Gunpowder, also known since the late 19th century as black powder, was the first chemical explosive and the only one known until the mid-1800s. It is a mixture of sulfur, charcoal, and potassium nitrate (saltpeter)—with the sulfur and charcoal acting as fuels, while the saltpetre works as 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 and as a pyrotechnic composition in fireworks.
Gunpowder was, according to prevailing academic consensus, invented in the 9th century in China, and the earliest record of a written formula for gunpowder appears in the 11th century Song Dynasty text, Wujing Zongyao. This discovery led to the invention of fireworks and the earliest gunpowder weapons in China. In the centuries following the Chinese discovery, gunpowder weapons began appearing in the Arab world, Europe, and India. The technology spread from China through the Middle East, and then into Europe. The earliest Western accounts of gunpowder appear in texts written by English philosopher Roger Bacon in the 13th century.
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. Gunpowder's burning rate increases with pressure, so it will burst containers if contained but otherwise just burns in the open. 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 roughly until the second half of the 19th century, when the first high explosives (nitro-explosives) were discovered. 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.
History
Gunpowder was invented in China. Chinese military forces used gunpowder-based weapons (i.e. rockets, guns, cannons) and explosives (i.e. grenades and different types of bombs) against the Mongols when the Mongols attempted to invade and breach city fortifications on China's northern borders. After the Mongols conquered China and founded the Yuan Dynasty, they used the Chinese gunpowder-based weapons technology in their attempted invasion of Japan; they also used gunpowder to fuel rockets.
The mainstream scholarly consensus is that gunpowder was invented in China, spread through the Middle East, and then into Europe, although there is a dispute over how much the Chinese advancements in gunpowder warfare influenced later advancements in the Middle East and Europe. The spread of gunpowder across Asia from China is widely attributed to the Mongols. One of the first examples of Europeans encountering gunpowder and firearms is at the Battle of Mohi in 1241. At this battle the Mongols not only used gunpowder in early Chinese firearms but in the earliest grenades as well.
Composition and Characteristics
The term black powder was coined in the late 19th century, primarily in the United States, to distinguish prior gunpowder formulations from the new smokeless powders and semi-smokeless powders, in cases where these are not referred to as cordite. Semi-smokeless powders featured bulk volume properties that approximated black powder, but had significantly reduced amounts of smoke and combustion products.
Smokeless powder has different burning properties (pressure vs. time) and can generate higher pressures and work per gram. This can rupture older weapons designed for black powder. Smokeless powders ranged in colour from brownish tan to yellow to white. Most of the bulk semi-smokeless powders ceased to be manufactured in the 1920s.
Black powder is a granular mixture of
- a nitrate, typically potassium nitrate (KNO3), which supplies oxygen for the reaction;
- charcoal, which provides carbon and other fuel for the reaction, simplified as carbon (C);
- sulfur (S), which, while also serving as a fuel, lowers the temperature required to ignite the mixture, thereby increasing the rate of combustion.
Potassium nitrate is the most important ingredient in terms of both bulk and function because the combustion process releases oxygen from the potassium nitrate, promoting the rapid burning of the other ingredients. To reduce the likelihood of accidental ignition by static electricity, the granules of modern black powder are typically coated with graphite, which prevents the build-up of electrostatic charge.
Charcoal does not consist of pure carbon; rather, it consists of partially pyrolyzed cellulose, in which the wood is not completely decomposed. Carbon differs from charcoal. Whereas charcoal's autoignition temperature is relatively low, carbon's is much greater. Thus, a black powder composition containing pure carbon would burn similarly to a match head, at best.
The current standard composition for the black powders that are manufactured by pyrotechnicians was adopted as long ago as 1780. Proportions by weight are 75% potassium nitrate (known as saltpeter or saltpetre), 15% softwood charcoal, and 10% sulfur. These ratios have varied over the centuries and by country, and can be altered somewhat depending on the purpose of the powder. For instance, power grades of black powder, unsuitable for use in firearms but adequate for blasting rock in quarrying operations, is called blasting powder rather than gunpowder with standard proportions of 70% nitrate, 14% charcoal, and 16% sulfur; blasting powder may be made with the cheaper sodium nitrate substituted for potassium nitrate and proportions may be as low as 40% nitrate, 30% charcoal, and 30% sulfur. In 1857 Lamont DuPont solved the main problem when using cheaper sodium nitrate formulations when he patented DuPont "B" Blasting powder; after manufacturing grains from press-cake in the usual way, the powder was tumbled with graphite dust for 12 hours, forming a coating on each grain which in this case reduced its ability to pick up moisture
http://en.wikipedia.org/wiki/Gunpowder
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