Calorimetric investigations of plastic crystals at low temperatures and high pressures with differential scanning calorimetry

Abstract

A new high-pressure low-temperature differential scanning calorimeter (d.s.c.) has been developed. The calorimeter has been designed for the investigation of some plastic crystals over wide ranges of temperature and pressure,e.g., between 100 and 450 K at normal pressure and 100 and 300 K at 4 kbar. This d.s.c. apparatus has been applied to the determination of transition temperatures and transition enthalpies of cyclohexane, 1,3-dimethyladamantane, and 1,3,5-trimethyladamantane at normal and elevated pressures from which the transition entropies were also determined. By means of these values and the slopes of the T(p) transition curves transition volumes could be additionally calculated.