Electromotive-force measurements of molten oxide mixtures. Part 8.—Thermodynamic properties of Na2O–B2O3 melts

Abstract

E.m.f. measurements of Na₂O–B₂O₃ melts in the composition range B₂O₃ to Na₂O·2B₂O₃ have been performed in which the liquid junction used in previous studies was improved by using β-alumina. The partial and total molar free energies, enthalpies and entropies of solution have been evaluated. In accordance with Krogh-Moe's treatment, the fractions of boroxol, tetraborate and the diborate group were estimated on the assumption of an ideal associated solution. The activity of Na₂O seems to change along a stepwise neutralization curve, where B₂O₃ or equally boroxol is considered to be a polybasic acid.