Activity and osmotic coefficients from the EMF of liquid membrane cells. VI-ZnSO4, MgSO4, CaSO4, and SrSO4 in water at 25?C

The activity coefficients of ZnSO₄, MgSO₄, CaSO₄, and SrSO₄ are measured by means of cells with ion-exchange liquid membranes similar to those described in the previous papers of this series. Negative deviations from the limiting law are observed in the dilute region. These deviations are, for ZnSO₄, appreciably more important than recent literature has indicated, and the corresponding activity coefficients need to be corrected by about 12%. Pitzer’s theory best-fit coefficients have accordingly been recalculated. The osmotic coefficients are also derived. Accessory information on the hydration state for zinc, magnesium, and sulfate ions, is presented.