The manufacture of sugar from the juice of a species of maple tree,
which grow spontaneously in many of the uncultivated parts of North
America, appears to have been first attempted about 1752, by some of the
farmers of New England, as a branch of rural economy.
The sugar maple, the _Acer saccharinum_ of Linnæus, thrives especially
in the states of New York and Pennsylvania, and yields a larger
proportion of sugar than that which grows upon the Ohio. It is found
sometimes in thickets which cover five or six acres of land; but it is
more usually interspersed among other trees. They are supposed to arrive
at perfection in forty years.
The extraction of maple sugar is a great resource to the inhabitants of
districts far removed from the sea; and the process is very simple.
After selecting a spot among surrounding maple trees, a shed is erected,
called the _sugar-camp_, to protect the boilers and the operators from
the vicissitudes of the weather. One or more augers, three-fourths of an
inch in diameter; small troughs for receiving the sap; tubes of elder or
sumach, 8 or 10 inches long, laid open through two-thirds of their
length, and corresponding in size to the auger-bits; pails for emptying
the troughs, and carrying the sap to the camp; boilers capable of
holding 15 or 16 gallons; moulds for receiving the syrup inspissated to
the proper consistence for concreting into a loaf of sugar; and,
lastly, hatchets to cut and cleave the fuel, are the principal utensils
requisite for this manufacture. The whole of February and beginning of
March are the sugar season.
The trees are bored obliquely from below upwards, at 18 or 20 inches
above the ground, with two holes 4 or 5 inches asunder. Care must be
taken that the auger penetrates no more than half an inch into the
alburnum, or white bark; as experience has proved that a greater
discharge of sap takes place at this depth than at any other. It is also
advisable to perforate in the south face of the trunk.
The trough, which contains from two to three gallons, and is made
commonly of white pine, is set on the ground at the foot of each tree,
to receive the sap which flows through the two tubes inserted into the
holes made with the auger; it is collected together daily, and carried
to the camp, where it is poured into casks, out of which the boilers are
supplied. In every case, it ought to be boiled within the course of two
or three days from flowing out of the tree, as it is liable to run
quickly into fermentation, if the weather become mild. The evaporation
is urged by an active fire, with careful skimming during the boiling;
and the pot is continually replenished with more sap, till a large body
has at length assumed a syrupy consistence. It is then allowed to cool,
and passed through a woollen cloth, to free it from impurities.
The syrup is transferred into a boiler to three-fourths of its capacity,
and it is urged with a brisk fire, till it acquires the requisite
consistence for being poured into the moulds or troughs prepared to
receive it. This point is ascertained, as usual, by its exhibiting a
granular aspect, when a few drops are drawn out into a thread between
the finger and the thumb. If in the course of the last boiling, the
liquor froth up considerably, a small bit of butter or fat is thrown
into it. After the molasses have been drained from the concreted loaves,
the sugar is not at all deliquescent, like equally brown sugar from the
cane. Maple sugar is in taste equally agreeable with cane sugar, and it
sweetens as well. When refined, it is equally fair with the loaf sugar
of Europe.
The period during which the trees discharge their juices is limited to
about six weeks. Towards the end of the flow, it is less abundant, less
saccharine, and more difficult to be crystallized.
QUANTITY of SUGAR brought into the Markets of the World, in the year
1838.
Tons.
British West Indies 160,000
Mauritius, 35,000; and British East Indies, 20,000 55,000
Java 36,000
Manilla and Siam 30,000
Dutch West Indies 25,000
St. Thomas and St. Croix 7,000
Martinique and Guadaloupe 80,000
Bourbon 20,000
Cuba 100,000
Brazils 95,000
From Beet-root, in France and Belgium 65,000
United States 65,000
-------
738,000[65]
[65] For this important table, I am indebted to James Cook, Esq., of
Mincing-lane.
SUGAR OF LEAD, properly _Acetate of lead_, (_Acetate de plomb_; _Sel de
Saturne_, Fr.; _Essigsaures Bleioxyd_, _Bleizucker_, Germ.) is prepared
by dissolving pure litharge, with heat, in strong vinegar, made of malt,
wood, or wine, till the acid be saturated. A copper boiler, rendered
negatively electrical by soldering a strap of lead within it, is the
best adapted to this process on the great scale. 325 parts of finely
ground and sifted oxide of lead, require 575 parts of strong acetic
acid, of spec. grav. 7° Baumé, for neutralization, and afford 960 parts
of crystallized sugar of lead. The oxide should be gradually sprinkled
into the moderately hot vinegar, with constant stirring, to prevent
adhesion to the bottom; and when the proper quantity is dissolved, the
solution may be weakened with some of the washings of a preceding
process, to dilute the acetate, after which the whole should be heated
to the boiling point, and allowed to cool slowly, in order to settle.
The limpid solution is to be drawn off by a syphon, concentrated by
boiling to the density of 32° B., taking care that there be always a
faint excess of acid, to prevent the possibility of any basic salt being
formed, which would interfere with the formation of regular crystals.
Should the concentrated liquor be coloured, it may be whitened by
filtration through granular bone black.
Stoneware vessels, with salt glaze, answer best for crystallizers. Their
edges should be smeared with candle-grease, to prevent the salt creeping
over them by _efflorescent vegetation_. The crystals are to be drained,
and dried in a stove-room very slightly heated. It deserves remark, that
linen, mats, wood, and paper, imbued with sugar of lead, and strongly
dried, readily take fire, and burn away like tinder. When the
motherwaters cease to afford good crystals, they should be decomposed by
carbonate of soda, or by lime skilfully applied, when a carbonate or an
oxide will be obtained, fit for treating with fresh vinegar. The
supernatant acetate of soda may be employed for the extraction of pure
acetic acid.
A main point in the preparation of sugar of lead, is to use a strong
acid; otherwise much time and acid are wasted in concentrating the
solution. This salt crystallizes in colourless, transparent, four and
six sided prisms, from a moderately concentrated solution; but from a
stronger solution, in small needles, which have a yellow cast if the
acid has been slightly impure. It has no smell, a sweetish astringent
metallic taste, a specific gravity of 2·345; it is permanent in the air
at ordinary temperatures, but effloresces when heated to 95°, with the
loss of its water of crystallization and some acid, falling into a
powder, which passes, in the air, slowly into carbonate of lead. The
crystals dissolve in 1-1/2 times their weight of water at 60°, but in
much less of boiling water, and in 8 parts of alcohol. The solution
feebly reddens litmus paper, but has an alkaline reaction upon the
colours of violets and turmeric. The constituents of the salt are, 58·71
oxide of lead, 27·08 acetic acid, and 14·21 water, in 100.
Acetate of lead is much used in calico-printing. It is poisonous, and
ought to be prepared and handled with attention to this circumstance.
There are two subacetates of lead; the first of which, the
ter-subacetate, has three atoms of base to one of acid, and is the
substance long known by the name of Goulard’s extract. It may be
obtained by digesting with heat a solution of the neutral acetate, upon
pure litharge or massicot. The solution affords white crystalline
scales, which do not taste so sweet as sugar of lead, dissolve in not
less than 30 parts of water, are insoluble in alcohol, and have a
decided alkaline reaction upon test paper. Carbonic acid, transmitted
through the solution, precipitates the excess of the oxide of lead, in
the state of a carbonate, a process long ago prescribed by Thenard for
making white-lead. This subacetate consists of 88·66 of oxide, and 13·34
acid, in 100 parts. It is employed for making the orange sub-chromate of
lead, as also sometimes in surgery.
A _sex-subacetate_, containing six atoms of base, may be obtained by
adding ammonia in excess to a solution of the preceding salt, and
washing the precipitate with dilute water of ammonia. A white powder is
thus formed, that dissolves sparingly in cold water, but gives a
solution in boiling water, from which white silky needles are deposited.
It consists of 92·86 oxide, and 7·14 acid.
SULPHATES, are saline compounds of sulphuric acid with oxidized bases.
The minutest quantity of them present in any solution, may be detected
by the precipitate, insoluble in nitric or muriatic acid, which they
afford with nitrate or muriate of baryta. They are mostly insoluble in
alcohol.
