceeding thence
beneath the husk to the other end of the seed, in the form of a green
leaflet.
The greatest heat of the couch is usually about 96 hours after the
barley has been taken out of the steep. In consequence, the radicles
tend to increase in length with very great rapidity, and must be checked
by artificial means, which constitute the chief art of the maltster. He
now begins to spread the barley thinner on the floor, and turns it over
several times in the course of a day, bringing the portions of the
interior into the exterior surface. The depth, which was originally 15
or 16 inches, is lowered a little at every turning over, till it be
brought eventually down to three or four inches. Two turnings a day are
generally required. At this period of spreading or flooring, the
temperature in England is about 62°, and in Scotland 5 or 6 degrees
lower.
About a day after the radicles appear, the rudiments of the stem, or of
the plumula, sprout forth, called by the English maltsters the
_acrospire_. It issues from the same end of the seed as the radicle, but
turns round, and proceeds within the husk towards the other end, and
would there come forth as a green leaf, were its progress not arrested.
The malting, however, is complete before the acrospire becomes a leaf.
The barley couch absorbs oxygen and emits carbonic acid, just as animals
do in breathing, but to a very limited extent; for the grain loses only
three per cent. of its weight upon the malt floor, and a part of this
loss is due to waste particles. As the acrospire creeps along the
surface of the seed, the farina within undergoes a remarkable
alteration. The gluten and mucilage disappear, in a great measure, the
colour becomes whiter, and the substance becomes so friable that it
crumbles into meal between the fingers. This is the great purpose of
malting, and it is known to be accomplished when the plumula or
acrospire has approached the end of the seed. Now the further growth
must be completely stopped. Fourteen days may be reckoned the usual
duration of the germinating stage of the malting operations in England;
but in Scotland, where the temperature of the couch is lower, eighteen
days or even twenty-one, are sometimes required. The shorter the period
within the above limits, the more advantageous is the process to the
maltster, as he can turn over his capital the sooner, and his malt is
also somewhat the better. Bigg is more rapid in its germination than
barley, and requires to be still more carefully watched. In dry weather
it is sometimes necessary to water the barley upon the couch.
Occasionally the odour disengaged from the couch is offensive,
resembling that of rotten apples. This is a bad prognostic, indicating
either that the barley was of bad quality, or that the workmen, through
careless shovelling, have crushed a number of the grains in turning them
over. Hence when the weather causes too quick germination, it is better
to check it by spreading the heap out thinner than by turning it too
frequently over. On comparing different samples of barley, we shall find
that the best develope the germ or acrospire quicker than the radicles,
and thus occasion a greater production of the saccharine principle; this
conversion advances along with the acrospire, and keeps pace with it, so
that the portion of the seed to which it has not reached, is still in
its unaltered starchy state. It is never complete for any single
barleycorn till the acrospire has come to the end opposite to that from
which it sprung; hence one part of the corn may be sugary, while the
other is still insipid. If the grain were allowed to vegetate beyond
this term, the radicles being fully one third of an inch long, the
future stem would become visibly green in the exterior; it would shoot
forth rapidly, the interior of the grain would become milky, with a
complete exhaustion of all its useful constituents, and nothing but the
husk would remain.
In France, the brewers, who generally malt their barley themselves,
seldom leave it on the couch more than 8 or 10 days, which, even taking
into account the warmer climate of their country, is certainly too short
a period, and hence they make inferior wort to the English brewer, from
the same quantity of malt.
At the end of the germination, the radicles have become 1-1/2 longer
than the barley, and are contorted so that the corns hook into one
another, but the acrospire is just beginning to push through. A moderate
temperature of the air is best adapted to malting; therefore it cannot
be carried on well during the heat of summer or the colds of winter.
Malt-floors should be placed in substantial thick-walled buildings,
without access of the sun, so that a uniform temperature of 59° or 60°
may prevail inside. Some recommend them to be sunk a little under the
surface of the ground, if the situation be dry.
During germination a remarkable change has taken place in the substance
of the grain. The glutinous constituent has almost entirely disappeared,
and is supposed to have passed into the matter of the radicles, while a
portion of the starch is converted into sugar and mucilage. The change
is similar to what starch undergoes when dissolved in water, and
digested in a heat of about 160°F. along with a little gluten. The
thick paste becomes gradually liquid, transparent, and sweet tasted, and
the solution contains now, sugar and gum, mixed with some unaltered
starch. The gluten suffers a change at the same time, and becomes
acescent, so that only a certain quantity of starch can be thus
converted by a quantity of gluten. By the artificial growth upon the
malt-floor, all the gluten and albumen present in barley are not
decomposed, and only about one half of the starch is converted into
sugar; the other half, by a continuance of the germination, would only
go to the growth of the roots and stems of the plant; but it receives
its nearly complete conversion into sugar without any notable waste of
substance in the brewer’s operation of mashing.
The _kiln-drying_.--When the malt has become perceptibly dry to the hand
upon the floor, it is taken to the kiln, and dried hard with artificial
heat, to stop all further growth, and enable it to be kept, without
change, for future use, at any time. The malt-kiln, which is
particularly described in the next page, is a round or a square chamber,
covered with perforated plates of cast iron, whose area is heated by a
stove or furnace, so that not merely the plates on which the malt is
laid are warmed, but the air which passes up through the stratum of malt
itself, with the effect of carrying off very rapidly the moisture from
the grains. The layer of malt should be about 3 or 4 inches thick, and
evenly spread, and its heat should be steadily kept at from the 90th to
the 100th degree of Fahrenheit’s scale, till the moisture be mostly
exhaled from it. During this time the malt must be turned over at first
frequently, and latterly every three or four hours. When it is nearly
dry, its temperature should be raised to from 145° to 165°F., and it
must be kept at this heat till it has assumed the desired shade of
colour, which is commonly a brownish-yellow or a yellowish-brown. The
fire is now allowed to die out, and the malt is left on the plates till
it has become completely cool; a result promoted by the stream of cool
air, which now rises up through the bars of the grate; or the thoroughly
dry browned malt may, by damping the fire, be taken hot from the plates,
and cooled upon the floor of an adjoining apartment. The prepared malt
must be kept in a dry loft, where it can be occasionally turned over
till it is used. The period of kiln-drying should not be hurried. Many
persons employ two days in this operation.
According to the colour and the degree of drying, malt is distributed
into three sorts; pale, yellow, and brown. The first is produced when
the highest heat to which it has been subjected is from 90° to 100° F.;
the amber yellow, when it has suffered a heat of 122°; and the brown
when it has been treated as above described. The black malt used by the
porter brewer to colour his beer, has suffered a much higher heat, and
is partially charred. The temperature of the kiln should, in all cases,
be most gradually raised, and most equably maintained. If the heat be
too great at the beginning, the husk gets hard dried, and hinders the
evaporation of the water from the interior substance; and should the
interior be dried by a stronger heat, the husk will probably split, and
the farina become of a horny texture, very refractory in the mash-tun.
In general, it is preferable to brown malt, rather by a long-continued
moderate heat, than by a more violent heat of shorter duration, which is
apt to carbonise a portion of the mucilaginous sugar, and to damage the
article. In this way, the sweet is sometimes converted into a bitter
principle.
During the kiln-drying, the roots and acrospire of the barley become
brittle, and fall off; and are separated by a wire sieve whose meshes
are too small to allow the malt itself to pass through.
A quantity of good barley, which weighs 100 pounds, being judiciously
malted, will weigh, after drying and sifting, 80 pounds. Since the raw
grain, dried by itself at the same temperature as the malt, would lose
12 per cent. of its weight in water, the malt process dissipates out of
these remaining 88 pounds, only 8 pounds, or 8 per cent. of the raw
barley. This loss consists of--
1-1/2 per cent. dissolved out in the steep water,
3 -- dissipated in the kiln,
3 -- by the falling of the fibrils,
1/2 -- of waste.
The bulk of good malt exceeds that of the barley from which it was made,
by about 8 or 9 per cent.
The operation of kiln-drying is not confined to the mere expulsion of
the moisture from the germinated seeds; but it serves to convert into
sugar a portion of the starch which remained unchanged, and that in a
twofold way; first, by the action of the gluten upon the fecula at an
elevated temperature, as also by the species of roasting which the
starch undergoes, and which renders it of a gummy nature. (See STARCH.)
We shall have a proof of this explanation, if we dry one portion of the
malt in a naturally dry atmosphere, and another in a moderately warm
kiln; the former will yield less saccharine extract than the latter.
Moreover, the kiln-dried malt has a peculiar, agreeable, and faintly
burned taste, probably from a small portion of empyreumatic oil formed
in the husk, and which not only imparts its flavour to the beer, but
also contributes to its preservation. It is therefore obvious, that the
skilful preparation of the malt must have the greatest influence both on
the quantity and quality of the worts to be made from it. If the
germination be pushed too far, a part of the extractible matter is
wasted; if it has not advanced far enough, the malt will be too raw, and
too much of its substance will remain as an insoluble starch; if it is
too highly kiln-dried, a portion of its sugar will be caramelised, and
become bitter; and if the sweating was imperfect or irregular, much of
the barley may be rendered lumpy and useless. Good malt is
distinguishable by the following characters:--
The grain is round and full, breaks freely between the teeth, and has a
sweetish taste, an agreeable smell, and is full of a soft flour from end
to end. It affords no unpleasant flavour on being chewed; it is not
hard, so that when drawn along an oaken table across the fibres, it
leaves a white streak, like chalk. It swims upon water, while unmalted
barley sinks in it. Since the quality of the malt depends much on that
of the barley, the same sort only should be used for one malting. New
barley germinates quicker than old, which is more dried up; a couch of a
mixture of the two would be irregular, and difficult to regulate.
[Illustration: 97 98 99 100]
_Description of the malt kiln._--_Figs._ 97, 98, 99, 100. exhibit the
construction of a well-contrived _malt kiln_. _Fig._ 97. is the ground
plan; _fig._ 98. is the vertical section; and _figs._ 99. and 100., a
horizontal and vertical section in the line of the malt-plates. The same
letters denote the same parts in each of the figures. A cast-iron
cupola-shaped oven is supported in the middle, upon a wall of brickwork
four feet high; and beneath it, are the grate and its ash-pit. The smoke
passes off through two equi-distant pipes into the chimney. The oven is
surrounded with four pillars, on whose top a stone lintel is laid: _a_
is the grate, 9 inches below the sole of the oven _b_; _c c c c_ are the
four nine-inch strong pillars of brickwork which bear the lintel _m_; _d
d d d d d_ are strong nine-inch pillars, which support the girder and
joists upon which perforated plates repose; _e_ denotes a vaulted arch
on each of the four sides of the oven; _f_ is the space between the kiln
and the side arch, into which a workman may enter, to inspect and clean
the kiln; _g g_, the walls on either side of the kiln, upon which the
arches rest, _h_, the space for the ashes to fall; _k_, the fire-door of
the kiln; _l l_, junction-pieces to connect the pipes _r r_ with the
kiln; the mode of attaching them is shown in _fig._ 99. These
smoke-pipes lie about three feet under the iron plates, and at the same
distance from the side walls; they are supported upon iron props, which
are made fast to the arches. In _fig._ 98., _u_ shows their section; at
_s s_, _fig._ 99., they enter the chimney, which is provided with two
register or damper plates, to regulate the draught through the pipes.
These registers are represented by _t t_, _fig._ 100., which shows a
perpendicular section of the chimney. _m_, _fig._ 98., is the lintel
which causes the heated air to spread laterally instead of ascending in
one mass in the middle, and prevents any combustible particles from
falling upon the iron cupola. _n n_ are the main girders of iron for the
iron beams _o o_, upon which the perforated plates _p_ lie; _q_, _fig._
98., is the vapour pipe in the middle of the roof, which allows the
steam of the drying malt to escape. The kiln may be heated either with
coal or wood.
The size of this kiln is about 20 feet square; but it may be made
proportionally either smaller or greater. The perforated floor should be
large enough to receive the contents of one steep or couch.
The perforated plate might be conveniently heated by steam pipes, laid
zig-zag, or in parallel lines under it; or a wire-gauze web might be
stretched upon such pipes. The wooden joists of a common floor would
answer perfectly to support this steam-range, and the heat of the pipes
would cause an abundant circulation of air. For drying the pale malt of
the ale brewer, this plan is particularly well adapted.
The kiln-dried malt is sometimes ground between stones in a common corn
mill, like oatmeal; but it is more generally crushed between iron
rollers, at least for the purposes of the London brewers.
[Illustration: 101 102]
The _crushing mill_.--The cylinder malt-mill is constructed as shown in
_fig._ 101, 102. I is the sloping-trough, by which the malt is let down
from its bin or floor to the hopper A of the mill, whence it is
progressively shaken in between the rollers B D. The rollers are of
iron, truly cylindrical, and their ends rest in bearers of hard brass,
fitted into the side frames of iron. A screw E goes through the upright,
and serves to force the bearer of the one roller towards that of the
other, so as to bring them closer together when the crushing effect is
to be increased. G is the square end of the axis, by which one of the
rollers may be turned either by the hand or by power; the other derives
its rotatory motion from a pair of equal-toothed wheels H, which are
fitted to the other end of the axes of the rollers. _d_ is a catch which
works into the teeth of a ratchet-wheel on the end of one of the rollers
(not shown in this view). The lever _c_ strikes the trough _b_ at the
bottom of the hopper, and gives it the shaking motion for discharging
the malt between the rollers, from the slide sluice _a_. _e e_, _fig._
101., are scraper-plates of sheet iron, the edges of which press by a
weight against the surfaces of the rollers, and keep them clean.
Instead of the cylinders, some employ a crushing mill of a
conical-grooved form like a coffee mill, upon a large scale. (_See the
general plan, infrà._)
The _mashing and boiling_.--Mashing is the operation by which the wort
is extracted, or eliminated from the malt, and whereby a
saccharo-mucilaginous extract is made from it. The malt should not in
general be ground into a fine meal, for in that case it would be apt to
form a cohesive paste with hot water, or to set, as it is called, and to
be difficult to drain. In crushed malt, the husk remains nearly entire,
and thus helps to keep the farinaceous particles open and porous to the
action of the water. The bulk of the crushed malt is about one-fifth
greater than that of the whole, or one bushel of malt gives a bushel and
a quarter of crushed malt. This is frequently allowed to lie a few days
in a cool place, in order that it may attract moisture from the air,
which it does very readily by its hygrometric power. Thus, the
farinaceous substance which had been indurated in the kiln, becomes
soft, spongy, and fit for the ensuing process of watery extraction.
Mashing has not for its object merely to dissolve the sugar and gum
already present in the malt, but also to convert into a sweet mucilage
the starch which had remained unchanged during the germination. We have
already stated that starch, mixed with gluten, and digested for some
time with hot water, becomes a species of sugar. This conversion takes
place in the mash-tun. The malted barley contains not only a portion of
gluten, but _diastase_ more than sufficient to convert the starch
contained in it, by this means, into sugar.
The researches of Payen and Persoz show, that the mucilage formed by the
reaction of malt upon starch, may either be converted into sugar, or be
made into permanent gum, according to the temperature of the water in
which the materials are digested. We take of pale barley malt, ground
fine, from 6 to 10 parts, and 100 parts of starch; we heat, by means of
a water-bath, 400 parts of water in a copper, to about 80°F.; we then
stir in the malt, and increase the heat to 140°F., when we add the
starch, and stir well together. We next raise the temperature to 158°,
and endeavour to maintain it constantly at that point, or at least to
keep it within the limits of 167° on the one side, and 158° on the
other. At the end of 20 or 30 minutes, the original milky and pasty
solution becomes thinner, and soon after as fluid nearly as water. This
is the moment in which the starch is converted into gum, or into that
substance which the French chemists call _dextrine_, from its power of
polarising light to the right hand, whereas common gum does it to the
left. If this merely mucilaginous solution, which seems to be a mixture
of gum with a little liquid starch and sugar, be suitably evaporated, it
may serve for various purposes in the arts to which gum is applied, but
with this view, it must be quickly raised to the boiling point, to
prevent the farther operation of the malt upon it. If we wish, on the
contrary, however, to promote the saccharine fermentation, for the
formation of beer, we must maintain the temperature at between 158° and
167° for three or four hours, when the greatest part of the gum will
have passed into sugar, and by evaporation of the liquid at the same
temperature, a starch syrup may be obtained like that procured by the
action of sulphuric acid upon starch. The substance, which operates in
the formation of sugar, or is the peculiar ferment of the sugar
fermentation, may be considered as a residuum of the gluten or vegetable
albumen in the germinating grain: it is reckoned by Payen and Persoz, a
new proximate principle called _diastase_, which is formed during
malting, in the grains of barley, oats, and wheat, and may be separated
in a pure state, if we moisten the malt flour for a few minutes in cold
water, press it out strongly, filter the solution, and heat the clear
liquid in a water bath, to the temperature of 158°. The greater part of
that albuminous azotised substance is thus coagulated, and is to be
separated by a fresh filtration; after which, the clear liquid is to be
treated with alcohol, when a flocky precipitate appears, which is
_diastase_. To purify it still further, especially from the azotised
matter, we should dissolve it in water, and precipitate again with
alcohol. When dried at a low temperature, it appears as a solid white
substance, which contains no azote; is insoluble in alcohol, but
dissolves in water and proof spirit. Its solution is neutral and
tasteless; when left to itself, it changes with greater or less rapidity
according to the temperature, and becomes sour at a temperature of from
149° to 167°. It has the property of converting starch into gum
(dextrine) and sugar, and indeed, when sufficiently pure, with such
energy that one part of it disposes 2000 parts of dry starch to that
change, but it operates the quicker the greater its quantity. Whenever
the solution of diastase with starch or with dextrine is heated to the
boiling point, it loses the sugar-fermenting property. One hundred parts
of well-malted starch appear to contain about one part of this
substance.
We can now understand the theory of malting, and the limits between
which the temperature of the liquor, ought to be maintained in this
operation; namely, the range between 157° and 160°F. It has been
ascertained as a principle in mashing, that the best and soundest
extract of the malt, is to be obtained, first of all, by beginning to
work with water at the lowest of these heats, and to conclude the mash
with water at the highest. Secondly, not to operate the extraction at
once with the whole of the water that is to be employed; but with
separate portions and by degrees. The first portion is added with the
view of penetrating equally the crushed malt, and of extracting the
already formed sugar; the next for effecting the sugar fermentation by
the action of the diastase. By this means also, the starch is not
allowed to run into a cohesive paste, and the extract is more easily
drained from the poorer mass, and comes off in the form of a nearly
limpid wort. The thicker moreover, or the less diluted the mash is, so
much the easier is the wort fined in the boiler or copper by the
coagulation of the albuminous matter: these principles illustrate, in
every condition, the true mode of conducting the mashing process; but
different kinds of malt require a different treatment. Pale and slightly
kilned malt requires a somewhat lower heat than malt highly kilned,
because the former has more undecomposed starch, and is more ready to
become pasty. The former also, for the same reason, needs a more
leisurely infusion than the latter, for its conversion into mucilaginous
sugar. The more sugar the malt contains, the more is its saccharine
fermentation accelerated by the action of the diastase. What has been
here said of pale malt, is still more applicable to the case of a
mixture of raw grain with malt, for it requires still gentler heats, and
more cautious treatment.
III. The mash-tun is a large circular tub with a double bottom; the
uppermost of which is called a false bottom, and is pierced with many
holes. There is a space of about 2 or 3 inches between the two, into
which the stopcocks enter, for letting in the water and drawing off the
wort. The holes of the false bottom should be burned, and not bored, to
prevent the chance of their filling up by the swelling of the wood,
which would obstruct the drainage: the holes should be conical, and
largest below, being about 3/8 of an inch there, and 1/8 at the upper
surface. The perforated bottom must be fitted truly at the sides of the
mash-tun, so that no grains may pass through. The mashed liquor is let
off into a large back, from which it is pumped into the wort coppers.
The mash-tun is provided with a peculiar rotatory apparatus for
agitating the crushed grains and water together, which we shall
presently describe. The size of the wort copper is proportional to the
amount of the brewing, and it must, in general, be at least so large as
to operate upon the whole quantity of wort made from one mashing; that
is, for every quarter of malt mashed, the copper should contain 140
gallons. The mash-tun ought to be at least a third larger, and of a
conical form, somewhat wider below than above. The quantity of water to
be employed for mashing, or the extraction of the wort, depends upon the
greater or less strength to be given to the beer. The seeds of the
crushed malt, after the wort is drawn off, retain still about 32 gallons
of water for every quarter of malt. In the boiling, and evaporation from
the coolers, 40 gallons of water are dissipated from one quarter of
malt; constituting 72 gallons in all. If 13 quarters of barley be taken
to make 1500 gallons of beer, 2400 gallons of water must therefore be
required for the mashing. This example will give an idea of the
proportions for an ordinary quality of beer.
When the mash is to begin, the copper must be filled with water, and
heated. As soon as the water has attained the heat of 145° in summer, or
167° in winter, 600 gallons of it are to be run off into the mash-tun,
and the 13 quarters of crushed malt are to be gradually thrown in and
well intermixed by proper agitation, so that it may be uniformly
moistened, and no lumps may remain. After continuing the agitation in
this way for one half or three-quarters of an hour, the water in the
copper will have approached to its boiling point, when 450 gallons at
the temperature of about 200° are to be run into the mash-tun, and the
agitation is to be renewed till the whole assumes an equally fluid
state: the tun is now to be well covered for the preservation of its
heat, and to be allowed to remain at rest for an hour, or an hour and a
half. The mean temperature of this mash may be reckoned at about 145°.
The time which is necessary for the transmuting heat of the remaining
starch into sugar depends on the quality of the malt. Brown malt
requires less time than pale malt, and still less than a mixture with
raw grain, as already explained. After the mash has rested the proper
time, the tap of the tun is opened, and the clear wort is to be drawn
out into the under back. If the wort that first flows is turbid, it must
be returned into the tun, till it runs clear. The amount of this first
wort may be about 675 gallons. Seven hundred and fifty gallons of water
at the temperature of 200° are now to be introduced up through the
drained malt, into the tun, and the mixture is to be agitated till it
becomes uniform, as before. The mash-tun is then to be covered, and
allowed to remain at rest for an hour. The temperature of this mash is
from 167° to 174°. While the second mash is making, the worts of the
first are to be pumped into the wort copper, and set a-boiling as
speedily as possible. The wort of the second mash is to be drawn off at
the proper time, and added to the copper as fast as it will receive it,
without causing the ebullition to stop.
A third quantity of water amounting to 600 gallons, at 200°, is to be
introduced into the mash-tun, and after half an hour, is to be drawn
off, and either pumped into the wort copper, or reserved for mashing
fresh malt, as the brewer may think fit.
The quantity of extract, per barrel weight, which a quarter of malt
yields to wort, amounts to about 84 lbs. The wort of the first extract
is the strongest; the second contains, commonly, one-half the extract of
the first; and the third, one-half of the second; according to
circumstances.
To measure the degrees of concentration of the worts drawn off from the
tun, a particular form of hydrometer, called a saccharometer, is
employed, which indicates the number of pounds weight of liquid
contained in a barrel of 36 gallons imperial measure. Now, as the barrel
of water weighs 360 lbs., the indication of the instrument when placed
in any wort, shows by how many pounds a barrel of that wort is heavier
than a barrel of water; thus, if the instrument sinks with its poise
till the mark 10 is upon a line with the surface of the liquid, it
indicates that a barrel of that wort weighs ten pounds more than a
barrel of water. See SACCHAROMETER.
Or, supposing the barrel of wort weighs 396 lbs., to convert that number
into specific gravity, we have the following simple rule:--
360 : 396 ∷ 100 : 1·100;
at which density, by my experiments, the wort contains 25 per cent., of
solid extract.
Having been employed to make experiments on the density of worts, and
the fermentative changes which they undergo, for the information of a
committee of the House of Commons, which sat in July and August, 1830, I
shall here introduce a short abstract of that part of my evidence which
bears upon the present subject.
My first object was to clear up the difficulties which, to common
apprehension, hung over the matter, from the difference in the scales
of the saccharometers in use among the brewers and distillers of England
and Scotland. I found that one quarter of good malt would yield to the
porter brewer a barrel Imperial measure of wort, at the concentrated
specific gravity of 1·234. Now, if the decimal part of this number be
multiplied by 360, being the number of pounds weight of water in the
barrel, the product will denote the excess in pounds, of the weight of a
barrel of such concentrated wort, over that of a barrel of water, and
that product is, in the present case, 84·24 pounds.
Mr. Martineau, jun., of the house of Messrs. Whitbread and Company, and
a gentleman connected with another great London brewery, had the
kindness to inform me that their average product from a quarter of malt
was a barrel of 84 lbs. gravity. It is obvious, therefore, that by
taking the mean operation of two such great establishments, I must have
arrived very nearly at the truth.
It ought to be remarked that such a high density of wort as 1·234 is not
the result of any direct experiment in the brewery, for infusion of malt
is never drawn off so strong; that density is deduced by computation
from the quantity and quality of several successive infusions; thus,
supposing a first infusion of the quarter of malt to yield a barrel of
specific gravity 1·112, a second to yield a barrel at 1·091, and a third
a barrel at 1·031, we shall have three barrels at the mean of these
three numbers, or one barrel at their sum, equal to 1·234.
I may here observe that the arithmetical mean or sum is not the true
mean or sum of the two specific gravities; but this difference is either
not known or disregarded by the brewers. At low densities this
difference is inconsiderable, but at high densities it would lead to
serious errors. At specific gravity 1·231, wort or syrup contains one
half of its weight of solid pure saccharum, and at 1·1045 it contains
one fourth of its weight; but the brewer’s rule, when here applied,
gives for the mean specific gravity 1·1155 = (1·231 + 1·000)/2.
The contents in solid saccharine matter at that density are however
27-1/4 per cent. showing the rule to be 2-1/4 lbs. wrong in excess on
100 lbs., or 9 lbs. per barrel.
The specific gravity of the solid dry extract of malt wort is 1·264; it
was taken in oil of turpentine, and the result reduced to distilled
water as unity. Its specific volume is 0·7911, that is, 10 lbs. of it
will occupy the volume of 7·911 lbs. of water. The mean specific
gravity, by computation of a solution of that extract in its own weight
of water, is 1·1166; but by experiment, the specific gravity of that
solution is 1·216, showing considerable condensation of volume in the
act of combination with water.
The following Table shows the relation between the specific gravities of
solutions of malt extract, and the per-centage of solid extract they
contain:
+-----+------+------------+-------+--------+
|Extr.|Water.|Malt Extract| Sugar |Specific|
|Malt.| | in 100. |in 100.|gravity.|
+-----+------+------------+-------+--------+
|600 +| 600 | 50·00 | 47·00 | 1·2180 |
|600 +| 900 | 40·0 | 37·00 | 1·1670 |
|600 +| 1200 | 33·3 | 31·50 | 1·1350 |
|600 +| 1500 | 28·57 | 26·75 | 1·1130 |
|600 +| 1800 | 25·00 | 24·00 | 1·1000 |
+-----+------+------------+-------+--------+
The extract of malt was evaporated to dryness, at a temperature of about
250° F., without the slightest injury to its quality, or any
empyreumatic smell. Bate’s tables have been constructed on solutions of
sugar, and not with solutions of extract of malt, or they agree
sufficiently well with the former, but differ materially from the
latter. Allan’s tables give the amount of a certain form of solid
saccharine matter extracted from malt, and dried at 175° F., in
correspondence to the specific gravity of the solution; but I have found
it impossible to make a solid extract from infusions of malt, except at
much higher temperatures than 175° F. Indeed, the numbers on Allan’s
saccharometer scale clearly show that his extract was by no means dry:
thus, at 1·100 of gravity he assigns 29·669 per cent. of solid
saccharine matter; whereas there is at that density of solid extract
only 25 per cent. Again, at 1·135, Allan gives 40 parts per cent. of
solid extract, whereas there are only 33-1/3 present.
By the triple mashing operations above described, the malt is so much
exhausted that it can yield no further extract useful for strong beer or
porter. A weaker wort might no doubt still be drawn off for small beer,
or for contributing a little to the strength of the next mashing of
fresh malt. But this I believe is seldom practised by respectable
brewers, as it impoverishes the grains which they dispose of for feeding
cattle.
The wort should be transferred into the copper, and made to boil as soon
as possible, for if it remains long in the under-back it is apt to
become acescent. The steam moreover raised from it in the act of boiling
serves to screen it from the oxygenating or acidifying influence of the
atmosphere. Until it begins to boil, the air should be excluded by some
kind of a cover.
Sometimes the first wort is brewed by itself into strong ale, the second
by itself into an intermediate quality; and the third into small beer;
but this practice is not much followed in this country.
We shall now treat of the boiling in of the hops. The wort drawn from
the mash-tun, whenever it is pumped into the copper, must receive its
allowance of hops. Besides evaporating off a portion of the water, and
thereby concentrating the wort, boiling has a twofold object. In the
first place, it coagulates the albuminous matter, partly by the heat,
and partly by the principles in the hops, and thereby causes a general
clarification of the whole mass, with the effect of separating the muddy
matters in a flocculent form. Secondly, during the ebullition, the
residuary starch and hordeine of the malt are converted into a limpid
sweetish mucilage, the _dextrine_ above described; while some of the
glutinous stringy matter is rendered insoluble by the tannin principle
of the hops, which favours still further the clearing of the wort. By
both operations the keeping quality of the beer is improved. This boil
must be continued during several hours; a longer time for the stronger,
and a shorter for the weaker beers. There is usually one seventh or one
sixth part of the water dissipated in the boiling copper. This process
is known to have continued a sufficient time, if the separation of the
albuminous flocks is distinct, and if these are found, by means of a
proof gauge suddenly dipped to the bottom, to be collected there, while
the supernatant liquor has become limpid. Two or three hours’ boil is
deemed long enough in many well-conducted breweries; but in some of
those in Belgium, the boiling is continued from 10 to 15 hours, a period
certainly detrimental to the aroma derived from the hop.
Many prefer adding the hops when the wort has just come to the boiling
point. Their effect is to repress the further progress of fermentation,
and especially the passage into the acetous stage, which would otherwise
inevitably ensue in a few days. In this respect, no other vegetable
production hitherto discovered can be a substitute for the hop. The
odorant principle is not so readily volatilised as would at first be
imagined; for when hop is mixed with strong beer wort, and boiled for
many hours, it can still impart a very considerable degree of its
flavour to weaker beer. By mere infusion in hot beer or water, without
boiling, the hop loses very little of its soluble principles. The tannin
of the hop combines, as we have said, with the vegetable albumen of the
barley, and helps to clarify the liquor. Should there be a deficiency of
albumen and gluten, in consequence of the mashing having been done at
such a heat as to have coagulated them beforehand, the defect may be
remedied by the addition of a little gelatine to the wort copper, either
in the form of calf’s foot, or of a little isinglass. If the hops be
boiled in the wort for a longer period than 5 or 6 hours, they lose a
portion of their fine flavour; but if their natural flavour be rank, a
little extra boiling improves it. Many brewers throw the hops in upon
the surface of the boiling wort, and allow them to swim there for some
time, that the steam may penetrate them, and open their pores for a
complete solution of their principles when they are pushed down into the
liquor. It is proper to add the hops in considerable masses, because in
tearing them asunder, some of the lupuline powder is apt to be lost.
The quantity of hop to be added to the wort varies according to the
strength of the beer, the length of time it is to be kept, or the heat
of the climate where it is intended to be sent. For strong beer, 4-1/2
lbs. of hops are required to a quarter of malt, when it is to be highly
aromatic and remarkably clear. For the stronger kinds of ale and porter,
the rule, in England, is to take a pound of hops for every bushel of
malt, or 8 lbs. to a quarter. Common beer has seldom more than a quarter
of a pound of hops to the bushel of malt.
It has been attempted to form an extract of hops by boiling in covered
vessels, so as not to lose the oil, and to add this instead of the hop
itself to the beer. On the great scale this method has no practical
advantage, because the extraction of the hop is perfectly accomplished
during the necessary boiling of the wort, and because the hop operates
very beneficially, as we have explained, in clarifying the beer. Such an
extract, moreover, could be easily adulterated.
_Of the Coolers._--The contents of the copper are run into what is
called the hop-back, on the upper part of which is fixed a drainer, to
keep back the hops. The pump is placed in the hop-back, for the purpose
of raising the wort to the coolers, usually placed in an airy situation
upon the top of the brewery. Two coolers are indispensable when we make
two kinds of beer from the same brewing, and even in single brewings,
called _gyles_, if small beer is to be made. One of these coolers ought
to be placed above the level of the other. As it is of great consequence
to cool the worts down to the fermenting pitch as fast as possible,
various contrivances have been made for effecting this purpose. The
common cooler is a square wooden cistern, about 6 inches deep, and of
such an extent of surface that the whole of one boil may only occupy 2
inches, or thereabouts, of depth in it. For a quantity of wort equal to
about 1500 gallons its area should be at least 54 feet long and 20 feet
wide. The seams of the cooler must be made perfectly water-tight and
smooth, so that no liquor may lodge in them when they are emptied. The
utmost cleanliness is required, and an occasional sweetening with
lime-water.
The hot wort reaches the cooler at a temperature of from 200° to 208°,
according to the power of the pump. Here it should be cooled to the
proper temperature for the fermenting tun, which may vary from 54° to
64°, according to circumstances. The refrigeration is accomplished by
the evaporation of a portion of the liquor: it is more rapid in
proportion to the extent of the surface, to the low temperature, and the
dryness of the atmosphere surrounding the cooler. The renewal of a body
of cool dry air by the agency of a fan, may be employed with great
advantage. The cooler itself must be so placed that its surface shall be
freely exposed to the prevailing wind of the district, and be as free as
possible from the eddy of surrounding buildings. It is thought by many,
that the agitation of the wort during its cooling, is hurtful. Were the
roof made moveable, so that the wort could be readily exposed, in a
clear night, to the aspect of the sky, it would cool rapidly by
evaporation, on the principles explained by Dr. Wells, in his “Essay on
Dew.”
When the cooling is effected by evaporation alone, the temperature falls
very slowly, even in cold air, if it be loaded with moisture. But when
the air is dry, the evaporation is vigorous, and the moisture exhaled
does not remain incumbent on the liquor, as in damp weather, but is
diffused widely in space. Hence we can understand how wort cools so
rapidly in the spring and autumn, when the air is generally dry, and
even more quickly than in winter, when the air is cooler, but loaded
with moisture. In fact, the cooling process goes on better when the
atmosphere is from 50° to 55°, than when it falls to the freezing point,
because in this case, if the air be still, the vapours generated remain
on the surface of the liquor, and prevent further evaporation. In summer
the cooling can take place only during the night.
In consequence of the evaporation during this cooling process, the bulk
of the worts is considerably reduced; thus, if the temperature at the
beginning was 208°, and if it be at the end 64°, the quantity of water
necessary to be evaporated to produce this refrigeration would be nearly
1/8 of the whole, putting radiation and conduction of heat out of the
question. The effect of this will be a proportional concentration of the
beer.
The period of refrigeration in a well-constructed cooler, amounts to 6
or 7 hours in favourable weather, but to 12 or 15 in other
circumstances. The quality of the beer is much improved by shortening
this period; because, in consequence of the great surface which the wort
exposes to the air, it readily absorbs oxygen, and passes into the
acetous fermentation with the production of various mouldy spots; an
evil to which ill-hopped beer is particularly liable. Various schemes
have been contrived to cool wort, by transmitting it through the
convolutions of a pipe immersed in cold water. The best plan is to
expose the hot wort for some hours freely to the atmosphere and the
cooler, when the loss of heat is most rapid by evaporation and other
means, and when the temperature falls to 100°, or thereby, to transmit
the liquor through a zig-zag pipe, laid almost horizontally in a trough
of cold water. The various methods described under _Refrigerator_ are
more complex, but they may be practised in many situations with
considerable advantage.
Whilst the wort reposes in the cooler, it lets fall a slight sediment,
which consists partly of fine flocks of coagulated albumen combined with
tannin, and partly of starch, which had been dissolved at the high
temperature, and separates at the lower. The wort should be perfectly
limpid, for a muddy liquor never produces transparent beer. Such beer
contains, besides mucilaginous sugar and gum, usually some starch, which
even remains after the fermentation, and hinders its clarifying, and
gives it a tendency to sour. The wort contains more starch the hotter it
has been mashed, the less hops have been added, and the shorter time it
has been boiled. The presence of starch in the wort may be made manifest
by adding a little solution of iodine in alcohol to it, when it will
become immediately blue. We thus see that the tranquil cooling of wort
in a proper vessel has an advantage over cooling it rapidly by a
refrigeratory apparatus. When the wort is sufficiently cool, it is let
down into the fermenting tun. In this transfer, the cooling might be
carried several degrees lower, were the wort made to pass down through a
tube inclosed in another tube, along which a stream of cold water is
flowing in the opposite direction, as we have described in the sequel of
ACETIC ACID. These fermenting tuns are commonly called _gyle-tuns_, or
working tuns, and are either square or circular, the latter being
preferable on many accounts.
IV. _Of the Fermentation._--In the great London breweries, the size of
these fermenting tuns is such that they contain from 1200 to 1500
barrels. The quantity of wort introduced at a time must, however, be
considerably less than the capacity of the vessel, to allow room for the
head of yeast which rises during the process; if the vessel be
cylindrical, this head is proportional to the depth of the worts. In
certain kinds of fermentation, it may rise to a third of that depth. In
general, the fermentation proceeds more uniformly and constantly in
large masses, because they are little influenced by vicissitudes of
temperature; smaller vessels, on the other hand, are more easily
handled. The _general_ view of fermentation will be found under that
title; I shall here make a few remarks on what is peculiar to beer.
During the fermentation of wort, a portion of its saccharine matter is
converted into alcohol, and wort thus changed, is beer. It is necessary
that this conversion of the sugar be only partial, for beer which
contains no undecomposed sugar would soon turn sour, and even in the
casks its alcohol undergoes a slow fermentation into vinegar. The amount
of this excess of sugar is greater in proportion to the strength of the
wort, since a certain quantity of alcohol, already formed, prevents the
operation of the ferment on the remaining wort. Temperature has the
greatest influence upon the fermentation of wort. A temperature of from
55° to 60° of the liquor, when that of the atmosphere is 55°, is most
advantageous for the commencement. The warmth of the wort as it comes
into the gyle-tun must be modified by that of the air in the apartment.
In winter, when this apartment is cold, the wort should not be cooled
under 64° or 60°, as in that case the fermentation would be tedious or
interrupted, and the wort liable to spoil or become sour. In summer,
when the temperature of the place rises to above 75°, the wort should be
cooled, if possible, down to 55°, for which purpose it should be let in
by the system of double pipes, above mentioned. The higher the
temperature of the wort, the sooner will the fermentation begin and end,
and the less is it in our power to regulate its progress. The expert
brewer must steer a middle course between these two extremes, which
threaten to destroy his labours. In some breweries a convoluted pipe is
made to traverse or go round the sides of the gyle-tun, through which
warm water is allowed to flow in winter, and cold in summer, so as to
modify the temperature of the mass to the proper fermenting pitch. If
there be no contrivance of this kind, the apartment may be cooled in
summer, by suspending wet canvas opposite the windows in warm weather,
and kindling a small stove within it in cold.
When the wort is discharged into the gyle-tun, it must receive its dose
of yeast, which has been previously mixed with a quantity of the wort,
and left in a warm place till it has begun to ferment. This mixture,
called _lobb_, is then to be put into the tun, and stirred well through
the mass. The yeast should be taken from similar beer. Its quantity must
depend upon the temperature, strength, and quantity of the wort. In
general, one gallon of yeast is sufficient to set 100 gallons of wort in
complete fermentation. An excess of yeast is to be avoided, lest the
fermentation should be too violent, and be finished in less than the
proper period of 6 or 8 days. More yeast is required in winter than
summer; for, at a temperature of 50°, a double quantity may be used to
that at 68°.
Six or eight hours after adding the yeast, the tun being meanwhile
covered, the fermentation becomes active: a white milky-looking froth
appears, first on the middle, and spreads gradually over the whole
surface; but continues highest in the middle, forming a frothy
elevation, the height of which increases with the progress of the
fermentation, and whose colour gradually changes to a bright brown, the
result, apparently, of the oxidation of the extractive contained in this
yeasty top. This covering screens the wort from the contact of the
atmospherical air. During this time, there is a perpetual disengagement
of carbonic acid gas, which is proportional to the quantity of sugar
converted into alcohol. The warmth of the fermenting liquid increases at
the same time, and is at a maximum when the fermentation has come to its
highest point. This increase of temperature amounts to from 9° to 14° or
upwards, and is the greater the more rapid the fermentation. But in
general, the fermentation is not allowed to proceed so far in the
gyle-tun, for after it is advanced a little way, the beer is _cleansed_,
that is, drawn off into other vessels, which are large barrels set on
end, with large openings in their top, furnished with a sloping tray for
discharging an excess of yeast into the wooden trough, in which the
_stillions_ stand. These _stillions_ are placed in communication with a
store-tub, which keeps them always full, by hydrostatic pressure, so
that the head of yeast may spontaneously flow over, and keep the body of
liquor in the cask clean. This apparatus will be explained in describing
the brewery plant. See the _figures, infrà_.
It must be observed, that the quantity of yeast, and the heat of
fermentation, differ for every different quality of beer. For mild ale,
when the fermentation has reached 75°, its first flavour begins; at 80°
the flavour increases; at 85° it approaches the high flavour; at 90° it
is high; but it may be carried to 100° and upwards, for particular
purposes. A wort of 30 lbs. per barrel (sp. gr. 1·088), ought to
increase about 15°, so that in order to arrive at 80°, it should be set
at 65°. The quantity of yeast for such an ale should be from 2 to 3 lbs.
per barrel. The higher the heat, the less yeast is necessary. If the
heat of the fermentation should at any time fall, it must be raised by a
supply of fresh yeast, well stirred in; but this practice is not
advisable in general, because rousing the worts in the gyle-tun is apt
to communicate a rank flavour of yeast to the ale. It is the practice of
many experienced brewers to look every 2 hours into the gyle-tun,
chiefly with the view of observing the progress of the heat, which is
low at first, but afterwards often increases half a degree per hour, and
subsequently declines, as the fermentation approaches its conclusion,
till at length the heat becomes uniform, or sometimes decreases, before
the fermentation is finished, especially where the quantity operated
upon is small.
Some brewers recommend, when the fermentation is carried to its utmost
period, to add about 7 lbs. of wheat or bean flour to a gyle-tun of 25
or 30 barrels, at the time of _cleansing_, so as to quicken the
discharge of the yeast, by disengagement of more carbonic acid. The
flour should be whisked up in a pail, with some of the beer, till the
lumps are broken, and then poured in. By early cleansing, the yeast is
preserved longer in a state proper for a perfect fermentation than by a
contrary practice.
For old ale, which is to be long kept, the heat of the fermentation
should not exceed 75°, but a longer time is required to complete the
fermentation and ensure the future good flavour of the ale.
For porter, the general practice is, to use from 4 to 4-1/2 lbs. of hops
per barrel for keeping; though what is termed mild or mixing porter, has
not more than 3 or 3-1/2 lbs. The heat of fermentation must not exceed
70°, and begin about 60°. If the heat tend to increase much above that
pitch in the gyle-tun, the porter should be _cleansed_, by means of the
_stillions_. At this period of the fermentation, care should be taken
that the sweetness of the malt be removed, for which purpose more yeast
may be used than with any other beer of the same strength. The quantity
is from 3 to 4 lbs. per barrel, rousing the wort in the gyle-tun every 2
hours in the day-time.
When the plan of _cleansing_ casks is not employed, the yeast is removed
from the surface of the fermenting tun by a skimmer, and the clear beer
beneath is then drawn off into the ripening tuns, called _store-vats_,
in which it is mixed up with different brewings, to suit the taste of
the customers. This transfer must take place whenever the extrication of
carbonic acid has nearly ceased; lest the alcohol formed should dissolve
some of the floating yeast, acquire thereby a disagreeable taste, and
pass partially into the acetous state.
In this process, during the formation of vinous spirit at the expense of
the sugar, the albumen and gluten diffused through the beer, being acted
upon by the alcohol, become insoluble; one portion of them is buoyed to
the top with the carbonic acid gas, to form the frothy yeast; and
another portion falls to form the bottom barm. The former consists of
the same materials as the wort, with a large proportion of gluten, which
forms its active constituent; the latter is a peculiar deposit,
consisting of the same gluten mixed with the various dense impurities of
the wort, and may be also used as a ferment, but is cruder than the
floating yeast. The amount of yeast is proportional to the activity of
the fermentation, or extrication of carbonic acid gas, as also to the
heat of the mashing process, and the quantity of starch or flour
unaltered by germination. Pale malt affords usually, more yeast than
malt highly kilned. When the yeast becomes excessive, from too violent
fermentation, it should be skimmed off from time to time, which will
tend to cool the liquor and moderate the intestine changes.
After the beer is let down into the close store-tuns in the cellar, an
obscure fermentation goes on, for a considerable period in its body,
which increases its spirituous strength, and keeps up in it a constant
impregnation of carbonic acid gas, so as to render it lively and
agreeable to the taste, when it is casked off for sale. It would appear,
that beer is never stationary in quality, while it is contained in the
tuns; for the moment when it ceases to improve by the decomposition of
its residuary sugar, it begins to degenerate into vinegar. This result
may be produced either by the exhaustion of the saccharine, or by the
fermentative matter. The store cellar should therefore be under ground,
free from alternations of temperature, vibrations of carriages, and as
cool as possible. In the great London breweries, the fermentation is
rendered very complete in the cleansing butts; so that a slow and steady
ripening is ensured in the great store-tuns. The gyle-tuns are too
capacious to permit the fermentation to be finished, with either safety
or sufficient dispatch in them.
V. OF RIPENING DIFFERENT KINDS OF BEER.--The varieties of beer depend
either upon the difference of their materials, or from a different
management of the brewing processes.
With regard to the materials, beers differ in the proportion of their
malt, hops, and water; and in the different kinds of malt or other
grain. To the class of table or small beers, all those sorts may be
referred whose specific gravity does not exceed 1·025, which contain
about 5 per cent. of malt extract, or nearly 18 pounds per barrel. Beers
of middling strength may be reckoned those between the density of 1·025
and 1·040; which contain, at the average, 7 per cent., or 25 pounds per
barrel. The latter may be made with 400 quarters of malt to 1500 barrels
of beer. Stronger beers have a specific gravity of from 1·050 to 1·080,
and take from 45 to 75 quarters of malt to the same quantity of beer.
The strongest beer found in the market is some of the English and Scotch
ales, for which from 18 to 27 quarters of malt are taken for 1500
gallons of beer. Good porter requires from 16 to 18 quarters for that
quantity. Beers are sometimes made with the addition of other
farinaceous matter to the malt; but when the latter constitutes the main
portion of the grain, the malting of the other kinds of corn becomes
unnecessary, for the diastase of the barley-malt changes the starch into
sugar during the mashing operation. Even with entirely raw grain, beer
is made in some parts of the Continent, the brewers trusting the
conversion of the starch into sugar to the action of the gluten alone,
at a low mashing temperature, on the principle of Saussure’s and
Kirchoff’s researches.
The colour of the beer depends upon the colour of the malt, and the
duration of the boil in the copper. The pale ale is made, as we have
stated, from steam or sun-dried malt, and the young shoots of the hop;
the deep yellow ale from a mixture of pale yellow and brown malt; and
the dark brown beer from well-kilned and partly carbonised malt, mixed
with a good deal of the pale, to give body. The longer and more strongly
heated the malt has been in the kiln, the less weight of extract,
_cæteris paribus_, does it afford. In making the fine mild ales, high
temperatures ought to be avoided, and the yeast ought to be skimmed off,
or allowed to flow very readily from its top, by means of the cleansing
butt system, so that little ferment being left in it to decompose the
rest of the sugar, the sweetness may remain unimpaired. With regard to
porter, in certain breweries, each of the three kinds of malt employed
for it is separately mashed, after which the first and the half of the
second wort is boiled along with the whole of the hops, and thence
cooled and set to ferment in the gyle-tun. The third drawn wort, with
the remaining half of the second, is then boiled with the same hops,
saved by the drainer, and, after cooling, added to the former in the
gyle-tun, when the two must be well roused together.
It is obvious, from the preceding development of principles, that all
amylaceous and saccharine materials, such as potatoes, beans, turnips,
as well as cane and starch syrup, molasses, &c., may be used in brewing
beer. When, however, a superior quality of brown beer is desired, malted
barley is indispensable, and even with these substitutes a mixture of it
is most advantageous. The washed roots of the common carrot, of the red
and yellow beet, or of the potato, must be first boiled in water, and
then mashed into a pulp. This pulp must be mixed with water in the
copper, along with wheaten or oat meal, and the proper quantity of hops,
then boiled during 8 or 9 hours. This wort is to be cooled in the usual
way, and fermented, with the addition of yeast. A much better process is
that now practised, on a considerable scale, at Strasbourg, in making
the ale, for which that city is celebrated. The mashed potatoes are
mixed with from a twentieth to a tenth of their weight of finely ground
barley malt, and some water. The mixture is exposed, in a water-bath, to
a heat of 160° F. for four hours, whereby it passes into a saccharine
state, and may then be boiled with hops, cooled, and properly fermented
into good beer.
Maize, or Indian corn, has also been employed to make beer; but its
malting is somewhat difficult on account of the rapidity and vigour with
which its radicles and plumula sprout forth. The proper mode of causing
it to germinate is to cover it, a few inches deep, with common soil, in
a garden or field, and to leave it there till the bed is covered with
green shoots of the plant. The corn must be then lifted, washed, and
exposed to the kiln.
_The Difference of the Fermentation._--The greater or less rapidity with
which the worts are made to ferment has a remarkable influence upon the
quality of the beer, especially in reference to its fitness for keeping.
The wort is a mucilaginous solution in which the yeastly principles,
eliminated by the fermentation, will, if favoured by regular and slow
intestine movements, completely rise to the surface, or sink to the
bottom, so as to leave the body fine. But, when the action is too
violent, these barmy glutinous matters get comminuted and dispersed
through the liquor, and can never afterwards be thoroughly separated. A
portion of the same feculent matter becomes, moreover, permanently
dissolved, during this furious commotion, by the alcohol that is
generated. Thus the beer loses not merely its agreeable flavour and
limpidity, but is apt to spoil from the slightest causes. The slower,
more regularly progressive, and less interrupted, therefore, the
fermentation is, so much better will the product be.
Beer, in its perfect condition, is an excellent and healthful beverage,
combining, in some measure, the virtues of water, of wine, and of food,
as it quenches thirst, stimulates, cheers, and strengthens. The vinous
portion of it is the alcohol, proceeding from the fermentation of the
malt sugar. Its amount, in common strong ale or beer, is about 4 per
cent., or four measures of spirits, specific gravity 0·825 in 100
measures of the liquor. The best brown stout porter contains 6 per
cent., the strongest ale even 8 per cent.; but common beer only one. The
nutritive part of the beer is the undecomposed gum-sugar, and the
starch-gum, not changed into sugar. Its quantity is very variable,
according to the original starch of the wort, the length of the
fermentation, and the age of the beer.
The main feature of good beer is fine colour and transparency; the
production of which is an object of great interest to the brewer.
Attempts to clarify it in the cask seldom fail to do it harm. The only
thing that can be used with advantage for _fining_ foul or muddy beer,
is isinglass. For porter, as commonly brewed, it is frequently had
recourse to. A pound of good isinglass will make about 12 gallons of
_finings_. It is cut into slender shreds, and put into a tub with as
much vinegar or hard beer as will cover it, in order that it may swell
and dissolve. In proportion as the solution proceeds, more beer must be
poured upon it, but it need not be so acidulous as the first, because,
when once well softened by the vinegar, it readily dissolves. The
mixture should be frequently agitated with a bundle of rods, till it
acquires the uniform consistence of thin treacle, when it must be
equalised still more by passing through a tammy cloth, or a sieve. It
may now be made up with beer to the proper measure of dilution. The
quantity generally used is from a pint to a quart per barrel, more or
less, according to the foulness of the beer. But before putting it into
the butt, it should be diffused through a considerable volume of the
beer with a whisk, till a frothy head be raised upon it. It is in this
state to be poured into the cask, briskly stirred about; after which the
cask must be bunged down for at least 24 hours, when the liquor should
be limpid. Sometimes the beer will not be improved by this treatment;
but this should be ascertained beforehand, by drawing off some of the
beer into a cylindric jar or phial, and adding to it a little of the
finings. After shaking and setting down the glass, we shall observe
whether the feculencies begin to collect in flocky parcels, which slowly
subside; or whether the isinglass falls to the bottom without making any
impression upon the beer. This is always the case when the fermentation
is incomplete, or a secondary decomposition has begun. Mr. Jackson has
accounted for this clarifying effect of isinglass in the following way.
The isinglass, he thinks, is first of all rather diffused mechanically,
than chemically dissolved, in the sour beer or vinegar, so that when the
finings are put into the foul beer, the gelatinous fibres, being set
free in the liquor, attract and unite with the floating feculencies,
which before this union were of the same specific gravity with the beer,
and therefore could not subside alone; but having now acquired
additional weight by the coating of fish-glue, precipitate as a
flocculent magma. This is Mr. Jackson’s explanation; to which I would
add, that if there be the slightest disengagement of carbonic acid gas,
it will keep up an obscure locomotion in the particles, which will
prevent the said light impurities, either alone or when coated with
isinglass, from subsiding. The beer is then properly enough called
_stubborn_ by the coopers. But the true theory of the action of
isinglass is, that the tannin of the hops combines with the fluid
gelatine, and forms a flocculent mass, which envelopes the muddy
particles of the beer, and carries them to the bottom as it falls, and
forms a sediment. When after the finings are poured in, no proper
precipitate ensues, it may be made to appear by the addition of a little
decoction of hop.
