( p, Vm, T, x) measurements for [(1 − x)H 2O + xCH 3OH] in the range 278 to 323 K and 0.1 to 280 MPa II. Thermodynamic excess properties

Abstract

Excess molar volumes are reported for [(1 − x)H 2O + xCH 3OH] from 0.1 MPa to 275 MPa at 278.15, 288.15, 298.15, 313.15, and 323.15 K. The values are used to calculate changes in the excess molar Gibbs energy, the excess molar enthalpy, and the excess molar entropy. Literature excess molar Gibbs energies and an excess molar enthalpy at 0.1 MPa are used to obtain the excess molar Gibbs energy and excess molar entropy under pressure. There is good agreement between the changes in excess molar enthalpy at 298.15 K and 50 MPa with literature values obtained directly. Systematic differences between the present excess molar volumes and limited literature values for x = 0.5 are attributed to difficulties in the experimental method used to obtain the latter. A comparison with [(1 − x)H 2O + xCH 3CN] at 298.15 K shows virtually no similarities in the dependence of the excess quantities on composition. It is unlikely that the (unbonded) accommodation of acetonitrile in the water structure thought to occur in (water + acetonitrile) has an analogue in (water + methanol).