when the product is to be used at high temperatures. By means of rollers
steam heated, the incorporation may be accomplished without the aid of a
volatile liquid, or the nitro-cellulose may be employed wet, the water
being removed after "solution."

It is advisable to use the cellulose nitrated only just enough to render
it suitable, in order to reduce the inflammability of the finished
product. Mr W. Allen, M.P., of Gateshead, proposed to use celluloid for
cartridge cases, and thus to lighten ammunition, and prevent jambing, for
the case will be resolved into gases along with the powder. Extractors
will also be done away with.

~Celluloid~ is an intimate mechanical mixture of pyroxyline (gun-cotton or
collodion-cotton) with camphor, first made by Hyatt, of Newark, U.S.A.,
and obtained by adding the pyroxyline to melted camphor, or by strongly
compressing the two substances together, or by dissolving the constituents
in an appropriate solvent, e.g., alcohol or ether, and evaporating to
dryness. A combination of the two latter methods, i.e., partial solution,
with pressure, is now usually adapted. The pyroxyline employed is
generally the tetra- and penta-nitrated cellulose, the hexa-nitrate
(gun-cotton) being but seldom used on account of its explosive properties.

Care is taken to prevent the formation of the hexa-nitrate by immersing
the cellulose in only moderately strong nitric acid, or in a warm mixture
of nitric and sulphuric acids. The paper, either in small pieces or in
sheets, is immersed for about twenty-five minutes in a mixture of 2 parts
of nitric acid and 5 parts of sulphuric acid, at a temperature of about
30° C., after which the nitrated cellulose is thoroughly washed with water
to remove the last traces of free acid, pressed, and whilst still moist,
mixed with the camphor.