FLUORINE

(F=18.9), an irritating gas and the most energetic halogen; combines with all elements except nitrogen and oxygen. It is liberated on pa ing an clectric current through hydrofluoric acid in platinum ve els. It decomposes cold water, and has bleaching and antiseptic properties. Hydrofluoric Acid (H.F.), obtained by decomposing fluor-spar with strong sulphuric acid, is a colorle volatile (the vapor being a deadly poison) liquid; M.P. 19° C. It is chemically very active, attacking gla (whence its use for gla etching), and its salts are called fluorides. FLUORBR-SPAR, DERBY SHIRE SPAR