Spectrophotometric Studies on Organometallic Complexes Used in Analytical Chemistry. VI : Spectrophotometric Determination of Uranium with Quercetinsulfonic Acid

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Quercetinsulfonic acid is soluble in water, and its neutral solution forms a brown colored water-soluble complex with uranyl ion. Therefore, the fundamental conditions for the determination of uranium with this complex were investigated. Uranyl-querce-tinsulfonic acid complex shows a comparatively wide absorption band with a maximum absorption at around 460 mμ. The complex, when colored at pH 6.0〜7.5, gives a definite 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 6.0〜6.5 in the case of quantitative determination. The reagent with concentration above 2.4×10^<-4> mol/1 gives a definite absorbancy. Therefore, the determination can be carried out well by adjusting the reagent to 4.8×10^<-4> mol/1 and at pH 6.0〜6.5. The calibration curve was prepared by using 1〜12.5γ/ml at 460〜490 mμ; it followed Beer's law well and its molar 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 on the development of coloration. When a large amount of thorium is present, uranium is separated by extracting with TBP from 7N HCl solution before the color is developed.
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