SOME THERMODYNAMIC PROPERTIES OF C-76 AND C-84

The vapor pressures of C-76 were measured over the temperature range 8 34-1069 K by the torsion-effusion method. The results are well represe nted by the following linear equation: log(p/kPa) = (8.23 +/- 0.20) - (10150 +/- 150)/(T/K). The standard sublimation enthalpy of this compo und, Delta(sub)H degrees(298) = 206 +/- 4 kJ mol(-1), as derived by se cond-law elaboration of the experimental data, is proposed. Some struc tural aspects of C-76 and C-84 crystals were investigated by X-ray ana lysis. Considerations on the thermodynamic properties of these compoun ds are also reported.