Differential capacitance of liquid/liquid interfaces: effect of electrolytes present in each phase

Abstract

The effect of electrolyte type and concentration on the differential capacitance of the 1,2-dichloroethane/water interface has been measured. The results show that the differential capacitance is controlled by the pair ion (1)–counter-ion (2), where 1 and 2 denote the different phases. At constant organic electrolyte composition the capacity increases in the order, F^– <SO^2–₄ < HO^– < ClO^–₄, Li⁺ <H⁺ <K⁺ <Mg²⁺ < Ba²⁺ < Sr²⁺≈ Ca²⁺. By contrast, at positive potentials and constant aqueous electrolyte composition, the capacitance decreases in the order, TPA⁺ > MTMA⁺ > TBA⁺ > TOA⁺, TPB^– > TCPB^–. In very dilute solutions, the effects are not noticeable.