_
Soluble cotton (collodion) 99.118 per cent.| Nitrogen = 11.64 per cent.
Gun-cotton 0.642 " _|
Non-nitrated cotton 0.240 "
Total ash 0.25 "

It should contain as little non-nitrated or unconverted cotton and as
little gun-cotton as possible, as they are both insoluble in nitro-
glycerol. The quality and composition of any sample of collodion-cotton
can be quickly inferred by determining the percentage of nitrogen by means
of the nitrometer and the use of the solubility test.[A] A high nitrogen
content coupled with a high solubility is the end to be aimed at; a high
nitrogen with a low solubility shows the presence of gun-cotton, and a low
nitrogen, together with a low solubility, the presence of unnitrated
cotton. Where complete solubility is essential and the percentage of
nitrogen less important, Dr Lunge recommends nitration with a mixture of
equal parts of sulphuric and nitric acids containing from 19 to 20 per
cent. of water.

[Footnote A: See Analysis of Explosives.]

Mr T.R. France claims to have invented some improvements in the
manufacture of soluble nitro-cellulose. His object has been to produce an
article as uniform as possible. His explanation of the imperfect action of
the acids is that, however uniform the mixed acids may be in strength and
proportions, and however carefully the operations of nitrating, &c., may
be conducted, there are variable elements found in different samples of
cotton. The cotton fibre has for its protection a glazed surface. It is
tubular and cellular in structure, and contains a natural semi-fluid
substance composed of oil or gum, which varies in nature according to the