Mr. Richardson, the author of the well-known brewer’s saccharometer,
gives the following as the densities of different kinds of beer:--
+-----------------------+------------------+-----------------+
| Beer. |Pounds per Barrel.|Specific Gravity.|
+-----------------------+------------------+-----------------+
|Burton ale, 1st sort | 40 to 43 | 1·111 to 1·120 |
| 2d ditto | 35 to 40 | 1·097 to 1·111 |
| 3d ditto | 28 to 33 | 1·077 to 1·092 |
|Common ale | 25 to 27 | 1·070 to 1·073 |
|Ditto ditto | 21 | 1·058 |
|Porter, common sort | 18 | 1·050 |
|Ditto, double | 20 | 1·055 |
|Ditto, brown stout | 23 | 1·064 |
|Ditto, best brown stout| 26 | 1·072 |
|Common small beer | 6 | 1·014 |
|Good table beer | 12 to 14 | 1·033 to 1·039 |
+-----------------------+------------------+-----------------+
_Of Returns or Malt Residuums._--When small beer is brewed after ale or
porter, only one mash is to be made; but where this is not done, there
may be two mashes, in order to economise malt to the utmost. We may let
on the water at 160° or 165°, in any convenient quantity, infuse for an
hour or thereby, then run it off, and pump into the copper, putting some
hops into it, and causing it to boil for an instant; when it may be
transferred to the cooler. A second mash or return may be made in the
same manner, but at a heat 5° lower; and then disposed of in the boiler
with some hops, which may remain in the copper during the night at a
scalding heat, and may be discharged into the cooler in the morning.
These two returns are to be let down into the under-back immediately
before the next brewing, and thence heated in the copper for the next
mashing of fresh malt, instead of hot water, commonly called _liquor_,
in the breweries. But allowance must be made, in the calculation of the
worts, for the quantity of fermentable matter in these two returns. The
nett aggregate saving is estimated from the gravity of the return taken
when cold in the cooler. A slight economy is also made in the extra
boiling of the used hops. The lapse of a day or two between the
consecutive brewings is no objection to the method of _returns_, because
they are too weak in saccharine matter to run any risk of fermentation.
In conclusion, it may be remarked that Mr. Richardson somewhat
underrates the gravity of porter, which is now seldom under 20 lbs. per
barrel. The criterion for transferring from the gyle-tun to the
cleansing butts is the attenuation caused by the production of alcohol
in the beer: when that has fallen to 10 lbs. or 11 lbs., which it
usually does in 48 hours, the cleansing process is commenced. The heat
is at this time generally 75°, if it was pitched at 65°; for the heat
and the attenuation go hand in hand.
About thirty years ago, it was customary for the London brewers of
porter, to keep immense stocks of it for eighteen months or two years,
with the view of improving its quality. The beer was pumped from the
cleansing butts into store-vats, holding from twenty to twenty-five
gyles or brewings of several hundred barrels each. The store-vats had
commonly a capacity of 5000 or 6000 barrels; and a few were double, and
one was treble, this size. The porter, during its long repose in these
vats, became fine, and by obscure fermentation its saccharine mucilage
was nearly all converted into vinous liquor, and dissipated in carbonic
acid. Its hop-bitter was also in a great degree decomposed. _Good hard
beer_ was the boast of the day. This was sometimes softened by the
publican, by the addition of some mild new-brewed beer. Of late years,
the taste of the metropolis has undergone such a complete revolution in
this respect, that nothing but the mildest porter will now go down.
Hence, six weeks is a long period for beer to be kept in London; and
much of it is drunk when only a fortnight old. Ale is for the same
reason come greatly into vogue; and the two greatest porter houses,
Messrs. Barclay, Perkins, & Co., and Truman, Hanbury, & Co., have become
extensive and successful brewers of mild ale, to please the changed
palate of their customers.
We shall add a few observations upon the brewing of Scotch ale. This
beverage is characterised by its pale amber colour, and its mild
balsamic flavour. The bitterness of the hop is so mellowed with the
malt, as not to predominate. The ale of Preston Pans is, in fact, the
best substitute for wine which barley has hitherto produced. The low
temperature at which the Scotch brewer pitches his fermenting tun
restricts his labours to the colder months of the year. He does nothing
during four of the summer months. He is extremely nice in selecting his
malt and hops; the former being made from the best English barley, and
the latter being the growth of Farnham or East Kent. The yeast is
carefully looked after, and measured into the fermenting tun in the
proportion of one gallon to 240 gallons of wort.
Only one mash is made by the Scotch ale brewer, and that pretty strong;
but the malt is exhausted by eight or ten successive sprinklings of
liquor (hot water) over the goods (malt), which are termed in the
vernacular tongue, _sparges_. These waterings percolate through the malt
on the mash-tun bottom, and extract as much of the saccharine matter as
may be sufficient for the brewing. By this simple method much higher
specific gravities may be obtained than would be practicable by a second
mash. With malt, the infusion or saccharine fermentation of the
_diastase_ is finished with the first mash; and nothing remains but to
wash away from the goods the matter which that process has rendered
soluble. It will be found on trial that 20 barrels of wort drawn from a
certain quantity of malt, by two successive mashings, will not be so
rich in fermentable matter as 20 barrels extracted by ten successive
sparges of two barrels each. The grains always remain soaked with wort
like that just drawn off, and the total residual quantity is three
fourths of a barrel for every quarter of malt. The gravity of this
residual wort will on the first plan be equal to that of the second
mash; but on the second plan, it will be equal only to that of the tenth
sparge, and will be more attenuated in a very high geometrical ratio.
The only serious objection to the sparging system is the loss of time by
the successive drainages. A mash-tun with a steam jacket, promises to
suit the sparging system well; as it would keep up an uniform
temperature in the goods, without requiring them to be sparged with very
hot liquor.
The first part of the Scotch process seems of doubtful economy; for the
mash liquor is heated so high as 180°. After mashing for about half an
hour, or till every particle of the malt is thoroughly drenched, the tun
is covered, and the mixture left to infuse about three hours; it is then
drained off into the under-back, or preferably into the wort copper.
After this wort is run off, a quantity of liquor (water), at 180° of
heat, is sprinkled uniformly over the surface of the malt; being first
dashed on a perforated circular board, suspended horizontally over the
mash-tun, wherefrom it descends like a shower upon the whole of the
goods. The percolating wort is allowed to flow off, by three or more
small stopcocks round the circumference of the mash-tun, to insure the
equal diffusion of the liquor.
The first sparge being run off in the course of twenty minutes, another
similar one is affused; and thus in succession till the whole of the
drainage, when mixed with the first mash-wort, constitutes the density
adapted to the quality of the ale. Thus, the strong worts are prepared,
and the malt is exhausted either for table beer, or for a _return_, as
pointed out above. The last sparges are made 5° or 6° cooler than the
first.
The quantity of hops seldom exceeds four pounds to the quarter of malt.
The manner of boiling the worts is the same as that above described; but
the conduct of the fermentation is peculiar. The heat is pitched at 50°,
and the fermentation continues from a fortnight to three weeks. Were
three brewings made in the week, seven or eight working tuns would thus
be in constant action; and, as they are usually in one room, and some of
them at an _elevation_ of temperature of 15°, the apartment must be
propitious to fermentation, however low its heat may be at the
commencement. No more yeast is used than is indispensable: if a little
more be needed, it is made effective by rousing up the tuns twice a day
from the bottom.
When the progress of the attenuation becomes so slack as not to exceed
half a pound in the day, it is prudent to cleanse, otherwise the top
harm might re-enter the body of the beer, and it would become
_yeast-bitten_. When the ale is cleansed, the head, which has not been
disturbed for some days, is allowed to float on the surface till the
whole of the _then_ pure ale is drawn off into the casks. This top is
regarded as a sufficient preservative against the contact of the
atmosphere. The Scotch do not skim their tuns, as the London ale brewers
commonly do. The Scotch ale, when so cleansed, does not require to be
set upon close stillions. It throws off little or no yeast, because the
fermentation was nearly finished in the tun. The strength of the best
Scotch ale ranges between 32 and 44 pounds to the barrel; or it has a
specific gravity of from 1·088 to 1·122, according to the price at which
it is sold. In a good fermentation, seldom more than a fourth of the
original gravity of the wort remains at the period of the cleansing.
Between one third and one fourth is the usual degree of attenuation.
Scotch ale soon becomes fine, and is seldom racked for the home market.
The following table will show the progress of fermentation in a brewing
of good Scotch ale:--
20 barrels of mash-worts of 42-1/2 pounds gravity = 860·6
20 -- returns 6-1/10 = 122
-----
12 ) 982·6
-----
pounds weight of extract per quarter of malt = 81
Fermentation:--
March 24. pitched the tun at 51°: yeast 4 gallons.
Temp. Gravity.
25. 52° 41 pounds.
28. 56° 39
30. 60° 34
April 1. 62° 32
4. 65° 29 added 1 lb. of yeast.
5. 66° 25
6. 67° 23
7. 67° 20
8. 66° 18
9. 66° 15
10. 64° 14·5 cleansed[7].
[7] BREWING (Society for diffusing Useful Knowledge), p. 156.
The following table shows the origin and the result of fermentation, in
a number of practical experiments:--
+--------+----------+-----------+----------+------------+
|Original| Lbs. per | Specific | Lbs. per |Attenuation,|
|Gravity |Barrel of | Gravity |Barrel of |or Saccharum|
|of the |Saccharine|of the Ale.|Saccharine| decomposed.|
| Worts. | Matter. | | Matter. | |
+--------+----------+-----------+----------+------------+
| 1·0950 | 88·75 | 1·0500 | 40·25 | 0·478 |
| 1·0918 | 85·62 | 1·0420 | 38·42 | 0·552 |
| 1·0829 | 78·125 | 1·0205 | 16·87 | 0·787 |
| 1·0862 | 80·625 | 1·0236 | 20·00 | 0·757 |
| 1·0780 | 73·75 | 1·0280 | 24·25 | 0·698 |
| 1·0700 | 65·00 | 1·0285 | 25·00 | 0·615 |
| 1·1002 | 93·75 | 1·0400 | 36·25 | 0·613 |
| 1·1025 | 95·93 | 1·0420 | 38·42 | 0·600 |
| 1·0978 | 91·56 | 1·0307 | 27·00 | 0·705 |
| 1·0956 | 89·37 | 1·0358 | 32·19 | 0·640 |
| 1·1130 | 105·82 | 1·0352 | 31·87 | 0·661 |
| 1·1092 | 102·187 | 1·0302 | 26·75 | 0·605 |
| 1·1171 | 110·00 | 1·0400 | 36·25 | 0·669 |
| 1·1030 | 96·40 | 1·0271 | 23·42 | 0·757 |
| 1·0660 | 61·25 | 1·0214 | 17·80 | 0·709 |
+--------+----------+-----------+----------+------------+
The second column here does not represent, I believe, the solid extract,
but the pasty extract obtained as the basis of Mr. Allen’s
saccharometer, and therefore each of its numbers is somewhat too high.
The last column, also, must be in some measure erroneous, on account of
the quantity of alcohol dissipated during the process of fermentation.
It must be likewise incorrect, because the density due to the saccharine
matter will be partly counteracted, by the effect of the alcohol present
in the fermented liquor. In fact, the attenuation does not correspond to
the strength of the wort; being greatest in the third brewing, and
smallest in the first. The quantity of yeast for the above ale brewings
in the table was, upon an average, one gallon for 108 gallons; but it
varied with its quality, and with the state of the weather, which, when
warm, permits much less to be used with propriety.
The good quality of the malt, and the right management of the mashing,
may be tested by the quantity of saccharine matter contained in the
successively drawn worts. With this view, an aliquot portion of each of
them should be evaporated by a safety-bath heat to a nearly concrete
consistence, and then mixed with twice its volume of strong spirit of
wine. The truly saccharine substance will be dissolved, while the starch
and other matters will be separated; after which the proportions of each
may be determined by filtration and evaporation. Or an equally correct,
and much more expeditious, method of arriving at the same result would
be, after agitating the viscid extract with the alcohol in a tall glass
cylinder, to allow the insoluble fecula to subside, and then to
determine the specific gravity of the supernatant liquid by a
hydrometer. The additional density which the alcohol has acquired will
indicate the quantity of malt sugar which it has received. The following
table, constructed by me, at the request of Henry Warburton, Esq., M.
P., chairman of the Molasses Committee of the House of Commons in 1830,
will show the brewer the principle of this important inquiry. It
exhibits the quantity in grains weight of sugar requisite to raise the
specific gravity of a gallon of spirit of different densities to the
gravity of water = 1·000.
Specific Gravity of Grains, Weight of Sugar in the
Spirit. Gallon Imperial.
0·995 0·980
0·990 1·890
0·985 2·800
0·980 3·710
0·975 4·690
0·970 5·600
0·965 6·650
0·960 7·070
0·955 8·400
0·950 9·310
The immediate purpose of this table was to show the effect of saccharine
matter in disguising the presence or amount of alcohol in the weak
feints of the distiller. But a similar table might easily be
constructed, in which, taking a uniform quantity of alcohol of 0·825,
for example, the quantity of sugar in any wort-extract would be shown by
the increase of specific gravity which the alcohol received from
agitation with a certain weight of the wort, inspissated to a nearly
solid consistence by a safety-pan, made on the principle of my patent
sugar-pan. (See SUGAR.) Thus, the normal quantities being 1000 grain
measures of alcohol, and 100 grains by weight of inspissated
mash-extract, the hydrometer would at once indicate, by help of the
table, first, the quantity per cent. of truly saccharine matter, and
next, by subtraction, that of farinaceous matter present in it.
[Illustration: 103]
_Plan, Machinery, and Utensils of a great Brewery._--_Figs._ 103. and
104. represent the arrangement of the utensils and machinery in a porter
brewery on the largest scale; in which, however, it must be observed
that the elevation _fig._ 103. is in a great degree imaginary as to the
plane upon which it is taken; but the different vessels are arranged so
as to explain their uses most readily, and at the same time to
preserve, as nearly as possible, the relative positions which are
usually assigned to each in works of this nature.
The malt for the supply of the brewery is stored in vast granaries or
malt-lofts, usually situated in the upper part of the buildings. Of
these, I have been able to represent only one, at A, _fig._ 103.: the
others, which are supposed to be on each side of it, cannot be seen in
this view. Immediately beneath the granary A, on the ground floor, is
the mill; in the upper story above it, are two pairs of rollers, _fig._
101, 102, and 103, under _a_, _a_, for bruising or crushing the grains
of the malt. In the floor beneath the rollers are the mill-stones _b_,
_b_, where the malt is sometimes ground, instead of being merely bruised
by passing between the rollers, under _a_, _a_.
The malt, when prepared, is conveyed by a trough into a chest _d_, to
the right of _b_, from which it can be elevated by the action of a
spiral screw, _fig._ 105., enclosed in the sloping tube _e_, into the
large chest or binn B, for holding ground malt, situated immediately
over the mash-tun D. The malt is reserved in this binn till wanted, and
it is then let down into the mashing-tun, where the extract is obtained
by hot water supplied from the copper G, seen to the right of B.
The water for the service of the brewery is obtained from the well E,
seen beneath the mill to the left, by a lifting pump worked by the steam
engine; and the forcing-pipe _f_ of this pump conveys the water up to
the large reservoir or water-back F, placed at the top of the
engine-house. From this cistern, iron pipes are laid to the copper G (on
the right-hand side of the figure), as also to every part of the
establishment where cold water can be wanted for cleaning and washing
the vessels. The copper G can be filled with cold water by merely
turning a cock; and the water, when boiled therein, is conveyed by the
pipe _g_ into the bottom of the mash-tun D. It is introduced beneath a
false bottom, upon which the malt lies, and, rising up through the holes
in the false bottom, it extracts the saccharine matter from the malt; a
greater or less time being allowed for the infusion, according to
circumstances. The instant the water is drawn off from the copper, fresh
water must be let into it, in order to be ready for boiling the second
mashing; because the copper must not be left empty for a moment,
otherwise the intense heat of the fire would destroy its bottom. For the
convenience of thus letting down at once as much liquor as will fill the
lower part of the copper, a pan or second boiler is placed over the top
of the copper, as seen in _fig._ 103.; and the steam rising from the
copper communicates a considerable degree of heat to the contents of the
pan, without any expense of fuel. This will be more minutely explained
hereafter. (_See fig._ 107.)
During the process of mashing, the malt is agitated in the mash-tun, so
as to expose every part to the action of the water. This is done by a
mechanism contained within the mash-tun, which is put in motion by a
horizontal shaft above it, H, leading from the mill. The mash machine is
shown separately in _fig._ 106. When the operation of mashing is
finished, the wort or extract is drained down from the malt into the
vessel I, called the _under-back_, immediately below the mash-tun, of
like dimensions, and situated always on a lower level, for which reason
it has received this name. Here the wort does not remain longer than is
necessary to drain off the whole of it from the tun above. It is then
pumped up by the three-barrelled pump _k_, into the pan upon the top of
the copper, by a pipe which cannot be seen in this section. The wort
remains in the pan until the water for the succeeding mashes is
discharged from the copper. But this delay is no loss of time, because
the heat of the copper, and the steam arising from it, prepare the wort,
which had become cooler, for boiling. The instant the copper is emptied,
the first wort is let down from the pan into the copper, and the second
wort is pumped up from the under-back into the upper pan. The proper
proportion of hops is thrown into the copper through the near hole, and
then the door is shut down, and screwed fast, to keep in the steam, and
cause it to rise up through pipes into the pan. It is thus forced to
blow up through the wort in the pan, and communicates so much heat to
it, or water, called _liquor_ by the brewers, that either is brought
near to the boiling point. The different worts succeed each other
through all the different vessels with the greatest regularity, so that
there is no loss of time, but every part of the apparatus is constantly
employed. When the ebullition has continued a sufficient period to
coagulate the grosser part of the extract, and to evaporate part of the
water, the contents of the copper are run off through a large cock into
the _jack-back_ K, below G, which is a vessel of sufficient dimensions
to contain it, and provided with a bottom of cast-iron plates,
perforated with small holes, through which the wort drains and leaves
the hops. The hot wort is drawn off from the jack-back through the pipe
_h_ by the three-barrelled pump, which throws it up to the coolers L, L,
L; this pump being made with different pipes and cocks of communication,
to serve all the purposes of the brewery except that of raising the cold
water from the well. The coolers L, L, L, are very shallow vessels,
built over one another in several stages: and that part of the building
in which they are contained is built with lattice-work or or shutter
flaps, on all sides, to admit free currents of air. When the wort is
sufficiently cooled to be put to the first fermentation, it is conducted
in pipes from all the different coolers to the large fermenting vessel
or gyle-tun M, which, with another similar vessel behind it, is of
sufficient capacity to contain all the beer of one day’s brewings.
Whenever the first fermentation is concluded, the beer is drawn off from
the great fermenting vessel M, into the small fermenting casks or
cleansing vessels N, of which there are a great number in the brewery.
They are placed four together, and to each four a common spout is
provided to carry off the yeast, and conduct it into the troughs _n_,
placed beneath. In these cleansing vessels the beer remains till the
fermentation is completed; and it is then put into the store-vats, which
are casks or tuns of an immense size, where it is kept till wanted, and
is finally drawn off into barrels, and sent away from the brewery. The
store-vats are not represented in the figure: they are of a conical
shape, and of different dimensions, from fifteen to twenty feet
diameter, and usually from fifteen to twenty feet in depth. The
steam-engine which puts all the machine in motion is exhibited in its
place, on the left side of the figure. On the axis of the large
fly-wheel is a bevelled spur-wheel, which turns another similar wheel
upon the end of a horizontal shaft, which extends from the engine-house
to the great horse-wheel, set in motion by means of a spur-wheel. The
horse-wheel drives all the pinions for the mill-stones _b_, _b_, and
also the horizontal axis which works the three-barrelled pump _k_. The
rollers _a_, _a_, are turned by a bevel wheel upon the upper end of the
axis of the horse-wheel, which is prolonged for that purpose; and the
horizontal shaft H, for the mashing engine, is driven by a pair of bevel
wheels. There is likewise a sack-tackle, which is not represented. It is
a machine for drawing up the sacks of malt from the court-yard to the
highest part of the building, whence the sacks are wheeled on a truck to
the malt-loft A, and the contents of the sacks are discharged.
The horse-wheel is intended to be driven by horses occasionally, if the
steam-engine should fail; but these engines are now brought to such
perfection that it is very seldom any recourse of this kind is needed.
[Illustration: 104]
_Fig._ 104. is a representation of the _fermenting house_ at the brewery
of Messrs. Whitbread and Company, Chiswell Street, London, which is one
of the most complete in its arrangement in the world: it was erected
after the plan of Mr. Richardson, who conducts the brewing at those
works. The whole of _fig._ 104. is to be considered as devoted to the
same object as the large vessel M and the casks N, _fig._ 103. In _fig._
104., _r r_ is the pipe which leads from the different coolers to convey
the wort to the great fermenting vessels or squares M, of which there
are two, one behind the other; _f f_ represents a part of the great pipe
which conveys all the water from the well E, _fig._ 103, up to the water
cistern F. This pipe is conducted purposely up the wall of the
fermenting-house, _fig._ 104, and has a cock in it, near _r_, to stop
the passage. Just beneath this passage a branch-pipe _p_ proceeds, and
enters a large pipe _x x_, which has the former pipe _r_ withinside of
it. From the end of the pipe _x_, nearest to the squares M, another
branch _n n_ proceeds, and returns to the original pipe _f_, with a cock
to regulate it. The object of this arrangement is to make all, or any
part, of the cold water flow through the pipe _x x_, which surrounds the
pipe _r_, formed only of thin copper, and thus cool the wort passing
through the pipe _r_, until it is found by the thermometer to have the
exact temperature which is desirable before it is put to ferment in the
great square M. By means of the cocks at _n_ and _p_, the quantity of
cold water passing over the surface of the pipe _r_ can be regulated at
pleasure, whereby the heat of the wort, when it enters into the square,
may be adjusted within half a degree.
When the first fermentation in the squares M M is finished, the beer is
drawn off from them by pipes marked _c_, and conducted by its branches W
W W, to the different rows of fermenting-tuns, marked N N, which occupy
the greater part of the building. In the hollow between every two rows
are placed large troughs, to contain the yeast which they throw off. The
figure shows that the small tuns are all placed on a lower level than
the bottom of the great vessels M, so that the beer will flow into them,
and, by hydrostatic equilibrium, will fill them to the same level. When
they are filled, the communication-cock is shut; but, as the working off
the yeast diminishes the quantity of beer in each vessel, it is
necessary to replenish them from time to time. For this purpose, the two
large vats O O are filled from the great squares M M, before any beer is
drawn off into the small casks N, and this quantity of beer is reserved
at the higher level for filling up. The two vessels O O are, in reality,
situated between the two squares M M; but I have been obliged to place
them thus in the section, in order that they may be seen. Near each
filling-up tun O is a small cistern _t_ communicating with the tun O by
a pipe, which is closed by a float-valve. The small cisterns _t_ are
always in communication with the pipes which lead to the small
fermenting vessels N; and therefore the surface of the beer in all the
tuns, and in the cisterns, will always be at the same level; and as this
level subsides by the working off of the yeast from the tuns, the float
sinks and opens the valve, so as to admit a sufficiency of beer from the
filling-up tuns O, to restore the surfaces of the beer in all the tuns,
and also in the cistern _t_, to the original level. In order to carry
off the yeast which is produced by the fermentation of the beer in the
tuns O O, a conical iron dish or funnel is made to float upon the
surface of the beer which they contain; and from the centre of this
funnel a pipe, _o_, descends, and passes through the bottom of the tun,
being packed with a collar of leather, so as to be water-tight; at the
same time that it is at liberty to slide down, as the surface of the
beer descends in the tun. The yeast flows over the edge of this
funnel-shaped dish, and is conveyed down the pipe to a trough beneath.
Beneath the fermenting-house are large arched vaults, P, built with
stone, and lined with stucco. Into these the beer is let down in casks
when sufficiently fermented, and is kept in store till wanted. These
vaults are used at Mr. Whitbread’s brewery, instead of the great
store-vats of which we have before spoken, and are in some respects
preferable, because they preserve a great equality of temperature, being
beneath the surface of the earth.
The malt-rollers, or machines for bruising the grains of the malt,
_fig._ 101. 102., have been already described. The malt is shot down
from A, _fig._ 103., the malt-loft, into the hopper; and from this it is
let out gradually through a sluice or sliding shuttle, _a_, _fig._ 103.
and falls between the rollers.
[Illustration: 105]
_Fig._ 105. is the screw by which the ground or bruised malt is raised
up, or conveyed from one part of the brewery to another. K is an
inclined box or trough, in the centre of which the axis of the screw H
is placed; the spiral iron plate or worm, which is fixed projecting from
the axis, and which forms the screw, is made very nearly to fill the
inside of the box. By this means, when the screw is turned round by the
wheels E F, or by any other means, it raises up the malt from the box
_d_, and delivers it at the spout G.
This screw is equally applicable for conveying the malt horizontally in
the trough K, as slantingly; and similar machines are employed in
various parts of breweries for conveying the malt wherever the situation
of the works require.
[Illustration: 106]
_Fig._ 106. is the mashing-machine. _a a_ is the tun, made of wood
staves, hooped together. In the centre of it rises a perpendicular
shaft, _b_, which is turned slowly round by means of the bevelled wheels
_t u_ at the top. _c c_ are two arms, projecting from that axis, and
supporting the short vertical axis _d_ of the spur-wheel _x_, which is
turned by the spur-wheel _w_; so that, when the central axis _b_ is made
to revolve, it will carry the thick short axle _d_ round the tun in a
circle. That axle _d_ is furnished with a number of arms, _e e_, which
have blades placed obliquely to the plane of their motion. When the
axis is turned round, these arms agitate the malt in the tun, and give
it a constant tendency to rise upwards from the bottom.
The motion of the axle _d_ is produced by a wheel, _x_, on the upper end
of it, which is turned by a wheel, _w_, fastened on the middle of the
tube _b_, which turns freely round upon its central axis. Upon a higher
point of the same tube _b_ is a bevel wheel, _o_, receiving motion from
a bevel wheel, _q_, fixed upon the end of the horizontal axis _n n_,
which gives motion to the whole machine. This same axis has a pinion,
_p_, upon it, which gives motion to the wheel _r_, fixed near the middle
of a horizontal axle, which, at its left hand end, has a bevel pinion,
_t_, working the wheel _u_, before mentioned. By these means, the
rotation of the central axis _b_ will be very slow compared with the
motion of the axle _d_; for the latter will make seventeen or eighteen
revolutions on its own axis in the same space of time that it will be
carried once round the tun by the motion of the shaft _b_. At the
beginning of the operation of mashing, the machine is made to turn with
a slow motion; but, after having wetted all the malt by one revolution,
it is driven quicker. For this purpose, the ascending-shaft _f g_, which
gives motion to the machine, has two bevel wheels, _h i_, fixed upon a
tube, _f g_, which is fitted upon a central shaft. These wheels actuate
the wheels _m_ and _o_, upon the end of the horizontal shaft _n n_; but
the distance between the two wheels _h_ and _i_ is such, that they
cannot be engaged both at once with the wheels _m_ and _o_; but the tube
_f g_, to which they are fixed, is capable of sliding up and down on its
central axis sufficiently to bring either wheel _h_ or _i_ into geer
with its corresponding wheel _o_ or _m_, upon the horizontal shaft; and
as the diameters of _n o_, and _i m_, are of very different proportions,
the velocity of the motion of the machine can be varied at pleasure, by
using one or other. _k_ and _k_ are two levers, which are forked at
their extremities, and embrace collars at the ends of the tube _f g_.
These levers being united by a rod, _l_, the handle _k_ gives the means
of moving the tube _f g_, and its wheels _h i_, up or down, to throw
either the one or the other wheel into geer.
The object of boiling the wort is not merely evaporation and
concentration, but extraction, coagulation, and, finally, combination
with the hops; purposes which are better accomplished in a deep confined
copper, by a moderate heat, than in an open shallow pan with a quick
fire. The copper being encased above in brickwork, retains its digesting
temperature much longer than the pan could do. The waste steam of the
close kettle, moreover, can be economically employed in communicating
heat to water or weak worts; whereas the exhalations from an open pan
would prove a nuisance, and would need to be carried off by a hood. The
boiling has a four-fold effect: 1. it concentrates the wort; 2. during
the earlier stages of heating, it converts the starch into sugar,
dextrine, and gum, by means of the diastase; 3. it extracts the
substance of the hops diffused through the wort; 4. it coagulates the
albuminous matter present in the grain, or precipitates it by means of
the tannin of the hops.
The degree of evaporation is regulated by the nature of the wort, and
the quality of the beer. Strong ale and stout for keeping, require more
boiling than ordinary porter or table-beer brewed for immediate use. The
proportion of the water carried off by evaporation is usually from a
seventh to a sixth of the volume. The hops are introduced during the
progress of the ebullition. They serve to give the beer not only a
bitter aromatic taste, but also a keeping quality, or they counteract
its natural tendency to become sour; an effect partly due to the
precipitation of the albumen and starch, by their resinous and tanning
constituents, and partly to the antifermentable properties of their
lupuline, bitter principle, ethereous oil, and resin. In these respects,
there is none of the bitter plants which can be substituted for hops
with advantage. For strong beer, powerful fresh hops should be selected;
for weaker beer, an older and weaker article will suffice.
The hops are either boiled with the whole body of the wort, or extracted
with a portion of it; and this concentrated extract added to the rest.
The stronger the hops are, the longer time they require for extraction
of their virtues; for strong hops, an hour and a half or two hours
boiling may be proper; for a weaker sort, half an hour or an hour may be
sufficient; but it is never advisable to push this process too far, lest
a disagreeable bitterness, without aroma, be imparted to the beer. In
our breweries, it is the practice to boil the hops with a part of the
wort, and to filter the decoction through a drainer, called the _jack
hop-back_. The proportion of hops to malt is very various; but, in
general, from a pound and a quarter to a pound and a half of the former
are taken for 100 lbs. of the latter in making good table-beer. For
porter and strong ale, 2 pounds of hops are used, or even more; for
instance, one pound of hops to a bushel of malt, if the beer be destined
for the consumption of India.
During the boiling of the two ingredients, much coagulated albuminous
matter, in various states of combination, makes its appearance in the
liquid, constituting what is called the _breaking or curdling of the
wort_, when numerous minute flocks are seen floating in it. The
resinous, bitter, and oily-ethereous principles of the hops combine with
the sugar and gum, or dextrine of the wort; but for this effect they
require time and heat; showing that the boil is not a process of mere
evaporation, but one of chemical reaction. A yellowish-green pellicle of
hop-oil and resin appears upon the surface of the boiling wort, in a
somewhat frothy form: when this disappears, the boiling is presumed to
be completed, and the beer is strained off into the cooler. The
residuary hops may be pressed and used for an inferior quality of beer;
or they may be boiled with fresh wort, and be added to the next brewing
charge.
_Figs._ 107, 108. represent the copper of a London brewery. _Fig._ 107.
is a vertical section; _fig._ 108., a ground-plan of the fire-grate and
flue, upon a smaller scale: _a_ is the close copper kettle, having its
bottom convex within; _b_ is the open pan placed upon its top. From the
upper part of the copper, a wide tube, _c_, ascends, to carry off the
steam generated during the ebullition of the wort, which is conducted
through four downwards-slanting tubes, _d d_ (two only are visible in
this section), into the liquor of the pan _b_, in order to warm its
contents. A vertical iron shaft or spindle, _e_, passes down through the
tube _c_, nearly to the bottom of the copper, and is there mounted with
an iron arm, called _a rouser_, which carries round a chain hung in
loops, to prevent the hops from adhering to the bottom of the boiler.
Three bent stays, _f_, are stretched across the interior, to support the
shaft by a collet at their middle junction. The shaft carries at its
upper end a bevel wheel, _g_, working into a bevel pinion upon the axis
_h_, which may be turned either by power or by hand. The _rouser_ shaft
may be lifted by means of the chain _i_, which, going over two pulleys,
has its end passed round the wheel and axle _k_, and is turned by a
winch: _l_ is a tube for conveying the waste steam into the chimney _m_.
[Illustration: 107 108]
The heat is applied as follows:--For heating the colossal coppers of the
London breweries, two separate fires are required, which are separated
by a narrow wall of brickwork, _n_, _fig._ 107, 108. The dotted circle
_a´ a´_ indicates the largest circumference of the copper, and _b´ b´_
its bottom; _o o_ are the grates upon which the coals are thrown, not
through folding doors (as of old), but through a short slanting iron
hopper, shown at _p_, _fig._ 107., built in the wall, and kept
constantly filled with the fuel, in order to exclude the air. Thus the
lower stratum of coals gets ignited before it reaches the grate. Above
the hopper _p_, a narrow channel is provided for the admission of
atmospherical air, in such quantity merely as may be requisite to
complete the combustion of the smoke of the coals. Behind each grate
there is a fire-bridge, _r_, which reflects the flame upwards, and
causes it to play upon the bottom of the copper. The burnt air then
passes round the copper in a semicircular flue, _s s_, from which it
flows off into the chimney _m_, on whose under end a sliding
damper-plate, _t_, is placed, for tempering the draught. When cold air
is admitted at this orifice, the combustion of the fuel is immediately
checked. There is, besides, another slide-plate at the entrance of the
slanting flue into the vertical chimney, for regulating the play of the
flame under and around the copper. If the plate _t_ be opened, and the
other plate shut, the power of the fire is suspended, as it ought to be,
at the time of emptying the copper. Immediately over the grate is a
brick arch, _u_, to protect the front edge of the copper from the first
impulsion of the flame. The chimney is supported upon iron pillars, _v
v_; _w_ is a cavity closed with a slide-plate, through which the ashes
may be taken out from behind, by means of a long iron hook.
[Illustration: 109]
_Fig._ 109. represents one of the sluice-cocks, which are used to make
the communications of the pipes with the pumps, or other parts of the
brewery. B B represents the pipe in which the cock is placed. The two
parts of this pipe are screwed to the side of a box, C C, in which a
slider, A, rises and falls, and intercepts, at pleasure, the passage of
the pipe. The slider is moved by the rod _a_. This passes through a
stuffing-box, in the top of the box which contains the slider, and has
the rack _b_ fastened to it. The rack is moved by a pinion fixed upon
the axis of a handle _e_, and the rack and pinion are contained in a
frame _d_ which is supported by two pillars. The frame contains a small
roller behind the rack, which bears it up towards the pinion, and keeps
its teeth up to the teeth of the pinion. The slider A is made to fit
accurately against the internal surface of the box C, and to bear
against this surface by the pressure of a spring, so as to make a
perfectly close fitting.
[Illustration: 110]
_Fig._ 110. is a small cock to be placed in the side of the great store
vats, for the purpose of drawing off a small quantity of beer, to taste
and try its quality. A is a part of the stave or thickness of the great
store vat; into this the tube B of the cock is fitted, and is held tight
in its place by a nut, _a a_, screwed on withinside. At the other end of
the tube B, a plug, _c_, is fitted, by grinding it into a cone, and it
is kept in by a screw. This plug has a hole up the centre of it, and
from this a hole proceeds sidewise, and corresponds with a hole made
through the side of the tube when the cock is open; but when the plug
_c_ is turned round, the hole will not coincide, and then the cock will
be shut. D is the handle or key of the cock, by which its plug is turned
to open or shut it: this handle is put up the bore of the tube (the
cover E being first unscrewed and removed), and the end of it is adapted
to fit the end of the plug of the cock. The handle has a tube or passage
bored up it, to convey the beer away from the cock when it is opened,
and from this the passage _f_, through the handle, leads, to draw the
beer into a glass or tumbler. The hole in the side of the plug is so
arranged, that, when the handle is turned into a perpendicular
direction, with the passage _f_ downwards, the cock will be open. The
intention of this contrivance is, that there shall be no considerable
projection beyond the surface of the tun; because it sometimes happens
that a great hoop of the tun breaks, and, falling down, its great weight
would strike out any cock which had a projection; and, if this happened
in the night, much beer might be lost before it was discovered. The cock
above described, being almost wholly withinside, and having scarcely any
projection beyond the outside surface of the tun, is secure from this
accident.
[Illustration: 111]
_Fig._ 111. is a small contrivance of a vent peg, to be screwed into the
head of a common cask when the beer is to be drawn off from it, and it
is necessary to admit some air to allow the beer to flow. A A represents
a portion of the head of the cask into which the tube B is screwed. The
top of this tube is surrounded by a small cup, from which project the
two small handles C C, by which the peg is turned round to screw it into
the cask. The cup round the other part of the tube, is filled with
water; into this a small cup, D, is inverted; in consequence, the air
can gain admission into the cask when the pressure within is so far
diminished, that the air will bubble up through the water, and enter
beneath the small cup D.
The most efficient substance for fining beer hitherto discovered is
isinglass, which is prepared by solution in vinegar or old stale beer,
and this solution is afterwards reduced with thin mild beer generally
brewed for the purpose, in all large establishments, from a raw or
return wort. It must next be passed through a fine hair sieve, by means
of rubbing it down with a hard hair-brush, and brought to the proper
consistency by thin mild beer. If properly made, it will be clear,
transparent, and free from feculencies. Finings serve excellently to
remove any extraneous matter that may be found floating in the beer, and
thus changes it from bright to brilliant. The common quantity used is
from a pint to a quart per barrel, according to the nature of the beer.
To ascertain whether the beer is in a fit state for fining, put it into
a long glass cylindric vessel, and add to it a teaspoonful, or thereby,
of the fining; then give the mixture a good shake, by turning the vessel
up and down, after closing its mouth with the palm of the hand. If the
beer has been well brewed, its aptitude to become bright will be soon
shown by the mixture getting thick and curdy; a bright portion will
generally show itself at the bottom or middle; after which the finings
will gradually mount to the top, taking up all the impurities along with
them, till the whole becomes brilliant. Some have said that the finings
should carry the impurities down to the bottom; but this, according to
Mr. Black[8], takes place only with stubborn beer, which would not
become thoroughly bright with any quantity of finings which could be
introduced. Finings have usually a specific gravity of from 1·010 to
1·016, and, when added to beer in a fit condition for fining, invariably
go to the top, and not to the bottom. In fining beer in a barrel laid on
its side, if the finings do not make their appearance at the bung-hole,
the beer will not become bright. The isinglass must not be dissolved
with heat, nor in hot water.
[8] Treatise on Brewing, 8vo, p. 68.
Beer brewed from imperfectly malted grain, or from a mixture of malt and
raw corn, gives a fermentation quite different in flavour from that of
beer from sound malt. The nose is, in fact, the best guide to the
experienced brewer for ascertaining whether his process is going on well
or ill.
Ropiness is a morbid state of beer, which is best remedied, according to
Mr. Black, by putting the beer into a vat with a false bottom, and
adding, per barrel, 4 or 5 pounds of hops, taken gradually away after
the first boilings of the worts; and to them may be added about half a
pound per barrel of mustard-seed. Rouse the beer as the hops are
gradually introduced, and, in some months, the ropiness will be
perfectly cured. The beer should be drawn off from below the false
bottom.
For theoretical views, see FERMENTATION; and for wort-cooling apparatus,
see REFRIGERATOR.
BEET-ROOT SUGAR. See SUGAR.
BELL-METAL, an alloy of copper and tin. See COPPER.
BELLOWS. See METALLURGY.
BEN OIL. See OIL OF BEN.
BENGAL STRIPES. Ginghams; a kind of cotton cloth woven with coloured
stripes.
BENJAMIN or BENZOIN. (_Benjoin_, Fr.; _Benzöe_, Germ.) A species of
resin used chiefly in perfumery. It is extracted by incision from the
trunk and branches of the _styrax benzoin_, which grows in Java,
Sumatra, Santa Fé, and in the kingdom of Siam. The plant belongs to the
decandria monogynia of Linnæus, and the natural family of the ebenaceæ.
It hardens readily in the air, and comes to us in brittle masses, whose
fracture presents a mixture of red, brown, and white grains of various
sizes, which, when white, and of a certain shape, have been called
_amygdaloid_, from their resemblance to almonds. The _sorted_ benzoin
is, on the other hand, very impure.
The fracture of benzoin is conchoidal, and its lustre greasy: its
specific gravity varies from 1·063 to 1·092. It has an agreeable smell,
somewhat like vanilla, which is most manifest when it is ground. It
enters into fusion at a gentle heat, and then exhales a white smoke,
which may be condensed into the acicular crystals of benzoic acid, of
which it contains 18 parts in the hundred. Stoltze recommends the
following process for extracting the acid. The resin is to be dissolved
in 3 parts of alcohol, the solution is to be introduced into a retort,
and a solution of carbonate of soda dissolved in dilute alcohol is to be
gradually added to it, till the free acid be neutralised; and then a
bulk of water equal to double the weight of the benzoin is to be poured
in. The alcohol being drawn off by distillation, the remaining liquor
contains the acid, and the resin floating upon it may be skimmed off and
washed, when its weight will be found to amount to about 80 per cent. of
the raw material. The benzoin contains traces of a volatile oil, and a
substance soluble in water, at least through the agency of carbonate of
potash. Ether does not dissolve benzoin completely. The fat and volatile
oils dissolve very little of it.
Unverdorben has found in benzoin, besides benzoic acid, and a little
volatile oil, no less than three different kinds of resin, none of which
has, however, been turned as yet to any use in the arts.
Benzoin is of great use in perfumery, as it enters into a number of
preparations; among which may be mentioned fumigating pastilles,
fumigating cloves (called also nails), _poudre à la maréchale_, &c. The
alcoholic tincture, mixed with water, forms _virginal_ milk. Benzoin
enters also into the composition of certain varnishes employed for
snuff-boxes and walkingsticks, in order to give these objects an
agreeable smell when they become heated in the hand. It is likewise
added to the spirituous solution of isinglass with which the best court
plaster is made.
BERLIN BLUE. Prussian blue. See BLUE.
BERRIES OF AVIGNON, _and Persian Berries_. (_Graines d’Avignon_, Fr.;
_Gelbbeeren_, Germ.) A yellowish dye-drug, the fruit of the _rhamnus
infectorius_, a plant cultivated in Provence, Languedoc, and Dauphiné,
for the sake of its berries, which are plucked before they are ripe,
while they have a greenish hue. Another variety comes from Persia,
whence its trivial name; it is larger than the French kind, and has
superior properties. The principal substances contained in these berries
are: 1. A colouring matter, which is united with a matter insoluble in
ether, little soluble in concentrated alcohol, and very soluble in
water: it appears to be volatile. 2. A matter remarkable for its
bitterness, which is soluble in water and alcohol. 3. A third principle,
in small quantity. A decoction of one part of the Avignon or Persian
berry in ten of water affords a brown-yellow liquor bordering upon
green, having the smell of a vegetable extract, and a slightly bitter
taste.
With gelatine that decoction gives, after some time, a slight
precipitate,--
With alkalies a yellow hue,
-- acids a slight muddiness,
-- lime-water a greenish-yellow tint,
-- alum a yellow colour,
-- red sulphate of iron an olive-green colour,
-- sulphate of copper an olive colour,
-- proto-muriate of tin a greenish yellow with a slight
precipitate. (See CALICO PRINTING.)
BERYL. A beautiful mineral or gem, of moderate price, usually of a green
colour of various shades, passing into honey-yellow and sky blue.
BEZOAR. The name of certain concretions found in the stomachs of
animals, to which many fanciful virtues were formerly ascribed. They are
interesting only to the chemical pathologist.
BILE. (_Bile_, Fr.; _Galle_, Germ.) The secreted liquor of the liver in
animals. For an account of the uses of animal bile in the arts, see
GALL.
BIRDLIME. (_Glu_, Fr.; _Vogelleim_, Germ.) The best birdlime may be made
from the middle bark of the holly, boiled seven or eight hours in water,
till it is soft and tender, then laid by heaps in pits under ground,
covered with stones after the water is drained from it. There it must be
left during two or three weeks, to ferment in the summer season, and
watered, if necessary, till it passes into a mucilaginous state. It is
then to be pounded in a mortar to a paste, washed in running water, and
kneaded till it be free from extraneous matters. It is next left for
four or five days in earthen vessels to ferment and purify itself, when
it is fit for use. Birdlime may be made by the same process from the
mistletoe (_viburnum lantana_), young shoots of elder, and the barks of
other vegetables, as well as from most parasite plants.
Good birdlime is of a greenish colour, and sour flavour, somewhat
resembling that of linseed oil; gluey, stringy, and tenacious. By drying
in the air it becomes brittle, and may be powdered; but its viscosity
may be restored by moistening it. It has an acid reaction with litmus
paper. It contains resin, mucilage, a little free acid, colouring and
extractive matter. The resin has been called VISCINE.
BISMUTH. (_Bismuth_, Fr.; _Wismuth_, Germ.) Called also marcasite and
tin-glass. It was shown to be a metal somewhat different from lead, by
G. Agricola, in 1546; Stahl and Dufay proved its peculiarity; but it was
more minutely distinguished by Pott and Geoffroy, about the middle of
the last century. It is a rare substance, occurring native, as an oxide,
under the name of bismuth ochre; as a sulphuret, called bismuth glance;
as a sulphuret with copper, called copper bismuth ore; as also with
copper and lead, called needle ore. It is found associated likewise with
selenium and tellurium. The native metal occurs in various forms and
colours, as white, reddish, and variegated; in primitive and floetz
formations, along with the ores of cobalt, nickel, copper, silver, and
bismuth ochre; at the Saxon Erzgebirge, near Schneeberg, and Joh.
Georgenstadt; also in Bohemia, Baden, Wurtemberg, Hessia, Sweden,
Norway, England, and France.
The production of this metal is but a limited object of the
smelting-works of the Saxon Erzgebirge at Schneeberg. It there occurs,
mixed with cobalt speiss, in the proportion of about 7 per cent. upon
the average, and is procured by means of a peculiar furnace of
liquation, which is the most economical method, both as to saving fuel,
and oxidisement of the bismuth.
[Illustration: 112 113 114]
The bismuth eliquation furnace at Schneeberg is represented in _figs._
112, 113, and 114., of which the first is a view from above, the second
a view in front, and the third a transverse section in the dotted line A
B of _fig._ 112. _a_ is the ash-pit; _b_, the fireplace; _c_, the
eliquation pipes; _d_, the grate of masonry or brickwork, upon which the
fuel is thrown through the fire-door _e e_. The anterior deeper lying
orifice of the eliquation pipes is closed with the clay-plate _f_; which
has beneath a small circular groove, through which the liquefied metal
flows off. _g_ is a wall extending from the hearth-sole nearly to the
anterior orifices of the eliquation pipes, in which wall there are as
many fire-holes, _h_, as there are pipes in the furnace; _i_ are iron
pans, which receive the fluid metal; _h_, a wooden water-trough, in
which the bismuth is granulated and cooled; _l_, the posterior and
higher lying apertures of the eliquation pipes, shut merely with a
sheet-iron cover. The granulations of bismuth drained from the posterior
openings fall upon the flat surfaces _m_, and then into the
water-trough. _n n_ are draught-holes in the vault between the two
pipes, which serve for increasing or diminishing the heat at pleasure.
The ores to be eliquated (sweated) are sorted by hand from the gangue,
broken into pieces about the size of a hazel nut, and introduced into
the ignited pipes; one charge consisting of about 1/2 cwt.; so that the
pipes are filled to half their diameter, and three fourths of their
length. The sheet-iron door is shut, and the fire strongly urged,
whereby the bismuth begins to flow in ten minutes, and falls through the
holes in the clay-plates into hot pans containing some coal-dust.
Whenever it runs slowly, the ore is stirred round in the pipes, at
intervals during half an hour, in which time the liquation is usually
finished. The residuum, called bismuth barley (_graupen_), is scooped
out with iron rakes into a water trough; the pipes are charged afresh;
the pans, when full, have their contents cast into moulds, forming bars
of from 25 to 50 pounds weight. About 20 cwt. of ore are smelted in 8
hours, with a consumption of 63 Leipzic cubic feet of wood. The total
production of Schneeberg, in 1830, was 9800 lbs. The bismuth thus
procured by liquation upon the great scale, contains no small admixture
of arsenic, iron, and some other metals, from which it may be freed by
solution in nitric acid, precipitation by water, and reduction of the
subnitrated oxide by black flux. By exposing the crude bismuth for some
time to a dull red heat, under charcoal, arsenic is expelled.
Bismuth is white, and resembles antimony, but has a reddish tint;
whereas the latter metal has a bluish cast. It is brilliant,
crystallises readily in small cubical facets, is very brittle, and may
be easily reduced to powder. Its specific gravity is 9·83; and by
hammering it with care, the density may be increased to 9·8827. It melts
at 480° Fahr., and may be cooled 6 or 7 degrees below this point without
fixing; but the moment it begins to solidify, the temperature rises to
480°, and continues stationary till the whole mass is congealed. When
heated from 32° to 212°, it expands 1/710 in length. When pure it
affords a very valuable means of adjusting the scale of high-ranged
thermometers. At strong heats bismuth volatilises, may be distilled in
close vessels, and is thus obtained in crystalline laminæ.
The alloy of bismuth and lead in equal parts has a density of 10·709,
being greater than the mean of the constituents; it has a foliated
texture, is brittle, and of the same colour as bismuth. Bismuth, with
tin, forms a compound more elastic and sonorous than the tin itself, and
is therefore frequently added to it by the pewterers. With 1 of bismuth
and 24 of tin, the alloy is somewhat malleable; with more bismuth, it is
brittle. When much bismuth is present, it may be easily parted by strong
muriatic acid, which dissolves the tin, and leaves the bismuth in a
black powder. It has been said, that an alloy of tin, bismuth, nickel,
and silver, hinders iron from rusting. (_Erdmann’s Journal._) The alloy
of bismuth with tin and lead was first examined by Sir I. Newton, and
has been called ever since fusible metal. Eight parts of bismuth, 5 of
lead, and 3 of tin, melt at the moderate temperature of 202° F.; but 2
of bismuth, 1 of lead, and 1 of tin, melt at 200·75° F. according to
Rose. A small addition of mercury of course aids the fusibility. Such
alloys serve to take casts of anatomical preparations. An alloy of 1
bismuth, 2 tin, and 1 lead, is employed as a soft solder by the
pewterers; and the same has been proposed as a bath for tempering steel
instruments. Cake-moulds, for the manufacturers of toilet soaps are made
of the same metal; as also excellent clichés for stereotype, of 3 lead,
2 tin, and 5 bismuth; an alloy which melts at 199° F. This compound
should be allowed to cool upon a piece of pasteboard, till it becomes of
a doughy consistence, before it is applied to the mould, to receive the
impress of the stamp.
The employment of plates of fusible metal as safety _rondelles_, to
apertures in the tops of steam boilers has been proposed in France,
because they would melt and give way at elevations of temperature under
those which would endanger the bursting of the vessel; the fusibility of
the alloy being proportioned to the quality of steam required for the
engine. It has been found, however, that boilers, apparently secured in
this way, burst, while the safety discs remained entire; the expansive
force of the steam causing explosion so suddenly, that the fusible alloy
had not time to melt or give way.
There are two, perhaps three, oxides of bismuth; the first and the
third, or the suboxide and super-oxide, are merely objects of chemical
curiosity. The oxide proper occurs native, and may be readily formed by
exposing the metal to a red-white heat in a muffle, when it takes fire,
burns with a faint blue flame, and sends off fumes which condense into a
yellow pulverulent oxide. But an easier process than that now mentioned
is to dissolve the bismuth in nitric acid, precipitate with water, and
expose the precipitate to a red heat. The oxide thus obtained has a
straw yellow colour, and fuses at a high heat into an opaque glass of a
dark-brown or black colour; but which becomes less opaque and yellow
after it has cooled. Its specific gravity is so high as 8·211. It
consists of 89·87 of metal and 10·13 oxygen in 100 parts. The above
precipitate, which is a sub-nitrate of bismuth, is called _pearl-white_,
and is employed as a flux for certain enamels; as it augments their
fusibility without imparting any colour to them. Hence, it is used
sometimes as a vehicle of the colours of other metallic oxides. When
well washed, it is employed in gilding porcelain; being added in the
proportion of one fifteenth to the gold. But pearl-white is most used by
ladies, as a cosmetic for giving a brilliant tint to a faded complexion.
It is called _blanc de fard_, by the French. If it contains, as bismuth
often does, a little silver, it becomes grey or dingy coloured on
exposure to light. When the oxide is prepared, by dropping the nitric
solution into an alkaline lye in excess, if this precipitate is well
washed and dried, it forms an excellent medicine; and is given, mixed
with gum tragacanth, for the relief of cardialgia, or burning and
spasmodic pains of the stomach.
Another sort of pearl-powder is prepared by adding a very dilute
solution of common salt to the above nitric solution of bismuth, whereby
a pulverulent sub-chloride of the metal is obtained in a light
flocculent form. A similar powder of a mother-of-pearl aspect may be
formed by dropping dilute muriatic acid into the solution of nitrate of
bismuth. The arsenic always present in the bismuth of commerce is
converted by nitric acid into arsenic acid, which, forming an insoluble
arseniate of bismuth, separates from the solution, unless there be such
an excess of nitric acid as to re-dissolve it. Hence the medicinal
oxide, prepared from a rightly-made nitrate, can contain no arsenic. If
we write with a pen dipped in that solution, the dry invisible traces
will become legible on plunging the paper in water.
It has been proposed to substitute bismuth for lead in assaying silver,
as a smaller quantity of it answers the purpose, and, as its oxide is
more fluent, can therefore penetrate the cupel more readily, and give a
more rapid result. But, independently of the objection from its high
price, bismuth has the disadvantage of boiling up, as well as of
_rocking_ or vegetating, with the silver, when the cupellation requires
a high heat. In extracting the silver from the galena found in the
copper-mine of Yahlun, it has happened sometimes that the silver
concreted towards the end of the operation, and produced a cauliflower
excrescence, which had to be cupelled again with a fresh dose of lead.
It was observed that, in this case, a portion of the silver had passed
into the cupel. Berzelius detected in a sample of silver thus concreted
the presence of bismuth.
The nitrate of bismuth, mixed with solution of tin and tartar, has been
employed as a mordant for dyeing lilac and violet in calico printing.
