OLEF'IANT, a. [L. oleo, olfacio.] Olefiant gas is a compound of one prime of carbon and one of hydrogen, called by Ure carbureted hydrogen, to distinguish it from the gas resulting from one prime of carbon and two of hydrogen, which he calls subcarbureted hydrogen.

Olefiant gas, is so called from its property of forming with chlorin a compound resembling oil.