4.4 Pourbaix diagrams.
Plot electrochemical stability for different redox states of an element as a function of pH. As noted above, these diagrams are essentially phase diagrams that plot the map the conditions of potential and pH (most typically in aqueous solutions) where different redox species are stable. We saw a simple example of such a diagram in section 4.5 for H2O. Typically, the water redox reactions are plotted as dotted lines on these more complicated diagrams for other elements.