ULTRASONIC DISPERSION AND RELAXATION AND THE BULK VISCOSITY COEFFICIENT OF A LIQUID

A method has been described to evaluate the compressional relaxation time in a liquid from ultrasonic dispersion alone, using the property of the bulk viscosity of the liquid. Available experimental data on ultrasonic dispersions in liquids are used to calculate this relaxation time and hence the intermolecular binding (or activation) energy of the liquid. The bulk viscosity coefficient of the liquid is a complex and frequency-dependent quantity under the action of an ultrasonic wave, and is closely related to the compresional relaxation time of the liquid and the ultrasonic absorption and dispersion in the liquid. The variation of the relaxation time with temperature is evaluated from data on the variation of ultrasonic dispersion in the liquid, with temperature, leading to the evaluation of activation energy. Comparison of calculated values with available values shows fairly good agreement. However the results are found to be very sensitive to the accuracy of the dispersion data.