Propane, colorless, odorless gas of the alkane series of hydrocarbons, of formula C3H8. It occurs in crude oil, in natural gas, and as a by-product of petroleum refining. Propane does not react strongly at room temperature. It does react, however, with chlorine at room temperature if the mixture is exposed to light. At higher temperatures, propane burns in air, producing carbon dioxide and water as final products, and is valuable as a fuel.
About half the propane produced annually in the U.S. is used as a domestic and industrial fuel. When it is used as a fuel, propane is not separated from the related compounds, butane, ethane, and propylene. Butane, with boiling point-0.5° C (31.1° F), however, reduces somewhat the rate of evaporation of the liquid mixture. Propane forms a solid hydrate at low temperatures, and this causes great inconvenience when a blockage occurs in a natural-gas line. Propane is used also as so-called bottled gas, as a motor fuel, as a refrigerant, as a low-temperature solvent, and as a source of propylene and ethylene.
Propane melts at -189.9° C (-309.8° F) and boils at -42.1° C (-43.8° F).