Book excerpt: Plutonium literature does not satisfactorily include the four common oxidation states of plutonium in discussions of the stoichiometry of the disproportionation of the tetravalent and pentavalent states of this element. A theoretical study of possible consequences of including all common oxidation states of plutonium in the disproportionation reactions was made. The study, based upon available potential and free energy data, indicates that the disproportionation equations can be written with all four species included. The potential behavior of disproportionated plutonium solutions can be predicted with the aid of these new equations. The equations also predict that the hydrogen ion dependence of plutonium disproportionation reactions should not be exactly fourth power at all acidities.