GUNPOWDER.
Gunpowder is a very intimate mixture of potassium nitrate (nitre), charcoal, and sulphur, and generally consists of the following proportions:
Nitre, 75 parts; charcoal, 15 parts; sulphur, 10 parts.
The following processes are used in its manufacture:
(1) Mixing the ingredients; (2) incorporating or "milling"; (3) breaking down the mill-cake; (4) pressing; (5) granulating; (6) dusting; (7) glazing; (8) second dusting; (9) stoving or drying; (10) finishing.
Good gunpowder should be composed of hard angular grains which do not soil the fingers, and should have a perfectly uniform dark-gray color. When new, it should be free from dust, and a gramme of it flashed on a copper or porcelain plate should leave no residue or foulness.
It should give the required initial velocity to the projectile, and produce not more than the maximum strain upon the gun.
When exposed to air of average dryness, it should not absorb more than 0.5 to 1.5 per cent of water. In damp air it absorbs more and deteriorates. Its exploding-point is 560° F.