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It is found experimentally that the absorbance of a mixture of the europium-XylenolOrange (XO) and zinc - XO complexes in slightly acidic media is equal to the sum of the individualabsorbances measured alone, within ±2%. When a mixture of rare earths (instead of europium) ismeasured together with zinc, the maximum deviation for additivity is within ca. ±3%. On the basisof this additivity of absorbances, a procedure can he devised to determine europium and zinc togetherspectrophotometrically with XO, and then europium alone after extraction of zinc(Ⅱ) with triocty-lamine / xylene. The interference of aluminium, and copper(Ⅱ) may be avoided by masking withsulphosalicylic acid and thiourea respectively.
It is found experimentally that the absorbance of a mixture of the europium-XylenolOrange (XO) and zinc - XO complexes in slightly acidic media is equal to the sum of the individualabsorbances measured alone, within ± 2%. When a mixture of rare earths instead of europium) ismeasured together with zinc, the maximum deviation for additivity is within ca. ± 3%. On the basis of this additivity of absorbances, a procedure can be scheduled to determine europium and zinc togetherspectrophotometrically with XO, and then europium alone after extraction of zinc (Ⅱ) with triocty-lamine / xylene. The interference of aluminum, and copper (Ⅱ) may be avoided by masking with sulfulosalicylic acid and thiourea respectively.