The manufacture divides itself into three branches:--1. The conversion
of sea salt, or chloride of sodium, into sulphate of soda. 2. The
decomposition of this sulphate into crude soda, called _black balls_ by
the workmen. 3. The purification of these balls, either into a dry white
soda-ash or into crystals.
[Illustration: 1033 1034 1035]
1. _The preparation of the sulphate of soda._--_Figs._ 1033, 1034, 1035.
represent the furnace for converting the muriate of soda into the
sulphate. The furnace must be built interiorly of the most refractory
fire-bricks, such as are used for glasshouses, but of the ordinary brick
size; except the bridges C, G, N, which should be formed of one mass,
such as what is called a Welsh lump. A is the ash-pit; B, the grate; C,
the first bridge, between the fire and the first calcining hearth, D, D;
F, F, is its roof; G, the second bridge, between the calcining hearth
and the decomposing hearth I, I, I; the roof of which is K, K. This
hearth I, I, is lined with a lead square pan, 5 or 6 inches deep, sloped
at the back opening, in _fig._ 1035., marked M´; which deficient part of
the upright side is filled up with two bricks placed one over the other,
as shown at _m_, _m_, _fig._ 1034., and luted with clay, to confine the
semi-liquid mass in the pan, I, I. Some manufacturers make this pan 8
inches deep, and line its bottom and sides with bricks or siliceous
sandstone, to protect the lead from the corrosive action of the acid.
There are others who consider this precaution troublesome, as the points
of the pan which become leaky are thereby concealed. In the roof of the
decomposing hearth, one or two syphon funnels R, of lead, are inserted
when the charge of acid (sulphuric) is to be poured down upon the salt
in I, I, to save the risk of any annoyance from the fumes of the
muriatic acid. O, O, is a chimney filled with round flint nodules, which
are kept continually moist by the trickling of a streamlet of water upon
the topmost layer. The muriatic gas meeting this descending film of
water upon so extensive a surface, becomes absorbed, and runs out below
in a liquid form. When the acid is required in a somewhat concentrated
state, this chimney should be made both high and capacious. Such a plan,
moreover, is very valuable for abating the nuisance caused by the
disengagement of the muriatic acid gas; which is otherwise apt to
sterilize the surrounding vegetation.
A fire being kindled in the grate B, _figs._ 1033. and 1034., 3 cwt. of
salt in powder are to be thrown by a shovel into the pan I, through the
door M, _fig._ 1035., or _m_, _m_, _fig._ 1034. Two hundred weight and a
half of oil of vitriol, of specific gravity 1·844 having been diluted
with from 25 to 30 per cent. of water, and well mixed, or 3 cwts. at 56°
Baumé, are to be slowly poured in by the funnel, and diffused among the
muriate of soda, by an occasional stir with an iron rake cased with
sheet lead. Fumes of muriatic acid will now plentifully escape, and,
passing up the condensing-shaft O, will flow down in the form of liquid
spirit of salt, and escape by the stoneware stopcock P, into the pipe of
a sunk cistern. The fire having been steadily kept up at a moderate
degree, the chemical reaction will be tolerably complete in the course
of two hours; but as this is relative to the nature of the fuel, and the
draught of the furnace, no very precise rule in point of time can be
laid down; but it is sufficient for this stage of the process, when the
fumes cease to be very dense and copious, as may be ascertained by
opening the door M, and looking in, or by the appearance at the top of
the shaft O. Over the door M´, in the opposite side of the decomposing
hearth, _fig._ 1035., there must be an arch or hood terminating in a
small chimney, 15 or 20 feet high, for the ascent of the muriatic
vapours, when the charge is drawn or run out of the hearth, and allowed
to fall into a square shallow iron tray, placed on the ground at the
back of the furnace. For this discharge, the two bricks which serve as
stoppers to that orifice, must be unluted and removed.
As soon as that charge is taken out, (the fire being meanwhile checked
by opening the door T, _fig._ 1034., and shutting partially the ash-pit
opening at A,) a fresh charge must be introduced as above described. The
nearly decomposed saline matter during the second charging of the hearth
I, will have grown cool and concrete. It must be shovelled into the
calcining hearth D, D, _fig._ 1033., by the back door Q, _fig._ 1035.,
where it will receive a higher degree of heat; and, by the expulsion of
the remaining part of the muriatic acid, it will become a perfect
sulphate of soda. It should be finally brought into a state of
semi-fusion. When a sample of it, taken out on the end of the rake or
trowel-shaped scraper, emits no fumes, the conversion is accomplished.
From 3 cwts. of common salt, or muriate of soda, rather more than 3-1/2
cwts. of perfect sulphate should be obtained, quite free from metallic
impurity.
The next step is the conversion of the sulphate into a crude soda.
