_Flesh._--The ordinary means employed for preserving butcher meat are,
drying, smoking, salting, and pickling or souring.
_Drying of animal fibre._--The best mode of operating is as
follows:--The flesh must be cut into slices from 2 to 6 ounces in
weight, immersed in boiling water for 5 or 6 minutes, and then laid on
open trellis-work in a drying-stove, at a temperature kept steadily
about 122° F., with a constant stream of warm dry air. That the boiling
water may not dissipate the soluble animal matters, very little of it
should be used, just enough for the meat to be immersed by portions in
succession, whereby it will speedily become a rich soup, fresh water
being added only as evaporation takes place. It is advantageous to add a
little salt, and some spices, especially coriander seeds, to the water.
After the parboiling of the flesh has been completed, the soup should be
evaporated to a gelatinous consistence, in order to fit it for forming a
varnish to the meat after it is dried, which may be completely effected
within two days in the oven. By this process two-thirds of the weight is
lost. The perfectly dry flesh must be plunged piece by piece in the
fatty gelatinous matter liquefied by a gentle heat; then placed once
more in the stove, to dry the layer of varnish. This operation may be
repeated two or three times, in order to render the coat sufficiently
uniform and thick. Butcher’s meat dried in this way, keeps for a year,
affords, when cooked, a dish similar to that of fresh meat, and is
therefore much preferable to salted provisions. The drying may be
facilitated, so that larger lumps of flesh may be used, if they be
imbued with some common salt immediately after the parboiling process,
by stratifying them with salt, and leaving them in a proper pickling-tub
for 12 hours before they are transferred to the stove. The first method,
however, affords the more agreeable article.
_Smoking._--This process consists in exposing meat previously salted, or
merely rubbed over with salt, to wood smoke, in an apartment so distant
from the fire as not to be unduly heated by it, and into which the smoke
is admitted by flues at the bottom of the side walls. Here the meat
combines with the empyreumatic acid of the smoke, and gets dried at the
same time. The quality of the wood has an influence upon the smell and
taste of the smoke-dried meat; smoke from beech wood and oak being
preferable to that from fir and larch. Smoke from the twigs and berries
of juniper, from rosemary, peppermint, &c., imparts somewhat of the
aromatic flavour of these plants. A slow smoking with a slender fire is
preferable to a rapid and powerful one, as it allows the empyreumatic
principles time to penetrate into the interior substance, without drying
the outside too much. To prevent soot from attaching itself to the
provisions, they may be wrapped in cloth, or rubbed over with bran,
which may be easily removed at the end of the operation.
The process of smoking depends upon the action of the wood acid, or the
creosote volatilized with it, which operates upon the flesh. The same
change may be produced in a much shorter time by immersing the meat for
a few hours in pyrolignous acid, then hanging it up in a dry air, which,
though moderately warm, makes it fit for keeping, without any taint of
putrescence. After a few days exposure, it loses the empyreumatic smell,
and then resembles thoroughly smoked provisions. The meat dried in this
way is in general somewhat harder than by the application of smoke, and
therefore softens less when cooked, a difference to be ascribed to the
more sudden and concentrated operation of the wood vinegar, which
effects in a few hours what would require smoking for several weeks. By
the judicious employment of pyrolignous acid diluted to successive
degrees, we might probably succeed in imitating perfectly the effect of
smoke in curing provisions.
_Salting._--The meat should be rubbed well with common salt, containing
about one sixteenth of saltpetre, and one thirty-secondth of sugar, till
every crevice has been impregnated with it; then sprinkled over with
salt, laid down for 24 or 48 hours, and, lastly, subjected to pressure.
It must next be sprinkled anew with salt, packed into proper vessels,
and covered with the brine obtained in the act of pressing, rendered
stronger by boiling down. For household purposes it is sufficient to rub
the meat well with good salt, to put it into vessels, and load it with
heavy weights, in order to squeeze out as much pickle as will cover its
surface. If this cannot be had, a pickle must be poured on it, composed
of 4 pounds of salt, 1 pound of sugar, and 2 oz. of saltpetre, dissolved
in 2 gallons of water.
_Pickling with vinegar._--Vinegar dissolves or coagulates the albumen of
flesh, and thereby counteracts its putrescence. The meat should be
washed, dried, and then laid in strong vinegar. Or it may be boiled in
the vinegar, allowed to cool in it, and then set aside with it in a cold
cellar, where it will keep sound for several months.
