Volumetric (PVT) and Calorimetric (CVVT) Measurements for Pure Methanol in the Liquid Phase

Volumetric (PVT) and calorimetric (CVVT) properties of pure methanol were measured in the liquid phase with a twin-cell adiabatic calorimeter. Temperatures were measured in a range from 314 to 411 K, densities between 699.3 and 775.6 kg ·m−3, and pressures to 20 MPa. The calorimetric cell (70 cm3 capacity) was surrounded by adiabatic thermal shielding (high vacuum). The sample pressures were measured by means of a quartz crystal transducer to within an uncertainty of about ±7 kPa. The relative uncertainty of CV was estimated to be 2%, with a coverage factor k=2, by combining the various sources of experimental uncertainty using a root-sum-of-squares formula. The results for pure methanol were compared with other recent measurements performed with a second high-temperature, high-pressure adiabatic calorimeter. Deviations of less than 3% were found between the earlier CV data and the present results for pure methanol. The uncertainty of the density measurements was estimated to be 0.2% (k=2). The measured densities and isochoric heat capacities were compared with values calculated with an IUPAC equation of state. Agreement of density was within 0.088% and that for isochoric heat capacity was within 0.95%. Values of vapor pressure were determined by extrapolating experimental P–T data to the saturated temperature along a fixed isochore. In the temperature range of this study, decomposition of methanol was not observed