ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Dissociation of the anions AlF₆^3- in the system Na₃AlF₆ —Na₂SO₄

I. Koštenská and M. Malinovský

Department of Inorganic Technology, Slovak Technical University, 880 37 Bratislava

Abstract:  The course of the liquidus of Na₂SO₄ in the system Na₃AIF₆ —Na₂SO₄ was determined. The eutectic point was found to be at 9.0 mole % Na₃AlF₆ and 91.0 mole % Na₂SO₄, t_E = 794.5°C. The solubility of Na₃AIF₆ in solid Na₂SO₄ is negligible. The course of the liquidus curve of Na₂SO₄ in the composition interval of 91.0—96.0 mole % Na₂SO₄ is consistent with the assumption that the anions AlF₆^3- undergo thermal dissociation according to the scheme AlF₆^3- ⇌ AIF₄^- + 2F^-. At a very low content of Na₃AIF₆ in Na₂SO₄ a total destruction of the anions AlF₄ takes place under the formation of 7 new elementary particles from each molecule of Na₃AIF₆ in molten Na₂SO₄ . In the eutectic point of the system Na₃AIF₆—Na₂SO₄ the degree of thermal dissociation of AlF₆^3- anions according to the given scheme equals 0.67. The calculated dissociation degree of pure cryolite is 0.21. The conclusions of some other papers concerning the given problems are discussed.

Full paper in Portable Document Format: 326a821.pdf

Chemical Papers 32 (6) 821–829 (1978)