SULPHATE OF ALUMINA AND POTASSA, is alum.
SULPHATE OF AMMONIA, is a salt sometimes formed by saturating the
ammonia liquor of the gas-works with sulphuric acid; and it is employed
for making carbonate of ammonia. See AMMONIA and SAL AMMONIAC.
SULPHATE OF BARYTA, is the mineral called heavy-spar, which frequently
forms the gangue or vein-stone of lead and other metallic ores.
SULPHATE OF COPPER, _Roman or Blue Vitriol_ (_Vitriol de Chypre_, Fr.;
_Kupfervitriol_, Germ.); is a salt composed of sulphuric acid and oxide
of copper, and may be formed by boiling the concentrated acid upon the
metal, in an iron pot. It is, however, a natural product of many copper
mines, from which it flows out in the form of a blue water, being the
result of the infiltration of water over copper pyrites, which has
become oxygenated by long exposure to the air in subterranean
excavations. The liquid is concentrated by heat in copper vessels, then
set aside to crystallize. The salt forms in oblique four-sided tables,
of a fine blue colour; has a spec. gravity of 2·104; an acerb,
disagreeable, metallic taste; and, when swallowed, it causes violent
vomiting. It becomes of a pale dirty blue, and effloresces slightly, on
long exposure to the air; when moderately heated, it loses 36 per cent.
of water, and falls into a white powder. It dissolves in 4 parts of
water, at 60°, and in 2 of boiling water, but not in alcohol; the
solution has an acid reaction upon litmus paper. When strongly ignited,
the acid flies off, and the black oxide of copper remains. The
constituents of crystallized sulphate of copper are--oxide, 31·80; acid,
32·14; and water, 36·06. Its chief employment in this country is in
dyeing, and for preparing certain green pigments. See SCHEELE’S and
SCHWEINFURTH GREEN. In France, the farmers sprinkle a weak solution of
it upon their grains and seeds before sowing them, to prevent their
being attacked by birds and insects.
SULPHATE OF IRON, _Green vitriol_, _Copperas_ (_Couperose verte_, Fr.;
_Eisenvitriol_, _Schwefelsaures Eisenoxydul_, Germ.); is a crystalline
compound of sulphuric acid and protoxide of iron; hence called, by
chemists, the protosulphate; consisting of, 26·10 of base, 29·90 of
acid, and 44·00 of water, in 100 parts; or of 1 prime equivalent of
protoxide, 36, + 1 of acid, 40, + 7 of water, 63, = 139. It may be
prepared by dissolving iron to saturation in dilute sulphuric acid,
evaporating the solution till a pellicle forms upon its surface, and
setting it aside to crystallize. The copperas of commerce is made in a
much cheaper way, by stratifying the pyrites found in the coal measures
(_Vitriolkies_ and _Strahlkies_ of the Germans), upon a sloping puddled
platform of stone, leaving the sulphuret exposed to the weather, till,
by the absorption of oxygen, it effloresces, lixiviating with water the
supersulphate of iron thus formed, saturating the excess of acid with
plates of old iron, then evaporating and crystallizing. The other
pyrites, which occurs often crystallized, called by the Germans
_Schwefelkies_ or _Eisenkies_, must be deprived of a part of its sulphur
by calcination, before it acquires the property of absorbing oxygen from
the atmosphere, and thereby passing from a bisulphuret into a
bisulphate. Alum schist very commonly contains vitriolkies, and affords,
after being roasted and weather-worn, a considerable quantity of
copperas, which must be carefully separated by crystallization from the
alum.
This liquor used formerly to be concentrated directly in leaden vessels;
but the first stage of the operation is now carried on in stone canals
of considerable length, vaulted over with bricks, into which the liquor
is admitted, and subjected at the surface to the action of flame and
heated air, from a furnace of the reverberatory kind, constructed at one
end, and discharging its smoke by a high chimney raised at the other.
See SODA MANUFACTURE. Into this oblong trough, resting on dense clay,
and rendered tight in the joints by water-cement, old iron is mixed with
the liquor, to neutralize the excess of acid generated from the pyrites,
as also to correct the tendency to superoxidizement in copperas, which
would injure the fine green colour of the crystals. After due
concentration and saturation in this surface evaporator, the solution is
run off into leaden boilers, where it is brought to the proper density
for affording regular crystals, which it does by slow cooling, in stone
cisterns.
Copperas forms sea-green, transparent, rhomboidal prisms, which are
without smell, but have an astringent, acerb, inky taste; they speedily
become yellowish-brown in the air, by peroxidizement of the iron, and
effloresce in a warm atmosphere: they dissolve in 1·43 parts of water at
60°, in 0·27 at 190°, and in their own water of crystallization at a
higher heat. This salt is extensively used in dyeing black, especially
hats, in making ink and prussian blue, for reducing indigo in the blue
vat, in the China blue dye, for making the German oil of vitriol, and in
many chemical and medicinal preparations.
There is a persulphate and subpersulphate of iron, but they belong to
the domain of chemistry. The first may be formed, either by dissolving
with heat one part of red oxide of iron (colcothar) in one-and-a-half of
concentrated sulphuric acid, or by adding some nitric acid to a
boiling-hot solution of copperas. It forms with galls and logwood a very
black ink, which is apt to become brown-black. When evaporated to
dryness, it appears as a dirty white pulverulent substance, which is
soluble in alcohol. It consists, in 100 parts, of 39·42 of red oxide of
iron, and 60·58 sulphuric acid.
Hydrated peroxide of iron, prepared by precipitation with alkali from
solution of the persulphate, is an excellent antidote against poisoning
by arsenic. A French _peruquier_, who had swallowed two drams of
arsenious acid, was, after an interval of twenty minutes, treated with
the oxide precipitated from 6 ounces of that salt by caustic potash. It
was diffused in 20 quarts of weak syrup, and administered in successive
doses. After repeated vomiting and purging, the patient felt no more
pain, and was pronounced by the physician to be quite convalescent.
In the copperas and alum works, a very large quantity of ochrey sediment
is obtained; which is a peroxide of iron, containing a little sulphuric
acid and alumina. This deposit, calcined in reverberatory hearths,
becomes of a bright-red colour; and when ground and elutriated, in the
same way as is described under _white lead_, forms a cheap pigment, in
very considerable demand, called _English red_, in the French market.
Colcothar of Vitriol, and Crocus of Mars, are old names for red oxide of
iron. This brown-red powder is obtained in its purest state, by
calcining dried sulphate of iron in a furnace till all its acid be
expelled, and its base become peroxidized. It must be levigated,
elutriated, and dried. This powder is employed extensively in the steel
manufacture, for giving the finishing lustre to fine articles; it is
used by silversmiths under the name of plate powder and _rouge_; and by
the opticians for polishing the specula of reflecting telescopes. Much
of the _crocus_ in the market, is made, however, from the copperas and
alum sediments, and is greatly inferior to the article prepared by the
last process. The finest _rouge_ is made by precipitating the oxide with
soda, then washing and calcining the powder.
An excellent powder for applying to razor-strops, is made by igniting
together in a crucible equal parts of well-dried copperas and sea salt.
The heat must be slowly raised and well regulated, otherwise the
materials will boil over in a pasty state, and the product will be in a
great measure lost. When well made, out of contact of air, it has the
brilliant aspect of plumbago. It has a satiny feel, and is a true _fer
olegiste_, similar in composition to the Elba iron ore. It requires to
be ground and elutriated; after which it affords, on drying, an
impalpable powder, that may be either rubbed on a strop of smooth buff
leather, or mixed up with hog’s-lard or tallow into a stiff cerate.
SULPHATE OF LIME. See GYPSUM.
