This project is an experimental study of the phase equilibria behavior of selected CO;i2 + hydrocarbon binary and ternary mixtures, which can contribute to the understanding of the phase equilibria behavior of CO;i2 - enhanced oil recovery systems. Vapor-liquid, liquid-liquid-vapor, and solid-liquid-vapor phase equilibria of the homologous series of binary mixtures of CO;i2 + n-alkybenzenes are studied. Also, the liquid-liquid-vapor phase equilibria of the ternary mixture CO;i2 + n-nonadecane + propane are studied in order to assess how the presence of a light hydrocarbon species extends the three-phase region of a prototype CO;i2 + hydrocarbon system in thermodynamic phase space. The studies are performed in the temperature range of -60;so to 125;soC at pressures up to 2000 psia.