A graph showing how standard electrode potentials vary with oxidation state for different oxidation states of an element. Frost diagrams can be constructed from Latimer diagrams. For an element M, the standard electrode potential E⦵ is calculated for the reaction.
where M(N) indicates the species in oxidation state N and M(0) indicates the zero oxidation state. The Frost diagram is then obtained by plotting NE⦵ against N for the different species. NE⦵ is proportional to the standard Gibbs free energy of the particular half reaction.
In a Frost diagram, the lowest point corresponds to the most stable oxidation state of the element. Also, the slope of a line between two points is the standard potential of the couple represented by the points. Like Latimer diagrams, Frost diagrams depend on pH. The Frost diagram was introduced by Arthur A. Frost (1909–2002) in 1951.