Gunpowder is a pyrotechnic composition, an explosive mixture of sulfur, charcoal and potassium nitrate (also known as saltpetre/saltpeter) that burns rapidly, producing volumes of hot solids and gases which can be used as a propellant in firearms and fireworks.
Gunpowder is classified as a low explosive because of its slow decomposition rate and consequently low brisance. Low explosives produce a subsonic deflagration wave rather than the supersonic detonation wave produced by brisants, or high explosives. The gases produced by burning gunpowder generate enough pressure to propel a bullet, but not enough to destroy the barrel of a firearm. This makes gunpowder less suitable for shattering rock or fortifications, where high explosives such as TNT are preferred.
Contents [hide]
1 Gunpowder (black powder)
1.1 Advantages
1.2 Disadvantages
1.3 Transportation
2 Sulfur-free gunpowder
3 History
3.1 China
3.2 Islamic world
3.3 Europe
3.4 Britain
3.5 India
3.6 United States
4 Manufacturing technology
5 Other uses
6 See also
7 Notes
8 References
9 External links
[edit] Gunpowder (black powder)
The term "black powder" was coined in the late 19th century to distinguish prior gunpowder formulations from the new smokeless powders and semi-smokeless powders. (Semi-smokeless powders featured bulk volume properties that approximated black powder in terms of chamber pressure when used in firearms, but had significantly reduced amounts of smoke and combustion products; they ranged in color from brownish tan to yellow to white. Most of the bulk semi-smokeless powders ceased to be manufactured in the 1920's.)[1][2][3]
Black powder is a granular mixture of
a nitrate—typically potassium nitrate (KNO3)—which supplies oxygen for the reaction;
charcoal, which provides fuel for the reaction in the form of carbon (C);
sulfur (S), which, while also a fuel, lowers the temperature of ignition and increases the speed 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.[4] 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.
The current standard composition for black powder manufactured by pyrotechnicians was adopted as long ago as 1780. It is 75% potassium nitrate, 15% softwood charcoal, and 10% sulfur.[5] These ratios have varied over the centuries, and by country, but can be altered somewhat depending on the purpose of the powder.
The burn rate of black powder can be changed by corning. Corning first compresses the fine black powder meal into blocks with a fixed density (1.7 g/cm³). The blocks are then broken up into granules. These granules are then sorted by size to give the various grades of black powder. In the USA, standard grades of black powder run from the coarse Fg grade used in large bore rifles and small cannon though FFg (medium and smallbore rifles), FFFg (pistols), and FFFFg (smallbore, short pistols and priming flintlocks). In the United Kingdom, the gunpowder grains are categorised by mesh size: the BSS sieve mesh size, being the smallest mesh size on which no grains were retained. Recognised grain sizes are Gunpowder 'G 7', 'G 20', 'G 40', and 'G 90'.
A simple, commonly cited, chemical equation for the combustion of black powder is
2 KNO3 + S + 3 C → K2S + N2 + 3 CO2.
A more accurate, but still simplified, equation is[6]
10 KNO3 + 3 S + 8 C → 2 K2CO3 + 3 K2SO4 + 6 CO2 + 5 N2.
The products of burning do not follow any simple equation. One study's results showed that it produced (in order of descending quantities): 55.91% solid products: potassium carbonate, potassium sulfate, potassium sulfide, sulfur, potassium nitrate, potassium thiocyanate, carbon, ammonium carbonate. 42.98% gaseous products: carbon dioxide, nitrogen, carbon monoxide, hydrogen sulfide, hydrogen, methane, 1.11% water.
Black powder formulations where the nitrate used is sodium nitrate tend to be hygroscopic, unlike black powders where the nitrate used is saltpetre. Because of this, black powder which uses saltpetre can be stored unsealed and remain viable for centuries provided no liquid water is ever introduced; muzzleloaders have been known to fire after hanging on a wall for decades in a loaded state, provided they remained dry. By contrast, powder that uses sodium nitrate, which is typically intended for blasting, must be sealed from moisture in the air to remain stable for long times.
[edit] Advantages
Smokeless powder requires precise loading of the charge to prevent damage due to overloading. With black powder, though such damage is still possible, loading can generally be carried out using volumetric measures rather than precise weight.
