Thermodynamic properties of the system argon-methane liquid

Summary

Vapor pressure and volume changes on mixing of the system argon-methane have been measured at 86.74 °K (triple point of trifluoro-chloromethane) by a technique essentially similar to that used for the carbon monoxide-methane system (Trans. Far. Soc.,52, 1488 (1956)). Heats of mixing and volume changes on mixing have been directly measured at slightly above 90.7 °K by the technique described by Jeener (Rev. Sci. Instr.,28, 263 (1957)). Excess properties have been worked out taking account for non-ideality of both liquid and vapor phases and compared to the prediction of the average potential theory developed by Prigogine and coworkers (seeThe Molecular Theory of Solutions, (Amsterdam 1957)) Table I gives

the main results. There is qualitative agreement between column 3 and 4 (right sign of the excess functions) though the theoretical expressions appear 2 to 3 times larger than the experimental ones. This is presumably to be ascribed to the relatively large value of ϱ=r ^*₂₂ )/r ₁₁ (about 12%) whose influence appears to be overestimated in the average potential theory.