VOLTAMMETRIC STUDY ON THE OSCILLATION OF THE POTENTIAL DIFFERENCE AT A LIQUID/LIQUID OR LIQUID/MEMBRANE INTERFACE ACCOMPANIED BY ION TRANSFER

The oscillations of potential difference at the interface between an aqueous solution (W) containing MgSO4 as a supporting electrolyte (SE) and an organic solution (Org) containing dilute ion i(+) and j(+).Y- as SE were investigated by forcing the transfer of i(+) at the interface through an applied current. The Org employed were Cs+ + tetrapentylammonium tetraphenylborate (TPenA(+).TPliB(-)) in nitrobenzene (NB), tetramethylammonium ion + TPenA(+).TPhB- in NB, H+ + tetraphenylarsonium dipicrylaminate (TPhAs+.DPA(-)) in 1,2-dichloroethane, etc. The necessary conditions for the oscillation were confirmed to be identical to those for the appearance of the maximum in the voltanunogram for the transfer of i(+) at the interface. By referring to the voltammogram and the electrocapillary curve at the interface and taking into account the ion pair (i(+).Y-) formation equilibrium in Org, such characteristics of the oscillation as the amplitude, period, pulse width and range of the applied current available for the oscillation were elucidated, and a mechanism for the oscillation is proposed. The important roles of the adsorption desorption of i(+).Y- at the interface and the dissociation of the desorbed i(+).Y- were emphasized.