Calcium carbide 242643 224110508 2008-07-07T10:36:48Z JAnDbot 1725149 robot Adding: [[cs:Karbid vápenatý]], [[sl:Kalcijev karbid]] Modifying: [[vi:Canxi cacbua]] {{refimprove|article|date=February 2008}} {{copyedit|article|date=February 2008}} {{Chembox new | Name = Calcium carbide | ImageFile = Cac2.jpg | ImageSize = 200px | ImageName = Calcium Carbide | IUPACName = Calcium Carbide | OtherNames = | Section1 = {{Chembox Identifiers | CASNo = 75-20-7 }} | Section2 = {{Chembox Properties | Formula = CaC<sub>2</sub> | MolarMass = 64.1 g/mol | Appearance = Gray-black crystals | Density = 2.22 g/cm³, solid (industrial grade) | MeltingPt = 2300 °C | BoilingPt = }} }} '''Calcium carbide''' is a [[chemical compound]] with the [[chemical formula]] of [[Calcium|Ca]][[Carbide|C<sub>2</sub>]]. The material is colorless, but most samples appear black through to grayish white lumps, depending on the grade. Its main use industrially is in the production of [[acetylene]]. ==Production== Calcium carbide is produced industrially in an [[electric arc furnace]] loaded with a mixture of [[Lime (mineral)|lime]] and [[coke (fuel)|coke]] at approximately 2000&nbsp;°C. This method has not changed since its invention in 1888: :CaO + 3C → CaC<sub>2</sub> + CO The high temperature required for this reaction is not practically achievable by traditional combustion, so the reaction is performed in an electric arc furnace with [[graphite]] electrodes. The carbide product produced generally contains around 80% calcium carbide by weight. The carbide is crushed to produce small lumps that can range a few mm up to 50 mm. The impurities are concentrated in the finer fractions. The CaC<sub>2</sub> content of the product is assayed by measuring the amount of acetylene produced on hydrolysis. As an example the British and German standards for the content of the coarser fractions are 295 L/kg and 300 L/kg respectively. Impurities present in the carbide include phosphide, which produces [[phosphine]] when hydrolysed.<ref name = Ullmans>[http://www.mrw.interscience.wiley.com/emrw/9783527306732/ueic/article/a04_533/current/pdf Calcium Carbide], Bernhard Langhammer, Ullmann's Encyclopedia of Industrial Chemistry, Wiley Interscience. (Subscription required)</ref> This reaction was an important part of the [[industrial revolution]] in chemistry. In the USA this occurred as a product of massive amounts of cheap [[hydro-electric power]] liberated from [[Niagara Falls]] before the turn of the 20th century. The method for the production in an [[electric arc furnace]] was discovered independently by T. L Willson and [[Henri Moissan|H. Moissan]] in 1888 and 1892.<ref>{{cite journal | title = The Manufacture of Calcium carbide | author = J. T. Morehead, G. de Chalmot | journal = Journal of The American Chemical Society | pages = 311–331 | doi = 10.1021/ja02090a001 | volume = 18 | issue = 4 | year = 1896}}</ref><ref>{{cite journal | title = Chimie Mindérale.- Description d'un nouveau four électrique | author = H. Moissan | journal = Comptes rendus hebdomadaires des séances de l'Académie des sciences | year = 1892 | volume = 115 | issue = | pages = 1031 | url = http://gallica.bnf.fr/ark:/12148/bpt6k3071t/f1031.chemindefer }}</ref> ==Crystal structure== Pure calcium carbide is a colourless solid. The common crystalline form at room temperature is a distorted rock salt structure with the C<sub>2</sub><sup>2<nowiki>&minus;</nowiki></sup> units lying parallel.<ref name = Greenwood/> ==Applications== ===Production of acetylene=== The reaction of calcium carbide with water was discovered by [[Friedrich Wohler]] in 1862. :CaC<sub>2</sub> + 2H<sub>2</sub>O → C<sub>2</sub>H<sub>2</sub> + Ca(OH)<sub>2</sub> This reaction is the basis of the industrial manufacture of [[acetylene]], and is the major industrial use of calcium carbide. In China, acetylene derived from calcium carbide remains a feedstock for the [[chemical industry]], in particular for the production of [[polyvinyl chloride]], PVC. Locally produced acetylene is more economic than using imported oil.<ref>{{cite web | author = Ya Dun | title = Troubles in the PVC industry | publisher = Hong Kong Trade Development Council | url = http://www.tdctrade.com/report/indprof/indprof_060106.htm | date = 2006-01-23}}</ref> Production of calcium carbide in China has been increasing. In 2005 output was 8.94 million tons with capacity to produce 17 million tons.