released. During the war the American Government placed orders for
68,000,000 such grenades as are here shown.]

[Illustration: © International Film Service, Inc.

WOMEN IN A MUNITION PLANT ENGAGED IN THE MANUFACTURE OF
TRI-NITRO-TOLUOL, THE MOST IMPORTANT OF MODERN HIGH EXPLOSIVES]

The active agent in all these explosives is the nitrogen atom in
combination with two oxygen atoms, which the chemist calls the "nitro
group" and which he represents by NO_{2}. This group was, as I have
said, originally used in the form of saltpeter or potassium nitrate, but
since the chemist did not want the potassium part of it--for it fouled
his guns--he took the nitro group out of the nitrate by means of
sulfuric acid and by the same means hooked it on to some compound of
carbon and hydrogen that would burn without leaving any residue, and
give nothing but gases. One of the simplest of these hydrocarbon
derivatives is glycerin, the same as you use for sunburn. This mixed
with nitric and sulfuric acids gives nitroglycerin, an easy thing to
make, though I should not advise anybody to try making it unless he has
his life insured. But nitroglycerin is uncertain stuff to keep and being
a liquid is awkward to handle. So it was mixed with sawdust or porous
earth or something else that would soak it up. This molded into sticks
is our ordinary dynamite.

If instead of glycerin we take cellulose in the form of wood pulp or
cotton and treat this with nitric acid in the presence of sulfuric we
get nitrocellulose or guncotton, which is the chief ingredient of
smokeless powder.