BISTRE. (_Bistre_, Fr. _bister_, Germ.) A brown colour which is used in
water colours, in the same way as China ink. It is prepared from
wood-soot, that of beech being preferred. The most compact and best
burned parcels of soot are collected from the chimney, pulverised, and
passed through a silk sieve. This powder is infused in pure water, and
stirred frequently with a glass ruler, then allowed to settle when the
water is decanted. If the salts are not all washed away, the process may
be repeated with warm water. The paste is now to be poured into a long
narrow vessel filled with water, stirred well, and left to settle for a
few minutes, in order to let the grosser parts subside. The supernatant
part is then to be poured off into a similar vessel. This process may be
repeated twice or thrice, to obtain a very good bistre. At last the
settled deposit is sufficiently fine, and, when freed from its
supernatant water, it is mixed with gum-water, moulded into proper
cakes, and dried. It is not used in oil painting, but has the same
effect in water-colours as brown pink has in oil.
BITUMEN, or ASPHALTUM. (_Bitume_, Fr. _Erdpech_, Germ.) A black
substance found in the earth, externally not dissimilar to pit-coal. It
is composed of carbon, hydrogen, and oxygen, like organic bodies; but
its origin is unknown. It has not been observed among the primitive or
older strata, but only in the secondary and alluvial formations. It
constitutes sometimes considerable beds, as in the isle of Trinidad,
where it occurs over an extensive district, in scattered masses. The
greater part of the asphaltum to be met with in commerce comes from the
Dead Sea, on whose shores it is cast up and gathered; whence it has got
the name of Jewish bitumen. In its black colour and fracture it
resembles ordinary pitch. By friction it affords negative electricity.
Its average density is 1·16. It melts at the temperature of boiling
water, kindles very readily at the flame, burns brightly with a thick
smoke, and leaves little ashes. Distilled by itself, it yields a
peculiar bituminous oil, very little water, some combustible gases, and
traces of ammonia. It leaves about one third of its weight of charcoal
after combustion, and ashes, containing silica, alumina, oxide of iron,
sometimes a little lime, and oxide of manganese. According to John,
asphaltum may be decomposed, by different solvents, into three distinct
substances. Water dissolves nothing; alcohol (anhydrous) dissolves out a
yellow resin equal to 5 per cent. of the weight of the asphaltum; that
resin is soluble in dilute alcohol and in ether. The portion not soluble
in the alcohol gives up a brown resin to ether, amounting to 70 per
cent. of the weight of the asphaltum. On evaporating off the ether, the
resin remains of a brownish-black colour, which dissolves readily in the
volatile oils and in the oil of petroleum. The portion of asphaltum
which does not dissolve in ether is very soluble in oil of turpentine,
and in oil of petroleum; but less so in oil of lavender. These three
resinous principles dissolve all together by digestion in the oils of
anise, rosemary, turpentine, olive, hemp-seed, nut, and linseed. Caustic
potash dissolves a notable quantity of asphaltum; but carbonate of
potash has no effect upon it.
Asphaltum enters into the composition of hydraulic cements, and into
that of black varnishes, called japans, for coating iron trays, &c. A
similar varnish may be prepared by dissolving 12 parts of fused amber, 2
parts of rosin, and 2 parts of asphaltum, in 6 parts of linseed oil
varnish, to which 12 parts of oil of turpentine have been added.
There is a kind of bitumen found at Aniches, in France, in the
department of the north, which is black, very fusible, and soft. It
burns with flame. Alcohol, ether, and oil of turpentine extract from it
a fatty substance, which may be saponified with alkalis.
The bitumen of Murindò, near Choco, in Columbia, is of a brownish-black
colour, soft, and has an earthy fracture. It has an acrid taste, burns
with a smell of vanilla, and is said to contain a large quantity of
benzoic acid. It appears to be the result of the decomposition of trees
containing benzoin.
Asphaltum occurs abundantly at the surface of the salt lake Asphaltites,
in Judea, produced from springs in the neighbourhood; it is floated
down, gathers consistence, and accumulates upon the surface of the lake;
the winds drive it on the shores, and the inhabitants collect it for
sale. Its inspissation diffuses a disagreeable smell in the air of that
region, which is supposed by the natives to be powerful enough to kill
birds when they attempt to fly across the lake.
But probably the most remarkable locality of asphaltum in the world is
the entire basin, or rather plain of it, in the island of Trinidad,
called the Tar Lake. It lies on the highest land in the island, and
emits a strong smell, sensible at ten miles’ distance. Its first
appearance is that of a lake of water, but, when viewed more nearly, it
seems to be a surface of glass. In hot weather its surface liquifies to
the depth of an inch, and it cannot then be walked upon. It is of a
circular form, about three miles in circumference, and of a depth not
ascertained. Large fissures frequently open and close up in it, whence
the pitch has been supposed to float upon a body of water. The soil, for
a considerable distance round it, consists of cinders and burnt earth,
and presents in many points indications of convulsions by subterranean
fire. In several parts of the neighbouring woods, there are round holes
and fissures in the ground, containing liquid bitumen to the depth of
two inches.
Mr. Hatchett examined some specimens from Trinidad, and concluded that
what had been heretofore supposed to be a pure mineral pitch was in
reality only a porous stone of the argillaceous kind, much impregnated
with bitumen.
These various bitumens belong exclusively to the secondary and tertiary
geological formations, and are not found among primitive rocks, except
very rarely in veins. They occur most generally in calcareous,
argillaceous, and sandy strata, and also in volcanic districts.
Petroleum frequently floats on the waters which issue from the volcanic
mountains, or which lie at their base; even the sea is at times covered
with it near the volcanic islands of Cape Verd. Mr. Breislak observed a
petroleum spring rising from the bottom of the sea near the southern
base of Vesuvius.
The substance with which bitumen seems to have the most constant and
most remarkable relations, is sea-salt; so that almost all the countries
most abundant in petroleum, as Italy, Transylvania, Persia, the environs
of Babylon, the region of the Dead Sea, &c., contain salt mines, or
lakes, or exhibit saline efflorescences. Iron pyrites is often
impregnated with petroleum, or contains a bituminous nucleus.
The origin of bitumen is as little known as that of most of the
productions of nature. Some regard it as an empyreumatic oil, a matter
analogous to liquid resin or essential oil, resulting from the
destruction of that astonishing multitude of animals and vegetables
buried in the earth, whose solid remains are daily brought to view in
mineral researches. It has been also supposed that naphtha and petroleum
are the product of coals decomposed either by the fire of volcanos, by
the subterranean combustion of coal itself, or by the decomposition of
pyrites. The latter opinion is not supported by any direct evidence, but
the two former are sufficiently probable.
_Elastic Bitumen_ is a rare substance, found hitherto only near
Castleton, in Derbyshire, in fissures of slaty clay.
_Bituminous mastic, or cement_, has been of late extensively employed in
France for covering roofs and terraces, and lining water cisterns. The
mineral bitumen used for the composition of this mastic is procured
chiefly from the _Obsann_ (Bas-Rhin), from the Parc (department de
l’Ain), and from the _Puy-de-la-Poix_ (department of Puy-de-Dome). But
boiled coal-tar answers equally well. In the neighbourhood of these
localities, there is a limestone impregnated with bitumen, which suits
for giving consistence to the cement. This is well dried, ground to
powder, sifted, and stirred while hot, in about one fifth its weight of
melted asphaltum, contained in a cast-iron boiler. Dry chalk or bricks,
ground and sifted, will suit equally well. As soon as this paste is made
quite homogeneous, it is lifted out with an iron shovel or spoon, and
spread in rectangular moulds, secured with pegs at the joints, fastened
to a kind of platform of smoothed planks, covered with strong
sheet-iron. The sides of these moulds should be previously smeared over
with a thin coat of loam-paste, to prevent their adhesion to the mastic.
Whenever the cake is cold, the frame is taken asunder, and it is removed
from the iron plate by an oblong shovel, or strong spatula of iron.
These cakes or bricks are usually 18 inches long, 12 broad, and 4 thick,
and weigh about 70 lbs.
BITTER PRINCIPLE. (_Amère_, Fr.; _Bitterstoff_, Germ.) This principle
has not been insulated hitherto by the chemist from the other proximate
principles of plants, but its existence is sufficiently recognised by
the taste. The following list contains the principal bitter substances,
many of which have been used in the arts and in medicine.
+--------------+-----------------+------------------+--------------+
|Name. |Part employed. |Country. |Observations. |
+--------------+-----------------+------------------+--------------+
|Quassia |Wood |Surinam, E. Indies|Powerfully |
| | | |bitter |
|Wormwood |Herb |Great Britain |Ditto |
|Aloe |Inspissated juice|South Africa |Ditto |
|Angustura |Bark |South America |Ditto |
|Orange |Unripe fruit |South of Europe } |Aromatic |
|Ditto |Peel |Ditto } |bitter |
|Acorus |Root |Ditto |Ditto |
|Carduus Bene- |Herb |Greek Archipelago | |
|dictus | | | |
|Cascarilla |Bark |Jamaica |Ditto |
|Centaury |Herb |Great Britain | |
|Camomile |Flowers | | |
|Colocynth |Fruit |Levant |Intolerably |
| | | |bitter |
|Colombo |Root |East Africa |Very bitter |
|Fumitory |Herb |Great Britain | |
|Gentiana lutea|Root |Switzerland |Very bitter |
|Ground Ivy |Herb |Great Britain | |
|Walnut |Peels | |With tannin |
|Island moss | | |With starch |
|Hops |Scales of the |Great Britain |Aromatic |
| |female flowers | |bitters |
|Milfoil |Herb flowers |Great Britain | |
|Large-leaved |Herb |Great Britain | |
|Satyrion | | | |
|Rhubarb |Root |China |Disagreeable |
| | | |odour |
|Rue |Herb |Great Britain |Bitter and |
| | | |sharp |
|Tansy |Herb flowers |Ditto |Bitter and |
| | | |offensive |
|Bitter trefoil|Herb |Ditto | |
|Simarouba |Bark |Guyana | |
|Bryony |Root |Great Britain |Sharp, bitter,|
| | | |nauseous |
|Coffee |Seeds |Arabia | |
+--------------+-----------------+------------------+--------------+
BLACK DYE. (_Teinte noire_, Fr. _Schwartze farbe_, Germ.) For 1 cwt. of
cloth, there are put into a boiler of middle size 18 lbs. of logwood,
with as much Aleppo galls in powder, and the whole, being enclosed in a
bag, is boiled in a sufficient quantity of water for 12 hours. One-third
of this bath is transferred into another boiler with two pounds of
verdigris; and the stuff is passed through this solution, stirring it
continually during two hours, taking care to keep the bath very hot
without boiling. The stuff is then lifted out, another third of the bath
is added to the boiler, along with eight pounds of sulphate of iron or
green vitriol. The fire is to be lowered while the sulphate dissolves,
and the bath is allowed to cool for half an hour, after which the stuff
is introduced, and well moved about for an hour, after which it is taken
out to air. Lastly, the remaining third of the bath is added to the
other two, taking care to squeeze the bag well. 18 or 22 lbs. of sumach
are thrown in; the whole is just brought to a boil, and then refreshed
with a little cold water; two pounds more of sulphate of iron are added,
after which the stuff is turned through for an hour. It is thereafter
washed, aired, and put again into the bath, stirring it continually for
an hour. After this, it is carried to the river, washed well, and then
filled. Whenever the water runs off clear, a bath is prepared with weld,
which is made to boil for an instant; and after refreshing the bath the
stuff is turned in to soften, and to render the black more fast. In this
manner, a very beautiful black is obtained, without rendering the cloth
too harsh.
Commonly more simple processes are employed. Thus the blue cloth is
simply turned through a bath of gall-nuts, where it is boiled for two
hours. It is next passed through a bath of logwood and sulphate of iron
for two hours, without boiling, after which it is washed and fulled.
Hellot has found that the dyeing might be performed in the following
manner:--For 20 yards of dark blue-cloth, a bath is made of two pounds
of fustic (morus tinctoria), 4-1/4 lbs. of logwood, and 11 lbs. sumach.
After boiling the cloth in it for three hours it is lifted out, 11 lbs.
of sulphate of iron are thrown into the boiler, and the cloth is then
passed through it during two hours. It is now aired, and put again in
the bath for an hour. It is, lastly, washed and scoured. The black is
less velvety than that of the preceding process. Experience convinced
him that the maddering prescribed in the ancient regulations only gives
a reddish cast to the black, which is obtained finer and more velvety
without madder.
A black may be dyed likewise without having given a blue ground. This
method is employed for cloths of little value. In this case they are
rooted; that is to say, they receive a dun ground with walnut husks, or
the root of the walnut tree, and are afterwards made black in the manner
above described, or in some other way; for it is obvious that a black
may be obtained by several processes.
According to Lewis, the proportions which the English dyers most
generally adopt are, for one hundred and twelve pounds of woollen cloth
previously dyed of a dark blue, about five pounds of sulphate of iron,
as much gall-nuts, and thirty pounds of logwood. They begin by galling
the cloth, they then pass it through the decoction of logwood, to which
the sulphate of iron has been added.
When the cloth is completely dyed, it is washed in the river, and passed
through the fulling-mill till the water runs off clear and colourless.
Some persons recommend, for fine cloths, to full them with soap water.
This operation requires an expert workman, who can free the cloth
thoroughly from the soap. Several recommend at its coming from the
fulling to pass the cloth through a bath of weld, with the view of
giving softness and solidity to the black. Lewis says, that passing the
cloth through weld, after it has been treated with soap, is absolutely
useless, although it may be beneficial when this operation has been
neglected.
Different operations may be distinguished in dyeing _silk_ black; the
boiling of the silk, its galling, the preparation of the bath, the
operation of dyeing, the softening of the black.
Silk naturally contains a substance called gum, which gives it the
stiffness and elasticity peculiar to it in its native state; but this
adds nothing to the strength of the silk, which is then styled raw; it
rather renders it, indeed, more apt to wear out by the stiffness which
it communicates; and although raw silk more readily takes a black
colour, yet the black is not so perfect in intensity, nor does it so
well resist the re-agents capable of dissolving the colouring particles,
as silk, which is scoured or deprived of its gum.
To cleanse silk intended for black, it is usually boiled four or five
hours with one fifth of its weight of white soap, after which it is
carefully beetled and washed.
For the galling, nut-galls equal nearly to three fourths of the weight
of the silk are boiled during three or four hours; but on account of the
price of Aleppo galls, more or less of the white gall-nuts, or of even
an inferior kind called galon, berry or apple galls, are used. The
proportion commonly employed at Paris is two parts of Aleppo galls to
from eight to ten parts of galon. After the boiling, the galls are
allowed to settle for about two hours. The silk is then plunged into the
bath, and left in it from twelve to thirty-six hours, after which it is
taken out and washed in the river.
Silk is capable of combining with quantities, more or less considerable,
of the astringent principle; whence results a considerable increase of
weight, not only from the weight of the astringent principle, but also
from that of the colouring particles, which subsequently fix themselves
in proportion to the quantity of the astringent principle which had
entered into combination. Consequently, the processes are varied
according to the degree of weight which it is wished to communicate to
the silk; a circumstance requiring some illustration.
The commerce of silk goods is carried on in two ways; they are sold
either by the weight, or by the surface, that is, by measure. Thus the
trade of Tours was formerly distinguished from that of Lyons; the silks
of the former being sold by weight, those of the latter, by measure. It
was therefore their interest to surcharge the weight at Tours, and, on
the contrary, to be sparing of the dyeing ingredients at Lyons; whence
came the distinction of light black and heavy black. At present, both
methods of dyeing are practised at Lyons, the two modes of sale having
been adopted there.
Silk loses nearly a fourth of its weight by a thorough boiling, and it
resumes, in the light black dye, one half of this loss; but in the heavy
black dye, it takes sometimes upwards of a fifth more than its primitive
weight; a surcharge injurious to the beauty of the black, and the
durability of the stuff. The surcharged kind is denominated English
black, because it is pretended that it was first practised in England.
Since silk dyed with a great surcharge has not a beautiful black, it is
usually destined for weft, and is blended with a warp dyed of a fine
black.
The peculiarity of the process for obtaining the heavy black consists in
leaving the silk longer in the gall liquor, in repeating the galling, in
passing the silk a greater number of times through the dye, and even
letting it lie in it for some time. The first galling is usually made
with galls which have served for a preceding operation, and fresh
gall-nuts are employed for the second. But these methods would not be
sufficient for giving a great surcharge, such as is found in what is
called the English black. To give it this weight, the silk is galled
without being ungummed; and, on coming out of the galls, it is rendered
supple by being worked on the jack and pin.
The silk-dyers keep a black vat, and its very complex composition varies
in different dye-houses. These vats are commonly established for many
years; and when their black dye is exhausted it is renovated by what is
called in France a _brevet_. When the deposit which has accumulated in
it is too great, it is taken out, so that at the end of a certain time
nothing remains of the several ingredients which composed the primitive
bath, but which are not employed in the brevet.
For the dyeing of raw silk black, it is galled in the cold, with the
bath of galls which has already served for the black of boiled silk. For
this purpose, silk, in its native yellow colour, is made choice of. It
should be remarked, that when it is desired to preserve a portion of the
gum of the silk, which is afterwards made flexible, the galling is given
with the hot bath of gall-nuts in the ordinary manner. But here, where
the whole gum of the silk, and its concomitant elasticity, are to be
preserved, the galling is made in the cold. If the infusion of galls be
weak, the silk is left in it for several days.
Silk thus prepared and washed takes very easily the black dye, and the
rinsing in a little water, to which sulphate of iron may be added, is
sufficient to give it. The dye is made in the cold; but, according to
the greater or less strength of the rinsings, it requires more or less
time. Occasionally three or four days are necessary; after which it is
washed, it is beetled once or twice, and it is then dried without
wringing, to avoid softening it.
Raw silk may be more quickly dyed, by shaking it round the rods in the
cold bath after the galling, airing it, and repeating these
manipulations several times, after which it is washed and dried as
above.
Macquer describes a more simple process for the black by which velvet is
dyed at Genoa; and he says that this process, rendered still simpler,
has had complete success at Tours. The following is his description.
For 1 cwt. (50 kilogrammes) silk, (22 lbs. 11 kilogrammes) of Aleppo
galls, in powder, are boiled for an hour in a sufficient quantity of
water. The bath is allowed to settle till the galls have fallen to the
bottom of the boiler, from which they are withdrawn; after which 32 lbs.
of English vitriol (or copperas) are introduced, with 13 lbs. of iron
filings, and 22 lbs. of country gum, put into a kind of two-handled
cullender, pierced every where with holes. This kettle is suspended by
two rods in the boiler, so as not to reach the bottom. The gum is left
to dissolve for about an hour, stirring it from time to time. If, after
this time, some gum remains in the kettle, it is a proof that the bath,
which contains two hogsheads, has taken as much of it as is necessary.
If, on the contrary, the whole gum is dissolved, from one to 4 lbs. more
may be added. This cullender is left constantly suspended in the boiler,
from which it is removed only when the dyeing is going on; and
thereafter it is replaced. During all these operations the boiler must
be kept hot, but without boiling. The galling of the silk is performed
with one third of Aleppo galls. The silk is left in it for six hours
the first time, then for twelve hours. The rest, _secundum artem_.
Lewis states that he has repeated this process in the small way; and
that, by adding sulphate of iron progressively, and repeating the
immersions of the silk a great number of times, he eventually obtained a
fine black.
Astringents differ from one another as to the quantity of the principle
which enters into combination with the oxide of iron. Hence, the
proportion of the sulphate, or of any other salt of iron, and that of
the astringents, should vary according to the astringents made use of,
and according to their respective quantities. Gall-nut is the substance
which contains most astringent; sumach, which seems second to it in this
respect, throws down (decomposes), however, only half as much sulphate
of iron.
The most suitable proportion of sulphate of iron appears to be that
which corresponds to the quantity of the astringent matter, so that the
whole iron precipitable by the astringent may be thrown down, and the
whole astringent may be taken up in combination with the iron. As it is
not possible, however, to arrive at such precision, it is better that
the sulphate of iron should predominate, because the astringent, when in
excess, counteracts the precipitation of the black colouring particles,
and has the property of even dissolving them.
This action of the astringent is such that, if a pattern of black cloth
be boiled with gall-nuts, it is reducible to grey. An observation of
Lewis may thence be explained. If cloth be turned several times through
the colouring bath, after it has taken a good black colour, instead of
acquiring more body, it is weakened, and becomes brownish. Too
considerable a quantity of the ingredients produces the same effect; to
which the sulphuric acid, set at liberty by the precipitation of the
oxide of iron, contributes.
It is merely the highly oxidised sulphate which is decomposed by the
astringent; whence it appears, that the sulphate will produce a
different effect according to its state of oxidisement, and call for
other proportions. Some advise, therefore, to follow the method of
Proust, employing it in the oxidised state; but in this case it is only
partially decomposed, and another part is brought, by the action of the
astringent, into the lower degree of oxidisement.
The particles precipitated by the mixture of an astringent and sulphate
of iron have not at first a deep colour; but they pass to a black by
contact of air while they are moist.
Under _dyeing_ I shall show that the black dye is only a very condensed
colour, and that it assumes more intensity from the mixture of different
colours likewise deep. It is for this reason advantageous to unite
several astringents, each combination of which produces a different
shade. But blue appears the colour most conducive to this effect, and it
corrects the tendency to dun, which is remarked in the black produced on
stuffs by the other astringents.
On this property is founded the practice of giving a blue ground to
black cloths, which acquire more beauty and solidity the deeper the
blue. Another advantage of this practice is to diminish the quantity of
sulphuric acid which is necessarily disengaged by the precipitation of
the black particles, and which would not only counteract their fixation,
but would further weaken the stuff, and give it harshness.
For common stuffs, a portion of the effect of the blue ground is
produced by the rooting.
The mixture of logwood with astringents contributes to the beauty of the
black in a twofold way. It produces molecules of a hue different from
what the astringents do, and particularly blue molecules, with the oxide
of copper, commonly employed in the black dyes; which appears to be more
useful the more acetate the verdigris made use of contains.
The boil of weld, by which the dye of black cloth is frequently
finished, may also contribute to its beauty, by the shade peculiar to
its combination. It has, moreover, the advantage of giving softness to
the stuffs.
The processes that are employed for wool, yield, according to the
observation of Lewis, only a rusty black to silk; and cotton is hardly
dyed by the processes proper for wool and silk. Let us endeavour to
ascertain the conditions which these three varieties of dyeing demand.
Wool has a great tendency to combine with colouring substances; but its
physical nature requires its combinations to be made in general at a
high temperature. The combination of the black molecules may therefore
be directly effected in a bath, in proportion as they form; and, if the
operation be prolonged by subdividing it, it is only with the view of
changing the necessary oxidisement of the sulphate, and augmenting that
of the colouring particles themselves.
Silk has little disposition to unite with the black particles. It seems
to be merely by the agency of the tannin, with which it is previously
impregnated, that these particles can fix themselves on it, especially
after it has been scoured. For this reason, silk baths should be old,
and have the colouring particles accumulated in them, but so feebly
suspended as to yield to a weak affinity. Their precipitation is
counteracted by the addition of gum, or other mucilaginous substances.
The obstacle which might arise from the sulphuric acid set at liberty is
destroyed by iron filings, or other basis. Thus, baths of a very
different composition, but with the essential condition of age, may be
proper for this dye. For cotton black dye, see CALICO PRINTING.
BLACK PIGMENT. The finest light black is prepared principally for the
manufacturing of printers’ ink. In Messrs. Martin and Grafton’s patent
process, the black is obtained by burning common coal-tar, which should,
however, be previously divested, as much as possible, of the ammoniacal
liquor and acid mixed with it in the tank.
For this purpose, it is proposed that four casks should be employed,
each capable of holding 130 gallons, and into every one of them are to
be put about 60 gallons of the rough impure tar, to which an equal
quantity of lime-water is to be added, and then agitated by machinery or
manual labour until the lime-water is completely mixed with the tar. The
vessels should next be suffered to rest for about six hours, by which
time the tar will settle at the bottom of the casks, and the water may
be drawn off. The casks containing the tar should now be filled with hot
water, which may be supplied from the boiler of a steam engine, and the
whole again agitated as before. This process may be repeated three
times, suffering the tar to subside between each; and twelve hours
should be allowed for settling from the last water, so that the whole of
the tar and water may become separated, the water rising to the top of
the cask, and the tar being left at the bottom in a pure state.
But, as some of the water will yet remain mechanically combined with the
tar, it is proposed that the tar should be subjected to the process of
distillation. For this purpose, a still, capable of holding 120 gallons,
may be employed, in which about 50 gallons, at one time, may be operated
upon; when, by a gentle heat, the water, and other impurities which the
tar may have retained, will be driven off. As soon as the water appears
to have evaporated, and the spirit runs fine and clear, the process of
distillation should be stopped; and, when cold, the pure tar may be
drawn off, and set apart for the purpose of being employed as
contemplated in the patent.
The tar thus purified may be now converted into black, or it may be
subjected to further rectification to divest it of the mineral pitch, or
asphaltum, which is combined with the oil and spirit: the latter is to
be preferred, because the mineral pitch, or asphaltum, is only
inflammable at a high temperature, which renders it more troublesome to
use in the process here contemplated, and also would cause the apparatus
to require frequent cleaning from the carbonized pitch deposited. In
order, therefore, to get rid of the mineral pitch, or asphaltum, forty
gallons of the tar are to be introduced into a still, as before; and,
instead of stopping the operation, as soon as the spirit begins to come
over, the distillation is continued with a strong heat, so as to force
over the whole of the oil and spirit, leaving the residuum of asphaltum
in the still: this process, however, is known to every chemist, and need
not be further explained.
[Illustration: 115 116]
In _fig._ 115. is exhibited a rude representation of the apparatus
employed in preparing and collecting the fine light spirit black,
produced by the combustion of the oil and spirit of coal-tar, after it
has been purified as above described. _a_ is the brickwork which
supports a number of burners issuing from a tube, _b_, within, and here
shown by dots, as passing along its whole length. _Fig._ 116. is a
section of the brickwork, with the tube, burner, and receiver, as will
be described hereafter. The tube may be called the tar main, as it is
intended to be filled with tar: it is constructed of cast iron, and from
it issue several (in this figure twenty-four) jets or burners, _c_, _c_,
_c_; any other number may be employed. _d_ is a furnace under the tar
main, the flue of which extends along, for the purpose of heating the
tar to the boiling point, in order to facilitate the process. From the
main, _b_, the tar flows into the jets _c_; wicks are introduced into
the jets, and, when set fire to by a red-hot stick, will burn and emit a
very considerable quantity of smoke; which it is the object of this
apparatus to conduct through many passages, for the purpose of
collecting its sooty particles.
There are a number of hoods, _e_, _e_, _e_, or bonnets, as they are
termed, all of which, through their pipes, have communication with, or
lead into, a main chimney, _f_, _f_. Into these hoods or bonnets the
smoke of the burners ascends, and from thence passes into the main
chimney _f_, and thence through the smoke tubes into the box _g_: here
the heaviest particles of the black deposit themselves; but, as the
smoke passes on through the farther pipes, a deposit of the second, or
finer, particles of black takes place in the box _h_. From hence the
smoke proceeds through other pipes into a series of canvass bags, _i_,
_i_, _i_, which are proposed to be about eighteen feet long, and three
in diameter. These bags are connected together at top and bottom
alternately, and through the whole series the smoke passes up one bag
and down the next, depositing fine black, called spirit black, upon the
sides of the canvass. After the jets have continued burning for several
days, the bags are to be beaten with a stick, so that the black may fall
to the bottom; and, when a sufficient quantity has accumulated, the bags
may be emptied and swept out. Thus seventy or eighty bags may be
employed; so that the smoke should pass through a length of about 400
yards, the farthest of which will be found to contain the finest black.
The last bag should be left open, in order to allow the vapour to escape
into the open air.
The main tar tube will require to be emptied every four or five days, in
order to clear it from the pitchy matter that may have subsided from the
burners, and they also will require to be frequently poked with a wire,
to clear off the black which forms upon the edges, and to drive down the
carbonized tar which attaches itself to the upper part of the jets.
BLEACHING (_Blanchiment_, Fr.; _Bleichen_, Germ.) is the process by
which the textile filaments, cotton, flax, hemp, wool, silk, and the
cloths made of them, as well as various vegetable and animal substances,
are deprived of their natural colour, and rendered nearly or altogether
white. The term bleaching comes from the French verb _blanchir_, to
whiten. The word _blanch_, which has the same origin, is applied to the
whitening of living plants by making them grow in the dark, as when the
stems of celery are covered over with mould.
The operations which the bleacher has recourse to differ according to
the nature of the bleaching means, the property of the stuff to be
bleached, and local customs or circumstances; and the result is also
obtained with more or less rapidity, certainty, economy, and perfection.
The destruction of the colouring matters attached to the bodies to be
bleached is effected either by the action of the air and light, of
chlorine, or sulphurous acid; which may be considered the three
bleaching powers employed for manufacturing purposes.
Bleaching by the influence of air and sunshine is the most ancient, and
still the most common, method in several civilised countries; it is also
supposed by many to be the least injurious to the texture of yarn and
cloth. The operations it involves are very simple, consisting in the
exposure of the goods upon a grass-plat to the sky, with their
occasional aspersion with moisture if necessary, in addition to the rain
and dew. The atmospheric air effects the bleaching by means of its
oxygenous constituent, which combines with the colouring matter, or its
elements carbon and hydrogen, and either makes it nearly white, or
converts it into a substance easily soluble in water and alkaline
solutions. This natural process is too slow to suit the modern demands
of the cotton and linen manufacturers. Fortunately for them, a new
bleaching agent, unknown to our forefathers, has been discovered in
chlorine, formerly called oxymuriatic acid, an agent modified by
chemistry so as to give an astonishing degree of rapidity, economy, and
perfection, to this important art. It is, however, not a little
surprising, that the science which has so greatly advanced its practical
part should have left its theory far from complete, and should afford no
satisfactory answers to the two following questions.--What is the action
of the solar rays upon the colouring matter? How do air and chlorine
operate upon this principle? Some suppose that light _predisposes_ the
colouring matter to combine with oxygen; others fancy that it acts
merely in the manner of a high temperature, so as to determine a
reaction between the elements of that substance, and to cause a new
combination possessed of peculiar properties. It is generally admitted
at the present day, that a portion of the oxygen of the air passes into
the colouring matter, and changes its constitution. This is, however,
probably not the part which oxygen plays, nor is it the only principle
in the atmosphere which exercises a bleaching influence. Neither is the
action of chlorine such as has been commonly represented in our chemical
systems.
But if authors offer us only vague hypotheses concerning the three
principal agents, light, oxygen, chlorine, they afford no information
whatever concerning the phenomena due to greasy spots so frequently
found upon cotton cloth, and so very troublesome to the bleacher. It has
indeed been sometimes said in bleach-works, that fatty substances are no
longer soluble in alkalies when they are combined with oxygen. The very
reverse of this statement is probably nearer the truth.
The object of bleaching is to separate from the textile fibre, by
suitable operations, all the substances which mask its intrinsic
whiteness; or which, in the course of ulterior dyeing operations, may
produce injurious effects. In this latter respect, cotton deserves
especial consideration. This substance is covered with a resinous
matter, which obstructs its absorption of moisture, and with a yellow
colouring matter in very small quantity, often so inconsiderable in some
cottons, that it would be unnecessary to bleach them, before submitting
them to the dyer, were it not that the manipulations which they undergo
introduce certain impurities which are more or less injurious, and must
be removed. It is in fact a circumstance well known in the factories,
that unbleached cottons may be dyed any dark colour, provided they are
deprived of that matter which makes them difficult to moisten. The
substances present in cotton goods are the following:--
1. The resinous matter natural to the cotton filaments.
2. The proper colouring matter of this vegetable.
3. The paste of the weaver.
4. A fat matter.
5. A cupreous soap.
6. A calcareous soap.
7. The filth of the hands.
8. Iron, and some earthy substances.
1. The matter which prevents the moistening of cotton wool may be
separated by means of alcohol, which, when evaporated, leaves thin
yellowish scales, soluble in alkalies, in acids, and even in a large
quantity of boiling water. For a long time the bleaching process
commenced with the removal of this resinous stuff, by passing the cloth
or the yarn through an alkaline ley. This was called scouring; it is now
nearly laid aside.
2. The colouring matter of cotton seems to be superficial, and to have
no influence on the strength of the fibres; for the yarn is found to be
as strong after it has been stripped by caustic soda of its resinous and
colouring matters, as it was before. The colouring matter is slightly
soluble in water, and perfectly in alkaline leys. When gray calico is
boiled in lime water, it comes out with a tint darker than it had
before; whence it might be supposed that the colouring matter was not
dissolved out, even in part. This, however, is not the case; for if we
filter the liquor, and neutralise it with an acid, we shall perceive
light flocks, formed of the resinous substance, united with the
colouring matter. The dark colour of the cloth is to be ascribed solely
to the property which lime possesses of browning certain vegetable
colours. This action is here exercised upon the remaining colour of the
cloth.
It may be laid down as a principle, that the colouring matter is not
directly soluble by the alkalies; but that it becomes so only after
having been for some time exposed to the joint action of air and light,
or after having been in contact with chlorine. What change does it
thereby experience, which gives it this solubility? Experiments made
upon pieces of cloth placed in humid oxygen, in dry oxygen, in
moist chlorine, and in dry chlorine, tend to show that hydrogen is
abstracted by the atmosphere; for in these experiments proofs of
_dis-hydrogenation_ appeared, and of the production of carbonic acid. In
all cases of bleaching by chlorine, this principle combines immediately
with the hydrogen of the colouring matter, and forms muriatic acid,
while the carbon is eliminated.
Undoubtedly water has an influence upon this phenomenon, since the
bleaching process is quicker with the humid chlorine than with the dry;
but this liquid seems to act here only mechanically, in condensing the
particles of the gas into a solution. We should also take into account
the great affinity of muriatic acid for water.
3. The weaver’s dressing is composed of farinaceous matters, which are
usually allowed to sour before they are employed. It may contain glue,
starch, gluten; which last is very soluble in lime-water.
4. When the dressing gets dry, the hand-weaver occasionally renders his
warp-threads more pliant by rubbing some cheap kind of grease upon them.
Hence it happens, that the cloth which has not been completely freed
from this fatty matter will not readily imbibe water in the different
bleaching operations; and hence, in the subsequent dyeing or dunging,
these greasy spots, under peculiar circumstances, somewhat like
lithographic stones, strongly attract the aluminous and iron mordants,
as well as the dye stuffs, and occasion stains which it is almost
impossible to discharge. The acids act differently upon the fatty
matters, and thence remarkable anomalies in bleaching take place. When
oil is treated with the acetic or muriatic acid, or with aqueous
chlorine, it evolves no gas, as it does with the sulphuric and nitric
acids, but it combines with these substances so as to form a compound
which cannot be dissolved by a strong boiling ley of caustic soda.
Carbonic acid acts in the same way with oil. On the other hand, when the
oils and fats are sufficiently exposed to the air, they seize a portion
of its oxygen, and become thereby capable of saponification, that is,
very soluble in the alkalies.
5. When the hand-weaver’s grease continues in contact for a night with
the copper dents of his reed, a kind of cupreous soap is formed, which
is sometimes very difficult to remove from the web. Lime-water does not
dissolve it; but dilute sulphuric acid carries off the metallic oxide,
and liberates the margaric acid, in a state ready to be acted on by
alkalis.
6. When cloth is boiled with milk of lime, the grease which is
uncombined unites with that alkaline earth; and forms a calcareous soap,
pretty soluble in a great excess of lime-water, and still more so in
caustic soda. But all fats and oils, as well as the soaps of copper and
lime, cease to be soluble in alkaline leys, when they have remained a
considerable time upon the goods, and have been in contact with acetic,
carbonic, muriatic acids, or chlorine. These results have been verified
by experiment.
7. Cotton goods are sometimes much soiled, from being sewed or tamboured
with dirty hands; but they may be easily cleansed from this filth by hot
water.
8. Any ferruginous or earthy matters which get attached to the goods in
the course of bleaching, are readily removable.
We are now prepared to understand the true principles of bleaching
cotton goods, for the most delicate operations of the calico printer.
1. The first process is steeping, or rather boiling, the goods in water,
in order to remove all the substances soluble in that liquid.
2. The next step is to wash or scour the goods by the dash-wheel or the
stocks. This is of great importance in the course of bleaching, and must
be repeated several times; so much so, that in winter, when the water of
the dash-wheel is cold, the bleaching is more tedious and difficult.
Yarn and very open fabrics do not much need the dash-wheel.
By these first two operations, the woven goods lose about sixteen per
cent. of their weight, while they lose only two parts out of five
hundred in all the rest of the bleaching.
3. In the third place the calicoes are boiled with milk of lime, whereby
they are stripped of their gluten, and acquire a portion of calcareous
soap. Formerly, and still in many bleach-works, the gluten was got rid
of by a species of fermentation of the farinaceous dressing; but this
method is liable to several objections in reference to the
calico-printer. 1. The fermentative action extends sometimes to the
goods, and weakens their texture, especially when they are piled up in a
great heap without being previously washed. 2. The spots of grease, or
of the insoluble soaps, become thereby capable of resisting the caustic
alkalies, and are rendered in some measure indelible; an effect due to
the acetic and carbonic acids generated during fermentation, and which
will be easily understood from what has been said concerning the action
of acids on fatty substances. It is not, therefore, without good reason
that many practical men throw some spent leys into the fermenting vats,
to neutralise the acids which are formed. Were it not for the presence
of fat, fermentation, skilfully conducted, would be an excellent means
of carrying off the gluten; and the steep is therefore applicable to
power-loom goods, which are not polluted with grease.
4. The goods are now subjected to a caustic soda ley, which dissolves
out the soaps of lime and copper, as well as that portion of the
colouring matter which is sufficiently dis-hydrogenated to be capable of
combining with it. This bucking with ley, which is repeated several
times upon the goods, in order to purge them completely from the fatty
matter present in the hand-loom webs, and also partially introduced in
the spinning, is almost the only operation to which yarns for turkey red
are subjected. After being boiled in a caustic soda ley, they are passed
through solutions of chloride of lime, and afterwards through the acid
steep.
5. When the goods are sufficiently bucked in the leys, they are either
exposed to chlorine, or laid out on the grass; sometimes both are had
recourse to for delicate work. These different modes of action have the
same influence on the colouring matter, but they give rise to different
effects in reference to greasy stains.
The goods are dipped in a solution of chloride of lime, which should be
kept tepid by means of steam. Alongside of the chlorine cistern, there
is another filled with dilute sulphuric or muriatic acid. When the goods
are taken out of the chlorine, they are drained on the top of its
cistern till no more liquid runs off them, and they are then plunged
into the _sour_. The action of the acid in the present case may be
easily explained. In proportion as a salt of lime is formed, this base
quits the chlorine, and allows it to act freely upon the colouring
matter. Thus we prevent the development of too great a quantity of
chlorine at once, which would be apt to injure the fibres; and we pursue
both a prudent and economical plan. Only so much chlorine as is strictly
necessary is called forth, and hence it excites no smell in the
apartment.
The chlorine serves to acidify the colouring matter, by abstracting a
portion of its hydrogen; but we must take the greatest care that there
is no grease upon the goods before immersion in it, for the consequence
would be, as above shown, very troublesome spots. When the cloth is laid
out upon the grass, it is the oxygen of the air which acidifies the
colouring matter; for which reason, the dew, which contains much air
rich in oxygen, singularly accelerates the bleaching process. It is
likewise, by absorbing oxygen from the atmosphere, that fats or oils
pass to the state of margaric and oleic acids, and become most easily
saponified. Should the goods, however, be left too long on the grass,
the fats absorb carbonic acid, and become insoluble in leys.
6. The goods must now receive a new soda ley, to dissolve out that
portion of the colouring matter which has been dis-hydrogenated in the
chlorine of the air, as well as the grease, if any perchance remained in
the soluble state. These last two operations are to be several times
repeated, because the colouring matter should be removed only by
degrees, for fear of injuring the texture of the goods, by subjecting
them to too much chlorine at a time.
7. We finish with the dilute sulphuric acid, which should be very weak
and tepid. It dissolves out the iron, and some earthy matters
occasionally found upon cotton. The goods must be most carefully washed
at the dash-wheel, or in a stream of water on quitting the sour bath,
for if the acid were allowed to dry in them, it would infallibly injure
their texture by its concentration. In winter, if the goods are allowed
to get frozen with the acid upon them, they may likewise be damaged.
We may here observe, that when the goods are not to remain white, their
bleaching may be completed with a ley; for though it leaves a faint
yellow tint, this is no inconvenience to the dyer. But when they are to
be finished with a starching after the last ley, they must have another
dip of the chlorine to render the white more perfect. An immersion in
the dilute acid has nearly the same effect.
The principles expounded above lead to this important consequence, that
when we wish to bleach goods that are free from greasy stains, as is the
case generally with the better kinds of muslins, or when we wish to
bleach even greasy goods for the starch finish, we may content ourselves
with the following operations:--
1. Boiling in water.
2. Scouring by the stocks or the dash-wheel.
3. Bucking with milk of lime.
4. Passing through chlorine, or exposure on the grass.
5. Bucking, or bouking with milk of lime. These two latter operations
require to be alternated several times, till the whole of the colouring
matter be removed.
6. Souring.
The bleaching of goods, which are never laid down on the green, and
which are not dried between two operations, may be completed in a couple
of days. They answer as well for the printer as the others, and they are
as white. Cotton fibres or yarns suffer no diminution of their strength,
when the cloth has been properly treated in the above described
processes.
Accurate experiments have demonstrated that their strength is not
impaired by being boiled in milk of lime for two hours at the ordinary
pressure, provided they be constantly kept covered with liquid during
the whole ebullition, and that they be well washed immediately
afterwards; or, by being boiled in pure water under the pressure of ten
atmospheres of steam; or by being boiled under the same pressure in a
caustic soda ley, marking 3° of Tweedale, or specific gravity 1·015,
though it has increased to double the density in the course of the boil,
by the escape of the steam; or by being boiled under the atmospheric
pressure at 14° of Tweedale, or specific gravity 1·070; or by being
immersed for eight hours in chloride of lime, capable of decolouring
three times its bulk, of test solution of indigo (see CHLORINE); and by
being afterwards dipped in sulphuric acid of specific gravity 1·067,
Tweedale 14°; or by being steeped for eighteen hours in sulphuric or
muriatic acid of specific gravity 1·035, 7° Tweedale.
In other well-conducted bleach-works the following is the train of
operations:-- 1. Cleansing out the weaver’s dressing by steeping the
cloth for twelve hours in cold water, and then washing it at the stocks
or the dash-wheel. 2. Boiling in milk of lime, of a strength suited to
the quality of the goods, but for a shorter time than with the soda ley;
two short operations with the lime, with intermediate washing, being
preferable to one of greater duration. 3 and 4. Two consecutive leys of
ten or twelve hours’ boiling, with about two pounds of soda crystals for
1 cwt. of cloth. 5. Exposure to the air for six or eight days, or the
application of the chloride of lime and the sulphuric acid. 6. A ley of
caustic soda, like the former, sometimes with less alkali. 7. Exposure
to the air for six or eight days, or chlorine and the sour, as above. 8.
Caustic soda ley, as before. 9. Chlorine and the sour. 10. Rinsing in
hot water, or scouring at the dash-wheel.
If the number of vessels to be heated exceeds four or five, there is an
economy in using steam as the medium of heat; but under this number
there is an advantage in the direct application of fire to a boiling or
bucking apparatus; since when only two vessels are in activity, there is
a waste of fuel by the extra steam power. It deserves to be remarked
also, that the increase of the bulk of the liquid by the condensation of
the steam, does not permit the spent white ley to be turned to use for
the green goods, on account of its excessive dilution. With the milk of
lime boil, however, this dilution would be rather an advantage.
It has been found that the introduction of bran into the fermenting
steep (when this is used) endangers the texture of the goods, by causing
a putrefactive fermentation in some places.
When in the milk of lime boil there is too much of this caustic earth,
or when it is poured in on the top of the goods, they are apt to suffer
damage. The milk of lime should be introduced from beneath into the
under compartment of the bucking apparatus. For the same reason, after
the caustic soda lye, the vessel should be filled up with water, if the
goods be not immediately transferred to the dash-wheel. When they are
allowed to become partially dry on the top, they are easily injured. The
copper of the bucking apparatus ought to be of a size proportioned to
that of the surmounting crib or vat; for when it is too small, the
liquid is too long of being brought into proper circulation, and the
goods may be meanwhile injured. In a bucking apparatus, which requires
five or six hours to be brought into full play, those goods are very apt
to be injured, which lie immediately under the overflow pipe.
When the chloride of lime steep is too strong, sometimes small round
holes are made in the calico, just as if they had been cut out by a
punch, especially in the borders or thicker parts of the goods. This
accident is owing to the presence of bubbles of chlorine. From the
saturated state of the liquid, they remain gaseous a sufficient length
of time for corroding the parts of the cloth with which they are in
contact. These will be obviously the denser parts, for they confine the
gas most completely, or prevent its diffusion through the mass. This
evil is prevented by diluting the chloride steep to the proper degree,
and moving the goods through it.
The greasy spots, described above, show themselves in the maddering by
attracting the dye-stuff more copiously than the pure parts of the
cloth, so as to mottle it; they are also recognised in the white goods
by being somewhat repulsive of moisture. When the combination of fatty
matters with chlorine takes place at the surface of cotton goods, it is
of a nature to resist the action of alkalies. It is the stearine, or the
principle of suet, particularly, which, by this means, acquires such a
strong affinity for cottons; the elaine, or the principle of oils, has
no such remarkable affinity. Lime, in some circumstances, seems to act
as a mordant to greasy matters, and to fix them fast. Hence the weaver
should be prohibited, in all cases, from allowing candle-grease to touch
his web. Goods soiled with it should never be allowed to lie by in the
warehouse, but be immediately cleansed before the air has fixed the
stearine by converting it into margaric acid. Lime should, in these
cases, be prudently employed; chlorine should never be used till the
greasy stains are thoroughly removed; and the bleacher should never
warrant his pieces for the printer till he has verified some of them by
the water test.
I shall conclude this general analysis of the principles of bleaching by
a few precepts. Avoid lime, at the first ley, for goods which contain
greasy spots; but use it freely after one or two soda leys, and apply
two soda leys after it. Do not apply chlorine between these leys, but
reserve it for the final operation. By this plan the goods will be well
bleached, and very little worn. Use the souring steeps freely, giving
them after each ley, whether of lime or soda, since the calcareous base,
with which the greasy spots get charged merely from hard water, is an
obstacle to the further action of the leys.
I shall now give some practical instructions concerning the several
steps of the bleaching process, as applied to cotton, linen, silk, and
wool.
The first thing which the cotton bleacher does, is to mark the pieces
with the initials of the owner, by means of a stamp imbued with coal
tar. The linen bleacher marks with nitrate of silver, a far more
expensive substance, but one which resists better the severer treatment
which his goods are destined to undergo.
The cotton goods are generally singed before they are sent to the
bleacher, and this is done either by passing them rapidly over a red-hot
semi-cylinder of iron, or over a row of gas flames, by Mr. Hall’s
ingenious contrivance. (See SINGEING.) Each piece is next creased
together lengthwise like a rope, folded into a bundle, and fixed by a
noose at the end. In this open state it is easily penetrated by the
water of the soaking cistern into which it is thrown. It is then scoured
by the dash or wash-wheel. It is now ready for the bucking or steaming
apparatus, where it is treated with milk of lime. The steam chamber
resembles the bucking vessel, without its bottom copper; that is to say,
a few inches below the grated bottom of the bucking tub, there is a
close iron sole, through the centre of which the steam is admitted by
several small apertures, for the purpose of diffusing it throughout the
goods, and causing a liquid circulation by its pressure, as the steam
does in the proper bucking boiler. One pound of lime previously made
into a cream consistenced mixture, and passed through a sieve, is used
for every thirty or forty pounds of cloth, according to its colour and
texture; and this cream mixed with more water is interstratified with
the pieces, as they are laid regularly in the vessel. Whenever this is
stocked with goods, all their interstices are filled up with water.
After the lime bucking, the cloth is transferred to the dash-wheel.
A pound of cloth requires for its whitening about half a pound of good
average chloride of lime or bleaching powder, as it is commonly called,
and this ought to be dissolved in about three gallons of water. Mr. Crum
of Thorniebank, near Glasgow, an extensive and excellent bleacher, has
so modified Dr. Dalton’s ingenious plan of testing the power of
bleaching liquors by green sulphate of iron, as to give it much greater
precision for the bleacher’s use, than the discolouration of indigo
originally proposed by Berthollet. Mr. Crum dissolves four ounces of
fresh green vitriol in hot water, and then adds the solution of
bleaching powder by small quantities at a time, till the iron becomes
wholly peroxidised, when the smell of chlorine will become perceptible.
When the bleacher has once found by trial the proper blanching power
which his chlorine steep ought to have, he can verify its standard, by
seeing how much of it must be added to an ounce, or any given weight of
fresh copperas, dissolved in hot water, to cause the peroxidisement and
the exhalation of the peculiar odour. M. Gay Lussac’s new method by
arsenious acid will be described under chlorine. From the experiments
which I made some years ago[9], upon indigo, it will be seen that this
dye stuff is so variable in its quantity of colouring matter, that no
two chemists operating with it independently, as a test for chloride of
lime, could arrive at the same result. They must provide themselves with
absolute indigo, by an expensive and troublesome process, not suited to
the busy bleacher. The vitriolage, as the French term it, or the souring
of the English bleacher, consists in immersing the goods for four hours
in dilute sulphuric acid, containing one gallon of oil of vitriol to
from 25 to 30 of water, thoroughly intermixed by stirring; for the
density of the acid is an obstacle to its equal distribution through the
water. This dilute acid will have a density of from 1·047 to 1·040, and
will contain from 7 to 6-1/2 per cent. by weight of the oil of vitriol.
[9] Quarterly Journal of Science, Literature, and the Arts, vol. vii.
p. 160.
The goods are now washed, and then boiled for eight or nine hours in an
alkaline ley, containing about two pounds of crystals of soda, or their
equivalent in soda ash or pearl-ash, for every 100 lbs. of cloth. The
ley must be made previously caustic by quick lime. A washing in the
wheel follows this boil; and then a chlorine steep for five hours in a
liquor two thirds of the strength of the former. It is next soured in
the dilute sulphuric acid, for two, three, or four hours, according to
the colour and quality of the cotton, and then thoroughly washed.
The cloth is now bleached white, but cannot be presented in the market
till it undergoes certain finishing processes. The piece is elongated
from the folds which it contracts during the rotation of the dash-wheel,
by being thrown into a stream of water in a cistern, terminated by the
squeezing rollers, which take in the end of the piece, and run it
through between them, with the effect of making it nearly dry. Two
pieces of cloth pass simultaneously through the rollers, and are
disentangled spontaneously, so to speak, without the help of hands.
[Illustration: 117 118]
The squeezing rollers or squeezers, for discharging the greater part of
the water from the yarns and goods in the process of bleaching, are
represented in _figs._ 117, 118., the former being a side-view, to show
how the roller gudgeons lie in the slots of the frame, and how the shaft
of the upper roller is pressed downward by a weighted lever, through a
vertical junction road, jointed at the bottom to a nearly horizontal
bar, on whose end the proper weight is hung. In _fig._ 118. these
rollers of birch-wood are shown in face; the under one receiving motion
through the toothed wheel on its shaft, from any suitable power of water
or steam. Upon the shaft of the latter, between the toothed wheel and
the roller, the lever and pulley for putting the machine into and out of
geer is visible. The under roller makes about 25 revolutions in the
minute, in which time three pieces of goods, stitched endwise, measuring
28 yards each, may be run through the machine, from a water trough on
one side, to a wooden grating upon the other.
When the goods are run through, they are carried off upon a grated
wheelbarrow, in a nearly dry state, and transferred to the spreading
machine, called at Manchester a _candroy_. In many bleach-works,
however, the creased pieces are pulled straight by the hands of women,
and are then strongly beat against a wooden stock to smooth out the
edges. This being done, a number of pieces are stitched endwise
together, preparatory to being mangled.
[Illustration: 119 120 121]
_Calender._--_Fig._ 120. is a cross section of this machine, and _figs._
119. 121. are front views broken off. The goods are first rolled upon
the wooden cylinder _a_, near the ground; by the tension roller _b_,
upon the same cylinder, the goods receive a proper degree of stretching
in the winding off. They then pass over the spreading bars _c c c_, by
which they are still more distended; next round the hollow iron cylinder
_d_, 16 inches diameter, and the paper cylinder _e_, of like dimensions;
thence they proceed under the second massive iron cylinder _f_, of 8
inches diameter, to be finally wound about the projecting wooden roller
_g_. This is set in motion by the pulleys _h_, _fig._ 121., and _i_,
_fig._ 120., and receives its proper tension from the hanging roller
_k_; _l_ is a press cylinder, of 14 inches diameter, made of plane-tree
wood. By its means we can at all times secure an equal degree of
pressure, which would be hardly possible did the weighted lever press
immediately upon two points of the calender rollers. The compression
exercised by the cylinders may be increased at pleasure by the bent
lever _m_, weights being applied to it at _n_. The upper branch of the
lever _o_ is made fast by screws and bolts at _p_, to the upper
press-cylinder. The junction leg _q_ is attached to the intermediate
piece _r_, by left and right-handed screws, so that according as that
piece is turned round to the right or the left, the pressure of the
weighted roller will be either increased or diminished. By turning it
still more, the piece will get detached, the whole pressure will be
removed, and the press-roller may be taken off; which is a main object
of this mechanism.
The unequable movement of the cylinders is produced by the wheels _s t
u_, of which the undermost has 69, the uppermost has 20, and the
carrier-wheel _t_, either 33, 32, or 20 teeth, according to the
difference of speed required. The carrier-wheel is bolted on at _v_, and
adjusted in its proper place by means of a slot. To the undermost iron
cylinder, the first motion is communicated by any power, for which
purpose either a rigger (driving pulley) is applied to its shaft at _u_,
or a crank motion. If it be desired to operate with a heated calender,
the undermost hollow cylinder may be filled with hot steam, admitted
through a stuffing box at one end, and discharged through a stuffing box
at the other, or by a red-hot iron roller.
Pure starch would be too expensive a dressing for common calico
shirtings, and therefore an extemporaneous starch is made by mixing one
pound of flour with one gallon of water, and allowing the mixture to
ferment in a warm place for twenty-four hours. In this way, a portion of
_lactic_ acid is formed, which dissolves the gluten, or separates it
from the starch; so that when the whole is thrown upon a sieve, a liquid
paste passes through, which, being boiled, answers well for stiffening
the goods, without giving them a gray tinge. The paste is thinned with
water to the desired degree, and faintly tinged with solution of indigo.
