Solubility of Al₂O₃ in Some Chloride−Fluoride Melts

Alumina solubility in chloride−fluoride melts of KCl−NaCl−NaF mixtures with ratios of 0.425:0.425:0.15 (I), 0.38:0.38:0.24 (II), and 0.35:0.35:0.30 (III) (molar fractions) was investigated in the 973−1123 K temperature range using the isothermal saturation method. Al₂O₃ solubility in the ionic melts studied was shown to be on the order of 0.06 g kg^-1 for system I, 0.12 g kg^-1 for system II, and 0.14 g kg^-1 for system III at 1073 K. All the “Al₂O₃ + melt” systems were found to demonstrate negative deviations from the ideal solutions. The solubility of Al₂O₃ in all the melts increases with the temperature increase; however, the dependences of −log N_Al2O3 versus T^-1 were characterized by the slopes (2.6 ± 0.4) × 10³ K (I and II) and (2.4 ± 0.6) × 10³ K (III), which were considerably less than the slope predicted by the Shreder−Le Chatelier equation (∼5.8 × 10³).