SULPHATE OF MAGNESIA, _Epsom Salt_ (_Sel amer_, Fr.; _Bittersalz_,
Germ.); exists in sea-water, as also in the waters of Saidschütz,
Sedlitz, and Püllna; and in many saline springs, besides Epsom in
Surrey, whence it has derived its trivial name, and from which it was
first extracted, in the year 1695, and continued to be so, till modern
chemistry pointed out cheaper and more abundant sources of this useful
purgative salt. The sulphate of magnesia, occasionally found effloresced
on the surface of minerals in crystalline filaments, was called
_haarsalz_ (hair salt) by the older writers. The bittern of the Scotch
sea-salt works is muriate of magnesia, mixed, with a little sulphate of
magnesia and chloride of sodium. If the proper decomposing quantity
(found by trial) of sulphate of soda be added to it, and the mixed
solution be evaporated at the temperature of 122° F., chloride of sodium
will form by double affinity, and fall down in cubical crystals; while
the solution of sulphate of magnesia which remains, being evaporated to
the proper point, will afford regular crystals in four-sided prisms with
four-sided acuminations. Or, if bittern be treated in a retort with the
equivalent quantity of sulphuric acid, the muriatic acid may be
distilled off into a series of Woulfe’s bottles, and the sulphate of
magnesia, soda, and lime, will remain in the retort, from which mixture
the sulphate of magnesia may be separated by filtration and
crystallization.
Magnesian limestone being digested with as much muriatic acid as will
dissolve out its lime only, will, after washing, afford, with the
equivalent quantity of sulphuric acid, a pure sulphate of magnesia; and
this is certainly the simplest and most profitable process for
manufacturing this salt upon the great scale. Many prepare it directly,
by digesting upon magnesian limestone the equivalent saturating quantity
of dilute sulphuric acid. The sulphate of lime being separated by
subsidence, the supernatant solution of sulphate of magnesia is
evaporated and crystallized.
This salt is composed of, magnesia 16·72, sulphuric acid 32·39, and
water 50·89. When free from muriate, it tends to effloresce in the air.
It dissolves in 4 parts of water at 32°, in 3 parts at 60°, in 1·4 at
200°, and in its own water of crystallization at a higher heat.
SULPHATE OF MANGANESE, is prepared on the great scale for the
calico-printers, by exposing the peroxide of the metal and pitcoal
ground together, and made into a paste with sulphuric acid, to a heat of
400° F. On lixiviating the calcined mass, a solution of the salt is
obtained, which is to be evaporated and crystallized. It forms pale
amethyst-coloured prisms, which have an astringent bitter taste,
dissolve in 2-1/2 parts of water, and consist of, protoxide of manganese
31·93, sulphuric acid 35·87, and water 32·20, in 100 parts.
SULPHATE OF MERCURY, is a white salt which is used in making corrosive
sublimate. See MERCURY. The subsulphate, called _Turbith Mineral_, is a
pale yellow pigment, and may be prepared by washing the white sulphated
peroxide with hot water, which resolves it into the soluble
supersulphate, and the insoluble subsulphate, or _Turbith_. It is
poisonous.
SULPHATE OF POTASSA, is obtained by first igniting and then
crystallizing the residuum of the distillation of nitric acid from
nitre.
SULPHATE OF SODA, is commonly called Glauber’s salt, from the name of
the chemist who first prepared it. It is obtained by igniting and then
crystallizing the residuum of the distillation of muriatic acid from
common salt. It crystallizes in channelled 6-sided prisms. See SODA
MANUFACTURE.
SULPHATE OF ZINC, called also _White Vitriol_, is commonly prepared in
the Harz, by washing the calcined and effloresced sulphuret of zinc or
blende, on the same principle as green and blue vitriol are obtained
from the sulphurets of iron and copper. Pure sulphate of zinc may be
made most readily by dissolving the metal in dilute sulphuric acid,
evaporating and crystallizing the solution. It forms prismatic crystals,
which have an astringent, disagreeable, metallic taste; they effloresce
in a dry air, dissolve in 2·3 parts of water at 60°, and consist
of--oxide of zinc, 28·29; acid, 28·18; water, 43·53. Sulphate of zinc is
used for preparing drying oils for varnishes, and in the reserve or
resist pastes of the calico-printer.
SULPHITES, are a class of salts, consisting of sulphurous acid, combined
in equivalent proportions with the oxidized bases.
SULPHOSELS, is the name given by Berzelius to a class of salts which may
be prepared as follows:--1. Dissolve a salt consisting of an oxide and
an acid (an _oxisalt_), in a very small quantity of water, and pass
through the solution a stream of sulphuretted hydrogen, till the salt be
entirely decomposed. In this operation, the _oxisalt_ is transformed
into a _sulphosalt_, by the sulphur of the compound gas; while its
hydrogen forms water with the oxygen of the saline base. This process is
applicable only to the metallic salts; and among these, not to the
nitrates, carbonates, or phosphates. 2. Another method of preparing
_sulphosalts_ is, to add to a watery solution of sulphuret of
potassium, an electro-negative metallic sulphuret, which will dissolve
in the liquid till the sulphuret of potassium be saturated. This saline
compound is to be employed to effect double decompositions with the
oxisalts; that is, to convert the radical of another base, combined with
an _oxacid_, into a sulphosalt. 3. If the electro-negative sulphuret be
put in powder into a solution of the hydrosulphuret of potassa, it will
dissolve and expel the sulphuretted hydrogen with effervescence; just as
carbonic acid is displaced by a stronger acid. For his other three
methods of preparing _sulphosalts_, see his _Elements_, vol. iii. p.
336, Fr. translation.
SULPHUR; _Brimstone_ (_Soufre_, Fr.; _Schwefel_, Germ.); is a simple
combustible, solid, non-metallic, of a peculiar yellow colour, very
brittle, melting at the temperature of 226° Fahr., and possessing, after
it has been fused, a specific gravity of 1·99. When held in a warm hand,
a roll of sulphur emits a crackling sound, by the fracture of its
interior parts; and when it is rubbed, it emits a peculiar well-known
smell, and acquires at the same time negative electricity. When heated
to the temperature of 560° F. it takes fire, burns away with a dull blue
flame of a suffocating odour, and leaves no residuum. When more strongly
heated, sulphur burns with a vivid white flame. It is not affected by
air or water.
Sulphur is an abundant product of nature; existing sometimes pure or
merely mixed, and at others in intimate chemical combination with
oxygen, and various metals, forming sulphates and sulphurets. See Ores
of COPPER, IRON, LEAD, &c., under these metals.
[Illustration: 1100]
_Fig._ 1100. represents one of the cast-iron retorts used at Marseilles
for refining sulphur, wherein it is melted and converted into vapours,
which are led into a large chamber for condensation. The body _a_, of
the retort is an iron pot, 3 feet in diameter outside, 22 inches deep,
half an inch thick, which weighs 14 cwt., and receives a charge of 8
cwt. of crude sulphur. The grate is 8 inches under its bottom, whence
the flame rises and plays round its sides. A cast-iron capital _b_,
being luted to the pot, and covered with sand, the opening in front is
shut with an iron plate. The chamber _d_, is 23 feet long, 11 feet wide,
and 13 feet high, with walls 32 inches thick. In the roof, at each
gable, valves or flap-doors, _e_, 10 inches square, are placed at the
bottom of the chimney _c_. The cords for opening the valves are led down
to the side of the furnace. The entrance to the chamber is shut with an
iron door. In the wall opposite to the retorts, there are two apertures
near the floor, for taking out the sulphur. Each of the two retorts
belonging to a chamber is charged with 7-1/2 or 8 cwts. of sulphur; but
one is fired first, and with a gentle heat, lest the brimstone froth
should overflow; but when the fumes begin to rise copiously, with a
stronger flame. The distillation commences within an hour of kindling
the fire, and is completed in six hours. Three hours after putting fire
to the first retort, the second is in like manner set in operation.
When the process of distillation is resumed, after having been some time
suspended, explosions may be apprehended, from the presence of
atmospherical air; to obviate the danger of which, the flap-doors must
be opened every 10 minutes; but they should remain closed during the
setting of the retorts, and the reflux of sulphurous fumes or acid
should be carried off by a draught-hood over the retorts. The
distillation is carried on without interruption during the week, the
charges being repeated four times in the day. By the third day, the
chamber acquires such a degree of heat as to preserve the sulphur in a
liquid state; on the sixth, its temperature becoming nearly 300° F.,
gives the sulphur a dark hue, on which account the furnace is allowed to
cool on the Sunday. The fittest distilling temperature is about 248°.
