is of any of a group of five chemically related
nonmetallic elements: chlorine, bromine, fluorine, iodine, and astatine.
Chlorine compounds are used as EP addiitives
in certain lubricating oils, and as constituents of certain
petrochemicals (e.g., vinyl chloride,
chlorinated waxes). Chlorine and fluorine
compounds are also used in some synthetic lubricants.