ULTRASONIC-ABSORPTION AND SOUND-VELOCITY OF DIMETHYL-SULFOXIDE WATER MIXTURES IN THE COMPLETE COMPOSITION RANGE

At 25°C the ultrasonic absorption coefficient and the sound velocity of dimethyl sulfoxide/water mixtures have been measured for various mole fractions between 0 and 1. The measurements of the absorption coefficient have been performed as a function of frequency between 200 kHz and 2.75 GHz. The sound velocity has been determined by three methods at different frequencies of the above range. At given mole fraction the absorption per wavelength increases linearly with frequency and the sound velocity is constant. Thus no relaxation process is found which could be attributed to the suggested formation of stoichiometrically well-defined dimethyl sulfoxide/water complexes. The volume viscosity and the adiabatic compressibility are derived from the measured quantities. The dependence upon the mixture composition is discussed together with other ones to show that there are special mixture properties at mole fractions around 30 % dimethyl sulfoxide. The mixtures, however, seem to be homogeneous hydrogen-bonded networks rather than being composed of definite molecular complexes. © 1990.