[Illustration: 1036 1037 1038]
One of the most improved soda furnaces is that, employed in a few
factories, represented in _figs._ 1036, 1037, and 1038. In the section
_fig._ 1037., there are two hearths in one furnace, the one elevated
above the level of the other by the thickness of a brick, or about 3
inches. A is the preparatory shelf, where the mixture to be decomposed
is first laid in order to be thoroughly heated, so that when transferred
to the lower or decomposing hearth B, it may not essentially chill it,
and throw back the operation. C is the fire-bridge, and D is the grate.
In the horizontal section, or ground plan, _fig._ 1038., we see an
opening in the front corresponding to each hearth. This is a door, as
shown in the side view or elevation of the furnace, _fig._ 1036.; and
each door is shut by an iron square frame filled with a fire-tile or
bricks, and suspended by a chain over a pulley fixed in any convenient
place. See PITCOAL, COKING OF, p. 1041. The workman, on pushing up the
door lightly, makes it rise, because there is a counterweight at the
other end of each chain, which balances the weight of the frame and
bricks. In the ground plan, only one smoke-flue is shown; and this
construction is preferred by many manufacturers; but others choose to
have two flues, one from each shoulder, as at _a_, _b_; which two flues
afterwards unite in one vertical chimney, from 25 to 40 feet high;
because the draught of a soda-furnace must be very sharp. Having
sufficiently explained the construction of this improved furnace, I
shall now proceed to describe the mode of making soda with it.
The materials with which the sulphate is decomposed into a rough
carbonate of soda, are chalk or ground limestone, and ground coal or
charcoal. The proportions in which these three substances are mixed,
influence in a remarkable degree the success of the decomposing
process. I have known a false proportion introduced, and persevered in,
at a factory, with the most prejudicial effect to the product; the
soda-ash produced, being in a small quantity relatively to the sulphate
employed, and being much charged with sulphur. After very numerous
trials which I have made on the great scale, and many inquiries at the
most successful soda-works, both in this country and abroad, I am
warranted to offer the following proportions as the most profitable:--
Sulphate of soda, 100 parts: carbonate of lime (chalk or limestone),
from 110 to 120 parts; if pure, 110; if a little impure or damp, 120:
pit coal, 50 parts.
These materials must be separately ground by an edge-stone mill, and
sifted into a tolerably fine powder. They must be then very carefully
mixed. Attention to these particulars is of no little importance to the
success of the soda process.
One hundred parts or pounds of sulphate of soda are equivalent to 75
parts of carbonate, and when skilfully decomposed, will generally yield
fully 70 pounds. A charge for the decomposing furnace with the
preparatory shelf should not exceed 200 lbs., or perhaps 180; therefore
if 75 pounds of ground sulphate of soda, with 80 pounds of chalk or
limestone (ground), and 37 pounds of ground coal; be well mixed, they
will constitute one charge. This charge must be shovelled in upon the
hearth A, or shelf of preparation, (_fig._ 1037.); and whenever it has
become hot (the furnace having been previously brought to bright
ignition), it is to be transferred to the decomposing hearth or
laboratory B, by an iron tool, shaped exactly like an oar, called the
spreader. This tool has the flattened part from 2 to 3 feet long, and
the round part, for laying hold of and working by, from 6 to 7 feet
long. Two other tools are used; one, a rake, bent down like a garden hoe
at the end; and another, a small shovel, consisting of a long iron rod
terminated with a piece of iron plate, about 6 inches long, 4 broad,
sharpened and tipped with steel, for cleaning the bottom of the hearth
from adhering cakes or crusts. Whenever the charge is shoved by the
sliding motion of the oar down upon the working hearth, a fresh charge
should be thrown into the preparation shelf, and evenly spread over its
surface.
The hot and partially carbonized charge being also evenly spread upon
the hearth B, is to be left untouched for about ten minutes, during
which time it becomes ignited, and begins to fuse upon the surface. A
view may be taken of it through a peep-hole in the door, which should be
shut immediately, in order to prevent the reduction of the temperature.
When the mass is seen to be in a state of incipient fusion, the workman
takes the oar and turns it over breadth by breadth in regular layers,
till he has reversed the position of the whole mass, placing on the
surface the particles which were formerly in contact with the hearth.
Having done this, he immediately shuts the door, and lets the whole get
another decomposing heat. After five or six minutes, jets of flame begin
to issue from various parts of the pasty-consistenced mass. Now is the
time to incorporate the materials together, turning and spreading by the
oar, gathering them together by the rake, and then distributing them on
the reverse part of the hearth; that is, the oar should transfer to the
part next the fire-bridge the portion of the mass lying next the shelf,
and _vice versâ_. The dexterous management of this transposition
characterizes a good soda-furnacer. A little practice and instruction
will render this operation easy to a robust clever workman. After this
transposition, incorporation, and spreading, the door may be shut again
for a few minutes, to raise the heat for the finishing off. Lastly, the
rake must be dexterously employed to mix, shift, spread, and
incorporate. The jets, called _candles_, are very numerous, and bright
at first; and whenever they begin to fade, the mass must be raked out
into cast-iron moulds, placed under the door of the laboratory to
receive the ignited paste.
