Horsley (1973) gives an extensive collection of data on azeotropes.Īctivity coefficients at infinite dilution The values of the activity coefficients determined at the azeotropic composition can be used to calculate the coefficients in the Wilson equation (or any other of the three-suffix equations) and the equation used to estimate the activity coefficients at other compositions. Where P °i is determined at the azeotropic temperature. At the azeotropic point the composition of the liquid and vapour are the same, so from equation: If a binary system forms an azeotrope, the activity coefficients can be calculated from a knowledge of the composition of the azeotrope and the azeotropic temperature. Some of the techniques most useful in design are given in the following paragraphs.Įstimation of activity coefficients from azeotropic data The same confidence cannot be placed on the prediction of equilibrium data as that for many of the prediction techniques for other physical properties given in this chapter. Caution must be used in the application of these techniques in design and the predictions should be supported with experimentally determined values whenever practicable. Some techniques are available for the prediction of vapour liquid equilibria (v l e) data and for the extrapolation of experimental values. The designer will often be confronted with the problem of how to proceed with the design of a separation process without adequate experimentally determined equilibrium data.
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