Fresh meat may be kept for some months in water deprived of its air. If
we strew on the bottom of a vessel a mixture of iron filings and flowers
of sulphur, and pour over them some water which has been boiled, so as
to expel its air, meat immersed in it will keep a long time, if the
water be covered with a layer of oil, from half an inch to an inch
thick. Meat will also keep fresh for a considerable period when
surrounded with oil, or fat of any kind, so purified as not to turn
rancid of itself, especially if the meat be previously boiled. This
process is called potting, and is applied successfully to fish, fowls,
&c.
Prechtl says that living fish may be preserved 14 days without water, by
stopping their mouths with crumbs of bread steeped in brandy, pouring a
little brandy into them, and packing them in this torpid state in straw.
When put into fresh water, they come alive again after a few hours!
_Prechtl, Encyclop. Technologisches, art. Faülniss Abhaltung._
_Eggs._--These ought to be taken new laid. The essential point towards
their preservation is the exclusion of the atmospheric oxygen, as their
shells are porous, and permit the external air to pass inwards, and to
excite putrefaction in the albumen. There is also some oxygen always in
the air cell of the eggs, which ought to be expelled or rendered
inoperative, which may be done by plunging them for 5 minutes in water
heated to 140° F. The eggs must be then taken out, wiped dry, besmeared
with some oil (not apt to turn rancid) or other unctuous matter, packed
into a vessel with their narrow ends uppermost, and covered with
sawdust, fine sand, or powdered charcoal. Eggs coated with gum arabic,
and packed in charcoal, will keep fresh for a year. Lime water, or
rather milk of lime, is an excellent vehicle for keeping eggs in, as I
have verified by long experience. Some persons coagulate the albumen
partially, and also expel the air by boiling the eggs for two minutes,
and find the method successful. When eggs are intended for hatching,
they should be kept in a cool cellar; for example, in a chamber
adjoining an ice-house. Eggs exposed, in the holes of perforated
shelves, to a constant current of air, lose about 3/4 of a grain of
their weight daily, and become concentrated in their albuminous part, so
as to be little liable to putrefy. For long sea voyages, the surest
means of preserving eggs, is to dry up the albumen and yolk, by first
triturating them into a homogeneous paste, then evaporating this in an
air-stove or a water-bath heated to 125°, and putting up the dried mass
in vessels which may be made air-tight. When used, it should be
dissolved in three parts of cold or tepid water.
Grain of all kinds, as wheat, barley, rye, &c., and their flour, may be
preserved for an indefinite length of time, if they be kiln-dried, put
up in vessels or chambers free from damp, and excluded from the air.
Well dried grain is not liable to the depredations of insects.
To preserve fruits in a fresh state, various plans are adopted. Pears,
apples, plums, &c. should be gathered in a sound state, altogether
exempt from bruises, and plucked, in dry weather, before they are fully
ripe. One mode of preservation is, to expose them in an airy place to
dry a little for eight or ten days, and then to lay them in dry sawdust
or chopped straw, spread upon shelves in a cool apartment, so as not to
touch each other. Another method consists in surrounding them with fine
dry sand in a vessel which should be made air-tight, and kept in a cool
place. Some persons coat the fruit, including their stalks, with melted
wax; others lay the apples, &c., upon wicker-work shelves in a vaulted
chamber, and smoke them daily during 4 or 5 days with vine branches or
juniper wood. Apples thus treated, and afterwards stratified in dry
sawdust, without touching each other, will keep fresh for a whole year.
The drying of garden fruits in the air, or by a kiln, is a well-known
method of preservation. Apples and pears of large size should be cut
into thin slices. From 5 to 6 measures of fresh apples, and from 6 to 7
of pears, afford in general one measure of dry fruit, (biffins). Dried
plums, grapes, and currants are a common article of commerce.
Herbs, cabbages, &c., may be kept a long time in a cool cellar, provided
they are covered with dry sand. Such vegetables are in general preserved
for the purposes of food, by means of drying, salting, pickling with
vinegar, or beating up with sugar. Cabbages should be scalded in hot
water previously to drying; and all such plants, when dried, should be
compactly pressed together, and kept in air-tight vessels. Tuberous and
other roots are better kept in an airy place, where they may dry a
little without being exposed to the winter’s frost.
A partial drying is given to various vegetable juices by evaporating
them to the consistence of a syrup, called a rob, in which so much of
the water is dissipated as to prevent them from running into
fermentation. The fruits must be crushed, squeezed in bags to expel the
juices, which must then be inspissated either over the naked fire, or on
a water or steam bath, in the air or in vacuo. Sometimes a small
proportion of spices is added, which tends to prevent mouldiness. Such
extracts may be conveniently mixed with sugar into what are called
conserves.
