The heat capacity of thionyl fluoride has been measured from 12° to 230°K for a sample of 99.976 mole% purity as determined by the melting‐point method. The heat of fusion was 1505.9 cal/mole at the solid—liquid—vapor equilibrium temperature of 143.25°K. The heat of vaporization at the normal boiling point of 228.84°K was 5091 cal/mole. The vapor pressure of the liquid to the normal boiling point has been measured, and the data are represented by which was obtained by minimizing the square of the residuals of the pressure.
The density of the liquid is represented by d(g/cc)=2.389–0.003398T.
The entropy of thionyl fluoride gas in the standard state at the normal boiling point calculated from the experimental data is 63.56 cal/(mole·°K). A spectroscopic entropy of 63.28 cal/(mole·°K) is calculated from the product of the moments of inertia, IAIBIC=1.6562×10−114 g3·cm6 from microwave data and the following frequency assignment: v1(a′)=1336 cm−1; v2(a′)=808 cm−1; v3(a′)=530 cm−1; v4(a′)=378 cm−1; v5(a″)=748 cm−1; and v6(a″)=396 cm−1. The discrepancy between the two entropies is accountable in terms of the experimental uncertainty and therefore, the molecular parameters and frequency assignment are confirmed.
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1965
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