Three extractions with 0.02 M thenoylrecovery of 50% of the hafnium with zirconium trifluoroacetone of a solution containing 5.0% content of 0.4%. zirconium, based on the hafnium content, gave a
III) in sulfuric acid rapidly and nearly completely to plutonium(IV).2At high concentrations of hydrogen peroxide plutonium(IV) is precipitated. This precipitate has been the subject of extensive investiga-tion3•4•6•6'7 and is known to contain, in addition to peroxide, anions such as Cl-, N03-, C104-and S04=, depending on the anions present in solution.The Peroxy Complexes of Plutonium(IV).-Addition of a small amount of hydrogen peroxide to a light brown solution of plutonium (IV) produces a deep brown color, the color changing within the time of stirring. On adding more
The data of Kasha and Sheline on rates aiid equilibria of the disproportionation reaction of plutoniuin(1V) to give plutonium(II1) and plutonium(V1) have been corrected for the reduction caused by the plutonium a-particles. I t was necessary to assume reaction paths for the a-particle-induced reduction, and one-electron reductions of Pu(V1) and Pu( IV) were chosen as most plausible. The disproportionation mechanism was found to be consistent with that previously deduced from the disproportionation of plutonium( V). The equilibrium for the disproportionation of plutonium(1V) exhibited approximately the expected fourth power dependence on hydrogen ion concentration in perchloric acid at unit ionic strength and 25'. An apparent fifth.power dependence was obtained for hydrochloric acid solutions, not at constant ionic strength. The disproportionaton rate showed an inverse third power acid dependence in perchloric acid a t constant ionic strength and an apparent-3.5 power dependence in hydrochloric acid solutions, without added salt. Approximate values of 40 kcal. and f 6 0 e x . were calculated for the heat and entropy of activation of the disproportionation reaction in onemolar hydrochloric acid. The formal potentials of the Pu(II1)-Pu(V1) and Pu(1V)-Pu(V1) couples in one molar perchloric acid a t 25" are -1.043 2~ 0.003 and -1.022 =t 0.002 volt, respectively. Thc corresponding values for one molar hydrochloric acid are -1.053 * 0.003 and -1.025 rt 0.002 volt. The discrepancy concerning chloride complexing of PuOz++ is nearly eliminated by the new values for the disproportionation equilibrium quotient. It is pointed out that the assumption of a small amount of complexing of P u f a by chloride ion would give complete agreement and evidence is advanced in support of this hypothesis.htroduction.-Attention1** has been called to a discrepancy between the observed properties of plutonium(V1) with chloride ion and that calculated from e.m.f. and disproportionation equilibrium measurements. Spectral observations show plutonyl ion, PuOz++, to be appreciably complexed in one molar hydrochloric acid.3 The e.m.f. and equilibrium results indicate the unlikely result that plutonyl ion is more strongly complexed by perchlorate than by chloride ion..The source of the discrepancy has been traced to an error in the equilibrium quotient for the reaction The average oxidation number of plutonium in a solution containing these species slowly decreases with time. The a-particles, from the disintegration of plutonium, in their passage through the solution produce species which bring about the red~c t i o n .~ When the rate of reduction by the CYparticle radiation becomes of the same order of magnitude as the rate of attainment of the disproportionation equilibrium of equation (l), then true equilibrium will not be established. The results of the calculations of this paper show that this correction is much more important than was previously suspected and that the apparent equilibrium quotients were seriously in error.Extensive measurement...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.