Ultrasonic absorption properties of methyl cyanide + water mixtures

Abstract

Ultrasonic absorption properties have been determined for water + methyl cyanide mixtures at 273, 298 and 308 K and over the frequency range 1.5-230 MHz using a travelling pulse technique, and qualitatively examined at 298 K over the range 200–1 500 kHz using a reverberation apparatus. Sound velocities in these mixtures have been measured at 273, 298 and 308 K and at 2 MHz using an acoustic interferometer. The variation of ultrasonic absorption with frequency (1.5-230 MHz) is analyzed in two ways; (i) assuming that there are two discrete relaxation frequencies, and (ii) using an expression which follows from a treatment by Romanov and Solovyev of concentration fluctuations. The latter analysis has the advantage that it identifies those mixtures where the volume, Gibbs function and enthalpy control the magnitude of the sound absorption. The analysis provides interaction lengths l_m and diffusion coefficients, D, for methyl cyanide + water mixtures.