Spectrophotometric determination of osmium with quinisatin oxime

A spectrophotometric determination of osmium has been developed, based on the purple color (absorption maximum at 515 mμ) formed by reaction of osmium with quinisatin oxime in buffered solution of dimethyl formamide and methanol. The absorbances are reproducible, and the system conforms to Beer's law. The method compares favorably in sensitivity with existing methods for osmium. The optimum concentration range (for 1 cm optical path) is about 2 to 10 p.p.m. of osmium. Although the maximum color develops slowly, it is stable for 7 days or longer. Several elements, notably iron, cobalt, and ruthenium, interfere, so that separation, is necessary. A reaction ratio of 1:2 for osmium and quinisatin oxime was clearly indicated; some evidence was also obtained for the presence of higher complexes.