The Chemistry of Powder and Explosives - Sciencemadness Dot Org

260 NITRIC ESTERS
nitrator which is equipped with twu paddles revolving vertically
in opposite directions and designed to thrust the cotton quickly
under the surface of the acid. For 32 pounds of cellulose a charge
of about 1500 pounds of mixed acid is used. This contains approximately
21% nitric acid, 63% sulfuric acid, and 16% water.
It may contain also a small amount, say 0.5%, of nitrous acid,
NO2 or N^O4, which, however, is calculated as being equivalent
to a like amount of water and is not reckoned as any part of the
nitrating total of actual nitric and sulfuric acids. The sulfuric
acid content of the nitrating acid is kept as constant as possible
in practice; the nitric acid content may vary somewhat, less than
1%, however, for slightly more nitric acid is necessary in warm
weather to offset the tendency toward denitration which exists
at that time. At the start the acid has a temperature of about
30°, the introduction of the cellulose requires about 4 minutes,
and the nitration is continued for 20 minutes longer while the
mixture is stirred mechanically with the paddles and the temperature
is kept between 30° and 34°. When the nitration is
complete, a valve in the bottom of the nitrator is opened and the
slurry is allowed to run into a centrifuge on the floor below.
Here the crude nitrocellulose is separated quickly from the spent
acid which is fortified for use again or, in part, goes to the acid
recovery plant. Wringer fires are by no means uncommon, especially
on damp days, for the air which is sucked through the acidsoaked
material in the centrifuge gives up its moisture to the
strong acid and dilutes it with the development of considerable
heat. The nitrated product is forked through an orifice in the
bottom of the wringer and falls into an immersion basin below,
where it is drowned by being mixed rapidly with a swiftly moving
stream of water. Thence it proceeds on its way down the guncotton
line where it is stabilized or purified and then prepared for
shipment or for use.
The crude nitrocellulose contains certain amounts of cellulose
sulfate, of nitrate of oxycellulose, and possibly of some cellulose
nitrate which is less stable than the ordinary, all of which are
capable of being hydrolyzed by long-continued boiling with
slightly acidified water. Guncotton requires a longer stabilizing
boil than pyrocellulose. After the boiling the acid is washed off
and removed from the nitrocellulose, yielding a product which is
now stabilized because it contains neither free acid nor compo-