Excess free energy changes for binary mixed electrolytes at vanishing ionic strengths

The mixing coefficients g k for expressing the increase in excess free energy on forming a mixture are used to express the activity coefficients and the osmotic coefficients of the mixtures. A successive interpolation method is used to compute these coefficients at vanishing ionic strengths for the series HBr + NBr 2 at 25°C. The behaviors of the mixing coefficients at vanishing concentrations are studied and compared with those computed from the higher‐order limiting laws and the primitive model with zero core diameter in the Mayer‐Friedman cluster theory for ionic solutions. Our results also agree with those from the HNC calculations together with the higher‐order limiting law.