The molecular thermodynamic model established by Hu

Xu and Prausnitz was extended to the gas solubility in electrolytic solutions. The influence of ion charge on the Helmholtz energy of fluid mixtures was taken into account by considering the interactions between the charge of ions located in the first coordination shell and the dipole or induced dipole of the central solute molecule. The contribution of the ions outside the first coordination shell can be neglected owing to the symmetrical distribution of the positive and negative ions with respect to the central solute molecule. The model in this paper includes a correlation equation for the effective hard sphere diameter of ions and the Paulings crystal diameter

σ = ησcrycysl

where η= - 6.645 + 747.2511/T + 2.95392 × 10-2T- 5.05798 × 10-5T2 + 3.2431 × 10-8 T3

for T>453.15K

η= 1.021. The results of calculations for 78 systems of gas solubilities in 1-1 type electrolytic solutions indicate that this model can predict the Henrys constants of gases in electrolytic solutions over a wide temperature range and a wide concentration range for electrolytes with the use of molecular parameters of gases in water only.