In conventional chemical engineering thermodynamic modeling of phase equilibrium, we are interested in the activity coefficient of the components in the mixture, and the excess Gibbs free energy of the mixture. Coincidentally, values of the solvation free energy are not directly measured experimentally. Rather, it is common to measure limiting activity coefficients from which one may obtain the solvation free energy. The limiting activity coefficient is related to the transfer free energy of a single solute from a system of pure liquid solute to a solution phase at infinite dilution. Moreover, limiting activity coefficients may be related directly to the parameters in common binary interaction excess Gibbs free energy models used to model phase equilibrium.