Salting is employed for certain fruits, as small cucumbers or gherkins,
capers, olives, &c. Even for peas such a method is had recourse to, for
preserving them a certain time. They must be scalded in hot water, put
up in bottles, and covered with saturated brine, having a film of oil on
its surface, to exclude the agency of the atmospheric air. Before being
used, they must be soaked for a short time in warm water, to extract the
salt. The most important article of diet of this class, is the _sour
kraut_ of the northern nations of Europe, (made from white cabbage,)
which is prepared simply by salting; a little vinegar being formed
spontaneously by fermentation. The cabbage must be cut into small
pieces, stratified in a cask along with salt, to which juniper berries
and carui seeds are added, and packed as hard as possible by means of a
wooden rammer. The cabbage is then covered with a lid, on which a heavy
weight is laid. A fermentation commences, which causes the cabbage to
become more compact, while a quantity of juice exudes and floats on the
surface, and a sour smell is perceived towards the end of the
fermentation. In this condition the cask is transported into a cool
cellar, where it is allowed to stand for a year; and indeed, where, if
well made and packed, it may be kept for several years.
The excellent process for preserving all kinds of butcher meat, fish,
and poultry, first contrived by M. Appert in France, and afterwards
successfully practised upon the great commercial scale by Messrs. Donkin
and Gamble, for keeping beef, salmon, soups, &c. perfectly fresh and
sweet for exportation from this country, as also turtle for importation
thither from the West Indies, deserves a brief description.
Let the substance to be preserved be first parboiled, or rather somewhat
more, the bones of the meat being previously removed. Put the meat into
a tin cylinder, fill up the vessel with seasoned rich soup, and then
solder on the lid, pierced with a small hole. When this has been done,
let the tin vessel thus prepared be placed in brine and heated to the
boiling point, to complete the remainder of the cooking of the meat. The
hole of the lid is now to be closed perfectly by soldering, whilst the
air is rarefied. The vessel is then allowed to cool, and from the
diminution of the volume, in consequence of the reduction of
temperature, both ends of the cylinder are pressed inwards, and become
concave. The tin cases, thus hermetically sealed, are exposed in a
test-chamber, for at least a month, to a temperature above what they are
ever likely to encounter; from 90° to 110° of Fahrenheit. If the process
has failed, putrefaction takes place, and gas is evolved, which, in
process of time, will cause both ends of the case to bulge, so as render
them convex, instead of concave. But the contents of those cases which
stand the test will infallibly keep perfectly sweet and good in any
climate, and for any number of years. If there be any taint about the
meat when put up, it inevitably ferments, and is detected in the proving
process. Mr. Gamble’s turtle is delicious.
This preservative process is founded upon the fact, that the small
quantity of oxygen contained within the vessel gets into a state of
combination, in consequence of the high temperature to which the animal
substances are exposed, and upon the chemical principle, that free
oxygen is necessary as a ferment to commence or give birth to the
process of putrefaction.
I shall conclude this article with some observations upon the means of
preserving water fresh on sea voyages. When long kept in wooden casks,
it undergoes a kind of putrefaction, contracts a disagreeable
sulphureous smell, and becomes undrinkable. The influence of the
external air is by no means necessary to this change, for it happens in
close vessels even more readily than when freely exposed to the
atmospherical oxygen. The origin of this impurity lies in the animal and
vegetable juices which the water originally contained in the source from
which it was drawn, or from the cask, or insects, &c. These matters
easily occasion, with a sufficient warmth, fermentation in the stagnant
water, and thereby cause the evolution of offensive gases. It would
appear that the gypsum of hard waters is decomposed, and gives up its
sulphur, which aggravates the disagreeable odour; for selenitic waters
are more apt to take this putrid taint, than those which contain merely
carbonate of lime.
As the corrupted water has become unfit for use merely in consequence of
the admixture of these foreign matters, for water in itself is not
liable to corruption, so it may be purified again by their separation.