One batch being thus worked off, the other, which has lain undisturbed
on the shelf, is to be shoved down from A to B, and spread equally upon
it, in order to be treated as above described. A third batch is then to
be placed on the shelf.
The article thus obtained should contain at least 22 per cent. of real
soda, equivalent to 37 per cent. of dry carbonate, or to 100 of
crystals. A skilful workman can turn out a batch in from three quarters
of an hour to an hour, producing a perfect carbonate, which yields on
solution an almost colourless liquid, nearly destitute of sulphur, and
containing hardly any decomposed sulphate.
In some soda-works, where the decomposing furnace is very large, and is
charged with a ton of materials at a time, it takes two men to work it,
and from five to six hours to complete a batch. Having superintended the
operation of the above-described small furnace, and examined its
products, I feel warranted to recommend its adoption.
The following materials and products show the average state of this soda
process:--
_Materials_--100 parts of sulphate of soda, ground, equivalent to 7·5
of carbonate; 110 of chalk or ground limestone; 55 of
ground coal: in the whole, 265.
_Products_--168 parts of crude soda, at 33 per cent. = 55·5 of dry
carbonate.
{ 130 -- crystals of carbonate of soda = 48 of dry
Or, { carbonate; and
{ 100 -- insoluble matter.
But these products necessarily vary with the skill of the workman.
In another manufactory the following proportions are used:--Six stones,
of 14 lbs. each, of dry ground sulphate of soda, are mixed with 3 of
chalk and 3 of coal. This mixture, weighing 1-1/2 cwt., forms a batch,
which is spread upon the preparation shelf of the furnace (_figs._ 1037.
and 1038.), as above described, and gradually heated to incipient
ignition. It is then swept forwards to the lower area B, by the iron
oar, and spread evenly by the rake. Whenever it begins to soften under
the rising heat of the laboratory (the side doors being meanwhile shut),
the mass must be laboriously turned over and incorporated; the small
shovel, or paddle, being employed to transfer, by the interchange of
small portions at a time, in rapid but orderly succession, the whole
materials from the colder to the hotter, and from the hotter to the
colder parts of the hearth. The process of working one batch takes about
an hour, during the first half of which period it remains upon the
preparation shelf. The average weight of the finished ball is 1 cwt.,
and its contents in alkalimetrical soda are 33 pounds.
Where the acidulous sulphate of iron from pyrites may be had at a cheap
rate, it has been long ago employed, as at Hurlett in Scotland, instead
of sulphuric acid, for decomposing the chloride of sodium. Mr. Turner’s
process of preparing soda, by decomposing sea salt with litharge and
quicklime, has been long abandoned, the resulting patent yellow, or
sub-chloride of lead, having a very limited sale.
[Illustration: 1039]
2. _The extraction of pure soda from the crude article._--The black
balls must be broken into fragments, and thrown into large square iron
cisterns, furnished with false bottoms of wooden spars; when the
cisterns are nearly full of these lumps, water is pumped in upon them,
till they are all covered. After a few days, the lixiviation is
effected, and the lye is drawn off either by a syphon or by a plug-hole
near the bottom of the cistern, and run into evaporating vessels. These
may be of two kinds. The surface-evaporating furnace, shown in _fig._
1039., is a very admirable invention for economizing vessels, lime, and
fuel. The grate A, and fireplace, are separated from the evaporating
laboratory D, by a double fire-bridge B, C, having an interstitial space
in the middle, to arrest the communication of a melting or igniting heat
towards the lead-lined cistern D. This cistern may be 8, 10, or 20 feet
long, according to the magnitude of the soda-work, and 4 feet or more
wide. Its depth should be about 4 feet. It consists of sheet lead, of
about 6 pounds weight to the square foot, and it is lined with one layer
of bricks, set in roman or hydraulic cement, both along the bottom and
up the sides and ends. The lead comes up to the top of C, and the
liquor, or lye, may be filled in to nearly that height. Things being
thus arranged, a fire is kindled upon the grate A; the flame and hot air
sweep along the surface of the liquor, raise its temperature there
rapidly to the boiling point, and carry off the watery parts in vapour
up the chimney E, which should be 15 or 20 feet high, to command a good
draught. But, indeed, it will be most economical to build one high
capacious chimney stalk, as is now done at Glasgow, Manchester, and
Newcastle, and to lead the flues of the several furnaces above described
into it. In this evaporating furnace the heavier and stronger lye goes
to the bottom, as well as the impurities, where they remain undisturbed.
Whenever the liquor has attained to the density of 1·3, or thereby, it
is pumped up into evaporating cast-iron pans, of a flattened somewhat
hemispherical shape, and evaporated to dryness while being diligently
stirred with an iron rake and iron scraper.
This alkali gets partially carbonated by the above surface-evaporating
furnace, and is an excellent article.
