Ultrasonic measurements and liquid structure of DMSO–water mixture

Abstract

The ultrasonic absorption of a 30% mole fraction mixture of dimethyl sulfoxide (DMSO) and water was measured at frequencies from 5 to 200 MHz by a pulse echo technique and over the temperature range −80 to 25 °C. At temperatures above −55 °C the observed absorption is greater than the classical value and is due to volume viscosity. To a very good approximation the ratio of the volume viscosity ηv to the shear viscosity ηs is 2/3. Below −55 °C a simultaneously occuring shear and volume relaxation is observed and the data in this region can be fit with a single relaxation time with an activation energy of 7.3 kcal/mol in agreement with that obtained for other hydrogen bonded liquids. No evidence of a distinct DMSO–water complex has been found.