Argon liquid-vapor equilibria

Liquid-Vapor Equilibrium Data for tbe Argon-Nitrogen-... 

During the course of an experimental study of the liquid-vapor equilibria of the nitrogen-oxygen-argon system ], it was found desirable to develop a rapid and accurate method for the analysis of equilibrium samples. After consideration of a number of possible analytical methods, such as chemical reactions for nitrogen and oxygen P or mass spectrometry [ ], gas chromatography was selected as the most likely to provide an acceptable technique. 

The detector medium is argon, kept at cryogenic conditions and vapor-liquid equilibrium at 87 K and 1265 mbar. A detector network and appropriate instrumentation to measure neutrino interactions with argon atoms will be immersed in the argon liquid inside the tank. A ventilation system (pressurizer) and a cavern heating system will work in parallel to maintain the conditions in the tank cavern at 22°C and 1250 mbar. 

Argon at liquid-nitrogen temperature exhibits an equilibrium pressure of 187 torrs. It offers the advantage of a lower vapor pressure than nitrogen, which will reduce the void volume error while retaining ease of pressure measurements. However, the cross-sectional area of argon is not well established and appears to vary according to the surface on which it is adsorbed. 

The equilibrium state between the solid, liquid, and vapor phase of argon (triple point of argon) at Tss = 83.798 (tea = 189.352°C) may be used as an alternative to the condensation point of oxygen. 

L. Israel, C. J. Sterner, and G. M. Wilson, Argon-Oxygen-Nitrogen Three-Component System Experimental Vapor-Liquid Equilibrium Data, Quarterly Progress Report I, Contract No. AF 33(657)-8742 (Oct. 1962). 

Vapor-Liquid Equilibrium Studies on the System Argon-Oxygen (3) 294... 

Vapor-Liquid Equilibrium Studies on the System Argon-Oxygen (3) 294 Measuring Vapor-Liquid Ratios during Flow by a Capacitance Method (5) 505... 

Figure 6.1.16 Content of ammonia vapor in equilibrium with liquid ammonia in a 3 1 H2/N2 mixture [effect of methane and argon not counted data from Jennings and Ward (1989)].

For nonideal vapor and liquid mixtures, the equilibrium constants must be determined experimentally. Since such equilibrium constants are a function of both temperature and pressure, any tabulation must include these two parameters. Table 6.2 provides equilibrium constants for nitrogen, oxygen, and argon for three pressures and a useful range of temperatures. 

Estimate the equilibrium vapor and liquid compositions for a mixture of oxygen and argon at a pressure and temperature of 0.101 MPa and 87 K, respectively, assuming that the vapor acts as an ideal gas and the liquid behaves as a perfect solution. 

The bottom product from the lower column of a double-column air separation unit consists of 40% nitrogen, 59% oxygen, and 1% argon on a molar basis. Determine the saturated temperature of liquid when the pressure in the column is 0.405 MPa. What is the composition of the vapor that is in equilibrium with this saturated reboiler liquid ... 

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