these being pulping. Having traced the cause of its instability to the
presence of substances caused by the action of the nitric acid on the
resinous or fatty substances contained in the cotton fibre, he succeeded
in eliminating them, by boiling the nitro-cotton in water, and by a
thorough washing, after pulping the cotton in poachers.

Although gun-cottons are generally spoken of as nitro-celluloses, they are
more correctly described as cellulose nitrates, for unlike nitro bodies of
other series, they do not yield, or have not yet done so, amido bodies, on
reduction with nascent hydrogen.[A] The equation of the formation of
gun-cotton is as follows:--

2(C_{6}H_{10}O_{5}) + 6HNO_{3} = C_{12}H_{14}O_{4}(NO_{3})_{6} + 6OH_{2}.
Cellulose. Nitric Acid. Gun-Cotton. Water.

The sulphuric acid used does not take part in the reaction, but its
presence is absolutely essential to combine with the water set free, and
thus to prevent the weakening of the nitric acid. The acid mixture used at
Waltham Abbey consists of 3 parts by weight of sulphuric acid of 1.84
specific gravity, and 1 part of nitric acid of 1.52 specific gravity. The
same mixture is also used at Stowmarket (the New Explosive Company's
Works). The use of weaker acids results in the formation of collodion-
cotton and the lower nitrates generally.

[Footnote A: "Cellulose," by Cross and Bevan, ed. by W.R. Hodgkinson, p.
9.]

The nitrate which goes under the name of gun-cotton is generally supposed
to be the hexa-nitrate, and to contain 14.14 per cent. of nitrogen; but a
higher percentage than 13.7 has not been obtained from any sample. It is