The starch, which is sometimes thickened with porcelain clay, Paris
plaster, or Spanish white, is put into a trough, and is evenly imparted
to the cloth as this is drawn down through it, by the traction of
rollers. There is a roller near the bottom of the trough, round which
the cloth is made to run, to secure its full impregnation; while the
upper rollers serve to expel its excess of the starch, and throw it back
into the cistern. See STARCHING APPARATUS.
The goods are next dried in an apartment heated by two, three, or more
flues, running along the floor, and covered usually with fire-tiles. At
first the heat is moderate, but it is gradually raised to upwards of
110° F.
The goods must now be passed again through the calender, in order to
receive their final smoothness and lustre. They are in the first place
damped with a peculiar machine, furnished with a circular brush, whose
points revolve in contact with water in a trough placed beneath them,
and sprinkle drops of water upon the goods as they are drawn forwards by
a pair of cylinders. They are then subjected to the powerful pressure of
the calender rollers.
The calendered pieces are neatly folded into compact parcels, and
stamped with the marks of each particular manufacturer, or various
devices to suit the markets for which they are designed. They are
finally piled on the sole of an hydraulic press, with a sheet of
pasteboard between each piece; but with occasional plates of iron to
secure uniformity of pressure throughout. When sufficiently condensed by
the press, they are taken out, and despatched to their respective
manufacturers in a state ready for sale.
There are no less than 25 steps in the bleaching of calicoes, many of
them effected with expensive machinery; yet the whole do not produce to
the bleacher more than 10 pence per piece, of 24 yards.
The following system was pursued a few years back, by a skilful bleacher
of muslins near Glasgow:--
“In fermenting muslin goods, we surround them with our spent leys, from
the temperature of 100° to 150° F., according to the weather, and allow
them to ferment for 36 hours. In boiling 112 lbs. = 112 pieces of
yard-wide muslin, we use 6 or 7 lbs. of pearl-ashes, and 2 lbs. of soft
soap, with 360 gallons of water, and allow them to boil for 6 hours;
then wash them, and boil them again with 5 lbs. of pearl-ashes, and 2
lbs. of soft soap, and allow them to boil 3 hours; then wash them with
water, and immerse them into the solution of oxymuriate of lime, at 5 on
the test-tube, and allow them to remain from 6 to 12 hours; next wash
them, and immerse them into dilute sulphuric acid at the specific
gravity of 3-1/2 on Tweedale’s hydrometer = 1·0175, and allow them to
remain an hour. They are now well washed, and boiled with 2-1/2 lbs. of
pearl-ashes, and 2 lbs. of soft soap for half an hour; afterwards washed
and immersed into the oxymuriate of lime as before, at the strength of 3
on the test-tube, which is stronger than the former, and allowed to
remain for 6 hours. They are again washed, and immersed in diluted
sulphuric acid at the specific gravity of 3 on Tweedale’s hydrometer =
1·015. If the goods be strong, they will require another boil, steep,
and sour. At any rate, the sulphuric acid must be well washed out before
they receive the finishing operation with starch.
“With regard to the lime, which some use instead of alkali immediately
after fermenting, the same weight of it is employed as of pearl-ashes.
The goods are allowed to boil in it for 15 minutes, but not longer,
otherwise the lime will injure the fabric.”
More recently the plan adopted is as follows; by which the purest whites
are produced for the London market.
“Lime is seldom used for our finer muslin goods, as it is found to
injure their fabric, and the colours do not keep for any length of time.
“An alkaline ley is made by boiling equal weights of lime and soda
together for an hour: this alkali is used for boiling goods the same as
potash, but without soap.
“In finishing jacounets or muslins, after washing them from the sour,
they are run through spring-water containing a little fine smalts, which
give them a clear shade; if of a coarse fabric, a little well-boiled
starch is added to the water. From this they are wrung or pressed, and
taken up by the selvage for the breadthing frame, and are run off it
upon a tin cylinder heated by steam, by which the piece is completely
dried in 15 minutes: it is then stripped from the cylinder, neatly
folded and pressed, which finishes the piece for the market. From 6_d._
to 9_d._ per piece of 12 yards is obtained for the bleaching and
finishing of those goods.
“Book muslins, after being washed from the sour, are wrung or pressed;
then they are hung up to dry in a heated stove, previous to being put
into starch, prepared by boiling 3 lbs. of it to every 5 gallons of
water, with 20 ounces of smalts: they are wrung out of this starch, and
taken to a room heated to 110° F.; the starch is wrought into the piece
till clear, then taken into a cold room, and the selvages dressed or
set, before being put on the breadthing frame in the heated stove, where
the piece is stretched to its length, while three or four persons at
each selvage keep the piece to its breadth. If a stiff finish is wanted,
they keep exactly opposite each other; but in breadthing the piece of
elastic, they cross the piece in breadthing, which gives it a springy
elastic finish. From 9_d._ to 15_d._ per piece of 12 yards is obtained
for the bleaching and finishing of these goods.
“Sewed trimmings, flounces, and dresses are run through spring water
containing fine smalts with a little well-boiled starch. They are then
taken to the drying stove, where they are stented till dry, which
finishes the piece for the market. From 6_d._ to 8_d._ per piece is
obtained for trimmings and flounces, and from 9_d._ to 1_s._ for
dresses, bleaching and finishing.”
In the bleaching of cotton cloth, where fixed colours are previously
dyed in the yarn before it is woven into cloth, such as the Turkey or
Adrianople red, and its compounds of lilac or purple, by the addition of
iron bases, various shades of blue from indigo, together with buff and
gold colour, tinged with the oxides of iron, great care is necessary.
The common process of bleaching pulicates, into which permanent colours
are woven, is, to wash the dressing or starch well out in cold water; to
boil them gently in soap, and, after again washing, to immerse them in a
moderately strong solution of the oxymuriate of potash; and this process
is followed until the white is good: they are then soured in dilute
sulphuric acid. If the goods are attended to in a proper manner, the
colours, in place of being impaired, will be found greatly improved, and
to have acquired a delicacy of tint which no other process can impart to
them.
Pulicates, or ginghams, which have been woven along with yarn which has
been previously bleached, are first freed by washing from the starch or
dressing: they are then washed, or slightly boiled with soap. After
which, they are completely rinsed in pure spring water, and then soured.
Besides these common processes for bleaching, another was some time ago
introduced, which consisted in immersing the cotton or linen goods in
pretty strong solution of caustic alkali, and afterwards exposing them
to the action of steam in a close vessel. It is now generally abandoned.
The cotton or linen goods having been previously cleaned by steeping and
washing, were, after being well drained, steeped in a solution of
caustic alkali of the specific gravity of 1020. After the superfluous
alkaline ley had been drained from them, they were arranged on a grating
in a receiver. The cover was then placed on the vessel, and firmly
screwed down; and the steam was admitted by turning the stop-cock of the
pipe which communicated with a steam boiler of the common construction.
The stains which come out upon maddered goods, in consequence of
defective bleaching, are called in this country _spangs_. Their origin
is such as I have described above, as the following statement of facts
will show. The weaver of calicoes receives frequently a fine warp so
tender from bad spinning or bad staple in the cotton, that it will not
bear the ordinary strain of the heddles, or friction of the shuttle and
reed, and he is obliged to throw in as much weft as will compensate for
the weakness or thinness of the warp, and make a good marketable cloth.
He of course tries to gain his end at the least expense of time and
labour. Hence when his paste dressing becomes dry and stiff, he has
recourse to such greasy lubricants as he can most cheaply procure; which
are commonly either tallow or butter in a rancid state, but the former
being the lowest priced is preferred. Accordingly, the weaver, having
heated a lump of iron, applies it to a piece of tallow held over the
warp in the loom, and causes the melted fat to drop in patches upon the
yarns, which he afterwards spreads more evenly by his brush. It is
obvious, however, that the grease must be very irregularly applied in
this way, and be particularly thick on certain spots. This irregularity
seldom fails to appear when the goods are bleached or dyed by the common
routine of work. Printed calicoes examined by a skilful eye, will be
often seen to be stained with large blotches evidently occasioned by
this vile practice of the weaver. The ordinary workmen call these
_copper_ stains, believing them to be communicated in the dyeing copper.
Such stains on the cloth are extremely injurious in dyeing with the
indigo vat. The following plan is adopted by some Scotch bleachers with
the effect, it is said, of effectually counteracting spangs from grease.
The goods having been singed and steeped in pure water, as is customary
in common bleaching, they are passed through a pair of rollers to press
out the impurities which have been loosened by the steeping. It must
here, however, be observed, that where the expense of one extra drying
can be afforded, the process might be very much improved by steeping the
brown calicoes for thirty or forty hours before singeing, because this
would separate much of that impurity which usually becomes fixed in the
stuff on its being passed over the hot cylinders. When the pieces have
been thus singed, steeped, and pressed, they are boiled four times, ten
or twelve hours at each time, in a solution of caustic potash, of the
specific gravity of from 1·0127 to 1·0156, washing them carefully and
thoroughly in pure water between each of these boilings. They are then
immersed in a solution of the chloride of potash, originally of the
strength of 1·0625, and afterwards reduced with twenty-four times its
measure with water.
When the preparation is good, these proportions will whiten cotton goods
completely in eight hours. In this steep they are, however, generally
suffered to remain twelve hours. It has been supposed that the common
bleaching liquor (chloride of lime) cannot, without injury, be
substituted for chloride of potash, but I believe this to be a mistake.
Some printers take the pieces from this solution, and, while wet, lay
them upon the grass, and there expose them to the sun and weather for
two or three days. They are thence removed to the sours, made of the
specific gravity of about 1·0254 at the temperature of 110° of
Fahrenheit. In bleaching common goods, and such as are not designed for
the best printing, the specific gravity of the sours is varied from that
of 1·0146 to that of 1·0238, if weighed when they become of the
temperature of the atmosphere. In these they are suffered to lie for
five or six hours, after which they are taken to the dash-wheel and
washed thoroughly. When this operation is finished, they are submitted
to four more boilings as before, with a solution of caustic potash;
taking care to wash well between each of these boilings. Sometimes
pearl-ash, made caustic, is used for the last of these boilings, lest
the sulphur, which always exists in the potashes of commerce, should
impair the whites. They are next immersed in the diluted chloride of
potash, of the strength before mentioned; after which they are well
washed in pure water, and then winched for half an hour in common sours.
The last process is that of careful washing in plenty of clean water,
after which they are not put into the stove, but are immediately hung up
in the airing sheds to dry gradually. The water must be good, and
abundant.
The number of operations, as here described, is great; but I know of no
other mode of procedure by which perfect bleaching is so likely to be
effected at all times and in all seasons, without disappointment. It
must here be remarked, that, for the best purposes of printing, it would
not be sufficient to take goods which have been bleached in the common
way and finish these by the better process; because the sulphate of lime
deposited in the cloth by that operation will be apt to spoil them for
madder colours; at least, a printer who is curious in his business would
hesitate to work up such cloth.
_Bucking or Bowking._--This is one of the most important operations in
the bleaching of both cotton and linen goods. There are several methods
whereby this process is carried on; but of these we shall select only
two, distinguishing them as the old and new method of bucking. In the
former way, the cloths have been steeped in the alkaline lye, as before
described, and afterwards well washed, are regularly arranged in a large
wooden vat, or kieve; a boiler of sufficient capacity is then filled
with caustic alkaline lye, which is heated to the temperature of blood.
The boiler is then emptied by a stop-cock upon the linens in the kieve,
until they are covered with the liquor. After having remained on the
cloth for some time, it is run off by a stop-cock, at the bottom of the
kieve, into an iron boiler sunk in the ground, from whence it is raised
into the boiler by a pump. The heat is now elevated to a higher
temperature, and the lye again run upon the goods in the kieve; from
whence it is returned into the boiler, as before described: and these
operations are continued, always increasing the heat, until the alkaline
lye is completely saturated with the colouring matter taken from the
cloth, which is known by its having acquired a completely offensive
smell, and losing its causticity.
When we consider the effect which heated liquids have upon coloured
vegetable matter, we shall see the propriety of the temperature of the
alkaline lye being gradually increased. Thus, when vegetable substances
are hastily plunged into boiling liquids, the colouring matter, in place
of being extracted, is, by this higher temperature, fixed into them. It
is on this principle that a cook acts in the culinary art, when the
green colour of vegetables is intended to be preserved: in place of
putting them into water when cold, they are kept back until the water is
boiling; because it is well known that, in the former case, the green
colour would be entirely extracted, whereas, when the vegetables are not
infused until the water is boiling, the colour is completely preserved
or fixed. On the same principle, when the temperature of the alkaline
lye is gradually raised, the extractive and colouring matter is more
effectually taken from the cloth; and the case is reversed when the lye
is applied at the boiling temperature: so much so, that linen which has
been so unfortunate as to meet with this treatment, can never be brought
to a good white.
When the alkaline lye is saturated with colouring matter, it is run off
as unfit for further use in this operation; but, were the goods to be
instantly taken out of the kieve, and carried to be washed in the
dash-wheel while hot, a certain portion of the colouring matter would be
again fixed into them, which is extremely difficult to eradicate. In
order to prevent this, the most approved bleachers run warm water upon
the cloth as soon as the impure lye is run off: this combines with and
carries off part of the remaining impurities. A stream of water is then
allowed to run upon the cloth in the kieve, until it comes off almost
transparent. The goods are now to be taken to the wash-stocks, or to the
dash-wheel, to be further cleaned, with the greatest efficacy.
The improved mode of bowking was the invention of Mr. John Laurie, a
native of Glasgow. It is now practised by many bleachers in Lancashire,
some on more perfect plans than others; but we shall give the
description of the kind of apparatus approved of by those whose
experience and skill have rendered them the most competent judges.
[Illustration: 122]
In _fig._ 122., A B C D is the wooden kieve, or kier, containing the
cloth; C E F D represents the cast-iron boiler; G G, the pump; _g_ K,
the pipe of communication between the kieve and the boiler. This pipe
has a valve on each of its extremities: that on the upper extremity,
when shut, prevents the lye from running into the boiler, and is
regulated by the attendant by means of the rod and handle _g_ B. The
valve at K admits the lye; but, opening inwards, it prevents the steam
from escaping through the pipe _g_ K. The boiler has a steam-tight iron
cover, _g_ L; and at C D, in the kieve, is a wooden grating, a small
distance above the cover of the boiler.
At M O is a broad plate of metal, in order to spread the lye over the
cloth. It is hardly necessary to say that the boiler has a furnace, as
usual, for similar purposes.
While the lye is at a low temperature, the pump is worked by the mill or
steam-engine. When it is sufficiently heated, the elasticity of the
steam forces it up through the valves of the pump, in which case it is
disjoined from the moving power.
N P is a copper spout, which is removed at the time of taking the cloth
out of the kieve.
[Illustration: 123]
The boilers A, _fig._ 123., used in bleaching, are of the common form,
having a stopcock, H G, at bottom, for running off the waste lye. They
are commonly made of cast iron, and are capable of containing from 300
to 600 gallons of water, according to the extent of the business done.
In order that the capacity of the boilers may be enlarged, they are
formed so as to admit of a crib of wood, strongly hooped, or, what is
preferable, of cast iron, to be fixed to the upper rim or edge of it. To
keep the goods from the bottom, where the heat acts most forcibly, a
strong iron ring, covered with netting made of stout rope, C, is allowed
to rest six or eight inches above the bottom of the boiler. Four double
ropes are attached to the ring E, for withdrawing the goods when
sufficiently boiled, which have each an eye for admitting hooks from the
running tackle of a crane. Where more boilers than one are employed, the
crane is so placed, that, in the range of its sweep, it may withdraw the
goods from any of them. For this purpose, the crane turns on pivots at
top and bottom; and the goods are raised or lowered at pleasure, with
double pulleys and sheaves, by means of a cylinder moved by cast-iron
wheels. The lid is secured by the screw bolts D D, and rings B B. F is a
safety valve.
The efficacy of Laurie’s bowking apparatus is remarkable. While the heat
is gradually rising, a current of fresh lye is constantly presented to
the different surfaces for saturating the goods, so as to increase its
detersive powers. Besides, the manner in which the apparatus is worked,
first by the water-wheel or steam-engine, and then by its intrinsic
operation, puts it completely out of the power of servants to slight the
work; not to speak of the great saving of alkali, which, in many cases,
has been found to amount to 25 per cent.
[Illustration: 124 125 126]
A simple modification of the bowking apparatus is shown in _figs._ 124,
125, 126.; the first being a vertical section, the second, a horizontal
section in the line _x_ of the first. It consists of two parts: the
upper wide part, _a a_, serves for the reception of the goods, and the
lower or pot, _b_, for holding the lye; _c c_ is an iron grating, shown
apart in _fig._ 126. The grating has numerous square apertures in the
middle of the disc, to which the rising pipe _d_ is screwed fast. The
upper cylinder is formed of cast iron, or of sheet iron well rivetted at
the edges; or sometimes of wood, this being secured at its under edge
into a groove in the top edge of the lye-pot. The mouth of the cylinder
is constructed usually of sheet iron. _e e_ is the fire-grate, whose
upper surface is shown in _fig._ 125.: it is made of cast iron, in three
pieces. The flame is parted at _f_, and passes through the two apertures
_g g_, into the flues _h h_, so as to play round the pot, as is visible
in _fig._ 125.; and escapes by two outlets into the chimney. The
apertures _i i_ serve for occasionally cleaning out the flues _h h_, and
are, at other times, shut with an iron plate. In the partition _f_,
which separates the two openings _g g_, and the flues _h h_, running
round the pot, there is a circular space at the point marked with _k_,
_fig._ 125., in which the large pipe for discharging the waste lye is
lodged. The upper large cylinder should be encased in wood, with an
intermediate space filled with sawdust, to confine the heat. The action
of this apparatus is exactly the same as of that already explained.
Besides the boiling, bucking, and other apparatus above described, the
machinery and utensils used in bleaching are various, according to the
business done by the bleacher. When linen or heavy cotton cloths are
whitened, and the business is carried on to a considerable extent, the
machines are both complicated and expensive. They consist chiefly of a
water-wheel, sufficiently powerful for giving motion to the wash-stocks,
dash-wheels, squeezers, &c., with any other operations where power is
required.
[Illustration: 127 128]
_Figs._ 127, 128. represent a pair of wash-stocks. A A are called the
stocks, or feet. They are suspended on iron pivots at B, and receive
their motion from wipers on the revolving-shaft C. The cloth is laid in
at D, and, by the alternate strokes of the feet, and the curved form of
the turnhead E, the cloth is washed and gradually turned. At the same
time, an abundant stream of water rushes on the cloth throughout holes
in the upper part of the turnhead. Wash-stocks are much used in Scotland
and in Ireland. In the latter country, they are often made with double
feet, suspended above and below two turnheads, and wrought with cranks
instead of wipers. Wash-stocks, properly constructed, make from 24 to 30
strokes per minute.
This mode of washing is now entirely given up in Lancashire, where a
preference is given to what are called dash-wheels and squeezers. The
dash are small water-wheels, the inside of which is divided into four
compartments, and closed up, leaving only a hole in each compartment for
putting in the cloth.
There are, besides, smaller openings for the free admission and egress
of the water employed in cleansing. The cloth, by the motion of the
wheel, is raised up in one part of the revolution of the wheel; while,
by its own weight, it falls in another. This kind of motion is very
effectual in washing the cloth, while, at the same time, it does not
injure its strength. The plan, however, where economy of water is of any
importance, is very objectionable; because the wheel must move at by far
too great a velocity to act to advantage as a water-wheel.
[Illustration: 129 130]
The wash or dash-wheel, now driven by power in all good bleach and
print-works, is represented in _fig._ 129., upon the left side in a back
view, and upon the right side in a front view (the sketch being halved).
_Fig._ 130. is a ground plan.
_a a_ is the washing-wheel; _b b_ its shaft-ends; _c c_ their brass
bearings or plummer-blocks, supported upon the iron pillars _d d_. The
frame is made of strong beams of wood, _e e_, bound together by cross
bars with mortises. _f f_, two of the circular apertures, each leading
to a quadrantal compartment within the dash-wheel. In the back view (the
left-hand half of the figure) the brass grating _g g_, of a curvilinear
form, is seen, through which the jets of water are admitted into the
cavity of the wheel; _h h_, are the round orifices, through which the
foul water runs off, as each quadrant passes the lower part of its
revolution; _i_, a water-pipe, with a stop-cock for regulating the
washing-jets; _k k_, the lever for throwing the driving-crab _l_, or
coupling-box, into or out of geer with the shaft of the wheel. This
machine is so constructed, that the water-cock is opened or shut by the
same leverage which throws the wheel into or out of geer. _m_, a wheel,
fixed upon the round extremity of the shaft of the dash-wheel, which
works into the toothed pinion connected with the prime mover. When the
end of the lever _k_, whose fork embraces the coupling-box upon the
square part of the shaft, is pushed forwards or backwards, it shifts the
clutch into or out of geer with the toothed wheel _m_. In the latter
case, this wheel turns with its pinion without affecting the dash-wheel.
_n n_, holdfasts fixed upon the wooden frame, to which the boards _o o_
are attached, for preventing the water from being thrown about by the
centrifugal force.
The dash-wheel is generally from 6 to 7 feet in diameter, about 30
inches wide, and requires the power of about two horses to drive it.
From one to two pieces of calico may be done at once in each quadrantal
compartment, in the course of 8 or 10 minutes; hence, in a day of 13
hours, with two such wheels 1200 pieces of yard-wide goods may be
washed.
After the process of washing by the dash-wheel, the water is expressed
from the cloth by means of the squeezers already described.
_Bleaching of Linen._--Linen contains much more colouring matter than
cotton. The former loses nearly a third of its weight, while the latter
loses not more than a twentieth. The fibres of flax possess, in the
natural condition, a light gray, yellow, or blond colour. By the
operation of rotting, or, as it is commonly called, water-retting, which
is employed to enable the textile filaments to be separated from the
boon, or woody matter, the colour becomes darker, and, in consequence
probably of the putrefaction of the green matter of the bark, the
colouring substance appears. Hence, flax prepared without rotting is
much paler, and its colouring matter may be in a great measure removed
by washing with soap, leaving the filaments nearly white. Mr. James Lee
obtained a patent in 1812, as having discovered that the process of
steeping and dew-retting is unnecessary, and that flax and hemp will not
only dress, but will produce an equal if not greater quantity of more
durable fibre, when cleaned in the dry way. Mr. Lee stated that, when
hemp or flax plants are ripe, the farmer has nothing more to do than to
pull, spread, and dry them in the sun, and then to break them by proper
machinery. This promising improvement has apparently come to nought,
having been many years abandoned by the patentee himself, though he was
favoured with a special act of parliament, which permitted the
specification of his patent to remain sealed up for seven years,
contrary to the general practice in such cases.
The substance which gives steeped flax its peculiar tint is insoluble in
boiling water, in acids, and in alkalies; but it possesses the property
of dissolving in caustic or carbonated alkaline lyes, when it has
possessed the means of dehydrogenation by previous exposure to oxygen.
Hemp is, in this respect, analogous to flax. The bleaching of both
depends upon this action of oxygen, and upon the removal of the
acidified dye, by means of an alkali. This process is effected generally
by the influence of air in combination with light and moisture acting on
the linen cloth laid upon the grass: but chlorine will effect the same
object more expeditiously. In no case, however, is it possible to
acidify the colour completely at once, but there must be many alternate
exposures to oxygen or chlorine, and alkali, before the flax becomes
white. It is this circumstance alone which renders the bleaching of
linen an apparently complicated business.
Having made these preliminary observations with regard to the method of
applying the alkaline lyes used in bleaching linen cloth, I shall now
bring the whole into one point of view, by detailing the connection of
these processes, as carried on at a bleach-field, which has uniformly
been successful in returning the cloth of a good white, and has
otherwise given satisfaction to its employers; and I shall only remark,
that I by no means hold it up as the best process which may be employed,
as every experienced bleacher knows that processes must be varied, not
only according to existing circumstances, but also according to the
nature of the linens operated upon.
In order to avoid repetition, where washing is mentioned, it must always
be understood that the linen is taken to the wash-stocks or dash-wheel,
and washed well in them for some hours. This part of the work can never
be overdone; and on its being properly executed between every part of
the bucking, boiling, steeping in the chloride of lime solution, and
souring, not a little of the success of bleaching depends. By exposure
is meant, that the linen cloth is taken and spread upon the bleach-green
for four, six, or eight days, according as the routine of business calls
for the return of the cloth, in order to undergo further operations.
A parcel of goods consists of 360 pieces of those linens which are
called Britannias. Each piece is 35 yards long; and they weigh, on an
average, 10 lbs. each; the weight of the parcel is, in consequence,
about 3600 lbs. avoirdupois weight. The linens are first washed, and
then steeped in waste alkaline lye, as formerly described under these
processes; they then undergo the following operations:--
1st, Bucked with 60 lbs. pearl-ashes, washed, exposed on the field.
2d, Ditto 80 ditto ditto ditto ditto.
3d, Ditto 90 potashes ditto ditto ditto.
4th, Ditto 80 ditto ditto ditto ditto.
5th, Ditto 80 pearl-ashes, ditto ditto ditto.
6th, Ditto 50 ditto ditto ditto ditto.
7th, Ditto 70 ditto ditto ditto ditto.
8th, Ditto 70 ditto ditto ditto ditto.
9th, Soured one night in dilute sulphuric acid, washed.
10th, Bucked with 50 lbs. pearl-ashes, washed, exposed on the field.
11th, Immersed in the chloride of potash or lime 12 hours.
12th, Boiled with 30 lbs. pearl ashes, washed, exposed on the field.
13th, Ditto 30 ditto ditto ditto ditto.
14th, Soured, washed.
The linens are then taken to the rubbing-board, and well rubbed with a
strong lather of black soap, after which they are well washed in pure
spring water. At this period they are carefully examined, and those
which are fully bleached are laid aside to be blued, and made up for the
market; while those which are not fully white are returned to be boiled,
and steeped in the chloride of lime or potash; then soured, until they
are fully white.
By the above process, 690 lbs. weight of alkali is taken to bleach 360
pieces of linen, each piece consisting of 35 yards in length; so that
the expenditure of alkali would be somewhat less than 2 lbs. for each
piece, were it not that some parts of the linens are not fully whitened,
as above noted. Two pounds of alkali may therefore be stated as the
average quantity employed for bleaching each piece of goods.
The method of bleaching linens in Ireland is similar to the foregoing;
any alteration in the process depending upon the judgment of the
bleacher in increasing or diminishing the quantity of alkali used. But
it is common, at most bleach-fields, to steep the linens in the chloride
of lime or potash at an early stage of the process, or after the goods
have undergone the fifth or sixth operation of bucking. By this means
those parts of the flax which are most difficult to bleach are more
easily acted upon by the alkali; and, as before noticed, souring early
in very dilute sulphuric acid, assists greatly in forwarding the
whitening of the linens. Mr. Grimshaw, calico-printer, near Belfast, was
the first who recommended early souring, which has since been very
generally adopted.
_The bleaching of Silk._--Silk in its raw state, as spun by the worm, is
either white or yellow of various shades, and is covered with a varnish,
which gives it stiffness and a degree of elasticity. For the greater
number of purposes to which silk is applied, it must be deprived of this
native covering, which was long considered to be a sort of gum. The
operation by which this colouring matter is removed is called scouring,
cleansing, or boiling. A great many different processes have been
proposed for freeing the silk fibres from all foreign impurities, and
for giving it the utmost whiteness, lustre, and pliancy; but none of the
new plans has superseded, with any advantage, the one practised of old,
which consists essentially in steeping the silk in a warm solution of
soap; a circumstance placed beyond all doubt by the interesting
experiments of M. Roard. The alkalies, or alkaline salts, act in a
marked manner upon the varnish of silk, and effect its complete
solution; the prolonged agency of boiling water, alone answers the same
purpose; but nothing agrees so well with the nature of silk, and
preserves its brilliancy and suppleness so perfectly, as a rapid boil
with soap-water. It would appear, however, that the Chinese do not
employ this method, but something that is preferable. Probably the
superior beauty of their white silk may be owing to the superiority of
the raw material.
The most ancient method of scouring silk consists of three operations.
For the first, or the _ungumming_, thirty per cent. of soap is first of
all dissolved in clean river water by a boiling heat; then the
temperature is lowered by the addition of a little cold water, by
withdrawing the fire, or at least by damping it. The hanks of silk
suspended upon horizontal poles over the boiler, are now plunged into
the soapy solution, kept at a heat somewhat under ebullition, which is
an essential point; for if hotter, the soap would attack the substance
of the silk, and not only dissolve a portion of it, but deprive the
whole of its lustre. The portions of the hanks plunged in the bath get
scoured by degrees; the varnish and the colouring matter come away, and
the silk assumes its proper whiteness and pliancy. Whenever this point
is attained, the hanks are turned round upon the poles, so that the
portion formerly in the air may be also subjected to the bath. As soon
as the whole is completely ungummed, they are taken out, wrung by the
peg, and shaken out; after which, the next step, called the _boil_, is
commenced. Into bags of coarse canvass, called _pockets_, about 25 lbs.
or 35 lbs. of ungummed silk are enclosed, and put into a similar bath
with the preceding, but with a smaller proportion of soap, which may
therefore be raised to the boiling point without any danger of
destroying the silk. The ebullition is to be kept up for an hour and a
half, during which time the bags must be frequently stirred, lest those
near the bottom should suffer an undue degree of heat. The silk
experiences in these two operations a loss of about 25 per cent. of its
weight.
The third and last scouring operation is intended to give the silk a
slight tinge, which renders the white more agreeable, and better
adapted to its various uses in trade. In this way we distinguish the
China white, which has a faint cast of red, the silver white, the azure
white, and the thread white. To produce these different shades, we begin
by preparing a soap-water so strong as to lather by agitation; we then
add to it, for the China white, a little annotto, mixing it carefully
in; and then passing the silk properly through it, till it has acquired
the wished for tint. As to the other shades, we need only azure them
more or less with a fine indigo, which has been previously washed
several times in hot water, and reduced to powder in a mortar. It is
then diffused through boiling water, allowed to settle for a few
minutes, and the supernatant liquid, which contains only the finer
particles, is added to the soap bath, in such proportion as may be
requisite. The silk, on being taken out of this bath, must be wrung
well, and stretched upon perches to dry; after which it is introduced
into the sulphuring chamber, if it is to be made use of in the white
state. At Lyons, however, no soap is employed at the third operation:
after the boil, the silk is washed, sulphured, and azured, by passing
through very clear river water properly blued.
The silks intended for the manufacture of blonds and gauzes are not
subjected to the ordinary scouring process, because it is essential, in
these cases, for them to preserve their natural stiffness. We must
therefore select the raw silk of China, or the whitest raw silks of
other countries; steep them, rince them in a bath of pure water, or in
one containing a little soap; wring them, expose them to the vapour of
sulphur, and then pass them through the azure water. Sometimes this
process is repeated.
Before the memoir of M. Roard appeared, extremely vague ideas were
entertained about the composition of the native varnish of silk. He has
shown that this substance, so far from being of a gummy nature, as had
been believed, may be rather compared to bees’ wax, with a species of
oil, and a colouring matter, which exists only in raw silks. It is
contained in them to the amount of from 23 to 24 per cent., and forms
the portion of weight which is lost in the _ungumming_. It possesses,
however, some of the properties of vegetable gums, though it differs
essentially as to others. In a dry mass, it is friable and has a
vitreous fracture; it is soluble in water, and affords a solution which
lathers like soap; but when thrown upon burning coals, it does not
soften like gum, but burns with the exhalation of a fetid odour. Its
solution, when left exposed to the open air, at first of a golden
yellow, becomes soon greenish, and ere long putrefies, as a solution of
animal matter would do in similar circumstances. M. Roard assures us
that the city of Lyons alone could furnish several thousand quintals of
this substance _per annum_, were it applicable to any useful purpose.
The yellow varnish is of a resinous nature, altogether insoluble in
water, very soluble in alcohol, and contains a little volatile oil,
which gives it a rank smell. The colour of this resin is easily
dissipated, either by exposure to the sun or by the action of chlorine:
it forms about one fifty-fifth of its weight.
Bees’ wax exists also in all the sorts of silk, even in that of China;
but the whiter the filaments, the less wax do they contain.
M. Roard has observed that, if the silk be exposed to the soap baths for
some time after it has been stripped of its foreign matters, it begins
to lose body, and has its valuable qualities impaired. It becomes dull,
stiff, and coloured in consequence of the solution more or less
considerable of its substance; a solution which takes place in all
liquids, and even in boiling water. It is for this reason that silks
cannot be alumed with heat; and that they lose some of their lustre in
being dyed brown, a colour which requires a boiling hot bath. The best
mode, therefore, of avoiding these inconveniences, is to boil the silks
in the soap-bath no longer than is absolutely necessary for the scouring
process, and to expose them in the various dyeing operations to as
moderate temperature as may be requisite to communicate the colour. When
silks are to be dyed, much less soap should be used in the cleansing,
and very little for the dark colours. According to M. Roard, raw silks,
white or yellow, may be completely scoured, in one hour, with 15 lbs. of
water for one of silk, and a suitable proportion of soap. The soap and
the silk should be put into the bath half an hour before its ebullition,
and the latter should be turned about frequently. The dull silks, in
which the varnish has already undergone some alteration, never acquire a
fine white until they are exposed to sulphureous acid gas. Exposure to
light has also a very good effect in whitening silks, and is had
recourse to, it is said, with advantage by the Chinese.
Carbonate of soda has been proposed to be used instead of soap in
scouring silk, but it has never come into use. The Abbé Collomb, in
1785, scoured silk by eight hours’ boiling in simple water, and he found
the silks bleached in this way to be stronger than by soap, but they are
not nearly so white. A patent has been taken out in England for
bleaching them by steam, of which an account will be found under the
article SILK.
It appears that the Chinese do not use soap in producing those fine
white silks which are imported into Europe. Michel de Grubbens who
resided long at Canton, saw and practised himself the operation there,
which he published in the Memoirs of the Academy of Stockholm in 1803.
It consists in preparing the silk with a species of white beans, smaller
than the Turkey beans, with some wheat flour, common salt, and water.
The proportions are 5 parts of beans, 5 of salt, 6 of flour, and 25 of
water, to form this vegetable bath. The beans must be previously washed.
It is difficult to discover what chemical action can occur between that
decoction and the varnish of raw silk; possibly some acid may be
developed, which may soften the gummy matter, and facilitate its
separation.
Baumé contrived a process which does not appear to have received the
sanction of experience, but which may put us in the right way. He
macerates the yellow raw silk in a mixture of alcohol at 36° (sp. gr.
0·837) and one thirty-second part of pure muriatic acid. At the end of
forty-eight hours, it is as white as possible, and the more so, the
better the quality of the silk. The loss which it suffers in this
menstruum is only one fortieth; showing that nothing but the colouring
matter is abstracted. The expense of this menstruum is the great
obstacle to Baumé’s process. The alcohol, however, might be in a very
great measure recovered, by saturating the acid with chalk, and
redistillation.
_Bleaching of Wool._--Wool, like the preceding fibrous matter, is
covered with a peculiar varnish, which impairs its qualities, and
prevents it from being employed in the raw state for the purposes to
which it is well adapted when it is scoured. The English give the name
_yolk_, and the French _suint_, to that native coat: it is a fatty
unctuous matter, of a strong smell, which apparently has its chief
origin in the cutaneous perspiration of the sheep; but which, by the
agency of external bodies, may have undergone some changes which modify
its constitution. It results from the experiments of M. Vauquelin, that
the _yolk_ is composed of several substances; namely, 1. a soap with
basis of potash, which constitutes the greater part of it; 2. of a
notable quantity of acetate of potash; 3. of a small quantity of
carbonate, and a trace of muriate, of potash; 4. of a little lime in an
unknown state of combination; 5. of a species of sebaceous matter, and
an animal substance to which the odour is due. There are several other
accidental matters present on sheep’s wool.
The proportion of yolk is variable in different kinds of wool, but in
general it is more abundant the finer the staple; the loss by scouring
being 45 per cent. for the finest wools, and 35 per cent. for the
coarse.
The yolk, on account of its soapy nature, dissolves readily in water,
with the exception of a little free fatty matter, which easily separates
from the filaments, and remains floating in the liquor. It would thence
appear sufficient to expose the wools to simple washing in a stream of
water; yet experience shows that this method never answers so well as
that usually adopted, which consists in steeping the wool for some time
in simple warm water, or in warm water mixed with a fourth of stale
urine. From 15 to 20 minutes of contact are sufficient in this case, if
we heat the bath as warm as the hand can bear it, and stir it well with
a rod. At the end of this time the wool may be taken out, set to drain,
then placed in large baskets, in order to be completely rinsed in a
stream of water.
It is generally supposed that putrid urine acts on the wool by the
ammonia which it contains, and that this serves to saponify the
remainder of the fatty matter not combined with the potash. M. Vauquelin
is not of this opinion, because he found that wool steeped in water,
with sal ammoniac and quick lime, is not better scoured than an equal
quantity of wool treated with mere water. He was hence led to conclude
that the good effects of putrefied urine might be ascribed to any thing
else besides the ammonia, and probably to the urea. Fresh urine contains
a free acid, which, by decomposing the potash soap of the yolk,
counteracts the scouring operation.
If wools are better scoured in a small quantity of water than in a great
stream, we can conceive that this circumstance must depend upon the
nature of the yolk which, in a concentrated solution, acts like a
saponaceous compound, and thus contributes to remove the free fatty
particles which adhere to the filaments. It should also be observed that
too long a continuance of the wool in the yolk water, hurts its quality
very much, by weakening its cohesion, causing the filaments to swell,
and even to split. It is said then to have lost its _nerve_. Another
circumstance in the scouring of wool, that should always be attended to,
is never to work the filaments together to such a degree as to occasion
their felting; but in agitating we must merely push them slowly round in
the vessel, or press them gently under the feet. Were it at all felted,
it would neither card nor spin well.
As the heat of boiling water is apt to decompose woollen fibres, we
should be careful never to raise the temperature of the scouring bath to
near this point, nor, in fact, to exceed 140° F. Some authors recommend
the use of alkaline or soapy baths for scouring wool, but practical
people do not deviate from the method above described.
When the washing is completed, all the wool which is to be sent white
into the market, must be exposed to the action of sulphurous acid,
either in a liquid or a gaseous state. In the latter case, sulphur is
burned in a close chamber, in which the wools are hung up or spread out;
in the former, the wools are plunged into water, moderately impregnated
with the acid. (See SULPHURING.) Exposure on the grass may also
contribute to the bleaching of wool. Some fraudulent dealers are accused
of dipping wools in butter-milk, or chalk and water, in order to whiten
them and increase their weight.
Wool is sometimes whitened in the fleece, and sometimes in the state of
yarn; the latter affording the best means of operating. It has been
observed that the wool cut from certain parts of the sheep, especially
from the groins, never bleaches well.
After sulphuring, the wool has a harsh crispy feel, which may be removed
by a weak soap bath. To this also the wool comber has recourse when he
wishes to cleanse and whiten his wools to the utmost. He generally uses
a soft or potash soap, and after the wool is well soaked in the warm
soap bath, with gentle pressure he wrings it well with the help of a
hook, fixed at the end of his washing tub, and hangs it up to dry.
_Bleaching of rags, and paste for paper making._--After the rags are
reduced to what is called half stuff, they should have the greater part
of the floating water run off, leaving just enough to form a stir-about
mass. Into this a clear solution of chloride of lime should be poured,
of such a strength as is suited to the colour of the rags, which should
have been previously sorted; and the engine is kept going so as to churn
the rags with the bleaching agent. After an hour, the water may be
returned upon the engine, and the washing of the paper resumed. From two
to four pounds of good chloride of lime are reckoned sufficient to
bleach one hundred weight of rags.
When the rags consist of dyed or printed cottons, after being well
washed and reduced to half stuff, they should be put into a large cask
or butt, supported horizontally by iron axles upon cradle bearings, so
that it may be made to revolve like a barrel-churn. For each hundred
weight of the coloured rags, take a solution containing from four to
eight pounds of chloride of lime; add it to the liquid mixture in the
butt along with half a pound of sulphuric acid for every pound of the
chloride; and after inserting the bung, or rather the square valve, set
the vessel in slow revolution backwards and forwards. In a short time
the rags will be colourless. The rags and paper paste ought to be very
well washed, to expel all the chlorine, and perhaps a little muriatic
acid might be used with advantage to dissolve out all the calcareous
matter, a portion of which is apt to remain in the paper, and to operate
injuriously upon both the pens and the ink. Some of the French paper
manufacturers bleach the paste with chlorine gas. Paper prepared from
such paste, well washed, is not apt to give a brown tint to maps, as
that carelessly bleached with chloride of lime is known to do.
BLENDE. (_Fr. and Germ._) Sulphuret of zinc, so named from the German
_blenden_ to dazzle, on account of its glistening aspect. It is called
black jack from its usual colour. Its lustre is pearly adamantine. Spec.
gravity from 3·7 to 4·2. It contains frequently iron, copper, arsenic,
cadmium and silver, all associated with sulphur. It is worked up partly
into metallic zinc, and partly into the sulphate of zinc, or white
vitriol. It consists of 66·72 zinc, and 33·28 sulphur; being nearly by
weight as two to one. See ZINC.
BLOCK MANUFACTURE. Though the making of ships’ blocks belongs rather to
a dictionary of engineering than of manufactures, it may be expected
that I should give some account of the automatic machinery for making
blocks, so admirably devised and mounted by M. I. Brunel, Esq. for the
British navy, in the dock-yard of Portsmouth.
The series of machines and operations are as follows:--
1. _The straight cross cutting saw._--The log is placed horizontally on
a very low bench which is continued through the window of the mill into
the yard. The saw is exactly over the place where the log is to be
divided. It is let down, and suffered to rest with its teeth upon the
log, the back still being in the cleft of the guide. The crank being set
in motion, the saw reciprocates backwards and forwards with exactly the
same motion as if worked by a carpenter, and quickly cuts through the
tree. When it first begins to cut, its back is in the cleft in the
guide, and this causes it to move in a straight line; but before it gets
out of the guide, it is so deep in the wood as to guide itself: for in
cutting across the grain of the wood, it has no tendency to be diverted
from its true line by the irregular grain. When the saw has descended
through the tree, its handle is caught in a fixed stop, to prevent its
cutting the bench. The machine is thrown out of geer, the attendant
lifts up the saw by a rope, removes the block cut off, and advances the
tree to receive a fresh cut.
2. _The circular cross-cutting saw._--This saw possesses universal
motion; but the axis is always parallel to itself, and the saw in the
same plane. It can be readily raised or lowered, by inclining the upper
frame on its axis; and to move it sidewise, the saw frame must swing
sidewise on its joints, which connect it with the upper frame. These
movements are effected by two winches, each furnished with a pair of
equal pinions, working a pair of racks fixed upon two long poles. The
spindles of these winches are fixed in two vertical posts, which
support the axis of the upper frame. One of these pairs of poles is
jointed to the extreme end of the upper frame; therefore by turning the
handle belonging to them, the frame and saw is elevated or depressed; in
like manner, the other pair is attached to the lower part of the saw
frame, so that the saw can be moved sidewise by means of their handles,
which then swing the saw from its vertical position.
These two handles give the attendant a complete command of the saw,
which we suppose to be in rapid motion, the tree being brought forward
and properly fixed. By one handle, he draws the saw against one side of
the tree, which is thus cut into, (perhaps half through); now, by the
other handle, he raises the saw up, and by the first-mentioned handle he
draws it across the top of the tree, and cuts it half through from the
upper side; he then depresses the saw and cuts half through from the
next side; and lastly a trifling cut of the saw, at the lower side,
completely divides the tree, which is then advanced to take another cut.
_The great reciprocating saw_ is on the same principle as the saw mill
in common use in America.
3. _The circular ripping saw_ is a thin circular plate of steel, with
teeth similar to those of a pit saw, formed in its periphery. It is
fixed to a spindle placed horizontally, at a small distance beneath the
surface of a bench or table, so that the saw projects through a crevice
a few inches above the bench. The spindle being supported in proper
collars, has a rapid rotatory motion communicated to it by a pulley on
the opposite end, round which an endless strap is passed from a drum
placed overhead in the mill. The block cut by the preceding machine,
from the end of the tree, is placed with one of the sides flat upon the
bench, and thus slides forward against the revolving saw which cuts the
wood with a rapidity incredible to any one who has not seen these or
similar machines.
[Illustration: 131 132]
4. _Boring machine._--The blocks, prepared by the foregoing saws, are
placed in the machine represented in _fig._ 131. This machine has an
iron frame, A A, with three legs, beneath which the block is introduced,
and the screw near B being forced down upon it, confines it precisely in
the proper spot to receive the borers D and E. This spot is determined
by a piece of metal fixed perpendicularly just beneath the point of the
borer E, shown separately on the ground at X; this piece of metal
adjusts the position for the borer D, and its height is regulated by
resting on the head of the screw _x_, which fastens the piece X down to
the frame. The sides of the block are kept in a parallel position, by
being applied against the heads of three screws tapped into the double
leg of the frame A. The borer D is adapted to bore the hole for the
centre pin in a direction exactly perpendicular to the surface resting
against the three screws; the other, at E, perforates the holes for the
commencement of the sheave holes. Both borers are constructed in nearly
the same manner; they are screwed upon the ends of small mandrels,
mounted in frames similar to a lathe. These frames, G and H, are fitted
with sliders upon the angular edges of the flat broad bars, I and K. The
former of these is screwed fast to the frame; the latter is fixed upon a
frame of its own, moving on the centre screws, at L L, beneath the
principal frame of the machine. By this means the borer E can be moved
within certain limits, so as to bore holes in different positions. These
limits are determined by two screws, one of which is seen at _a_; the
other being on the opposite side is invisible. They are tapped through
fixed pieces projecting up from the frame. A projecting piece of metal,
from the under side of the slider K of the borer E, stops against the
ends of these screws, to limit the excursion of the borer. The frames
for both borers are brought up towards the block by means of levers M
and N. These are centered on a pin, at the opposite sides of the frame
of the machine, and have oblong grooves through them which receive screw
pins, fixed into the frames G and H, beneath the pulleys P P, which give
motion to the spindles.
5. _The mortising machine_ is a beautiful piece of mechanism, but too
complicated for description within the limits prescribed to this
article.
6. _The corner saw_, _fig._ 132., consists of a mandrel, mounted in a
frame A, and, carrying a circular saw L upon the extreme end of it. This
mandrel and its frame being exactly similar to those at G and H _fig._
131., does not require a separate view, although it is hid behind the
saw, except the end of the screw, marked A. This frame is screwed down
upon the frame B B of the machine, which is supported upon four columns.
C C, D D, is an inclined bench, or a kind of trough, in which a block is
laid, as at E, being supported on its edge by the plane C C of this
bench, and its end kept up to its position by the other part of the
bench D D.
By sliding the block along this bench, it is applied to the saw, which
cuts off its angles, as is evident from the figure, and prepares it for
the shaping engine. All the four angles are cut off in succession, by
applying its different sides to the trough or bench. In the figure, two
of them are drawn as being cut, and the third is just marked by the saw.
This machine is readily adapted to different sizes of blocks, by the
simple expedient of laying pieces of wood of different thickness against
the plane D D, so as to fill it up, and keep the block nearer to or
farther from the saw; for all the blocks are required to be cut at the
same angle, though, of course, a larger piece is to be cut from large
than from small blocks. The block reduced to the state of E is now taken
to
7. _The shaping machine._--A great deal of the apparent complication of
this figure arises from the iron cage, which is provided to defend the
workmen, lest the blocks, which are revolving in the circles, or chuck,
with an immense velocity, should be loosened by the action of the tool,
and fly out by their centrifugal force. Without this provision, the
consequences of such an accident would be dreadful, as the blocks would
be projected in all directions, with an inconceivable force.
8. _The scoring engine_ receives two blocks, as they come from the
shaping engine, and forms the groove round their longest diameters for
the reception of their ropes or straps, as represented in the two snatch
blocks and double block, under _figs._ 131, 132.
[Illustration: 133]
A, B, _fig._ 133., represent the above two blocks, each held between two
small pillars _a_, (the other pillar is hid behind the block) fixed in a
strong plate D, and pressed against the pillars by a screw _b_, which
acts on a clamp _d_. Over the blocks a pair of circular planes or
cutters E E, are situated, both being fixed on the same spindle, which
is turned by a pulley in the middle of it. The spindle is fitted in a
frame F F, moving in centres at _e e_, so as to rise and fall when
moved by a handle _f_. This brings the cutters down upon the blocks; and
the depth to which they can cut is regulated by a curved shape _g_,
fixed by screws upon the plate D, between the blocks. Upon this rests a
curved piece of metal _h_, fixed to the frame F, and inclosing, but not
touching, the pulley. To admit the cutters to traverse the whole length
of the blocks, the plate D, (or rather a frame beneath it,) is sustained
between the points of two centres. Screws are seen at _l_, on these
centres. The frame inclines when the handle L is depressed. At M is a
lever, with a weight at the end of it, counterbalancing the weight of
the blocks, and plate D, all which are above the centre on which they
move. The frame F is also provided with a counterpoise to balance the
cutters, &c. The cutters E E are circular wheels of brass, with round
edges. Each has two notches in its circumference, at opposite sides; and
in these notches chisels are fixed by screws, to project beyond the rim
of the wheel, in the manner of a plane iron before its face.
This machine is used as follows:--In order to fix the block, it is
pressed between the two pins (only one of which at _a_, can be seen in
this view), and the clamp _d_, screwed up against it, so as just to hold
the block, but no more. The clamp has two claws, as is seen in the
figure, each furnished with a ring entering the double prints previously
made, in the end of the block. These rings are partly cut away, leaving
only such a segment of each as will just retain the block, and the metal
between them is taken out to admit the cutter to operate between them,
or nearly so. In putting the blocks into this machine, the workman
applies the double prints to the ends of the claws of the clamps, but
takes care that the blocks are higher between the pins _a_ than they
should be; he then takes the handle _f_, and by it presses the cutters E
E, (which we suppose are standing still,) down upon the blocks,
depressing them between their pins at the same time, till the descent of
the cutters is stopped by the piece _h_ resting on the shape _g_. He now
turns the screws _b b_, to fix the blocks tight. The cutters being put
in motion cut the scores, which will be plainly seen by the mode of
adjustment just described, to be of no depth at the pin-hole; but by
depressing the handle L, so as to incline the blocks, and keeping the
cutters down upon their shape _g_, by the handle _f_, they will cut any
depth towards the ends of the blocks, which the shape _g_ admits.
By this means one quarter of the score is formed; the other is done by
turning both blocks together half round in this manner. The centres _l_
are not fitted into the plate D itself, but into a frame seen at R
beneath the plate, which is connected with it by a centre pin, exactly
midway between the two blocks A B. A spring catch, the end of which is
seen at _r_, confines them together; when this catch is pressed back,
the plate D can be turned about upon its centre pin, so as to change the
blocks, end for end, and bring the unscored quarters (_i. e._ over the
clamps) beneath the cutters; the workman taking the handles _f_ and L,
one in each hand, and pressing them down, cuts out the second quarter.
This might have been effected by simply lifting up the handle L; but in
that case the cutter would have struck against the grain of the wood, so
as to cut rather roughly; but by this ingenious device of reversing the
blocks, it always cuts clean and smooth, in the direction of the grain.
The third and fourth quarters of the score are cut by turning the other
sides of the blocks upwards, and repeating the above operation. The
shape _g_ can be removed, and another put in its place, for different
sizes and curves of block; but the same pins _a_, and holding clamps
_d_, will suit many different sizes.
By these machines the shells of the blocks are completely formed, and
they are next polished and finished by hand labour; but as this is
performed by tools and methods which are well known, it is needless to
enter into any explanation: the finishing required being only a
smoothing of the surfaces. The machines cut so perfectly true as to
require no wood to be removed in the finishing; but as they cut without
regard to the irregularity of the grain, knots, &c., it happens that
many parts are not so smooth as might be wished, and for this purpose
manual labour alone can be employed.
The lignum vitæ for the sheaves of the blocks, is cut across the grain
of the wood by two cross cutting saws, a circular and straight saw, as
before mentioned. These machines do not essentially differ in their
principle from the great cross cutting saws we have described, except
that the wood revolves while it is cutting, so that a small saw will
reach the centre of a large tree, and at the same time cut it truly
flat. The limits prescribed for our plates will not admit of giving
drawings of these machines, and the idea which could be derived from a
verbal description would not be materially different from the cross
cutting saws before mentioned. These machines cut off their plates for
the end of the tree, which are exactly the thickness for the intended
sheave. These pieces are of an irregular figure, and must be rounded and
centered in the crown saw.
[Illustration: 134]
9. _The crown saw_ is represented in _fig._ 134., where A is a pulley
revolving by means of an endless strap. It has the crown or trepan saw
_a_ fixed to it, by a screw cut within the piece, upon which the saw is
fixed, and which gives the ring or hoop of the saw sufficient stability
to perform its office. Both the pulleys and saw revolve together upon a
truly cylindrical tube _b_, which is stationary, being attached by a
flaunch _c_ to a fixed puppet B, and on this tube as an axis the saw and
pulley turn, and may be slid endwise by a collar fitted round the centre
piece of the pulley, and having two iron rods (only one of which can be
seen at _d_ in the figure), passing through holes made through the
flaunch and puppet B. When the saw is drawn back upon its central tube,
the end of the latter projects beyond the teeth of the saw. It is by
means of this fixed ring or tube within the saw, that the piece of wood
_e_ is supported during the operation of sawing, being pressed forcibly
against it by a screw D, acting through a puppet fixed to the frame of
the machine. At the end of this screw is a cup or bason which applies
itself to the piece of wood, so as to form a kind of vice, one side
being the end of the fixed tube, the other the cup at the end of the
screw D. Within the tube _b_ is a collar for supporting a central axis,
which is perfectly cylindrical. The other end of this axis, (seen at
_f_,) turns in a collar of the fixed puppet E. The central axis has a
pulley F, fixed on it, and giving it motion by a strap similar to the
other. Close to the latter pulley a collar _g_ is fitted on the centre
piece of the pulley, so as to slip round freely, but at the same time
confined to move endways with the pulley and its collar. This collar
receives the ends of the two iron rods _d_. The opposite ends of these
rods are, as above mentioned, connected by a similar collar, with the
pulley A of the saw _a_. By this connection, both the centre bit, which
is screwed into the end of the central axis _f_, and the saw sliding
upon the fixed tube _b_, are brought forward to the wood at the same
time, both being in rapid motion by their respective pulleys.
