Adiabatic calorimeter for the purpose of calorimetry in the solid, liquid and supercooled phases of metals

Abstract

An adiabatic calorimeter has been developed for the purpose of calorimetry in the solid, liquid and supercooled phases of metals in vacuum or inert gas atmospheres. Heat capacity was measured with heat supplied by an external drive system, in which the power output of a DC stabilised power source is interlocked with the rotation of a motor. For measurement of the specimen temperature, a chromel-constantan thermocouple was used, and heat was supplied uniformly by a constantan heater wound around a crucible. The temperature of the adiabatic system was programmed PID controlled, and stability was maintained within +or-0.009 K min-1 in the region of 300-700 K even when supplying heat to the specimens. Using a crucible made of fused quartz, pure bismuth was supercooled to 30 K; the enthalpy of fusion was measured as 11478 J mol-1, and the entropy of fusion as 21.077 J mol-1 K-1. The measured values of both the enthalpy and entropy of fusion, and the values of the heat capacity in the solid and the liquid phases all showed good agreement with values in the literature, and it was shown that stable measurement of heat capacity in the solid, liquid and supercooled phases using the same specimen and apparatus is possible.