Solubility Product of Tetravalent Plutonium Hydroxide and Study of the Amphoteric Character of Hexavalent Plutonium Hydroxide

Summary The solubility dependence of Pu(OH)4 as a function of the p n of diluted equilibrating perchloric acid solutions has been studied by covering a wide interval of ps- From the experimental solubility data obtained and some theoretical implications, an attempt has been made to conciliate the extrapolated, experimentally found thermodynamic solubility product with DEBYE-HÜCKELS theory on ionic effects to account for the variations observed of the apparent solubility product throughout the different experiments carried out. The study of the apparent solubility product as a function of the ionic force has evidenced the existence of important discontinuities, which have been tentatively referred to a number of hypothesis based on the variation of the ionic activities of the present species, and on the impurities characterized in the precipitate systematically used as the starting material throughout this work. Some other interesting features of Pu (OH)! connected with this investigation have been studied in detail. Since the analysis of the precipitate employed has evidenced the presence of some percent amounts of plutonyl hydroxide, a study of the amphoteric characteristics of this species could be undertaken simultaneously. The method used for the calculation of the instability constant of the amphoteric process involved has been described in detail. A single ion-exchange experiment has been carried out with the aim of getting some information on the state of plutonium in very diluted aqueous solutions.