ISOPIESTIC STUDIES OF AQUEOUS-SOLUTIONS AT ELEVATED-TEMPERATURES .11. ((1-Y)CSCL+YBACL2)(AQ)

Isopiestic results were obtained for the common-ion mixture {(1-yCsCl+yBaCl2}(aq) over the temperature range 383 K to 524 K. NaCl(aq) served as the reference electrolyte for the calculation of excess thermodynamic properties. The ion-interaction model, as applied to mixed electrolytes, gave an excellent description of the experimental results. In contrast to mixtures of the alkali-metal cations, the present mixture of unlike-charge types required both binary and ternary mixing parameters. Mixing contributions were very important, amounting to as much as 50 per cent of the trace activity coefficient of BaCl2. The excess enthalpy indicates a change in the nature of the solute-solvent interaction at about 475 K. Derived activity coefficients depend significantly on using or omitting the theoretical mixing terms and also on the value of the parameter α. © 1992 Academic Press Limited All rights reserved.