of water. If it is
necessary to determine the nitro-glycerine quantitatively in an explosive,
the scheme on page 213 may be followed. Ether is the best solvent to use.
Nitrogen should be determined in the nitrometer.

~Gelatine Compounds.~--The simplest of these compounds is, of course,
blasting gelatine, as it consists of nothing but nitro-cotton and nitro-
glycerine, the nitro-cellulose being dissolved in the glycerine to form a
clear jelly, the usual proportions being about 92 per cent. of nitro-
glycerine to 8 per cent. nitro-cotton, but the cotton is found as high as
10 per cent. in some gelatines. Gelatine dynamite and gelignite are
blasting gelatines, with varying proportions of wood-pulp and saltpetre
(KNO_{3}) mixed with a thin blasting gelatine. The method of analysis is
as follows:--Weigh out 10 grms. of the substance, previously cut up into
small pieces with a platinum spatula, and place over calcium chloride in a
desiccator for some days. Reweigh. The loss equals moisture. This is
generally very small. Or Handy's method may be used. The dried sample is
then transferred to a small thistle-headed funnel which has been cut off
from its stem, and the opening plugged with a little glass wool, and round
the top rim of which a piece of fine platinum wire has been fastened, in
order that it may afterwards be easily removed from the Soxhlet tube. The
weight of this funnel and the glass wool must be accurately known. It is
then transferred to the Soxhlet tube and exhausted with ether, which
dissolves out the nitro-glycerine. The weighed residue must afterwards be
treated in a flask with ether-alcohol to dissolve out the nitro-cotton.

But the more expeditious method, and one quite as accurate, is to transfer
the dried gelatine to a conical Erlenmeyer flask of about 500 c.c.
capacity, and add 250 c.c. of a mixture of ether-alcohol (2 ether to 1
alcohol), and allow to stand overnight. Sometimes a further addition of
ether-alcohol is necessary. It is always better to add another 300 c.c.,
and leave for twenty minutes or so after the solution has been filtered
off. The undissolved portion, which consists of wood-pulp, potassium
nitrate, and other salts, is filtered off through a linen or paper filter,
dried and weighed.

~Solution.~--The ether-alcohol solution contains the nitro-cotton and the
nitro-glycerine in solution.[A] To this solution add excess of chloroform
(about 100 c.c. will be required), when the nitro-cel