-The sample is
dried in the oven as above for fifteen minutes, and exposed for two hours
to the air. The test as above for compressed gun-cotton is then applied.

~C. Cordite~ must stand a temperature of 180 deg. F. for fifteen minutes. The
sample is prepared as follows:--Pieces half an inch long are cut from one
end of every stick selected for the test: in the case of the thicker
cordites, each piece so cut is further subdivided into about four
portions. These cut pieces are then passed once through the mill, the
first portion of material which passes through being rejected on account
of the possible presence of foreign matter from the mill. The ground
material is put on the top sieve of the nest of sieves, and sifted. That
portion which has passed through the top sieve and been stopped by the
second is taken for the test. If the mill is properly set, the greater
portion of the ground material will be of the proper size. If the volatile
matter in the explosive exceeds 0.5 per cent., the sifted material should
be dried at a temperature not exceeding 140 deg. F, until the proportion does
not exceed 0.5 per cent. After each sample has been ground, the mill must
be taken to pieces and carefully cleaned. The sieves used consist of a
nest of two sieves with holes drilled in sheet copper. The holes in the
top sieve have a diameter = 14 B.W.G., those in the second = 21 B.W.G.

If too hard for the mill, the cordite may be softened by exposure to the
vapour of acetone,[A] or reduced, to the necessary degree of subdivision
by means of a sharp moderately-coarse rasp. Should it have become too soft
in the acetone vapour for the mill, it should be cut up into small pieces,
which may be brought to any desired degree of hardness by simple exposure
to air. Explosives which consist partly of gelatinised collodion-cotton,
and partly of ungelatinised gun-cotton, are best reduced to powder by a
rasp, or softened by exposure to mixed ether and alcohol vapour at a
temperature of 40 deg. F. to 100 deg. F.

[Footnote A: Mr W. Cullen _(Jour. Soc. Chem. Ind._, Jan. 31, 1901) says:--
"Undoubtedly the advent of the horny smokeless powders of modern times has
made it a little difficult to give the test the same scope as it had when
first introduced." As a rule a simple explanation can be found for every
apparently abnormal result, and in the accidental retention of a portion
of the solvent used in the manufacture, will frequently be found an
expla