Gases (petroleum), C3-4; Petroleum gas; [A complex combination of hydrocarbons produced by distillation of products from the cracking of crude oil. It consists of hydrocarbons having carbon numbers in the range of C3 through C4, predominantly of propane and propylene, and boiling in the range of approximately – 51 °C to – 1 °C (– 60 °F to 30 °F.)]