<ref>{{cite news | title = Govt takes measures to curb development of calcium carbide sector | publisher = BusyTrade.com | url = http://www.busytrade.com/news/newsinfo.php?id=2425 | date = 2007-05-16}}</ref> In the USA, Europe and Japan consumption is generally declining.<ref>{{cite web | url = http://www.sriconsulting.com/CEH/Public/Reports/724.5000/ | author = Jamie Lacson, Stefan Schlag and Goro Toki | date = December 2004 | title = Calcium Carbide | publisher = SRI Consulting}}</ref> Production levels in the USA in 1990 were 236,000 tons pa.<ref name = Greenwood>{{Greenwood&Earnshaw}}</ref> ===Production of calcium cyanamide=== Calcium carbide reacts with nitrogen at high temperature to form calcium cyanamide: :CaC<sub>2</sub> + N<sub>2</sub> → CaCN<sub>2</sub> + C Calcium cyanamide is used as fertilizer. It is hydrolysed to [[cyanamide]], H<sub>2</sub>NCN.<ref name = Greenwood/> ===Steelmaking=== Calcium carbide is used: * in the [[desulfurisation]] of iron (pig iron, cast iron and steel)<ref name = Ullmans/> *as a fuel in steelmaking to extend the scrap ratio to liquid iron depending on economics. *as a powerful [[deoxidizer]] at [[ladle (metallurgy)|ladle]] treatment facilities. ===Carbide lamps=== {{Main|Carbide lamp}} Calcium carbide was used in [[carbide lamp]]s, in which water drips on carbide and the formed acetylene is ignited. These lamps were unusable in coal mines where the presence of the flammable gas methane made them a serious hazard. The presence of flammable gases in coal mines led to the miner [[safety lamp]]. However carbide lamps were used extensively in slate, copper and tin mines, but most have now been replaced by electric lamps. Carbide lamps are still used by some [[caver]]s [[caving|exploring caves]] and other underground areas,<ref>[http://www.teara.govt.nz/TheBush/BushAndMountainRecreation/Caving/4/en Caving equipment and culture] (from [[Te Ara Encyclopedia of New Zealand]])</ref> though they are increasingly being replaced in this use by [[Light-emitting diode|LED]] lights. They were also used extensively as head lights in early [[automobiles]], although in this application they are also obsolete, having been replaced entirely by electric lamps. ===Other uses=== In the ripening of fruit, it is used as source of acetylene gas, which is a ripening agent (similar to ethylene).<ref>{{cite journal | author = F. B. Abeles and H. E. Gahagan, III | title = Abscission: The Role of Ethylene, Ethylene Analogues, Carbon Dioxide, and Oxygen | year = 1968 | journal = [[Plant Physiol.]] | volume = 43 | issue = 8 | pages = 1255–1258 | url = http://www.plantphysiol.org/cgi/content/abstract/43/8/1255 | pmid = 16656908 }}</ref> It is still used in the [[Netherlands]] and [[Belgium]] for a traditional custom called ''Carbidschieten'' (Shooting Carbide). To create an explosion, carbide and water are put in a milk churn with a lid. Ignition is usually done with a torch. Some villages in the Netherlands fire multiple milk churns in a row as a New Year's Eve tradition. The old tradition comes from the old [[pagan]] religion to chase off spirits. It is used in toy cannons (see [[Big-Bang Cannon]]), as well as in [[bamboo cannon]]s. Together with [[calcium phosphide]], calcium carbide is used in floating, self-igniting naval [[flare (pyrotechnic)|signal flares]] (see [[Holmes' Marine Life Protection Association]]). Calcium carbide is also used in small carbide lamps called ''carbide candles'', which are used for blackening rifle sights to reduce glare. These "candles" are used due to the sooty flame produced by acetylene. ==External links== * [http://www.epa.gov/ttn/chief/ap42/ch11/final/c11s04.pdf Calcium Carbide Manufacturing] ==References== <references /> [[Category:Calcium compounds]] [[Category:Carbides]] [[Category:Acetylides]] [[Category:Deoxidizers]] [[cs:Karbid vápenatý]] [[de:Calciumcarbid]] [[es:Carburo de calcio]] [[id:Karbit]] [[it:Carburo di calcio]] [[hu:Kalcium-karbid]] [[nl:Calciumcarbide]] [[ja:炭化カルシウム]] [[pl:Karbid]] [[pt:Carbeto de cálcio]] [[ru:Карбид кальция]] [[sk:Karbid vápenatý]] [[sl:Kalcijev karbid]] [[vi:Canxi cacbua]] [[zh:电石]]