(n.) A non-metallic, gaseous element, strongly acid or negative, or associated with chlorine, bromine, and iodine, in the halogen group of which it is the first member. It always occurs combined, is very active chemically, and possesses such an avidity for most elements, and silicon especially, that it can neither be prepared nor kept in glass vessels. If set free it immediately attacks the containing material, so that it was not isolated until 1886. It is a pungent, corrosive, colorless gas. Symbol F. Atomic weight 19.

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