Excess molar enthalpies and the thermodynamics of (methanol + water) to 573 K and 40 MPa

Abstract

Excess molar enthalpies H m E of (methanol + water) were measured from 298 to 573 K at pressures from 7 to 40 MPa. The observed H m Es are significantly negative at 298.15 K, near zero at about 398 K, and positive at higher temperatures. The composition dependence of H m E at low temperatures is much simpler than for (ethanol or propanol + water). The measurements reported here extend above the critical temperature of methanol. The very large changes in H m E with temperature and composition often observed near the critical conditions of the more volatile component were not observed under the conditions of this study. The results reported here were combined with available measured values of other thermodynamic quantities and represented with thermodynamically consistent empirical functions of temperature, pressure, and composition. Calculated excess molar Gibbs free energies, excess molar volumes, excess molar enthalpies, and excess molar heat capacities are tabulated.