The spectrophotometric determination and solvent extrāction of osmium with o-(β-benzoylthiourido)benzoic acid as reagent

o-(β-Benzoylthiourido)benzoic acid is proposed as a spectrophotometric reagent for the determination of osmium. The brownish yellow complex formed is soluble in alcohol and in other organic solvents. The colour system obeys Beer's law from 3 to 18 p.p.m. of osmium at 410 mμ with an optimum range of 3–15 p.p.m., where the percent relative error per 1% absolute photometric error is 2.75%. A 1:1 complex is formed and the dissociation constant is of the order of 10^-5. With prior extraction of palladium as the axide complex with n-butanol, osmium can be separated from almost all ions, including those of platinum metals, by extraction witli ethyl acetate.