Spectrophotometric determination of molybdenum(vi) with benzoylacetanilide

The complex formed between molybdenum(VI) and benzoylacetanilide in the pH range 0.6 and 1.9 has been extracted into methyl isobutyl ketone and the absorbance has been measured at 410 mμ. Quantities of 0.15 to 2.10 mg of molybdenum have been determined with a standard deviation of 0.6%. The color is stable up to 2 hours. The presence of Co 2+ , Ni 2+ , Zn 2+ , Mn 2+ , Be 2+ , Al 3+ , Cr 3+ , Ce 4+ , Th 4+ or UO 2+ 2 up to 100 μg causes no interference. Ordinarily, Fe 3+ interferes with the determination, but when masked with 1 ml of 0.5% solution of ascorbic acid the tolerance limit is 10 mg. Thus, molybdenum can be determined in steel when present in amounts as low as 0.26%.