Calcium carbide


Calcium carbide

Chembox new
Name = Calcium carbide
ImageFile = Carbid.jpg
ImageSize = 200px
ImageName = Calcium Carbide
IUPACName = Calcium Carbide
OtherNames =
Section1 = Chembox Identifiers
CASNo = 75-20-7

Section2 = Chembox Properties
Formula = CaC2
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 CaC2. 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 and coke at approximately 2000 °C. This method has not changed since its invention in 1888::CaO + 3C → CaC2 + 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 CaC2 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. [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)]

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 H. Moissan in 1888 and 1892. [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
] [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
]

Crystal structure

Pure calcium carbide is a colourless solid. The common crystalline form at room temperature is a distorted rock salt structure with the C22 units lying parallel.

Applications

Production of acetylene

The reaction of calcium carbide with water was discovered by Friedrich Wöhler in 1862.:CaC2 + 2H2O → C2H2 + Ca(OH)2

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. [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] Production of calcium carbide in China has been increasing. In 2005 output was 8.94 million tons with capacity to produce 17 million tons. [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] In the USA, Europe and Japan consumption is generally declining. [cite web | url = http://www.sriconsulting.com/CEH/Public/Reports/724.5000/ | author = Jamie Lacson, Stefan Schlag and Goro Toki | month = December | year = 2004 | title = Calcium Carbide | publisher = SRI Consulting] Production levels in the USA in 1990 were 236,000 tons pa.Greenwood&Earnshaw]

Production of calcium cyanamide

Calcium carbide reacts with nitrogen at high temperature to form calcium cyanamide::CaC2 + N2 → CaCN2 + CCalcium cyanamide is used as fertilizer. It is hydrolysed to cyanamide, H2NCN.

teelmaking

Calcium carbide is used:
* in the desulfurisation of iron (pig iron, cast iron and steel)
*as a fuel in steelmaking to extend the scrap ratio to liquid iron depending on economics.
*as a powerful deoxidizer at ladle treatment facilities.

Carbide lamps

Calcium carbide is used in carbide lamps, 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 cavers exploring caves and other underground areas, [ [http://www.teara.govt.nz/TheBush/BushAndMountainRecreation/Caving/4/en Caving equipment and culture] (from Te Ara Encyclopedia of New Zealand)] though they are increasingly being replaced in this use by 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). [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 ]

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 cannons.

Together with calcium phosphide, calcium carbide is used in floating, self-igniting naval 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


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Look at other dictionaries:

  • calcium carbide — n. a dark gray, crystalline compound, CaC2, used to produce acetylene and calcium cyanamide …   English World dictionary

  • calcium carbide — kalcio karbidas statusas T sritis chemija formulė CaC₂ atitikmenys: angl. calcium carbide; calcium diacarbide rus. кальция карбид ryšiai: sinonimas – kalcio dikarbidas …   Chemijos terminų aiškinamasis žodynas

  • calcium carbide — noun a grey salt of calcium (CaC) used in making acetylene • Hypernyms: ↑binary compound, ↑carbide …   Useful english dictionary

  • calcium carbide — a grayish black, lumpy, crystalline powder, CaC2, usually derived from coke or anthracite by reaction with limestone or quicklime: used chiefly for the generation of acetylene, which it yields upon decomposing in water. Also called carbide. [1885 …   Universalium

  • calcium carbide — noun Date: circa 1888 a usually dark gray crystalline compound CaC2 used especially for the generation of acetylene and for making calcium cyanamide …   New Collegiate Dictionary

  • calcium carbide — /kælsiəm ˈkabaɪd/ (say kalseeuhm kahbuyd) noun a crystalline compound of calcium and carbon, CaC2, which reacts with water to form acetylene …   Australian English dictionary

  • calcium carbide — noun A black, solid, of formula CaC, manufactured from lime and carbon at high temperatures; reacts with water to form acetylene …   Wiktionary

  • calcium carbide — n. compound used in the production of acetylene …   English contemporary dictionary

  • calcium carbide — cal′cium car′bide n. chem. a grayish black powder, CaC2, used chiefly to generate acetylene by decomposing it in water • Etymology: 1885–90 …   From formal English to slang

  • carbide, calcium carbide —    A compound (CaC2) of grayish color that reacts with water to produce acetylene gas and calcium hydroxide [Ca(OH)2] [13].    Commonly used by cavers and miners earlier in this century as a means of providing light in caves or mines. Some cavers …   Lexicon of Cave and Karst Terminology


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