Abstract: A new sensitive colour reaction of Os(Ⅳ) with 8-amino quinoline has been studied.The complex has an absorption peak at 600 nm and the reagent exhibits maximum absorptivity in the ultraviolet region,so that they show a strong colour contrast.The apparent molar absorptivity was found to be 1.32×10⁵L/mol,cm.Beer's law is obeyed in the range of 0-10 μg of Os (Ⅳ)per l0 mL.It was also found that the complex reaction can be completed in 15-20 min,at 80-90℃ and pH 3.62 kept in a HAc-NaAc buffer solution,The colour of solution is stable at least 24 h.The molar ratio of Os(Ⅳ) to 8-amino quinoline was establislied to be 1:3 by two methods, All other noble metals except Ru(Ⅳ) which gives a slight absorption at 600 nm do not give colour reaction with 8-amino quinoline,even so 20 times amount of Ru(Ⅳ) can be tolerated.All common base metals reacting with 8-amino quinoline give no absorption at 600 nm,This paper is considered superior in terms of simplicity,stability,sensitivity and selectivity.

Key words: Amino quinoline, Osmium, Spectrophotometry