SHREE SITA RAM
CALCIUM CARBIDE CaC2
SSRC®

- PRODUCTION OF ACETYLENE GAS:

The reaction of calcium carbide with water, producing acetylene and calcium hydroxide, was discovered by Friedrich Wöhler in 1862.

CaC2(s) + 2H2O(aq) → C2H2(g) + Ca(OH)2(aq)

This reaction was the basis of the industrial manufacture of acetylene, and is the major industrial use of calcium carbide. Today acetylene is mainly manufactured by the partial combustion of methane or appears as a side product in the ethylene stream from cracking of hydrocarbons. Approximately 400,000 tonnes are produced this way annually (see Acetylene Preparation). In China, acetylene derived from calcium carbide remains a raw material for the chemical industry, in particular for the production of polyvinyl chloride. Locally produced acetylene is more economical than using imported oil. Production of calcium carbide in China has been increasing. In 2005 output was 8.94 million tons, with the capacity to produce 17 million tons. In the United States, Europe, and Japan, consumption of calcium carbide is generally declining. Production levels in the US during the 1990s were 236,000 tons per year.

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- PRODUCTION OF CALCIUM CYANAMIDE:

Calcium carbide reacts with nitrogen at high temperature to form calcium cyanamide:

CaC2 + N2 → CaCN2 + C

Commonly known as nitrolime, calcium cyanamide is used as fertilizer. It is hydrolysed to cyanamide, H2NCN.

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- STEEL MAKING:

Calcium carbide is used:

• in the desulfurization 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.

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- CARBIDE LUMPS:

Calcium carbide is used in carbide lamps. Water dripping on carbide produces acetylene gas, which burns and produces light. While these lamps gave steadier and brighter light than candles, they were dangerous in coal mines, where flammable methane gas made them a serious hazard. The presence of flammable gases in coal mines led to miner safety lamps such as the Davy lamp, in which a wire gauze reduces the risk of methane ignition. Carbide lamps were still used extensively in slate, copper, and tin mines where methane is not a serious hazard. Most miners' lamps have now been replaced by electric lamps.

Carbide lamps are still used for mining in some less wealthy countries, for example in the silver mines near Potosí, Bolivia. Carbide lamps are also still used by some cavers exploring caves and other underground areas, although they are increasingly being replaced in this use by LED lights.

Carbide lamps were also used extensively as headlights in early automobiles, motorcycles and bicycles, but have been replaced entirely by electric lamps.

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- OTHER USES:

Calcium carbide is sometimes used as source of acetylene gas, which is a ripening agent similar to ethylene. However, this is illegal in some countries as, in the production of acetylene from calcium carbide, contamination often leads to trace production of phosphine and arsine. These impurities can be removed by passing the acetylene gas through acidified copper sulfate solution, but, in developing countries, this precaution is often neglected.

Calcium carbide is used in toy cannons such as the Big-Bang Cannon, as well as in bamboo cannons. In the Netherlands calcium carbide is used around new-year to shoot with milk churns.

Calcium carbide, together with calcium phosphide, is used in floating, self-igniting naval signal flares, such as those produced by the Holmes' Marine Life Protection Association.

Calcium carbide is used to determine the moisture content of soil. When soil and calcium carbide are mixed in a closed pressure cylinder, the water content in soil reacts with calcium carbide to release acetylene whose pressure can be measured to determine the moisture content.

Calcium carbide is sold commercially as a mole repellent. When it comes into contact with water, the produced gas drives away the moles.