This purification may be accomplished most easily by passing the water
through charcoal powder, or through the powder of rightly calcined
bone-black. The carbon takes away not only the finely diffused corrupt
particles, but also the gaseous impurities. By adding to the water a
very little sulphuric acid, about 30 drops to 4 pounds, Lowitz says that
two-thirds of the charcoal may be saved. Undoubtedly the sulphuric acid
acts here, as in other similar cases, by the coagulation and separation
of the albuminous matters, combining with them, and rendering them more
apt to be seized by the charcoal. A more effectual agent for the
purification of foul water is to be found in alum. A dram of pounded
alum should be dissolved with agitation in a gallon of the water, and
then left to operate quietly for 24 hours. A sediment falls to the
bottom, while the water becomes clear above, and may be poured off. The
alum combines here with the substances dissolved in the water, as it
does with the stuffs in the dyeing copper. In order to decompose any
alum which may remain in solution, the equivalent quantity of crystals
of carbonate of soda may be added to it.
The red sulphate of iron acts in the same way as alum. A few drops of
its solution are sufficient to purge a pound of foul water. The foreign
matters dissolved in the water, which occasion putrefaction, become
insoluble, in consequence of oxidizement, like vegetable extractive, and
are precipitated. On this account, also, foul water may be purified, by
driving atmospheric air through it with bellows, or by agitating it in
contact with fresh air, so that all its particles are exposed to oxygen.
Thus we can explain the influence of streams and winds, in counteracting
the corruption of water exposed to them. Chlorine acts still more
energetically than the air in purifying water. A little aqueous chlorine
added to foul water, or the transmission of a little gaseous chlorine
through it, cleanses it immediately.
Water-casks ought to be charred inside, whereby no fermentable stuff
will be extracted from the wood. British ships, however, are now
commonly provided with iron tanks for holding their water in long
voyages.
PYRITES, is the native bisulphuret of iron. Copper pyrites, called
vulgarly mundick, is a bisulphuret of copper.
PYRO-ACETIC SPIRIT. (_Esprit pyro-acétique_, _Acétone_, Fr.;
_Brennzlicher Essiggeist_, _Mesit_, Germ.) This liquid was discovered
and described by Chenevix long before _pyrolignous spirit_ was known. It
may be obtained by subjecting to dry distillation the acetates of
copper, lead, alkalis, and earths; and as it is formed especially during
the second half of the process, the liquor which comes over then should
be set apart, separated by decantation from the empyreumatic oil, and
distilled a second time by the heat of a water-bath. The fine light
fluid which now comes over first, is to be rectified along with
carbonate of potassa, or chloride of calcium. As pyro-acetic spirit
usually retains, even after repeated distillations, a disagreeable
empyreumatic smell, like garlic, a little good bone-black should be
employed in its final rectification. According to Reichenbach,
pyro-acetic spirit may be extracted in considerable quantity from beech
tar. (See the next article.) The spirit thus prepared, is a colourless
limpid liquid, of an acrid and burning taste at first, but afterwards
cooling; of a penetrating aromatic smell, different from that of
alcohol; of the spec. gravity 0·7921 at 60° F., boiling at 132° F., and
remaining fluid at 5°. It consists ultimately of--carbon, 62·148;
hydrogen, 10·453; oxygen, 27·329; or, of 1 proportion of carbonic acid +
2 prop. of olefiant gas + 1 prop. of water; or, 1 prop. of acetic
acid--1 prop. of carbonic acid. According to another view, it is
composed of, 51·52 parts of concentrated acetic acid, and 48·488 of oil
of wine, being double of the quantity in acetic ether. It is very
combustible, and burns with a brilliant flame, without smoke. When
treated by chlorine, it loses an atom of its hydrogen, and absorbs 2
atoms of chlorine. It is soluble in water, alcohol, ether, and is not
convertible into ether by strong sulphuric acid. It is used for
dissolving the resins commonly called gums, with which the bodies of
hats are stiffened.
PYROLIGNOUS ACID. In addition to what has been said under ACETIC ACID, I
shall here describe the process as conducted upon a great scale at an
establishment near Manchester. The retorts are of cast iron, 6 feet
long, and 3 feet 8 inches in diameter. Two of these cylinders are heated
by one fire, the flame of which plays round their sides and upper
surface; but the bottom is shielded by fire-tiles from the direct action
of the fire. 2 cwts. of coals are sufficient to complete the
distillation of one charge of wood; 36 imperial gallons of crude
vinegar, of specific gravity 1·025, being obtained from each retort. The
process occupies 24 hours. The retort-mouth is then removed, and the
ignited charcoal is raked out for extinction into an iron chest, having
a groove round its edges, into which a lid is fitted.
When this pyrolignous acid is saturated with quicklime, and distilled,
it yields one per cent. of pyroxilic spirit (sometimes called naphtha);
which is rectified by two or three successive distillations with
quicklime.
