Molar Heat Capacity at Constant Volume of n-Butane at Temperatures from 141 to 342 K and at Pressures to 33 MPa

Abstract

Molar heat capacities at constant volume (CV) for normal butane are presented. Temperatures ranged from 141 to 342 K for pressures up to 33 MPa. Measurements were conducted on liquid in equilibrium with its vapor and on compressed liquid samples. The high purity of the samples was verified by chemical analysis. For the samples, calorimetric results were obtained for two-phase [Cv(2)], saturated liquid (Cσ or C′x), and single-phase (CV) molar heat capacities. The principal sources of uncertainty 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 is estimated to be 0.7%, for Cv(2) it is 0.5%, and for Cσ it is 0.7%.