ION-INTERACTION APPROACH FOR VOLUMETRIC CALCULATIONS FOR SOLUTIONS OF SINGLE ELECTROLYTES AT 25-DEGREES-C

The ion interaction approach of Pitzer permits the prediction of thermodynamic characteristics of multiple-electrolyte solutions if the ion interaction parameters (Pitzer parameters) for each type of single-electrolyte solutions are known. The purpose of the present paper is to suggest the best sets of volumetric Pitzer parameters, V(MX)oBAR, beta(MX)(O)V, beta(MX)(1)V, beta(MX)(2)V and C(MX)V, at 25-degrees-C for salts formed from Na+, K, Mg2+, Ca2+, Cl-, Br-, HCO3-, CO32- and SO42- ions. Using essentially all published relevant experimental data, a database for the mass densities and apparent molar volumes at 25-degrees-C vs. the solute concentration has been created for each single-electrolyte solution type. Unreliable data were discarded by an appropriate statistical lest. The remaining data, covering solute concentrations from infinite dilution to saturation, were used to compute the unrestricted and restricted sets of volumetric Pitzer parameters by least squares. Taking the differences between the calculated and experimental densities and apparent molar volumes as the criterion of quality , the best set of volumetric Pitzer parameters was selected for each type of electrolyte and was used to calculate the mass densities, at 25-degrees-C, of some multiple-electrolyte solutions resembling Dead Sea waters.