Density

The density or specific gravity of gunpowder is one of its most important properties. In the form of dust, the velocity of combustion increases rapidly with the density up to about 1.60, when it decreases. In grained powder the velocity of combustion decreases as the density increases. For English or American powder this velocity is about four-tenths of an inch per second. For French and most of the continental powders, which are le dense than the English, it is about forty-eight-hundredths of an inch. The excellent preservative qualities of English and American powders are largely due to their high densities,—the standard being about 1.75. A certain degree of density is absolutely e ential to grain powder to prevent the inflamed gases from penetrating the pores of the powder and flashing off the whole ma to the destruction of the gun. In the manufacture of powder the density depends, first, upon the amount of trituration to which the ingredients are subjected in the incorporating mill; second, upon the pre ure employed to form the cake; and, third, upon the degree of moisture it contains when subjected to these operations, particularly the last. The pre ure-gauge is not a reliable measure of the density given to a powder, though a good indication of the hardne , with which density must not be confounded. Dry powder meal offers a great resistance to compre ion, but becomes very hard,—the work being consumed in consolidating the surface particles. To obtain uniform density a certain amount of moisture is nece ary to a ist the particles in their movement. As much as 6 per cent. of moisture is used in making prismatic powder.