acetylene [key], HC≡CH, a colorless gas. It melts at −80.8℃ and boils at −84.0℃. Offensive odors often noted in commercial acetylene are due to impurities. Acetylene forms explosive mixtures with oxygen or air. It is soluble in acetone, ethanol, and water. When dissolved in acetone it is nonexplosive and so is stored dissolved in acetone under pressure in steel cylinders for commercial use. Since it is explosive in the liquid state, it is not generally stored in this form. Acetylene is easily prepared commercially by the reaction of calcium carbide with water, but is prepared commercially by the pyrolysis of hydrocarbons. It is used for cutting and welding metals (see oxyacetylene torch) and is sometimes used as an illuminant gas. When subjected to high temperatures, it undergoes polymerization; benzene may also be formed. It is used in the production of many organic compounds, e.g., neoprene rubber, plastics, and resins. Acetylene is the simplest alkyne.
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