The sulphur is drawn off through two iron pipes cast in the iron doors
of the orifices on the side of the chamber opposite to the furnace. The
iron stoppers being taken out of the mouths of the pipes, the sulphur is
allowed to run along an iron spout placed over red-hot charcoal, into
the appropriate wooden moulds.
_Native sulphur_ in its pure state is solid, brittle, transparent,
yellow, or yellow bordering on green, and of a glassy lustre when newly
broken. It occurs frequently in crystalline masses, and sometimes in
complete and regular crystals, which are all derivable from the
rhomboidal octahedron. The fracture is usually conchoidal and shining.
Its specific gravity is 2·072, exceeding somewhat the density of melted
sulphur. It possesses a very considerable refractive power; and doubles
the images of objects even across two parallel faces. Sulphur,
crystallized by artificial means, presents a very remarkable phenomenon;
for by varying the processes, crystals are obtained whose forms belong
to two different systems of crystallization. The red tint, so common in
the crystals of Sicily, and of volcanic districts, has been ascribed by
some mineralogists to the presence of realgar, and by others to iron;
but Stromeyer has found the sublimed orange-red sulphur of Vulcano, one
of the Lipari islands, to result from a natural combination of sulphur
and selenium.
It is extracted from the minerals containing it, at Solfatara, by the
following process:--
Ten earthen pots, of about a yard in height, and 4-1/2 gallons imperial
in capacity, bulging in the middle, are ranged in a furnace called a
gallery; five being set on the one side, and five on the other. These
are so distributed in the body of the walls of the gallery, that their
belly projects partly without, and partly within, while their top rises
out of the vault of the roof. The pots are filled with lumps of the
sulphur ore of the size of the fist; their tops are closed with
earthenware lids, and from their shoulder proceeds a pipe of about 2
inches diameter, which bends down, and enters into another covered pot,
with a hole in its bottom, standing over a tub filled with water. On
applying heat to the gallery, the sulphur melts, volatilizes, and runs
down in a liquid state into the tubs, where it congeals. When one
operation is finished, the pots are re-charged, and the process is
repeated.
In Saxony and Bohemia, the sulphurets of iron and copper are introduced
into large earthenware pipes, which traverse a furnace-gallery; and the
sulphur exhaled flows into pipes filled with cold water, on the outside
of the furnace. 900 parts of sulphuret afford from 100 to 150 of
sulphur, and a residuum of metallic protosulphuret. See METALLURGY and
COPPER.
Volcanic sulphur is purer than that extracted from pyrites; and as the
latter is commonly mixed with arsenic, and some other metallic
impregnations, sulphuric acid made of it would not answer for many
purposes of the arts; though a tolerably good sulphuric acid may be made
directly from the combustion of pyrites, instead of sulphur, in the lead
chambers. The present high price of the Sicilian sulphur is a great
encouragement to its extraction from pyrites. It is said that the common
English brimstone, such as was extracted from the copper pyrites of the
Parys mine of Anglesey, contained fully a fifteenth of residuum,
insoluble in boiling oil of turpentine, which was chiefly orpiment;
while the fine Sicilian sulphur, now imported in vast quantities by the
manufacturers of oil of vitriol, contains not more than 3 per cent. of
foreign matter, chiefly earthy, but not at all arsenical.
Sulphur has been known from the most remote antiquity. From its kindling
at a moderate temperature, it is employed for readily procuring fire,
and lighting by its flame other bodies not so combustible. At Paris, the
preparation of sulphur matches constitutes a considerable branch of
industry. The sulphurous acid formed by the combustion of sulphur in the
atmospheric air, is employed to bleach woollen and silken goods, as also
cotton stockings; to disinfect vitiated air, though it is inferior in
power to nitric acid vapour and chlorine; to kill mites, moths, and
other destructive insects in collections of zoology; and to counteract
too rapid fermentation in wine-vats, &c. As the same acid gas has the
property of suddenly extinguishing flame, sulphur has been thrown into a
chimney on fire, with the best effect; a handful of it being sometimes
sufficient. Sulphur is also employed for cementing iron bars in stone;
for taking impressions from seals and cameos, for which purpose it is
kept previously melted for some time, to give the casts an appearance of
bronze. Its principal uses, however, are for the manufactures of
vermillion, or cinnabar, gunpowder, and sulphuric acid.
See METALLURGY, page 823, for the description of Gahn’s furnace for
extracting sulphur from pyrites.
Pyrites as a bi-sulphuret, consisting of 45·5 parts of iron, and 54·5 of
sulphur, may, by proper chemical means, be made to give off one half of
its sulphur, or about 27 per cent.; but great care must be taken not to
generate sulphurous acid, as is done very wastefully by the Fahlun and
the Goslar processes. By the latter, indeed, not more than 1 or 2 parts
of sulphur are obtained, by roasting 100 parts of the pyritous ores of
the Rammelsberg mines. In these cases, the sulphur is burned, instead of
being sublimed. The residuum of the operation, when it is well
conducted, is black sulphuret of iron, which may be profitably employed
for making copperas. The apparatus for extracting sulphur from pyrites
should admit no more air than is barely necessary to promote the
sublimation.--Sicily produced last year 70,000 tons of sulphur, and
Tuscany 1200; of which Great Britain consumed 46,000; France, 18,000;
other places, 6000. In 1820, Great Britain consumed only 5000 tons.
SULPHURATION, is the process by which woollen, silk, and cotton goods
are exposed to the vapours of burning sulphur, or to sulphurous acid
gas. In the article STRAW-HAT MANUFACTURE, I have described a simple and
cheap apparatus, well adapted to this operation.
Sulphuring-rooms are sometimes constructed upon a great scale, in which
blankets, shawls, and woollen clothes may be suspended freely upon poles
or cords. The floor should be flagged with a sloping pavement, to favour
the drainage of the water that drops down from the moistened cloth. The
iron or stoneware vessels, in which the sulphur is burned, are set in
the corners of the apartment. They should be increased in number
according to the dimensions of the place, and distributed uniformly over
it. The windows and the entrance door must be made to shut hermetically
close. In the lower part of the door, there should be a small opening,
with a sliding shutter, which may be raised or lowered by the mechanism
of a cord passing over a pulley.
The aperture by which the sulphurous acid and azotic gases are let off,
in order to carry on the combustion, should be somewhat larger than the
opening at the bottom. A lofty chimney carries the noxious gases above
the building, and diffuses them over a wide space, their ascension being
promoted by means of a draught-pipe of iron, connected with an ordinary
stove, provided with a valve to close its orifice when not kindled.
When the chamber is to be used, the goods are hung up, and a small fire
is made in the draught-stove. The proper quantity of sulphur being next
put into the shallow pans, it is kindled, the entrance door is closed,
as well as its shutter, while a vent-hole near the ground is opened by
drawing its cord, which passes over a pulley. After a few minutes, when
the sulphur is fully kindled, that vent-hole must be almost entirely
shut, by relaxing the cord; when the whole apparatus is to be let alone
for a sufficient time.
The object of the preceding precautions is to prevent the sulphurous
acid gas escaping from the chamber by the seams of the principal
doorway. This is secured by closing it imperfectly, so that it may admit
of the passage of somewhat more air than can enter by the upper seams,
and the smallest quantity of fresh air that can support the combustion.
The velocity of the current of air may be increased at pleasure, by
enlarging the under vent-hole a little, and quickening the fire of the
draught-stove.
Before opening the entrance door of the apartment, for the discharge of
the goods, a small fire must be lighted in the draught furnace, the
vent-hole must be thrown entirely open, and the sliding shutter of the
door must be slid up, gradually more and more every quarter of an hour,
and finally left wide open for a proper time. By this means the air of
the chamber will become soon respirable.
SULPHURETTED HYDROGEN, is a gas, composed of one part of hydrogen and
sixteen parts of sulphur, by weight. Its specific gravity is 1·1912,
compared to air = 1·0000. It is the active constituent of the
sulphureous mineral waters. When breathed, it is very deleterious to
animal life; and being nearly twice as dense as air, it may be poured
from its generating bottle into cavities; a scheme successfully employed
by M. Thenard to destroy rats in their holes.
