Balance of Entropy - The Onsager Reciprocal Relations

This case corresponds to a two-phase vapor-liquid state. From conditions F(0) 0 and F(l) 0 it follows that a necessary condition of biphasic state is 

This case corresponds to a one-phase saturated state (condensation point). From condition F(l) = 0 there follows the necessary condition of existence of mixture in a saturated gas state 

Note that criteria 1 and 5 are not physically realizable, therefore they may be considered only as the auxiliary criteria helpful in numerical solutions of appropriate problems. 

we have the following system of 2N + 2 equations for 2N + 2 unknowns 

---