10. _The Coaking Engine._--This ingenious piece of machinery is used to
cut the three semicircular holes which surround the hole bored by the
crown saw, so as to produce a cavity in the centre of the disc.
11. _Face-turning Lathe._--The sheave is fixed against a flat chuck at
the end of a mandrel, by an universal chuck, similar to that in the
coaking engine, except that the centre pin, instead of having a nut, is
tapped into the flat chuck, and turned by a screw-driver.
BLOOD. (_Sang_, Fr.; _Blut_, Germ.) The liquid which circulates in the
arteries and veins of animals; bright red in the former and purple in
the latter, among all the tribes whose temperature is considerably
higher than that of the atmosphere. It consists 1. of a colourless
transparent solution of several substances in water; and 2. of red,
undissolved particles diffused through that solution. Its specific
gravity varies with the nature and health of the animal; being from
1·0527 to 1·0570 at 60° F. It has a saline sub-nauseous taste, and a
smell peculiar to each animal. When fresh drawn from the vessels, it
rapidly coagulates into a gelatinous mass, called the clot, cruor, or
crassamentum, from which after some time, a pale yellow fluid, passing
into yellowish green, oozes forth, called the _serum_. If the warm blood
be stirred with a bundle of twigs, as it flows from the veins, the
fibrine concretes, and forms long fibres and knots, while it retains its
usual appearance in other respects. The clot contains fibrine and
colouring matter in various proportions. Berzelius found in 100 parts of
the dried clot of blood, 35 parts of fibrine, 58 of colouring matter;
1·3 of carbonate of soda; 4 of an animal matter soluble in water, along
with some salts and fat. The specific gravity of the serum varies from
1·027 to 1·029. It forms about three fourths of the weight of the blood,
has an alkaline reaction, coagulates at 167° F. into a gelatinous mass,
and has for its leading constituent _albumen_ to the amount of 8 per
cent. besides fat, potash, soda, and salts of these bases. Blood does
not seem to contain any gelatine.
The red colouring matter called _hematine_, may be obtained from the
cruor by washing with cold water and filtering.
Blood was at one time largely employed for clarifying syrup, but it is
very sparingly used by the sugar refiners in Great Britain of the
present day. It may be dried by evaporation at a heat of 130° or 140°,
and in this state has been transported to the colonies for purifying
cane juice. It is an ingredient in certain adhesive cements, coarse
pigments for protecting walls from the weather, for making animal
charcoal in the Prussian blue works, and by an after process, a
decolouring carbon. It is used in some Turkey red dye-works. Blood is a
powerful manure.
BLOWING MACHINE. See IRON, METALLURGY, VENTILATION.
BLOWPIPE. (_Chalumeau_, Fr.; _Lothröhre_, Germ.) Jewellers,
mineralogists, chemists, enamellers, &c. make frequent use of a tube,
usually bent near the end, terminated with a finely pointed nozzle, for
blowing through the flame of a lamp, candle, or gas-jet, and producing
thereby a small conical flame possessing a very intense heat.
Modifications of blow pipes are made with jets of hydrogen, oxygen, or
the two gases mixed in due proportions.
BLUE DYES. (_Teint_, Germ. See ENAMEL.) The materials employed for this
purpose are indigo, Prussian blue, logwood, bilberry, (_vaccinium
myrtillus_,) elder berries, (_sambucus nigra_,) mulberries, privet
berries, (_ligustrum vulgare_,) and some other berries whose juice
becomes blue by the addition of a small portion of alkali, or of the
salts of copper. For dyeing with the first three articles, see them in
their alphabetical places. I shall here describe the other or minor blue
dyes.
To dye blue with such berries as the above, we boil one pound of them in
water, adding one ounce of alum, of copperas, and of blue vitriol, to
the decoction, or in their stead equal parts of verdegris and tartar,
and pass the stuffs a sufficient time through the liquor. When an iron
mordant alone is employed, a steel blue tint is obtained; and when a tin
one, a blue with a violet cast. The privet berries which have been
employed as sap colours by the card painters, may be extensively used in
the dyeing of silk. The berries of the African night-shade (_solanum
guineense_) have been of late years considerably applied to silk on the
continent in producing various shades of blue, violet, red, brown, &c.
but particularly violet. With alkalis and acids these berries have the
same habitudes as bilberries; the former turning them green, the latter
red. They usually come from Italy compressed in a dry cake, and are
infused in hot water. The infusion is merely filtered, and then employed
without any mordant, for dyeing silk, being kept at a warm temperature
by surrounding the bath vessel with hot water. The goods must be winced
for six hours through it in order to be saturated with colour; then they
are to be rinsed in running water and dried. One pound of silk requires
a pound and a half of the berry cake. In the residuary bath, other tints
of blue may be given. Sometimes the dyed silk is finished by running it
through a weak alum water. A colour approaching to indigo in permanence,
but which differs from it in being soluble in alkalis, though incapable
of similar disoxidizement, is the _gardenia genipa_ and _aculeata_ of
South America whose colourless juice becomes dark blue with contact of
air; and dyes stuffs, the skin, and nails, of an unchangeable deep blue
colour, but the juice must be applied in the colourless state.
BLUE PIGMENTS. Several metallic compounds possess a blue colour;
especially those of iron, cobalt, and molybdenum. The metallic pigments,
little if at all employed, but which may be found useful in particular
cases, are the molybdate of mercury, the hydro-sulphuret of tungsten,
the prussiate of tungsten, the molybdate of tin, the oxide of copper
darkened with ammonia, the silicate of copper, and a fine violet colour
formed from manganese and molybdenum. The blues of vegetable origin, in
common use, are indigo, litmus, and blue cakes. The blue pigments of a
metallic nature found in commerce are the following: _Prussian blue_;
_mountain blue_, a carbonate of copper mixed with more or less earthy
matter; _Bremen blue_, or _verditer_, a greenish blue colour obtained
from copper mixed with chalk or lime; _iron blue_, phosphate of iron,
little employed; _cobalt blue_, a colour obtained by calcining a salt of
cobalt with alumina or oxide of tin; _smalt_, a glass coloured with
cobalt and ground to a fine powder; _charcoal blue_, a deep shade
obtained by triturating carbonized vine stalks with an equal weight of
potash in a crucible till the mixture ceases to swell, then pouring it
upon a slab, putting it into water and saturating the alkali with
sulphuric acid. The liquor becomes blue, and lets fall a dark blue
precipitate, which becomes of a brilliant blue colour when heated.
Molybdenum blue is a combination of this metal, and oxide of tin or
phosphate of lime. It is employed both as a paint, and an enamel colour.
A blue may also be obtained by putting into molybdic acid, (made by
digesting sulphuret of molybdenum with nitric acid,) some filings of
tin, and a little muriatic acid. The tin deoxidizes the molybdic acid to
a certain degree, and converts it into the molybdous, which when
evaporated and heated with alumina recently precipitated, forms this
blue pigment. _Ultramarine_ is a beautiful blue pigment, which see.
BLUE VITRIOL; sulphate of copper.
BOMBAZINE. A worsted stuff, sometimes mixed with silk.
BONES. (_Os_, Fr.; _Knochen_, Germ.) They form the frame work of animal
bodies, commonly called the skeleton; upon which the soft parts are
suspended, or in which they are enclosed. Bones are invested with a
membrane styled the periosteum, which is composed of a dense tissue
affording glue; whence it is convertible into jelly, by ebullition with
water. Bones are not equally compact throughout their whole substance;
the long ones have tubes in their centres lined with a kind of
periosteum, of more importance to the life of the bones than even their
external coat. The flat, as well as the short and thick bones, exhibit
upon their surface an osseous mass of a dense nature, while their
interior presents a cavity divided into small cellules by their bony
partitions.
In reference to the composition of bones, we have to consider two
principal constituents; the living portion or the osseous cartilage, and
the inorganic or the earthy salts of the bones.
The osseous cartilage is obtained by suspending bones in a large vessel
full of dilute muriatic acid, and leaving it in a cool place at about
50° Fahr. for example. The acid dissolves the earthy salts of the bones
without perceptibly attacking the cartilage, which, at the end of a
short time, becomes soft and translucid, retaining the shape of the
bones; whenever the acid is saturated, before it has dissolved all the
earthy salts it should be renewed. The cartilage is to be next suspended
in cold water, which is to be frequently changed till it has removed all
the acidity. By drying, the cartilage shrinks a little, and assumes a
darker hue, but without losing its translucency. It becomes, at the same
time, hard and susceptible of breaking when bent, but it possesses great
strength.
This cartilage is composed entirely of a tissue passing into gelatine.
By boiling with water, it is very readily convertible into a glue, which
passes clear and colourless through the filter, leaving only a small
portion of fibrous matter insoluble by further boiling. This matter is
produced by the vessels which penetrate the cartilage, and carry
nourishment to the bone. We may observe all these phenomena in a very
instructive manner, by macerating a bone in dilute muriatic acid, till
it has lost about the half of its salts; then washing it with cold
water, next pouring boiling water upon it, leaving the whole in repose
for 24 hours, at a temperature a few degrees below 212° Fahr.
The cartilage, which has been stripped of its earthy salts dissolves,
but the small vessels which issue from the undecomposed portion of the
bone remain under the form of white plumes, if the water has received no
movement capable of crushing or breaking them. We may then easily
recognise them with a lens, but the slightest touch tears them, and
makes them fall to the bottom of the vessel in the form of a
precipitate; if we digest bones with strong hot muriatic acid so as to
accelerate their decomposition, a portion of the cartilage dissolves in
the acid with a manifest disengagement of carbonic acid gas, which
breaks the interior mass, and causes the half-softened bone to begin to
split into fibrous plates, separable in the direction of their length.
According to Marx these plates, when sufficiently thin, possess, like
scales of mica, the property of polarising light, a phenomenon which
becomes more beautiful still when we soak them with the essential oil of
the bark of the Laurus Cassia. The osseous cartilage is formed before
the earthy part. The long bones are then solid, and they become hollow
only in proportion as the earthy salts appear. In the new-born infant, a
large portion of the bones is but partially filled with these salts,
their deposition in cartilage takes place under certain invariable
_points of ossification_, and begins at a certain period after
conception, so that we may calculate the age of the foetus according to
the progress which ossification has made.
The earthy parts of bones are composed principally of the phosphate and
carbonate of lime in various proportions, variable in different animals,
and mixed with small quantities, equally variable, of phosphate of
magnesia and fluate of lime. The easiest means of procuring the earthy
salts of bones consists in burning them to whiteness, but the earthy
residuum procured in this manner, contains substances which did not
exist beforehand in the bones, and which did not form a part of their
earthy salts; as for example sulphate of soda, produced at the expense
of the sulphur of the bones and the alkaline carbonate, proceeding from
the cartilage with which it was combined. On the other hand, the greater
part of the lime has lost its carbonic acid. As the sulphuric acid is
the product of combustion, it is obvious that an acidulous solution of a
fresh bone can afford no precipitate with muriate of barytes. The
phosphate of lime contained in the bone-salts is a subphosphate,
consisting, according to Berzelius, of three prime equivalents of the
acid, and 8 of the base; or of 2,677 parts of the former, and 2,848 of
the latter. It is always obtained when we precipitate the phosphate of
lime by an excess of ammonia. When calcined bones are distilled in a
retort with their own weight of sulphuric acid, a little fluoric acid is
disengaged, and it acts on the surface of the glass. The following
analyses of the bones of men and horned cattle, are given by Berzelius.
They were dried after being stripped of their fat and periosteum till
they lost no more weight.
+-----------------------------------------+-----------+--------+
| |Human bone.|Ox bone.|
+-----------------------------------------+-----------+--------+
|Cartilage completely soluble in water | 32·17 } | 33·3 |
|Vessels | 1·13 } | |
|Subphosphate with a little fluate of lime| 53·04 | 57·35 |
|Carbonate of lime | 11·3 | 3·85 |
|Phosphate of magnesia | 1·16 | 2·05 |
|Soda with very little muriate of soda | 1·20 | 3·45 |
| | ------ | ------ |
| | 100·00 | 100·00 |
+-----------------------------------------+-----------+--------+
The most essential difference in the composition of these bones is that
those of man contain three times as much carbonate of lime as those of
the ox; and that the latter are richer in phosphate of lime and magnesia
in the same proportion. Fernandez de Barros has established a comparison
between the phosphate and carbonate of lime in the bones of different
animals. He found in 100 parts of earthy salt of the bones of the
following animals:--
+-----+------------------+-----------+
| |Phosphate of lime.|Carb. lime.|
+-----+------------------+-----------+
|Lion | 95·0 | 2·5 |
|Sheep| 80·0 | 19·3 |
|Hen | 88·9 | 10·4 |
|Frog | 95·2 | 2·4 |
|Fish | 91·9 | 5·3 |
+-----+------------------+-----------+
The bones of fish are divided into those which contain earthy salts and
those which have none, called cartilaginous fishes. The enamel of the
teeth is composed as follows:--
+-------------------------------------+-------------+----------+
| |Human enamel.|Ox enamel.|
+-------------------------------------+-------------+----------+
|Phosphate of lime with fluate of lime| 88·5 | 85·0 |
|Carbonate of lime | 8·0 | 7·1 |
|Phosphate of magnesia | 1·5 | 3·0 |
|Soda | 0·0 | 1·4 |
|Brown membranes attached to the tooth| 2·0 | 3·5 |
|alkali, water | | |
| | ----- | ----- |
| | 100·0 | 100·0 |
+-------------------------------------+-------------+----------+
In the arts, the bones are employed by turners, cutlers, manufacturers
of animal charcoal; and, when calcined, by assayers for making cupels.
In agriculture, they are employed as a manure, for which purpose they
should be ground in a mill, and the powder sowed along with the seeds in
a drill. It is supposed, in many cases, to increase the crop in weight
of grain and straw together, by from 40 to 50 per cent. In France, soup
is extensively made by dissolving bones in a steam-heat of two or three
days’ continuance. The shavings of hartshorn, which is a species of
bone, afford an elegant jelly: the shavings of calves’ bones may be used
in their stead.
Living bones acquire a red tinge when the animals receive madder with
their food; but they lose it when the madder is discontinued for some
time.
BONE BLACK (_Noir d’os_, Fr.; _Knochenschwartz_, Germ.), or _Animal
charcoal_, as it is less correctly called, is the black carbonaceous
substance into which bones are converted by calcination in close
vessels. This kind of charcoal has two principal applications; to
deprive various solutions, particularly syrups, of their colouring
matters, and to furnish a black pigment. The latter subject will be
treated of under IVORY BLACK.
The discovery of the antiputrescent and decolouring properties of
charcoal in general, is due to Lowitz, of Petersburg; but their
modifications have occupied the attention of many chemists since his
time. Kels published, in 1798, some essays on the discolouring of
indigo, saffron, madder, syrup, &c. by means of charcoal, but he
committed a mistake in supposing bone black to have less power than the
charcoal of wood. The first useful application of charcoal to the
purification of raw colonial sugar was made by M. Guillon, who brought
into the French markets considerable quantities of fine syrups, which he
discoloured by ground wood charcoal, and sold them to great advantage,
as much superior to the cassonades of that time. In 1811, M. Figuier, an
apothecary at Montpellier, published a note about animal charcoal,
showing that it blanched vinegars and wines with much more energy than
vegetable charcoal; and, lastly, in 1812, M. Derosnes proposed to
employ animal charcoal in the purification of syrups and sugar refining.
The quantities of bone black left in the retorts employed by MM. Payen,
for producing crude carbonate of ammonia, furnished abundant materials
for making the most satisfactory experiments, and enabled these
gentlemen soon to obtain ten per cent. more of refined sugar from the
raw article than had been formerly extracted, and to improve, at the
same time, the characters of the lumps, bastards, treacle, &c.
[Illustration: 135 136 137 138]
The calcination of bones is effected by two different systems of
apparatus; by heating them in a retort similar to that in which coal is
decomposed in the gas works, or in small pots piled up in a kiln. For
the description of the former, see GAS-LIGHT. On the second plan, the
bones, broken into pieces, are put into small cast-iron pots of the form
shown in _fig._ 135., about three eighths of an inch thick, two of which
are dexterously placed with their mouths in contact, and then luted
together with loam. The lip of the upper pot is made to slip inside of
the under one. These double vessels, containing together about fifty
pounds of bones, are arranged alongside, and over each other, in an
oven, like a potter’s kiln, till it be filled. The oven or kiln may be
either oblong or upright. The latter is represented in _fig._ 136, 137,
138. A is the fireplace or grate for the fuel; C C are the openings in
the dome of the furnace through which the flame flows; the divisions of
these orifices are shown in _fig._ 138. B is the wall of brick-work. D
the space in which the pots are distributed. E is the door by which the
workman carries in the pots, which is afterwards built up with fire
bricks, and plastered over with loam. This door is seen in _fig._ 136. F
F are the lateral flues for conveying the disengaged gases into the air.
[Illustration: 139 140]
_Fig._ 139. is a longitudinal section, and _fig._ 140. a ground plan of
a horizontal kiln for calcining bones. _a_ is the fire-chamber, lying
upon a level with the sole of the kiln; it is separated by a pillar _b_,
from the calcining hearth _c_. In the pillar or wall, several rows of
holes _d_, are left at different heights; _e_ is the entrance door; _f_,
the outlet vents for the gases, vapours, and smoke, into the chimney
_g_; _h_, a sliding damper-plate for regulating the admission of the air
into the fire in the space _a_.
By this arrangement the offensive emanations are partly consumed, and
partly carried off with the smoke. To destroy the smell completely, the
smoke should be made to pass through a second small furnace.
The number of pots that may be put into a kiln of this kind depends, of
course, upon its dimensions; but, in general, from 100 to 150 are piled
up over each other, in columns, at once; the greatest heat being nearest
the roof of the kiln; which resembles, in many respects, that used for
baking pottery ware.
In both kilns the interior walls are built of fire-bricks. In the oblong
one, the fiercest heat is near the vaulted roof; in the upright one,
near the sole; and the pots, containing the larger lumps of bones,
should be placed accordingly near the top of the former, and the bottom
of the latter. Such a kiln may receive about seventy double pots,
containing in the whole thirty-five cwt. of bones.
After the earth is filled with the pots, and the entrance door is shut,
the fire is applied at first moderately, but afterwards it must be
raised and maintained, at a brisk heat, for eight or ten hours. The door
of the ash-pit and the damper may now be nearly closed, to moderate the
draught, and to keep up a steady ignition for six or eight hours longer,
without additional firing; after which the doors must be all opened to
cool the furnace. When this is done, the brick-work of the entrance door
must be taken down, the kiln must be emptied, and immediately filled
again with a set of pots previously filled with bones, and luted
together: the pots which have been ignited may, in the course of a short
time, be opened, and the contents put into the magazine. But in
operating with the large decomposing cylinder retort, the bones being
raked out hot, must be instantly tossed into a receiver, which can be
covered-in air-tight till they are cool.
The bones lose upon the average about one half of their weight in the
calcination. In reference to the quality of the black, experience has
shown that it is so much more powerful as a discolouring agent, as the
bones from which it was made have been freer from adhering fatty,
fleshy, and tendinous matters.
The charcoal is ground in a mill, either to a fine powder and sifted; or
into a coarse granular state, like gunpowder, for the preparation of
which two sieves are required, one with moderately fine meshes, to allow
the small dust to pass through, and one with large meshes, to separate
the proper sized grains from the coarser lumps. Either a corn-mill, an
edgestone mill, or a steel cylinder mill, may be employed for grinding
bone-black, and it is generally damped in the operation to keep down the
fine dust.
Bone-black, as found in commerce, is very variable in its discolouring
power, which arises from its having been exposed either to too great a
heat which has glazed its carbon, or to too low a heat which has left
its albumen imperfectly decomposed. A steady ignition of due continuance
is the proper decomposing temperature. Its composition is generally as
follows:--
Phosphate of lime, with carbonate of lime, and a little sulphuret of
iron, or oxide of iron, 88 parts; iron in the state of a silicated
carburet, 2 parts; charcoal containing about one fifteenth of azote, 10
parts. None of the substances present, except the charcoal, possesses
separately any discolouring power.
The quality may be tested by a solution of brown sugar, or molasses, or
of indigo in sulphuric acid. The last is generally preferred by the
French chemists, who have occupied themselves most with this subject,
and it contains usually one thousandth part of its weight of this
dye-drug of the best quality. Other animal substances yield a charcoal,
possessed of very considerable discolouring properties. The following
table by M. Bussy exhibits an interesting comparison of almost every
kind of charcoal in this point of view.
Table of the discolouring powers of different charcoals.
+--------------------------+-------+-------+--------+--------+------+
| | |Indigo |Molasses|Blanch- |Power |
|Species of Charcoal. |Weight.| test | test |ing by | by |
| | con- | con- |indigo. |molas-|
| | |sumed. | sumed. | |ses. |
+--------------------------+-------+-------+--------+--------+------+
| |Gramme.|Litres.| | | |
|Blood calcined with potash| 1 | 1·60 | 0·18 | 50 | 20 |
|Ditto with chalk | 1 | 0·57 | 0·10 | 18 | 11 |
|Ditto with phosp. lime | 1 | 0·38 | 0·09 | 12 | 10 |
|Gelatine ditto with potash| 1 | 1·15 | 0·14 | 36 | 15·5 |
|Albumen ditto ditto | 1 | 1·08 | 0·14 | 34 | 15·5 |
|Starch ditto ditto | 1 | 0·34 | 0·08 | 10·6 | 8·8 |
|Charcoal from acet. potash| 1 | 0·18 | 0·04 | 5·6 | 4·4 |
|Ditto from carb. soda by | 1 | 0·38 | 0·08 | 12 | 8·8 |
|phosphorus | | | | | |
|Calcined lamp black | 1 | 0·128 | 0·03 | 4 | 3·3 |
|Ditto ditto potash | 1 | 0·55 | 0·09 | 15·2 | 10·6 |
|Bone black treated with | 1 | 1·45 | 0·18 | 45 | 20 |
|mur. acid and potash | | | | | |
|Bone black ditto with mur.| 1 | 0·06 | 0·015 | 1·87 | 1·6 |
|acid | | | | | |
|Oil calcined with phosp. | 1 | 0·064 | 0·017 | 2 | 1·9 |
|of lime | | | | | |
|Crude bone black | 1 | 0·032 | 0·009 | 1 | 1 |
+--------------------------+-------+-------+--------+--------+------+
With regard to the mode of operation of bone black on coloured liquids,
M. Payen showed in his prize essay, 1. That the decolouring power of
charcoal depends in general upon its state of division; 2. That in the
various charcoals, the carbonaceous matter acts only upon the colouring
matters, combining with and precipitating them; 3. That in the
application of charcoal to the refining of sugar, it acts also upon the
gluten, for it singularly promotes crystallisation; 4. That according to
the above principles, the decolouring action of charcoals may be so
modified, as to make the most inert become the most active; 5. That the
distinction between animal and vegetable charcoals is improper, and that
we may substitute for it that of dull and brilliant charcoals; 6. That
of the substances present in charcoal besides carbon, and particularly
animal charcoal, those which favour the decolouring action, have an
influence relative only to the carbon; they serve as auxiliaries to it,
by insulating its particles, and presenting them more freely to the
action of the colouring matter; 7. That animal charcoal, besides its
decolouring power, has the valuable property of taking lime in solution
from water and syrup; 8. That neither vegetable, nor other charcoals,
besides the animal, have this power of abstracting lime; 9. That by the
aid of the decolorimeter, or graduated tube charged with test solution
of indigo or molasses, it is easy to appreciate exactly the decolouring
properties of all kinds of charcoal.
Different varieties of lignite (fossilized wood) or even pit coal, when
well carbonized in close vessels, afford a decolouring charcoal of
considerable value. By reducing 100 parts of clay into a thin paste with
water, kneading into it 20 parts of tar, and 500 of finely ground pit
coal, drying the mixed mass, and calcining it out of contact of air, a
charcoally matter may be obtained not much inferior to bone-black in
whitening syrups.
The restoration of animal charcoal from burnt bones, for the purpose of
sugar refining, has been long practised in France. Mr. W. Parker has
lately made the following process the subject of a patent. The charcoal,
when taken from the vessels in which it has been employed for the
purposes of clarifying the sugar, is to be thoroughly washed with the
purest water that can be obtained, in order to remove all the saccharine
matter adhering to it. When the washing process has been completed, the
charcoal is laid out to dry, either in the open air or in a suitable
stove, and when perfectly free from moisture, it is to be separated into
small pieces and sifted through a sieve, the wires or meshes of which
are placed at distances of about two and a half in every inch. This
sifting will not only divide the charcoal into small pieces, but will
cause any bits of wood or other improper matters to be separated from
it.
The charcoal, thus prepared, is then to be packed lightly in cylindrical
vessels called crucibles, with some small quantity of bones, oil, or
other animal matter mixed with it. The crucibles are then to be closed
by covers, and luted at the joints, leaving no other opening but one
small hole in the centre of the cover, through which any gas, generated
within the vessel when placed in the oven or furnace, may be allowed to
escape.
The crucibles are now to be ranged round the oven, and placed, one upon
another, in vertical positions; and when the oven is properly heated,
gas will be generated within each crucible, and issue out from the
central hole. The gas thus emitted, being of an inflammable quality,
will take fire, and assist in heating the crucibles; and the operation
being carried on until the crucibles become of a red heat, the oven is
then to be closed, and allowed to cool; after which the crucibles are to
be removed, when the charcoal will be found to have become perfectly
renovated, and fit for use as before.
BORAX. A native saline compound of boracic acid and soda, found
abundantly in Thibet and in South America. The crude product from the
former locality was imported into Europe under the name of _tincal_, and
was purified from some adhering fatty matter by a process kept a long
time secret by the Venetians and the Dutch, and which consisted chiefly
in boiling the substance in water with a little quicklime.
Gmelin found borax, in prismatic crystals, to contain 46·6 per cent. of
water; and Arvredson, in the calcined state, to consist of 68·9 of acid
and 31·1 soda, in 100 parts. M. Payen describes an octahedral borax,
which contains only 30·64 per cent. of water, and is therefore preferred
by the braziers in their soldering processes.
Borax has a sweetish, somewhat lixivial taste, and affects vegetable
colours like an alkali; it is soluble in 12 parts of cold and 2 of
boiling water. It effloresces and becomes opaque in a dry atmosphere,
and appears luminous, by friction, in the dark. It melts at a heat a
little above that of boiling water, and gives out its water of
crystallization, after which it forms a spongy mass, called calcined
borax. The octahedral borax, which is prepared by crystallization, in a
solution of 1·256 sp. gr., kept up at 145° F., is not efflorescent. When
borax is ignited, it fuses into a glassy-looking substance.
The following is the improved mode of purifying borax. The crude
crystals are to be broken into small lumps, and spread upon a filter
lined with a lead grating, under which a piece of cloth is stretched
upon a wooden frame. The lumps are piled up to the height of 12 inches,
and washed with small quantities of a caustic soda lye of 5° B. (sp. gr.
1·033) until the liquor comes off nearly colourless; they are then
drained, and put into a large copper of boiling water, in such
quantities that the resulting solution stands 20° B. (sp. gr. 1·160).
Carbonate of soda, equivalent to 12 per cent. of the borax must now be
added; the mixed solution is allowed to settle, and the clear liquid
syphoned off into crystallizing vessels. Whenever the mother waters get
foul, they must be evaporated to dryness in cast-iron pots, and roasted,
to burn away the viscid colouring matter.
Borax is sometimes adulterated with alum and common salt: the former
addition may be readily detected by a few drops of water of ammonia,
which will throw down its alumina; and the latter by nitrate of silver,
which will give with it a precipitate insoluble in nitric acid.
The native boracic acid obtained from the lakes of Tuscany, which has
been manufactured in France into borax, has greatly lowered the price of
this article of commerce. When MM. Payen and Cartier first began the
business, they sold the crystals at the same price as the Dutch, viz. 7
francs the kilogramme (2-1/5 lbs. avoird.); but, in a few years, they
could obtain only 2 francs and 60 centimes, in consequence of the market
getting overstocked. The annual consumption of France in 1823 was 25,000
kilos., and the quantity produced in M. Payen’s works was 50,000. The
mode of making borax from the acid is as follows:--The lake water is
evaporated in graduation houses, and then concentrated in boilers till
it crystallizes. In that state it is carried to Marseilles. About 500
kilogrammes of water are made to boil in a copper, and 600 kilogrammes
of crystallized carbonate of soda are dissolved in it by successive
additions of 20 kilogrammes. The solution being maintained at nearly the
boiling point, 500 kilogrammes of the crystallized boracic acid of
Tuscany are introduced, in successive portions. At each addition of
about 10 kilogrammes, a lively effervescence ensues, on which account
the copper should be of much greater capacity than is sufficient to
contain the liquors. When the whole acid has been added, the fire must
be damped by being covered up with moist ashes, and the copper must be
covered with a tight lid and blankets, to preserve the temperature
uniform. The whole is left in this state during 30 hours; the clear
liquor is then drawn off into shallow crystallizing vessels of lead, in
which it should stand no higher than 10 or 12 inches, to favour its
rapid cooling. At the end of three days in winter, and four in summer,
the crystallization is usually finished. The mother water is drawn off,
and employed, instead of simple water, for the purpose of dissolving
fresh crystals of soda. The above crystals are carefully detached with
chisels, redissolved in boiling water, adding for each 100 kilos., 10
kilos. of carbonate of soda. This solution marks 20° B. (sp. gr. 1·160);
and, at least, one ton (1000 kilos.) of borax should be dissolved at
once, in order to obtain crystals of a marketable size. Whenever this
solution has become boiling hot, it must be run off into large
crystallizing lead chests of the form of inverted truncated pyramids,
furnished with lids, enclosed in wooden frames, and surrounded with mats
to confine the heat. For a continuous business there should be at least
18 vessels of this kind; as the solution takes a long time to complete
its crystallization, by cooling to 30° C. (86° F.). The borax crystals
are taken out with chisels, after the liquor has been drawn off, and the
whole has become cold.
One hundred parts of the purest acid, usually extracted from the lakes
of Tuscany, contain only fifty parts of the real boracic acid, and yield
no more, at the utmost, than 140 or 150 of good borax.
Dry borax acts on the metallic oxides at a high temperature, in a very
remarkable manner, melting and vitrifying them into beautiful coloured
glasses. On this account it is a most useful reagent for the blowpipe.
Oxide of chrome tinges it of an emerald green; oxide of cobalt, an
intense blue; oxide of copper, a pale green; oxide of tin, opal; oxide
of iron, bottle green and yellow; oxide of manganese, violet; oxide of
nickel, pale emerald green. The white oxides impart no colour to it by
themselves. In the fusion of metals borax protects their surface from
oxidizement, and even dissolves away any oxides formed upon them; by
which twofold agency it becomes an excellent flux, invaluable to the
goldsmith in soldering the precious metals, and to the brazier in
soldering copper and iron.
Borax absorbs muriatic and sulphurous acid gases, but no others, whereby
it becomes, in this respect, a useful means of analysis.
The strength or purity of borax may be tested by the quantity of
sulphuric acid requisite to neutralize a given weight of it, as
indicated by tincture of litmus.
When mixed with shell-lac in the proportion of one part to five, borax
renders that resinous body soluble in water, and forms with it a species
of varnish.
Boracic acid is a compound of 31·19 of boron and 68·81 oxygen, in 100
parts. Its prime equivalent referred to oxygen 100, is 871·96.
The following process for refining the native Indian borax or tincal,
has been published by MM. Robiquet and Marchand:--
It is put into large tubs, covered with water for 3 or 4 inches above
its surface, and stirred through it several times during six hours. For
400 pounds of the tincal there must now be added one pound of quicklime
diffused through two quarts of water. Next day the whole is thrown upon
a sieve, to drain off the water with the impurities, consisting, in some
measure, of the fatty matter combined with the lime, as an insoluble
soap. The borax, so far purified, is to be dissolved in 2-1/2 times its
weight of boiling water, and eight pounds of muriate of lime are to be
added for the above quantity of borax. The liquor is now filtered,
evaporated to the density of 18° or 20° B. (1·14 to 1·16 sp. grav.), and
set to crystallize in vessels shaped like inverted pyramids, and lined
with lead. At the end of a few days, the crystallization being
completed, the mother waters are drawn off, the crystals are detached
and dried. The loss of weight in this operation is about 20 per cent.
The quantity of borax imported into the United Kingdom in 1835 was
335,224 pounds; whereof 122,022 pounds were exported. The duty is 10_s._
upon the refined, and 4_s._ unrefined.
BOOKBINDING, is the art of sewing together the sheets of a book; and
securing them with a back and side boards. Binding is distinguished from
stitching, which is merely sewing the leaves without bands or backs; and
from half-binding, which consists in securing the back only with
leather, the pasteboard sides being covered with blue or marble paper;
whereas in binding, both the back and sides are covered with leather.
Bookbinding, according to the present mode, is performed in the
following manner:--The sheets are first folded into a certain number of
leaves, according to the form in which the book is to appear; viz. two
leaves for folios, four for quartos, eight for octavos, twelve for
duodecimos, &c. This is done with a slip of ivory or boxwood, called a
folding stick; and in the arrangement of the sheets the workmen are
directed by the catch-words and signatures at the bottom of the pages.
When the leaves are thus folded and arranged in proper order, they are
usually beaten upon a stone with a heavy hammer, to make them solid and
smooth, and are then condensed in a press. After this preparation they
are sewed in a sewing press, upon cords or packthreads called bands,
which are kept at a proper distance from each other, by drawing a thread
through the middle of each sheet, and turning it round each band,
beginning with the first and proceeding to the last. The number of bands
is generally six for folios, and five for quartos, or any smaller size.
The backs are now glued, and the ends of the bands are opened, and
scraped with a knife, that they may be more conveniently fixed to the
pasteboard sides; after which the back is turned with a hammer, the book
being fixed in a press between boards, called backing boards, in order
to make a groove for admitting the pasteboard sides. When these sides
are applied, holes are made in them for drawing the bands through, the
superfluous ends are cut off, and the parts are hammered smooth. The
book is next pressed for cutting; which is done by a particular machine
called the plough, to which is attached a knife. See the figures and
descriptions _infra_. It is then put into a press called the cutting
press, betwixt two boards, one of which lies even with the press, for
the knife to run upon; and the other above for the knife to cut against.
After this the pasteboards are cut square with a pair of iron shears;
and last of all, the colours are sprinkled on the edges of the leaves,
with a brush made of hog’s bristles; the brush being held in the one
hand, and the hair moved with the other.
Different kinds of binding are distinguished by different names, such as
law binding, marble binding, French binding, Dutch binding, &c. In Dutch
binding, the backs are vellum. In French binding a slip of parchment is
applied over the back between each band, and the ends are pasted upon
the inside of each pasteboard. This indorsing, as it is called, is
peculiar to the French binders; who are enjoined, by special
_ordonnance_, to back their books with parchment. The parchment is
applied in the press, after the back has been grated to make the paste
take hold. The Italians still bind in a coarse thick paper, and this
they call binding _alla rustica_. It is extremely inconvenient, as it is
liable to wear without particular care.
A patent was obtained in 1799 by Messrs. John and Joseph Williams,
stationers in London, for an improved method of binding books of every
description. The improvement consists of a back, in any curved form,
turned a little at the edges, and made of iron, steel, copper, brass,
tin, or of ivory, bone, wood, vellum, or, in short, any material of
sufficient firmness. This back is put on the book before it is bound, so
as just to cover without pressing the edges; and the advantage of it is
that it prevents the book, when opened, from spreading on either side,
and causes it to rise in any part to nearly a level surface. In this
method of binding the sheets are prepared in the usual manner, then
sewed on vellum slips, glued, cut, clothed, and boarded, or half
boarded; the firm back is then fastened to the sides by vellum drawn
through holes, or secured by inclosing it in vellum or ferret wrappers,
or other materials pasted down upon the boards, or drawn through them.
A patent was likewise obtained in 1800 by Mr. Ebenezer Palmer, a London
stationer, for an improved way of binding books, particularly merchants’
account-books. This improvement has been described as follows:--let
several small bars of metal be provided about the thickness of a
shilling or more, according to the size and thickness of the book; the
length of each bar being from half an inch to several inches, in
proportion to the strength required in the back of the book. At each end
of every bar let a pivot be made of different lengths, to correspond to
the thickness of two links which they are to receive. Each link must be
made in an oval form, and contain two holes proportioned to the size of
the pivots, these links to be the same metal as the hinge, and each of
them nearly equal in length to the width of two bars. The links are then
to be riveted on the pivots, each pivot receiving two of them, and thus
holding the hinge together, on the principle of a link-chain or hinge.
There must be two holes or more of different sizes, as may be required,
on each bar of the hinge or chain; by means of these holes each section
of the book is strongly fastened to the hinge which operates with the
back of the book, when bound, in such a manner as to make the different
sections parallel with each other, and thus admit writing without
inconvenience on the ruled lines, close to the back.
The leather used in covering books is prepared and applied as follows:
being first moistened in water, it is cut to the size of the book, and
the thickness of the edge is paired off on a marble stone. It is next
smeared over with paste made of wheat flour, stretched over the
pasteboard on the outside, and doubled over the edges within. The book
is then corded, that is, bound firmly betwixt two boards, to make the
cover stick strongly to the pasteboard and the back; on the exact
performance of which the neatness of the book in a great measure
depends. The back is then warmed at the fire to soften the glue, and the
leather is rubbed down with a bodkin or folding stick, to set and fix it
close to the back of the book. It is now set to dry, and when dry the
boards are removed; the book is then washed or sprinkled over with a
little paste and water, the edges and squares blacked with ink, and then
sprinkled fine with a brush, by striking it against the hand or a stick;
or with large spots, by being mixed with solution of green vitriol,
which is called marbling. Two blank leaves are then pasted down to the
cover, and the leaves, when dry, are burnished in the press, and the
cover rolled on the edges. The cover is now glazed twice with the white
of an egg, filleted, and last of all, polished, by passing a hot iron
over the glazed colour.
The employment in book binding of a rolling press for smoothing and
condensing the leaves, instead of the hammering which books have usually
received, is an improvement introduced several years ago into the trade
by Mr. W. Burn. His press consists of two iron cylinders about a foot in
diameter, adjustable in the usual way, by means of a screw, and put in
motion by the power of one man or of two, if need be, applied to one or
two winch-handles. In front of the press sits a boy who gathers the
sheets into packets, by placing two, three, or four upon a piece of tin
plate of the same size, and covering them with another piece of tin
plate, and thus proceeding by alternating tin plates and bundles of
sheets till a sufficient quantity have been put together, which will
depend on the stiffness and thickness of the paper. The packet is then
passed between the rollers and received by the man who turns the winch,
and who has time to lay the sheets on one side, and to hand over the tin
plates by the time that the boy has prepared a second packet. A minion
bible may be passed through the press in one minute, whereas the time
necessary to beat it would be twenty minutes. It is not, however, merely
a saving of time that is gained by the use of the rolling press; the
paper is made smoother than it would have been by beating, and the
compression is so much greater, that a rolled book will be reduced to
about five-sixths of the thickness of the same book if beaten. A shelf,
therefore, that will hold fifty books bound in the usual way would hold
nearly sixty of those bound in this manner, a circumstance of no small
importance, when it is considered how large a space even a moderate
library occupies, and that book-cases are an expensive article of
furniture. The rolling press is now substituted for the hammer by
several considerable bookbinders.
[Illustration: 141 142]
_Fig._ 141. represents the sewing press, as it stands upon the table,
before which the bookbinder sits. _Fig._ 142. is a ground plan without
the parts _a_ and _n_ in the former figure. A is the base-board,
supported upon the cross bars _m n_, marked with dotted lines in _fig._
142. Upon the screw rods _r r_ _fig._ 141. the nuts _t d_ serve to fix
the flat upper bar _n_, at any desired distance from the base. That bar
has a slit along its middle, through which the hooks below _z z_ pass
down for receiving the ends of the sewing cords _p p_, fixed at _y y_,
and stretched by the thumb-screws _z z_. The bar _y y_ is let into an
oblong space cut out of the front edge of the base board and fixed there
by a movable pin _a_, and a fixed pin at its other end round which it
turns.
[Illustration: 143]
_Fig._ 143. is the bookbinder’s cutting press, which is set upright upon
a sort of chest for the reception of the paper parings; and consists of
three sides, being open above and to the left hand of the workman. The
pressbar, or beam _a_, has two holes _n n_ upon its under surface, for
securing it to two pegs standing on the top of the chest. The screw rods
_t t_ pass through two tapped holes in the bar, marked with _b c_ at its
upper end; their heads _r r_ being held by the shoulders _o o_. The
heads are pierced with holes into which lever pins are thrust for
screwing the rods hard up. The heavy beam _a_ remains immovable, while
the parallel bar with the book is brought home towards it by the two
screws. The two rulers _s s_ serve as guides to preserve the motions
truly parallel; and the two parallel lath bars _b c_ guide between them
the end bar _e_, of the plough, whose knife is shown at _i_, with its
clamping screw _z_.
[Illustration: 144 145]
Mr. Oldham, printing engineer of the Bank of England, distinguished for
mechanical ingenuity, has contrived a convenient machine for cutting the
edges of books, banknotes, &c. either truly square or polygonal, with
mathematical precision. _Fig._ 144. represents an end elevation of the
machine. _Fig._ 145. a side view of the same, the letters of reference
indicating the same parts of the machine in each of the figures.
[Illustration: 146 147]
_a_, is the top cross bar with rectangular grooves _b b_; _c c_, are
side posts; _d d_, cross feet to the same, with strengthening brackets;
_e e_, a square box, in which the press stands, for holding waste
cuttings. _Fig._ 146. is a cross section of the upright posts, _c c_,
taken horizontally. There are rectangular grooves in the upright posts,
for the projecting ends of the cast iron cross bracket _f_, to slide up
and down in. In the middle of the under-side of this piece _f_, there is
a boss, within which is a round recess, to receive the top of the screw
_g_, which works in the cast iron cross piece _h_, similarly made with
the former, but bolted firmly to the posts _c c_. Upon the screw _g_
there is a circular handle or ring _i_, for partially turning the screw,
and immediately over it cross holes for tightening the press by means of
a lever bar. Upon the cross piece _f_, is bolted the board _j_, and upon
each end of this board is made fast the rabbetted pieces _k k_, for
another board _l_, to slide in. Across the middle of this board, and
parallel to the pieces _k k_, the tongue piece _m_, is made fast, which
fits into a groove in the bottom of board _l_. A horizontal
representation of this is seen at _fig._ 147. and immediately under this
view is also seen an end view of _l_, and _f_, connected together, and a
side view of _f_ by itself. In the middle of the board _l_, is a pin
for a circular board _n_, to turn upon, and upon this latter board is
placed the “material to be cut,” with a saving piece between it, and the
circular piece which is to be divided upon its edge into any number of
parts required, with a stationary index on the board _l_, to point to
each.
It will now be understood that the “material to be cut,” may be turned
round upon the centre pin of the board _n_, and also that both it and
the board can be shifted backward and forward under the top cross piece
_a_, and between the side slide slips _k k_, the surfaces of which
should also be divided into inches and tenths.
The plough, _fig._ 148., shown in several positions, is made to receive
two knives or cutters as the “material to be cut” may require, and which
are situated in the plough as I now describe. The plough is composed of
three principal parts, namely, the top, and its two sides. The top _o_,
is made the breadth of the cross piece _a_, and with a handle made fast
thereon. The sides _p p_, are bolted thereto, with bolts and nuts
through corresponding holes in the top and sides. The figures below give
inside views, and cross sections of the details of the manner in which
the cutters and adjustments are mounted. A groove is cut down each cheek
or side, in which are placed screws that are held at top and bottom from
moving up and down, but by turning they cause the nuts upon them to do
so; they are shown at _q q_. These nuts have each a pin projecting
inwards, that go into plain holes made in the top ends of cutters _r r_.
The 148th. and following figs. are 1/4 in scale.
[Illustration: 148 149 150 151 152 153 154]
The cutters, and the work for causing them to go up and down, are sunk
into the cheeks, so as to be quite level with their inner surfaces.
_Fig._ 149. shows one of those screws apart, how fixed, and with
moveable nut and projecting pin. The top of each screw terminates with a
round split down, and above it a pinion wheel and boss thereon, also
similarly split. This pinion fits upon the split pin. Above, there is
cross section of a hollow coupling cap with steel tongue across, that
fits into both the cuts of the screw pin and pinion boss, so that when
lowered upon each other, they must all turn together. In the middle and
on the top of the upper piece _o_, the larger wheel _s_, runs loose upon
its centre, and works into the two pinion-wheels _t t_. The wheel _s_
has a fly-nut with wings mounted upon it.
It will now be seen, when the plough is in its place as at _fig._ 150.,
that if it be pushed to and fro by the right hand, and the nut
occasionally turned by the left, the knives or cutters will be protruded
downwards at the same time, and these either will or will not advance as
the coupling caps _u u_ are on or off. The ribs _v v_, run in the
grooves _b b_, _fig._ 144., and keep the cutters to their duty, working
steadily. The top cross bar _a_, is the exact breadth of a bank-note, by
which means both knives are made to cut at the same time. The paper is
cut uniformly to one length, and accurately square.
By the use of this machine, the air-pump paper-wetting apparatus, and
appendant press, the paper of 45,000 notes is fully prepared in one hour
and a half by one person, and may then be printed. It is not so much
injured by this process as by the ordinary method of clipping by hand,
soaking it, &c., which more or less opens and weakens the fabric,
especially of bank-note paper.
One of the greatest improvements ever made in the art of bookbinding is,
apparently, that for which Mr. William Hancock has very recently
obtained a patent. After folding the sheets in double leaves, he places
them vertically, with the edges forming the back of the book downwards
in a concave mould, of such rounded or semi-cylindrical shape as the
back of the book is intended to have. The mould for this purpose
consists of two parallel upright boards, set apart upon a cradle frame,
each having a portion or portions cut out vertically, somewhat deeper
than the breadth of the book, but of a width nearly equal to its
thickness before it is pressed. One of these upright boards may be
slidden nearer to or farther from its fellow, by means of a guide bar,
attached to the sole of the cradle. Thus the distance between the
concave bed of the two vertical slots in which the book rests, may be
varied according to the length of the leaves. In all cases about
one-fourth of the length of the book at each end projects beyond the
board, so that one half rests between the two boards. Two or three
packthreads are now bound round the leaves thus arranged, from top to
bottom of the page in different lines, in order to preserve the form
given to the back of the mould in which it lay. The book is next
subjected to the action of the press. The back, which is left projecting
_very slightly_ in front, is then smeared carefully by the fingers with
a solution of caoutchouc, whereby each paper-edge receives a small
portion of the cement. In a few hours it is sufficiently dry to take
another coat of a somewhat stronger caoutchouc solution. In 48 hours, 4
applications of the caoutchouc may be made and dried. The back and the
adjoining part of the sides are next covered with the usual band or
fillet of cloth, glued on with caoutchouc; after which the book is ready
to have the boards attached, and to be covered with leather or parchment
as may be desired.
We thus see that Mr. Hancock dispenses entirely with the operations of
stitching, sewing, sawing-in, hammering the back, or the use of paste
and glue. Instead of leaves attached by thread stitches at 2 or 3
points, we have them agglutinated securely along their whole length.
Books bound in this way open so perfectly flat upon a table without
strain or resilience, that they are equally comfortable to the student,
the musician, and the merchant. The caoutchouc cement moreover being
repulsive to insects, and not affected by humidity, gives this mode of
binding a great superiority over the old method with paste or glue,
which attracted the ravages of the moth, and in damp situations allowed
the book to fall to pieces. For engravings, atlasses, and ledgers, this
binding is admirably adapted, because it allows the pages to be
displayed most freely, without the risk of dislocating the volume; but
for security, 3 or 4 stitches should be made. The leaves of music-books
bound with caoutchouc, when turned over, lie flat at their whole extent,
as if in loose sheets, and do not torment the musician like the leaves
of the ordinary books, which are so ready to spring back again.
Manuscripts and collections of letters which happen to have little or no
margin left at the back for stitching them by, may be bound by Mr.
Hancock’s plan without the least encroachment upon the writing. The
thickest ledgers thus bound, open as easily as paper in quire, and may
be written on up to the innermost margin of the book without the least
inconvenience.
Having inspected various specimens of Mr. Hancock’s workmanship, I
willingly bear testimony to the truth of the preceding statement. See
CLOTH BINDING.
[Illustration: 155]
BOTTLE MANUFACTURE. The following mechanism for moulding bottles, forms
the subject of a patent obtained by Henry Rickets of Bristol in 1822.
_Fig._ 155. is a section of the apparatus, consisting of a square frame,
_a a_, of iron or wood; this is fixed in a pit formed in the floor; _b
b_ is the base of the frame, with an aperture for knocking up the bottom
of the bottle; _c c_ are four legs secured to the frame-floor _b_, upon
which the mould is supported. The platform or stand of the mould _d d_
has an opening in its centre for the introduction of the bottom of the
mould, which is raised against the bottom of the bottle by the knocker
up; _e e_ are the sides of the mould; and _f f_ is the top of the mould
in two pieces, turning over upon the joints at _g g_, so as to form the
neck of the bottle; _h h_ are levers or arms for raising and depressing
the top pieces; _i i_ is a horizontal shaft or axle, turning in bearings
at each end, from which shaft two levers, _k k_, extend; these levers
are connected by upright rods, _l l_, to the levers or arms, _h h_, of
the top pieces _f f_.
The weight of the arms _h h_, and rods _l l_, will, by their gravity,
cause the top pieces to open, as shown by the dotted lines; in this
situation of the mould, the melted glass is to be introduced by a tube
as usual. The workman then steps with one foot upon the knob _m_, which
forces down the rod _n_, and by means of a short lever _o_, extending
from the shaft _i_, forces down the top pieces _f_, and closes the
mould, as seen in the figure; the glass is then made to extend itself to
the shape of the mould, by blowing as usual, so as to form the bottle,
and the workman at this time putting his other foot upon the knob _p_,
depresses the rod _q_, and hence raises the bottom of the mould by means
of the knocker-up, _r_, so as to form the bottom of the bottle.
At the bottom of the mould a ring is introduced of any required
thickness, for the purpose of regulating the capacity of the bottle;
upon which ring it is proposed to raise letters and figures, as a mould
to imprint the maker’s name and the size of the bottle. These moulds can
be removed and changed at pleasure. Under the knob _p_, a collar or
washer is to be introduced, of any required thickness, to regulate the
knocking up of the bottom, by which a perfect symmetry of form is
presented. In order to make bottles of different sizes or forms, the
mould is intended to be removed, and its place supplied by another mould
of different dimensions and figure; the lower parts of all the moulds
being made to fit the same frame. Such a mould ought to be prescribed by
legislative enactment, with an excise stamp to define the capacity of
every bottle, and thereby put an end to the interminable frauds
committed in the measure of wine and all other liquors sold by the
bottle.
BOUGIE. A smooth, flexible, elastic, slender cylinder, introduced into
the urethra, rectum, or œsophagus, for opening or dilating it, in cases
of stricture and other diseases. The invention of this instrument is
claimed by Aldereto, a Portuguese physician, but its form and uses were
first described by his pupil Amatus, in the year 1554. Some are solid,
and some hollow; some corrosive, and some mollifying. They generally owe
their elasticity to linseed oil, inspissated by long boiling, and
rendered drying by litharge. This viscid matter is spread upon a very
fine cord or tubular web of cotton, flax, or silk, which is rolled upon
a slab when it becomes nearly solid by drying, and is finally polished
in the same way.
Pickel, a French professor of medicine, published the following recipe
for the composition of bougies. Take 3 parts of boiled linseed oil, one
part of amber, and one of oil of turpentine; melt and mix these
ingredients well together, and spread the compound at three successive
intervals upon a silk cord or web. Place the pieces so coated in a stove
heated to 150° F.; leave them in it for 12 hours, adding 15 or 16 fresh
layers in succession, till the instruments have acquired the proper
size. Polish them first with pumice-stone, and finally smooth with
tripoli and oil. This process is the one still employed in Paris, with
some slight modifications; the chief of which is dissolving in the oil
one twentieth of its weight of caoutchouc to render the substance more
solid. For this purpose the caoutchouc must be cut into slender shreds,
and added gradually to the hot oil. The silk tissue must be fine and
open, to admit of the composition entering freely among its filaments.
Each successive layer ought to be dried first in a stove, and then in
the open air, before another is applied. This process takes two months
for its completion, in forming the best bougies called _elastic_; which
ought to bear twisting round the finger without cracking or scaling, and
extension without giving way, but retracting when let go. When the
bougies are to be hollow, a mandril of iron wire, properly bent with a
ring at one end, is introduced into the axis of the silk tissue. Some
bougies are made with a hollow axis of tin foil rolled into a slender
tube. Bougies are also made entirely of caoutchouc, by the intervention
of a solution of this substance in sulphuric ether, a menstruum
sufficiently cheap in France, on account of the low duty upon alcohol.
There are medicated bougies, the composition of which belongs to
surgical pharmacy. The manufacture of these instruments of various kinds
forms a separate and not inconsiderable branch of industry at Paris. MM.
Feburger and Lamotte are eminent in this line.
BRACES. (_Bretelles_, Fr. _Hosenträger_, Germ.) Narrow fillets or bands
of leather or textile fabric, which pass over the shoulders, and are
attached behind and before to the waistbands of pantaloons and trowsers,
in the act of wearing them, for supporting their weight, and _bracing_
them up to the body. It is a useful modern invention, superseding the
necessity of girding the belly with a tight girdle, as in former times.
[Illustration: 156 157]
BRAIDING MACHINE. (_Machine à lacets_, Fr.; _Bortenwerkerstuhl_, Germ.)
