Electrical double layers at the oil/water interface

Electrocapillary curves have been measured of the interface between nitrobenzene solution of tetrabutylammonium tetraphenylborate and aqueous solution of lithium chloride using a dropping electrolyte solution electrode under the precise control of the electrical potential difference and of the ion transfer current across the interface. The nitrobenzene–water interface could be electrically polarized over the voltage span of 300 mV. The residual current was explained as due to both the transfer of tetrabutylammonium ion and tetraphenylborate ion through the interface and the charging current at the interface. The electrocapillary curve was parabolic in shape. The surface charge vs. potential curve derived from the electrocapillary curve agreed with that obtained from the differential capacity vs. potential curve of the interface. The results indicate that the interface can virtually be treated as an ideal polarized interface over a certain potential range.

Polarizability and electrocapillary measurements of the nitrobenzene-water interface.

The adsorption of the hexadecyltrimethylammonium ion(HTMA+) at the polarized nitrobenzene–water interface has been studied using electrocapillary measurements. The adsorption of HTMA+ was found to be markedly dependent on the potential drop across the interface. HTMA+ exhibited no specific adsorption in the potential range where the aqueous phase is positive, whereas a strong adsorption occurred in the potential range where the electric potential in the aqueous phase is negative with respect to that in the nitrobenzene. The adsorption free energy depends linearly on the potential difference across the interface. The specific adsorption of HTMA+ significantly alters the double-layer structure. The outer Helmholtz potential in the nitrobenzene phase was inverted from negative to positive due to the adsorption of HTMA+ ions.

The Effect of the Electrical Potential Difference on the Adsorption of the Hexadecyltrimethylammonium Ion at the Polarized Nitrobenzene–Water Interface

Studies of the properties of vibrating water-nitrobenzene interface

Study of supporting electrolyte adsorption in the water/nitrobenzene partition system: I. A new drop weight technique for interfacial tension measurements

The change of interfacial tension induced by the flow of an electric current through a nitrobenzene-water interface was studied experimentally and theoretically for both ac and dc. The nitrobenzene and water phases contain some hexadecyltrimethylammonium bromide, and a supporting electrolyte (or KBr in the water phase or hexadecyltrimethylammonium picrate in nitrobenzene). The overpotential measured while an electric current flowed through the interface was zero. Concentration changes near the interface were observed, and compared with theory. The interfacial transport number which arises from these measurements as an adjustable parameter is compared with transference numbers in bulk.

Y Verburgh

Papers

Effect of a supporting electrolyte on the interfacial transference numbers during electroadsorption at the nitrobenzene—water interface