Toward a simple molecular theory of hydrophobic hydration

A perturbation theory of water is extended to mixtures, and its application to aqueous solutions of noble gases is presented. The present approach is based on the thermodynamic perturbation theory of the primitive models of associating fluids, substituting the reference pseudo-hard-body term by a hard-sphere/pseudo-hard-body mixture term and introducing appropriate corrections. The primitive models are constructed in a rigorous way from realistic parents. The procedure yields equations of state allowing for the determination of all residual properties. The residual chemical potential is expressed and subsequently the Henry's law constants of noble gases, from He to Xe, are evaluated as functions of temperature showing qualitative agreement with experimental data. Throughout the procedure, no experimental data are used to adjust the parameters or to fine-tune the results.