This being employed, not only to manufacture stay-laces, braid, and
upholsterer’s cord, but to cover the threads of caoutchouc for weaving
brace-bands, deserves a description in this work. Three threads at least
are required to make such a knitted lace, but 11, 13, or 17, and even 29
threads are often employed, the first three numbers being preferred.
They are made by means of a frame of a very ingenious construction,
which moves by a continuous rotation. We shall describe a frame with 13
threads, from which the structure of the others may be readily
conceived. The basis of the machine consists of four strong wooden
uprights, A, _fig._ 156, 157, 158., occupying the four angles of a
rectangle, of which one side is 14 inches long, the other 18 inches, and
the height of the rectangle about 40 inches. _Fig._ 156. is a section in
a horizontal plane, passing through the line _a b_ of _fig._ 157. which
is a vertical section in a plane passing through the centre of the
machine C, according to the line _c d_, _fig._ 156. The side X is
supposed to be the front of the frame; and the opposite side, Y, the
back. B, six spindles or skewers, numbered, from 1 to 6, placed in a
vertical position upon the circumference of a circle, whose centre
coincides with that of the machine at the point C. These six spindles
are composed, 1. Of so many iron shafts or axes D, supported in brass
collets E, (_fig._ 157.) and extended downwards within 6 inches of the
ground, where they rest in brass steps fixed upon a horizontal beam. 2.
Wooden heads, made of horn-beam or nut-tree, placed, the first upon the
upper end of each spindle, opposite the cut-out beam F, and the second
opposite the second beam G. 3. Wooden-toothed wheels, H, reciprocally
working together, placed between the beam G, and the collet-beam E. The
toothed wheels and the lower heads for each spindle are in one piece.
The heads and shafts of the spindles No. 1. and 6., are one fifth
stronger than those of the other spindles; their heads have five
semi-circular grooves, and wheels of 60 teeth, while the heads of the
others have only four grooves, and wheels of 48 teeth; so that the
number of the grooves in the six spindles is 26, one half of which is
occupied with the stems of the puppets I, which carry the 13 threads
from No. 1. to 13. The toothed wheels, which give all the spindles a
simultaneous movement, but in different directions, are so disposed as
to bring their grooves opposite to each other in the course of rotation.
K, the middle winglet, triple at bottom and quintuple at top, which
serves to guide the puppets in the direction they ought to pursue.
L, three winglets, single at top and bottom, placed exteriorly, which
serve a like purpose.
M, two winglets, triple at bottom and single at top, placed likewise
exteriorly, and which serve the same purposes as the preceding; _m_, are
iron pins inserted in the cut-out beam G, which serve as stops or limits
to the oscillations of the exterior winglets.
Now, if by any moving power (a man can drive a pair) rotation be
impressed upon the large spindle No. 1., in the direction of the arrow,
all the other spindles will necessarily pursue the rotatory movement
indicated by the respective arrows. In this case, the 13 puppets working
in the grooves of the heads of the spindles will be carried round
simultaneously, and will proceed each in its turn, from one extremity of
the machine to the opposite point, crossing those which have a
retrograde movement. The 13 threads united at the point N, situated
above the centre of the machine, will form at that point the braid,
which after having passed over the pulley _o_, comes between the two
rollers P Q, and is squeezed together, as in a flatting-mill, where the
braid is calendered at the same time that it is delivered. It is obvious
that the roller P, receives its motion from the toothed wheel of the
spindle No. 3., and from the intermediate wheels R, S, T, as well as
from the endless screw Z, which drives at proper speed the wheel W,
fixed upon the shaft of the roller P.
The braid is denser in proportion as the point N is less elevated above
the tops of the puppets; but in this case, the eccentric motion of these
puppets is much more sensible in reference to that point, towards which
all the threads converge, than when it is elevated. The threads which
must be always kept equally stretched by means of a weight, as we shall
presently see, are considerably strained by the traction, occasioned by
the constantly eccentric movement of the puppets. From this cause,
braiding machines must be worked at a moderate velocity. In general, for
fine work, 30 turns of the large spindle per minute are the utmost that
can safely be made.
[Illustration: 158]
The puppet or spindle of this machine, being the most important piece, I
have represented it in section, upon a scale one fourth of its actual
size, _fig._ 158. It is formed of a tube, _a_, of strong sheet iron well
brazed; _b_ is a disc, likewise of sheet iron, from which a narrow
fillet, _c_, rises vertically as high as the tube, where both are
pierced with holes, _d e_, through which the thread _f_ is passed, as it
comes from the bobbin, _g_, which turns freely upon the tube _a_. The
top of this bobbin is conical and toothed. A small catch or detent, _h_,
moveable in a vertical direction round _i_, falls by its own weight into
the teeth of the crown of the bobbin, in which case this cannot revolve;
but when the detent is raised so far as to disengage the teeth, and at
the same time to pull the thread, the bobbin turns, and lets out thread
till the detent falls back into these same teeth.
A skewer of iron wire, _k_, is loaded with a small weight, _l_, melted
upon it. The top of this skewer has an eye in it, and the bottom is
recurved as is shown in _fig._ 158., so that supposing the thread comes
to break, this skewer falls into the actual position in the figure,
where we see its lower end extending beyond the tube _a_, by about 1/4
of an inch; but as long as the thread is unbroken, the skewer _k_, which
serves to keep it always tense, during the eccentric movement of the
puppet, does not pass out below the tube.
This disposition has naturally furnished the means of causing the
machine to stop, whenever one of the threads breaks. This inferior
protrusion of the skewer pushes in its progress a detent, which
instantly causes the band to slide from the driving pulley to the loose
pulley. Thus the machine cannot operate unless all the threads be
entire. It is the business of the operative, who has 3 or 4 under her
charge, to mend the threads as they break, and to substitute full
bobbins for empty ones, whenever the machine is stopped.
The braiding frame, though it does not move quickly, makes a great deal
of noise, and would make still more, were the toothed wheels made of
metal instead of wood. For them to act well, they should be made with
the greatest precision, by means of appropriate tools for forming the
teeth of the wheels, and the other peculiar parts.
BRAN. (_Son_, Fr.; _Kleie_, Germ.) The husky portion of ground wheat,
separated by the boulter from the flour. It is advantageously employed
by the calico printers, in the clearing process, in which, by boiling in
bran-water, the colouring matters adhering to the non-mordanted parts of
maddered goods, as well as the dun matters which cloud the mordanted
portions, are removed. A valuable series of researches concerning the
operation of bran in such cases was made a few years ago by that
distinguished chemist and calico printer, M. Daniel Kœchlin-Schouch, and
published in the ninth number of the Bulletin de la Société Industrielle
de Mulhausen. Nine sets of experiments are recorded, which justified the
following conclusions.
1. The dose of two bushels of bran for 10 pieces of calico is the best,
the ebullition being kept up for an hour. A boil for the same time in
pure water had no effect in clearing either the grounds or the figures.
2. Fifteen minutes boiling are sufficient when the principal object is
to clear white grounds, but in certain cases thirty minutes are
requisite to brighten the dyed parts. If, by increasing the charge of
bran, the time of the ebullition could be shortened, it would be in some
places, as Alsace, an economy; because for the passage of ten pieces
through a copper or vat heated with steam, 1 cwt. of coal is consumed in
fuel which costs from 2-1/2 to 3 francs, while two bushels of bran are
to be bought for one franc.
3. By increasing the quantity of water from 12 to 24 hectolitres with
two bushels of bran, the clearing effect upon the ten pieces was
impaired. It is therefore advantageous not to use too much water.
4. Many experiments concur to prove that flour is altogether useless for
the clearing boil, and that finer bran is inferior for this purpose to
the coarser.
5. The white ground of the calicoes boiled with wheat bran, are
distinguishable by their superior brightness from that of those boiled
with rye bran, and especially with barley bran; the latter having hardly
any effect.
6. There is no advantage in adding soap to the bran boil; though a
little potash or soda may be properly introduced when the water is
calcareous.
7. The pellicle of the bran is the most powerful part, the flour and the
starch are of no use in clearing goods, but the mucilage which forms one
third of the weight of the bran has considerable efficacy, and seems to
act in the following way. In proportion as the mucilaginous substance
dissolves the colouring and tawny matters upon the cloth, the husky
surface attracts and fixes upon itself the greater part of them.
Accordingly, when used bran is digested in a weak alkaline bath, it
gives up the colour which it had absorbed from the cloth.
The following chemical examination of bran is interesting. A pound of it
was boiled at successive times with water, the decoctions being
filtered, let fall in cooling a greyish deposit, which was separated by
decantation. The clear liquor afforded by evaporation to dryness four
ounces of a brownish, brittle matter, composed chiefly of mucilage, a
little gluten, and starch. The gray deposit of the above filtered liquor
amounted to half an ounce. Nine ounces of the cortical portion of the
bran were obtained. The loss amounted to 2-1/2 ounces, being in some
measure the hygrometric water of the bran itself.
When boiled with distilled water, goods are cleared pretty well without
bran. Certain delicate dyes must be boiled only a few minutes in a
strong decoction of bran previously made.
BRANDY. The name given in this country to ardent spirits distilled from
wine, and possessed of a peculiar taste and flavour, due to a minute
portion of a peculiar volatile oil. Each variety of alcohol has an aroma
characteristic of the fermented substance from which it is procured;
whether it be the grape, cherries, sugar-cane, rice, corn, or potatoes;
and it may be distinguished even as procured from different growths of
the vine. The brandies of Languedoc, Bordeaux, Armagnac, Cognac, Aunis,
Saintonge, Rochelle, Orleans, Barcelona, Naples, &c. being each readily
recognisable by an experienced dealer.
Aubergier showed, by experiments, that the disagreeable taste of the
spirits distilled from the _marc_ of the grape is owing to an essential
oil contained in the skin of the grape; and found that the oil, when
insulated, is so energetic that a few drops are sufficient to taint a
pipe of 600 litres of fine-flavoured spirit.
The most celebrated of the French brandies, those of Cognac and
Armagnac, are slightly rectified to only from 0·935 to 0·922; they
contain more than half their weight of water, and come over therefore
highly charged with the fragrant essential oil of the husk of the grape.
When, to save expense of carriage, the spirit is rectified to a much
higher degree, the dealer, on receiving it at Paris, reduces it to the
market proof by the addition of a little highly-flavoured weak brandy
and water; but he cannot in this way produce so finely-flavoured a
spirit, as the weaker product of distillation of the Cognac wine. If the
best Cognac brandy be carefully distilled at a low heat, and the strong
spirit be diluted with water, it will be found to have suffered much in
its flavour.
Genuine French brandy evinces an acid reaction with litmus paper, owing
to a minute portion of vinegar; it contains besides some acetic ether,
and, when long kept in oak casks, a little astringent matter. The
following formula may be proposed for converting a silent or flavourless
corn spirit, into a factitious brandy. Dilute the pure alcohol to the
proof pitch, add to every hundred pounds weight of it from half a pound
to a pound of argol (crude winestone) dissolved in water, a little
acetic ether, and French-wine vinegar, some bruised French plums, and
flavour-stuff from Cognac; then distil the mixture with a gentle fire,
in an alembic furnished with an agitator.
The spirit which comes over may be coloured with nicely burned sugar
(caramel) to the desired tint, and roughened in taste with a few drops
of tincture of catechu or oak-bark.
The above recipe will afford a spirit free from the deleterious drugs
too often used to disguise and increase the intoxicating power of
British brandies; one which may be reckoned as wholesome as alcohol, in
any shape, can ever be.
BRASS. (_Laiton_, _cuivre jaune_, Fr.; _Messing_, Germ.) An alloy of
copper and zinc. It was formerly manufactured by cementing granulated
copper, called _bean-shot_, or copper clippings, with calcined calamine
(native carbonate of zinc) and charcoal, in a crucible, and exposing
them to bright ignition. Three parts of copper were used for three of
calamine and two of charcoal. The zinc reduced to the metallic state by
the agency of the charcoal, combined with the copper, into an alloy
which formed, on cooling, a lump at the bottom of the crucible. Several
of these, being remelted and cast into moulds, constituted ingots of
brass for the market. James Emerson obtained a patent, in 1781, for
making brass by the direct fusion of its two metallic elements, and it
is now usually manufactured in this way.
It appears that the best proportion of the constituents to form fine
brass is one prime equivalent of copper = 63-1/2 + one of zinc = 32·3;
or very nearly 2 parts of copper to 1 of zinc. The bright gold coloured
alloy, called Prince’s, or Prince Rupert’s metal, in this country,
consists apparently of two primes of zinc to one of copper, or of nearly
equal parts of each. Brass, or hard solder, consists of two parts of
brass and one of zinc melted together, to which a little tin is
occasionally added; but when the solder must be very strong, as for
brass tubes that are to undergo drawing, two thirds of a part of zinc
are used for two parts of brass. Mosaic gold, according to the
specification of Parker and Hamilton’s patent consists of 100 parts of
copper, and from 52 to 55 of zinc; which is no atomic proportion. Bath
metal is said to consist of 32 parts of brass and 9 parts of zinc.
The button manufacturers of Birmingham make their _platin_ with 8 parts
of brass and 5 of zinc; but their cheap buttons with an alloy of copper,
tin, zinc, and lead.
Red brass, the Tombak of some, (not of the Chinese, for this is white
copper,) consists of more copper and less zinc than go to the
composition of brass; being from 2-1/2 to 8 or 10 of the former to 1 of
the latter. At the famous brass works of Hegermühl, to be presently
described, 11 parts of copper are alloyed with 2 of zinc into a red
brass, from which plates are made that are afterwards rolled into
sheets. From such an alloy the Dutch foil, as it is called, is
manufactured at Nürnberg; Pinchbeck, Similor, Mannheim gold, are merely
different names of alloy similar to Prince’s metal. The last consists of
3 of copper and 1 of zinc, separately melted, and suddenly incorporated
by stirring.--_Wiegleb._
In the process of alloying two metals of such different fusibilities as
copper and zinc, a considerable waste of the latter metal by the
combustion, to which it is so prone, might be expected; but, in reality,
their mutual affinities seem to prevent the loss, in a great measure, by
the speedy absorption of the zinc into the substance of the copper.
Indeed, copper plates and rods are often _brassed_ externally by
exposure, at a high temperature, to the fumes of zinc, and afterwards
laminated or drawn. The spurious gold wire of Lyons is made from such
rods. Copper vessels may be superficially converted into brass by
boiling them in dilute muriatic acid, containing some winestone and zinc
amalgam.
The first step in making brass is to plunge slips of copper into melted
zinc till an alloy of somewhat difficult fusion be formed, to raise the
heat, and add the remaining proportion of the copper.
The brass of the first fusion is broken to pieces, and melted with a
fresh quantity of zinc, to obtain the finished brass. Each melting takes
about 8 or 9 hours. The metal is now cast into plates, about 40 inches
long by 26 inches broad, and from one third to one half inch thick. The
moulds are, in this case also, slabs of granite mounted in an iron
frame. Granite appears to be preferred to every thing else as a mould,
because it preserves the heat long, and by the asperities of its
surface, it keeps hold of the clay lute applied to secure the joinings.
The cast plates are most usually rolled into sheets. For this purpose
they are cut into ribands of various breadths, commonly about 6-1/2
inches. The cylinders of the brass rolling-press are generally 46 inches
long, and 18 inches in diameter. The ribands are first of all passed
cold through the cylinders; but the brass soon becomes too hard to
laminate. It is then annealed in a furnace, and, after cooling, is
passed afresh through a rolling press. After paring off the chipped
edges, the sheets are laminated two at a time: and if they are to be
made very thin, even eight plates are passed through together. The brass
in these operations must be annealed 7 or 8 times before the sheet
arrives at the required thinness. These successive heatings are very
expensive; and hence they have led the manufacturers to try various
plans of economy. The annealing furnaces are of two forms according to
the size of the sheets of brass. The smaller are about 12 feet long,
with a fire place at each end, and about 13 inches wide. The arch of the
furnace has a cylindrical shape, whose axis is parallel to its small
side. The hearth is horizontal, and is made of bricks set on edge. In
the front of the furnace there is a large door, which is raised by a
lever, or chain, and counterweight, and slides in a frame between two
cheeks of cast iron. This furnace has, in general, no chimney, except a
vent slightly raised above the door, to prevent the workmen being
incommoded by the smoke. Sometimes the arch is perforated with a number
of holes. The sheets of brass are placed above each other, but separated
by parings, to allow the hot air to circulate among them, the lowest
sheet resting upon two bars of cast iron placed lengthwise.
The large furnaces are usually 32 feet long, by 6-1/2 feet wide, in the
body, and 3 feet at the hearth. A grate, 13 inches broad, extends along
each side of the hearth, through its whole length, and is divided from
it by a small wall, 2 or 3 inches high. The vault of the furnace has a
small curvature, and is pierced with 6 or 8 openings, which allow the
smoke to pass off into a low bell-chimney above. At each end of the
furnace there is a cast-iron door, which slides up and down in an iron
frame, and is poised by a counterweight. On the hearth there is a kind
of railway, composed of two iron bars, on the grooves of which the
carriage moves with its loads of sheets of brass.
These sheets, being often 24 feet long, could not be easily moved in and
out of the furnace; but as brass laminates well in the cold state, they
are all introduced and moved out together. With this view, an iron
carriage is framed with four bars, which rest on four wheels. Upon this
carriage, of a length nearly equal to that of the furnace, the sheets
are laid, with brass parings between them. The carriage is then raised
by a crane to a level with the furnace, and entered upon the grooved
bars which lie upon the hearth. That no heat may be lost, two carriages
are provided, the one being ready to put in as the other is taken out;
the furnace is meanwhile uniformly kept hot. This method, however
convenient for moving the sheets in and out, wastes a good deal of fuel
in heating the iron carriage.
The principal places in which brass is manufactured on the great scale
in England, are Bristol, Birmingham, and Holywell, in North Wales.
The French writers affirm, that a brass, containing 2 _per cent._ of
lead, works more freely in the turning lathe, but does not hammer so
well as the mere alloy of copper and zinc.
At the brass manufactory of Hegermühl, upon the Finon canal near
Potsdam, the following are the materials of one charge; 41 pounds of old
brass, 55 pounds refined copper (gahrkupfer) granulated; and 24 pounds
of zinc. This mixture, weighing 120 pounds, is distributed into four
crucibles, and fused in a wind furnace with pitcoal fuel. The waste
varies from 2-1/2 to 4 pounds upon the whole.
[Illustration: 159 160]
_Fig._ 159. represents the furnace as it was formerly worked there with
charcoal; _a_, the laboratory in which the crucibles were placed. It was
walled with fire bricks. The foundations and the filling-in walls were
formed of stone rubbish, as being bad conductors of heat; sand and ashes
may be also used; _b_, cast-iron circular grating plates pierced with
12 holes (see _fig._ 160.), over them a sole of loam, _c_, is beat down,
and perforated with holes corresponding to those in the iron discs; _d_,
the ash-pit; _e_, the _bock_, a draught flue which conducts the air
requisite to the combustion, from a sunk tunnel, in communication with
several melting furnaces. The terrace or crown of the furnace, _f_, lies
on a level with the foundry floor, _h h_, and is shut with a tile of
fire-clay, _g_, which may be moved in any direction by means of hooks
and eyes in its binding iron ring. _Fig._ 161. the tongs for putting in
and taking out the charges, as viewed from above and from the side.
[Illustration: 161 162 163]
_Figs._ 162, 163. represent the furnaces constructed more recently for
the use of pitcoal fuel; _fig._ 162. being an upright section, and
_fig._ 163. the ground plan. In this furnace the crucibles are not
surrounded with the fuel, but they receive the requisite melting heat
from the flame proceeding from the grate upon which it is burned. The
crucibles stand upon 7 binding arches, _a_, which unite in the middle at
the key-stone _b_, _fig._ 163. Between the arches are spaces through
which the flame rises from the grate _c_. _d_ is the fire-door; _e_, a
sliding tile or damper for regulating or shutting off the air-draught;
_f_ an inclined plane, for carrying off the cinders that fall through
the grate, along the draught tunnel _g_, so that the air in entering
below may not be heated by them.
The crucibles are 16 inches deep, 9-1/2 wide at the mouth, 6-1/2 at the
bottom; with a thickness in the sides of 1 inch and 1-1/2 below; they
stand from 40 to 50 meltings. The old brass, which fills their whole
capacity, is first put in and melted down; the crucibles are now taken
out, and are charged with the half of the zinc in pieces of from 1 to 3
cubic inches in size, covered over with coal ashes; then one half of the
copper charge is introduced, again coal-dust; and thus the layers of
zinc and copper are distributed alternately with coal-ashes betwixt
them, till the whole charge gets finally fused. Over all, a thicker
layer of carbonaceous matter is laid, to prevent oxidizement of the
brass. Eight crucibles filled in this way are put into the furnace
between the 11 holes of the grate shelf; and over them two empty
crucibles are laid to be heated for the casting operation. In from 3-1/2
to 4 hours the brass is ready to be poured out. Fifteen English bushels
of coals are consumed in one operation; of which six are used at the
introduction of the crucibles, and four gradually afterwards.
When sheet brass is to be made the following process is pursued:--
An empty crucible, called a _caster_ (_giesser_), is taken out of the
furnace through the crown with a pair of tongs, and is kept red hot by
placing it in a hollow hearth (_mundal_), surrounded with burning coals;
into this crucible the contents of four of the melting pots are poured;
the dross being raked out with an iron scraper. As soon as the melting
pot is emptied, it is immediately re-charged in the manner above
described, and replaced in the furnace. The surface of the melted brass
in the _caster_ is swept with the stump of a broom, then stirred about
with the iron rake, to bring up any light foreign matter to the surface,
which is then skimmed with a little scraper; the crucible is now seized
with the casting tongs, and emptied in the following way:--
[Illustration: 164 165]
The mould or _form_ for casting sheet brass consists of two slabs of
granite, _a a_, _figs._ 164, 165. They are 5-1/2 feet long; 3 feet
broad, 1 foot thick, and, for greater security, girt with iron bands, _b
b_, 2 inches broad, 1-1/2 thick, and joined at the four corners with
bolts and nuts. The mould rests upon an oaken block, _c_, 3-1/2 feet
long, 2-1/6 broad, and 1-1/4 thick, which is suspended at each end upon
gudgeons, in bearing blocks, placed under the foundery floor, _d d_, in
the casting pit, _e e_. This is lined with bricks; and is 6-3/4 feet
long, 5-1/2 broad, and 2 deep; upon the two long side walls of the pit,
the bearing blocks are laid, which support the gudgeons. The
swing-blocks are 10 inches long, 18 inches broad, 15 inches thick, and
are somewhat rounded upon their back edge, so that the casting frame may
slope a little to the horizon. To these blocks two cross wooden arms, _f
f_, are mortised, upon which the under slab rests, freely, but so as to
project about 5 inches backwards over the block, to secure an equipoise
in the act of casting. _g g_ are bars, placed at both of the long sides,
and one of the ends, between the slabs, to determine the thickness of
the brass-plate. Upon the other slab the gate _h_ is fastened, a sheet
of iron 6 inches broad, which has nearly the shape of a parallel
trapezium (lozenge), and slopes a little towards the horizon. It serves
for setting the casting pot upon in the act of pouring out, and renders
its emptying more convenient. That gate (_steinmaul_) is coated with a
mixture of loam and hair. The upper slab is secured to the under one in
its slanting position by an _armour_ or binding. This consists of the
tension bars of wood, _i k l m_, of the iron bars _n_, (3 to 3-1/2
inches broad, 1-1/2 inch thick, see the top view, _fig._ 165.) of a rod
with holes and pins at its upper end, and of the iron screw spindle _o_.
The mode in which these parts act may be understood from inspection of
the figure. In order to lift the upper slab from the under one, which is
effected by turning it round its edge, a chain is employed, suspending
two others, connected with the slab. The former passes over a pulley,
and may be pulled up and down by means of a wheel and axle, or with the
aid of a counterweight. Upon each of the two long sides of the slab
there are two iron rings, to which the ends of the chains may be hooked.
The casting faces of the slab must be coated with a layer of finely
ground loam; the thinner the better.
When calamine is employed, 1/2 cwt. of copper, 3/4 cwt. of calamine, and
1/3 the volume of both of charcoal mixed, are put into 7 crucibles, and
exposed to heat during 11 or 12 hours; the product being from 70 to 72
lbs. of brass.
_Brass-plate rolling._--At Hegermühl there are two re-heating or
annealing furnaces, one larger, 18 feet long, and another smaller,
8-1/2; the hot chamber is separated from the fire place by iron beams,
in such a way that the brass castings are played upon by the flames on
both their sides. After each passage through the laminating press
(rolls) they are heated anew, then cooled and laminated afresh, till
they have reached the proper length. The plates are besmeared with
grease before rolling.
[Illustration: 166 167 168]
_Fig._ 166. shows the ground plan of the furnace and its railway; _fig._
167. the cross section; and _fig._ 168. the section lengthwise; _a a_,
the iron way bars or rails upon the floor of the foundry, for enabling
the wheels of the waggon-frame to move readily backwards and forwards;
_b b_, the two grates; _c c_, the ash pits; _d d_, the fire beams; _e e
e_, vents in the roof of the hot chamber _f_; _g g_, two plates for
shutting the hot chamber; _h_, the flue; _i_, the chimney. After the
rolling, the sheets covered with a black oxide of copper, are plunged
into a mother water of the alum works for a few minutes, then washed in
clean water, and lastly, smeared with oil and scraped with a blunt
knife.
In rough brass and brass wares, no less than 16,240 cwts. were
manufactured in the Prussian States in the year 1832.
For musical purposes, the brass wire made in Berlin, has acquired great
and merited celebrity; but that of Birmingham is now preferred even by
foreigners.
BRASS COLOUR, for staining glass, is prepared by exposing for several
days thin plates of brass upon tiles in the _leer_ or annealing arch of
the glass-house, till it be oxidized into a black powder, aggregated in
lumps. This being pulverized and sifted, is to be again well calcined
for several days more, till no particles remain in the metallic state;
when it will form a fine powder of a russet brown colour. A third
calcination must now be given, with a carefully regulated heat; its
quality being tested from time to time by fusion with some glass. If it
makes the glass swell, and intumesce, it is properly prepared; if not,
it must be still farther calcined. Such a powder communicates to glass,
greens of various tints, passing into turquoise.
When thin narrow strips of brass are stratified with sulphur in a
crucible, and calcined at a red heat, they become friable, and may be
reduced to powder. This being sifted and exposed upon tiles in a
reverberatory furnace for ten or twelve days, becomes fit for use, and
is capable of imparting a calcedony, red or yellow tinge to glass by
fusion, according to the mode and proportion of using it.
The glass-makers’ red colour may be prepared by exposing small plates of
brass to a moderate heat in a reverberatory furnace, till they are
thoroughly calcined, when the substance becomes pulverulent, and assumes
a red colour. It is then ready for immediate use.
BRASS COLOUR, as employed by the colourmen to imitate brass, is of two
tints, the red or bronze, and the yellow like gilt brass. Copper filings
mixed with red ochre or bole, constitute the former; a powdered brass
imported from Germany is used for the latter. Both must be worked up
with varnish after being dried with heat, and then spread with a flat
camel-hair brush evenly upon the surface of the object. The best varnish
is composed of 20 ounces of spirits of wine, 2 ounces of shellac, and 2
ounces of sandarach, properly dissolved. See VARNISH. Only so much of
the brass powder and varnish should be mixed at a time as is wanted for
immediate use.
BRASS FOIL. Dutch leaf, called _Knitter_ or _Rauschgold_ in Germany, is
made from a very thin sheet brass, beat out under a hammer worked by
water power, which gives 300 or 400 strokes per minute; from 40 to 80
leaves being laid over each other. By this treatment it acquires its
characteristic solidity and lustre. See above, the process for
converting the copper superficially into brass by the fumes of zinc.
BRAZING. (_Braser_, Fr.; _Messing-lothung_, Germ.) The soldering
together of edges of iron, copper, brass, &c., with an alloy consisting
of brass and zinc, sometimes with a little tin or silver. The surfaces
to be thus united must be filed perfectly bright, and not be soiled with
the fingers or in any other way. The granular or nearly pulverulent
alloy is usually wetted with a paste of ground borax and water, applied
in this state, dried, and then exposed carefully to bright ignition at a
clear forge fire. Some workmen enclose the part to be soldered in a clay
lute, but others prefer leaving it uncovered, that they may see when the
solder has flowed freely, and entered into all the seams.
BRAZIL-WOOD. (_Bois de Fernambouc_, Fr.; _Brasilienholz_, Germ.) This
dye-wood derives its name from the part of America whence it was first
imported. It has also the names Fernambuca, wood of Saint Martha, and of
Sapan, according to the places which produce it. Linnæus distinguishes
the tree which furnishes the Brazil wood by the name of _Cæsalpinia
crista_. It commonly grows in dry places among rocks. Its trunk is very
large, crooked, and full of knots. It is very hard, susceptible of a
fine polish, and sinks in water. It is pale when newly cleft, but
becomes red on exposure to the air.
It has different shades of red and orange. Its goodness is determined
particularly by its density. When chewed, a saccharine taste is
perceived. It may be distinguished from red saunders wood, as the latter
does not yield its colour to water.
Boiling water extracts the whole colouring matter of Brazil-wood. If the
ebullition be long enough continued, it assumes a fine red colour. The
residuum appears black. In this case, an alkali may still extract much
colouring matter. The solution in alcohol or ammonia is still deeper
than the preceding.
The decoction of Brazil-wood, called juice of Brazil, is observed to be
less fit for dyeing when recent, than when old or even fermented. By age
it takes a yellowish-red colour. For making this decoction, Hellot
recommends to use the hardest water; but it should be remarked, that
this water deepens the colour in proportion to the earthy salts which it
contains. After boiling this wood reduced to chips, or, what is
preferable, to powder, for three hours, this first decoction is poured
into a cask. Fresh water is poured on the wood, which is then made to
boil for three hours, and mixed with the former. When Brazil-wood is
employed in a dyeing bath, it is proper to enclose it in a thin linen
bag, as well as all the dye woods in general.
Wool immersed in the juice of Brazil takes but a feeble tint, which is
speedily destroyed. It must receive some preparations.
The wool is to be boiled in a solution of alum, to which a fourth or
even less of tartar is added, for a larger proportion of tartar would
make the colour yellowish. The wool is kept impregnated with it for at
least eight days, in a cool place. After this, it is dyed in the Brazil
juice with a slight boiling. But the first colouring particles that are
deposited, afford a less beautiful colour; hence it is proper to pass a
coarser stuff previously through the bath. In this manner a lively red
is procured, which resists pretty well the action of the air.
Brazil-wood is made use of for dyeing silk what is called false crimson,
to distinguish it from the crimson made by means of cochineal, which is
much more permanent.
The silk should be boiled at the rate of 20 parts of soap per cent., and
then alumed. The aluming need not be so strong as for the fine crimson.
The silk is refreshed at the river, and passed through a bath more or
less charged with Brazil juice, according to the shade to be given. When
water free from earthy salts is employed, the colour is too red to
imitate crimson; this quality is given it by passing the silk through a
slight alkaline solution, or by adding a little alkali to the bath. It
might, indeed, be washed in a hard water till it had taken the desired
shade.
To make deeper false crimsons of a dark red, juice of logwood is put
into the Brazil bath after the silk has been impregnated with it. A
little alkali may be added, according to the shade that is wanted.
To imitate poppy or flame colour, an annotto ground is given to the
silk, deeper even than when it is dyed with carthamus. It is washed,
alumed, and dyed with juice of Brazil, to which a little soap water is
usually added.
The colouring particles of Brazil wood are easily affected, and made
yellow by the action of acids.
They thus become permanent colours. But what distinguishes them from
madder and kermes, and approximates them to cochineal, is their
reappearing in their natural colour, when they are thrown down in a
state of combination with alumina, or with oxide of tin. These two
combinations seem to be the fittest for rendering them durable. It is
requisite, therefore, to inquire what circumstances are best calculated
to promote the formation of these combinations, according to the nature
of the stuff.
The astringent principle, likewise, seems to contribute to the
permanence of the colouring matter of Brazil wood; but it deepens its
hue, and can only be employed for light shades.
The colouring particles of Brazil wood are very sensible to the action
of alkalies which give them a purple hue; and there are several
processes in which the alkalies, either fixed or volatile, are used for
forming violets and purples. But the colours obtained by these methods,
which may be easily varied according to the purpose, are perishable, and
possess but a transient bloom. The alkalies appear not to injure the
colours derived from madder, but they accelerate the destruction of most
other colours.
In England and Holland the dye-woods are reduced to powder by means of
mills erected for the purpose.
The bright fugitive red, called fancy red, is given to cotton by
Nicaragua, or peachwood, a cheap kind of Brazil wood.
The cotton being scoured and bleached, is boiled with sumach. It is then
impregnated with a solution of tin (at 5° Baumé, according to Vitalis).
It should now be washed slightly in a weak bath of the dyeing wood, and
lastly, worked in a somewhat stale infusion of the peach or Brazil wood.
When the temperature of this is lukewarm, the dye is said to take
better. Sometimes two successive immersions in the bath are given. It is
now wrung out, aired, washed in water, and dried.
M. Vitalis says, that his solution of tin is prepared with two ounces of
tin and a pound of aqua regia made with two parts of nitric acid at 24°
Baumé, and three parts of muriatic acid at 22°.
For a rose colour, the cotton is alumed as usual, and washed from the
alum. It then gets the tin mordant, and is again washed. It is now
turned through the dye-bath, an operation which is repeated if
necessary.
For purple a little alum is added to the Brazil bath.
1. For amaranth, the cotton is strongly galled, dried, and washed.
2. It is passed through the black cask (tonneau noir), see BLACK DYE,
till it has taken a strong grey shade.
3. It receives a bath of lime water.
4. Mordant of tin.
5. Dyeing in the Brazil wood bath.
6. The two last operations are repeated.
Dingler has endeavoured to separate the colouring matter of the
different sorts of Brazil wood, so as to obtain the same tint from the
coarser as from the best Pernambuco. His process consists in treating
the wood with hot water or steam, in concentrating the decoction so as
to obtain 14 or 15 pounds of it from 4 pounds of wood, allowing it to
cool, and pouring into it two pounds of skim milk; agitating, then
boiling for a few minutes, and filtering. The dun colouring matters are
precipitated by the coagulation of the caseous substance. For dyeing,
the decoctions must be diluted with water; for printing they must be
concentrated, so that 4 pounds of wood shall furnish only 5 or 6 pounds
of decoction, and the liquor may be thickened in the ordinary way. These
decoctions may be employed immediately, as by this treatment they have
acquired the same property as they otherwise could get only by being
long kept. A slight fermentation is said to improve the colour of these
decoctions; some ground wood is put into the decoction to favour this
process.
As gelatine produces no precipitate with these decoctions, they
consequently contain no tannin. Gall-nuts, however, sumach, the bark of
birch or alder, render the colour of Brazil wood more durable, upon
alumed linen and cotton goods, but the shade is a little darker.
In dyeing wool with Pernambuco, the temperature of the bath should never
be above 150° Fahr., since higher heats impair the colour.
According to Dingler and Kurrer, bright and fast scarlet reds may be
obtained upon wool, by preparing a decoction of 50 pounds of Brazil wood
in three successive boils, and setting the decoction aside for 3 or 4
weeks in a cool place; 100 pounds of the wool are then alumed in a bath
of 22 pounds of alum and 11 pounds of tartar, and afterwards rinsed in
cold water. Meanwhile we fill two-thirds with water, a copper containing
30 pails, and heated to the temperature of 150° or 160° F. We pour in 3
pailfuls of the decoction, heat to the same point again, and introduce
30 pounds of wool, which does not take a scarlet, but rather a crimson
tint. This being removed, 2 pails of decoction are put in, and 30 pounds
of wool which becomes scarlet, but not so fine as at the third dip. If
the dyer strengthens the colour a little at the first dip, a little more
at the second, and adds at the third and fourth the quantity of
decoction merely necessary, he will obtain an uniform scarlet tint. With
50 pounds of Pernambuco 1000 pounds of wool may be dyed scarlet in this
way, and with the deposits another 100 may be dyed of a tile colour. An
addition of weld renders the colour faster but less brilliant.
Karkutsch says the dye may be improved by adding some ox-gall to the
bath.
In dyeing cotton the tannin and gallic acid are two necessary mordants,
and the colour is particularly bright and durable, when the cloth has
been prepared with the oily process of Turkey red.
It is said that stale urine heightens the colour of the Brazil dye when
the ground wood is moistened with it.
The quantity of Brazil or Nicaragua wood imported into the United
Kingdom in 1835, was 6,242 tons, whereof 1,811 were exported; of
Brazilietto 230 tons. The duty upon the first article is 5_s._ per ton.
BREAD (_Pain_, Fr.; _Brod_, Germ.) is the spongy mass produced by baking
the leavened or fermented dough of wheat or rye flour, at a proper heat.
It is the principal food of highly civilized nations. The skilful
preparation of this indispensable article constitutes the art of the
Baker. Dough baked without being fermented constitutes cakes or
biscuits; but not bread strictly speaking.
Pliny informs us, that barley was the only species of corn at first used
for food; and even after the method of reducing it to flour had been
discovered, it was long before mankind learned the art of converting it
into cakes.
Ovens were first invented in the East. Their construction was understood
by the Jews, the Greeks, and the Asiatics, among whom baking was
practised as a distinct profession. In this art, the Cappadocians,
Lydians, and Phœnicians, are said to have particularly excelled. It was
not till about 580 years after the foundation of Rome, that these
artisans passed into Europe. The Roman armies, on their return from
Macedonia, brought Grecian bakers with them into Italy. As these bakers
had handmills beside their ovens, they still continued to be called
_pistores_, from the ancient practice of bruising the corn in a mortar;
and their bakehouses were denominated _pistoriæ_. In the time of
Augustus there were no fewer than 329 public bakehouses in Rome; almost
the whole of which were in the hands of Greeks, who long continued the
only persons in that city acquainted with the art of baking good bread.
In nothing, perhaps, is the wise and cautious policy of the Roman
government more remarkably displayed, than in the regulations which it
imposed on the bakers within the city. To the foreign bakers who came to
Rome with the army from Macedonia, a number of freedmen were associated,
forming together an incorporation from which neither they nor their
children could separate, and of which even those who married the
daughters of bakers were obliged to become members. To this
incorporation were entrusted all the mills, utensils, slaves, animals,
every thing, in short, which belonged to the former bakehouses. In
addition to these, they received considerable portions of land; and
nothing was withheld, which could assist them in pursuing, to the best
advantage, their highly prized labours and trade. The practice of
condemning criminals and slaves, for petty offences, to work in the
bakehouse, was still continued; and even the judges of Africa were bound
to send thither, every five years, such persons as had incurred that
kind of chastisement. The bakehouses were distributed throughout the
fourteen divisions of the city, and no baker could pass from one into
another without special permission. The public granaries were committed
to their care; they paid nothing for the corn employed in baking bread
that was to be given in largess to the citizens; and the price of the
rest was regulated by the magistrates. No corn was given out of these
granaries except for the bakehouses, and for the private use of the
prince. The bakers had besides private granaries, in which they
deposited the grain, which they had taken from the public granaries for
immediate use; and if any of them happened to be convicted of having
diverted any portion of the grain to another purpose, he was condemned
to a ruinous fine of five hundred pounds weight of gold.
Most of these regulations were soon introduced among the Gauls; but it
was long before they found their way into the more northern countries of
Europe. Borrichius informs us that in Sweden and Norway, the only bread
known, so late as the middle of the 16th century, was unleavened cakes
kneaded by the women. At what period in our own history the art of
baking became a separate profession, we have not been able to ascertain;
but this profession is now common to all the countries in Europe, and
the process of baking is also nearly the same.
The French, who particularly excel in the art of baking, have a great
many different kinds of bread. Their _pain bis_, or brown bread, is the
coarsest kind of all, and is made of coarse groats mixed with a portion
of white flour. The _pain bis blanc_, is a kind of bread between white
and brown, made of white flour and fine groats. The _pain blanc_, or
white bread, is made of white flour, shaken through a sieve after the
finest flour has been separated. The _pain mollet_, or soft bread, is
made of the purest flour without any admixture. The _pain chaland_, or
customers’ bread, is a very white kind of bread, made of pounded paste.
_Pain chapelé_, is a small kind of bread, with a well-beaten and very
light paste, seasoned with butter or milk. This name is also given to a
small bread, from which the thickest crust has been removed by a knife.
_Pain cornu_, is a name given by the French bakers to a kind of bread
made with four corners, and sometimes more. Of all the kinds of small
bread, this has the strongest and firmest paste. _Pain à la reine_,
queen’s bread, _pain à la Sigovie_, _pain chapelé_, and _pain cornu_,
are all small kinds of bread, differing only in the lightness or
thickness of the paste. _Pain gruau_ is a small very white bread made
now in Paris, from the flour separated after a slight grinding from the
best wheat. Such flour is in hard granular particles.
In this country we have fewer varieties of bread, and these differ
chiefly in their degrees of purity. Our white or fine bread is made of
the purest flour; our wheaten bread, of flour with a mixture of the
finest bran; and our household bread, of the whole substance of the
grain without the separation either of the fine flour or coarse bran. We
have also symnel bread, manchet or roll bread, and French bread, which
are all made of the purest flour from the finest wheat; the roll bread
being improved by the addition of milk, and the French bread by the
addition of eggs and butter. To these may be added gingerbread, a cake
made of flour, with almonds, liquorice, aniseed, rose-water, and sugar
or treacle; and mastlin bread, made of wheat and rye, or sometimes of
wheat and barley. We have various kinds of small bread, having various
names, according to their various forms. They are, in general, extremely
light, and are sweetened with sugar, currants, and other palatable
ingredients. In Scotland there is a cake called _short bread_, made from
a pretty thick dough, enriched with butter, sweetened with sugar, and
seasoned with orange peel, or other kinds of spices.
The process of making bread is nearly the same in all the countries of
modern Europe; though the materials of which it as composed vary with
the farinaceous productions of different climates and soils. The flour
of wheat is most generally employed for this purpose, wherever that
vegetable can be reared. This flour is composed of a small portion of
mucilaginous saccharine matter, soluble in cold water, from which it may
be separated by evaporation; of a great quantity of starch, which is
scarcely soluble in cold water, but capable of combining with that fluid
by means of heat; and an adhesive gray substance called gluten,
insoluble in water, ardent spirit, oil, or ether, and resembling an
animal substance in many of its properties. Flour kneaded with water,
forms a tough rather indigestible paste containing all the constituent
parts which we have enumerated. Heat produces a considerable change on
the glutinous part of this compound, and renders it more easy of
mastication and digestion. Still, however, it continues heavy and tough,
compared with bread which is raised by leaven or yeast. Leaven is
nothing more than a piece of dough, kept in a warm place till it
undergoes a process of fermentation; swelling, becoming spongy, or full
of air bubbles, at length disengaging an acidulo-spirituous vapour, and
contracting a sour taste. When this leaven is mingled in proper
proportions with fresh-made dough, it makes it rise more readily and
effectually than it would do alone, and gives it at the same time a
greater degree of firmness. Upon the quality of the leaven employed, the
quality of the bread materially depends.
The principal improvement which has been made on bread in modern times,
is the substitution of yeast or barm in place of common leaven. This
yeast is the viscid froth that rises to the surface of beer, in the
first stage of its fermentation. When mixed with the dough, it makes it
rise much more speedily and effectually than ordinary leaven, and the
bread is of course much lighter, and freer from that sour and
disagreeable taste which may often be perceived in bread raised with
leaven, either because too much is mingled with the paste, or because it
has been allowed to advance too far in the process of fermentation.
Bread properly raised and baked, differs materially from unleavened
cakes, not only in being less compact and heavy, and more agreeable to
the taste, but in losing its tenacious and glutinous qualities, and thus
becoming more salutary and digestible.
We possess several analyses of wheat flour. Ordinary wheat (_triticum
hybernum mixed with triticum turgidum_) contains, according to the
analyses made by Vauquelin of several species of wheat flour, the
following substances:--
+--------------------------+------+-------+-------+------+
| | | | | |
| Species of Wheat. |Water.|Gluten.|Starch.|Sugar.|
| | | | | |
+--------------------------+------+-------+-------+------+
|French wheat flour | 10·0 | 10·96 | 71·49 | 4·72 |
|Hard wheat of Odessa flour| 12·0 | 14·55 | 56·50 | 8·48 |
|Soft wheat of Odessa flour| 10·0 | 12·00 | 62·00 | 7·56 |
|Same sort of flour | 8·0 | 12·10 | 70·84 | 4·90 |
|Same sort of flour | 12·0 | 7·30 | 72·00 | 5·42 |
|Wheat of the French bakers| 10·0 | 10·20 | 72·80 | 4·20 |
|Flour of the Paris hos- | 8·0 | 10·30 | 71·20 | 4·80 |
|pitals (2d quality) | | | | |
|Ditto (3d quality) | 12·0 | 9·02 | 67·78 | 4·80 |
+--------------------------+------+-------+-------+------+
+--------------------------+------+-----+------+------+
| | | | |Water |
| Species of Wheat. | Gum. |Bran.|Total.| of |
| | | | |dough.|
+--------------------------+------+-----+------+------+
|French wheat flour | 3·32 | - |100·49| 50·3 |
|Hard wheat of Odessa flour| 4·90 | 2·3 | 98·73| 51·2 |
|Soft wheat of Odessa flour| 5·80 | 1·2 | 98·42| 54·8 |
|Same sort of flour | 4·60 | - |100·41| 37·4 |
|Same sort of flour | 3·30 | - |100·02| 37·2 |
|Wheat of the French bakers| 2·80 | - |100·00| 40·6 |
|Flour of the Paris hos- | 3·60 | - | 97·90| 37·8 |
|pitals (2d quality) | | | | |
|Ditto (3d quality) | 4·60 | 2·0 |100·21| 37·8 |
+--------------------------+------+-----+------+------+
The following table of analyses merits also a place here.
+------------------+------+-------+-------+------+-------+-----+-----+
|Species of Flour. |Water.|Gluten.|Starch.|Sugar.|Gummi- |Albu-|Bran.|
| | | | | |gluten.|men. | |
+------------------+------+-------+-------+------+-------+-----+-----+
|Flour of the | 1 | 22· | 74· | 5·50| 1· | 1·50| |
|triticum spelta | | | | | | | |
|Ditto triticum | 1 | 24· | 68· | 5·0 | 1· | 1·50| |
|hybernum | | | | | | | |
|Ditto common wheat| - | 12·5 | 74·5 | 12· | 2· | | |
|Ditto wheat and | 6 | 9·80 | 75·50 | 4·22| 3·28 | - | 1·2 |
|rye mixed | | | | | | | |
|(mastlin) | | | | | | | |
+------------------+------+-------+-------+------+-------+-----+-----+
The first two of the above analyses were made by Vogel, the third by
Proust, and the fourth by Vauquelin.
Analyses of the flour of some other corns.
+---------+-------+-----+----+-----+---------+-------------+-----+
|Species |Starch.|Muci-|Glu-|Albu-| Sugar. | Husk. |Hor- |
|of Flour.| |lage.|ten.|men. | | |dein.|
+---------+-------+-----+----+-----+---------+-------------+-----+
| | | | | | |Of a fat oil,| |
|White | 59·00 | 2·5 | - |4·30 | 8·25 | 2 | |
|oatmeal | | | | |Of resin,| | |
|Barley | 32·00 | 9· | 3· | - | 2 | - | 55 |
|meal | | | | | | | |
+---------+-------+-----+----+-----+---------+-------------+-----+
The first analysis is by Vogel, the second by Proust.
It deserves to be remarked, that the flour of Odessa contains a much
greater quantity of sugar than the French flour. The substance indicated
in the preceding table by the name of gluten, is the gluten of Beccaria,
that is to say, a mixture of gluten and vegetable albumen. The gum of
wheat is not quite identical with ordinary gum. It is a brown azotised
substance, which, when treated by nitric acid, affords no mucic acid,
but oxalic acid and the bitter principle of Welter. It contains besides
superphosphate of lime.
The last column of the first table exhibits the quantity of water
necessary to convert the flour into dough of the ordinary consistence,
and it is usually proportional to the quantity of gluten. The hard wheat
of Odessa forms an exception in this respect; the reason of the
difference being that the starch contained in this flour is not as in
ordinary flour in a fine powder, but in small transparent grains, which
resemble pounded gum, and absorb less water than pulverulent starch.
The _triticum monococcon_, according to Zenneck, contains in its
unsifted flour, 16·334 of gluten and vegetable albumen; 64·838 of
starch; 11·347 of gum, sugar, and extractive; 7·481 of husks. The sifted
flour affords 15·536 of gluten and vegetable albumen; 76·459 of starch;
7·198 of sugar, gum, and extractive; 0·807 of husky matter. It is
difficult to conceive how such great quantities of gluten, albumen, and
extractive matter, could disappear in the sifting. The triticum spelta
contains in 100 parts of the finest flour, 22·5 of a soft and humid
gluten, mixed with vegetable albumen; 74 of starch, and 5·5 of sugar.
Here we have an excess of 2 parts in the 100.
Wheat furnishes very little ashes by incineration, not more than 0·15
per cent. of the weight; containing superphosphates of soda, lime, and
magnesia.
The object of baking is to combine the gluten and starch of the flour
into a homogeneous substance, and to excite such a vinous fermentative
action, by means of its saccharine matter, as shall disengage abundance
of carbonic acid gas in it for making an agreeable, soft, succulent,
spongy, and easily digestible bread. The two evils to be avoided in
baking are, hardness on the one hand, and pastiness on the other.
Well-made bread is a chemical compound, in which the gluten and starch
cannot be recognized or separated, as before, by a stream of water. When
flour is kneaded into a dough, and spread into a cake, this cake, when
baked, will be horny if it be thin, or if thick, will be tough and
clammy; whence we see the value of that fermentative process, which
generates thousands of little cells in the mass or crumb, each of them
dry, yet tender and succulent, through the intimate combination of the
moisture. By this constitution it becomes easily soluble in the juices
of the stomach, or in other words, light of digestion. It is moreover
much less liable to turn sour than cakes made from unfermented dough.
Rye, which also forms a true spongy bread, though inferior to that of
wheat, consists of similar ingredients; namely, 61·07 of starch; 9·48 of
gluten; 3·28 of vegetable albumen; 3·28 of uncrystallizable sugar; 11·09
of gum; 6·38 of vegetable fibre; the loss upon the 100 parts amounted to
5·62, including an acid whose nature the analyst, M. Einhof, did not
determine. Rye flour contains also several salts, principally the
phosphates of lime and magnesia. This kind of grain forms a
dark-coloured bread reckoned very wholesome; comparatively little used
in this country, but very much in France, Germany, and Belgium.
Dough fermented with the aid either of leaven or yeast, contains little
or none of the saccharine matter of the flour, but in its stead a
certain portion, nearly half its weight, of spirit, which imparts to it
a vinous smell, and is volatilized in the oven; whence it might be
condensed into a crude weak alcohol, on the plan of Mr. Hick’s patent,
were it worth while. But the increased complexity of the baking
apparatus, will probably prove an effectual obstacle to the commercial
success of this project, upon which already upwards of 20,000_l._
sterling have been squandered.
That the sugar of the flour is the true element of the fermentation
preposterously called panary, which dough undergoes, and that the starch
and gluten have nothing to do with it, may be proved by decisive
experiments. The vinous fermentation continues till the whole sugar is
decomposed, and no longer; when if the process be not checked by the
heat of baking, the acetous fermentation will supervene. Therefore if a
little sugar be added to a flour which contains little or none, its
dough will become susceptible of fermenting, with extrication of gas, so
as to make spongy succulent bread. But since this sponginess is produced
solely by the extrication of gas, and its expansion in the heat of the
oven, any substance capable of emitting gas, or of being converted into
it under these circumstances, will answer the same purpose. Were a
solution of bicarbonate of ammonia obtained by exposing the common
sesqui-carbonate in powder for a day to the air, incorporated with the
dough, in the subsequent firing it will be converted into vapour, and in
its extrication render the bread very porous. Nay, if water highly
impregnated with carbonic acid gas be used for kneading the dough, the
resulting bread will be somewhat spongy. Could a light article of food
be prepared in this way, then as the sugar would remain undecomposed,
the bread would be so much the sweeter, and the more nourishing. How far
a change propitious to digestion takes place in the constitution of the
starch and gluten, during the fermentative action of the dough, has not
been hitherto ascertained by precise experiments. Medical practitioners,
who derive an enormous revenue from dyspepsia, should take some pains
to investigate this subject.
Dr. Colquhoun, in his able essay upon the art of making bread, has shown
that its texture when prepared by a sudden formation and disengagement
of elastic fluid generated within the oven, differs remarkably from that
of a loaf which has been made after the preparatory fermentation with
yeast. Bread which has been raised with the common carbonate of ammonia
as used by the pastry-cooks, is porous no doubt, but not spongy with
vesicular spaces, like that made in the ordinary way. The former kind of
bread never presents that air-cell stratification which is the boast of
the Parisian baker, but which is almost unknown in London. I have found
it moreover very difficult to expel by the oven the last portion of the
ammonia, which gives both a tinge and a taste to the bread. I believe,
however, that the bicarbonate would be nearly free from this objection,
which operates so much against the sesqui-carbonate of the shops.
In opposition to Mr. Edlin’s account of the excellent quality of bread
made by impregnating dough with carbonic acid gas[10], Dr. Colquhoun
adduces Vogel’s experiments, which show that such dough, when baked,
after having been kept in a warm situation during the usual time,
afforded nothing better than a hard cake, which had no resemblance to
common bread. Vogel further states, as illustrative of the general
necessity of providing a sufficient supply of disengaged elastic fluid
within the dough, before baking it at all, that when he made various
attempts to form a well-raised vesicular loaf, within the oven, by
mixing flour with carbonate of magnesia, or with zinc filings, and then
kneading it into a paste by means of water, acidulated with sulphuric
acid, he always met with complete failure and disappointment. Dr.
