Chemical equilibrium is not characterized by equilibrium constants alone. At least one conservation principle is necessary.
Textbook descriptions of plutonium chemistry that are based on two-reaction-product disproportionation equations, or do not
recognize the conservation principles, are incomplete and potentially misleading.
The percents of all oxidation states produced by Pu disproportionation, including unreacted starting material, can be obtained
by new equations that are easy to apply. The equations are useful for quantifying the extent and the stoichiometry of disproportionation,
the consequences of complexation, and the effects of temperature changes on the composition of the oxidation-state mixture.
Two predominance-region diagrams for plutonium are illustrated. One diagram plots the pH vs. the equilibrium fraction of hexavalent plutonium. The other diagram plots the equilibrium fraction of tetravalent plutonium vs. the plutonium oxidation number. Both diagrams define the boundaries of the regions where tri-, tetra-, penta-, and hexavalent plutonium are the predominant species. In each diagram, the two principal triple points are located at the intersections of three predominance-region boundary lines.
More than 99% of radioactive cobalt can be removed from water by precipitation as cobalt/III/ hydroxide. The process is continuous and uses either sodium hypochlorite or oxygen and calcium sulfite to oxidize the cobalt. Carbonate and phosphate interfere with cobalt removal, but the process has potential for other applications such as thallium removal and sewage treatment.
Balanced disproportionation equations indicate phenomena not predicted by the traditional, two-reaction-product equations. This communication illustrates unanticipated maxima in oxidation state distributions and suggests that they might be useful for characterizing alpha coefficients in aqueous solutions.
The equilibrium constant for the first hydrolysis reaction of tetravalent plutonium is surrounded by uncertainty. A new method
illustrates criteria by which the reliabilities of the numerical estimates can be judged. The new formulas are simple, the
method is easy to apply, and the results are easy to compare.
A method for quantitatively estimating the fractions of plutonium oxidation states that derive from disproportionation, or other oxidation-reduction reactions, is illustrated with data for seawater. The results agree with experiment and can be checked numerically. Attention is drawn to a discrepancy in what we think is known about seawater.
The numerical value of the first hydrolysis constant of tetravalent plutonium is uncertain by a factor of about ten. This
article illustrates the estimation of that constant by a least squares method applied to simultaneous equations involving
all of the Pu oxidation states.
The complexation of tetravalent plutonium in aqueous solutions derives from several sources including counterions, hydrolysis,
additives, and impurities. A quantitative tool accounting for all such effects, known and unknown, is the alpha coefficient.
It can be expressed in six ways by means of the equilibrium fractions of two Pu oxidation states.
An empirical method for preparing a plutonium predominance-region diagram is illustrated by an example. The method estimates
the boundaries of the forbidden, unique, and ambiguous regions as defined by the equilibrium fraction of hexavalent plutonium
and the plutonium oxidation number.