Nitrosyl Fluoride, NOF

Nitrosyl fluoride is prepared by passing nitrosyl chloride over silver fluoride in a platinum tube heated to 200°-250° C., and condensing the gas in a platinum receiver immersed in liquid air. The liquid is purified by fractional distillation at a low temperature:

NOCl + AgF = AgCl + NOF.

At ordinary temperatures nitrosyl fluoride is a colourless gas, which liquefies at -56° C. and solidifies at -134° C. The vapour density (compared with air as unity) at 760 mm. and 23° C. is 1.683, which agrees with the formula NOF.

Chemically the gas is very active, many substances reacting with it in the cold. Thus sodium, silicon, boron, phosphorus, and antimony inflame, producing the corresponding fluoride and evolving nitric oxide. Lead, antimony, bismuth, and copper are only slowly attacked; while sulphur, carbon, and iodine are without action even on heating. Arsenic and antimony pentafluorides form additive compounds with nitrosyl fluoride.

The gas fumes in moist air, owing to the formation of hydrogen fluoride and nitrous acid, which decomposes, producing brown fumes.