Thermodynamic Study in the RbBO2-CsBO2 System by Mass-Spectrometric Knudsen Effusion Method.

Abstract

In the whole composition range of the solid solution in the RbBO2–CsBO2 system, activities and molar Gibbs energies, enthalpies, and entropies of mixing are determined from the ion-intensity ratios measured mass-spectrometrically in the temperature range below solidus line from 764 to 978 K. The activities of RbBO2 and CsBO2 show positive deviation from Raoult's law and decrease with increasing the temperature. The molar enthalpies of mixing are positive. From the small excess molar entropies of mixing, this solid solution is concluded to be almost regular. These results are compared with those for the mixed solutions of alkali halides.