Temperature Coefficient of Hypersonic Sound and Relaxation Parameters for Some Liquids

Abstract

The spontaneous Brillouin effect has been used to determine the variation of sound speed with temperature in the temperature range of − 30° to + 160°C above the relaxation frequencies in dibromomethane, dichloromethane, and carbon disulfide, below any relaxation frequency of acetone and nitrobenzene, and in the region of dispersion in chloroform, carbon tetrachloride, benzene, and acetic acid. In some cases the speeds have been corrected for dispersion. The temperature coefficient of sound and the parameters that characterize the relaxation have been evaluated and compared with other determinations. The sound speeds as a function of temperature have also been measured in water and five viscous liquids; 1‐octanol, ethylene glycol, aniline, glycerol, and pentachlorobiphenyl. A simplified form of the Isakovich–Chaban theory involving a single temperature‐dependent relaxation time has been used to predict the dispersion in glycerol and pentachlorobiphenyl and the amplitude absorption coefficient in glycerol from ultrasonic data. The predicted speeds are in quantitative agreement with the measured values. The observed amplitude absorption coefficient is shifted to higher temperature as the more complete theory of Isakovich and Chaban would predict.