The Chemistry of Powder and Explosives - Sciencemadness Dot Org

FLASHLESS CHARGES AND FLASHLESS POWDER 323
at night disclose the position of the gun to the enemy. When a
large gun is fired, there is a large and dazzlingly bright muzzle
flash, from a 12-inch gun for example a white-hot flame 150 feet
or more in length. The light from such a flame reflects from the
heavens at night and is visible for a distance of as much as 30
miles, much farther than the sound from the gun may be heard.
The enemy by the use of appropriate light-ranging apparatus
may determine the position of the flash, and may undertake to
bombard and destroy the battery from a great distance.
Smokeless powder, burning in the chamber of the gun at the
expense of its own combined oxygen, produces gas which contains
hydrogen, carbon monoxide, carbon dioxide, etc., and this
gas, being both hot and combustible, takes fire when it emerges
from the muzzle and comes into contact with the fresh oxygen
supply of the outer air. One part of the brilliancy of the flash is
the result of the emergent gas being already preheated, often to
a temperature at which it would be visible anyway, generally to a
point far above the temperature of its inflammation in air. In
thinking about this latter temperature, it is necessary to take
account of the fact that, other things being equal, a small cloud
of gas from a small gun loses its temperature more quickly and
becomes completely mixed with the air more rapidly than a large
cloud of gas from a large gun. The gas emerging from a small
gun would need to be hotter in the first place if it is to inflame
than gas of the same composition emerging from a large gun. It
is for this reason perhaps that it is easier to secure flashless discharges
with guns of small caliber (not over 6 inch) than with
those of major caliber.
There are four ways, distinguishably different in principle, by
which flashlessness has been secured, namely,
(1) by the addition to the charge of certain salts, particularly
potassium chloride or potassium hydrogen tartarate, or by the
use of powdered tin or of some other substance which, dispersed
throughout the gas from the powder, acts as an anti-oxidant and
prevents its inflammation; -
(2) by incorporating carbonaceous material in the smokeless
powder, by which means the composition of the gas is altered and
22 Cf. Demougin, Mem. poudres, 25, 130 (1932-33); Fauveau and Le
Paire, ibid., 25, 142 (1932-33); Prettre, ibid., 25, 160, 169 (1932-33).