lycerine under the influence of heat, a
temperature of about 50 deg. C. being required. At lower temperatures the
dissolution is very imperfect indeed; and after the materials have been
left in contact for days, the threads of the cotton can still be
distinguished. The insoluble form or gun-cotton is entirely _insoluble_ in
nitro-glycerine. It can, however, be made to dissolve[A] by the aid of
acetone or acetic ether. Both or rather all the forms of nitro-cellulose
can be dissolved in acetone or acetic ether. They also dissolve in
concentrated sulphuric acid, and the penta-nitrate in nitric acid at about
80 deg. or 90 deg. C.

[Footnote A: Or rather to form a transparent jelly.]

The penta-nitrate may be obtained in a pure state by the following
process, devised by Eder:--The gun-cotton is dissolved in concentrated
nitric acid at 90 deg. C., and reprecipitated by the addition of concentrated
sulphuric acid. After cooling to 0 deg. C., and mixing with a larger volume of
water, the precipitated nitrate is washed with water, then with alcohol,
dissolved in ether-alcohol, and again precipitated with water, when it is
obtained pure. This nitrate is soluble in ether-alcohol, and slightly in
acetic acid, easily in acetone, acetic ether, and methyl-alcohol,
insoluble in alcohol. Strong potash (KOH) solution converts into the
di-nitrate C_{12}H_{18}O_{8}(NO_{3})_{2}. The hexa-nitrate is not soluble
in acetic acid or methyl-alcohol.

The lower nitrates known as the tetra- and tri-nitrates are formed
together when cellulose is treated with a mixture of weak acids, and
allowed to remain in contact with them for a very short time (twenty
minutes). They cannot be separated from one another, as they all dissolve
equally in ether-alcohol, acetic ether, acetic acid, methyl-alcohol,
acetone, amyl acetate, &c.

As far as the manufacture of explosive bodies is concerned, the two forms
of nitro-cellulose used and manufactured are gun-cotton or the hexa-
nitrate (once regarded as tri-nitro-cellulose), which is also known as
insoluble gun-cotton, and the soluble form of gun-cotton, which is also
known as collodion, and consists of a mixture of several of the lower
nitrates. It is probable that it chiefly consists, however, of the next
highest nitrate to gun-cotton, as the theoretical percentage of nitrogen
for this body,. the penta-nitrate, is 12.75 per cent., and analyses of
commercial collodion-cotton, entirely soluble in ether-alcohol,