Isothermal Diffusion of Uncharged Molecules in a Two-Component System

13 5 ISOTHERMAL DIFFUSION OF UNCHARGED MOLECULES IN A TWO-COMPONENT SYSTEM 

In an isothermal isobaric system in which no chemical reactions can occur, no free charges are present, and upon which no external forces act, Eq. (13.3.10) reduces to 

This shows that not all the gradients of the chemical potentials are independent. It is convenient to consider the component present in excess as solvent (labeled co) and to express its chemical potential gradient V/cm in terms of the chemical potential gradients of the remaining components (solutes). Then 

Combining this with Eq. (13.5.1) gives the entropy production 

Thus for an n component solution there are n — 1 independent forces V(—m) corresponding to the fluxes 

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