Thermodynamic Properties of Trifluoroiodomethane (CF13I)1

Studies of the thermodynamic properties of trifluoroiodomethane (CF3I) are preseInted in this paper. The vapor liquid coexistence curve of CF3I was measured by visual observation of the meniscus. The critical temperature and the critical density of CF3 I were determined by considering not only the level where the meniscus disappeared but also the iIntensity of the critical opalescence. The correlation of the saturated density in the critical region was developed, and the exponent of the power law ; was determined. Correlations of the saturated vapor and liquid densities and the enthalpy of vaporization for CF3 I were also developed. The vapor pressure of CF3 I was measured at temperatures ranging from below the normal boiling point to the critical point, and a vapor pressure equation for CF3 I was developed, from which the normal boiling point of CF3 I was determined. The gaseous PVT properties of CF3 I were measured with a Burnett isochoric method, and a gaseous equation of state for CF3 I was devel- oped. The speed of sound of gaseous CF3I was measured with a cylindrical, variable-path acoustic iInterferometer operating at 156.252 kHz, and the ideal- gas heat capacity and second acoustic virial coefficient were calculated. A cor- relation of the second virial coefficient for CF3 I was obtained by a semiempiri- cal method using the square-well potential for the iIntermolecular force and was compared with the result based on PVT measurements. The surface tension of CF3 I was measured with a differential capillary rise method (DCRM), and the temperature dependence of the results was successfully represeInted to within \0.13 mN} m&1 using a van der Waals correlation.