Excess property relations among

Since the residual properties and excess properties are merely two particular members of the general class of differences defined in (6.2.1), we might expect that the functional forms for relations among excess properties bear similarities to the forms for relations among residual properties. Indeed, many such similarities exist, and in fact the similarities extend beyond functional relations to encompass the entire strategy used in relating conceptuals to experimentally accessible quantities. 

Similar connections can be made for properties of mixing, excess properties, and activity coefficients. The use of this approach on fluctuation properties is described by Perry and O Connell (1984). The relations for TCFI among pairs of species are extremely complex with the extents of reactions embedded in the TCFI. However, those for DCFI are much more direct and the extents of reaction are contained in the projectors. Defining the desired matrix. 

The theorem of correspondii states can therefore be applied to the mixture as well as to pure compounds, when the average molecular parameters of the mixture are known. A simple graphical discussion of the excess properties is then possible (cf. 4). One can read the values of the excess functions directly from a diagram representing the reduced properties of pure compounds as functioJ3s of reduced temperature and pressure. This is the most remarkable feature of the theory, if one keeps in mind the complex relationship among the excess functions themselves and between excess functions and intermolecular forces. In the present treatment the behaviour of the excess functions is directly related to the behaviom of pure components which may be either obtained experimentally or deduced from some statistical model. 

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