GIBBS ENERGIES, ENTROPIES AND ENTHALPIES OF TRANSFER FOR DIVALENT-CATIONS TO SEVERAL SOLVENTS

Gibbs energies of transfer for the divalent cations Cu2+, Zn2+, Cd2+, Ba2+ and Pb-2+ from the reference solvent N,N-dimethylformamide have been derived from reversible polarographic half-wave potentials via the bis(biphenyl)chromium assumption. Entropies of transfer were calculated from temperature coefficients of the half-wave potentials employing the assumption of a negligible thermal diffusion potential. Enthalpies of transfer were calculated from the equation Delta(t)H degrees = Delta(t)G degrees + T Delta(t)S degrees. Thermodynamic transfer properties for Cu2+, Zn2+ Cd2+, Ba2+ and Pb2+ for up to 23 solvents were obtained. The Gibbs energies of transfer and the enthalpies of transfer reflected the principle of hard and soft acids and bases; the entropies of transfer of the divalent cations depended linearly on each other for all solvents. The solvent effects on the transfer properties are accounted for as first-sphere interactions between the cations and the solvent molecules and by interactions of these entities with the surrounding solvent matrices.