Sulfur hexafluoride (SF₆) is colorless, odorless, tasteless and nontoxic noncombustible gas in normal conditions. Molecular weight: 146.06; density: 6.139g/l, which is about 5 times of air's. It is one of the materials we have known with best chemical stability, with same nonreactivity with that of nitrogen. It has excellent thermal stability, and will not decompose even when it is above 500℃ if pure.

   SF₆ has excellent electric insulativity and arc-extinguishing property. Under same conditions, its insulativity is 2.5 times of that of air and nitrogen at the least, and its arc-extinguishing property is 100 times of that of air. Its melting point is －50.8℃, so it can be used as special refrigerant within －45-0℃. For its high thermal resistance, it is also a kind of stable heat carrier.

   For the abovesaid and other excellent properties, SF₆ is widely used in electric power, electron, laser, medical treatment, meteorology, refrigeration, fire control, chemical and military industries, as well as space navigation, non-ferrous metallurgy, physical research, etc.