Solute and solvent activities of CaCl2(aq) solutions from the adsorption isotherm treatment

The values of the two Brunauer-Emmett-Teller (BET) parameters calculated by Stokes and Robinson (1948) are reevaluated using recent experimental, data on the activity coefficients of CaCl2(aq) reported by Rard and Clegg (1997). At the 95% confidence level, no significant statistical differences are observed in the values df the BET parameters reported in this work and those reported by Stokes and Robinson (1948). The water activities a,, osmotic coefficients phi, and mean ionic activity coefficients, gamma(+/-) of CaCl2(aq) are then calculated from saturation to dilute solution. Since the standard state of the solute in the 1 BET model is the anhydrous liquid electrolyte rather than: the infinitely dilute solution, the technique of Ally and Braunstein (1996) is utilized to obtain the mean ionic activity coefficients of CaCl2(aq) over the, entire concentration range. The differences between the chemical potentials of the solute in the infinitely dilute solution standard state (hypothetical) and the anhydrous liquid electrolyte standard state (hypothetical) are shown to remain constant, as must be, since, the standard states are fixed at a given temperature. The ability of the model to predict a(w), phi, and gamma(+/-) with only two parameters is reported.