n the manufacture of the gelatine
explosives should be as free as possible from gun-cotton, otherwise little
lumps of undissolved nitro-cotton will be left in the finished gelatine.
The non-nitrated or unconverted cotton should also be very low, in fact
considerably under 1/2 per cent.

The nitro-cotton and the nitro-glycerine used should always be tested
before use by the heat test, because if they do not separately stand this
test, it cannot be expected that the gelatine made from them will do so.
It often occurs, however, that although both the ingredients stand this
test separately before being mixed, that after the process of manufacture
one or other or both fail to do so.

The nitro-cotton most suitable for gelatine making is that which has been
finely pulped. If it is not already fine enough, it must be passed through
a fine brass wire sieve. It will be found that it requires to be rubbed
through by hand, and will not go through at all if in the least degree
damp. It is better, therefore, to dry it first. The percentage of nitrogen
in the nitrated cotton should be over 11 per cent. It should be as free as
possible from sand or grit, and should give but little ash upon ignition,
not more than 0.25 per cent. The cotton, which is generally packed wet in
zinc-lined wooden boxes, will require to be dried, as it is very essential
indeed that none of the materials used in the manufacture of gelatine
should contain more than the slightest trace of water. If they do, the
gelatine subsequently made from them will most certainly exude, and become
dangerous and comparatively valueless. It will also be much more difficult
to make the nitro-cotton dissolve in the nitro-glycerine if either
contains water.

In order to find out how long any sample of cotton requires to be dried, a
sample should be taken from the centre of several boxes, well mixed, and
about 1,000 grms. spread out on a paper tray, weighed, and the whole then
placed in the water oven at 100 deg. C., and dried for an hour or so, and
again weighed, and the percentage of moisture calculated from the loss in
weight. This will be a guide to the time that the cotton will probably
require to be in the drying house. Samples generally contain from 20 to 30
per cent. of water. After drying for a period of forty-eight hours, a
sample should be again dried in the oven at 100 deg. C., and the moisture
determined, and so on at intervals until the bulk of the cotton is found