Abstract: Ammonium fluoride is converted into a bifluoride by reaction with KF to form KF.HF, converting the latter to NaF.HF and heating said sodium bifluoride to form a solid product comprising NaF.

Abstract: Potassium fluoride and silica are reacted with an aqueous solution of hydrofluorosilicic acid. The resulting potassium fluorosilicate is recovered. The potassium fluorosilicate may be further reacted with ammonia in water to form an aqueous mixture of ammonium fluoride and potassium fluoride. The ammonium fluoride is then heated in aqueous solution in the presence of excess potassium fluoride to release ammonia and to form potassium bifluoride. The potassium bifluoride is recovered from solution substantially free from ammonia and heated to release hydrogen fluoride. Alternatively, the recovered potassium bifluoride may be reacted with sodium fluoride to produce sodium bifluoride. The sodium bifluoride is then heated to release hydrogen fluoride.

Abstract: Hydrogen fluoride is produced from hydrofluosilicic acid. The hydrofluosilicic acid is reacted with ammonia. An aqueous solution of ammonium fluoride thus produced is fed with partly recycled alkali metal fluoride to a continuously operated reactor where a bifluoride of the alkali metal is formed in aqueous solution. Reaction mixture is continuously withdrawn and solid alkali metal bifluoride crystallized therefrom. The mother liquor is recycled to the reactor. The solid alkali metal bifluoride is decomposed by heat to produce hydrogen fluoride and solid alkali metal fluoride. The alkali metal fluoride is recycled to the reactor.

Abstract: Hydrogen fluoride is recovered from hydrofluosilicic acid by-product of phosphoric acid manufacture. The hydrofluosilicic acid effluent is reacted with ammonia to form ammonium fluoride which is converted to a bifluoride by reaction with an excess of soluble metal fluoride. The bifluoride is readily recoverable and decomposable to yield hydrogen fluoride.