ust be as dry
as possible, and the latter should not contain more than .6 per cent. of
mineral matter and not more than 10 per cent. of soluble nitro-cellulose,
and a nitrogen content of not less than 12.5 per cent. The dry gun-cotton
(about 1 per cent. of moisture) is placed in an incorporating tank, which
consists of a brass-lined box, some of the acetone is added, and the
machine (Fig. 29), is started; after some time the rest of the acetone is
added (20 per cent. in all) and the paste kneaded for three and a half
hours. At the end of this time the Vaseline is added, and the kneading
continued for a further three and a half hours. The kneading machine (Fig.
29) consists of a trough, composed of two halves of a cylinder, in each of
which is a shaft which carries a revolving blade. These blades revolve in
opposite directions, and one makes about half the number of revolutions of
the other. As the blades very nearly touch the bottom of the trough, any
material brought into the machine is divided into two parts, kneaded
against the bottom, then pushed along the blade, turned over, and
completely mixed. During kneading the acetone gradually penetrates the
mixture, and dissolves both the nitro-cellulose and nitro-glycerine, and a
uniform dough is obtained which gradually assumes a buff colour. During
kneading the mass becomes heated, and therefore cold water is passed
through the jacket of the machine to prevent heating the mixture above the
normal temperature, and consequent evaporation of the acetone. The top of
the machine is closed in with a glass door, in order to prevent as far as
possible the evaporation of the solvent. When the various ingredients are
formed into a homogeneous mass, the mixture is taken to the press house,
where in the form of a plastic mass it is placed in cylindrical moulds.
The mould is inserted in a specially designed press, and the cordite paste
forced through a die with one or more holes. The paste is pressed out by
hydraulic pressure, and the long cord is wound on a metal drum (Fig. 38),
or cut into lengths; in either case the cordite is now sent to the drying
houses, and dried at a temperature of about 100 deg. F. from three to fourteen
days, the time varying with the size. This operation drives off the
acetone, and any moisture the cordite may still contain, and its diameter
decreases somewhat. In case of the finer cordite, such as the rifle
cordite, the next operation is blending. This proce