# Chapter 13: The Phase Rule and Phase Diagrams

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$$\newcommand{\el}{\subs{el}} % electrical$$
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We encountered the Gibbs phase rule and phase diagrams in Chapter 8 in connection with single-substance systems.  The present chapter derives the full version of the Gibbs phase rule for multicomponent systems.  It then discusses phase diagrams for some representative types of multicomponent systems, and shows how they are related to the phase rule and to equilibrium concepts developed in Chapters 11 and 12.