AN ADIABATIC LOW-TEMPERATURE CALORIMETER FOR HEAT-CAPACITY MEASUREMENT OF SMALL SAMPLES

A small sample adiabatic calorimeter for measuring heat capacities in the temperature range 60-350 K using the Nernst method has been constructed. The sample cell of the calorimeter is 6 cm(3) in the internal volume, equipped with a miniature platinum thermometer and surrounded by two adiabatic shields. Two sets of 6-junction chromel-copel thermocouples were mounted between the cell and the shields to indicate the temperature differences between them. The adiabatic conditions of the cell were automatically controlled by two sets of temperature controller. A mechanical pump was used to pump out the vapour of liquid nitrogen in the cryostat to solidify N-2 (1), and 60 K or even lower temperature was obtained. The performance of this apparatus was evaluated by heat capacity measurements on a-alumina. The deviations of experimental results from a smoothed curve lie within +/-0.2%, while the inaccuracy is within +/-0.5% compared with the recommended reference data in the wole temperature range.