Polarizability and Electrocapillary Measurements of the Nitrobenzene–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.