On the mean spherical approximation for hard ions and dipoles

The analytical solution of the Mean Spherical Approximation for the case of equal size ions and different size solvent is reexamined using only two parameters: a polarization parameter lambda and a screening parameter gamma. We show that the ion dipole cross energy parameter, which in previous work was obtained solving a cubic equation, can be obtained from a linear algebraic equation. Therefore, the inverse problem of calculating the reduced charge parameter d sub 0 and the reduced dipole parameter d sub 2 from lambda and gamma is reduced to a system of two equations: a cubic for d sub 0, and a linear for d sub 2. Simpler expressions for the thermodynamic parameters are also obtained.