SAFETY LAMP. I have reserved for this place an account of the patented
improvement made upon Davy’s lamp by Messrs. Upton and Roberts; the
latter of whom, having worked in coal mines from a boy, and having
observed, that in peculiar circumstances, the Davy was insecure, was led
to contrive certain modifications of it, for which he received, some
years ago, a reward from the Society of Arts. It appears from undoubted
experiments, that if a jet of carburetted hydrogen (coal gas for
example) be impelled with very moderate force against the side of the
Davy, it will first fill the wire cylinder of the burning lamp with
flame, and then take fire itself exteriorly. This passage of the flame
of explosive gases through the meshes of wire gauze of the fineness
prescribed for safety lamps by Sir H. Davy, was demonstrated in several
trials before the select committee of the House Commons on accidents in
mines, by Mr. Pereira, at the London University.[49] While the gas is at
rest, relatively to Davy’s lamp, the explosion has never been known to
pass; but “if,” says Mr. Pereira, “a lamp be held before a jet of gas
until it becomes hot (a red heat is not essential), and then gently
moved, the flame will pass, and the experiment may be repeated
successively a number of times in the minute.” Two layers of wire gauze,
though they greatly impede the transmission of light, will still permit
that of flame, in the above circumstances. In Upton and Roberts’ lamp,
there is but one coat of wire gauze, but it is enclosed in a glass
cylinder, in such a manner as to admit the air which feeds the flame
only under its bottom, first through an annular range of holes, and next
through one disc, or several, of wire gauze, fixed a little way below
the wick. The explosive air, after passing up through these wire-gauze
discs, enters a little brass cupola, and is reflected inwards from the
orifice at its top upon the flame, whereby it is completely burned
before it reaches the cavity of the surmounting cylinder. By this
reverberatory action of the air upon the wick, the intensity of the
light is at the same time greatly augmented. Since the feed orifices of
the lamp are small in comparison with the capacity of the surmounting
cage, the latter does not get filled with flame on being plunged in an
explosive gaseous mixture, as happens to the naked cage of Davy. The
wire gauze can never, therefore, become very hot, far less ignited, in
the new lamp. There are, in fact, three impediments to the passage of
the flame out of the lamp; first, the stratum of carbonic acid round
the light; secondly, the wire-gauze cylinder; and thirdly, the glass
cylinder. The entrance at the bottom may be made secure in any desired
degree, by multiplying the layers of wire cloth. The top is protected,
moreover, by a brass hood, through which the currents of carbonic acid
and nitrogen gases, continually ascending from the burning wick, oppose
certain obstacles to the transmission of flame downwards. Even should
the glass be accidentally broken, the lamp is still a complete Davy.
[49] On the 30th of July, 1835.
In the experiments made before the honourable committee at the London
University, Mr. Pereira showed, first, that when a jet of coal-gas
alone, or an explosive mixture of coal-gas and air, impinged upon the
wire-gauze cylinder of one of Davy’s lamps with a certain force, the
flame generally passed through the meshes, of which there were from 950
to 1024 in the square inch. When a mixture of four parts of hydrogen,
and one of coal-gas was directed in a jet upon the lighted lamps of
Davy, Stevenson, Dillon, Wood of Killingworth (called the refrigerating
lamp), Robson, and Clanny, the flame readily passed; but when thrown
upon the lamp of Upton and Roberts, it did not once pass, causing merely
slight detonations within the lamp. When the force of the jet was
augmented, it extinguished the light. This lamp was finally subjected to
the still severer test of a mixture of four parts of atmospherical air,
and one of hydrogen; yet it did not explode it. When exposed to a
mixture of two-thirds of air, and one of hydrogen, the lamp was
immediately extinguished.
The following, out of many certificates, appears to me decisive in
favour of this improvement of Davy’s lamp. It comes from an experienced
pitman, in a very deep and extensive coal mine, which I know to be
replete with explosive gas, as I have myself visited it in company with
its accomplished engineer, John Buddle, Esq.
“I hereby certify that I have this day tried Messrs. Upton and Roberts’
new patent safety lamp, in the Jarrow colliery; and I state, as an
experienced pitman, having been thirty-two years master wasteman in that
colliery, that I greatly prefer this new lamp to the common Davy lamp. I
had it between five and six hours on trial in the pit. I consider that
it gives about three times the light of the Davy lamp, as I could see at
least ten yards before me in a straight line; and of its great safety I
can have no doubt, as it does not fill with flame, as the Davy does. And
although I had this extra light, there was much less oil consumed. I
consider it a good working lamp.
