Conditions of equilibrium for heterogenous systems with various restrictions

If the envelope is adiabatic, then Equation (5.7) must be written as 

If the envelope is rigid, then we find the pressure of each phase within a group must be the same, but the pressures of the two groups are independent and need not be equal. 

When the envelope is permeable to a component, then the chemical potential of the component must be the same in each phase in which it exists. If the envelope is not permeable to a component, then for each group, the chemical potential of that component must be the same in each phase in which it exists. However, the chemical potential of that component need not be the same in the groups. These conditions apply to species as well as to components. 

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