Colquhoun performed a series of well-devised experiments on this
subject, which fully confirmed Vogel’s results, and prove that a proper
spongy bread cannot be made by the agency of either carbonic acid water,
or of mixtures of sesqui-carbonate of soda, and tartaric acid. The bread
proved doughy and dense in every case, though less so with the latter
mixture than the former. No loaf bread can, indeed, be well made by any
of these two extemporaneous systems, because they are inconsistent with
the thorough kneading of the dough. It is this process which renders
dough at once elastic enough to expand when carbonic acid gas is
generated within it, and cohesive enough to confine the gas when it is
generated. The whole gas of the loaf is disengaged in its interior by a
continuous fermentation, after all the processes of kneading have been
finished; for the loaf, after being kneaded, weighed out, and shaped, is
set aside till it expands gradually to double its bulk, before it is put
into the oven. But when a dough containing sesqui-carbonate of soda is
mixed with one containing muriatic acid, in due proportions to form the
just dose of culinary salt, the gas escapes during the necessary
incorporation of the two, and the bread formed from it is dense and
hard. Dr. Whiting has, however, made this old chemical process the
subject of a new patent for baking bread.
[10] Treatise on the Art of Bread Making, p. 56.
When the baker prepares his dough, he takes a portion of the water
needed for the batch, having raised its temperature to from 70° to 100°
F., dissolves a certain proportion of his salt in it, then adds the
yeast, and a certain quantity of his flour. This mixture, called the
_sponge_, is next covered up in the small kneading-trough, alongside of
the large one, and let alone for _setting_ in a warm situation. In about
an hour, signs of vinous fermentation appear, by the swelling and
heaving up of the sponge, in consequence of the generation of carbonic
acid; and if it be of a semi-liquid consistence, large air bubbles will
force their way to the surface, break, and disappear in rapid
succession. But when the _sponge_ has the consistence of thin _dough_,
it confines the gas, becomes thereby equably and progressively inflated
to double its original volume; when no longer capable of containing the
pent-up air, it bursts and subsides. This process of rising and falling
alternately might be carried on during twenty-four hours, but the baker
has learned by experience to guard against allowing full scope to the
fermentative principle. He generally interferes after the first, or at
furthest after the second or third dropping of the sponge; for were he
not to do so, the bread formed with such dough would invariably be found
sour to the taste and the smell. Therefore he adds at this stage to the
sponge the reserved proportions of flour, salt, and water, which are
requisite to make the dough of the desired consistence and size; and
next incorporates the whole together by a long and laborious course of
kneading. When this operation has been continued till the fermenting and
the fresh dough have been intimately blended, and till the glutinous
matter of both is worked into such union and consistence that the mass
becomes so tough and elastic as to receive the smart pressure of the
hand without adhering to it, the kneading is suspended for some time.
The dough is now abandoned to itself for a few hours, during which it
continues in a state of active fermentation throughout its entire mass.
Then it is subjected to a second but much less laborious kneading, in
order to distribute the generated gas as evenly as possible among its
parts, so that they may all partake equally of the vesicular structure.
After this second kneading, the dough is weighed out into the portions
suitable to the size of bread desired; which are of course shaped into
the proper forms, and once more set aside in a warm situation. The
continuance of the fermentation soon disengages a fresh quantity of
carbonic acid gas, and expands the lumps to about double their pristine
volume. These are now ready for the oven, and when they finally quit it
in the baked state, are about twice the size they were when they went
in. The generation of the due quantity of gas should be complete before
the lumps are transferred to the oven; because whenever they encounter
its heat, the process of fermentation is arrested; for it is only the
previously existing air which gets expanded throughout every part of the
loaf, swells out its volume, and gives it the _piled_ and vesicular
texture. Thus the well-baked loaf is composed of an infinite number of
cellules filled with carbonic acid gas, and apparently lined with a
glutinous membrane of a silky softness. It is this which gives the
light, elastic porous constitution to bread.
After suffering the fermentative process to exhaust itself in a mass of
dough, and the dough to be brought into that state in which the addition
of neither yeast, nor starch, nor gluten will produce any effect in
restoring that action, if we mix in 4 per cent. of saccharine matter, of
any kind, with a little yeast, the process of fermentation will
immediately re-commence, and pursue a course as active and lengthened as
at first, and cease about the same period.[11]
[11] Dr. Colquhoun, in Annals of Philosophy for 1826, vol. xii. p.
171.
This experiment, taken in connection with the facts formerly stated,
proves that what was called panary fermentation, is nothing but the
ancient and well-known process of the vinous fermentation of sugar,
which generates alcohol. There seems to be but one objection to the
adoption of this theory. After the loaf is baked, there is found in its
composition nearly as much saccharine matter as existed in the flour
before fermentation. M. Vogel states that in the baked bread there
remains 3·6 parts of sugar, out of the 5 parts which it originally
contained. Thus, in 100 parts of loaf bread prepared with wheaten flour,
distilled water, and yeast without the admixture of any common salt, he
found the following ingredients:--
Sugar 8·6
Torrefied or gummy starch 18·0
Starch 53·5
Gluten, combined with a little starch, 20·75
Exclusive of carbonic acid, muriate of lime, phosphate of lime, &c.
It must be borne in mind that in every loaf the process of fermentation
has been prematurely checked by the baker’s oven, and therefore the
saccharine constituent can never be wholly decomposed. It seems certain,
also, that by the action of gluten upon the starch in the early stage of
the firing, a quantity of sugar will be formed by the saccharine
fermentation; which we have explained in treating of BEER.
Several masses of dough were prepared by Dr. Colquhoun in which pure
wheat starch was mixed with common flour, in various proportions. In
some of the lumps this starch had been gelatinized, with the _minimum_
of hot water, before it was added to the flour. After introducing the
usual dose of salt, the dough was thoroughly kneaded, set apart for the
proper period, allowed to ferment in the accustomed way, and then baked
in the oven. In outward appearance, increase of bulk, and vesicular
texture, none of them differed materially from a common loaf, baked
along with them for the sake of comparison; except that when the starch
considerably exceeded the proportion of flour in the lump, the loaf,
though whiter, had not risen so well, being somewhat less vesicular.
But, on tasting the bread of each loaf, those which contained most
gelatinized starch were unexpectedly found to be the sweetest. The other
loaves, into which smaller quantities of the gelatinized starch had been
introduced, or only some dry starch, had no sweetish taste whatever to
distinguish them from ordinary bread. These facts seem to establish the
conclusion, that the presence of gelatinous starch in bread put into the
oven, is a means of forming a certain portion of saccharine matter
within the loaf, during the baking process. Now it is more than probable
that gelatinized starch does exist, more or less, in all loaves which
have been fermented by our usual methods, and hence a certain quantity
of sugar will necessarily be generated at its expense, by the action of
heat. Thus the difficulty started by M. Vogel is sufficiently solved;
and there remains no doubt that, in the saccharine principle of flour,
the fermentation has its origin and end, while dough is under
fermentation.
The source of the sourness which supervenes in bread, under careless or
unskilful hands, had been formerly ascribed to each of all the
constituents of flour; to its gluten, its starch, and its sugar; but
erroneously, as we now see: for it is merely the result of the second
fermentation which always succeeds the vinous, when pushed improperly
too far. It has been universally taken for granted by authors, that the
acid thus generated in dough is the acetic. But there appear good
grounds to believe that it is frequently a less volatile acid, probably
the lactic, particularly when the process has been tardy, from the
imperfection of the yeast or the bad quality of the flour. The
experiments of Vogel, Braconnot, and others, prove that the latter acid
is generated very readily, and in considerable quantity during the
spontaneous decomposition of a great many vegetable substances, when in
a state of humidity. The presence of lactic acid would account for the
curious fact, that the acidity of unbaked dough is much more perceptible
to the taste than to the smell; while the sourness of the same piece of
bread, after coming out of the oven, is, on the contrary, much more
obvious to the olfactory organs than to the palate. But this is exactly
what ought to happen, if the lactic acid contributes, in conjunction
with the acetic, to produce the acescence of the dough. At the ordinary
temperature of a bakehouse, the former acid, though very perceptible in
the mouth, is not distinguishable by the nostrils; but as it is easily
decomposed by heat, no sooner is it exposed to the high temperature of
the oven, than it is resolved, in a great measure, into acetic acid[12],
and thus becomes more manifest to the sense of smell, and less to that
of taste. This theory seems to explain satisfactorily all the phenomena
accompanying the progress of fermentation in baker’s dough, and also
some of its results in the process of baking which do not easily admit
of any other solution.
[12] Berzelius.
There are extremely simple and effectual methods for enabling the baker
to adopt measures either to prevent or correct the evil of acescence,
and these are to neutralize the acid by the due exhibition of an alkali,
such as soda; or an alkaline earth, such as magnesia or chalk. And it
affords a striking proof of how much the artisan has been accustomed to
plod, uninquiring and uninformed, over the same ground, that a remedy so
safe and so economical, should remain at this day unthought of and
unemployed by most of the manufacturers of bread in the United Kingdom.
The introduction of a small portion of carbonate of soda will rectify
any occasional error in the result of the so called panary fermentation,
and will, in fact, restore the dough to its pristine sweetness. The
quantity of acetate of soda, which will be thus present in the bread,
will be altogether inconsiderable; and as it has no disagreeable taste,
and is merely aperient to the bowels in a very mild degree, it can form
no objection in the eye of the public police. The restoration of dough
thus tainted with acid, and its conversion into pleasant and wholesome
bread, has been sufficiently verified by experiment. But, according to
Mr. Edmund Davy, carbonate of magnesia may be used with still greater
advantage, as during the slow action of the acid upon it, the carbonic
acid evolved serves to open up and lighten bread which would otherwise
be dense and doughy from the indifferent quality of the flour. Here,
however, the dangerous temptation lies with a sordid baker to use cheap
or damaged flour, and to rectify the bread made of it by chemical
agents, innocent in themselves, but injurious as masks of a bad raw
material. When sour yeast must be used, as sometimes happens with the
country bakers, or in private houses at a distance from beer breweries,
there can be no harm, but, on the contrary, much propriety, in
correcting its acidity, by the addition of as much carbonate of soda to
it as will effect its neutralization, but nothing more. When sour yeast
has been thus corrected, it has been found, in practice, to possess its
fermentative power unimpaired, and to be equally efficacious, with fresh
formed yeast, in making good palatable loaves.
We have seen that, in baking, about one fourth of the starch is
converted into a matter possessing the properties of _British gum_ (see
STARCH), and also that the gluten, though not decomposed, has its
particles disunited, and is not so tough and adhesive as it is in the
flour. This principle is also, as we have said, useful in cementing all
the particles of the dough into a tenacious mass, capable of confining
the elastic fluid generated by the vinous fermentation of the sugar.
Starch is the main constituent, the basis of nourishment in bread, as
well as in all farinaceous articles of food. The albumen also of the
wheat being coagulated by the heat of the oven, contributes to the
setting of the bread into a consistent elastic body.
In the mills in the neighbourhood of London, no less than seven distinct
sorts of flour are ground out of one quantity of wheat. These are for
one quarter--
Fine flour 5 bushels 3 pecks.
Seconds 0 2
Fine middlings 0 1
Coarse middlings 0 0·5
Bran 3 0
Twenty-penny 3 0
Pollard 2
--- ---
14 2·5
So that we have nearly a double bulk of flour, or 14 bushels and 2-1/2
pecks from 8 bushels of wheat. In the sifting of the flour through the
bolter, there is a fine white angular meal obtained called sharps, which
forms the central part of the grain. It is consumed partly by the fine
biscuit bakers. The bakers of this country were formerly bound by law to
bake three kinds of bread, the _wheaten_, _standard wheaten_, and the
_household_; marked respectively with a W, S W, and H, and if they
omitted to make these marks on their bread they were liable to a
penalty. The size of the loaves were usually peck, half-peck, quartern,
and half-quartern; the weights of which, within 48 hours of their being
baked, should have been respectively 17 lbs. 6 oz.; 8 lbs. 11 oz.; 4
lbs. 5 oz. 8 dr.; and 4 lbs. 2 oz. 14 dr. In general they weigh about
one-seventh more before they enter the oven, or they lose one-seventh of
their weight in baking. The French bread loses fully one-sixth in the
oven, owing chiefly to its more oblong thin shape, as compared to the
cubical shape of the English bread. But this loss of weight is very
variable, being dependent upon the quality of the wheaten flour, and the
circumstances of baking. The present law in England defines the quartern
loaf at 4 lbs., and subjects the baker to a penalty if the bread be one
ounce lighter than the standard. Hence it leaves the baker in
self-defence, to leave it in rather a damp and doughy state. But there
is much light bread sold in London. I have met with quartern loaves of 3
lbs. 10 ozs. A sack of flour weighing 280 lbs. was presumed by the
framers of our former parliamentary acts, for the assize of bread, to be
capable of being baked into 80 loaves. If this proportion had been
correct, one-fifth part of our quartern loaf must consist of water and
salt, and four-fifths of flour. But in general, of good wheaten flour,
three parts will take up one part of water; so that the sack of flour
should have turned out, and actually did turn out, more than 80 loaves.
At present with 4 lb. bread it may well yield 92 loaves.
The following statement of the system of baking at Paris, I received in
1835 from a very competent judge of the business.
1,000 kilogrammes of wheat = 5 quarters English, cost 200 fr., and yield
800 kilos of flour of the best white quality, equivalent to 5-1/10 sacks
French. Hence the sack of flour costs 40 francs at the mill, and
including the carriage to Paris, it costs 45 or 46 francs.
The profit of the flour dealer is about 3-1/2 francs, and the sale price
becomes from 43 to 50 francs.
_Bread manufactured from the above._
_£_ _s._ _d._ _£_ _s._ _d._
One day’s work of an ordinary baker, 6 0 0
who makes fourbatches in a day,
consists of 3 sacks at 50 francs, or
2_l._ sterling each
Salt 2-3/4 lbs. at 2_d._ per lb. 0 0 5-1/2
Yeast or leaven 3 lbs. at 5_d._ 0 1 3
---------------
Total cost of materials 6 1 8-1/2
_Expenses of Baking._
Three workmen at different rates of 0 12 0
wages, 15 francs
Fire-wood 0, as the charcoal pro-
duced pays for it
General expenses, such as rent, 0 12 0
taxes, interest of capital, &c.
----------
1 4 0 = 1 4 0
--------------
7 5 8-1/2
For this sum 315 loaves are made, 7 17 6
being 105 for every sack of flour
weighing 156·66 kilos, or 344-2/3
lbs. avoird. One loaf contains
therefore 344·65/105 = 3·282 lbs.,
and as 100 lbs. of flour in Parisian
baking are reckoned to produce 127
lbs. of bread, each loaf will weigh
4·168 lbs., avoird., and will cost
7_l._ 5_s._ 8-1/2_d._ divided by 315
= 5-1/2_d._ very nearly. The value
of 315 loaves at the sale price of
6_d._ will be
--------------
Upon this day’s work the clear 0 11 9-1/2
profit is therefore
A new baking establishment has been recently formed at the Royal
Clarence Victualling Establishment at Weevil, near Portsmouth, upon a
scale of magnitude nearly sufficient to supply the whole royal navy with
biscuits, and that of a very superior description. The following account
of it is taken from the United Service Journal. “It having been
discovered that the flour supplied to government by contract, had in
many instances been most shamefully adulterated, the corn is ground at
mills comprised within the establishment, by which means the
introduction of improper ingredients is prevented, and precisely the
proportion of bran which is requisite in the composition of good
sea-biscuit is retained, and no more. The flour-mill is furnished with
10 pairs of stones, by which 40 bushels of flour may be ground and
dressed ready for baking, in an hour. The baking establishment consists
of 9 ovens, each 13 feet long by 11 feet wide, and 17-1/2 inches in
height. These are each heated by separate furnaces, so constructed that
a blast of hot air and fire sweeps through them, and gives to the
interior the requisite dose of heat in an incredible short space of
time. The first operation in making the biscuits, consists in mixing the
flour or rather meal and water; 13 gallons of water are first introduced
into a trough, and then a sack of the meal, weighing 280 lbs. When the
whole has been poured in by a channel communicating with an upper room,
a bell rings, and the trough is closed. An apparatus consisting of two
sets of what are called knives, each set ten in number, are then made to
revolve amongst the flour and water by means of machinery. This mixing
operation lasts one minute and a half, during which time the double
set of knives or stirrers makes twenty-six revolutions. The next
process is to cast the lumps of dough under what are called the
breaking-rollers,--huge cylinders of iron, weighing 14 cwt. each, and
moved horizontally by the machinery along stout tables. The dough is
thus formed into large rude masses 6 feet long by 3 feet broad, and
several inches thick. At this stage of the business, the kneading is
still very imperfect, and traces of dry flour may still be detected.
These great masses of dough are now drawn out, and cut into a number of
smaller masses about a foot and a half long by a foot wide, and again
thrust under the rollers, which is repeated until the mixture is so
complete that not the slightest trace of any inequality is discoverable
in any part of the mass. It should have been stated that two workmen
stand one at each side of the rollers, and as the dough is flattened
out, they fold it up, or double one part upon another, so that the
roller at its next passage squeezes these parts together, and forces
them to mix. The dough is next cut into small portions, and being placed
upon large flat boards, is, by the agency of machinery, conveyed from
the centre to the extremity of the baking-room. Here it is received by a
workman, who places it under what is called the sheet roller, but which,
for size, colour, and thickness, more nearly resembles a blanket. The
kneading is thus complete, and the dough only requires to be cut into
biscuits before it is committed to the oven. The cutting is effected by
what is called the cutting-plate, consisting of a net-work of 52
sharp-edged hexagonal frames, each as large as a biscuit. This frame is
moved slowly up and down by machinery, and the workman, watching his
opportunity, slides under it the above-described blanket of dough, which
is about the size of a leaf of a dining table; and the cutting-frame in
its descent indents the sheet, but does not actually cut it through, but
leaves sufficient substance to enable the workman at the mouth of the
oven to jerk the whole mass of biscuits unbroken into it. The dough is
prevented sticking to the cutting-frame by the following ingenious
device: between each of the cutter-frames is a small flat open frame,
movable up and down, and loaded with an iron ball, weighing several
ounces. When the great frame comes down upon the dough, and cuts out 52
biscuits, each of these minor frames yields to the pressure, and is
raised up; but as soon as the great frame rises, the weight of the balls
acting upon the little frames, thrusts the whole blanket off, and allows
the workmen to pull it out. One quarter of an hour is sufficient to bake
the biscuit, which is afterwards placed for three days in a drying room,
heated to 85° or 90°, which completes the process.” The following
statement of the performance of the machinery is taken from actual
experiment; in 116 days, during 68 of which, the work was continued for
only 7-1/2 hours; and during 48, for only 5-3/4 hours each day, in all
769 working hours, equal to 77 days of 10 hours each; the following
quantity of biscuit was baked in the 9 ovens; viz., 12,307 cwt. =
1,378,400 lbs. The wages of the men employed in baking this quantity
amounted to 273_l._ 10_s._ 9-1/2_d._; if it had been made by hand, the
wages would have been 933_l._ 9_s._ 10_d._; saving in the wages of
labour, 659_l._ 7_s._ 0-1/2_d._ In this, is not included any part of the
interest of the sum laid out upon the machine, or expended in keeping it
in order. But in a very few years at such an immense rate of saving, the
cost of the engine and other machinery will be repaid. This admirable
apparatus is the invention of T. T. Grant, Esq. storekeeper of the Royal
Clarence Victualling Establishment, who, we believe, has been properly
rewarded, by a grant of 2,000_l._ from government.
The labour of incorporating the ingredients of bread, viz. flour, water
and salt, or kneading dough, is so great as to have led to the
contrivance of various mechanical modes of producing the same effect.
One of the most ingenious is that for which a patent was obtained in
August, 1830, by Mr. Edwin Clayton. It consists of a rotatory kneading
trough, or rather barrel, mounted in bearings with a hollow axle, and of
an interior frame of cast iron made to revolve by a solid axle which
passes through the hollow one; in the frame there are cutters diagonally
placed for kneading the dough. The revolving frame and its barrel are
made to turn in contrary directions, so as greatly to save time and
equalize the operation. This double action represents kneading by the
two hands, in which the dough is inverted from time to time, torn
asunder, and reunited in every different form. The mechanism will be
readily understood from the following description.
[Illustration: 169]
_Fig._ 169. exhibits a front elevation of a rotatory kneading trough,
constructed according to improvements specified by the patentee, the
barrel being shown in section: _a_ is the barrel, into which the several
ingredients, consisting of flour, water, and yeast, are put, which
barrel is mounted in the frame-work _b_, with hollow axles _c_ and _d_,
which hollow axles turn in suitable bearings at _e_; _f_ is the
revolving frame which is mounted in the interior of the barrel _a_, by
axles _g_ and _h_. The ends of this revolving frame are fastened, or
braced together by means of the oblique cutters or braces _i_, which act
upon the dough when the machine is put in motion, and thus cause the
operation of kneading.
Either the barrel may be made to revolve without the rotatory frame, or
the rotatory frame without the barrel, or both may be made to revolve
together, but in opposite ways. These several motions may be obtained by
means of the geer-work, shown at _k_, _l_, and _m_, as will be presently
described.
If it be desired to have the revolving motion of the barrel and rotatory
frame together, but in contrary directions, that motion may be obtained
by fastening the hollow axle of the wheel _m_, by means of a screw _n_,
to the axle _h_, of the rotatory frame _f_, tight, so as they will
revolve together, the other wheels _k_ and _l_ being used for the
purpose of reversing the motion of the barrel. It will then be found
that by turning the handle _o_, the two motions will be obtained.
If it be desired to put the rotatory frame _f_, only into motion, that
action will be obtained by loosening the screw _n_, upon the axle of the
wheel _m_, when it will be found that the axle _h_, will be made to
revolve freely by means of the winch _o_, without giving motion to the
wheels _k_, _l_, and _m_, and thus the barrel will remain stationary. If
the rotatory action of the barrel be wanted, it will be obtained by
turning the handle _p_, at the reverse end of the machine, which,
although it puts the geer at the opposite end of the barrel into motion,
yet as the hollow axle of the wheel _m_ is not fastened to the axle _h_,
by the screw _n_, these wheels will revolve without carrying round the
frame _f_.
M. Kuhlmann, Professor of Chemistry at Lille, having been called upon
several times by the courts of justice to examine by chemical processes
bread suspected of containing substances injurious to health, collected
some interesting facts upon the subject, which were published under the
direction of the central council of salubrity of the department _du
Nord_.
For some time public attention had been drawn to an odious fraud
committed by a great many bakers in the north of France and in
Belgium,--the introduction of a certain quantity of sulphate of copper
into their bread. When the flour was made from bad grain this
adulteration was very generally practised, as was proved by many
convictions and confessions of the guilty persons. When the dough does
not rise well in the fermentation (_le pain pousse plat_), this
inconvenience was found to be obviated by the addition of blue vitriol,
which was supposed also to cause the flour to retain more water. The
quantity of blue water added is extremely small, and it is never done in
presence of strangers, because it is reckoned a valuable secret. It
occasions no economy of yeast, but rather the reverse. In a litre (about
a quart) of water, an ounce of sulphate of copper is dissolved; and of
this solution a wine-glass full is mixed with the water necessary for 50
quartern or 4 pound loaves.
M. Kuhlmann justly observes that there can be no safety whatever to the
public when such a practice is permitted, because ignorance and avarice
are always apt to increase the quantity of the poisonous water. In
analyses made by him and his colleagues, portions of bread were several
times found so impregnated with the above salt that they had acquired a
blue colour, and presented occasionally even small crystals of the
sulphate. By acting on the poisoned bread with distilled water and
testing the water with ferro-cyanate (prussiate) of potash, the reddish
brown precipitate or tint characteristic of copper will appear even with
small quantities. Should the noxious impregnation be still more minute,
the bread should be treated with a very dilute nitric-acid, either
directly, or after incineration in a platinum capsule, and the solution,
when concentrated by evaporation, should be tested by the ferro-cyanate
of potash. In this way, a one seventy thousandth part of sulphate of
copper may be detected.
M. Kuhlmann deduces, from a series of experiments on baking with various
small quantities of sulphate of copper, that this salt exercises an
extremely energetic action upon the fermentation and rising of the
dough, even when not above one seventy thousandth part of the weight of
the bread is employed; or one grain of sulphate for ten pounds of bread.
The proportion of the salt which makes the bread rise best is one twenty
thousandth, or one grain in three pounds of bread. If much more of the
sulphate be added, the bread becomes moist, less white, and acquires a
peculiar disagreeable smell like that of leaven. The increase of weight
by increased moisture may amount to one sixteenth without the bread
appearing softer, in consequence of the solidifying quality of the
copper; for the acid does not seem to have any influence; as neither
sulphate of soda, sulphate of iron, nor sulphuric acid have any
analogous power. Alum operates like blue vitriol on bread, but larger
quantities of it are required. It _keeps water_, and _raises well_, to
use the bakers’ terms.
When alum is present in bread it may be detected by treating the bread
with distilled water, filtering the water first through calico, and next
through filtering paper, till it becomes clear; then dividing it into
two portions, and into the one pouring a few drops of nitrate or muriate
of barytes, and into the other a few drops of water of ammonia. In the
former a heavy white precipitate indicating sulphuric acid will appear,
and in the latter a light precipitate of alumina, redissoluble by a few
drops of solution of caustic potash.
When chalk or Paris plaster is used to sophisticate flour, they may be
best detected by incinerating the bread made of it, and examining the
ashes with nitric acid which will dissolve the chalk with effervescence,
and the Paris plaster without. In both cases the calcareous matter may
be demonstrated in the solution, by oxalic acid, or better by oxalate of
ammonia.
In baking puff-paste the dough is first kneaded along with a certain
quantity of butter, then rolled out into a thin layer, which is coated
over with butter, and folded face-wise many times together, the upper
and under surfaces being made to correspond. This stratified mass is
again rolled out into a thin layer, its surface is besmeared with
butter, and then it is folded face-wise as before. When this process is
repeated ten or a dozen times, the dough will consist of many hundred
parallel laminæ, with butter interposed between each pair of plates.
When a moderately thick mass of this is put into the oven, the elastic
vapour disengaged from the water and the butter, diffuses itself between
each of the thin laminæ, and causes them to swell into what is properly
called puff-paste, being an assemblage of thin membranes, each dense in
itself, but more or less distinct from the other, and therefore forming
apparently but not really light bread.
One of the most curious branches of the baker’s craft is the manufacture
of gingerbread, which contains such a proportion of molasses, that it
cannot be fermented by means of yeast. Its ingredients are flour,
molasses or treacle, butter, common potashes, and alum. After the butter
is melted, and the potashes and alum are dissolved in a little hot
water, these three ingredients, along with the treacle, are poured among
the flour, which is to form the body of the bread. The whole is then
incorporated by mixture and kneading into a stiff dough. Of these five
constituents the alum is thought to be the least essential, although it
makes the bread lighter and crisper, and renders the process more rapid;
for gingerbread dough requires to stand over several days, sometimes 8
or 10, before it acquires that state of porosity which qualifies it for
the oven. The action of the treacle and alum on the potashes in evolving
carbonic acid, seems to be the gasefying principle of gingerbread; for
if the carbonate of potash is withheld from the mixture, the bread, when
baked, resembles in hardness a piece of wood.
Treacle is always acidulous. Carbonate of magnesia and soda may be used
as substitutes for the potashes. Dr. Colquhoun has found that carbonate
of magnesia and tartaric acid may replace the potashes and the alum with
great advantage, affording a gingerbread fully more agreeable to the
taste, and much more wholesome than the common kind, which contains a
notable quantity of potashes. His proportions are one pound of flour, a
quarter of an ounce of carbonate of magnesia, and one eighth of an ounce
of tartaric acid; in addition to the treacle, butter, and aromatics as
at present used. The acid and alkaline earth must be well diffused
through the whole dough. The magnesia should, in fact, be first of all
mixed with the flour. Pour the melted butter, the treacle, and the acid
dissolved in a little water all at once among the flour, and knead into
a consistent dough, which being set aside for half an hour or an hour
will be ready for the oven, and should never be kept unbaked more than 2
or 3 hours. The following more complete recipe is given by Dr.
Colquhoun, for making thin gingerbread cakes:--
Flour 1 lb.
Treacle 0-1/2
Raw sugar 0-1/4
Butter 2 oz.
Carbon. magnesia 0-1/4
Tartaric acid 0-1/8
Ginger 0-1/8
Cinnamon 0-1/8
Nutmeg 1
This compound has rather more butter than common thin gingerbread.
I shall here insert a passage from my Dictionary of Chemistry as
published in 1821; as it may prove interesting to many of my present
readers.
“Under _Process of Baking_, in the Supplement to the Encyclopedia
Britannica, we have the following statement:--‘An ounce of alum is then
dissolved over the fire in a tin pot, and the solution poured into a
large tub, called by the bakers the seasoning-tub. Four pounds and a
half of salt are likewise put into the tub, and a pailful of hot
water.’--_Foot note on this passage._--‘In London, where the goodness of
bread is estimated entirely by its whiteness, it is usual with those
bakers who employ flour of an inferior quality, to add as much alum as
common salt to the dough; or, in other words, the quantity of salt added
is diminished one half, and the deficiency supplied by an equal weight
of alum. This improves the look of the bread very much, rendering it
much whiter and firmer.’”
In a passage which we shall presently quote, our author represents the
bakers of London in a conspiracy to supply the citizens with bad bread.
We may hence infer that the full allowance he assigns of 2-1/4 pounds of
alum for every 2-1/4 pounds of salt, will be adopted in converting the
sack of flour into loaves. But as a sack of flour weighs 280 pounds, and
furnishes on an average 80 quartern loaves, we have 2-1/4 pounds divided
by 80, or (15750 grains/80) = 197 grains, for the quantity present, by
this writer, in a London quartern loaf. Yet in the very same page (39th
of vol. ii.) we have the following passage: “Alum is not added by all
bakers. The writer of this article has been assured by several bakers of
respectability, both in Edinburgh and Glasgow, on whose testimony he
relies, and who made excellent bread, that they never employed any alum.
The reason for adding it given by the London bakers is, that it renders
the bread whiter, and enables them to separate readily the loaves from
each other. This addition has been alleged by medical men, and is
considered by the community at large, as injurious to the health, by
occasioning constipation. But if we consider the small quantity of this
salt added by the baker, not quite 5-1/2 grains to a quartern loaf, we
will not readily admit these allegations. Suppose an individual to eat
the seventh part of a quartern loaf a day, he would only swallow
eight-tenths of a grain of alum, or, in reality, not quite so much as
half a grain; for one half of this salt consists of water. It seems
absurd to suppose that half a grain of alum, swallowed at different
times during the course of a day, should occasion constipation.” Is it
not more absurd to state 2-1/4 pounds or 36 ounces, as the alum
adulteration of a sack of flour by the London bakers, and within a few
periods to reduce the adulteration to one ounce?
That this voluntary abstraction of 35/36 of the alum, and substitution
of superior and more expensive flour is not expected by him from the
London bakers, is sufficiently evident from the following story. It
would appear that one of his friends had invented a new yeast for
fermenting dough, by mixing a quart of beer barm with a paste made of
ten pounds of flour and two gallons of boiling water, and keeping this
mixture warm for six or eight hours.
“Yeast made in this way,” says he, “answers the purposes of the baker
much better than brewers’ yeast, because it is clearer, and free from
the hop mixture which sometimes injures the yeast of the brewer. Some
years ago the bakers of London, sensible of the superiority of this
artificial yeast, invited a company of manufacturers from Glasgow to
establish a manufactory of it in London, and promised to use no other.
About 5,000_l._ accordingly was laid out on buildings and materials, and
the manufactory was begun on a considerable scale. The ale-brewers,
finding their yeast, for which they had drawn a good price, lie heavy on
their hands, invited _all_ the journeymen bakers to their cellars, gave
them their full of ale, and promised to regale them in that manner every
day, provided they would force their masters to take all their yeast
from the ale-brewers. The journeymen accordingly declared, in a body,
that they would work no more for their masters unless they gave up
taking any more yeast from the manufactory. The masters were obliged to
comply; the new manufactory was stopped, and the inhabitants of London
were obliged to continue to eat worse bread, because it was the interest
of the ale-brewers to sell the yeast. Such is the influence of
journeymen bakers in the metropolis of England!”
This doleful diatribe seems rather extravagant; for surely beer yeast
can derive nothing noxious to a porter drinking people, from a slight
impregnation of hops; while it must form probably a more energetic
ferment than the fermented paste of the new company, which at any rate
could be prepared in six or eight hours by any baker who found it to
answer his purpose of making a pleasant-eating bread. But it is a very
serious thing for a lady or gentleman of sedentary habits, or infirm
constitution, to have their digestive process daily vitiated by damaged
flour, whitened with 197 grains of alum per quartern loaf. Acidity of
stomach, indigestion, flatulence, headaches, palpitation, costiveness,
and urinary calculi may be the probable consequences of the habitual
introduction of so much acidulous and acescent matter.
I have made many experiments upon bread, and have found the proportion
of alum very variable. Its quantity seems to be proportional to the
badness of the flour; and hence when the best flour is used, no alum
need be introduced. That alum is not necessary for giving bread its
utmost beauty, sponginess, and agreeableness of taste, is undoubted;
since the bread baked at a very extensive establishment in Glasgow, in
which about 20 tons of flour were regularly converted into loaves in the
course of a week, united every quality of appearance with an absolute
freedom from that acido-astringent drug. Six pounds of salt were used
for every sack of flour; which, from its good quality, generally
afforded 83 or 84 quartern loaves of the legal weight of four pounds
five ounces and a half each. The loaves lost nine ounces in the oven.
Every baker ought to be able to analyse his flour. He may proceed as
follows:--A ductile paste is to be made with a pound of the flour and a
sufficient quantity of water, and left at rest for an hour; then having
tied across a bowl a piece of silken sieve-stuff, a little below the
surface of the water in the bowl, the paste is to be laid upon the sieve
on a level with the water, and kneaded tenderly with the hand, so as
merely to wash the starchy particles out of it. This portion of the
flour gets immediately diffused through the water, some of the other
constituents dissolve, and the gluten alone remains upon the filter. The
water must be several times renewed till it ceases to become milky. The
last washings of the gluten are made out of the sieve.
The whole of the turbid washings are to be put into a tall conical glass
or stoneware vessel, and allowed to remain at rest, in a cool place,
till they deposit the starch. The clear supernatant liquor is then
decanted off. The deposit consists of starch, with a little gluten. It
must be washed till the water settles over it quite clear, and then it
is to be dried.
The filtered waters being evaporated, at a boiling heat, discover flocks
floating through them, which have been supposed by some to be albumen,
and by others gluten. At last, phosphate of lime precipitates. When the
residuum has assumed a syrupy consistence in the cold, it is to be mixed
with alcohol, in order to dissolve out its sugar. Cold water being added
to what remains, effects a solution of the mucilage, and leaves the
insoluble azotized matter with the phosphate of lime.
By this mode of analysis a minute portion of resin may remain in the
gluten and in the washing water; the gluten retains also a small
proportion of a fixed oil, and a volatile principle, which may be
removed by alcohol. If we wish to procure the resin alone, we must first
of all treat the flour, well dried, with alcohol.
When corn flour, poor in gluten, is to be analyzed, the dough must be
inclosed in a linen bag, kneaded with water, and washed in that state.
In analyzing barley-meal by the above process, _hordeine_, mixed with
common starch, is obtained: they may be separated by boiling water,
which dissolves the starch, and leaves the hordeine under the aspect of
saw-dust.
[Illustration: 170 171]
_Fig._ 171. is the plan of a London baker’s oven, fired with coal fuel.
_Fig._ 170. is the longitudinal section.
_a_, the body of the oven; _b_, the door; _c_, the fire-grate and
furnace; _d_, the smoke flue; _e_, the flue above the door, to carry off
the steam and hot air, when taking out the bread; _f_, recess below the
door, for receiving the dust; _g_, damper plate to shut off the steam
flue; _h_, damper plate to shut off smoke flue, after the oven has come
to its proper heat; _i_, a small iron pan over the fire-place _c_, for
heating water; _k_, ash-pit below the furnace.
[Illustration: 172]
_Fig._ 172. is the front view; the same letters refer to the same
objects in all the figures.
The flame and burnt air of the fire at _c_, sweep along the bottom of
the oven by the right hand side, are reflected from the back to the left
hand side, and thence escape by the flue _d_; (see plan _fig._ 171).
Whenever the oven has acquired the proper degree of heat, the fire is
withdrawn, the flues are closed by the damper plates, and the lumps of
fermented dough are introduced.
BRECCIA, an Italian term, used by mineralogists and architects to
designate such compound stony masses, natural or artificial, as consist
of hard rocky fragments of considerable size, united by a common cement.
When these masses are formed of small rounded pebbles, the conglomerate
is called a pudding-stone, from a fancied resemblance to plum pudding.
_Concrete_, now so much used for the foundations of large buildings, is
a factitious breccia, or pudding-stone. See CONCRETE.
BREWING. (_Brasser_, Fr.; _Brauen_, Germ.) The art of making beer, which
see.
BRICK. (_Brique_, Fr.; _Backsteine_, _ziegelsteine_, Germ.) A solid,
commonly rectangular, composed of clay, hardened by heat, and intended
for building purposes. The natural mixture of clay and sand, called
_loam_, as well as marl, which consists of lime and clay, with little or
no sand, constitutes also a good material for making bricks. The poorer
the marl is in lime, the worse adapted it is for agricultural purposes,
and the better for the brick manufacturer, being less liable to fuse in
his kiln. When a natural compound of silica and clay can be got nearly
free from lime and magnesia, it forms a kind of bricks very refractory
in the furnace, hence termed _fire-bricks_. Such a material is the
slate-clay, _schieferthon_, of our coal measures, found abundantly, and
of excellent quality, at Stourbridge, and in the neighbourhood of
Newcastle and Glasgow. The London brickmakers add to the clay about one
third of coal ashes obtained from the kitchen dust-holes; so that when
the bricks are put into the kiln, the quantity of coaly matter attached
to their surface, serves to economise fuel, and makes them less apt to
shrink in the fire; though they are less compact, and probably less
durable, than the bricks made in the coal districts of England.
The general process of brick-making consists in digging up the clay in
autumn; exposing it, during the whole winter, to the frost, and the
action of the air, turning it repeatedly, and working it with the spade;
breaking down the clay lumps in spring, throwing them into shallow pits,
to be watered and soaked for several days. The next step is to temper
the clay, which is generally done by the treading of men or oxen. In the
neighbourhood of London, however, this process is performed in a
horse-mill. The kneading of the clay is, in fact, the most laborious but
indispensable part of the whole business; and that on which, in a great
measure, the quality of the bricks depends. All the stones, particularly
the ferruginous, calcareous, and pyritous kinds, should be removed, and
the clay worked into a homogeneous paste, with as little water as
possible.
The earth, being sufficiently kneaded, is brought to the bench of the
moulder, who works the clay into a mould made of wood or iron, and
strikes off the superfluous matter. The bricks are next delivered from
the mould, and ranged on the ground; and when they have acquired
sufficient firmness to bear handling, they are dressed with a knife, and
staked or built up in long dwarf walls, thatched over, and left to dry.
An able workman will make, by hand, 5,000 bricks in a day.
The different kinds of bricks made in England are principally _place
bricks_, _gray and red stocks_, _marl facing bricks_, and _cutting
bricks_. The place bricks and stocks are used in common walling. The
marls are made in the neighbourhood of London, and used in the outside
of buildings; they are very beautiful bricks, of a fine yellow colour,
hard, and well burnt, and, in every respect, superior to the stocks. The
finest kind of marl and red bricks, called cutting bricks, are used in
the arches over windows and doors, being rubbed to a centre, and gauged
to a height.
In France attempts were long ago made to substitute animals and machines
for the treading of men’s feet in the clay-kneading pit; but it was
found that their schemes could not replace, with advantage, human
labour, where it is so cheap, particularly for separating the stones and
heterogeneous matters from the loam. The more it is worked, the denser,
more uniform, and more durable, the bricks which are made of it. A good
French workman, in a day’s labour of 12 or 13 hours, it has been said,
is able to mould from 9,000 to 10,000 bricks, 9 inches long, 4-1/2
inches broad, and 2-1/4 thick; but he must have good assistants under
him. In many brickworks near Paris, screw-presses are now used for
consolidating the bricks and paving tiles in their moulds. M. Mollerat
employed the hydraulic press for the purpose of condensing pulverized
clay, which, after baking, formed beautiful bricks; but the process was
too tedious and costly. An ingenious contrivance for moulding bricks
mechanically, is said to be employed near Washington, in America. This
machine moulds 30,000 in a day’s work of 12 hours, with the help of one
horse, yoked to a gin wheel, and the bricks are so dry when discharged
from their moulds, as to be ready for immediate burning. The machine is
described, with figures, in the _Bulletin de la Société d’Encouragement_
for 1819, p. 361. _See further on, an account of our recent patents._
Bricks, in this country, are generally baked either in a clamp or in a
kiln. The latter is the preferable method, as less waste arises, less
fuel is consumed, and the bricks are sooner burnt. The kiln is usually
13 feet long, by 10-1/2 feet wide, and about 12 feet in height. The
walls are one foot two inches thick, carried up a little out of the
perpendicular, inclining towards each other at the top. The bricks are
placed on flat arches, having holes left in them resembling
lattice-work; the kiln is then covered with pieces of tiles and bricks,
and some wood put in, to dry them with a gentle fire. This continues two
or three days before they are ready for burning, which is known by the
smoke turning from a darkish colour to transparent. The mouth or mouths
of the kiln are now dammed up with a _shinlog_, which consists of pieces
of bricks piled one upon another, and closed with wet brick earth,
leaving above it just room sufficient to receive a faggot. The faggots
are made of furze, heath, brake, fern, &c., and the kiln is supplied
with these until its arches look white, and the fire appears at the top;
upon which the fire is slackened for an hour, and the kiln allowed
gradually to cool. This heating and cooling is repeated until the bricks
be thoroughly burnt, which is generally done in 48 hours. One of these
kilns will hold about 20,000 bricks.
Clamps are also in common use. They are made of the bricks themselves,
and generally of an oblong form. The foundation is laid with _place
brick_, or the driest of those just made, and then the bricks to be
burnt are built up, tier upon tier, as high as the clamp is meant to be,
with two or three inches of breeze or cinders strewed between each layer
of bricks, and the whole covered with a thick stratum of breeze. The
fireplace is perpendicular, about three feet high, and generally placed
at the west end; and the flues are formed by gathering or arching the
bricks over, so as to leave a space between each of nearly a brick wide.
The flues run straight through the clamp, and are filled with wood,
coals, and breeze, pressed closely together. If the bricks are to be
burnt off quickly, which may be done in 20 or 30 days, according as the
weather may suit, the flues should be only at about six feet distance;
but if there be no immediate hurry, they may be placed nine feet
asunder, and the clamp left to burn off slowly.
Floating bricks are a very ancient invention: they are so light as to
swim in water; and Pliny tells us, that they were made at Marseilles; at
Colento, in Spain; and at Pittane, in Asia. This invention, however, was
completely lost, until M. Fabbroni published a discovery of a method to
imitate the floating bricks of the ancients. According to Posidonius,
these bricks are made of a kind of argillaceous earth, which was
employed to clean silver plate. But as it could not be our tripoli,
which is too heavy to float in water, M. Fabbroni tried several
experiments with mineral agaric, guhr, lac-lunæ, and fossil meal, which
last was found to be the very substance of which he was in search. This
earth is abundant in Tuscany, and is found near Casteldelpiano, in the
territories of Sienna. According to the analysis of M. Fabbroni, it
consists of 55 parts of siliceous earth, 15 of magnesia, 14 of water, 12
of alumina, 3 of lime, and 1 of iron. It exhales an argillaceous odour,
and, when sprinkled with water, throws out a light whitish smoke. It is
infusible in the fire; and, though it loses about an eighth part of its
weight, its bulk is scarcely diminished. Bricks composed of this
substance, either baked or unbaked, float in water; and a twentieth part
of clay may be added to their composition without taking away their
property of swimming. These bricks resist water, unite perfectly with
lime, are subject to no alteration from heat or cold, and the baked
differ from the unbaked only in the sonorous quality which they have
acquired from the fire. Their strength is little inferior to that of
common bricks, but much greater in proportion to their weight; for M.
Fabbroni found, that a floating brick, measuring 7 inches in length,
4-1/2 in breadth, and one inch eight lines in thickness, weighed only
14-1/4 ounces; whereas a common brick weighed 5 pounds, 6-3/4 ounces.
The use of these bricks may be very important in the construction of
powder magazines and reverberatory furnaces, as they are such bad
conductors of heat, that one end may be made red hot while the other is
held in the hand. They may also be employed for buildings that require
to be light; such as cooking-places in ships, and floating batteries,
the parapets of which would be proof against red-hot bullets.
The following plan of a furnace or kiln for burning tiles has been found
very convenient:--
[Illustration: 173 174 175]
_Fig._ 173., front view, A A, B B, the solid walls of the furnace; _a a
a_, openings to the ash-pit, and the draught hole; _b b b_, openings for
the supply of fuel, furnished with a sheet-iron door. _Fig._ 174. Plan
of the ash-pits and air channels _c c c_. The principal branch of the
ash-pit D D D, is also the opening for taking out the tiles, after
removing the grate; E the smoke flue. _Fig._ 175. Plan of the kiln seen
from above. The grates H H H. The tiles to be fired are arranged upon
the spaces _f f f f_.
[Illustration: 176]
_Fig._ 176. is the plan and section of one of the grates upon a much
larger scale than in the preceding figures.
_Mechanical brick moulding._--Messrs. Lyne and Stainford obtained in
August, 1825, a patent for a machine for making a considerable number of
bricks at one operation. It consists, in the first place, of a
cylindrical pug-mill of the kind usually employed for comminuting clay
for bricks and tiles, furnished with rotatory knives, or cutters, for
breaking the lumps and mixing the clay with the other materials of which
bricks are commonly made. Secondly, of two movable moulds, in each of
which fifteen bricks are made at once; these moulds being made to travel
to and fro in the machine for the purpose of being alternately brought
under the pug-mill to be fitted with the clay, and then removed to
situations where plungers are enabled to act upon them. Thirdly, in a
contrivance by which the plungers are made to descend, for the purpose
of compressing the material and discharging it from the mould in the
form of bricks. Fourthly, in the method of constructing and working
trucks which carry the receiving boards, and conduct the bricks away as
they are formed.
[Illustration: 177]
_Fig._ 177. exhibits the general construction of the apparatus; both
ends of which being exactly similar, little more than half of the
machine is represented. _a_ is the cylindrical pug-mill, shown partly in
section, which is supplied with the clay and other materials from a
hopper above; _b b_, are the rotatory knives or cutters, which are
attached to the vertical shaft, and being placed obliquely, press the
clay down towards the bottom of the cylinder, in the act of breaking and
mixing it as the shaft revolves. The lower part of the cylinder is open;
and immediately under it the mould is placed in which the bricks are to
be formed. These moulds run to and fro upon ledges in the side frames of
the machine; one of the moulds only can be shown by dots in the figure,
the side rail intervening: they are situated at _c c_ and are formed of
bars of iron crossing each other, and encompassed with a frame. The
mould resembles an ordinary sash window in its form, being divided into
rectangular compartments (fifteen are proposed in each) of the
dimensions of the intended bricks, but sufficiently deep to allow the
material, after being considerably pressed in the mould, to leave it,
when discharged, of the usual thickness of a common brick.
The mould being open at top and bottom, the material is allowed to pass
into it, when situated exactly under the cylinder; and the lower side of
the mould, when so placed, is to be closed by a flat board _d_,
supported by the truck _e_, which is raised by a lever and roller
beneath, running upon a plane rail with inclined ends.
The central shaft _f_, is kept in continual rotatory motion by the
revolution of the upper horizontal wheel _g_, of which it is the axis;
and this wheel may be turned by a horse yoked to a radiating arm, or by
any other means. A part of the circumference of the wheel _g_, has teeth
which are intended at certain periods of its revolution to take into a
toothed pinion, fixed upon the top of a vertical shaft _h h_. At the
lower part of this vertical shaft, there is a pulley _i_, over which a
chain is passed that is connected to the two moulds _c_, and to the
frame in which the trucks are supported; by the rotation of the vertical
shaft, the pulley winds a chain, and draws the moulds and truck frames
along.
The clay and other material having been forced down from the cylinder
into the mould, the teeth of the horizontal wheel _g_ now come into geer
with the pinion upon _h_, and turn it and the shaft and pulley _i_, by
which the chain is wound, and the mould at the right hand of the machine
brought into the situation shown in the figure; a scraper or edge-bar
under the pug-mill having levelled the upper face of the clay in the
mould, and the board _d_, supported by the truck _e_, formed the flat
under side.
The mould being brought into this position, it is now necessary to
compress the materials, which is done by the descent of the plungers _k
k_. A friction-roller _l_, pendant from the under side of the horizontal
wheel as that wheel revolves, comes in contact with an inclined plane,
at the top of the shaft of the plungers; and, as the friction-roller
passes over this inclined plane, the plungers are made to descend into
the mould, and to compress the material; the resistance of the board
beneath causing the clay to be squeezed into a compact state. When this
has been effectually accomplished, the further descent of the plungers
brings a pin _m_, against the upper end of a quadrant catch-lever _n_,
and, by depressing this quadrant, causes the balance-lever upon which
the truck is now supported to rise at that end, and to allow the truck
with the board _d_ to descend, as shown by dots; the plungers at the
same time forcing out the bricks from the moulds, whereby they are
deposited upon the board _d_; when, by drawing the truck forward out of
the machine, the board with the bricks may be removed, and replaced by
another board. The truck may then be again introduced into the machine,
ready to receive the next parcel of bricks.
By the time that the discharge of the bricks from this mould has been
effected, the other mould under the pug cylinder has become filled with
the clay, when the teeth of the horizontal wheel coming round, take into
a pinion upon the top of a vertical shaft exactly similar to that at
_h_, but at the reverse end of the machine, and cause the moulds and the
frame supporting the trucks to be slidden to the left end of the
machine; the upper surface of the mould being scraped level in its
progress, in the way already described. This movement brings the
friction-wheel _o_, up the inclined plane, and thereby raises the truck
with the board to the under side of the mould, ready to receive another
supply of clay; and the mould at the left-hand side of the machine being
now in its proper situation under the plungers, the clay becomes
compressed, and the bricks discharged from the mould in the way
described in the former instance; when this truck being drawn out, the
bricks are removed to be dried and baked, and another board is placed in
the same situation. There are boxes _p_, upon each side of the pug
cylinder containing sand, at the lower parts of which small sliders are
to be opened (by contrivances not shown in the figure) as the mould
passes under them, for the purpose of scattering sand upon the clay in
the mould to prevent its adhering to the plungers. There is also a rack
and toothed sector, with a balance weight connected to the inclined
plane at the top of the plunger-rods, for the purpose of raising the
plunger after the friction-roller has passed over it. And there is a
spring acting against the back of the quadrant-catch for the purpose of
throwing it into its former situation, after the pin of the plunger has
risen.
One of the latest, and apparently most effective machines for
brick-making, is that patented by Mr. Edward Jones of Birmingham, in
August 1835. His improvements are described under four heads; the first
applies to a machine for moulding the earth into bricks in a circular
frame-plate horizontally, containing a series of moulds or rectangular
boxes, standing radially round the circumference of the circular frame,
into which boxes successively the clay is expressed from a stationary
hopper as the frame revolves, and after being so formed, the bricks are
successively pushed out of their boxes, each by a piston, acted upon by
an inclined plane below. The second head of the specification describes
a rectangular horizontal frame, having a series of moulding boxes placed
in a straight range, which are acted upon for pressing the clay by a
corresponding range of pistons fixed in a horizontal frame, worked up
and down by rods extending from a rotatory crank shaft, the moulding
boxes being allowed to rise for the purpose of enabling the pistons to
force out the bricks when moulded, and leave them upon the bed or board
below. The third head applies particularly to the making of tiles, for
the flooring of kilns in which malt or grain is to be dried. There is in
this contrivance a rectangular mould, with pointed pieces standing up
for the purpose of producing air-holes through the tiles as they are
moulded, which is done by pressing the clay into the moulds upon the
points, and scraping off the superfluous matter at top by hand. The
fourth or last head applies to moulding chimney pots in double moulds,
which take to pieces for the purpose of withdrawing the pot when the
edges of the slabs or sides are sufficiently brought into contact.
“The drawing which accompanies the specification very imperfectly
represents some parts of the apparatus, and the description is still
more defective; but as we are acquainted with the machinery, we will
endeavour to give it an intelligible form, and quote those parts of the
specification which point the particular features of novelty proposed to
be claimed by the patentee as his invention, under the several
heads.”[13]
[13] Mr. Newton, in his London Journal, February, 1837.
[Illustration: 178 179]
_Fig._ 178. represents, in elevation, the first-mentioned machine for
moulding bricks. The moulds are formed in the face of a circular plate
or wheel _a a_, a portion of the upper surface of which is represented
in the horizontal view, _fig._ 179. Any convenient number of these
moulds are set radially in the wheel, which is mounted upon a central
pivot, supported by the masonry _b b_. There is a rim of teeth round the
outer edge of the wheel _a a_, which take into a pinion _c_, on a shaft
connected to the first mover; and by these means the wheel _a_, with the
moulding boxes, is made to revolve horizontally, guided by arms with
anti-friction rollers, which run round a horizontal plate _a a_, fixed
upon the masonry.
A hopper _e_, filled with the brick earth shown with one of the moulding
boxes in section, is fixed above the face of the wheel in such a way,
that the earth may descend from the hopper into the several moulding
boxes as the wheel passes round under it; the earth being pressed into
the moulds, and its surface scraped off smooth by a conical roller _f_,
in the bottom of the hopper.
Through the bottom of each moulding box there is a hole for the passage
of a piston rod _g_, the upper end of which rod carries a piston with a
wooden pallet upon it, acting within the moulding box; and the lower end
of this rod has a small anti-friction roller which, as the wheel _a_
revolves, runs round upon the face of an oblique ring or inclined way _h
h_, fixed upon the masonry.
