Abstract
Quercetinsulfonic acid is soluble in water, and its neutral solution forms a brown colored watersoluble complex with uranium ion. Therefore, the fundamental conditions for the determination of uranium by this method have been investigated. Uranyl-quercetinsulfonate complex shows comparatively wide absorption band with a maximum absorption at around 460 mμ. The complex when colored at pH 6.07.5, gives a difinite absorbancy; however, the absorption by the reagent itself is rapidly increased with pH above 6.5. For this reason, it is necessary to adjust the solution to pH 6.06.5 in the case of quantitative determination. The reagent with concentration above 2.4×10-4 mol/l gives a definite absorbancy. Therefore, the determination can be carried out well by adjusting the reagent to 4.8×10-4 mol/l and pH to 6.06.5. The calibration curve was prepared by using 112.5 γ/ml at 460490mμ; it followed Beer's law well and its molecular extinction coefficient was 17, 600. Good results were obtained for quantitative determination after removing coexisting elements with TBP. When thorium is present in an amount about the same as that of uranium, about 0.005% EDTA should be added at the development of coloration. Or, when a large amount of thorium is present, is separated by extracting it with TBP from 7N HCl solution before the color is developed.