SULPHURIC ACID, _Vitriolic Acid_, or _Oil of Vitriol_ (_Acid
sulfurique_, Fr.; _Schwefelsaüre_, Germ.). This important product, the
agent of many chemical operations, was formerly procured by the
distillation of dried sulphate of iron, called _green_ vitriol, whence
the corrosive liquid which came over, having an oily consistence, was
denominated oil of vitriol. This method has been superseded in Great
Britain, France, and most other countries, by the combustion of sulphur
along with nitre, in large leaden chambers; but as the former process,
which is still practised at Bleyl in Bohemia, and Nordhausen in Saxony,
gives birth to some interesting results, I shall describe it briefly.
Into a long horizontal furnace, or gallery of brickwork, a series of
earthenware retorts, of a pear shape, is arranged, with curved necks
fitted into stoneware bottles or condensers. Each retort is charged with
sulphate of iron, which has been previously heated to moderate redness.
The first product of the distillation, a slightly acidulous phlegm, is
allowed to escape; then the retort and receiver are securely luted
together. The fire is now raised, and urged briskly for 36 hours,
whereby the strong sulphuric acid is expelled, in the form of heavy
white vapours, which condense in the cold receiver into an oily-looking
liquid. The latter portions, when received in a separate refrigerator,
frequently concrete into a crystalline mass, formerly called glacial oil
of vitriol. About 64 pounds of strong acid may be obtained from 600
pounds of copperas. It is brown-coloured; and varies in specific-gravity
from 1·842 to 1·896. Its boiling point is so low as 120° Fahr. When
re-distilled in a glass retort, into a receiver surrounded with ice, a
very moderate heat sends over white fumes, which condense into a soft
solid, in silky filaments, like asbestos, tough, and difficult to cut.
When this is exposed to the air, it emits copious fumes of sulphuric
(not sulphurous) acid. It burns holes in paper as rapidly as a red-hot
iron. Dropped in small quantities into water, it excites a hissing
noise, like ignited metal; and in larger quantities, it occasions an
explosion. By dropping a fragment of it into a poised phial containing
water, and stoppering instantly, to prevent the ejection of liquid, by
the ebullition which always ensues, I got a dilute acid, containing a
known portion of the solid acid, from the specific gravity of which, as
well as from its saturating power, I ascertained that the above solid
sulphuric acid was truly anhydrous (_void of water_), consisting of 1
equivalent proportion of sulphur, and 3 of oxygen; or, by weight, of 16
of the former, and 24 of the latter. This acid makes a red solution of
indigo.
The production of sulphuric acid from sulphur and nitre may be elegantly
illustrated by means of a glass globe with a stoppered hole at its side,
and four bent glass tubes inserted into a leaden cap in its upper
orifice. The first tube is to be connected with a heated matrass,
disengaging sulphurous acid from copper filings and sulphuric acid; the
second with a retort, disengaging more slowly deutoxide of azote (nitric
oxide) from copper filings and nitric acid; the third with a vessel for
furnishing steam in a moderate current towards the end of the process,
when no water has been previously admitted into the balloon; the fourth
tube may be upright, and terminate in a small funnel. Through the
opening in the side of the globe, atmospherical air is to be admitted
from time to time, by removing the stopper; after which, the residuary
lighter azote may be allowed to escape by the funnel orifice.
The nitric oxide first absorbs oxygen from the air, becomes, in
consequence, nitrous acid vapour, which giving up one third of its
oxygen to the sulphurous acid, converts this, with the aid of water,
into sulphuric acid, while itself returning to the state of nitric
oxide, is again qualified to take oxygen from the air, and to transfer
it to the sulphurous acid gas; and thus in perpetual rotation. These
oxygenating and disoxygenating processes continue until nearly the whole
oxygen of the atmospheric air contained in the globe is consumed. Were
there little aqueous vapour present, those gases would soon cease to
operate upon each other; for though the nitric oxide became nitrous
acid, this would oxygenate little of the sulphurous acid, because the
three substances would condense into white crystals upon the sides of
the balloon, like hoar frost upon a window-pane in winter. These
indicate a deficiency of aqueous vapour, and an excess of nitrous acid.
On the admission of steam, the crystals disappear, the sulphuric acid is
liquefied, the nitrous acid is converted into nitric acid and nitric
oxide; the former of which combines with the water, while the latter is
converted by the atmospheric oxygen into nitrous acid vapour. A certain
quantity of water is therefore requisite to prevent the formation of
that crystalline compound, which condenses the nitrous acid, and renders
it inoperative in transforming fresh portions of sulphurous acid into
sulphuric. On these principles alone is it possible to oxygenate the
sulphurous acid, by the nitrous acid resuming and surrendering a dose of
oxygen, in perpetual alternation.
It was MM. Clement and Desormes who first had the sagacity to trace
these complicated changes. They showed that nitrous acid gas and
sulphurous acid gas mixed, react on each other through the intervention
of moisture; that there resulted thence a combination of sulphuric acid,
deutoxide of azote (nitrous gas), and water; that this crystalline
compound was instantly destroyed by more water, with the separation of
the sulphuric acid in a liquid state, and the disengagement of nitrous
gas; that this gas re-constituted nitrous acid at the expense of the
atmospheric oxygen of the leaden chamber, and thus brought matters to
their primary condition. From this point, starting again, the particles
of sulphur in the sulphurous acid, through the agency of water, became
fully oxygenated by the nitrous acid, and fell down in heavy drops of
sulphuric acid, while the nitrous gas derived from the nitrous acid, had
again recourse to the air for its lost dose of oxygen. This beautiful
interchange of the oxygenous principle was found to go on, in their
experiments, till either the sulphurous acid, or oxygen in the air, was
exhausted.
They verified this proposition, with regard to what occurs in sulphuric
acid chambers, by mixing in a crystal globe the three substances,
deutoxide of azote, sulphurous acid, and atmospheric air. The immediate
production of red vapours indicated the transformation of the deutoxide
into nitrous acid gas; and now the introduction of a very little water
caused the proper _reaction_, for opaque vapours rose, which deposited
white star-form crystals on the surface of the glass. The gases were
once more transparent and colourless; but another addition of water
melted these crystals with effervescence, when ruddy vapours appeared.
In this manner the phenomena were made to alternate, till the oxygen of
the included air was expended, or all the sulphurous acid was converted
into sulphuric. The residuary gases were found to be nitrous acid gas,
and azote, without sulphurous acid gas; while unctuous sulphuric acid
bedewed the inner surface of the globe. Hence, they justly concluded
their new theory of the manufacture of oil of vitriol to be
demonstrated.
In consequence of their discovery, the manufacture of this acid has
received such improvements, that a nearly double product of it may now
be obtained from the same weight of materials. Indeed, the economy may
be reckoned to be much greater; for one half of the more costly
ingredient, the nitre, formerly employed with a given weight of sulphur,
suffices at present.
In the manufacture of sulphuric acid upon the great scale, two different
systems of working were long prevalent; the intermittent or periodical,
and the continuous or uniform. Both were carried on in large leaden
chambers. In the former, the chambers were closed during the period of
combustion and gaseous combination, but were opened from time to time to
introduce fresh atmospheric air. This method is, I believe, generally
abandoned now, on account of the difficulties and delays attending it,
though it afforded large products in skilful hands. In the latter, a
continuous current of air is allowed to enter at the oven in front of
the chamber for the combustion of the sulphur, and there is a constant
escape of nitrogen gas, with a little sulphurous acid gas, at the remote
end of the roof.
