Thermodynamic properties of liquid mixtures of krypton + methane

Abstract

The equations of state of liquid methane and of a mixture of composition 0.475 Kr + 0.525 CH₄ have been measured at 129.32, 134.32, 142.68 and 147.08 K, from just above the saturation vapour pressure to the freezing pressure of krypton. Similar studies have been made at 142.68 K for two other mixtures with mole fraction of krypton x= 0.645 and 0.339.

The results show that the excess volume is small and negative at low pressures and increases slightly with pressure, becoming almost zero at high pressures. A plot of V^E against x has a rather symmetric curve at low pressures, becoming less so at high pressures. The changes in the excess functions G^E, H^E and TS^E with increasing pressure have been calculated; G^E is less affected by pressure than H^E or TS^E, a feature common to other simple liquid mixtures.

Neither the conformal solution theory (in the van-der-Waals–one-fluid form) nor a perturbed hard-sphere equation could account for the quantitative behaviour of the system.