Time-resolved measurement of equilibrium surface tensions at the electrified mercury-aqueous sodium fluoride interphase by the method of Wilhelmy

Abstract

The Wilhelmy plate technique for measuring static and dynamic surface tensions was extended to the electrified mercury-aqueous electrolyte interphase. Several modifications to a conventional Wilhelmy plate are described, which were necessary to implement the technique within an electrochemical environment. Proper isolation of the Wilhelmy plate and associated instrument from vibration allowed sensitivities to be reached that were about 5 times greater than those attainable with maximum bubble pressure measurements. The surface tensions at the electrified mercury-aqueous NaF interphase measured with the modified Wilhelmy plate instrument agreed well with literature values. The capability of the instrument described for making rapid measurements of surface tensions was exploited to observe intrinsic fluctuations in the equilibrium surface tensions. The importance of intrinsic fluctuations and time-averaging for precise evaluation of the equilibrium surface tension are discussed.