Pressure of Pure Substances

Critical Pressure of Pure Substances.— The critical pressure may be determined in several ways. As already indicated, the critical pressure may be determined directly from p,V isotherms but this method is not particularly accurate because of the difficulty in establishing the critical isotherm. 

Kudchadker et al. have pointed out that experimental methods which enable visual observation of the critical temperature, the determination of the critical density by the law of rectilinear diameters (see below), and subsequently the direct determination of the corresponding critical pressure, should be preferred over other methods. 

The most commonly used techniques involve measurement of vapour pressure up to the critical temperature. The sample is confined over mercury in a tube sealed at the upper end. The mercury can be pressurized using a dead-weight pressure tester and the pressure on the sample varied at will. The critical pressure can either be obtained by measuring the vapour pressure as a function of temperature up to a kelvin or so below the critical point and extrapolating to the critical temperature, or by measurement of the pressure at which the meniscus 

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Boublik, T., V. Fried, and E. Hala "The Vapor Pressure of Pure Substances," Elsevier, Amsterdam, 1973. 

B. D. Smith and R. Srivastava, Thermodynamic Data for Pure Compounds Part A.. Hydrocarbons and Ketones, Elsevier, Amsterdam, the Netherlands, 1986. T. Boubhk, V. Eried, and E. Hala, The Hapour Pressures of Pure Substances, 2nd ed., Elsevier, Amsterdam, the Netherlands, 1984. 

Boubik, T., Fried, V. and Hala, E. (1984) The Vapour Pressures of Pure Substances, 2nd edn (Elsevier). 

Boublik, T., Fried, V., Hala, E. (1984) The Vapor Pressure of Pure Substances, 2nd revised Edition, Elsevier, Amsterdam, The Netherlands. Bowman, B. T., Sans, W. W. (1983) Determination of octanol-water partitioning coefficient (KqW) of 61 organophosphorus and carbamate insecticides and their relationship to respective water solubility (S) values. J. Environ. Sci. Health B18, 667-683. Bradley, R. S., Cleasby, T. G. (1953) The vapour pressure and lattice energy of some aromatic ring compounds. J. Chem. Soc. 1953, 1690-1692. 

Stull, D.R. (1947) Vapor pressure of pure substances organic compounds. Ind. Eng. Chem. 39(4), 517-560. 

A. N. Nesmayanov, Vapour Pressure of the Chemical Elements. Amsterdam, New York Elsevier, 1963 T. Boublik, F. Vojtech and H. Eduard, The Vapor Pressure of Pure Substances. Amsterdam, New York Elsevier Scientific, 1973. 

Boublik T, Fried V, Hala E. 1984. The vapor pressures of pure substances Selected values of the temperature dependence of the vapor pressures of some pure substances in the normal and low-pressure region. Volume 17. Amsterdam, Netherlands Elsevier Scientific Publications. 

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