When pure carbonate is wanted, that dry mass must be mixed with its own
bulk of ground coal, sawdust, or charcoal, and thrown into a
reverberatory furnace, like _fig._ 1038., but with the sole all upon one
level. Here it must be exposed to a heat not exceeding 650° or 700° F.;
that is, a little above the melting heat of lead; the only object being
to volatilize the sulphur present in the mass, and carbonate the alkali.
Now, it has been found, that if the heat be raised to distinct redness,
the sulphur will not go off, but will continue in intimate union with
the soda. This process is called calking, and the furnace is called a
calker furnace. It may be six or eight feet long, and four or five feet
broad in the hearth, and requires only one door in its side, with a
hanging iron frame filled with a fire-tile or bricks, as above
described.
This carbonating process may be performed upon several cwts. of the
impure soda, mixed with sawdust, at a time. It takes three or four hours
to finish the desulphuration; and it must be carefully turned over by
the oar and the rake, in order to burn the coal into carbonic acid, and
to present the carbonic acid to the particles of caustic soda diffused
through the mass, so that it may combine with them.
When the blue flames cease, and the saline matters become white, in the
midst of the coaly matter, the batch may be considered as completed. It
is raked out, and when cooled, lixiviated in great iron cisterns with
false bottoms, covered with mats. The watery solution being drawn off
clear by a plug-hole, is evaporated either to dryness, in hemispherical
cast-iron pans, as above described, or only to such a strength that it
shows a pellicle upon its surface, when it may be run off into
crystallizing cisterns of cast iron, or lead-lined wooden cisterns. The
above dry carbonate is the best article for the glass manufacture.
_Crystallized carbonate of soda_, contains 62-3/4 per cent. of water.
The crystals are colourless transparent rhomboids, which readily
effloresce in the air, and melt in their own water of crystallization.
On decanting the liquid from the fused mass, it is found that one part
of the salt has given up its water of crystallization to another. By
evaporation of that fluid, crystals containing one-fifth less water than
the common carbonate are obtained. These do not effloresce in the air.
_Mineral soda_, the sesquicarbonate, (_Anderthalb kohlensaures natron_,
Germ.); is found in the province of Sukena, in Africa, between Tripoli
and Fezzan. It forms a stratum no more than an inch thick, just below
the surface of the soil. Its texture is striated crystalline, like
fibrous gypsum. Several hundred tons of it are collected annually, which
are chiefly consumed in Africa. This species of soda does not effloresce
like the Egyptian, or the manufactured soda crystals, owing to its
peculiar state of composition and density. It was analyzed by Klaproth,
under its native name of _trona_, and was found to consist, in 100
parts, of--soda, 37; carbonic acid, 38; sulphate of soda, 2·5; water,
22·5, in 100.
This soda is, therefore, composed of--3 atoms of carbonic acid,
associated with 2 atoms of soda, and 4 of water; while our commercial
soda crystals are composed of--1 atom of carbonic acid, 1 atom of soda,
and 10 atoms of water.
There are six natron lakes in Egypt. They are situated in a barren
valley, called Bahr-bela-ma, about thirty miles to the west of the
Delta.
There are natron lakes also in Hungary, which afford in summer a white
saline efflorescent crust of carbonate of soda, mixed with a little
sulphate.
There are several soda lakes in Mexico, especially to the north of
Zacatecas, as also in many other provinces. In Columbia, 48 English
miles from Merida, mineral soda is extracted from the earth in great
abundance, under the name of _urao_.
_Bicarbonate of soda_ (_Doppelt kohlensaures natron_, Germ.); is
prepared, like bicarbonate of potassa, by transmitting carbonic acid gas
through a cold saturated solution of pure carbonate of soda, till
crystalline crusts be formed. The bicarbonate may also be obtained in
four-sided tables grouped together. It has an alkaline taste and
reaction upon litmus paper, dissolves in 13 parts of cold water, and is
converted by boiling water into the sesquicarbonate, with the
disengagement of one fourth of its carbonic acid. It consists of--37 of
soda, 52·35 carbonic acid, and 10·65 water.
SODA-WATER, is the name given to water containing a minute quantity of
soda, and highly charged with carbonic acid gas, whereby it acquires a
sparkling appearance, an agreeable pungent taste, an exhilarating
quality, and certain medicinal powers. It constitutes a considerable
object of manufacture in this kingdom. The following figure represents,
I understand, the best system of apparatus for preparing it. A very
dilute solution of soda is put into the globular vessel H, and the
carbonic acid gas is forced into it from the gasometer E, by means of
the powerful pump-work, as will be understood from the subjoined
explanation.
The same apparatus may serve for making any species of aerated water, in
imitation of any natural spring. All that is necessary for this purpose,
is to put into the cistern Q, the neutro-saline matter, earths, metallic
oxides, pure water, &c., each in due proportion, according to the most
accredited analysis of the mineral water to be imitated, to agitate that
mixture, to suck it into the condenser H, through the pipe R, and then
to impregnate it to the due degree, by pumping in the appropriate gas,
previously contained in the gasometer F.
