Mean Ionic Activity Coefficients and Dissociation Constant of HCl in the System HCl-H2SO4-H2O at 298 K

The mean ionic activity coefficients of HCl (_1±) in the system HCl-H₂SO₄-H₂O at 298 K were calculated by the Mikulin and MacKay-Perring methods and were then used for calculating the mixed thermo- dynamic dissociation constant of HCl (K_m). The mean value of the constant proved to be equal to that found previously for aqueous solution of HCl, and deviations from the mean value are most likely due to the fact that, when calculating K_m, incompleteness of dissociation of both electrolytes was neglected. The _1± values calculated by the MacKay-Perring and Mikulin methods virtually coincide, within the determination and calculation errors, with the published data. This result confirms the suitability of the previously suggested procedure for determining the strictly thermodynamic mixed dissociation constants from the experimental data on the vapor pressure in combination with the mean ionic activity coefficients.