“Jarrow Colliery, near Newcastle on Tyne, March 31, 1836.” (Signed)
“ROBERT FAIRLY.”
[Illustration: 953]
_Fig._ 953., is a vertical section through the middle of the lamp. _a_,
_a_, is the oil-cistern, showing the fold of the wick; it is covered at
top with _b_, _b,_ several layers of wire gauze; _c_, _c_, is the
perforated brass ring, under these layers, for admitting air, which is
reverberated upon the burning wick by the cupola _c_; _d_, _d_, is the
cylinder of glass, surrounding the wire-cloth one; _e_, _e_, is the
safety brass hood, which screws down in the frame, so as to cover in the
top of the glass chimney; _f_, is the arched wire for suspending the
lamp to the girdle of the miner; _g_, is the bent tube for supplying oil
to the cistern; and _h_ is the safety-trimmer, shown more distinctly in
the figure illustrative of the LAMP of DAVY.
Between the glass and the cage there should be a space of about
one-tenth of an inch, forming an annular chimney for the free
ventilation of the flame; and between the under edge of the hood _e_,
and the upper rim of the glass, there should likewise be an interval, as
also vent-holes in the top of the hood, for the free escape of the
smoke. The orifice of the little tube _g_, should be rather lower than
the ring of holes _c_, otherwise the oil, when incautiously poured into
it, might overflow them, and prevent the lamp from burning. _The figure
is drawn somewhat in perspective._
As the naked cage of Davy often gets red-hot with flame; as it is
sometimes used for hours by miners in this most hazardous state; as this
lamp gives so little light as to tempt rash men to remove its
safety-cage;[50] as “it is upon record, that taking the average of ten
years previous to the introduction of Sir H. Davy’s safety lamp, and
allowing one clear year for its introduction, and of ten years after it
was properly introduced, there had been double the number of accidents,
and at least double the number of deaths, of what took place in the ten
years previous to its introduction;[51] as his lamp in explosive
air-courses needs to be carried close upon the bosom, or under the coat
of the miner; as it was declared by its illustrious inventor to be
dangerous when exposed to such currents of explosive gas; and as the
above described modification of it is free from all these defects and
dangers,--I humbly apprehend that no conscientious proprietor or viewer
of coal-mines will delay to substitute the lamp of Upton and Roberts for
the naked Davy, for otherwise he will certainly stand in a very painful
predicament before a coroner’s inquest, at the next mortal casualty from
explosion.”
[50] At Rowpit Harraton, June 30, 1817, thirty-eight lives were lost
by the wilfulness of one man unscrewing it, though he was well
forewarned of the danger. He said, “he could not see with that thing,”
meaning the Davy.--_Buddle, in Report of House of Commons_, p. 215.
[51] Dr. Reid Clanny, in Report on Accidents in Mines, p. 32. I
observe that in Sykes’ _Local Records_ of the counties of Durham and
Northumberland, corrected by J. Buddle, Esq., there are 540 deaths by
explosions, between June, 1817, and June, 1835. What a mass of misery
to the families of the sufferers!
The patentees have, I am told, been put to so much trouble and expense
in trying to introduce this life-protector into our coal-mines, that
they have in a great measure abandoned the business. Messrs. Smith of
Birmingham have meanwhile undertaken to make the lamps.
SAFFLOWER. This dye-stuff has been fully described under CARTHAMUS and
ROUGE.