Thus, to make Seltzer water, for each 12 pounds troy, = 69,120 grains,
or 1 gallon imperial very nearly, take 55 grains of dry carbonate of
soda, 17 of carbonate of lime, 18 of carbonate of magnesia, 3-1/2 of
subphosphate of alumina, 3 of chloride of potassium, 155 of chloride of
sodium, and 3 of finely precipitated silica. Put these materials into
the cistern Q, and charge the gasometer F with 353 cubic inches of
carbonic acid gas. Then work the machine by the handle of the wheel X,
as explained below, and regulate the introduction of the liquid and the
gas in aliquot portions; for example, if the condenser H admits half a
gallon of water at a time, that quantity of liquid should be charged
with 176 cubic inches of the gas, being one half of the whole quantity.
The sulphuretted mineral waters may be imitated in like manner, by
taking the proportions of their constituents, as given in Table II. of
WATERS, MINERAL.
IMPROVED SODA-WATER APPARATUS, AS MADE BY MR. HAYWARD TYLER, OF MILTON
STREET.
_Fig._ 1040. front view of the soda-water machine. _Fig._ 1041. end view
of the same.
[Illustration: 1040 1041]
A, lead generator, for making the gas. B, lead pot, for holding
sulphuric acid. C, handle for moving the agitator of the receiver, which
stirs up the ingredients in the lead generator. _a_, cap and screw, for
charging the lead pot with sulphuric acid. _b_, swivel-joint, which is
movable, for occasionally throwing in portions of sulphuric acid for
generating gas. _c_, stuffing-box for agitator. _d_, large cap and
screw, for charging the lead generator with whiting and water. _e_, cap
and screw, for emptying contents of ditto. D, lead pipe, to convey the
gas from the lead generator to gasometer. E, wood tub, filled with
water, for gasometer to work in. F, copper gasometer. G, strong iron
frame, for gasometer and tub to stand on, firmly fixed together by three
wrought-iron rods, _f_, _f_. _g_, _g_, two pulleys, for carrying rope
and counterbalance weight _h_, for balancing copper gasometer. _i_, cock
for discharging atmospheric air contained in the gasometer before making
the gas. _k_, cock for occasionally emptying the water out of the tub.
_l_, union joint, to which is fixed a copper pipe, passing through the
water in the tub, to deliver the gas as generated into the copper
gasometer. _m_, another union joint, with a similar copper pipe, passing
through the water in the tub, and projecting two or three inches above
the surface of the water, to convey the gas from the copper gasometer to
the soda-water machine. H, H, condenser for aerating the soda-water. I,
safety valve. K, K, bottling valve. L, bottling nipple. M, M, soda-water
pump. N, valve-piece. O, O, piston of the pump. P, pipe for conducting
gas from the gasometer to pump. Q, copper pan for holding the solution
of soda. R, copper pipe for conducting the solution of soda to the force
pump. S, S, two cocks for regulating the admission of the solution and
gas to the pump. T, copper pipe through which the soda-water is forced
to the condenser. U, pinion wheel, to give motion to the agitator
revolving inside the condenser. V, V, wheel for driving ditto. W, W,
cast-iron frame for carrying machinery. X, X, cast-iron fly-wheel. Z,
wrought-iron crank. Y, Z, Z, wood stools and curb, upon which the whole
of the machinery is fixed.
SODIUM, the metallic basis of soda, is obtained by processes similar to
those by which potassium is procured. By fusing hydrate of soda with a
little hydrate of potassa, a mixture is obtained, which yields more
readily than soda by itself to the decomposing action of iron-turnings
at a high heat, in a bent gun-barrel. The portion of potassium produced,
may be got rid of, by digesting the alloy for a few days in some naphtha
or oil of turpentine contained in an open vessel. The sodium remains at
the bottom of the liquid. Pure sodium may, however, be prepared at once,
by subjecting incinerated tartrate of soda to heat in the apparatus of
Brunner, described under POTASSIUM. It is white, like silver; softer and
more malleable than any other metal, and may be readily reduced into
very thin leaves. It preserves its malleability till it approaches the
melting point. Its specific gravity is 0·970. It softens at the
temperature of 122° F., and at 200° it is perfectly fluid; but it will
not rise in vapour until heated to nearly the melting point of glass. In
the air it oxidizes slowly, and gets covered with a crust of soda; but
it does not take fire till it is made nearly red-hot; and then it emits
brilliant scintillations. When thrown upon water, it is rapidly
oxidized, but without kindling, like potassium. If a drop of water be
thrown upon it, it becomes so hot by the chemical action as to take
fire. There are three oxides of sodium; 1. the suboxide; 2. the oxide,
or the basis of common soda; and, 3. the suroxide; the last being formed
when sodium is heated to redness upon a plate of silver.
