The Chemistry of Powder and Explosives - Sciencemadness Dot Org

318 SMOKELESS POWDER
as the burning advances, and, other things in the gun being equal,
they produce gas at a rate which accelerates more rapidly and,
in consequence, gives a greater velocity to the projectile.
A progressive burning strip ballistitc was u^ed to s*t World War.
It consisted of a central thick strip or slab of ballistite, 50 r /c
FIGURE 79. Progressive Burning Colloided Smokeless Powder. 12-Inch
powder at different stages of its burning. A grain of 12-inch powder, such
as appears at the left, was loaded into a 75-mm. gun along with the usual
charge of 75-mm. powder (of the same form as the 12-inch grain but of
less web thickness). When the gun was fired, a layer of colloid having a
thickness equal to one-half the web of the 75-mm. powder was burned off
from every grain in the gun. This consumed the 75-mm. powder completely.
The 12-inch grain was extinguished when thrown from the muzzle
of the gun; it was picked up from the ground—and is the second grain
in the above picture. The next grain was shot twice from a 75-mm. gun,
the last grain three times. After three shootings, the perforations are so
large that a fourth shooting would cause them to meet one another, and
the grain to fall apart, leaving slivers.
nitroglyccrin and 50% soluble nitrocellulose, made without volatile
solvent, and sandwiched between two thin strips of powder
made, without volatile solvent, from 50% soluble nitrocellulose
and 50% crystalline dinitrotoluene. The two compositions were
rolled to the desired thicknesses separately between warm rolls,
and were then combined into the laminated product by pressing
between warm rolls. The outer layers burned relatively slowly
with a temperature of about 1500°; the inner slab burned rapidly
with a temperature of about 3000°.