A Manual of the Chemistry of the Carbon Compounds

298 THE CUBMISTBY OF
fresh acid mixture, and left there for forty-eight hours, It is then
again well squeezed, and washed for a long time with running water,
and lastly steeped again in a solution of potassium carbonate,
Gun-cotton thus manufactured will keep without ohange for
almost any length of time, and may be kept under water for safety's
sake; possessing, after drying, all its original properties.
It is insoluble in water, alcohol, and ether. It takes fire at 150°,
burning away rapidly, but without explosion; but when ignited in a
coufined space, or by percussion, it decomposes with a violent detonation,
the action of which equals that of five times its weight of gunpowder.
The products of its decomposition consist principally of
nitrogen, carbon monoxide, carbon dioxide, and water,
A different product is obtained by steeping cotton-wool in a warm
mixture of two parts of dry saltpetre and three parts of concentrated
sulphuric acid, for twenty-four hours; the substance thus formed is
called soluble gun-cotton, or collodion-wool; it is less explosive, and
readily soluble in a mixture of ether with a little absolute alcohol,
forming a clear solution called collodion, which, when left to evaporate,
dries up quickly to a thin, transparent, adhesive, waterproof membrane,
which is used in surgery as a covering for wounds and burns.
Collodion is also largely used in photography to cover glass-plates
with a transparent membrane containing silver-salts.
Collodion wool contains less NO8 than gun-cotton, but ite composition
is not exactly known; both compounds are reconverted into
cotton-wool by acting on them with a solution of a ferrous salt or
other reducing agents; hydroxyl replaces the group NO^ and the
latter oxidizes the ferrous salt, and nitric oxide is given off.
By the action of strong nitric acid upon paper, sawdust, flax, &c,
explosive bodies resembling gun-cotton are obtained.
Woody fibre does not contain free cellulose but in combination
with other bodies, Thus finely-divided pinewood (Pintts abies), after
being purified by exhausting it with very weak acetic acid, hot water,
aloohol, and ether (in order to remove colouring matter, resin, &c),
yields to an ammoniacal solution of cuprio oxide only a trace of
oelluloae. Its composition was found to be C8fHiQOn; on boiling it
with hydroohlorio acid, dextrose goes in solution, and an insoluble
residue of Lignost CjgHjgOji is left behind:—
f TT O .4- 9TT O — 9C* 1 TT O 4- O W O
Lignose is also insoluble in an ammoniacal solution of cupric
oxide, but is oonverted into cellulose on boiling it with weak nitric
acid; besides cellulose, other produots are formed, probably belonging
to the aromatic group, as by fusing lignose with caustic potash,
pyrocaUehin C6H8Oo, a body belonging to this group, is formed.
Pine-wood may therefore be regarded as a kmd of ether, containing
the radicals of grape-sugar, cellulose and pyrocateohin:—
0 - 2C9HV2O9 + CuHapu + C9H809