Generally, high explosives are preferred for shattering rock; however, because of its low brisance, black powder causes fewer fractures and results in more usable stone compared to other explosives, making black powder useful for blasting monumental stone such as granite and marble.
Black powder is well suited for blank rounds, signal flares, burst charges, and rescue-line launches.
Gunpowder can be used to make fireworks by mixing with chemical compounds that produce the desired color.
[edit] Disadvantages
Black powder has relatively low energy density compared to modern smokeless powders and produces a thick smoke that can impair aiming and reveal a shooter's position.
Combustion converts less than half the mass of black powder to gas; the rest ends up as a thick layer of soot inside the barrel. In addition to being a nuisance, the residue from burnt black powder is hygroscopic and an anhydrous caustic substance. When moisture from the air is absorbed, the potassium oxide or sodium oxide turns into hydroxide, which will corrode wrought iron or steel gun barrels. Black powder arms must be well cleaned both inside and out to remove the residue.
[edit] Transportation
The UN Model Regulations on the Transportation of Dangerous Goods and national transportation authorities, such as United States Department of Transportation, have classified Gunpowder (black powder) as a Group A: Primary explosive substance for shipment because it ignites so easily. Complete manufactured devices containing black powder are usually classified as Group D: Secondary detonating substance, or black powder, or article containing secondary detonating substance, such as "Firework", "Class D Model Rocket Engine", etc, for shipment because they are harder to ignite than loose powder. As explosives, they all fall into the category of Class 1.
[edit] Sulfur-free gunpowder
The development of smokeless powders, such as Cordite, in the late 19th century created the need for a spark-sensitive priming charge, such as gunpowder. However, the sulfur content of traditional gunpowders caused corrosion problems with Cordite Mk I and this led to the introduction of a range of sulfur-free gunpowders, of varying grain sizes.[7] They typically contain 70.5 parts of saltpetre and 29.5 parts of charcoal.[7] Like black powder, they were produced in different grain sizes. In United Kingdom, the finest grain was known as sulfur-free mealed powder (SMP). Coarser grains were numbered as sulfur-free gunpowder (SFG n): 'SFG 12', 'SFG 20', 'SFG 40' and 'SFG 90', for example, where the number was a BSS sieve mesh size, being the smallest mesh size on which no grains were retained.
[edit] History
Main article: History of gunpowder
[edit] China
A Mongol bomb thrown against a charging Japanese samurai during the Mongol invasions of Japan, 1281.Most sources credit the discovery of gunpowder to Chinese alchemists in the 9th century searching for an elixir of immortality.[8] The discovery of gunpowder was probably the product of centuries of alchemical experimentation.[9] Saltpetre was known to the Chinese by the mid-1st century AD and there is strong evidence of the use of saltpetre and sulfur in various largely medicinal combinations.[10] A Chinese alchemical text from 492 noted that saltpeter gave off a purple flame when ignited, providing for the first time a practical and reliable means of distinguishing it from other inorganic salts, making it possible to evaluate and compare purification techniques.[9]
The first reference to gunpowder is probably a passage in the Zhenyuan miaodao yaolüe, a Taoist text tentatively dated to the mid-800s:[9]
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.[11]
Ming Dynasty (1368-1644 AD) matchlock firearmsContrary to popular belief, the Chinese did not use gunpowder only for fireworks. In fact, the earliest surviving recipes for gunpowder can be found in the Chinese military treatise Wujing zongyao[9] of 1044 AD, which contains three: two for use in incendiary bombs to be thrown by siege engines and one intended as fuel for poison smoke bombs.[12] The formulas in the Wujing zongyao range from 27 to 50 percent nitrate.[13] Experimenting with different levels of saltpetre content eventually produced bombs, grenades, and land mines, in addition to giving fire arrows a new lease on life.[9] By the end of the 12th century, there were cast iron grenades filled with gunpowder formulations capable of bursting through their metal containers.[14] The 14th century Huolongjing contains gunpowder recipes with nitrate levels ranging from 12 to 91 percent, six of which approach the theoretical composition for maximal explosive force.[1