An isolated system has two phases, denoted by $\mathrm{A}$ and B, each of which consists of the same two substances, denoted by 1 and $2 .$ Show that necessary conditions for equilibrium are
1. the temperature of each phase is the same, $T_{\mathrm{A}}=T_{\mathrm{B}}$.
2. the pressure of each phase is the same, $p_{\mathrm{A}}=p_{\mathrm{B}}$.
3. the chemical potential of each component has the same value in each phase, $\mu_{1}^{\mathrm{A}}=\mu_{1}^{\mathrm{B}}, \mu_{2}^{\mathrm{A}}=\mu_{2}^{\mathrm{B}}$.