Abstract: The study of spectrophotometric determination of traces of osmium with 1,5-diphenylcar-bazide in the presence of non-ionic surfactant OP-10 at pH3.5 HAc-NaAc buffer solution is given in this paper. The effects of other noble metals and base metals were investigated. The non-ionic sufac-tant OP-10 phlys an important role in increasing sensitivity and stability. The molar ratio of osmium to the reagent is 1 : 1. The calibration graph for measurement at 570 nm is linear in the range of 0.1 -5.0 mg of osmium per 10 mL, with a molar absorptivity of 3. 50×10⁵ L · mol^-1 · cm^-1. The relative standard deviation is smaller than 4.0%.

Key words: 1,5-Diphenylcarbazide, Osmium (Ⅳ), Non-ionic sulfactant, Spectrophotometric method