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The densities of liquid argon, krypton xenon, oxygen, nitrogen, carbon monoxide methane, and carbon tetrafluoride along the orthobaric liquid curve

1969; Elsevier BV; Volume: 1; Issue: 4 Linguagem: Inglês

10.1016/0021-9614(69)90072-x

1096-3626

M.J. Terry, John T. Lynch, M. Bunclark, K.R. Mansell, L. A. K. Staveley,

Advanced Thermodynamics and Statistical Mechanics

The densities along the orthobaric liquid curve of the following liquefied gases have been measured with a precision of a few parts in 104: argon (86 to 118 K); krypton (118 to 164 K); xenon (164 to 219 K); oxygen (80 to 121 K); nitrogen (78 to 105 K); carbon monoxide (78 to 111 K); methane (92 to 151 K); carbon tetrafluoride (91 to 185 K). The measurements were made on a sample of about 9 cm3 in a glass pyknometer, which was incorporated in a cryostat assembly similar to that used in conventional lowtemperature adiabatic calorimetry. The results have been considered from the point of view of the law of corresponding states. When the volume is plotted as a fraction of the critical volume Vc against temperature expressed as a fraction of the critical temperature Tc, the results for liquid krypton, xenon, and nitrogen conform to a common curve. By changing the “best” values of Vc for argon and oxygen by about 0.5 per cent (which is probably within the uncertainty limits of these values of Vc), the points for these two liquids could also be made to fall on the same curve. But there are indications of small divergences from this curve for methane and carbon monoxide, even if the values of Vc adopted for these two substances are altered. Over the temperature ranges studied, the so-called rectilinear diameter for all eight substances examined is in fact a very slight curve, but extrapolation to the critical temperature of a least-squares straight line gives values of the critical volume within about one per cent of the literature values.