[Illustration: 1101]
_Fig._ 1101. represents a sulphuric acid chamber, _a_, _a_, are the
brick or stone pillars upon which it rests; _b_, _b_, are the sustaining
wooden beams or joists; _c_, is the chimney for the discharge of the
nitrogen; _d_, is the roof, and _e_, the sole of the hearth for the
combustion of the sulphur; _f_, is the cylindrical tunnel, or pipe of
lead or cast iron, for conducting the gasiform materials into the
chamber; _g_, is the steam-boiler; and _h_, the steam-pipe. That plan is
variously modified, by different oil-of-vitriol makers in this country
and in France. Very frequently, the oven _e_, _d_, is not situated under
the chamber, but is built at the end of it, as at _i_, and arched over
with brick, the crown being 9 inches thick. The pipe _f_, 18 inches in
diameter, is then placed outside of the chamber, being inserted into a
brick chimney, and, turning rectangularly, enters it opposite _k_. The
sole of the hearth _e_, is a thick plate of cast iron (not hollowed as
shown in the figure), 5 or 6 feet long, and 3 or 4 broad, with a small
fireplace constructed beneath it, whose smoke-flue runs outwards, under
the floor, to the side wall of the building. The oven is in this case
about 2 feet in height, from the sole to the roof; and it has an iron
door, about 12 inches by 15, which slides up and down in a
tightly-fitted iron frame. This door is frequently placed in the side of
the oven, parallel to the long side of the leaden chamber. A stout
collar of lead is bolted to the chamber, where the pipe enters it. At
the middle of the side of the chamber, about 2 feet above the ground, a
leaden trough is fixed, which serves as a syphon-funnel and water-trap
for introducing water to the acid gases.
Several manufacturers divide the chamber into a series of rectangular
compartments, by parallel leaden screens, 10 or 12 feet asunder, and
allow these compartments to communicate by a narrow opening, or a hole 1
foot square, in the top and bottom of each screen alternately. Thus the
fumes, which enter from the chimney-pipe over _k_, will be forced, by
the screen at _b_, to descend to 1, and pass through the opening there,
to get into the second compartment, whence they will escape near the top
at 2, thus circulating up and down, so as to occasion a complete
agitation and intermixture of their heterogeneous particles. Into the
side of the chamber, opposite to the centre of each compartment, a lead
pipe enters, and proceeds towards the middle of the area, terminating in
a narrow orifice, for discharging a jet of high-pressure steam from a
boiler loaded with 40 pounds upon the square inch. This boiler should be
placed under a shed exterior to the building. It deserves to be noted,
that the incessant tremors produced in this pipe by the escape of the
steam, cause the orifice to contract, and eventually to close almost
entirely, just as the point of a glass tube does when exposed directly
to the flame of a blowpipe. Provision should therefore be made against
this event, by the chemical engineer.
Equidistant between the middle point and each end of the chamber, two
round holes are cut out in its side, about 16 inches in diameter, and 2
feet from the floor; the sheet lead being folded back over the face of
the strong deals which strengthen the chamber in that place. The edges
of the holes are bevelled outwards, so as to fit a large conical plug of
wood faced with lead, called a man-hole door. One or other of these
doors is opened from time to time, to allow the superintendent to
inspect the process, or workmen to enter, after the chamber is well
ventilated, for the purpose of making repairs. The joists or tie-beams,
that bind the rafters of the roof of both the leaden chamber and the
house, must be at least 7 inches deep, by 3 broad, and of such length as
to have their ends supported upon the outer wall, or the columnar
supports of the roof, in case a number of chambers are enclosed together
in parallel ranges under a vast shed. These beams, which lie two feet
apart, suspend the leaden roof, by means of leaden straps, soldered to
its upper surface and edges. The sides of the chamber are sustained by
means of similar leaden straps affixed to the wooden posts (uprights), 4
inches broad by 3 thick, placed two or three feet apart along the sides
of the chamber; resting on the ground below, and mortised into the
tie-beams above. Some chambers rest upon a sand-floor; but they are
preferably placed upon wooden joists, supported by pillars stretching
over an open area, as shown in the figure, into which the workmen may
descend readily, to examine the bottom.
The outlet _c_, on the top of the chamber, is sometimes joined to a long
pipe of lead laid nearly horizontally, with a slight inclination
upwards, along the roof, for favouring the condensation and return of
acid matter.
At the extremity _l_, of the chamber, which, having a downward slope of
1 inch in every 20 feet, should stand from 3 to 6 inches (according to
its length) lower than _i_, one leg of an inverted syphon pipe is fixed
by fusion, into which the liquid of the chamber passing, will show by
its altitude the depth on the bottom within. From the cup-shaped orifice
of that bent-up pipe, the acid of the chamber is drawn off by an
ordinary leaden syphon into the concentration pans.
The sheet lead of which the sides and top are made, should weigh from 5
to 6 pounds per square foot; that of the bottom should be nearly of
double thickness.
Having now detailed, with sufficient minuteness, the construction of the
chamber, I shall next describe the mode of operating with it. There are
at least two plans at present in use for burning the sulphur
continuously in the oven. In the one, the sulphur is laid on the hearth
_e_, (or rather on the flat hearth in the separate oven, above
described,) and is kindled by a slight fire placed under it; which fire,
however, is allowed to go out after the first day, because the oven
becomes by that time sufficiently heated by the sulphur flames to carry
on the subsequent combustion. Upon the hearth, an iron tripod is set,
supporting, a few inches above it, a hemispherical cast-iron bowl
(basin) charged with nitre and its decomposing proportion of strong
sulphuric acid. In the other plan, 12 parts of bruised sulphur, and 1 of
nitre, are mixed in a leaden trough on the floor with 1 of strong
sulphuric acid, and the mixture is shovelled through the sliding iron
door upon the hot hearth. The successive charges of sulphur are
proportioned, of course, to the size of the chamber. In one of the
largest, which is 120 feet long, 20 broad, and 16 high, 12 cwt. are
burned in the course of 24 hours, divided into 6 charges, every fourth
hour, of 2 cwt. each. In chambers of one-sixth greater capacity,
containing 1400 metres cube, 1 ton of sulphur is burned in 24 hours.
This immense production was first introduced at Chaunay and Dieuze,
under the management of M. Clement-Desormes. The bottom of the chamber
should be covered at first with a thin stratum of sulphuric acid, of
spec. grav. 1·07, which decomposes nitrous acid into oxygen and nitrous
gas; but not with mere water, which would absorb the nitrous acid
vapours, and withdraw them from their aerial sphere of action. The
vapour of nitric acid, disengaged from the nitre on the hearth of the
oven, when brought into intimate contact with the sulphurous acid,
either gives up oxygen to it, becomes itself nitrous gas, and converts
it into sulphuric acid; or combines with the sulphurous acid into the
crystalline compound above described, which, the moment it meets with
moisture, is decomposed into sulphuric acid and nitrous gas. The
atmospherical oxygen of the chamber immediately reconverts this gas into
nitrous or nitric acid fumes, which are again ready, with the
co-operation of sulphurous acid gas and aqueous vapour, to produce fresh
quantities of hydrous sulphuric acid (oil of vitriol) and nitrous gas.
At low temperatures, this curious play of chemical affinities has a
great tendency to form the crystalline compound, and to deposit it in a
crust of considerable thickness (from one-half to one inch) on the sides
of the chamber, so as to render the process inoperative. A circumstance
of this kind occurred, in a very striking manner, during winter, in a
manufacture of oil of vitriol in Russia; and it has sometimes occurred,
to a moderate extent, in Scotland. It is called, at Marseilles, the
_maladie des chambres_. It may be certainly prevented, by maintaining
the interior of the chamber, by a jet of steam, at a temperature of 100°
F. When these crystals fall into the dilute acid at the bottom, they are
decomposed with a violent effervescence, and a hissing gurgling noise,
somewhat like that of a tun of beer in brisk fermentation.
M. Clement-Desormes demonstrated the proposition relative to the
influence of temperature by a decisive experiment. He took a glass
globe, furnished with three tubulures, and put a bit of ice into it.
Through the first opening he then introduced sulphurous acid gas;
through the second, oxygen; and through the third, nitrous gas
(deutoxide of azote). While the globe was kept cool, by being plunged in
iced water, no sulphuric acid was formed, though all the ingredients
essential to its production were present. But on exposing the globe to a
temperature of 100° Fahr., the four bodies began immediately to react on
each other, and oil of vitriol was condensed in visible _striæ_.
The introduction of steam is a modern invention, which has vastly
facilitated and increased the production of oil of vitriol. It serves,
by powerful agitation, not only to mix the different gaseous molecules
intimately together, but to impel them against each other, and thus
bring them within the sphere of their mutual chemical attraction. This
is its mechanical effect. Its chemical agency is still more important.
