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_, Draining Outlet; _e_, Grid; _f_, Troughs, with Aprons _g_; _h_, Pipe, with Branches _h'_, leading to Troughs, _f_; _k'_, Outlet Pipe of the Sulphuric Acid Tank _k_; _l_, Water Supply Pipe; _m_, Pipe to supply of Nitrating Acids; _o_, Perforations of Trough _f_; _p_, Cock to remove Acid.]