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Gas-liquid equilibrium compesitions for the O2-CO2 system were determined for the -49.4°C isotherm over the complete pressure range from the vapor pressure of CO2 at -49.4°C, 6.92 atm abs, to the maximum pressure of the system, 142.4 atm abs. Activity coefficients are calculated, and a thermodynamic consistency test is applied.The gas-liquid equilibrium of the O2-CO2 system at low temperatures has been studied in detail previously (2, 4> ¿0-Partly to verify and partly to complete the previous work(2) where the high-pressure range of the isotherm is missing, a series of gas-and liquid-phase equilibrium compositions were determined at -49.4°C for pressure up to the maximum, 142.4 atm abs. Activity coefficients based on the unsymmetric nor-1 To whom correspondence should be addressed. malization are calculated, and a thermodynamic consistency test is performed. EXPERIMENTALThe apparatus used here is of the vapor-recirculation type and is discussed in detail elsewhere (1). The central unit of the vapor-recirculation apparatus is the cell containing a sta-

A Dvorak-Boublik equilibrium recirculation apparatus has been used to measure isothermal vapor-liquid equilibrium (VLE) data for 10 different binary systems: diisopropyl ether + 2-methoxyethanol, trichloroethylene + 2-methoxyethanol, 1,2-epoxybutane + n-hexane, 1,2-epoxyhexane + n-heptane, 1,2-epoxybutane + n-heptane, 1,2-epoxybutane + 1-hexene, 1,2-epoxybutane + 1-octene, 1,2-epoxybutane + 1-chlorobutane, 1,2-epoxybutane + 2-chlorobutane, and epichlorohydrin (l-chloro-2,3-epoxypropane) + 2-chlorobutane. For each system except the last one, two isothermal sets of VLE data at pressures ranging from 7 to 102 kPa have been measured. Computer programs, using a numerical routine based on the maximum likelihood principle, have been used to test the data for thermodynamic consistency and to calculate group interaction parameters (formerly not available) for the UNIFAC model.