SAFFRON (_Saffran_, Fr. and Germ.); is a filamentous cake, composed of
the stigmata of the flowers of the _Crocus sativus_. It contains a
yellow matter called _polychroïte_, because a small quantity of it is
capable of colouring a great body of water. This is obtained by
evaporating the watery infusion of saffron to the consistence of an
extract, digesting the extract with alcohol, and concentrating the
alcoholic solution. The polychroïte remains in the form of a brilliant
mass, of a reddish-yellow colour, transparent, and of the consistence of
honey. It has the agreeable smell, with the bitter pungent taste, of
saffron. It is very soluble in water; and if it be stove-dried, it
deliquesces speedily in the air. According to M. Henry _père_,
polychroïte consists of 80 parts of colouring matter, combined with 20
parts of a volatile oil, which cannot be separated by distillation till
the colouring matter has been combined with an alkali. By mixing one
part of shred saffron with eight parts of saturated brine, and one-half
part of caustic lye, and distilling the mixture, the oil comes over into
the receiver, and leaves the colouring matter in the retort, which may
be precipitated from the alkaline solution by an acid. The pure
colouring matter, when dried, is of a scarlet hue, and then readily
dissolves in alcohol, as also in the fat and volatile oils, but
sparingly in water. Light blanches the reddish-yellow of saffron, even
when it is contained in a full phial well corked. Polychroïte, when
combined with fat oil, and subjected to dry distillation, affords
ammonia, which shows that azote is one of its constituents. Sulphuric
acid colours the solution of polychroïte indigo blue, with a lilac cast;
nitric acid turns it green, of various shades, according to the state of
dilution. Protochloride (muriate) of tin produces a reddish precipitate.
Saffron is employed as a seasoning in French cookery. It is also used to
tinge confectionary articles, liqueurs, and varnishes; but rarely as a
pigment.
SAGO (_Sagou_, Fr. and Germ.); is a species of starch, extracted from
the pith of the sago palm, a tree which grows to the height of 30 feet
in the Moluccas and the Philippines. The tree is cut down, cleft
lengthwise, and deprived of its pith, which being washed with water upon
a sieve, the starchy matter comes out, and soon forms a deposit. This is
dried to the consistence of dough, pressed through a metal sieve to corn
it (which is called _pearling_), and then dried over a fire with
agitation in a shallow copper pan. Sago is sometimes imported in the
pulverulent state, in which it can be distinguished from arrow-root only
by microscopic examination of its particles. These are uniform and
spherical, not unequal and ovoid, like those of arrow-root.
SAL AMMONIAC. The manufacture of this salt may be traced to the remotest
era. Its name is derived from Ammonia, or the temple of Jupiter Ammon,
in Egypt, near to which the salt was originally made. Sal ammoniac
exists ready formed in several animal products. The dung and urine of
camels contain a sufficient quantity to have rendered its extraction
from them a profitable Egyptian art in former times, in order to supply
Europe with the article. In that part of Africa, fuel being very scarce,
recourse is had to the dung of these animals, which is dried for that
purpose, by plastering it upon the walls. When this is afterwards burned
in a peculiar kind of furnace, it exhales a thick smoke, replete with
sal ammoniac in vapour; the soot of course contains a portion of that
salt, condensed along with other products of combustion. In every part
of Egypt, but especially in the Delta, peasants are seen driving asses
loaded with bags of that soot, on their way to the sal ammoniac works.
Here it is extracted in the following manner. Glass globes coated with
loam are filled with the soot pressed down by wooden rammers, a space of
only two or three inches being left vacant, near their mouths. These
globes are set in round orifices formed in the ridge of a long vault, or
large horizontal furnace flue. Heat is gradually applied by a fire of
dry camels’ dung, and it is eventually increased till the globes become
obscurely red. As the muriate of ammonia is volatile at a temperature
much below ignition, it rises out of the soot in vapour, and gets
condensed into a cake upon the inner surface of the top of the globe. A
considerable portion, however, escapes into the air; and another portion
concretes in the mouth, which must be cleared from time to time by an
iron rod. Towards the end, the obstruction becomes very troublesome, and
must be most carefully attended to and obviated, otherwise the globes
would explode by the uncondensed vapours. In all cases, when the
subliming process approaches to a conclusion, the globes crack or split;
and when they come to be removed, after the heat has subsided, they
usually fall to pieces. The upper portion of the mass is separated,
because to it the white salt adheres; and on detaching the pieces of
glass with a hatchet, it is ready for the market. At the bottom of each
balloon a nucleus of salt remains, surrounded with fixed pulverulent
matter. This is reserved, and after being bruised, is put in along with
the charge of soot in a fresh operation.
The sal ammoniac obtained by this process is dull, spongy, and of a
grayish hue; but nothing better was for a long period known in commerce.
Forty years ago, it fetched 2_s._ 6_d._ a pound; now, perfectly pure sal
ammoniac may be had at one-fifth part of that price.
Various animal offals develope during their spontaneous putrefactive
fermentation, or their decomposition by heat, a large quantity of free
or carbonated ammonia, among their volatile products. Upon this
principle many sal ammoniac works have been established. In the
destructive distillation of pitcoal, there is a considerable quantity of
ammoniacal products, which are also worked up into sal ammoniac.
