The Gibbs-Duhem Relation

Consider

$$\input{equations/16-7A}$$ (24-15)

and compare it to our previous expression for $dG$:

It follows that (This is another important equation):

$$\input{equations/gibbs-duhem}$$ (24-16)

This is the Gibbs-Duhem Equation. It will be used again and again.

Notice that Equation 24-16 has the following form:

$$\input{equations/gibbs-duhem-form}$$ (24-17)

At equilibrium, a small virtual change in the system is normal to the size of the system.