[Footnote B: Royal Gunpowder Factory.]

[Footnote C: Costs from £10 to £25 a ton. In his description of the
"Preparation of Cotton-waste for the Manufacture of Smokeless Powder," A.
Hertzog states that the German military authorities require a cotton which
when thrown into water sinks in two minutes; when nitrated, does not
disintegrate; when treated with ether, yields only 0.9 per cent. of fat;
and containing only traces of chlorine, lime, magnesia, iron, sulphuric
acid, and phosphoric acid. If the cotton is very greasy, it must be first
boiled with soda-lye under pressure, washed, bleached with chlorine,
washed, treated with sulphuric acid or HCl, again washed, centrifugated,
and dried; if very greasy indeed a preliminary treatment with lime-water
is desirable. See also "Inspection of Cotton-Waste for Use in the
Manufacture of Gun-cotton," by C.E. Munro, _Jour. Am. Chem. Soc._, 1895,
17, 783.]

~Drying the Cotton.~--This operation is performed in either of two ways.
The cotton may either be placed upon shelves in a drying house, through
which a current of hot air circulates, or dried in steam-jacketed
cylinders. It is very essential that the cotton should be as dry as
possible before dipping in the acids, especially if a wholly "insoluble"
nitro-cellulose is to be obtained. After drying it should not contain more
than 0.5 per cent. of moisture, and less than this if possible. The more
general method of drying the cotton is in steam-jacketed tubes, i.e.,
double cylinders of iron, some 5 feet long and 1-1/2 foot wide. The cotton
is placed in the central chamber (Fig. 10), while steam is made to
circulate in the surrounding jacket, and keeps the whole cylinder at a
high temperature (steam pipes may be coiled round the outside of an iron
tube, and will answer equally well). By means of a pipe which communicates