Cobalt fluoride, CoF 2.2H 2 0, is formed when cobalt carbonate is evaporated with an excess of aqueous hydrofluoric acid, separating in rose-red crystalline crusts.
Electrolysis of a solution in hydrofluoric acid gives cobaltic fluoride, CoF3.
The dark product obtained is washed with water, hydrochloric acid and hydrofluoric acid, and finally calcined again with the oxide or with borax, being protected from air during the operation by a layer of charcoal.
It may be condensed and yields a solid which melts at - 55° C. Sulphuretted hydrogen decomposes it with formation of hydrofluoric acid and liberation of sulphur.
It is decomposed by water into hydrofluoric and sulphurous acids.