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

Fusibility and structure of the NaF-rich melts in the NaF-NaAlSi₃O₈ and NaF-KAlSi₃O₈ systems

K. Grjotheim, V. Daněk, K. Matiašovský, and J. Stubergh

Department of Chemistry, University of Oslo, N-0315 Oslo 3, Norway

Abstract: The liquidus curves of NaF in the NaF—NaAlSi₃O₈  and NaF— KAlSi₃O₈ systems were determined using the thermal analysis and the visual thermal analysis methods. Different courses of the liquidus curves were found de­pending on the nature of the system under investigation. Various ther­modynamic approaches were applied for the NaF activity calculation. The best fit of the experimental and calculated values of the temperature of primary crystallization of NaF was obtained if neither a chemical reaction between the fluoride anions and the feldspar polyanions nor a full disin­tegration of the feldspar anions were considered. In the NaF— NaAlSi₃O₈ system, the interaction energy of 21 kJmol-1 is probably necessary for the exchange reaction of the accompanying calcium oxide (as impurity) with sodium fluoride. In the NaF—KAlSi₃O₈  reciprocal system, the standard Gibbs energy of the exchange reaction was included in the calculation.

Full paper in Portable Document Format: 445a685.pdf

Chemical Papers 44 (5) 685–691 (1990)