GUNPOWDERAlso known as black powder. An explosive extensively used for blasting purposes and for fireworks. It was introduced into Europe prior to 1250 and was the only propellant used in guns until 1870. It is now superseded for military uses by high explosives. Black powder deteriorates easily in air from the absorption of moisture. It is a mechanical mixture of potassium nitrate, charcoal, and sulfur, in the usual proportions of 75%, 15, and 10. More saltpeter increases the rate of burning; additional charcoal decreases the rate. A slow-burning powder for fireworks rockets may have only 54% saltpeter and 32 charcoal. Commercial black powder comes in grains of graded sizes and is glazed with graphite. The grain sizes are known as pebble powder, large-grain, fine-grain, sporting powder, mining powder, Spanish spherical powder, and cocoa powder. The potential energy of gunpowder is estimated at 500 ft • ton/lb (305,000 kg • m/kg), but the actual gun efficiency is less than 10% of this. A temperature of about 3712°F (2100°C) is produced by the explosive. Gunpowder is the slowest-acting of all the explosives, and it has a heaving, not a shattering, effect. Hence, it is effective for blasting and breaking up stone. Blasting powder is divided by Du Pont into two grades: A and B. The A powder contains saltpeter; the B powder contains nitrate of soda. The saltpeter concentration varies from 64 to 74% in commercial formulations. The other ingredients are the usual sulfur and charcoal. The B powder is not so strong or water-resistant as A powder, but is cheaper and is extensively used. Pellet powder is blasting powder made up in cylindrical cartridges for easier use in mining. White gunpowder is a powder in which the saltpeter is replaced by potassium chlorate. It is very sensitive and explodes with violence. It is used only for percussion caps and fireworks. Lesmok powder, used in 22-caliber cartridges, is composed of 15% black powder and 85 nitrocellulose.
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