Thermodynamic properties of methanol in the critical and supercritical regions

The isochoric heat capacity of pure methanol in the temperature range from 482 to 533 K, at near-critical densities between 274.87 and 331.59 kg(.)m(-3), has been measured by using a high-temperature and high-pressure nearly constant volume adiabatic calorimeter. The measurements were performed in the single- and two-phase regions including along the coexistence curve. Uncertainties of the isochoric heat capacity measurements are estimated to be within 2%. The single- and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from experimental data for each measured isochore. The critical temperature (T-c = 512.78 +/- 0.02K) and the critical density (rho(c) = 277.49 +/- 2 kg(.)m(-3)) for pure methanol were derived from the isochoric heat-capacity measurements by using the well-established method of quasi-static thermograms. The results of the CVVT measurements together with recent new experimental PVT data for pure methanol were used to develop a thermodynamically self-consistent Helmholtz free-energy parametric crossover model, CREOS97-04. The accuracy of the crossover model was confirmed by a comprehensive comparison with available experimental data for pure methanol and values calculated with various multiparameter equations of state and correlations. In the critical and supercritical regions at 0.98T(c) <= T <= 1.5T(c) and in the density range 0.35 rho(c) <= rho <= 1.65 rho(c), CREOS97-04 represents all available experimental thermodynamic data for pure methanol to within their experimental uncertainties.