Construction of an Adiabatic Calorimeter Workable under Constant High-pressure

An adiabatic high-pressure calorimeter was constructed. The calorimeter cell was devised for minimization of the cell mass relative to the volume of the sample chamber. The pressure in the cell was controlled by joining the cell with a transmitting tube to a stabilized high-pressure system. The adiabatic conditions were achieved by temperature control of the transmitting tube as well as of adiabatic shields inside the cryostat. Procedures for the precise pressure control and for the determination of the molar volume and heat capacity with the correction for the mass transfer of pressure-transmitting liquid in a series of measurement were discussed. The apparatus is capable of measurement under constant pressure up to 110 MPa and over the temperature range from 100 to 370 K. The results on liquid 3-methylpentane which was used as the pressure medium proved satisfactory performance of this new-type calorimeter.