Heat capacity of gaseous carbon dioxide

Abstract

The heat capacity (Cv) of gaseo us carbon d ioxide has been measured at -30°, 0°, + 50°, and + 90 ° C and at 0.5-, 1.0-, and lo5-atmosphere pressure, with an accuracy of 0.1 percent. The flow calorimeter used was a modification of the one previously described by Scott and Mellors [1 ] 2 and Wacker , Cheney, and Scott [2] . In order to test the accuracy of t he calo-rimeter, the heat capacity of oxygen was measured at 1 atm osphere at -30°, 0°, and + 50°C. Thc measured values of Cv for oxygen were combined with an equation of sta te to gi ve C;; these differed from the statistically calculated values by + 0.03, -0.06 and -0.01 per cent at the three temperatures. The experimental values of Cv for carbon dioxide have been used to calculate new values of C; and values of t he pressure coefficient of heat capacity at the four temperatures of m easu rement. The theoretical values of C; calculated in 1949 [8] were found to be too low by 0.2 to 0.3 percent ; the results of a new calculation are in substantial agreement with the experiments. The press ure coefficients are in agreement with those obtained from the recent pressure-volume-temperature work of MacCormack and Schneider [7].