By supplying moisture at every point of the immense included space, it
determines the formation of hydrous sulphuric acid, from the compound of
nitric, nitrous, sulphurous, and dry sulphuric acids. No sooner is this
reaction accomplished, than the nitrous gas resumes its oxygen, from the
continuous atmospherical current, and becomes again fit to operate a
like round of transmutations with sulphurous acid, steam, and oxygen.
The nitrogen (azote), which ought to be the only residuum in a
_perfectly_ regulated vitriol chamber, escapes, by its relative
lightness, at the opening _c_, in the roof, or, more properly speaking,
is displaced by the influx of the heavier gases at the entrance-pipe.
On the intermittent plan, after the consumption of each charge, and
condensation of the product, the chamber was opened, and freely
ventilated, so as to expel the residuary azote, and replenish it with
fresh atmospheric air. In this system there were four distinct stages or
periods:--1. Combustion for two hours; 2. Admission of steam, and
settling, for an hour and a half; 3. Conversion, for three hours, during
which interval the drops of strong acid were heard falling like heavy
hailstones on the bottom; 4. Purging of the chamber, for three quarters
of an hour.
By the continuous method, sulphuric acid may be currently obtained in
the chambers, of the specific gravity 1·350, or 1·450 at most; for, when
stronger, it absorbs and retains permanently much nitrous acid gas; but
by the intermittent, so dense as 1·550, or even 1·620; whence in a
district where fuel is high priced, as near Paris, this method
recommended itself by economy in the concentration of the acid. In Great
Britain, and even in most parts of France, however, where time,
workmen’s wages, and interest of capital, are the paramount
considerations, manufacturers do not find it for their interest in
general to raise the density of the acid in the chambers above 1·400, or
at most 1·500; as the further increase goes on at a retarded rate, and
its concentration from 1·400 to 1·600, in leaden pans, costs very
little.
At about the specific gravity of 1·35, in Great Britain, the liquid of
the chambers is run off, by the syphon above described, into a leaden
gutter or spout, which discharges it into a series of rectangular
vessels made of large sheets of lead, of 12 or 14 lbs. to the square
foot, simply folded up at the angles into pans 8 or 10 inches deep,
resting upon a grate made of a pretty close row of wrought-iron bars of
considerable strength, under which the flame of a furnace plays. Where
coals are very cheap, each pan may have a separate fire; but where they
are somewhat dear, the flame, after passing under the lowest pan of the
range, which contains the strongest acid (at about 1·600), proceeds
upwards with a slight slope to heat the pans of weaker acid, which, as
it concentrates, is gradually run down by syphons to replenish the lower
pans, in proportion as their aqueous matter is dissipated. The 3 or 4
pans constituting the range are thus placed in a straight line, but each
at a different level, terrace-like; _en gradins_, as the French say.
When the acid has thereby acquired the density of 1·650, or 1·700 at
most, it must be removed from the leaden evaporators, because, when of
greater strength, it would begin to corrode them; and it is transferred
into leaden coolers, or run through a long refrigeratory worm-pipe
surrounded by cold water. In this state it is introduced into glass or
platinum retorts, to undergo a final concentration, up to the specific
gravity of 1·842, or even occasionally 1·845, in consequence of slight
saline impurities. When glass retorts are used, they are set in a long
sand-bath over a gallery furnace, resting on fire tiles, under which a
powerful flame plays; and as the flue gradually ascends from the
fireplace, near to which it is most distant from the tiles; to the
remoter end, the heat acts with tolerable equality on the first and last
retort in the range. When platinum stills are employed, they are fitted
into the inside of cast-iron pots, which protect the thin bottom and
sides of the precious metal. The fire being applied directly to the
iron, causes a safe, rapid, and economical concentration of the acid.
The iron pots, with their platinum interior, filled with concentrated
boiling-hot oil of vitriol, are lifted out of the fire-seat by tackle,
and let down into a cistern of cold water, to effect the speedy
refrigeration of the acid, and facilitate its transvasion into carboys
packed in osier baskets lined with straw. Sometimes, however, the acid
is cooled by running it slowly off through a long platinum syphon,
surrounded by another pipe filled with cold water. _Fig._ 1102. shows my
contrivance for this purpose.
[Illustration: 1102]
The under stopcock _a_, being shut, and the leg _b_, being plunged to
nearly the bottom of the still, the worm is to be filled with
concentrated cold acid through the funnel _c_. If that stopcock is now
shut, and _a_ opened, the acid will flow out in such quantity as to
rarefy the small portion of air in the upper part of the pipe _b_,
sufficiently to make the hot acid rise up over the bend, and set the
syphon in action. The flow of the fluid is to be so regulated by the
stopcock _a_, that it may be greatly cooled in its passage by the
surrounding cold water in the vessel _f_, which may be replenished by
means of the tube and funnel _d_, and overflow at _e_.
A manufacturer of acid in Scotland, who burns in each chamber 210 pounds
of sulphur in 24 hours, being at the rate of 420 pounds for 20,000 cubic
feet (= nearly 2000 metres cube) has a product of nearly 3 pounds of
concentrated oil of vitriol for every pound of sulphur and twelfth of a
pound of nitre. The advantage of his process results, I conceive, from
the lower concentration of the acid in the chambers, which favours its
more rapid production.
The platinum retort admits of from 4 to 6 operations in a day, when it
is well mounted and managed. It has a capital of platinum, furnished
with a short neck, which conducts the disengaged vapours into a lead
worm of condensation; and the liquid thus obtained is returned into the
lead pans. Great care must be taken to prevent any particles of lead
from getting into the platinum vessel, since at the temperature of
boiling sulphuric acid, the lead unites with the precious metal, and
thus causes holes in the retort. These must be repaired by soldering-on
a plate of platinum with gold.
Before the separate oven or hearth for burning the sulphur in contact
with the nitre was adopted, this combustible mixture was introduced into
the chamber itself, spread on iron trays or earthen pans, supported
above the water on iron stands. But this plan was very laborious and
unproductive. It is no longer followed.
One of the characters of the good quality of sulphuric acid, is its
dissolving indigo without altering its fine blue colour.
Sulphuric acid, when well prepared, is a colourless and inodorous
liquid, of an oily aspect, possessing a specific gravity, in its most
concentrated state, of 1·842, when redistilled, but as found in
commerce, of 1·845. It is eminently acid and corrosive, so that a single
drop will communicate the power of reddening litmus to a gallon of
water, and will produce an ulcer of the skin when allowed to remain upon
it. If swallowed in its strongest state, in even a small quantity, it
acts so furiously on the throat and stomach as to cause intolerable
agony and speedy death. Watery diluents, mixed with chalk or magnesia,
are the readiest antidotes. At a temperature of about 600° F., or a few
degrees below the melting point of lead, it boils and distils over like
water. This is the best method of procuring sulphuric acid free from the
saline and metallic matters with which it is sometimes contaminated.
The affinity of sulphuric acid for water is so strong that, when exposed
in an open saucer, it imbibes one-third of its weight from the
atmosphere in 24 hours, and fully six times its weight in a few months.
Hence it should be kept excluded from the air. If four parts, by weight,
of the strongest acid be suddenly mixed with one part of water, both
being at 50° F., the temperature of the mixture will rise to 300°;
while, on the other hand, if four parts of ice be mixed with one of
sulphuric acid, they immediately liquefy and sink the thermometer to 4°
below zero. From the great attraction existing between this acid and
water, a saucer of it is employed to effect the rapid condensation of
aqueous vapour as it exhales from a cup of water placed over it; both
standing under the exhausted receiver of an air-pump. By the cold
produced by this unchecked evaporation in vacuo, the water is speedily
frozen.
To determine the purity of sulphuric acid, let it be slowly heated to
the boiling point of water, and if any volatile acid matter be present,
it will evaporate, with its characteristic smell. The presence of saline
impurity, which is the common one, is discovered by evaporating a given
weight of it in a small capsule of platinum placed on red-hot cinders.
