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Pure Appl. Chem. 76(1), 11-17, 2004

Pure and Applied Chemistry

Vol. 76, Issue 1

Are isotopic mixtures ideal?

G. Jancs�

KFKI Atomic Energy Research Institute, H-1525 Budapest 114, P.O.Box 49, Hungary

Abstract:

Isotopic mixtures have long been considered as textbook examples of ideal solutions. High-precision vapor pressure measurements have shown that even these very simple mixtures exhibit deviations from the ideal behavior. The small, but still significant nonideality of isotopic mixtures can be accounted for in terms of the difference in the molar volumes of isotopic molecules. Theoretical analysis demonstrates that the internal vibrations of the molecules significantly contribute to the excess Gibbs energy, and the proper consideration of the volume dependence of molecular vibrations of the component molecules is essential to the understanding of the properties of isotopic mixtures.

*Lecture presented at the European Molecular Liquids Group (EMLG) Annual Meeting on the Physical Chemistry of Liquids: Novel Approaches to the Structure, Dynamics of Liquids: Experiments, Theories, and Simulation,Rhodes, Greece, 7-15 September 2002. Other presentations are published in this issue, pp. 1-261.


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