CRITICAL TRANSITIONS OF TERNARY MIXTURES - A WINDOW ON THE PHASE-BEHAVIOR OF MULTICOMPONENT FLUIDS

The critical properties of the carbon dioxide+ethylene+helium ternary mixture are calculated and compared with experimental data. The purpose of the analysis is to illustrate how the calculation of ternary critical transitions can provide an insight into the general fluid phase behavior of multicomponent mixtures. Previous calculations had indicated that ternary mixtures exhibit some critical transitions which have no direct parallel in binary-mixture phase equilibria. Apart from the possibility of a tricritical point, the occurrence of a critical transition between different two-phase regions is likely to be common in ternary mixtures containing, at least, two binary subsystems of limited miscibility. The calculations are in qualitative agreement with available experimental data and they confirm the existence of a ''double critical point.''