Molecular systems equilibrium between subsystems

Next we consider the problems of identifying the equilibrium state for two interacting phases of the same molecular species but in different states c-f aggregation, and of determining the requirements for the stability of this state. An e.xample of this is a vapor and a liquid in equilibrium. To be general, we again consider a composite system isolated from its environment, except that here the boundary between the two subsystems is the real interface between the phases. For this system, we have... 

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