ABSTRACT
Several methods of surface tension measurement are based on the measurement of the static shape of an axisymmetric drop or bubble or on the point of mechanical instability of such drops or bubbles. Measurement of the pull of a liquid surface directly on a solid object is the basis for two of the standard methods are discussed. The increased accuracy and simplicity of the automated pendant drop procedure makes it a very flexible method that has been applied to measure ultralow interfacial tensions, pressure, temperature and time dependence of interfacial tension, relaxation of adsorption layers, measurement of line tensions, and film-balance measurements. The spinning drop method is a shape-measurement method similar to the pendant and sessile drop methods. For a dilute solution, the rate of change of surface tension is often slow enough that automated versions of static methods such as the Wilhelmy plate or pendant drop methods can be used to follow the changes in surface tension.
