Electrocapillary Measurements in the Presence and Absence of Superimposed A‐C Potential

Abstract : Recent discussions on the discrepancies which exist between double layer adsorption parameters determined from electrocapillary measurements and differential capacitance measurements are considered. Electrocapillary curves have been determined by the classical method of 'maximum bubble pressure' recommended by Schiffrin. An electronic detector has been added using a.c. signal across the interface to determine the instant when the first mercury droplet begins to grow. Comparison of curves obtained by visual and electronic detection shows that, within experimental error, the a.c. has no effect on the measured interfacial tension. It is concluded that the commonly observed discrepancies arise from a finite, changing contact angle at the mercury-glass-solution interface in the Lippmann capillary electrometer. (Author)