HEAT CAPACITY AND VAPOR PRESSURE OF CRYSTALLINE BIS(BENZENE)CHROMIUM . THIRD-LAW ENTROPY COMPARISON AND THERMODYNAMIC EVIDENCE CONCERNING STRUCTURE OF BIS(BENZENE)CHROMIUM

Heat capacity measurements from 5 to 350° K and vapor pressure measurements on bis(benzene)chromium together with the published frequency assignments permit a correlation between the third-law and spectroscopic entropies. Neither thermal anomalies nor zero point entropy were found. The agreement is consistent with free rotation about the ring to metal bonds and D6h symmetry for the molecule as proposed by Cotton. The thermodynamic functions for the crystal at 298.15°K are 53.52, 54.07, 26.77, and -27.30 cal · mole-1 °K-1 for the heat capacity, entropy, enthalpy function, and Gibbs function, respectively. The vapor pressure over the range 310 to 365°K is represented by log10p (mm) = 27.42-5451/T-5.535 log10T, (T in °K). © 1969.