The first attempts made in France to obtain sal ammoniac profitably in
this manner, failed. A very extensive factory of the kind, which
experienced the same fate, was under the superintendence of the
celebrated Baumé, and affords one out of a thousand instances where
theoretical chemists have shown their total incapacity for conducting
operations on the scale of manufacturing economy. It was established at
Gravelle near Charenton, and caused a loss to the shareholders in the
speculation of upwards of 400,000 francs. This result closed the concern
in 1787, after a foolish manipulation of 27 years. For ten years after
that event, all the sal ammoniac consumed in France was imported into it
from foreign countries. Since then the two works of MM. Payen and
Pluvinet were mounted, and seem to have been tolerably successful. Coal
soot was, prior to the introduction of the gas-works, a good deal used
in Great Britain for obtaining sal ammoniac. In France, bones and other
animal matters are distilled in large iron retorts, for the manufacture
of both animal charcoal and sal ammoniac.
[Illustration: 954 955]
These retorts are iron cylinders, 2 or 3 feet in diameter, and 6 feet
long. _Figs._ 954. and 955. show the form of the furnace, and the manner
in which the cylinders are arranged; the first being a longitudinal, the
second a transverse section of it. A, the ash-pits under the grates; B,
the fireplaces, arched over at top; C, the vault or bench of
fire-bricks, perforated inside with eight flues for distributing the
flame; D, a great arch, with a triple voussoir D, _d´_, _d´´_, under
which the retorts are set. The first arch D, is perforated with twenty
vent-holes; the second, with four vent-holes; through which the flame
passes to the third arch, and thence to the common chimney-stalk. The
retorts _e_, are shut by the door _e´_ (_fig._ 955.), luted, and made
fast with screw-bolts. Their other ends _e´´_ terminate in tubes _f_,
_f_, _f_, which all enter the main pipe _h_. The condensing pipe
proceeds slantingly downwards from the further end of _h_, and dips into
a large sloping iron cylinder immersed in cold water. See GAS-LIGHT and
STOVE, for a better plan of furnace.
[Illustration: 956]
The filters used in the large sal ammoniac works in France are
represented in _fig._ 956. The apparatus consists----1. of a wooden
chest _a_, lined with lead, and which is turned over at the edges; a
socket of lead _b_, soldered into the lowest part of the bottom, serves
to discharge the liquid; 2. of a wooden crib or grating formed of
rounded rods, as shown in the section _c_, _c_, and the plan _d_; this
grating is supported one inch at least above the bottom, and set truly
horizontal, by a series of wedges; 3. of an open fabric of canvas or
strong calico, laid on the grating, and secured over the edges, so as to
keep it tense. A large wooden reservoir _f_, lined with lead, furnished
with a cover, is placed under each of the filters; a pump throws back
once or twice upon the filters what has already passed through. A common
reservoir _g_, below the others, may be made to communicate at pleasure
with one of them, by means of intermediate stopcocks.
The two boilers for evaporating and decomposing are made of lead, about
one quarter of an inch thick, set upon a fire-brick vault, to protect
them from the direct action of the flame. Through the whole extent of
their bottoms above the vault, horizontal cast-iron plates, supported by
ledges and brick compartments, compel the flame and burned air, as they
issue from the arch, to percur many sinuosities before they pass up the
chimney. This floor of cast iron is intended to support the bottom of
the boiler, and to diffuse the heat more equably. The leaden boilers are
surrounded with brickwork, and supported at their edges with a wooden
frame. They may be emptied at pleasure into lower receivers, called
crystallizers, by means of leaden syphons and long-necked funnels.
The crystallizers are wooden chests lined with lead, 15 inches deep, 3
or 4 feet broad, and from 6 to 8 feet long; and may be inclined to one
side at pleasure. A round cistern receives the drainings of the
mother-waters. The pump is made of lead, hardened with antimony and tin.
[Illustration: 957 958 959 960 961]
The subliming furnace is shown in _figs._ 957. and 958. by a transverse
and longitudinal section. _a_ is the ash-pit; _b_, the grate and
fireplace; _c_, the arch above them. This arch, destined to protect the
bottles from the direct action of the fire, is perforated with
vent-holes, to give a passage to the products of combustion between the
subliming vessels. _d_, _d_, are bars of iron, upon which the bottoms of
the bottles rest; _e_, stoneware bottles, protected by a coating of loam
from the flame.
