# Potentials in Pourbaix Diagrams

by Silvius
Tags: diagrams, potentials, pourbaix
 P: 13 I see, thank you very much, Borek! How does this relate to the idea that the potential at which a horizontal line divides two oxidation states of an element is equal to the potential of the reduction half equation which relates those two species? (For example where we had Fe$^{3+}$ (aq) and Fe$^{2+}$ (aq) divided by a horizontal line with the former on the top).
Yes but why do the potentials in this case represent the potentials for the reduction of Fe$^{3+}$ to Fe$^{2+}$ when there is other stuff which might be contributing to the "solution" potential? Is it simply because under these conditions, those two species are the dominant species?