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Acetylene

Updated on August 22, 2009

Acetylene (C2H2) is a highly flammable gas that burns with intense heat and a bright white light. Acetylene is an organic compound of carbon and hydrogen. It freezes at -84.3° C. (-120° F.), is colorless, and is moderately poisonous when inhaled. When there are impurities in the gas, it has a somewhat offensive smell, but pure acetylene has an aromatic odor similar to that of ether.

Although acetylene was discovered in 1836 by the British chemist Edmund Davy, it was not until 1892 that it became of importance to industry. At that tune, Thomas L. Willson, a Canadian, discovered an inexpensive way of producing calcium carbide by heating coal and lime in an electric furnace. The calcium carbide was combined with water to produce acetylene. This process is still in use, although acetylene is now also produced by cracking (breaking up) large hydrocarbon molecules in crude petroleum.

Because acetylene yields a brilliant white light upon burning, it was formerly used in automobile headlights, bicycle lamps, and other lights. The gas was produced in these lights by allowing a small supply of water to drip slowly onto chunks of calcium carbide. Acetylene lamps have been largely replaced by electric lights, but acetylene is still used in some miner's lamps, on boats, in lighthouses and harbor buoys, and in other places where electricity is not available.

Acetylene explodes readily and violently and must be handled carefully. It can be shipped safely in metal cylinders by dissolving it in acetone under pressure. It is also shipped in steel containers packed with an absorbent filler that has no sizable spaces where acetylene fumes can collect and explode.

Acetylene combines readily with many substances and is widely used in the synthesis of industrial products. Acetic acid is produced in large quantities from acetylene. Neoprene synthetic rubber is produced from vinyl acetylene. Acetic acid reacts with acetylene to form vinyl acetates, which are used in paints, adhesives, safety-glass laminations, and synthetic sponges. Hydrogen chloride reacts with acetylene to produce vinyl chloride, which is made into vinyl plastics; these are used to make upholstery, floor tile, inflatable toys, and many other products. Combination of acetylene with hydrogen cyanide produces acrylonitrile, from which synthetic fibers such as Acrilan and Orion are made. Chlorination of acetylene yields chlorocarbons, which are used as solvents in dry cleaning and in industry. Acetylene is also widely used in oxyacetylene torches for cutting and welding metals.

An oxyacetylene torch is a device used for welding and cutting metals, such as steel. In the oxyacetylene torch, acetylene is burned in oxygen. Temperatures of more than 4000° C. may be reached in the flame of an oxyacetylene torch. The oxygen is supplied to the torch from a cylinder of compressed gas. Acetylene is supplied from a tank that is loosely packed with kapok or a similar material and filled with a solution of acetylene in acetone under pressure.

Cylinders of only compressed acetylene, without filler or packing, are not used because they are likely to explode with great violence.

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