Thermodynamic Properties of Sulfuryl Fluoride from 12°K to Its Boiling Point. Entropy from Molecular and Spectroscopic Data

The heat capacity of sulfuryl fluoride has been measured from 12 to 218°K. A lambda transition was observed at 65.7°K. The heat of fusion at the triple-point temperature, 137.34°K, was 1074 cal/mole. The heat of vaporization at the normal boiling point, 217.78°K, was 4596 cal/mole. The vapor pressure data are closely represented by the equation log10Pmm=7.8323−1071.235/T−0.01391 log10T.The liquid density from 182 to 204°K is closely represented by the equation d=2.576−0.004044T.The entropy of sulfuryl fluoride gas has been calculated from the calorimetric data and the third law of thermodynamics to be 62.66 eu/mole at 217.78°K. The calculated spectroscopic entropy was 63.24 eu/mole. The discrepancy, 0.58 eu/mole is attributed to randomness in the solid at 0°K.