 Mixing can be intuitively explained by the following example, first used by Gibbs in introducing the concept of mixing. Begin with a glass of water, then add a shot of scotch; this is illustrated in Fig. 4a. The volume \(C\) of the cocktail (scotch + water) is \(\mu(C)\) and the volume of scotch that was added to the water is \(\mu(S)\), so that in \(C\)the concentration of scotch is \(\mu(S)/\mu(C)\).