Excess molar volumes and densities of (methanol+water) at temperatures between 323 K and 573 K and pressures of 7.0 MPa and 13.5 MPa

Densities of {xCH3OH+(1−x)H2O} relative to water were measured in a vibrating-tube densimeter at the temperatures (323,373,423,473,523, and 573) K and at pressures of 7.0 MPa and 13.5 MPa. Excess molar volumesVmEfor {xCH3OH+(1−x)H2O} were calculated from the experimental densities for the mixtures, using accurate equations of state for water and methanol. The data were treated with a modified corresponding-state model based on the properties of pure water. An empirical function was used to fit small differences between the compression factors of {xCH3OH+(1−x)H2O} and the compression factor of H2O at the same reduced temperature and the same reduced pressure. The corresponding-states treatment reproduces the measured densities to within the experimental uncertainty of 0.4 kg·m−3at all of the temperatures and pressures studied, except atT=573 K andp=13.5 MPa. The densities, excess molar volumes, partial molar volumes, isothermal compressions, and cubic expansion coefficients from the model are consistent with the limited literature data available. The behaviour ofVmEatT=573.6 K andp=13.7 MPa indicates either a very narrow region of (vapour+liquid) phase separation, or near-critical behaviour atx≈0.44 with the critical pressurepc≤13.5 MPa.