Isochoric heat capacity measurements for 2,2-dichloro-1,1,1-trifluoroethane (R123) at temperatures from 167 to 341 K and 1-chloro-1,2,2,2-tetrafluoroethane (R124) from 94 to 341 K at pressures to 35 MPa

Molar hear capacities at a constant volume (C-v) of 2,2-dichloro-1,1,1-trif luoroethane (R123) and 1-chloro-1,2,2,2-tetrafluoroethane (R124) were measu red with an adiabatic calorimeter. Temperatures ranged from 167 K for R123 and from 94 K for R124 to 341 K, and pressures were up to 33 MPa. Measureme nts were conducted an the liquid in equilibrium with its vapor and on compr essed liquid samples. The samples were of a high purity, verified by chemic al analysis of each fluid. For the samples, calorimetric results were obtai ned for two-phase (C-v((2))), saturated liquid (C sigma or C-x'), and singl e-phase (C-v) molar heat capacities, The C-sigma data were used to estimate vapor pressures for values less than 100 kPa by applying a thermodynamic r elationship between the saturated liquid heat capacity and the temperature derivatives of the vapor pressure. Doe ro the tendency of both R123 and R12 4 to subcool, the triple-point temperature (T-tr) and the enthalpy of fusio n (Delta H-fus) could not be measured. The principal sources of uncertainty al e the temperature rise measurement and the change-of-volume work adjust ment. The expanded uncertainty (at the 2 sigma level) for C-v is estimated to be 0.7%, for C-v((2)) it is 0.5%, and for C-sigma it is 0.7%.