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 VE against x has a rather symmetric curve at low pressures, becoming less so at high pressures. The changes in the excess functions GE, HE and TSE with increasing pressure have been calculated; GE is less affected by pressure than HE or TSE, 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.