Phase equilibria in the system Ne-Xe at high pressures: I. Gas-gas equilibrium and the critical line up to 20 kbar

Abstract

The phase behaviour of the system neon-xenon has been studied in a diamond anvil cell at pressures up to 20kbar. By visual observation of the mixtures, the phase transition of the homogeneous gas phase to fluid-fluid equilibrium has been detected as a function of pressure and temperature, with an overall composition ranging from 14% to 53% xenon. The measurements reveal that the critical line of neon-xenon moves continuously from the critical double point of the system to higher pressures and higher temperatures. Asymptotic behaviour of the critical line or the existence of a second critical double point cannot be observed because the measurements of the gas-gas equilibrium are restricted by the appearance of the melting surface of the mixture. A strong shift of the critical concentration as a function of pressure and temperature was observed from 36% xenon at 3 kbar and 7°C to 26% at 18 kbar and 142°C.