_Fig._ 959. shows the cast-iron plates, _a_, _b_, _c_, which, placed
above the vaults, receive each two bottles in a double circular opening.
At the extremity of the above furnace, a second one, called the drier,
_fig._ 960., receives the products of the combustion of the first, at A,
under horizontal cast-iron plates, and upon which the bottom of a rather
shallow boiler B, rests. After passing twice under these plates, round a
longitudinal brick partition _b_, _b´_, _b´´_, the products of
combustion enter the smoke chimney C. See plan, _fig._ 961.
The boiler set over this furnace should have no soldered joints. It may
be 3-1/2 feet broad, 9 or 10 feet long, and 1 foot deep. The concrete
sal ammoniac may be crushed under a pair of edge mill-stones, when it is
to be sold in powder.
Bones, blood, flesh, horns, hoofs, woollen rags, silk, hair, scrapings
of hides and leather, &c., may be distilled for procuring ammonia. When
bones are used, the residuum in the retort is bone black. The charcoal
from the other substances will serve for the manufacture of prussian
blue. The bones should undergo a degree of calcination beyond what the
ammoniacal process requires, in order to convert them into the best bone
black; but the other animal matters should not be calcined up to that
point, otherwise they are of little use in the prussian blue works. If
the bones be calcined, however, so highly as to become glazed, their
decolouring power on syrups is nearly destroyed. The other substances
should not be charred beyond a red-brown heat.
The condensed vapours from the cylinder retorts afford a compound liquor
holding carbonate of ammonia in solution, mixed with a large quantity of
empyreumatic oil, which floats at top. Lest incrustations of salt should
at any time tend to obstruct the tubes, a pipe should be inserted within
them, and connected with a steam boiler, so as to blow steam through
them occasionally.
The whole liquors mixed have usually a density of 8° or 9° Baumé
(1·060). The simplest process for converting their carbonate of ammonia
into muriate, is to saturate them with muriatic acid, to evaporate the
solution in a leaden boiler till a pellicle appears, to run it off into
crystallizers, and to drain the crystals. Another process is, to
decompose the carbonate of ammonia, by passing its crude liquor through
a layer of sulphate of lime, 3 or 4 inches thick, spread upon the
filters, _fig._ 956. The liquor may be laid on with a pump; it should
never stand higher than 1 or 2 inches above the surface of the bruised
gypsum, and it should be closely covered with boards, to prevent the
dissipation of the volatile alkali in the air. When the liquor has
passed through the first filter, it must be pumped upon the second; or
the filters being placed in a terrace form, the liquor from the first
may flow down upon the second, and thus in succession. The last filter
should be formed of nearly fresh gypsum, so as to ensure the thorough
conversion of the carbonate into sulphate. The resulting layers of
carbonate of lime should be washed with a little water, to extract the
sulphate of ammonia interposed among its particles. The ammoniacal
liquor thus obtained must be completely saturated, by adding the
requisite quantity of sulphuric acid; even a slight excess of acid can
do no harm. It is then to be evaporated, and the oil must be skimmed off
in the course of the concentration. When the liquid sulphate has
acquired the density of about 1·160, sea salt should be added, with
constant stirring, till the whole quantity equivalent to the double
decomposition be introduced into the lead boiler.
The fluid part must now be drawn off by a syphon into a somewhat deep
reservoir, where the impurities are allowed to subside; it is then
evaporated by boiling, till the sulphate of soda falls down in granular
crystals, as the result of the mutual reaction of the sulphate of
ammonia and muriate of soda; while the more soluble muriate of ammonia
remains in the liquor. During this precipitation, the whole must be
occasionally agitated with wooden paddles; the precipitate being in the
intervals removed to the cooler portion of the pan, in order to be taken
out by copper rakes and shovels, and thrown into draining-hoppers,
placed near the edges of the pan. The drained sulphate of soda must be
afterwards washed with cold water, to extract all the adhering sal
ammoniac.