If more than two grains remain out of 500, the acid may be reckoned to
be impure. The best test for sulphuric acid, and the soluble salts into
which it enters, is the nitrate of baryta, of which 182 parts are
equivalent to 49 of the strongest liquid acid, or to 40 of the dry, as
it exists in crystallized sulphate of potassa. One twenty thousandth
part of a grain of the acid may be detected by the grayish-white cloud
which baryta forms with it. 100 parts of the concentrated acid are
neutralized by 143 parts of dry carbonate of potassa, and by 110 of dry
carbonate of soda, both perfectly pure.
Of all the acids, the sulphuric is most extensively used in the arts,
and is, in fact, the primary agent for obtaining almost all the others,
by disengaging them from their saline combinations. In this way, nitric,
muriatic, tartaric, acetic, and many other acids, are procured. It is
employed in the direct formation of alum, of the sulphates of copper,
zinc, potassa, soda; in that of sulphuric ether, of sugar by the
saccharification of starch, and in the preparation of phosphorus, &c. It
serves also for opening the pores of skins in tanning, for clearing the
surfaces of metals, for determining the nature of several salts by the
acid characters that are disengaged, &c.
According to the analysis of Dr. Thomson, the crystalline compound
deposited occasionally in the leaden chambers above described consists
of--
Sulphurous acid 0·6387, or 3 atoms.
Sulphuric acid 0·5290 2
Nitric acid 0·3450 1 atom.
Water 0·0733 1
Sulphate of lead 0·0140.
He admits that the proportion of water is a little uncertain; and that
the presence of sulphurous acid was not proved by direct analysis. When
heated with water, the crystalline matter disengages nitrous gas in
abundance; lets fall some sulphate of lead; and the liquid is found to
be sulphuric acid. When heated without water, it is decomposed with
emission of nitrous gas and fuming nitric acid; leaving a liquid which,
mixed with water, produces a brisk effervescence, consisting chiefly of
nitrous gas.
The following TABLE shows the quantity of concentrated and dry sulphuric
acid in 100 parts of dilute, at different densities, by my experiments,
published in the Quarterly Journal of Science, for October, 1817:--
+-------+---------+-------+
|Liquid.|Sp. grav.| Dry. |
+-------+---------+-------+
| 100 | 1·8460 |81·54 |
| 99 | 1·8438 |80·72 |
| 98 | 1·8415 |79·90 |
| 97 | 1·8391 |79·09 |
| 96 | 1·8366 |78·28 |
| 95 | 1·8340 |77·46 |
| 94 | 1·8288 |76·65 |
| 93 | 1·8235 |75·83 |
| 92 | 1·8181 |75·02 |
| 91 | 1·8026 |74·20 |
| 90 | 1·8070 |73·39 |
| 89 | 1·7986 |72·57 |
| 88 | 1·7901 |71·75 |
| 87 | 1·7815 |70·94 |
| 86 | 1·7728 |70·12 |
| 85 | 1·7640 |69·31 |
| 84 | 1·7540 |68·49 |
| 83 | 1·7425 |67·68 |
| 82 | 1·7315 |66·86 |
| 81 | 1·7200 |66·05 |
| 80 | 1·7080 |65·23 |
| 79 | 1·6972 |64·42 |
| 78 | 1·6860 |63·60 |
| 77 | 1·6744 |62·78 |
| 76 | 1·6624 |61·97 |
| 75 | 1·6500 |61·15 |
| 74 | 1·6415 |60·34 |
| 73 | 1·6321 |59·52 |
| 72 | 1·6204 |58·71 |
| 71 | 1·6090 |57·89 |
| 70 | 1·5975 |57·08 |
| 69 | 1·5868 |56·26 |
| 68 | 1·5760 |55·45 |
| 67 | 1·5648 |54·63 |
| 66 | 1·5503 |53·82 |
| 65 | 1·5390 |53·00 |
| 64 | 1·5280 |52·18 |
| 63 | 1·5170 |51·37 |
| 62 | 1·5066 |50·55 |
| 61 | 1·4960 |49·74 |
| 60 | 1·4860 |48·92 |
| 59 | 1·4760 |48·11 |
| 58 | 1·4660 |47·29 |
| 57 | 1·4560 |46·48 |
| 56 | 1·4460 |45·66 |
| 55 | 1·4360 |44·85 |
| 54 | 1·4265 |44·03 |
| 53 | 1·4170 |43·22 |
| 52 | 1·4073 |42·40 |
| 51 | 1·3977 |41·58 |
| 50 | 1·3884 |40·77 |
| 49 | 1·3788 |39·95 |
| 48 | 1·3697 |39·14 |
| 47 | 1·3612 |38·32 |
| 46 | 1·3530 |37·51 |
| 45 | 1·3440 |36·69 |
| 44 | 1·3345 |35·88 |
| 43 | 1·3255 |35·06 |
| 42 | 1·3165 |34·25 |
| 41 | 1·3080 |33·43 |
| 40 | 1·2999 |32·61 |
| 39 | 1·2913 |31·80 |
| 38 | 1·2826 |30·98 |
| 37 | 1·2740 |30·17 |
| 36 | 1·2654 |29·35 |
| 35 | 1·2572 |28·54 |
| 34 | 1·2490 |27·72 |
| 33 | 1·2409 |26·91 |
| 32 | 1·2334 |26·09 |
| 31 | 1·2260 |25·28 |
| 30 | 1·2184 |24·46 |
| 29 | 1·2108 |23·65 |
| 28 | 1·2032 |22·83 |
| 27 | 1·1956 |22·01 |
| 26 | 1·1876 |21·20 |
| 25 | 1·1792 |20·38 |
| 24 | 1·1706 |19·57 |
| 23 | 1·1626 |18·75 |
| 22 | 1·1549 |17·94 |
| 21 | 1·1480 |17·12 |
| 20 | 1·1410 |16·31 |
| 19 | 1·1330 |15·49 |
| 18 | 1·1246 |14·68 |
| 17 | 1·1165 |13·86 |
| 16 | 1·1090 |13·05 |
| 15 | 1·1019 |12·23 |
| 14 | 1·0953 |11·41 |
| 13 | 1·0887 |10·60 |
| 12 | 1·0809 | 9·78 |
| 11 | 1·0743 | 8·97 |
| 10 | 1·0682 | 8·15 |
| 9 | 1·0614 | 7·34 |
| 8 | 1·0544 | 6·52 |
| 7 | 1·0477 | 5·71 |
| 6 | 1·0405 | 4·89 |
| 5 | 1·0336 | 4·08 |
| 4 | 1·0268 | 3·26 |
| 3 | 1·0206 | 2·446 |
| 2 | 1·0140 | 1·63 |
| 1 | 1·0074 | 0·8154|
+-------+---------+-------+
SUMACH (Eng. and Fr.; _Schmack_, Germ.); is the powder of the leaves,
peduncles, and young branches of the _Rhus coriaria_, and _Rhus
cotinus_, shrubs which grow in Hungary, the Bannat, and the Illyrian
provinces. Both kinds contain tannin, with a little yellow
colouring-matter, and are a good deal employed for tanning
light-coloured leathers; but the first is the best. With mordants, it
dyes nearly the same colours as galls. In calico-printing, sumach
affords, with a mordant of tin, a yellow colour; with acetate of iron,
weak or strong, a gray or black; and with sulphate of zinc, a
brownish-yellow. A decoction of sumach reddens litmus paper strongly;
gives white flocks with the protomuriate of tin; pale-yellow flocks with
alum; blue flocks with red sulphate of iron, with an abundant
precipitate. In the south of France, the twigs and leaves of the
_Coriaria myrthifolia_ are used for dyeing, under the name of _rédoul_,
or _rodou_.
SWEEP-WASHER, is the person who extracts from the sweepings, potsherds,
&c., of refineries of silver and gold, the small residuum of precious
metal.
SYNTHESIS, is a Greek word, which signifies combination, and is applied
to the chemical action which unites dissimilar bodies into a uniform
compound; as sulphuric acid and lime, into gypsum; or chlorine and
sodium, into culinary salt.
SYRUP, is a solution of sugar in water. Cane-juice, concentrated to a
density of 1·300, forms a syrup which does not ferment in the transport
home from the West Indies, and may be boiled and refined at one step
into superior sugar-loaves, with eminent advantage to the planter, the
refiner, and the revenue.