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A new procedure to measure high-pressure vapor-liquid equilibria Is proposed, In which both vapor-and liquid-phase samples are withdrawn without disturbing the equilibrium conditions. Vapor-liquid equilibrium data are reported for pressures approaching the critical pressures for the nitrogen-carbon dioxide system at 273.2, 293.2, and 298.2 K, and for the methane-Freon 22 (chlorodifluoromethane) system and the methane-Freon 12 (dlchtorodlfluoromethane) system both at 283.2, 273.2, and 298.2 K. Critical pressures and compositions at several temperatures were determined by means of a graphical method.

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Thermal conductivltles of pure gases (Ar, N,, O,, CO,, CH,, C2H4) have been measured at temperatures from 25 to 50 OC and pressures up to 150 bar by using a vertical coaxial cylindrical cell on a relative basis. The apparatus was calibrated with Ar, O,, CH, , and C02 as standard gases. The uncertainty of the thermal conductivii obtained is estimated to be within 3%. Experimental results for pure gases were compared with the values of other investigators and the maximum deviation was 6 % . Predictive values determined by the Stiel-Thodos equation were in good agreement with the experimental results. IntroductionThe thermal conductivity of fluids is an essential basic property in the design of processing equipment involving heat transfer. Thodos (1966, 1965) measured the thermal conductivity of CH, and N2 gases and Michels

A coaxial cylindrical cell was constructed for measuring thermal conductivities of nine pure fluids (argon, nitrogen, oxygen, helium, carbon dioxide, methane, ethane, ethylene and propane) at temperatures ranging from 25 to 76°C under pressures up to 17.5MPa. Thermal conductivities of two binary mixtures (argon-nitrogen and methane-ethylene) were also measured at 30.6, 50.6 and 76.6°C under pressures up to 9.8 MPa. The apparatus was calibrated with eight kinds of gases. The Stiel-Thodos and Crooks-Daubert correlations were applied to predict the effect of pressure on the thermal conductivity of pure fluids. They were also extended to the mixtures by use of the van der Waals one-fluid model. Fairly good agreement was obtained with the experimental data as well as those from the literature except in the vicinity of the critical region.