Activity and Osmotic Coefficients from the Emf of Liquid-Membrane-Cells. VII : Co(ClO4)2, Ni(ClO4)2, K2SO4, CdSO4, CoSO4, and NiSO4.

The activity coefficients of CdSO4 CoSO4, and NiSO4 are determined from the emf of liquid-membrane cells, like those described in the papers I–VI of this series. The activity coefficients of the auxiliary salts Co(ClO4)2, Ni(ClO4)2, and K2SO4, needed to eliminate the problem of extrapolation to infinite dilution of the 2–2 salts, are also measured. CdSO4 CoSO4 and NiSO4 in the dilute region deviate downward from the limiting law by a larger extent than believed in the past, thus creating the need for the activity coefficients to be recalculated and systematically lowered by 8–16%. The activity coefficients of Co(ClO4)2 and Ni(ClO4)2, too, need to be corrected by around –3%. For K2SO4, the original values, although scattered, were substantially correct. Pitzer's theory best-fit parameter, able to provide the activity and osmotic coefficients of the salts considered, are reported.