DECHEMA vapor—liquid equilibrium measurement

Worth noting is the fact that Barker s method does not require experimental j/f values. Thus the correlating parameters a, P, and so on, can be evaluated from a P-Xi data subset. Common practice now is, in fact, to measure just such data. They are, of course, not subject to a test for consistency by the Gibbs/Duhem equation. The world s store of VLE data has been compiled by Gmehhng et al. Vapor-Liquid Equilibrium Data Collection, Chemistry Data Series, vol. I, parts 1-8, DECHEMA, Frankfurt am Main, 1979-1990). 

Solvent activities of polymer solutions have been measured for about 60 years now. However, the database for polymer solutions is still modest, in comparison with the enormous amount of data available for mixtures of low-molecular substances. Three explicit databases have been published in the literature up to now. The database prepared by Wen Hao et al. is summarized in two parts of the DECHEMA Chemistry Data Series. Danner and Higtf provided a database and some calculation methods on a floppy disk with their book. WoUfarth prepared the most complete data collection regarding vapor-liquid equilibrium data of polymer solutions. His annually updated electronic database is not commercially available however, personal requests can be made via his e-mail address given above. 

Data Quality Normally, it is not possible to evaluate LLE data for thermodynamic consistency [Sorenson and Arlt, Liquid-Liquid Equilibrium Data Collection, Binary Systems, vol. V, pt. 1 (DECHEMA, 1979), p. 12]. The thermodynamic consistency test for VLE data involves calculating an independently measured variable from the others (usually the vapor composition from the temperature, pressure, and liquid composition) and comparing the measurement with the calculated value. Since LLE data are only very weakly affected by change in pressure, this method is not feasible for LLE. However, if the data were produced by equilibration and analysis of both phases, then at least the data can be checked to determine how well the material balance closes. This can be done by plotting the total... 

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