Thermodynamic Properties of Propane. II. Molar Heat Capacity at Constant Volume from (85 to 345) K with Pressures to 35 MPa

Abstract

Molar heat capacities at constant volume (CV) were measured with an adiabatic calorimeter for pure propane. The high purity of the samples was verified by chemical analysis. Temperatures ranged from the triple point of propane near 85 K to the upper temperature limit of the calorimeter at 345 K, while pressures ranged up to 35 MPa. Measurements were conducted on liquid propane in equilibrium with its vapor and on compressed liquid samples along isochores. Heat capacity results are reported for two-phase (CV(2)), saturated liquid (Cσ), and single-phase (CV) isochores. Vapor pressure data are based on measurements of CV(2) along a two-phase isochore. Measurements were also made to determine the triple-point temperature of (85.525 ± 0.005) K and heat of fusion of (3508 ± 20) J·mol−1 for propane near its triple point. The principal sources of uncertainty in CV are the temperature-rise measurement and the change-of-volume work adjustment. The expanded uncertainty (i.e., a coverage factor k = 2 and thus a two-standard deviation estimate) for values of CV(2) is estimated to be 0.5 %; for both Cσ and CV, it is 0.7 %.