[Illustration: FIG. 23.--VESSEL FOR NITRATING COTTON OR PAPER.]

The nitrating apparatus of White and Schupphaus (U.S.P., No. 418, 237, 89)
Mr Field considers to be both novel and excellent. The cage (Fig. 24),
with its central perforated cylinder (Fig. 25), is intended to ensure the
rapid and perfect saturation of the tissue paper used for nitrating. The
patentees say that no stirring is required with their apparatus. This,
says Mr Field, might be true when paper is used, or even cotton, when the
temperature of nitration is from 30° to 35° C., but would not be true if
the temperature were raised to 50° to 55° C. The process is as follows:--
The paper is nitrated in the cage (Fig. 25), the bottom of which is formed
by the flanged plate C, fastened to the bottom of the internal cylinder B.
After nitration the cage is carried to a wringer, which forms the basket,
and the acids removed. Finally, the cage is taken to a plunge tank, where
the paper is removed from the cage by simply pulling out the central
perforated cylinder B. Fig. 26 shows the nitrating pot, with its automatic
cover. The plunge tank is shown in plan and section in Figs. 28 and 29.
This apparatus is suitable for the nitration of cotton fibre in bulk at
high or low temperatures. Other methods that have been patented are
Mowbray's (U.S.P., No. 434, 287), in which it is proposed to nitrate paper
in continuous lengths, and Hyatt's (U.S.P., No. 210, 611).

[Illustration: FIG. 24.--CENTRAL PERFORATED CYLINDER.]

[Illustration: FIG. 25.--THE CAGE. WHITE AND SCHUPPHAUS' NITRATING
APPARATUS.]

[Illustration: FIG. 26.--CELLULOID NITRATING POT.]

[Illustration: FIG. 27.--ANOTHER VIEW.]