Isothermal Joule–Thomson coefficient of nitrogen

Abstract

A flow calorimeter for the measurement of the isothermal Joule–Thomson coefficient of gases has been constructed for use at low temperatures and pressures up to 600 kN m^–2. A recirculatory flow system, which requires only a small quantity of gas, has been developed. The apparatus has been used to make new measurements of the isothermal Joule–Thomson coefficient of nitrogen from 298.15 to 78.37 K. Heat leaks in the flow calorimeter have been considered in detail and a method by which they may be analysed has been developed. The results are shown to be in good agreement with other work which satisfies a thermodynamic consistency test. Integration of the Joule–Thomson coefficient data yields new values of the second virial coefficient of nitrogen which are significantly different from existing data below 150 K.