DISSOCIATION CONSTANTS AND SPECIATION IN AQUEOUS LI2SO4 AND K2SO4 FROM MEASUREMENTS OF ELECTRICAL CONDUCTANCE TO 673 K AND 29 MPA

Abstract

The electrical conductivities of aqueous solutions of Li2SO4 and K2SO4 have been measured at 523-673 K at 20-29 MPa in dilute solutions for molalities up to 2 × 10-2 mol kg-1. These conductivities have been fitted to the conductance equation of Turq, Blum, Bernard, and Kunz with a consensus mixing rule and mean spherical approximation activity coefficients. In the temperature interval 523-653 K, where the dielectric constant, ε, is greater than 14, the electrical conductance data can be fitted by a solution model which includes ion association to form MSO4-, M2 S O40, and HSO4-, where M is Li or K. The adjustable parameters of this model are the first and second dissociation constants of the M2SO4. For the 673 K and 300 kg m-3 state point where the Coulomb interactions are the strongest (dielectric constant, ε = 5), models with more extensive association give good fits to the data. In the case of the Li2SO4 model, including the multi-ion associate, Li16 (SO4)80, gave an extremely good fit to the conductance data. © 2006 Elsevier Inc. All rights reserved.