any of a group of compounds of sulfur with fluorine that includes SF6, SF4, S2 F10, SF2, and S2 F2. Only the first three compounds have practical importance.
Sulfur hexafluoride (SF6) is a colorless, odorless gas with a density 5.107 times that of air (20°C), a melting point (mp) of - 50.5°C and a boiling point (bp) of - 63.8°C. The compound is only slightly soluble in water but dissolves somewhat more readily in alcohol. Upon heating in oxygen or hydrogen, sulfur hexafluoride does not undergo chemical change but is decomposed by hydrogen sulfide into HF and S. Sulfur hexafluoride is formed by burning S in F2 and is used as a gaseous insulator for high-voltage equipment (elegas).
Sulfur pentafluoride (disulfur decafluoride, S2 F10) is a colorless liquid with a density of 2.08 g/cm3 (0°C), an mp of - 92°C, and a boiling point (bp) of 29°C. Its chemical properties are similar to those of SF6, but it is less inert and very poisonous. With CCl2, sulfur pentafluoride yields the fluorochloride SF5 Cl. Sulfur pentafluoride is formed in the reaction of elements as an admixture of SF6.
Sulfur tetrafluoride (SF4) is a colorless, highly poisonous gas with a sharp odor, an mp of - 124°C, and a bp of -40°C. It is produced by the reaction of SCl2 with NaF or of CoF3 with S. Sulfur tetrafluoride reacts with aldehydes, ketones, and other carbonyl compounds to form the coresponding organic fluorine compounds.