Collier's New Encyclopedia (1921)/Acetylene

ACETYLENE, a hydrocarbon having the formula C $2$ H $2$, also called ethine. The carbon atoms are united to each other by three bonds. It is produced by passing an electric current between carbon poles in an atmosphere of hydrogen, and also by the incomplete combustion of hydrocarbons. It is a colorless gas, specific gravity, 0.92, has a peculiar odor, and burns with a bright flame; it forms a red precipitate with ammoniacal cuprous chloride, which, by the action of nascent hydrogen, is converted into ethylene, C $2$ H $4$.

Source: Collier's New Encyclopedia 1. (1921) New York: P.F. Collier & Son Company. 19 (text) and following 60 (illustration).