Measurement of the Surface and Interfacial Tension from Maximum Volume of a Pendant Drop

Abstract

Described herein is a two-phase nonempirical method for the determination of surface or interfacial tension of stationary systems that also allows the determination of drop correction factor. The method is based on the theoretical calculation of the drop profile associated with the maximum volume of a pendant drop on a cylindrical capillary. The capillary constant and the drop correction factor are calculated from measured maximum drop volume. The accuracy and the reproducibility of the method are demonstrated by comparison of surface tension data obtained for bidistilled water, ethanol, n-hexane, and toluene with values resulting from independent reference measurements using sphere tensiometry, cylinder tensiometry, and the drop detachment method. For measurements of the interfacial tension of 1-octanol versus water, drop detachment and sphere tensiometry were used as reference techniques. The drop correction factors arecompared with the values calculated by polynomial approximation of the drop correction factor function f(r/vf1/3) introduced by W. D. Harkins and F. E. Brown (J. Am. Chem. Soc.41, 499, 1919).