(Chemical symbol: C4H10). A flammable gaseous paraffin hydrocarbon present in petroleum and natural gas, sometimes used in oxyfuel (flame) cutting. Butane is colorless, with a slightly unpleasant odor. Butane is available as a liquefied compressed gas in cylinders. Molecular weight, 58.123; specific gravity 2.110 at 20°C (68°F); liquid density, 4.81 Ib/gaI at
21°C (70°F); critical temperature, 152°C (305.6″F); critical pressure, 43.3 kPa (6.28 psia). See OXYFUEL GAS CUTTING and PROPANE.