tank, sufficiently elevated on iron
standards to allow room for the small gauge tanks and moulding apparatus
below. It holds the contents of one poacher (18 cwt.), and is provided
with revolving arms to keep the pulp stirred up, so that it may be
uniformly suspended in water.

Recently a new process, invented by J.M. and W.T. Thomson (Eng. Pat. No.
8,278, 1903), has been introduced at the Waltham Abbey Factory. The object
of this invention is the removal of the acids of nitration from the
nitrated material after the action has been completed, and without the aid
of moving machinery, such as presses, rollers, centrifugals, and the like.
The invention consists in the manufacture of nitrated celluloses by
removing the acids from the nitrated cellulose directly by displacement
without the employment of either pressure or vacuum or mechanical
appliances of any kind, and at the same time securing the minimum dilution
of the acids. It was found that if water was carefully run on to the
surface of the acids in which the nitro-cellulose is immersed, and the
acids be slowly drawn off at the bottom of the vessel, the water displaces
the acid from the interstices of the nitro-cellulose without any
undesirable rise in temperature, and with very little dilution of the
acids. By this process almost the whole of the acid is recovered in a
condition suitable for concentration, and the amount of water required for
preliminary washing is very greatly reduced. The apparatus which is used
for the purpose consists of a cylindrical or rectangular vessel
constructed with a perforated false bottom and a cock at its lowest point
for running off the liquid. Means are also provided to enable the
displacing water to be run quietly on to the surface of the nitrating
acids.[A]

[Footnote A: In a further patent (Eng. Pat. 7,269, 1903, F.L. Natham),
J.M. Thomson and W.T. Thomson propose by use of alcohol to replace the
water, used in washing nitro-cellulose, and afterward to remove the
alcohol by pressing and centrifuging.]

The apparatus is shown in Fig. 2O, side elevation, and in Fig. 21 a plan
of the nitrating vessel and its accessories is given. In Fig. 20 is shown
in sectional elevation one of the trough devices for enabling liquids to
be added to those in the nitrating vessel without substantial disturbance.

[Illustration: FIG. 20.--SECTIONAL ELEVATION OF THOMSON'S APPARATUS, _a_,
Tank; _b_, False Bottom; _c_, Bottom; _c'_, Ribs; _d_, Draini