While the formulation of cavity formation for hard body (HB) fluids was widely expanded, less investigations have been done with respect to the real fluids. Formally the analytical expressions of chemical potential of a HS solute in a HB fluid are used for prediction of the free energy of cavity formation for real fluids. Successful application of these relations for real systems needs true adjustment of the effective hard sphere diameters (EHSD) of solute and solvent molecules. Since the arbitrarily determination of this parameter obscures subject, a reliable method for calculating of true values of EHSD which should be used in analytical expressions of CFE for HS systems is highly required. In this work a unique approach for prediction of the values of CFE for real systems is presented. The validity of the Pierotti’s assumption which ignores the entropy of solute-solvent interaction (i.e. Eint ≈ Gint) as the first application of the present approach, is investigated.
