kage
of celluloid combs also exploded in the guard's van on one of the German
railways a few years ago. Although it is not an explosive under ordinary
circumstances, or even with a powerful detonator, considerable care should
be exercised in its manufacture.

~The Manufacture of Gun-Cotton.~--The method used for the manufacture of
gun-cotton is that of Abel (Spec. No. 1102, 20. 4. 65). It was worked out
chiefly at Stowmarket[A] and Waltham Abbey,[B] but has in the course of
time undergone several alterations. These modifications have taken place,
however, chiefly upon the Continent, and relate more to the apparatus and
machinery used than to any alteration in the process itself. The form of
cellulose used is cotton-waste,[C] which consists of the clippings and
waste material from cotton mills. After it has been cleaned and purified
from grease, oil, and other fatty substances by treatment with alkaline
solutions, it is carefully picked over, and every piece of coloured cotton
rag or string carefully removed. The next operation to which it is
submitted has for its object the opening up of the material. For this
purpose it is put through a carding machine, and afterwards through a
cutting machine, whereby it is reduced to a state suitable for its
subsequent treatment with acids, that is, it has been cut into short
lengths, and the fibres opened up and separated from one another.

[Footnote A: The New Explosive Co. Works.]

[Footnote B: Royal Gunpowder Factory.]

[Footnote C: Costs from L10 to L25 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 place