Thermodynamic Properties of Carbon Tetrafluoride from 4°K to Its Melting Point

Abstract

Abstract Thermodynamic properties of solid and liquid carbon tetrafluoride were measured at temperatures from 4°K to 100°K. The heat of transition was found to be 349.5±0.9 cal/mol, the transition temperature 76.221°K, the heat of fusion 168.6±0.05 cal/mol, the triple point temperature 89.515°K and the triple point pressure 0.80±0.03 Torr. The amount of impurity in the specimen of CF4 was estimated to be 0.0147 mol% from the measurement of the melting point range. The values of molal entropy of CF4 as an ideal gas at 298.2°K, were calculated from the calorimetric and spectroscopic data as 62.63 e.u. and 62.45 e.u., respectively. The Debye characteristic temperature at 0°K was derived from the low temperature heat capacity data, and the θD(T) curve was compared with that for neopentane taking into account the octupole interaction of molecules in the crystal.