An Automatic Adiabatic Calorimeter for Low Temperatures. The Heat Capacity of Standard Benzoic Acid

Abstract

An adiabatic calorimeter for the measurements of the heat capacity of a solid and liquid over the temperature range from 13 to 300°K has been constructed. In order to minimize the operating manpower, all the temperature controls were recorded semiautomatically. The energy input was started and stopped automatically by a timer driven by a signal from a transistor clock. The working platinum resistance thermometer was calibrated against a laboratory standard thermometer which had been calibrated by the National Bureau of Standards. In order to verify the performance and the accuracy of this one-man-operated calorimeter, the heat capacity of a Calorimetry Conference Standard sample of benzoic acid crystal has been measured from 15 to 310°K. The results have compared with the data from the NBS and from other laboratories; this comparison served to establish the reliability of this equipment. The estimated errors are ±2% at 20°K, ±1% below 50°K, and ±0.3% above 50°K.