Improved calculation techniques for interfacial tensiometers

Abstract

Improved techniques for calculating the interfacial tension of liquids using the capillary rise and maximum bubble pressure methods have been developed. The methodology may be extended to other methods including the differential bubble pressure, drop weight, Du Noüy ring, pendant drop, and sessile drop methods. The technique includes a different scaling of the pressure balance equation than originally used by Bashforth and Adams. When integrated, the scaled pressure equation describes interface geometry as a function of Eötvös number (Eo), a measure of the relative magnitudes of gravitational and surface tension forces. For the range of Eo in which most capillary rise and maximum bubble pressure experiments are performed, the dependence on Eo can be represented with a maximum error of 0.008% by a third order expansion in Eo. This new relation eliminates the need for tables and iterative solutions for determining interfacial tension from measured quantities when using either the capillary rise or maximum bubble pressure method.