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An adiabatic calorimeter has been constructed for the study of properties of condensed substances in the temperature range 2° to 300°K. Two resistance thermometers were used, one of platinum for T>11°K and one of carbon for T20°K but decreasing to ±0.5% at the highest temperatures. In conjunction with these measurements, vapour pressures were measured in the temperature range 66° to 86°K. The heat of fusion was found to be 284.5±0.4 cal mole-1, the triple point temperature 83.810°K and the triple point pressure 516.86±0.02 mm Hg. The amount of impurity in the specimen of argon was estimated to be 3 parts per million from a study of the melting range. Direct measurement of the heat of vaporization of the liquid gave the result 1563.6±4.6 cal mole -1 at 85.67°K, which corresponds to 1555.0±4.6 cal mole-1 at the normal boiling point.
Flubacher et al. (Fri,) studied this question.