Dielectric and Ultrasonic Relaxation in Glycerol

Abstract

Measurements of dielectric and ultrasonic relaxation in glycerol are compared over a frequency range of 7.5 to 37.5 megacycles and over a temperature range from 20°C to − 25°C. Reduced dielectric and ultrasonic constants when plotted against viscosity at a constant frequency of 30 megacycles appeared quite similar. The imaginary (or loss) part of the reduced constants exhibited a peak at the same viscosity. Both phenomena exhibited a departure from a single relaxation time theory. This deviation of the dielectric phenomena from the simple theory was attributed in the usual manner to a distribution of relaxation times. The striking similarities in the behavior of the dielectric and ultrasonic phenomena suggests an intimate relation between the two. Thus, if a distribution of relaxation times exists for the dielectric, it should in all probability exist in the ultrasonic process. Both shear and compressional viscous processes are associated with the acoustic phenomena. It was concluded that if any difference exists in the shear and compressional viscous relaxation times, its effect is masked by a probable distribution in relaxation times for each process. Calculations indicated that the natural ``rotational jump'' time in glycerol is between ½ and 4 times the ``translational (or viscous) jump'' time.