finally dried on a wide linen sheet, through which was forced air heated
to 60° C. The average yield from 100 parts of cotton was 165 parts of gun-
cotton. The strong pressings of the gun-cotton, while still impregnated
with acids, caused subsequent washings to be difficult and laborious.

~Granulation of Gun-Cotton.~--Gun-cotton is often required in the
granulated form for use either alone or with some form of smokeless
powder. This is done under the patent of Sir Frederick Abel in the
following manner:--The gun-cotton from the poacher is placed in a
centrifugal machine, very similar to the hydro-extractors before
mentioned, and used for wringing out the acids. In this machine it loses
water until it only contains 33 per cent., and is at the same time reduced
to a more or less fibrous state. It is then taken to the granulating room,
where it is first passed through sieves or perforations, which break up
the mass into little pieces like shot. The material is then transferred to
a revolving drum made of wood or stout leather, which is kept constantly
revolving for some time. The material is occasionally sprinkled with
water. The drum in turning, of course, carries the granules partially
round with it, but the action of gravity causes them to descend constantly
to the lowest point, and thus to roll over one another continually. The
speed of the drum must not be too rapid. None of the granules must be
carried round by centrifugal force, but it must be fast enough to carry
them some little distance up the side of the drum. After removal from the
drum the granules are dried upon shelves in the drying house.

Gun-cotton is also dissolved in acetone or acetic ether until it has taken
the form of a jelly. It is then rolled into thin sheets, and when dry cut
up into little squares. In the manufacture of smokeless powders from
nitro-cellulose, nitro-lignine, &c., the various substances are mixed with
the gun-cotton or collodion-cotton before granulating.