Study of the System Acetonitrile-Water in the One-Phase Pretransitional Region

Abstract

Acetonitrile-water mixtures have often been employed as solvent media. Although their behaviour has previously been investigated by use of a variety of experimental techniques at several temperatures, relatively little is known of their general properties in the one-phase precritical and critical regions. The coexistence curve has been previously published. The system ace-tonitrile-water has an upper critical solution temperature at 272.1K when the mole fraction of water is 0.62 (Schneider, 1964; Armitage et al., 1968). Densities, viscosities and static dielectric constants of acetonitrile-water mixtures have only been determined up to 278.15K (Moreau et al., 1975, 1976). An extension of such measurements into the precritical and critical regions was desirable in order to gain a better understanding of the structural interactions in these binary hydroorganic solutions. Thus it was undertaken to measure the density (ρ), the viscosity (η) and the static dielectric constant (ε) at normal pressure up to the transition temperature, within 4 degrees of the critical temperature, for the acetonitrile-water mixtures with the composition in the mole% of water range 40<x<82.