17. Why should powder be free from dust?
Because the dust fills up the intervals between the grains, and forming a compact mass, retards combustion.
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18. To what special purpose are large and small grained powders applied?
The large for cannon, and the small for small arms.
19. How is the size of the grain for each kind of powder tested?
By means of sieves or gauges.
20. How many grains of powder are in 10 grs. Troy weight?
Cannon, 150; Musket, 2,000 to 2,500; and Rifle, 12,000 to 15,000.
21. What is the object in glazing powder?