Synthesis and properties of uranium compounds: pt.1

A guanidinium salt of [U(PW11O39)2]sup(10-), the solubility of which is adequate for crystal growing, has been synthesized. Using this salt or potassium salt, we have measured the stability of [U(PW11O39)2]sup(10-) as a function of pH of the solution and found that the anion is stable for the pH range 3-7. We have developed a colorimetric method for determining the concentration of U4+. In this method PW11O39sup(7-) is added to U4+ in such a quantity that the mole ratio PWsub(11)Osub(39)sup(7-)/Usup(4+) exceeds 2 and the intensity of the 22.7 kK band (epsilon 1030 M-1cm-1) is measured. In order to develop a continuous method to recover uranium, we have determined the amount of recovered PWsub(11)Osub(39)sup(7-) after decomposing [U(PW11O39)2]sup(10-) by adding either a base or an oxidizing agent. The percentage of PWsub(11)Osub(39)sup(7-) recovered was approximately 70% when a base was used and approximately 80% when K2S2O8 was used. A colorimetric method for determining PW11O39sup(7-) has also been developed. (Author)