(n.) A substance regarded as an element, contained in the atmosphere and remarkable for its chemical inertness.

Dry Ice Freon acetylene argon asphyxiating gas butane carbon dioxide carbon monoxide castor-bean meal chlorine coal gas commercial fertilizer compost coolant dressing dung enrichener ethane ether ethyl chloride ethylene fertilizer fluorine formaldehyde freezing mixture guano helium hydrogen ice ice cubes illuminating gas krypton lewisite liquid air liquid helium liquid oxygen manure marsh gas methane muck mustard gas natural gas neon night soil nitrate nitrogen organic fertilizer oxygen ozone phosphate poison gas propane radon refrigerant sewer gas superphosphate xenon