2.1 Phase Transitions in Thermodynamic Systems (continued)

Figure 2.1. Free energy of mixing of a binary liquid, its chemical potential, and the corresponding phase diagram: T₂ > T_crit and T₁ < T_crit.

A distinction must be made between the equilibrium criterion and the stability criterion, which specifies when a homogeneous phase is stable against decomposition into heterogeneous phases in the unstable region. According to Gibbs, the following conditions apply to a binary system:

Original footnote: J. Willard Gibbs (1839–1903), physicist.