Heat capacities, enthalpy increments, phase transitions, and derived thermodynamic functions for the condensed phases of bicyclohexyl between the temperatures 6 K and 440 K

Heat capacity and enthalpy measurements by using adiabatic calorimetry for temperatures between 6 K and 440 K are reported for bicyclohexyl (Chemical Abstracts registry number [92-51-3]). The triple point temperature and the enthalpy of fusion were determined. Two different phase-change sequences in the solid state were observed depending upon the thermal history of the sa mple. Discord between literature values for temperatures and enthalpies of phase transitions are shown to be due to hysteresis effects. Entropies and enthalpies for the condensed phases relative to T --> 0 are reported. Resul ts are compared with literature calorimetric and spectroscopic studies. The stability relationships between the known phases of crystalline bicyclohex yl are established. Planned publications in this series will include report s of measurements leading to the calculation of standard molar Gibbs energi es of formation for bicyclohexyl and phenylcyclohexane, and a revised therm odynamic analysis of the (biphenyl + hydrogen) reaction network. (C) 1998 A cademic Press.