The tarry deposit of the crude pyrolignous acid, being subjected to
distillation by itself, affords a crude pyro-acetic ether, which may
also be purified by re-distillation with quicklime, and subsequent
agitation with water.
The pyrolignite of lime, is made by boiling the pyrolignous acid in a
large copper, which has a sloping spout at its lip, by which the tarry
scum freely flows over, as it froths up with the heat. The fluid
compound thus purified, is syphoned off into another copper, and mixed
with a quantity of alum equivalent to its strength, in order to form the
red liquor, or acetate of alumina, of the calico-printer. The acetate of
lime, and sulphate of alumina and potash, mutually decompose each other;
with the formation of sulphate of lime, which falls immediately to the
bottom.
M. Kestner, of Thann, in Alsace, obtains, in his manufactory of
pyrolignous acid, 5 hectolitres (112 gallons imperial, nearly,) from a
cord containing 93 cubic feet of wood. The acid is very brown, much
loaded with tar, and marks 5° Baumé; 220 kilogrammes of charcoal are
left in the cylinders; 500 litres of that brown acid produce, after
several distillations, 375 of the pyrolignous acid of commerce,
containing 7 per cent. of acid, with a residuum of 40 kilogrammes of
pitch. For the purpose of making a crude acetate of lead (pyrolignite),
he dries pyrolignite of lime upon iron plates, mixes it with the
equivalent decomposing quantity of sulphuric acid, previously diluted
with its own weight of water, and cooled; and transfers the mixture as
quickly as possible into a cast-iron cylindric still, built horizontally
in a furnace; the under half of the mouth of the cylinder being always
cast with a semicircle of iron. The acetic acid is received into large
salt-glazed stone bottles. From 100 parts of acetate of lime, he obtains
133 of acetic acid, at 38° Baumé. It contains always a little sulphurous
acid from the reaction of the tar and the sulphuric acid.
[Illustration: 929, 930]
The apparatus represented in _figs._ 929. and 930. is a convenient
modification of that exhibited under acetic acid, for producing
pyrolignous acid. _Fig._ 929. shows the furnace in a horizontal section
drawn through the middle of the flue which leads to the chimney. _Fig._
930. is a vertical section taken in the dotted line x, x, of _fig._ 929.
The chest _a_ is constructed with cast-iron plates bolted together, and
has a capacity of 100 cubic feet. The wood is introduced into it through
the opening _b_, in the cover, for which purpose it is cleft into
billets of moderate length. The chest is heated from the subjacent grate
_c_, upon which the fuel is laid, through the fire-door _d_. The flame
ascends spirally through the flues _e_, _e_, round the chest, which
terminate in the chimney _f_. An iron pipe _g_ conveys the vapours and
gaseous products from the iron chest to the condenser. This consists of
a series of pipes laid zigzag over each other, which rest upon a
framework of wood. The condensing tubes are enclosed in larger pipes
_i_, _i_; a stream of cold water being caused to circulate in the
interstitial spaces between them. The water passes down from a trough
_k_, through a conducting tube _l_, enters the lowest cylindrical case
at _m_, flows thence along the series of jackets _i_, _i_, _i_, being
transmitted from the one row to the next above it, by the junction tubes
_o_, _o_, _o_, till at _p_ it runs off in a boiling-hot state. The
vapours proceeding downwards in an opposite direction to the cooling
stream of water, get condensed into the liquid state, and pass off at
_q_, through a discharge pipe, into the first close receiver _r_, while
the combustible gases flow off through the tube _s_, which is provided
with a stopcock to regulate the magnitude of their flame under the
chest. As soon as the distillation is fully set agoing, the stopcock
upon the gas-pipe is opened; and after it is finished, it must be shut.
The fire should be supplied with fuel at first, but after some time the
gas generated keeps up the distilling heat. The charcoal is allowed to
cool during 5 or 6 hours, and is then taken out through an aperture in
the back of the chest, which corresponds to the opening _u_, _fig._
929., in the brickwork of the furnace. About 60 per cent. of charcoal
may be obtained from 100 feet of fir-wood, with a consumption of as much
brush-wood for fuel.
