Gun powder

Gunpowder, also known as black powder, is the earliest known chemical explosive. It is a mixture of sulfur, charcoal, and potassium nitrate (saltpeter). The sulfur and charcoal act as fuels, and the saltpeter is an oxidizer. Because of its burning properties and the amount of heat and gas volume that it generates, gunpowder has been widely used as a propellant in firearms, as a pyrotechnic composition in fireworks and as a blasting powder in quarrying, mining, and road building. Black powder firearms are in limited use today in hunting, shooting, and without bullets, in historical reenactments. Black powder has been replaced for most industrial uses by high explosives such as dynamite.

Black powder is assigned the UN number UN0027 and has a hazard class of 1.1D. It has a flash point of approximately 427–464 °C (801–867 °F). The specific flash point may vary based on the specific composition of the gunpowder. Gunpowder's specific gravity is 1.70–1.82 (mercury method) or 1.92–2.08 (pycnometer), and it has a pH of 6.0–8.0.

Gunpowder is classified as a low explosive because of its relatively slow decomposition rate and consequently low brisance. Low explosives deflagrate (i.e., burn) at subsonic speeds, whereas high explosives detonate, producing a supersonic wave. Ignition of the powder packed behind a bullet must generate enough pressure to force it from the muzzle at high speed, but not enough to rupture the gun barrel. Gunpowder thus makes a good propellant, but is less suitable for shattering rock or fortifications. Gunpowder was widely used to fill artillery shells and in mining and civil engineering to blast rock until the second half of the 19th century, when the first high explosives were put into use. Gunpowder is no longer used in modern explosive military warheads, nor is it used as main explosive in mining operations due to its cost relative to that of newer alternatives such as ammonium nitrate/fuel oil (ANFO). Black powder is still used as a delay element in various munitions where its slow-burning properties are valuable.

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