Acetylene

Acetylene, C2H2 (= CH.CH), or Ethine, a gaseous substance of disagreeable odour, which is produced by the incomplete combustion of hydrocarbons; the well-known smell of a Bunsen burner which has been turned low and "lit back" is due to formation of acetylene. It was discovered by Berthelot in 1859, by discharging an electric current between carbon points, in an atmosphere of hydrogen, and forms the starting-point in his celebrated synthesis of alcohol. Acetylene may be liquefied at ordinary temperatures by a pressure of about 80 atmospheres.