Recent developments in the electroacoustic characterisation of colloidal suspensions and emulsions

The electrokinetic sonic amplitude (ESA) effect, in which a sound wave is generated in a colloidal system by the application of an alternating electric field, provides a powerful method for characterizing colloidal suspensions. The key parameter is that particle dynamic mobility which can be determined accurately in suspensions of essentially any concentration above about 1% by weight. This quantity can then be related to characteristics like particle size and the zeta potential on the particle surface. Since the electroacoustic measurement provides the magnitude and phase angle of the dynamic mobility over a range of frequencies it is, in principle, capable of supplying more information than direct-current electrophoretic mobility measurement.; The ESA effect, in which a sound wave is generated in a colloidal system by the application of an alternating electric field, provides us with a powerful method for characterising colloidal suspensions. The key parameter is the particle dynamic mobility which can be determined accurately in suspensions of essentially any concentration above about 1% by weight. This quantity can then be related to such important characteristics as the particle size and the zeta potential on the particle surface. Theoretical analyses have been provided to cover particles of almost any shape. The currently available apparatus can measure particle sizes in the range from about 0.1 to 10 μm and the zeta potential of particles down to nanometer dimensions. Since the electroacoustic measurement provides both the magnitude and the phase angle of the dynamic mobility over a range of frequencies it is, in principle, capable of supplying much more information than is a d.c. electrophoretic mobility measurement.