Silver fluoride, AgF

Evaporation in vacuum of a solution of silver oxide in hydrofluoric acid yields the Silver fluoride, AgF, in the form of an amorphous, yellow mass, of density 5.852 at 15.5° C. At red heat it melts to a black liquid, which on cooling solidifies to a crystalline mass. It is very soluble in water, its solubility at 15.5° C. being 181.8 grams per 100 grams of water. The solution has a neutral reaction. In its solubility the fluoride presents a marked contrast to the other silver halides. The anhydrous salt can absorb 844 times its volume of ammonia.

Two hydrates have been described. The monohydrate, AgF,H₂O, forms yellowish cubes,4 or large, deliquescent, tetragonal crystals, decomposed by heat with formation of a basic salt, Ag₂F(OH), and evolution of hydrogen fluoride. The dihydrate, AgF,2H₂O, crystallizes from concentrated solution in hard, transparent prisms.

From a solution of the fluoride in dilute hydrofluoric acid there crystallizes an acid salt, AgF,HF, in brown, deliquescent crystals. On cooling, a solution of the fluoride in pure hydrogen fluoride deposits white crystals of the formula AgF,3HF.

An aqueous solution containing 0.0002 per cent, of silver fluoride has been employed as a sterilizer to render water potable. The salt is sensitive to light.