SOLDERING (_Souder_, Fr.; _Löthen_, Germ.); is the process of uniting
the surfaces of metals, by the intervention of a more fusible metal,
which being melted upon each surface, serves, partly by chemical
attraction, and partly by cohesive force, to bind them together. The
metals thus united may be either the same or dissimilar; but the uniting
metal must always have an affinity for both. Solders must be, therefore,
selected in reference to their appropriate metals. Thus tin-plates are
soldered with an alloy consisting of from 1 to 2 parts of tin, with 1 of
lead; pewter is soldered with a more fusible alloy, containing a certain
proportion of bismuth added to the lead and tin; iron, copper, and brass
are soldered with spelter, an alloy of zinc and copper, in nearly equal
parts; silver, sometimes with pure tin, but generally with
silver-solder, an alloy consisting of 5 parts of silver, 6 of brass, and
2 of zinc; zinc and lead, with an alloy of from 1 to 2 parts of lead
with 1 of tin; platinum, with fine gold; gold, with an alloy of silver
and gold, or of copper and gold; &c.
In all soldering processes, the following conditions must be observed:
1. the surfaces to be united must be entirely free from oxide, bright,
smooth, and level; 2. the contact of air must be excluded during the
soldering, because it is apt to oxidize one or other of the surfaces,
and thus to prevent the formation of an alloy at the points of union.
This exclusion of air is effected in various ways. The locksmith encases
in loam the objects of iron, or brass, that he wishes to subject to a
soldering heat; the silversmith and brazier mix their respective solders
with moistened borax powder; the coppersmith and tinman apply sal
ammoniac, rosin, or both, to the cleaned metallic surfaces, before using
the soldering-iron to fuse them together with the tin alloy. The strong
solder of the coppersmith consists of 8 parts of brass and 1 of zinc;
the latter being added to the former, previously brought into a state of
fusion. The crucible must be immediately covered up for two minutes till
the combination be completed. The melted alloy is to be then poured out
upon a bundle of twigs held over a tub of water, into which it falls in
granulations. An alloy of 3 parts of copper and 1 of zinc forms a still
stronger solder for the coppersmiths. When several parts are to be
soldered successively upon the same piece, the more fusible alloys,
containing more zinc, should be used first. A softer solder for
coppersmiths is made with 6 parts of brass, 1 of tin, and 1 of zinc; the
tin being first added to the melted brass, then the zinc; and the whole
well incorporated by stirring.
The edges of sheet lead for sulphuric acid chambers, and its
concentration pans, are joined together by melted lead itself, because
any solder containing tin would soon be corroded. With this view, the
two edges being placed in contact, are flattened down into a long wooden
groove, and secured in their situation by a few brass pins driven into
the wood. The surfaces are next brightened with a triangular scraper,
rubbed over with candle grease, and then covered with a stream of hot
melted lead. The riband of lead thus applied is finally equalized by
being brought into partial fusion with the plumber’s conical iron heated
to redness; the contact of air being prevented by sprinkling rosin over
the surface. The sheets of lead are thus _burned_ together, in the
language of the workmen.
SOOT (_Noir de fumée_, _Suie_, Fr.; _Rus_, _Flatterrus_, Germ.); is the
pulverulent charcoal condensed from the smoke of wood or coal fuel. A
watery infusion of the former is said to be antiseptic, probably from
its containing some creosote.
The soot of pitcoal has not been analyzed with any minuteness. It
contains some sulphate and carbonate of ammonia, along with bituminous
matter.
SORBIC ACID, is the same with malic acid; which see.
SOY, is a liquid condiment, or sauce, imported chiefly from China. It is
prepared with a species of white haricots, wheat flour, common salt, and
water; in the proportions respectively of 50, 60, 50, and 250 pounds.
The haricots are washed, and boiled in water till they become so soft as
to yield to the fingers. They are then laid in a flat dish to cool, and
kneaded along with the flour, a little of the hot water of the decoction
being added from time to time. This dough is next spread an inch or an
inch and a half thick upon the flat vessel (made of thin staves of
bamboo), and when it becomes hot and mouldy, in two or three days, the
cover is raised upon bits of stick, to give free access of air. If a
rancid odour is exhaled, and the mass grows green, the process goes on
well; but if it grows black, it must be more freely exposed to the air.
