Sulphuryl Fluoride, SO₂F₂

Sulphuryl Fluoride, SO₂F₂ was obtained by Moissan and Lebeau by heating a gaseous mixture of sulphur dioxide and fluorine electrically with a platinum wire. By this method the resulting sulphuryl fluoride contains thionyl fluoride, sulphur dioxide and oxygen, the sulphur impurities being removable by water and the oxygen by cooling to -80° C., which leaves it uncondensed.

The combustion of fluorine in moist hydrogen sulphide or the interaction of fluorine and dry hydrogen sulphide in a glass vessel (the last- named supplying the necessary oxygen) also gives rise to a mixture of sulphuryl fluoride with thionyl fluoride, sulphur hexafluoride and silicon fluoride.

Sulphuryl fluoride is a colourless, odourless gas, which liquefies at -52° C. and solidifies in liquid air, melting then at -120° C. It is remarkably stable, and dissolves unchanged in water to the extent of approximately 1 volume in 10 at the ordinary temperature; alcohel absorbs about three volumes of the gas at the ordinary temperature.

Chemically the gas is surprisingly inactive. It is unaffected by water at 150° C., but an aqueous solution of potassium hydroxide causes decomposition into potassium fluoride and sulphate:

SO₂F₂ + 4KOH = K₂SO₄ + 2KF + 2H₂O.

It attacks glass at a red heat, giving silicon tetrafluoride and sulphur trioxide. Carbon and boron are without action on the gas at a red heat, but sodium at a temperature considerably above the melting-point causes gradual decomposition with absorption. Hydrogen sulphide, aided by heat, attacks both thionyl and sulphuryl fluorides, inducing decomposition.