Gas-liquid and fluid-fluid phase separation in the system helium + argon at high pressures

Abstract

Equilibrium phase compositions for the system helium + argon are reported at seven temperatures in the range 91.34–147.73°K, and at pressures up to 680 atm. The data are concentrated in the region 144–148°K, and include two points on the critical mixture curve. This curve passes through a minimum in temperature at 147.1°K at a pressure of 442 atm, and a region of fluid-fluid phase separation is to exist at higher pressures and temperatures. The nature of the critical curve in relation to those of other binary systems containing helium is discussed.