Gunpowder

Gunpowder, also known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur (S), charcoal (C), and potassium nitrate (saltpeter, KNO3). The sulfur and charcoal act as fuels while the saltpeter is an oxidizer. Because of its incendiary properties and the amount of heat and gas volume that it generates, gunpowder has been widely used as a propellant in firearms, artillery, rockets, and fireworks, and as a blasting powder in quarrying, mining, and road building. Gunpowder was invented in 9th-century China and spread throughout most parts of Eurasia by the end of the 13th century. Originally developed by the Taoists for medicinal purposes, gunpowder was first used for warfare about 1000 AD. 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 gunpowder packed behind a projectile generates enough pressure to force the shot from the muzzle at high speed, but usually not enough force to rupture the gun barrel. Gunpowder thus makes a good propellant, but is less suitable for shattering rock or fortifications with its low-yield explosive power. However, by transferring enough energy (from the burning gunpowder to the mass of the cannonball, and then from the cannonball to the opposing fortifications by way of the impacting ammunition) eventually a bombardier may wear down an opponent's fortified defenses. Gunpowder was widely used to fill fused artillery shells (and used in mining and civil engineering projects) until the second half of the 19th century, when the first high explosives were put into use. Gunpowder is no longer used in modern weapons, nor is it used for industrial purposes, due to its relatively inefficient cost compared to newer alternatives such as dynamite and ammonium nitrate/fuel oil. Today gunpowder firearms are limited primarily to hunting, target shooting, and bulletless historical reenactments. Based on a 9th-century Taoist text, the invention of gunpowder by Chinese alchemists was likely an accidental byproduct from experiments seeking to create the elixir of life. This experimental medicine origin of gunpowder is reflected in its Chinese name huoyao, which means 'fire medicine'. The first military applications of gunpowder were developed around 1000 AD. The earliest chemical formula for gunpowder appeared in the 11th century Song dynasty text, Wujing Zongyao, however gunpowder had already been used for fire arrows since at least the 10th century. In the following centuries various gunpowder weapons such as bombs, fire lances, and the gun appeared in China. Saltpeter was known to the Chinese by the mid-1st century AD and was primarily produced in the provinces of Sichuan, Shanxi, and Shandong. There is strong evidence of the use of saltpeter and sulfur in various medicinal combinations. A Chinese alchemical text dated 492 noted saltpeter burnt with a purple flame, providing a practical and reliable means of distinguishing it from other inorganic salts, thus enabling alchemists to evaluate and compare purification techniques; the earliest Latin accounts of saltpeter purification are dated after 1200. The first reference to the incendiary properties of such mixtures is the passage of the Zhenyuan miaodao yaolüe, a Taoist text tentatively dated to the mid-9th century: 'Some have heated together sulfur, realgar and saltpeter with honey; smoke and flames result, so that their hands and faces have been burnt, and even the whole house where they were working burned down.' The Chinese word for 'gunpowder' is Chinese: 火药/火藥; pinyin: huŏ yào /xuo yɑʊ/, which literally means 'Fire Medicine'; however this name only came into use some centuries after the mixture's discovery. In the following centuries a variety of gunpowder weapons such as rockets, bombs, and land mines appeared before the first metal barrel firearms were invented. Explosive weapons such as bombs have been discovered in a shipwreck off the shore of Japan dated from 1281, during the Mongol invasions of Japan.