As soon as all the surface is covered with green mouldiness, which
usually happens in eight or ten days, the cover is removed, and the
matter is placed in the sunshine for several days. When it has become as
hard as a stone, it is cut into small fragments, thrown into an earthen
vessel, and covered with the 250 pounds of water having the salt
dissolved in it. The whole is stirred together, and the height at which
the water stands is noted. The vessel being placed in the sun, its
contents are stirred up every morning and evening; and a cover is
applied at night, to keep it warm and exclude rain. The more powerful
the sun, the sooner the soy will be completed; but it generally requires
two or three of the hottest summer months. As the mass diminishes by
evaporation, well water is added; and the digestion is continued till
the salt water has dissolved the whole of the flour and the haricots;
after which the vessel is left in the sun for a few days, as the good
quality of the soy depends on the completeness of the solution, which is
promoted by regular stirring. When it has at length assumed an oily
appearance, it is poured into bags, and strained. The clear black liquid
is the soy, ready for use. It is not boiled, but is put up into bottles,
which must be carefully corked. Genuine soy was made in this way at
Canton, by Michael de Grubbens. See _Memoirs of Academy of Sciences of
Stockholm_ for 1803.
SPECIFIC GRAVITY, designates the relative weights of different bodies
under the same bulk; thus a cubic foot of water weighs 1000 ounces
avoirdupois; a cubic foot of coal, 1350; a cubic foot of cast iron,
7280; a cubic foot of silver, 10,400; and a cubic foot of pure gold,
19,200; numbers which represent the specific gravities of the respective
substances, compared to water = 1·000. See ALLOY.
SPECULUM METAL, is an alloy of copper and tin; described under COPPER.
SPERMACETI; the _Cetine_ of Chevreul. In certain species of the
_cachalot_ whale, as the _Physeter macrocephalus_, _tursio_, _microps_,
and _orthodon_, as also the _Delphinus edentulus_, the fat of some parts
of their bodies contains a peculiar kind of stearine, called spermaceti.
The oil obtained from cavities in the bones of the cranium of the above
cetaceæ is the richest in this kind of stearine. This being thrown into
great filter-bags, the spermaceti oil passes through, and is
subsequently purified by the addition of a small quantity of potash lye,
which precipitates certain matters by neutralizing the acid that held
them in solution. The solid which remains on the filter is next squeezed
in bags, by means of a horizontal hydraulic press encased in steam, then
digested with a weak potash lye, in order to dissolve out any oil which
may continue to adhere to it, washed with water, finally dissolved in a
tub by the agency of steam, laded into tin pans, and allowed slowly to
concrete into a white semi-transparent brittle lamellar crystalline
mass, which forms elegant candles.
At 60° its specific gravity is 0·943. It melts at 112·5°; 100 parts of
alcohol at 0·821 dissolve 3-1/2 of it, of which 0·9 are deposited on
cooling. Warm ether dissolves it in very large quantities. It is soluble
also in the fat of volatile oils; and if the solutions have been
saturated while hot, the greater part of the spermaceti crystallizes on
cooling. When this substance has been purified by digesting alcohol upon
it repeatedly, what remains is the _cetine_ of Chevreul, or pure
spermaceti. Its melting point has now become 116° F., and its boiling
point 616° F., at which it distils without alteration. Caustic alkaline
lyes saponify it with difficulty.
SPIRIT OF AMMONIA, is, properly speaking, alcohol combined with ammonia
gas; but the term is often applied to water of ammonia.
SPIRITS, VINOUS. This subject has been fully discussed in the articles
ALCOHOL, DISTILLATION, and FERMENTATION. I have shown that the
progressive increase of alcohol in the wash tends progressively to
prevent the conversion of the wort into spirit, or checks the fermenting
process, though a great deal of fermentable matter remains unchanged.
Mr. Sheridan has sought to remove this obstacle to the thorough
transmutation of saccharine matter into alcohol, by drawing off the
spirit as it is formed. For this purpose he ferments his wash in close
tuns, connected with a powerful air-pump worked by machinery, thus
continually removing the carbonic acid as it is formed, and maintaining
a diminished pressure under which the alcohol readily distils at a
temperature of 120° or 130° F. He finds that this degree of heat is not
injurious to the fermentation, provided that it be communicated by the
air of a stove-room, and not by water or steam pipes traversing the
liquid, which would inevitably scald or seeth the particles in
succession, and thereby extinguish the fermenting principle.
By the above ingenious plan, Mr. Sheridan tells me he has obtained 28
gallons of proof spirit from a quarter of grain, instead of the average
product 21, being an increase of 25 per cent. The experiment was tried
upon a considerable scale at Messrs. Currie’s great distillery near
London; but could not be established as a mode of manufacture, on
account of the excise laws, which prohibit the distillers from carrying
on the two processes of fermentation and distillation at the same time.
SPIRIT OF WINE; Alcohol.
SPONGE (_Eponge_, Fr.; _Schwamm_, Germ.); is a cellular fibrous tissue
produced by small animals, almost imperceptible, called polypi by
naturalists, which live in the sea. This tissue is said to be covered in
its recent state with a kind of semi-fluid thin coat of animal jelly,
susceptible of a slight contraction or trembling on being touched; which
is the only symptom of vitality displayed by the sponge. After death,
this jelly disappears, and leaves merely the sponge; formed by the
combination of a multitude of small capillary tubes, capable of
receiving water in their interior, and of becoming thereby distended.
