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.