Low-temperature heat capacity and the thermodynamic properties of 1,1,2-trifluoro-1,2-dichloroethane

The heat capacity (C-p, (m)) of coolant X-123a (CF2ClCHFCl) was measured in the temperature range 58.6-296.3 K by the method of adiabatic calorimetry. The temperature of transition from the vitreous to the supercooled liquid state (T-g 86.5 K), the triple point temperature (T-tp = 135.74 +/- 0.19 K) , and the enthalpy and entropy of fusion [Delta(fus)H(m) = 7.08 +/- 0.13 kJ /mol and Delta(fus)S(m) = 52.16 +/- 0.71 J/(mol K)] were determined. The ca lculated C-p,C- m values in the temperature range 8.5-58.6 K and the experi mental heat capacity values were used to calculate the S-m(o)(T)- S-m(o)(0) , {H-m(o) (T)-H-m(o) (0)}, and -{G(m)(o) (T)-H-m(o) (0)} thermodynamic func tions and the m m m entropy of formation of 1,1,2-trifluoro-1,2-dichloroeth ane in the gas phase at 298.15 K.