The reaction of aluminum fluoride solution with cryolite

The title reaction was investigated kinetically and the products obtained were analyzed and examined by physicochemical methods. The reaction was found to result in the formation of NaAlF₄.H₂O and its solid solutions with aluminum fluoride with compositions down to Na_0.5AlF_3.5.1.3H₂O, except in the presence of chiolite seed crystals, which cause the reaction to give it as the final product.It was suggested that the solid solution are brought about by coprecipitation of approximately monohydrated hexagonal ° -AlF₃ direct from solution, both compounds being presumably isostructural each other.Differences in the infrared spectra of Na₂AlF₆, Na₅Al₃F₁₄ and NaAlF₄.H₂O were indicated.Homogenous mixtures of Na₃AlF₆ and NaAlF₄.H₂O are found to react exothermally at 350°C to give Na₅Al₃F₁₄, while NaAlF₄.H₂O alone decomposes into Na₅Al₃F₁₄ and AlF₃.