Volumetric properties of H2O, D2O, and methanol in acetonitrile at 278.15-318.15 K

Abstract

The densities of H2O, D2O, and MeOH solutions in acetonitrile with the solute concentrations up to 0.07 molar fractions at 278.15, 288.15, 298.15, 308.15, and 318.15 K were measured using vibrating-tube densimetry with an error ≤8·10–6 g cm–3. The limiting partial molar volumes for the H/D isotopomers of water and IaII in acetonitrile (V– 2 ∞) and the isotope effects in V– 2 ∞ and in excess molar volumes of acetonitrile—water mixtures were calculated. Molecules of H2O, D2O, and IaII form associates with acetonitrile molecules via hydrogen bonds. The associates have the packing volumes close to those in the individual solute. The water and methanol molecules were assumed to be incorporated into the acetonitrile structure without substantial changes in the latter. However, this process results in some compression of the system with a simultaneous increase in its expansibility.