The clay is introduced into the moulding boxes from the hopper, fixed
over the lowest part of the inclined way _h_, and it will be perceived
that as the wheel revolves, the piston rods _g_, in passing up the
inclined way, will cause the pistons to force the new-moulded bricks,
with their pallet or board under them, severally up the mould, into the
situation shown at _i_, in _fig._ 178., from whence they are to be
removed by hand. Fresh pallets being then placed upon the several
pistons, they, with the moulds, will be ready for moulding fresh bricks,
when, by the rotation of the wheel _a_, they are severally brought under
the hopper, the pistons having sunk to the bottoms of their boxes, as
the piston rods passed down the other side of the inclined way _h_.
The patentee says, after having described the first head of his
invention, he would have it understood that the same may be varied
without departing from the main object of the invention; viz. that of
arranging a series of moulds when worked by means of an inclined track,
and in such manner that bricks, tiles, or other articles made of brick
earth, may be capable of being formed in a mould with pallets or boards
laid within the moulds, and constituting the bottoms thereof, the bricks
being removed from out of the moulds, with the pallets or boards under
them, as above described. “I do not, therefore, confine myself to the
precise arrangement of the machine here shown, though it is the best
with which I am acquainted for the purpose.”
[Illustration: 180 181]
The second head of the invention is another construction of apparatus
for moulding bricks, in this instance, in a rectangular frame. _Fig._
180. is a front elevation of the machine; _fig._ 181., a section of the
same taken transversely. _a a_ is the standard frame-work and bed on
which the bricks are to be moulded. Near the corners of this standard
frame-work, four vertical pillars _b b_ are erected, upon which pillars
the frame of the moulding boxes _c_, slides up and down, and also the
bar _d_, carrying the rods of the pistons _e e e_. These pistons are for
the purpose of compressing the clay in the moulding box, and therefore
must stand exactly over and correspond with the respective moulds in the
frame _c_ beneath.
The sliding frame _c_, constituting the sides and ends of the moulding
boxes, is supported at each end by an upright sliding rod _f_, which
rods pass through guides fixed to the sides of the standard frame _a a_,
and at the lower end of each there is a roller, bearing upon the levers
_g_, on each side of the machine, but seen only in _fig._ 181., which
levers, when depressed, allow the moulding boxes to descend, and rest
upon the bed or table of the machine _h h_.
In this position of the machine resting upon the bed or table, the
brick-earth is to be placed upon, and spread over, the top of the frame
_c_, by the hands of workmen, when the descent of the plunger or pistons
_e e e_, will cause the earth to be forced into the moulds, and the
bricks to be formed therein. To effect this, rotatory power is to be
applied to the toothed wheel _i_, fixed on the end of the main driving
crank shaft _k k_, which on revolving will, by means of the crank rods
_l l_, bring down the bar _a_, with the pistons or plungers _e e e_, and
compress the earth compactly into the moulds, and thereby form the
bricks.
When this has been done, the bricks are to be released from the moulds
by the moulding frame _c_ rising up from the bed, as shown in _fig._
180., the pistons still remaining depressed, and bearing upon the upper
surfaces of the bricks. The moulding frame is raised by means of cams
_m_, upon the crank shaft, which at this part of the operation are
brought under the levers _g_, for the purpose of raising the cams and
the sliding rods _f_, into the position shown in _fig._ 181.
The bricks having been thus formed and released from their moulds, they
are to be removed from the bed of the machine by pushing forward, on the
front side, fresh boards or pallets, which of course will drive the
bricks out upon the other side, whence they are to be removed by hand.
There is to be a small hole in the centre of each pallet, and also in
the bed, for the purpose of allowing any superfluous earth to be pressed
through the moulding boxes when the pistons descend. And in order to cut
off the projecting piece of clay which would be thus formed on the
bottom of the brick, a knife-edge is in some way connected to the bed of
the machine; and as the brick slides over it, the knife separates the
protuberant lump: but the particular construction of this part of the
apparatus is considered to be of little importance; and the manner of
effecting the object is not clearly stated in the specification.
The patentee proposes a variation in this construction, which he
describes in these words: “It will be evident that in place of having
the moulds to rise, they may, by suitable arrangements, be made to
descend below the bricks. In this case, in place of the boards,
stationary blocks to receive the pallets must be fixed on the bed of the
machine, and these blocks must be shaped in such a manner as to allow of
the moulds passing over them; and then it will be desirable to use the
first part of my improvements, that of having the pallets within the
moulds at the time of moulding the bricks; or in case of working with
exceedingly stiff brick-earth, the pallets may be dispensed with.” In
1835, 1,380,279,065 bricks paid duty in the United Kingdom; the revenue
from which was 405,580_l._ 6_s._ 3_d._
BRIMSTONE. (_Soufre_, Fr.; _Schwefel_, Germ.) Sulphur, which see.
BRITISH GUM. The trivial name given to starch, altered by a slight
calcination in an oven, whereby it assumes the appearance and acquires
the properties of gum, being soluble in cold water, and forming in that
state a paste well adapted to thicken the colours of the calico printer.
See STARCH.
BROMINE, one of the archæal elements, which being developed from its
combinations at the positive pole of the voltaic circuit, has been
therefore deemed to be idio-electro-positive like oxygen and chlorine.
It derives its name from its nauseous smell, Βρῶμος, _fœtor_. It occurs
in various saline springs on the continent of Europe, in those of Ashby
de la Zouche, and some others in England; in the lake Asphaltites, in
sponges, in some marine plants, in an ore of zinc, and in the cadmium of
Silesia. At ordinary temperatures it is liquid, of a dark brown colour
in mass, but of a hyacinth-red in thin layers. Its smell is rank and
disagreeable, somewhat like that of chlorine. It has a very caustic
taste. Its specific gravity is 2·966. Applied to the skin it colours it
deep yellow and corrodes it. One drop put within the bill of a bird
suffices to kill it. It combines with oxygen with feeble affinity,
forming bromic acid. Its attraction for hydrogen being far more
energetic, it forms therewith a strong acid, the hydrobromic.
Bromine dissolves very sparingly in water, but it is very soluble in
alcohol and ether. It combines with carbone, phosphorus, sulphur, and
chlorine, as well as with most of the metals. From its scarcity it has
not hitherto been applied to any purpose in the arts, but it is supposed
to possess powerful discutient effects upon scrophulous and other
glandular tumours, whence the waters containing it are prescribed as an
internal and external remedy in such forms of disease.
BRONZE. A compound metal consisting of copper and tin, to which
sometimes a little zinc and lead are added. This alloy is much harder
than copper, and was employed by the ancients to make swords, hatchets,
&c., before the method of working iron was generally understood. The art
of casting bronze statues may be traced to the most remote antiquity,
but it was first brought to a certain degree of refinement by Theodoros
and Rœcus of Samos, about 700 years before the Christian era, to whom
the invention of modelling is ascribed by Pliny. The ancients were well
aware that by alloying copper with tin, a more fusible metal was
obtained, that the process of casting was therefore rendered easier, and
that the statue was harder and more durable; and yet they frequently
made them of copper nearly pure, because they possessed no means of
determining the proportions of their alloys, and because by their mode
of managing the fire, the copper became refined in the course of
melting, as has happened to many founders in our own days. It was during
the reign of Alexander that bronze statuary received its greatest
extension, when the celebrated artist Lysippus succeeded by new
processes of moulding and melting to multiply groups of statues to such
a degree that Pliny called them the _mob of Alexander_. Soon afterwards
enormous bronze colossuses were made, to the height of towers, of which
the isle of Rhodes possessed no less than one hundred. The Roman consul
Mutianus found 3,000 bronze statues at Athens, 3,000 at Rhodes, as many
at Olympia and at Delphi, although a great number had been previously
carried off from the last town.
In forming such statues, the alloy should be capable of flowing readily
into all the parts of the mould, however minute; it should be hard, in
order to resist accidental blows, be proof against the influence of the
weather, and be of such a nature as to acquire that greenish oxidized
coat upon the surface which is so much admired in the antique bronzes,
called _patina antiqua_. The chemical composition of the bronze alloy is
a matter therefore of the first moment. The brothers Keller, celebrated
founders in the time of Louis XIV., whose _chefs d’œuvre_ are well
known, directed their attention towards this point, to which too little
importance is attached at the present day. The statue of Desaix in the
Place Dauphine, and the column in the Place Vendôme are noted specimens
of most defective workmanship from mismanagement of the alloys of which
they are composed. On analyzing separately specimens taken from the
bas-reliefs of the pedestal of this column, from the shaft, and from the
capital, it was found that the first contained only six per cent. of
alloy, and 94 of copper, the second much less, and the third only 0·21.
It was therefore obvious that the founder, unskilful in the melting of
bronze, had gone on progressively refining his alloy, by the oxidizement
of the tin, till he had exhausted the copper, and that he had then
worked up the refuse scoriæ in the upper part of the column. The cannons
which the government furnished him for casting the monument consisted
of--
Copper 89·360
Tin 10·040
Lead 0·102
Silver, zinc, iron, and loss 0·498
-------
100·000
The moulding of the several bas-reliefs was so ill executed, that the
chiselers employed to repair the faults removed no less than 70 tons of
bronze, which was given them, besides 300,000 francs for their work. The
statues made by the Kellers at Versailles were found on chemical
analysis to consist of--
No. 1. No. 2. No. 3. The mean.
Copper 91·30 91·68 91·22 91·40
Tin 1·00 2·32 1·78 1·70
Zinc 6·09 4·93 5·57 5·53
Lead 1·61 1·07 1·43 1·37
------ ------ ------ ------
100·00 100·00 100·00 100·00
The analysis of the bronze of the statue of Louis XV. was as follows:--
Copper 82·45 Its specific gravity was 8·482.
Zinc 10·30
Tin 4·10
Lead 3·15
------
100·00
The alloy most proper for bronze medals which are to be afterwards
struck, is composed of from 8 to 12 parts of tin and from 92 to 88 of
copper; to which if 2 or 3 parts in the hundred of zinc be added they
will make it assume a finer bronze tint. The alloy of the Kellers is
famous for this effect. The medal should be subjected to three or four
successive stamps of the press, and be softened between each blow by
being heated and plunged into cold water.
The bronze of bells or bell metal is composed in 100 parts of copper 78,
tin 22. This alloy has a fine compact grain, is very fusible and
sonorous. The other metals sometimes added are rather prejudicial, and
merely increase the profit of the founders. Some of the English bells
consist of 80 copper, 10·1 tin, 5·6 zinc, and 4·3 lead; the latter metal
when in such large quantity is apt to cause insulated drops, hurtful to
the uniformity of the alloy.
The _tam-tams and cymbals of bronze_.--The Chinese make use of bronze
instruments forged by the hammer, which are very thin, and raised up in
the middle; they are called gongs, from the word _tshoung_ which
signifies a bell. Klaproth has shown that they contain nothing but
copper and tin; in the proportions of 78 of the former metal and 22 of
the latter. Their specific gravity is 8·815. This alloy when newly cast
is as brittle as glass, but by being plunged at a cherry-red heat into
cold water and confined between two discs of iron to keep it in shape,
it becomes tough and malleable. The cymbals consist of 80 parts copper
and 20 tin.
Bronze vessels naturally brittle may be made tenacious by the same
ingenious process, for which the world is indebted to M. Darcet. Bronze
mortars for pounding have their lips tempered in the same way. Ancient
warlike weapons of bronze were variously compounded; swords were formed
of 87-1/2 copper, and 12-1/2 tin in 100 parts; the springs of balistæ
consisted of 97 copper, and 3 tin.
_Cannon metal_ consists of about 90 or 91 copper, and 10 or 9 of tin.
From the experiments of Papacino-d’Antony, made at Turin, in 1770, it
appears that the most proper alloy for great guns is from 12 to 14
parts of tin to 100 of copper; but the Comte Lamartilliere concluded
from his experiments made at Douay, in 1786, that never less than 8 nor
more than 11 of tin should be employed in 100 parts of bronze.
_Gilt ornaments of bronze._--This kind of bronze should be easy of
fusion, and take perfectly the impression of the mould. The alloy of
copper and zinc is when fused of a pasty consistence, does not make a
sharp cast, is apt to absorb too much amalgam, is liable to crack in
cooling, and is too tough or too soft for the chaser or the turner. Were
the quantity of zinc increased to make the metal harder, it would lose
the yellow colour suitable to the gilder. A fourfold combination of
copper, zinc, tin, and lead, is preferable for making such ornamental
bronze articles; and the following proportions are probably the best, as
they unite closeness of grain with the other good qualities. Copper 82,
zinc 18, tin 3 or 1, lead 1-1/2 or 3. In the alloy which contains most
lead, the tenacity is diminished and the density is increased, which is
preferable for pieces of small dimensions. Another alloy which is said
to require for its gilding only two thirds of the ordinary quantity of
gold, has the following composition: copper, 82·257; zinc, 17·481; tin,
0·238; lead, 0·024.
The antique bronze colour is given to figures and other objects made
from these alloys by the following process:--Two drams of sal-ammoniac,
and half a dram of salt of sorrel, (binoxalate of potash,) are to be
dissolved in fourteen ounce measures (English) of colourless vinegar. A
hair pencil being dipped into this solution, and pressed gently between
the fingers, is to be rubbed equally over the clean surface of the
object slightly warmed in the sun or at a stove; and the operation is to
be repeated till the wished for shade is obtained. (See GILDING.)
The bronze founder ought to melt his metals rapidly, in order to prevent
the loss of tin, zinc, and lead, by their oxidizement. Reverberatory
furnaces have been long used for this operation; the best being of an
elliptical form. The furnaces with dome tops are employed by the bell
founders, because their alloy being more fusible, they do not require so
intense a heat; but they also would find their advantage in using the
most rapid mode of fusion. The surface of the melting metals should be
covered with small charcoal, or coke; and when the zinc is added, it
should be dextrously thrust to the bottom of the melted copper.
Immediately after stirring the melted mass so as to incorporate its
ingredients, it should be poured out into the moulds. In general the
metals most easily altered by the fire, as the tin, should be put in
last. The cooling should be as quick as possible in the moulds to
prevent the risk of the metals separating from each other in the order
of their density, as they are very apt to do. The addition of a little
iron, in the form of tin-plate, to bronze, is reckoned to be
advantageous.
One part of tin, and two parts of copper, (nearly one atom of tin and
four of copper, or more exactly 100 parts of tin, and 215 copper,) form
the ordinary speculum metal of reflecting telescopes, which is of all
the alloys the whitest, the most brilliant, the hardest, and the most
brittle. The alloy of 1 part of tin, and 10 of copper, (or nearly one
atom of the former to eighteen of the latter,) is the strongest of the
whole series.
Ornamental objects of bronze, after being cast, are commonly laid upon
red-hot coals till they take a dull red heat, and are then exposed for
some time to the air. The surface is thereby freed from any greasy
matter, some portion of the zinc is dissipated, the alloy assumes more
of a coppery hue, which prepares for the subsequent gilding. The black
tinge which it sometimes gets from the fire may be removed by washing it
with a weak acid. It may be made very clean by acting upon it with
nitric acid, of specific gravity 1·324, to which a little common salt
and soot have been added, the latter being of doubtful utility; after
which it must be well washed in water, and dried with rags or saw dust.
BRONZING, is the art of giving to objects of wood, plaster, &c. such a
surface as makes them appear as if made of bronze. The term is sometimes
extended to signify the production of a metallic appearance of any kind
upon such objects. They ought first to be smeared over smoothly with a
coat of size or oil varnish, and when nearly dry, the metallic powder
made from Dutch foil, gold leaf, mosaic gold, or precipitated copper, is
to be applied with a dusting bag, and then rubbed over the surface with
a linen pad; or the metallic powders may be mixed with the drying oil
beforehand, and then applied with a brush. Sometimes fine copper, or
brass filings, or mosaic gold, are mixed previously with some pulverized
bone ash, and then applied in either way. A mixture of these powders
with mucilage of gum arabic is used to give paper or wood a bronze
appearance. The surface must be afterwards burnished. Copper powder
precipitated by clean plates of iron, from a solution of nitrate of
copper, after being well washed and dried, has been employed in this
way, either alone or mixed with pulverized bone-ash. A finish is given
to works of this nature by a coat of spirit varnish.
A white metallic appearance is given to plaster figures by rubbing over
them an amalgam of equal parts of mercury, bismuth, and tin, and
applying a coat of varnish over it. The iron-coloured bronzing is given
by black lead or plumbago, finely pulverized and washed. Busts and
other objects made of cast iron acquire a bronze aspect by being well
cleaned and plunged in solution of sulphate of copper, whereby a thin
film of this metal is left upon the iron.
Copper acquires by a certain treatment a reddish or yellowish hue, in
consequence of a little oxide being formed upon its surface. Coins and
medals may be handsomely bronzed as follows: 2 parts of verdigris and 1
part of sal ammoniac are to be dissolved in vinegar; the solution is to
be boiled, skimmed, and diluted with water till it has only a weak
metallic taste, and upon further dilution lets fall no white
precipitate. This solution is made to boil briskly, and is poured upon
the objects to be bronzed, which are previously made quite clean,
particularly free from grease, and set in another copper pan. This pan
is to be put upon the fire, that the boiling may be renewed. The pieces
under operation must be so laid that the solution has free access to
every point of their surface. The copper hereby acquires an agreeable
reddish brown hue, without losing its lustre. But if the process be too
long continued, the coat of oxide becomes thick, and makes the objects
appear scaly and dull. Hence they must be inspected every 5 minutes, and
be taken out of the solution the moment their colour arrives at the
desired shade. If the solution be too strong, the bronzing comes off
with friction, or the copper gets covered with a white powder, which
becomes green by exposure to air, and the labour is consequently lost.
The bronzed pieces are to be washed with many repeated waters, and
carefully dried, otherwise they would infallibly turn green. To give
fresh-made bronze objects an antique appearance, three quarters of an
ounce of sal ammoniac, and a dram and a half of binoxalate of potash
(salt of sorrel) are to be dissolved in a quart of vinegar, and a soft
rag or brush moistened with this solution is to be rubbed over the clean
bright metal, till its surface becomes entirely dry by the friction.
This process must be repeated several times to produce the full effect;
and the object should be kept a little warm. Copper acquires very
readily a brown colour by rubbing it with a solution of the common liver
of sulphur, or sulphuret of potash.
The Chinese are said to bronze their copper vessels by taking 2 ounces
of verdigris, 2 ounces of cinnabar, 5 ounces of sal ammoniac and 5
ounces of alum, all in powder, making them into a paste with vinegar,
and spreading this pretty thick like a pigment on the surfaces
previously brightened. The piece is then to be held a little while over
a fire, till it becomes uniformly heated. It is next cooled, washed, and
dried; after which it is treated in the same way once and again till the
wished-for colour is obtained. An addition of sulphate of copper makes
the colour incline more to chesnut brown, and of borax more to yellow.
It is obvious that the cinnabar produces a thin coat of sulphuret of
copper upon the surface of the vessel, and might probably be used with
advantage by itself.
To give the appearance of antique bronze to modern articles, we should
dissolve 1 part of sal ammoniac, 3 parts of cream of tartar, and 6 parts
of common salt in 12 parts of hot water, and mix with the solution 8
parts of a solution of nitrate of copper of specific gravity 1·160. This
compound, when applied repeatedly in a moderately damp place to bronze,
gives it in a short time a durable green coat, which becomes by degrees
very beautiful. More salt gives it a yellowish tinge, less salt a bluish
cast. A large addition of sal ammoniac accelerates the operation of the
mordant.
BROWNING _of gun-barrels and other arms._--By this process, the surface
of several articles of iron acquires a shining brown colour. This
preparation, which protects the iron from rust, and also improves its
appearance, is chiefly employed for the barrels of fowling-pieces and
soldier’s rifles, to conceal the fire-arms from the game and the enemy.
The finest kind of browning is the Damascus, in which dark and bright
lines run through the brown ground.
This operation consists in producing a very thin uniform film of oxide
or rust upon the iron, and giving a gloss to its surface by rubbing wax
over it, or coating it with a shell-lac varnish.
Several means may be employed to produce this rust speedily and well.
The effect may be obtained by inclosing the barrels in a space filled
with the vapour of muriatic acid. Moistening their surface with dilute
muriatic or nitric acid, will answer the same purpose. But the most
common material used for browning, is the butter or chloride of
antimony, which, on account of its being subservient to this purpose,
has been called _bronzing salt_. It is mixed uniformly with olive oil,
and rubbed upon the iron slightly heated; which is afterwards exposed to
the air, till the wished-for degree of browning is produced. A little
aquafortis is rubbed on after the antimony, to quicken its operation.
The brown barrel must be then carefully cleaned, washed with water,
dried, and finally polished, either by the steel burnisher, or rubbed
with white wax, or varnished with a solution of 2 ounces of shell-lac,
and 3 drams of dragon’s blood, in 2 quarts of spirit of wine.
The following process may also be recommended: Make a solution with half
an ounce of aquafortis, half an ounce of sweet spirit of nitre, 1 ounce
of spirit of wine, 2 ounces of sulphate of copper, and 1 ounce of
tincture of iron, in so much water as will fill altogether a quart
measure. The gun barrel to be browned must first of all be filed and
polished bright, and then rubbed with unslaked lime and water to clear
away all the grease. Its two ends must now be stopped with wooden rods,
which may serve as handles, and the touch-hole must be filled with wax.
The barrel is then to be rubbed with that solution, applied to linen
rags or a sponge, till the whole surface be equally moistened; it is
allowed to stand 24 hours, and is then scrubbed with a stiff brush. The
application of the liquid and the brushing may be repeated twice or
oftener, till the iron acquires a fine brown colour. After the last
brushing, the barrel must be washed with plenty of boiling water,
containing a little potash; then washed with clean water, dried, rubbed
with polishing hard wood, and coated with shell-lac varnish, for which
purpose the barrel must be heated to the boiling point of water. It is
finally polished with a piece of hard wood.
Storch recommends to make a browning solution with 1 part of sulphate of
copper, one third of a part of sulphuric ether, and 4 parts of distilled
water.
To give the damask appearance, the barrel must be rubbed over first with
very dilute aquafortis and vinegar, mixed with a solution of blue
vitriol; washed and dried, and rubbed with a hard brush to remove any
scales of copper which may be precipitated upon it from the sulphate.
Statues, vases, bas-reliefs, and other objects made of gypsum, may be
durably bronzed, and bear exposure to the weather better than after the
ordinary oil-varnish, by the following process:--Prepare a soap from
linseed oil, boiled with caustic soda lye, to which add a solution of
common salt, and concentrate it by boiling, till it becomes somewhat
granular upon the surface. It is then thrown upon a piece of linen
cloth, and strained with moderate pressure. What passes through is to be
diluted with boiling water, and again filtered. On the other hand, 4
parts of blue vitriol and 1 part of copperas are to be dissolved
separately in hot water. This solution is to be poured slowly into the
solution of soap, as long as it occasions any precipitate. This
flocculent matter is a mixture of cupreous soap and ferruginous soap,
that is, a combination of the oxides of copper and iron with the
margaric acid of the soda soap. The copper soap is green, the iron soap
is reddish brown, and both together resemble that green rust which is
characteristic of the antique bronzes. When the precipitate is
completely separated, a fresh portion of the vitriol solution is to be
poured upon it in a copper pan, and is made to boil, in order to wash
it. After some time, the liquid part must be decanted, and replaced by
warm water for the purpose of washing the metallic soaps. They are
finally treated with cold water, pressed in a linen bag, drained and
dried. In this state the compound is ready for use in the following
way:--
Three pounds of pure linseed oil are to be boiled with twelve ounces of
finely-powdered litharge, then strained through a coarse canvass cloth,
and allowed to stand in a warm place till the soap turns clear. Fifteen
ounces of this soap-varnish, mixed with 12 ounces of the above metallic
soaps, and 5 ounces of fine white wax, are to be melted together at a
gentle heat in a porcelain basin, by means of a water bath. The mixture
must be kept for some time in a melted state, to expel any moisture
which it may contain. It must be then applied, by means of a painter’s
brush, to the surface of the gypsum previously heated to the temperature
of about 200° F. By skilful management of the heat, the colour may be
evenly and smoothly laid on without filling up the minute lineaments of
the busts. When, after remaining in the cool air for a few days, the
smell of the pigment has gone off, the surface is to be rubbed with
cotton wool, or a fine linen rag, and variegated with a few streaks of
metal powder or shell gold. Small objects may be dipped in the melted
mixture, and then exposed to the heat of a fire till they are thoroughly
penetrated and evenly coated with it.
BROWN DYE. Upon this subject some general views are given in the article
DYEING, explanatory of the nature of this colour, to which I may in the
first place refer. This dye presents a vast variety of tints, from
yellow and red to black brown, and is produced either by mixtures of
red, yellow, and blue with each other, or of yellow or red with black,
or by substantive colours, such as catechu or oxide of manganese, alone.
We shall here notice only the principal shades; leaving their
modifications to the caprice or skill of the dyer.
1. Brown from mixture of other colours.
Wool and woollen cloths must be boiled with one eighth their weight of
alum and sulpho-tartrate of iron (see this article); afterwards washed,
and winced through the madder bath, which dyes the portion of the stuff
imbued with the alum red, and that with the salt of iron black; the tint
depending upon the proportion of each, and the duration of the madder
bath.
A similar brown is produced by boiling every pound of the stuff with two
ounces of alum, and one ounce of common salt, and then dyeing it in a
bath of logwood containing either sulphotartrate, acetate, or sulphate
of iron. Or the stuff may be boiled with alum and tartar, dyed up in a
madder bath, and then run through a black bath of iron mordant and galls
or sumach. Here the black tint is added to the red till the proper hue
be hit. The brown may be produced also by adding some iron liquor to the
madder bath, after the stuff has been dyed up in it with alum and
tartar. A better brown of this kind is obtained by boiling every pound
of wool with 2 ounces of alum, dyeing it up in cochineal, then changing
the crimson thus given into brown, by turning the stuff through the bath
after acetate of iron has been added to it. Instead of the cochineal,
archil or cutbear, with a little galls or sumach, may be used.
Wool or silk may also receive a light blue ground from the indigo vat,
then be mordanted with alum, washed, and turned through a madder bath
till the wished-for brown be brought out. For the deeper shades, galls
or sumach may be added to the paler Brazil-wood, with more or less iron
mordant. Instead of the indigo vat, Saxon blue may be employed to ground
the stuff before dyeing it with madder, or 5 pounds of madder, with 1
pound of alum, a solution of one tenth of a pound of indigo in sulphuric
acid, may be used with the proper quantity of water for 20 pounds of
wool; for dark shades some iron mordant may be added. Or we may combine
a bath of cochineal or cutbear, fustic, and galls, and add to it
sulphate of iron and sulphate of indigo, blunted with a little potash.
If we boil woollen cloth with alum and tartar, then pass it through a
madder bath, and afterwards through one of weld or fustic, containing
more or less iron mordant, we obtain shades variable, according to the
proportions of the materials, from _mordoré_ and cinnamon to chesnut
brown.
After the same manner, bronze colours may be obtained from the union of
olive dyes with red. For 25 pounds of cloth, we take 4 pounds of fustic
chips, boil them for 2 hours, turn the cloth in this bath for an hour,
and drain it; then add to the bath from 4 to 6 ounces of sulphate of
iron, and 1 pound of ordinary madder, or 2 pounds of sandal wood; put
the cloth again in this compound bath, and turn it through, till the
desired shade be obtained. By changing the proportions, and adding an
iron mordant, other tints may be produced.
This mode of dyeing is suitable for silk, but with three different
baths, one of logwood, one of Brazil-wood, and one of fustic. The silk,
after being boiled with soap, is to be alumed, and then dyed up in a
bath compounded of these three decoctions, mixed in the requisite
proportions. By the addition of walnut peels, sulphate of copper, and a
little sulphate of iron, or by passing the silk through a bath of
annotto, a variety of brown shades may be had.
Or the silk may receive an annotto ground, and then be passed through a
bath of logwood or Brazil-wood. For 10 pounds of silk, 6 ounces of
annotto are to be taken, and dissolved with 18 ounces of potashes in
boiling water. The silk must be winced through this solution for 2
hours, then wrung out, dried, next alumed, passed through a bath of
Brazil-wood, and finally through a bath of logwood containing some
sulphate of iron. It is to be wrung out and dried.
Brown of different shades is imparted to cotton and linen, by
impregnating them with a mixed mordant of acetates of alumina and iron,
and then dyeing them up, either with madder alone, or with madder and
fustic. When the aluminous mordant predominates, the madder gives an
amaranth tint. For horse-chesnut brown, the cotton must be galled,
plunged into a black bath, then into a bath of sulphate of copper, next
dyed up in a decoction of fustic, wrung out, passed through a strong
madder bath, then through the sulphate of copper solution, and finished
with a soap boil. Different shades of cinnamon are obtained, when
cottons first dyed up with madder get an olive cast with iron liquor in
a fustic bath.
These cinnamon and mordoré shades are also produced by dyeing them first
in a bath of weld and verdigris, passing them through a solution of
sulphate of iron, wringing and drying them; next putting them through a
bath containing 1 pound of galls for 10 pounds of stuff, again drying,
next aluming, and maddering. They must be brightened by a boil in soap
water.
A superior brown is produced by like means upon cotton goods, which have
undergone the oiling process of the Turkey red dye. Such stuffs must be
galled, mordanted with alum (see MADDER), sulphate of iron, and acetate
of lead (equal to 2/3 of the alum); after washing and drying, dyed in a
madder bath, and cleared with a soap boil. The tint of brown varies with
the proportion of alum and sulphate of iron.
We perceive from these examples, in how many ways the browning of dyes
may be modified, upon what principles they are founded, and how we have
it in our power to turn the shade more or less towards red, black,
yellow, blue, &c.
Brown may be produced by direct dyes. The decoction of oak bark dyes
wool a fast brown of different shades, according to the concentration of
the bath. The colour is more lively with the addition of alum.
The decoction of bastard marjoram (_Origanum vulgare_) dyes cotton and
linen a reddish brown, with acetate of alumina. Wool takes from it a
dark brown.
The bark of the mangrove tree (_Rizophora mangle_) affords to wool
boiled with alum and tartar a fine red brown colour, which, with the
addition of sulphate of iron, passes into a fast chocolate.
The _Bablah_, the pods of the East Indian _Mimosa cineraria_, and the
African _Mimosa nilotica_, gives cotton a brown with acetate or sulphate
of copper.
The root of the white sea rose (_Nymphæa alba_) gives to cotton and wool
beautiful shades of brown. A mordant of sulphate of iron and zinc is
first given, and then the wool is turned through the decoction of the
root, till the wished-for shade is obtained. The cotton must be
mordanted with a mixture of the acetates of iron and zinc.
Walnut peels (_Juglans regia_), when ripe, contain a dark brown dye
stuff, which communicates a permanent colour to wool. The older the
infusion or decoction of the peels, the better dye does it make. The
stuff is dyed in the lukewarm bath, and needs no mordant, though it
becomes brighter with alum. Or this dye may be combined with the madder
or fustic bath, to give varieties of shade. For dyeing silk, this bath
should be hardly lukewarm, for fear of causing inequality of colour.
The peelings of horse-chesnuts may be used for the same purpose. With
muriate of tin they give a bronze colour, and with acetate of lead a
reddish brown.
Catechu gives cotton a permanent brown dye, as also a bronze, and
mordoré, when its solution in hot water is combined with acetate or
sulphate of copper, or when the stuff is previously mordanted with the
acetates of copper and alumina mixed, sometimes with a little iron
liquor, rinsed, dried, and dyed up, the bath being at a boiling heat.
Ferrocyanate of copper gives a yellow brown or a bronze to cotton and
silk.
The brown colour called _carmelite_ by the French is produced by one
pound of catechu to four ounces of verdigris, with five ounces of
muriate of ammonia.--The bronze (_solitaire_) is given by passing the
stuff through a solution of muriate or sulphate of manganese, with a
little tartaric acid, drying, passing through a potash lye at 4° Baumé,
brightening and fixing with solution of chloride of lime.
BRUSHES. (_Brosses_, Fr.; _Bürsten_, Germ.) Mr. T. Mason obtained a
patent in October, 1830, for an improvement in the manufacture of this
article. It consists in a firmer mode of fixing the knots or small
bundles of hair into the stock or the handle of the brush. This is done
by forming grooves in the stocks of the brushes, for the purpose of
receiving the ends of the knots of hair, instead of the holes drilled
into the wood, as in brushes of the common constructions. These grooves
are to be formed like a dovetail, or wider at the bottom than the top;
and when the ends of the knots of hair have been dipped into cement,
they are to be placed in the grooves and compressed into an oval form,
by which the ends of the hair will be pressed outwards into the recess
or wider part of the dovetailed groove, or the grooves may be formed
with threads or teeth on the sides, instead of being dovetailed; and the
cement and hairs being pressed into the teeth or threads, will cause
them to adhere firmly to the stock or handle of the brush.
[Illustration: 182 183 184]
A metal ferrule may be placed on the outside of the stock of the brush,
if necessary, and secured by pins or rivets, or in any other convenient
manner, which ferrule may also form one side of the outer groove. _Fig._
182. is a plan view of the stock of a round brush; _fig._ 183. is a
section of the same; _a a_ are the dovetailed grooves, which are turned
out of the wood; _b_ is the metal ferrule; _c c_ are knots or small
bundles of hair, to form the brush. After a number of the knots of hair
are prepared, the ends are to be dipped into proper cement, and then
placed into the grooves, when their ends are to be squeezed by a pair of
plyers, or other means, which will compress them into the oval shape, as
shown in _fig._ 184., and cause the ends of the hairs to extend outward
under the dovetailed part of the recess.
The knots of hair are to be successively placed in the grooves, and
forced up by a tool against the last knot put in, and so on, until the
grooves are filled; _fig._ 184. is a section taken through a brush with
teeth or threads of a screw formed upon the sides of the groove; into
these teeth or threads the cement and hairs will be forced by the
compression, by which means they will be held firmly in the stock of the
brush.
BUTTER. (_Beurre_, Fr.; _Butter_, Germ.) Milk contains a fatty matter of
more or less consistency, modified very much according to the nature of
the animals which afford it. This substance is butter, held suspended in
the milk by means of the caseous matter and whey, with which it is
intimately blended. Milk is a true emulsion resulting from the mixture
of these three ingredients, owing its opacity and white colour to the
diffusion through it of that butyraceous oil. When any circumstance
dissolves this union, each component becomes insulated, and manifests
its peculiar properties. Milk, even left to itself, at a temperature of
from 50° to 60° F., separates spontaneously into several products. A
layer of a fatter, more consistent, but lighter nature, floats upon its
surface, while the subjacent liquid forms a white magma, which retains
among its curdy flocks all the whey of the milk. The upper layer or
cream contains nearly the whole of the butter; but a portion remains
entangled with the curd and whey below.
It belongs to a work on husbandry or rural economy to treat fully of the
operations of the dairy; one of the principal of which is the extraction
of butter from milk.
The Tartars and French have been long in the habit of preserving butter,
by melting it with a moderate heat, whereby are coagulated the
albuminous and curdy matters remaining in it, which are very
putrescible. This fusion should be made by a heat of a water bath, about
176° F., continued for some time, to effect the more complete
purification of the butter. If in this settled liquified state it be
carefully decanted, strained through a tammy cloth, and slightly salted,
it may be kept for a long time nearly fresh, without becoming in any
degree rancid, more especially if it be put up in small jars closely
covered.
BUTTER OF CACAO. See CACAO and OILS.
BUTTON MANUFACTURE. This art is divided into several branches,
constituting so many distinct trades. Horn, leather, bone, and wood, are
the substances frequently employed for buttons, which are either plain,
or covered with silk, mohair thread, or other ornamental materials. The
most durable and ornamental buttons are made of various metals,
polished, or covered with an exceedingly thin wash, as it is termed, of
some more valuable metal, chiefly tin, silver, and gold.
Those buttons intended to be covered with silk, &c. are termed, in
general, moulds. They are small circles, perforated in the centre, and
made from those refuse chips of bone which are too small for other
purposes. These chips, which, for the large and coarser buttons, are
pieces of hard wood, are sawn into thin flakes, of an equal thickness;
from which, by a machine, the button moulds are cut out at two
operations.
The shavings, sawdust, and more minute fragments, are used by
manufacturers of cutlery and iron toys, in the operations of
case-hardening; so that not the smallest waste takes place.
Metal buttons are formed of an inferior kind of brass, pewter, and other
metallic compositions: the shanks are made of brass or iron wire, the
formation of which is a distinct trade. The buttons are made by casting
them round the shank. For this purpose the workman has a pattern of
metal, consisting of a great number of circular buttons, connected
together in one plane by very small bars from one to the next; and the
pattern contains from four to twelve dozen of buttons of the same size.
An impression from this pattern is taken in sand in the usual manner;
and shanks are pressed into the sand in the centre of each impression,
the part which is to enter the metal being left projecting above the
surface of the sand. The buttons are now cast from a mixture of brass
and tin; sometimes a small proportion of zinc is added, which is found
useful in causing the metal to flow freely into the mould, and make a
sharp casting. When the buttons are cast, they are cleaned from the sand
by brushing; they are then broken asunder, and carried to a second
workman at the lathe, who inserts the shank of a button into a chuck of
a proper figure, in which it is retained by the back centre of the lathe
being pressed against the button with a spring. The circumference is
now, by filing it as it turns round, reduced to a true circle; and the
button is instantly released by the workman’s holding back the centre,
and is replaced by another. A third workman now turns the back of the
button smooth, in a chuck lathe, and makes the projecting part round the
shank true; and a fourth renders the face of the button smooth, by
placing it in a chuck, and applying the edge of a square bar of steel
across its centre.
Gilt buttons are stamped out from copper, (having sometimes a small
alloy of zinc,) laminated in the flatting mill to the proper thickness.
The stamp is urged by a fly-press, which cuts them out at one stroke.
These circular pieces, called blanks, are annealed in a furnace to
soften them; and the maker’s name, &c. is struck on the back by a
monkey, which is a machine very similar to a pile-engine. This stamp
also renders the face very slightly convex, that the buttons may not
stick together in the gilding process. The shanks are next soldered on.
The burnishing is performed by a piece of hematites or blood-stone,
fixed into a handle, and applied to the button as it revolves by the
motion of the lathe.
A great number of the buttons, thus prepared for gilding, are put into
an earthen pan, with the proper quantity of gold to cover them[14],
amalgamated with mercury in the following manner:--The gold is put into
an iron ladle, and a small quantity of mercury added to it; the ladle is
held over the fire, till the gold and mercury are perfectly united. This
amalgam being put into the pan with the buttons, as much aquafortis,
diluted with water, as will wet them all over, is thrown in, and they
are stirred up with a brush, till the acid, by its affinity to the
copper, carries the amalgam to every part of its surface, covering it
with the appearance of silver. When this is perfected, the acid is
washed away with clean water. This process by the workman is called
quicking.
[14] By act of parliament 5 grains of gold are allotted for the
purpose of gilding 144 buttons, though they may be tolerably well gilt
by half that quantity. In this last case, the thickness would be about
the 214,000th part of an inch.
The old process in gilding buttons, called the drying off, was
exceedingly pernicious to the operator, as he inhaled the vapour of the
mercury, which is well known to be a violent poison. In order to obviate
this, the following plan of apparatus has been employed with success.
The vapour, as it rises from the pan of buttons heated by a charcoal
fire, is conducted into an oblong iron flue or gallery, gently sloped
downwards, having at its end a small vertical tube dipping into a water
cistern, for condensing the mercury, and a large vertical pipe for
promoting the draught of the products of the combustion.
Plated buttons are stamped by the fly-press, out of copper-plate,
covered on one side with silver at the flatting-mill. The copper side is
placed upwards in stamping, and the die or hole through which they are
stamped, is rather chamfered at its edge, to make the silver turn over
the edge of the button. The backs are stamped in the same manner as the
gilt buttons. The shanks are soldered on with silver solder, and heated
one by one in the flame of a lamp, with a blow-pipe urged by bellows.
The edges are now filed smooth in the lathe, care being taken not to
remove any of the silver which is turned over the edge. They are next
dipped in acid, to clean the backs, and boiled in cream of tartar and
silver, to whiten them; after which they are burnished, the backs being
first brushed clean by a brush held against them as they revolve in the
lathe. The mode of burnishing is the same as for gilt buttons.
Button shanks are made by hand from brass or iron wire, bent and cut by
the following means:--
The wire is lapped spirally round a piece of steel bar. The steel is
turned round by screwing it into the end of the spindle of a lathe, and
the wire by this means lapped close round it till it is covered. The
coil of wire thus formed is slipped off, and a wire fork or staple with
parallel legs put into it. It is now laid upon an anvil, and by a punch
the coil of wire is struck down between the two prongs of the fork, so
as to form a figure 8, a little open in the middle. The punch has an
edge which marks the middle of the 8, and the coil being cut open by a
pair of shears along this mark, divides each turn of the coil into two
perfect button shanks or eyes.
[Illustration: 185 186 187 188 189]
Mr. Holmes, of Birmingham, obtained in May, 1833, a patent for an
improved construction of buttons. _Fig._ 185. represents the outside
appearance of one of his improved shanks, as raised or formed out of the
disc of metal which is to constitute the back of the button; _fig._
186. an edge view, looking through the shank or loop; _fig._ 187. is
another edge view, looking at the raised shank or loop endways; _fig._
188. is a section taken through the shank and disc in the direction of
the dotted line A B, in _fig._ 185.; and _fig._ 189. another section
taken in the direction of the dotted line C D, in _fig._ 185. All these
figures of his improved shanks, as well as those hereinafter described,
together with the tools used to form the same, are drawn at about half
the real size, to show the parts more distinctly. It will be seen that
the shanks or loops _a a_ are formed by partially cutting and raising,
or forcing up a portion of the metal disc or back _b_, and are
compressed or formed by the action of the tools, or punches and dies, so
as to have a rounded figure on the inside of the top part of the shank,
as at _c_, the edges of the metal being turned so as to prevent them
cutting the threads by which the button is fastened to the cloth or
garment. It will be observed that, there being but one passage or way
through which the thread can be passed to sew on the button, and that
opening being rounded on all edges, will cause the threads to keep in
the centre of the shanks, the form of the shank allowing a much neater
attachment to the garment, and keeping the threads from the edges of the
metal. The ends of the shank, or portions _e e_, which rise up from the
disc or back _b_, are made nearly circular, in order to avoid presenting
any edges of the metal to the sides of the button-hole; and when the
shank is sewed on the cloth, it forms, in conjunction with the threads,
a round attachment, thereby preventing the shank from cutting or wearing
the button-hole: the threads, when the shank is properly sewed to the
garment, nearly filling up the opening through the shank, and completing
that portion of the circle which has been taken out of the shank by the
dies in forming the crescented parts of the loop. It will be therefore
understood that the intention is, that the inside edges of the shank
should be turned as much as possible away from the threads by which the
button is sewed on the cloth, and that the outside of the shank should
be formed so as to present rounded surfaces to the button-hole, and that
the thread should fill up the opening through the shank, so as to
produce a round attachment to the garment. It should here be observed,
that the backs of the buttons shown in these figures are of the shape
generally used for buttons covered with Florentine or other fabric, or
faced with plates of thin metal, and are intended to have the edges of a
disc, or what is termed a shell, forming the face, to be closed in upon
the inclined or bevelled edges of the backs. Having now described the
peculiar form of the improved shanks which he prefers, for buttons to be
covered with Florentine or other fabric, or shells of thin metal plate,
he proceeds to describe some of the different variations from the same.
[Illustration: 190 191 192 193 194 195 196]
_Fig._ 190. is a representation of a shank, the cut through the disc or
back being effected by a parallel rib on the die, and corresponding
groove in the shaping punch, instead of the semi-circular or crescented
cut shown in _fig._ 185.; _fig._ 191. is a view of another shank, the
separation of the sides of the loop being performed by straight edges in
both punch and die. He prefers finishing this shaped shank (that is,
giving it the rounded form, to prevent its cutting the threads), by
detached punches, and dies, or pincers, as will be hereinafter
described. _Fig._ 192. is a representation of one of the improved
shanks, which has merely portions, _f f_, of the back of the button
connected to its ends. This shank may be used for buttons which have a
metal shell to be closed in upon the bevelled edges of the ends, or the
shank piece may be otherwise connected to the face part of the button.
_Fig._ 193. is a representation of a shank raised out of a small disc of
metal _g g_, intended to be soldered to the disc of metal forming the
button, or it may be otherwise fixed to the back; _fig._ 194. is a
representation of another shank for the same purpose, having only
portions of metal _h h_, for soldering or otherwise attaching it to the
back of the button, as by placing a ring or annular piece over it
forming the back, which shall be confined to the face, as before
described; _fig._ 195. is a representation of a shank raised upon a dish
or bevelled piece of metal, and is intended to be used for buttons made
from pearl-shell, horn, wood, paper, or other substances. The back part
of the button has a dovetailed recess formed in it to receive the
dish-shaped back, which is pressed into the recess, the edges of the
dish being expanded in the dovetailed parts of the recess by the
ordinary means, and thereby firmly fixing it to the button, as shown in
_fig._ 196.
[Illustration: 197 198 199 200 201 202 203 204]
Having now explained the peculiar forms of his improved shanks, he
proceeds to describe the tools, or punches and dies, by which he cuts
the disc or back from out of a sheet of metal, and at the same operation
produces and forms the shank complete. _Fig._ 197. is a longitudinal
section taken through a pair of dies and punches when separated; _fig._
198. is a similar section, taken when they are put together, and in the
act of forming a shank after cutting out the disc or back of the button
from a sheet of metal; _fig._ 199. is a face view of the punch; and
_fig._ 200. is a similar representation of the counter die, with the
tools complete, _a_ is the punch or cutter, and _b_ the counter bed, by
the circular edges of which the disc of metal is cut out of the sheet;
_c_ is a die, fixed in the cutter _a_, (upon which the name of the
button-maker may be engraved). _Fig._ 201. is a face view of this die
when removed out of the punch; _d_ is the counter die to the die _c_. It
will be perceived that these dies _c_ and _d_, together with the punch
and bed, compress the disc of metal into the form required for the back
of the button; that shown in the figures, as before stated, is of the
shape used for buttons to be covered with Florentine or thin plate
metal, in a round shell closed in upon the inclined or bevelled edge of
the back; _e_ is the cutting and shaping punch of the shank, which is
fixed within the counter die; this punch cuts through the metal of the
disc, and forms the shank as the dies approach nearer together, by
raising or forcing it up into the recess or opening in the die _c_,
where it is met by the end of another shaping punch _f_, fixed in the
punch _a_, which compresses the upper part of the shank into the recess
_g_, in the end of the punch _e_, thereby giving the shank its rounded
figure, and at the same time forming the other part of the shank into
the required shape, as described at _figs._ 185. to 189. The ends of
these shaping punches fit into and over each other, as will be seen by
the detached figures of the punches designed for forming the shank first
described. _Fig._ 202. is a representation of the punches when apart and
removed out of the dies; _fig._ 203. is a longitudinal section of the
same; _fig._ 204. is another view of the punches as seen on the top. The
sharp edge of the recess _h_, in the punch _e_, comes in contact with
the cutting edges of the projecting rib _i_, of the die _c_, and thereby
cuts through so much of the metal as is required. The edge _k_ of this
die keeps the outside ends of the shank of a spherical figure, as before
explained, while the punches force up the metal, and form the elevated
loop or shank: _u u_ are holes made through the counter die _d_, for the
passage of clearing pins, which force out the shank or back piece from
the counter die when finished; the operation of which will be shown when
describing the machinery hereafter. There are adjusting screws at the
back of the punches and dies, by which they can be regulated and brought
to their proper position one to the other.
[Illustration: 205]
Although he has shown the punches which form his improved shanks, fixed
into and working in conjunction with the punch and dies which cut out
and shape the discs of metal for the back of the button, yet he does not
intend to confine himself to that mode of using them, as flat blanks or
discs for the backs of buttons may be cut out in a separate stamping
press, and afterwards shaped in the same press or in another, and then
brought under the operation of the punches which form his improved
shanks, fixed in any suitable press. This last-mentioned mode of
producing button shanks and backs he prefers when such metals are
employed as require annealing between the operations of shaping the
backs and forming the shank. _Fig._ 205. is a section taken through a
pair of dies, in which the operation only of forming the shank is to be
performed, the backs being previously shaped in another press. In this
instance the punches _e_ and _f_ are mounted in guide-pieces _m_ and
_n_, which keep them in the proper position towards each other, the die
c being mounted in the piece _n_, and acting against the face of the
guide _m_. The blanks or backs of the buttons may be fed into these dies
by hand or any other means; and after the shank is formed, the finished
back can be pushed out of the lower die by clearing rods passed through
the holes _u u_, and removed by hand, or in any convenient manner.
[Illustration: 206 207 208 209]
When his improved shanks are formed out of iron or other metal which is
too brittle to allow of the shank being forced up and finished at one
operation in the dies and punches, he prefers cutting out and shaping
the blank or back of the button first, and after annealing it, to raise
or force up the portion of metal to form the shank into the shape shown
in _fig._ 206., that is, without the edges of the metal being turned to
prevent their cutting the threads, and after again annealing it, to bend
or turn the edges into the shape shown in _fig._ 191. by means of
suitable punches in another press, or by a pair of pincers and punch as
shown in _fig._ 207., which is a side view of a small apparatus to be
used for turning the edges of the shank by hand, with a partly formed
shank seen under operation. _a_, is the upper jaw of a pair of pincers,
this jaw being fixed on to the head of the standard _b_; the under jaw
_c_, is formed by the end of the lever or handle _d_, which has its
fulcrum in the standard _b_. _e_, is a small punch, passed through a
guide hole in the head of the standard, one end projecting into the jaws
of the pincers, the other against a piece _f_, attached by a joint to
the lever _d_, and working through a slot in the head of the standard;
this piece _f_, has an inclined plane on the side next the end of the
punch, which, in its descent, projects the punch forward against the top
of the loop of the shank, (placed at _g_,) as the pincers are closed by
forcing down the lever _d_, and, in conjunction with the jaws of the
pincers, compresses the shank into the required form, as shown at _h_,
and in the enlarged _fig._ 191. A spring, _i_, acts against a pin fixed
into the punch _e_, for the purpose of bringing it back as the jaws open
after forming a shank. _Figs._ 208. and 209. represent the face and
section of the dies mentioned before, for cutting the slits in the
discs, as at _fig._ 190.
[Illustration: 210]
[Illustration: 211]
[Illustration: 212]
[Illustration: 213 214]
Having explained the peculiar forms of his improved metallic shanks for
buttons, and the tools employed in making the same, he proceeds to
describe the machinery or apparatus by which he intends to carry his
invention into effect. He proposes to take a sheet of metal, say about
30 or 40 feet long, and of the proper width and thickness; which thin
sheet is to be wound upon a roller, and placed above the machine, so
that it can be easily drawn down into the machine as required for
feeding the punches and dies. _Fig._ 210. is a plan view of a machine,
intended to work any convenient number of sets of punches and dies
placed in rows. Eleven sets of punches and dies are represented, each
set being constructed as described under _figs._ 197 to 204; _fig._ 211.
is a side view, and _fig._ 212. a longitudinal section, taken through
the machine; _figs._ 213. and 214. are transverse sections taken through
the machine between the punches and counter dies, _fig._ 213.
representing its appearance at the face of the punches, and _fig._ 214.
the opposite view of the counter dies. _a a_, are the punches; _b b_,
the counter dies; each being mounted in rows in the steel plates _c c_,
fixed upon two strong bars _d_ and _e_, by countersunk screws and nuts,
the punches and dies being retained in their proper position by the
plates, which are screwed on to the front of the steel plates, and press
against the collars of the punches and dies. The bars _d_ and _e_ are
both mounted on the guide-pins _g g_, fixed in the heads _h h_ of the
frame, which guide pins pass through the bosses on the ends of the bars.
The bar _d_ is stationary upon the guide pins, being fixed to the heads
_h h_, by nuts and screws passed through ears cast on their bosses. The
bar _e_ slides freely upon the guide pins _g g_, as it is moved
backwards and forwards by the crank _i i_, and connecting-rods _j j_, as
the crank shaft revolves. The sheet of thin iron to be operated upon is
placed, as before stated, above the machine; its end being brought down
as at _a a_, and passed between the guide rod and clearing-plate _k_,
and between the pair of feeding-rollers _l l_, which, by revolving, draw
down a further portion of the sheet of metal between the punches and
dies, after each operation of the punches.
As the counter dies advance towards the punches, they first come in
contact with the sheet of metal to be operated upon; and after having
produced the pressure which cuts out the discs, the perforations of the
sheet are pushed on to the ends of the punches by the counter dies; and
in order that the sheet may be allowed to advance, the carriage which
supports the axles of the feeding-rollers, with the guide rod and
clearing-plate, are made to slide by means of the pin _m_, which works
in a slot in the sliding-piece _n_, bearing the axis of the
feeding-roller _l l_, the slide _n_, being kept in its place on the
frame work by dovetailed guides shown in _fig._ 214.
When the counter dies have advanced near to the sheet of metal, the pin
_m_ comes in contact with that end of the slot in the piece _n_, which
is next to the punches, and forces the carriage with feed-rollers and
clearing-plate, and also the sheet of metal, onwards, as the dies are
advanced by the reaction of the cranks; and after they have cut out the
discs, and raised the shanks, the sheet of metal will remain upon the
punches; and when the bar _e_ returns, the finished backs and shanks are
forced out of the counter dies, by the clearing-pins and rods _o o_,
which project through the bar _e_, and through the holes before
mentioned in the counter dies; these clearing-pins being stationary
between the bars _p p_, mounted upon the standard _q q_, on the cross
bar of the frame, as shown in _figs._ 210., 212., 213. Immediately after
this is done, the pins _m_ come in contact with the other ends of the
slots in the pieces _n_, and draw back the feeding-rollers _l l_,
together with the clearing-plate _k_, and the sheet of metal, away from
the punches into the position represented in the figures.
At this time the feeding of the metal into the machine is effected by a
crank-pin _r_, on the end of the crank-shafts coming in contact with the
bent end of the sliding-bar _s_, supported in standards _t t_; and as
the crank-shaft revolves, this pin _r_ forces the bar _s_ forward, and
causes the tooth or pall _u_, on its reverse end, to drive the
racket-wheel _v_, one or more teeth; and as the racket-wheel _v_ is
fixed on to the end of the axle of one of the rollers _l_, it will cause
t