The liquor thus freed from the greater part of the sulphate, when
sufficiently concentrated, is to be drawn off by a lead syphon, into the
crystallizers, where, at the end of 20 or 30 hours, it affords an
abundant crop of crystals of sal ammoniac. The mother-water may then be
run off, the crystallizers set aslope to drain the salt, and the salt
itself must be washed, first by a weak solution of sal ammoniac, and
lastly with water. It must be next desiccated, by the apparatus _fig._
960., into a perfectly dry powder, then put into the subliming stoneware
balloons, by means of a funnel, and well rammed down. The mouth of the
bottle is to be closed with a plate or inverted pot of any kind. The
fire must be nicely regulated, so as to effect the sublimation of the
pure salt from the under part of the bottle, with due regularity, into a
white cake in the upper part. The neck of the bottle should be cleared
from time to time with a long steel skewer, to prevent the risk of
choking, and consequent bursting; but in spite of every precaution,
several of the bottles crack almost in every operation. In Scotland, sal
ammoniac is sublimed in cast-iron pots lined with thin fire-tiles, made
in segments accommodated to the internal surface of the pots; the vapour
being received and condensed into cakes, within balloons of green glass
set over their mouths. The salt, when taken out, and freed by scraping
from any adhering ochreous or other impurities, is ready for the market,
being sold in hollow spherical masses. The residuum in the pots or
bottles may be partially worked up in another operation. The greatest
evil is produced by the mixture or even contact of iron, because its
peroxide readily rises in vapour with the sal ammoniac, and tinges it of
a red or yellow colour.
The most ordinary process for converting the ammoniacal liquor of the
gas works into sal ammoniac, is to saturate it with sulphuric acid, and
to decompose the sulphate, thus formed, by the processes above
described. But muriatic acid will be preferred, where it is as cheap as
sulphuric of equivalent saturating power; because a tolerably pure sal
ammoniac is thereby directly obtained. As the coal-gas liquor contains a
good deal of sulphuretted hydrogen, the saturation of it with acid
should be so conducted as to burn the disengaged noxious gases in a
chimney. Formerly human urine was very extensively employed, both in
this country and in France, in the manufacture of sal ammoniac; but
since the general establishment of gas-works it has been, I believe,
abandoned. The process was exceedingly offensive.
The best white sal ammoniac is in spheroidal cakes of about one foot
diameter, three or four inches thick in the middle, somewhat thinner at
the edges, and is semi-transparent or translucent. Each lump weighs
about one quarter of a cwt. As it is easily volatilized by heat, it may
be readily examined as to its sophistication with other salts. Sal
ammoniac has a certain tenacity, and is flexible under the hammer or
pestle. It is principally used in tinning of cast-iron, wrought iron,
copper, brass, and for making the various ammoniacal preparations of
pharmacy.
In a chemical factory near Glasgow, 7200 gallons of ammoniacal liquor,
obtained weekly from the gas-works, are treated as follows:--The liquor
is first rectified by distillation from a waggon-shaped wrought-iron
boiler, into a square cistern of iron lined with lead. 4500 lbs. of
sulphuric acid, of specific gravity 1·625, are then slowly added to the
somewhat concentrated distilled water of ammonia. The produce is 2400
gallons of sulphate of ammonia, slightly acidulous, of specific gravity
1·150, being of such strength as to deposit a few crystals upon the
sides of the lead-lined iron tank in which the saline combination is
made. It is decomposed by common salt.
From the 7200 gallons of the first crude liquor, 900 gallons of tar are
got by subsidence, and 200 gallons of petroleum are skimmed off the
surface. The tar is converted, by a moderate boiling in iron pans, into
good pitch.
SALAMSTONE. See LAPIDARY.
SALEP, or SALOUP, is the name of the dried tuberous roots of the
_Orchis_, imported from Persia and Asia Minor, which are the product of
a great many species of the plant, but especially of the _Orchis
mascula_. Salep occurs in commerce in small oval grains, of a
whitish-yellow colour, at times semi-transparent, of a horny aspect,
very, hard, with a faint peculiar smell, and a taste like that of gum
tragacanth, but slightly saline. These are composed almost entirely of
starchy matter, well adapted for making a thick pap with water or milk,
and are hence in great repute in the Levant, as restorers of the animal
forces. Their aphrodisiacal properties are apocryphal. If the largest
roots of the _Orchis mascula_ of our own country were cleaned, scraped,
steeped for a short time in hot, and then for a few minutes in boiling
water, to extract their rank flavour, afterwards suspended upon strings
to dry in the air, they would afford as nourishing and palatable an
article as the Turkey saloup, and at a vastly lower price.
SALICINE, is a febrifuge substance, which may be obtained in white
pearly crystals from the bark of the white willow (_Salix alba_), of the
aspen tree (_Salix helix_), as also of some other willows, and some
poplars. It has a very bitter taste.
