A revisit to the non-Bornian theory of the Gibbs energy of ion transfer between two immiscible liquids

Previously, Osakai and Ebina (1998) proposed a non-Bornian theory for the Gibbs energy ( Δ G tr ° ,W → O ) of ion transfer at the organic solvent/water interface. In a conventional manner, however, Δ G tr ° ,W → O was divided into ionic charge-dependent and -independent terms. The former was formulated based on non-Bornian, short-range interactions of an ion with primary solvent molecules, while the latter was evaluated as the energy of cavity formation by using the Uhlig formula. In this study, we have successfully shown that the above two terms can be brought together in the context of short-range ion–solvent interactions, and that the Δ G tr ° ,W → O scaled by the ionic surface area can be given by a quadratic function of the surface field strength of the ion. The obtained semiempirical equation of Δ G tr ° ,W → O is very simple, and would be useful for the prediction of Δ G tr ° ,W → O .