Standard thermodynamic quantities of transfer

This section is devoted to a detailed elaboration of thermodynamic quantities employed in the literature to deal with dilute solutions. These are the so-called standard free energies, entropies, enthalpies, etc. associated with the transfer of a solute from one phase to another. There are actually many quantities which are referred to as standard quantities. We deal essentially with one of these, the one which is most directly amenable to a molecular interpretation. 

Because of our ultimate intention to interpret experimental quantities, we shall be concerned with systems at constant temperature and pressure, which are the most prevalent in experimental work in this field. 

The general expressions for the chemical potential and the pseudochemical potential in the T, F, N ensemble have been developed in Sections 3.5 and 3.6. The analogous relations in the T, P, N ensemble are derived in Appendix 9-F. Here, we summarize the basic quantities that will be required. The chemical potential and the pseudo-chemical potential of a component A are defined in the T, P, Nj, ensemble by 

the added A molecule is assumed to be placed at a fixed position Rq. For nonspherical molecules, we may require also that the orientation be fixed. Here we deal, for simplicity, with spherical molecules only. 

The basic statistical mechanical expressions for the chemical potential are 

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In a similar fashion, one can derive other standard thermodynamic quantities of transfer for processes I and II. The expressions for process II will always be simpler than the corresponding expressions for process I. 

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