The enthalpy of mixing of argon + nitrogen at 123, 130, and 140 K at pressures up to 10.1 MPa

Abstract

The enthalpy of mixing of argon + nitrogen at 123, 130, and 140 K has been measured using a flow-calorimetric apparatus. The pressure dependence of the enthalpy of mixing has been investigated over the range 1.73 to 10.1 MPa. The measurements progress from the gas phase, through the two-phase and supercritical-fluid regions, and into the liquid region, as the pressure is increased. The results at 140 K are close to the critical point, and show great sensitivity to the pressure. Comparison is made with the Redlich-Kwong equation of state using parameters chosen to fit a previous determination of the excess enthalpy of the liquid mixture at 84.5 K. Agreement with measurements in the gaseous and two-phase regions and in the liquid region up to 123 K is satisfactory. Only qualitative agreement with the measurements at 130 and 140 K is found.