Photometric techniques have been developed to determine strontium(II) and uranium(VI), barium(II) and uranium(VI) in aqueous solutions where these elements are present together at concentration levels of 10-5–10-4 mol/l. The techniques are based on the difference in optimum conditions for forming the complexes of uranium(VI) and ions of alkaline-earth elements with arsenazo III, as well as absorbance additivity of colored solutions. To eliminate the influence of arsenic(V) and phosphorus(V), it has been proposed to eliminate them preliminary from the solutions by sorption on the anion exchanger in the Cl–-form. The results obtained using the developed techniques have been checked for correctness by the «entered – found» technique and confirmed by the additive method. The techniques were used to determine the solubility of mineral-like compounds MII (BVUO6)2•nH2O (M – Sr, Ba; BV – As, P). The composition and formation constants of uranium(VI), strontium(II) and barium(II) with arsenazo III complexes have been found.
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