Sponges occur attached to stones at the bottom of the sea; and abound
particularly upon the shores of the islands in the Grecian Archipelago.
Although analogous in their origin to coral, sponges are quite different
in their nature; the former being composed almost entirely of carbonate
of lime; while the latter are formed of the same elements as animal
matters, and afford, on distillation, a considerable quantity of
ammonia.
Dilute sulphuric acid has been recommended for bleaching sponges, after
the calcareous impurities have been removed by muriatic acid. Chlorine
water answers better.
SPOON MANUFACTURE. See STAMPING OF METALS.
STAINED GLASS. When certain metallic oxides or chlorides, ground up with
proper fluxes, are painted upon glass, their colours fuse into its
surface at a moderate heat, and make durable pictures, which are
frequently employed in ornamenting the windows of churches as well as of
other public and private buildings. The colours of stained glass are all
transparent, and are therefore to be viewed only by transmitted light.
Many metallic pigments, which afford a fine effect when applied cold on
canvas or paper, are so changed by vitreous fusion as to be quite
inapplicable to painting in stained glass.
The glass proper for receiving these vitrifying pigments, should be
colourless, uniform, and difficult of fusion; for which reason crown
glass, made with little alkali, or with kelp, is preferred. When the
design is too large to be contained on a single pane, several are fitted
together, and fixed in a bed of soft cement while painting, and then
taken asunder to be separately subjected to the fire. In arranging the
glass pieces, care must be taken to distribute the joinings so that the
lead frame-work may interfere as little as possible with the effect.
A design must be drawn upon paper, and placed beneath the plate of
glass; though the artist cannot regulate his tints directly by his
pallet, but by specimens of the colours producible from his pallet
pigments after they are fired. The upper side of the glass being sponged
over with gum-water, affords, when dry, a surface proper for receiving
the colours, without the risk of their running irregularly, as they
would be apt to do, on the slippery glass. The artist first draws on the
plate, with a fine pencil, all the traces which mark the great outlines
and shades of the figures. This is usually done in black, or, at least,
some strong colour, such as brown, blue, green, or red. In laying on
these, the painter is guided by the same principles as the engraver,
when he produces the effect of light and shade by dots, lines, or
hatches; and he employs that colour to produce the shades, which will
harmonize best with the colour which is to be afterwards applied; but
for the deeper shades, black is in general used. When this is finished,
the whole picture will be represented in lines or hatches similar to an
engraving finished up to the highest effect possible; and afterwards,
when it is dry, the vitrifying colours are laid on by means of larger
hair pencils; their selection being regulated by the burnt specimen
tints. When he finds it necessary to lay two colours adjoining, which
are apt to run together in the kiln, he must apply one of them to the
back of the glass. But the few principal colours to be presently
mentioned, are all fast colours, which do not run, except the yellow,
which must therefore be laid on the opposite side. After colouring, the
artist proceeds to bring out the lighter effects by taking off the
colour in the proper place, with a goose quill cut like a pen without a
slit. By working this upon the glass, he removes the colour from the
parts where the lights should be the strongest; such as the hair, eyes,
the reflection of bright surfaces and light parts of draperies. The
blank pen may be employed either to make the lights by lines, or hatches
and dots, as is most suitable to the subject.
By the metallic preparations now laid upon it, the glass is made ready
for being fired, in order to fix and bring out the proper colours. The
furnace or kiln best adapted for this purpose, is similar to that used
by enamellers. See ENAMEL, and the _Glaze-kiln_; under POTTERY. It
consists of a muffle or arch of fire-clay or pottery, so set over a
fireplace, and so surrounded by flues, as to receive a very considerable
heat within, in the most equable and regular manner; otherwise some
parts of the glass will be melted; while, on others, the superficial
film of colours will remain unvitrified. The mouth of the muffle, and
the entry for introducing fuel to the fire, should be on opposite sides,
to prevent as much as possible the admission of dust into the muffle,
whose mouth should be closed with double folding-doors of iron,
furnished with small peep-holes, to allow the artist to watch the
progress of the staining, and to withdraw small trial slips of glass,
painted with the principal tints used in the picture.
The muffle must be made of very refractory fire-clay, flat at its
bottom, and only 5 or 6 inches high, with such an arched top as may make
the roof strong, and so close on all sides as to exclude entirely the
smoke and flame. On the bottom of the muffle a smooth bed of sifted
lime, freed from water, about half an inch thick, must be prepared for
receiving the pane of glass. Sometimes several plates of glass are laid
over each other with a layer of dry pulverulent lime between each. The
fire is now lighted, and most gradually raised, lest the glass should be
broken; and after it has attained to its full heat, it must be kept up
for 3 or 4 hours, more or less, according to the indications of the
trial slips; the yellow colour being principally watched, as it is found
to be the best criterion of the state of the others. When the colours
are properly burnt in, the fire is suffered to die away, so as to anneal
the glass.