SAL PRUNELLA, is fused nitre cast into cakes or balls.
SAL VOLATILE, is sesquicarbonate of ammonia.
SALT, EPSOM, is sulphate of magnesia.
SALT, MICROCOSMIC, is the triple phosphate of soda and ammonia.
SALT OF AMBER, is succinic acid.
SALT OF LEMONS, is citric acid.
SALT OF SATURN, is acetate of lead.
SALT OF SODA, is carbonate of soda.
SALT OF SORREL, is bi-oxalate of potassa.
SALT OF TARTAR, is carbonate of potassa.
SALT OF VITRIOL, is sulphate of zinc.
SALT PERLATE, is phosphate of soda.
SALTPETRE, is nitre, or nitrate of potassa.
SALT, SEDATIVE, is boracic acid.
SALTS, are an important class of chemical compounds, antiently studied
under the Greek title of _Halurgy_. At one period every inorganic
substance readily soluble in water, was regarded as a salt; and
afterwards, every substance soluble in five hundred times its weight of
water. Thus both acid and alkaline bodies came to be enrolled among
salts; but latterly, the combinations of the acids with alkalis, earths,
and metallic calces (now styled oxides), were alone thought to be
entitled to the denomination of salts, in consequence of their
resemblance in appearance, and supposed analogy in composition, to
culinary salt. Since Sir H. Davy demonstrated that this substance
contained neither acid nor alkaline matter, but that it consisted of
chlorine and the metal sodium, the generality of chemists found it
impossible to include salts under one category of constitution; while a
few have rashly offered to cut the knot, by excluding from the saline
family, chloride of sodium, the patriarch of the whole.
_Salts_, may be justly divided into three orders:
1. The binary, consisting of two single members; such as the bromides,
chlorides, cyanides, fluorides, iodides, carburets, phosphurets,
sulphurets, &c.
2. The bi-binary, consisting of two double members; such as the borates,
bromates, carbonates, chlorates, sulphates, sulphites, hyposulphites,
sulphohydrates, &c.
3. The ternary, consisting of two single members of one genus, and one
member of another; such as the boro-fluorides, silico-fluorides,
sulpho-cyanides, chloriodides, &c.
The species of each order may exist in three states, constituting
neutral salts; supersalts; and subsalts; as for example, the chloride of
sodium, the bisulphate of potassa, the subnitrate of lead, &c.
In the above arrangement, cyanogen is allowed to represent a simple
substance, from its forming analogous compounds with chlorine and
iodine. The neutral state of salts is commonly indicated by their
solutions not changing the colours of litmus, violets, or red cabbage;
the sub-state of salts, by their turning the violet and cabbage green;
and the super-state of salts, by their changing the purple of litmus,
violets, and cabbage, red; but to the generality of this criterion there
are some exceptions. The atomic theory may be advantageously resorted
to, in this predicament. 1. When one prime equivalent of the one member
(whether single or double) of a salt, combines with one prime of the
other member, a neutral salt is the result, as in chloride of sodium or
nitrate of potassa. 2. When two primes of the electro-negative member
combine with one prime of the electro-positive, a supersalt is formed,
as bichloride of tin, or bisulphate of potassa. 3. When one prime of the
electro-negative member combines with two or more primes of the
electro-positive, a subsalt is produced, as the subacetate and
subchromate of lead, &c.
SALT, SEA, or CULINARY; _Chloride of sodium_; _muriate of soda_.
(_Hydrochlorate de soude_, Fr.; _Chlornatrium_, Germ.) Sea salt, or rock
salt, in a state of purity, consists of 60 of chlorine + 40 of sodium,
in 100 parts.
This important species of the saline class possesses, even in mass, a
crystalline structure, derived from the cube, which is its primitive
form. It has generally a foliated texture, and a distinct cleavage; but
it has also sometimes a fibrous structure. The massive salt has a
vitreous lustre. It is not so brittle as nitre; it is nearly as hard as
alum, a little harder than gypsum, and softer than calcareous spar. Its
specific gravity varies from 2·0 to 2·25. When pure, it is colourless,
translucent, or transparent. On exposure to heat, it commonly
decrepitates; but some kinds of rock salt enter quietly into fusion at
an elevated temperature, a circumstance which has been ascribed to their
having been originally subjected to the action of fire.