SALT EFFECT ON THE TRANSFER OF IONS AT LIQUID/LIQUID INTERFACE STUDIED BY POLAROGRAPHY WITH AQUEOUS ELECTROLYTE DROPPING ELECTRODE

The ion transfer polarography was applied to investigate the dissolved state of a diluted ion, i(z), which is rather hydrophobic, in an aqueous solution in the presence of concentrated hydrophilic ions. The effect of coexisting ions on the dissolved states of i(z) was evaluated based on the electrostatic and non-electrostatic contributions on the solvation energy of i(z) and ion-pair formation of i(z) with a coexisting counter ion. The change in the electrostatic contribution was attributed to the dehydration of i(z) resulted from the decrease of water activity due to the hydration of the coexisting ions. The change in the non-electrostatic contribution was explained by the variation of the cavity formation energy and the dispersion force with the change of the concentration of coexisting ions. The ion-pair formation of i(z) with the coexisting ion is more serious when i(z) is more hydrophobic.