Stoltze has ascertained, by numerous experiments, that one pound of wood
yields from 6 to 7-1/2 ounces of liquid products; but in acetic acid it
affords a quantity varying from 2 to 5, according to the nature of the
wood. Hard timber, which has grown slowly upon a dry soil, gives the
strongest vinegar. White birch and red beech afford per pound 7-1/3
ounces of wood vinegar, 1-1/3 ounce of combustible oil, and 4 ounces of
charcoal. One ounce of that vinegar saturates 110 grains of carbonate of
potassa. Red pine yields per pound 6-1/2 ounces of vinegar, 2-1/4 ounces
of oil, 3-3/4 ounces of charcoal; but one ounce of the vinegar saturates
only 44 grains of carbonate of potassa, and has therefore only
two-fifths of the strength of the vinegar from the birch. An ounce of
the vinegar from the white beech, holly oak (_Ilex_), common ash, and
horse chesnut, saturates from 90 to 100 grains of the carbonate. In the
same circumstances, an ounce of the vinegar of the alder and white pine
saturates from 58 to 60 grains.
PYROLIGNOUS or PYROXILIC SPIRIT, improperly called naphtha. This is
employed, as well as pyroacetic ether, to dissolve the sandarach,
mastic, and other resinous substances, which, under the name of gums,
are used for stiffening the bodies of hats. I have already described, in
the article PYROLIGNOUS ACID, how this spirit is obtained. Berzelius has
found that the crude spirit may be best purified by agitating it with a
fat oil, in order to abstract the empyreumatic oil; then to decant the
spirit, distil it, first with fresh calcined charcoal, and next with
chloride of calcium. The pyrolignous spirit, thus purified, is
colourless, and limpid like alcohol; has an ethereous smell, somewhat
resembling that of ants. Its taste is hot, and analogous to that of oil
of peppermint. Its specific gravity, by my experiments, is 0·824. It
readily takes fire, and burns with a blue flame, without smoke. It
combines with water in any proportion; a property which distinguishes it
from pyroacetic ether and spirit.
It is not easy to say what is the real chemical nature of pyroxilic
spirit. There is no ultimate analysis of it that can be depended upon.
The properties of the spirit examined by MM. Marcet and Macaire, differ
from those of our spirit, in refusing to combine with water, like
alcohol. The article on sale in this country readily unites with water,
and in all proportions with alcohol.
PYROMETER, is the name of an instrument for measuring high degrees of
heat above the range of the mercurial thermometer. Wedgewood’s is the
one commonly referred to by writers upon porcelain and metallurgy; but a
better one might be easily contrived.
PYROPHORUS, is the generic name of any chemical preparation, generally a
powder, which inflames spontaneously when exposed to the air.
PYROTECHNY. See FIRE-WORKS.
PYROXILINE, is a name which I have ventured to give to a substance
detected in pyroxilic spirit, by Mr. Scanlan, while residing in Dublin,
and therefore called by him _Eblanin_. I am indebted to that ingenious
chemist for the following facts.
If potash water be added to raw wood-spirit (_pyrolignous_), as long as
it throws down any thing, a precipitate is produced, which is
_pyroxiline_, mixed with tarry matter. This precipitate is to be
collected on a filter cloth, and submitted to strong pressure between
folds of blotting-paper; it is next to be washed with cold alcohol,
spec. grav. 0·840, in order to free it from any adhering tarry matter;
when the pyroxiline is left nearly pure. If it be dissolved in boiling
alcohol, or hot oil of turpentine, it crystallizes regularly on cooling,
in right square prisms, of a fine yellow colour, that look opaque to the
naked eye, but when examined under the microscope, have the transparency
and colour of ferroprussiate of potash. Its turpentine solution affords
crystals of a splendid orange-red colour, having the appearance of
minute plates, whose form is not discernible by the naked eye, but when
examined by the microscope, they are seen to be thin right rectangular
prisms. The orange-red colour is only the effect of aggregation; for
when ground to powder, these crystals become yellow; and under the
microscope, the difference in colour between the two is very slight. Its
melting point is 318° F. It sublimes at 300° in free air; heated in a
close tube in a bath of mercury, it emits vapour at 400°; it then begins
to decompose, and is totally decomposed at 500°. Sulphuric acid
decomposes it, producing a beautiful blue colour, which passes into
crimson, as the acid attracts water from the atmosphere, and it totally
disappears on plentiful dilution with water, leaving carbon of a
dirty-brown colour. Its alcoholic or turpentine solution imparts a
permanent yellow dye to vegetable or animal matter.
Pyroxiline consists, according to the analysis of Drs. Apjohn and
Gregory, of--carbon, 75·275; hydrogen, 5·609; oxygen, 19·116, in 100
parts.