Abstract: A distillation method is used for the separation of Ru as RuO_4 after oxidation of all Ru species from liquid waste. NaBiO_3 is used as oxidizing agent in H_2SO_4-H_3PO_4 solution, RuO_4 is absorbed in a mixed hydrochloric acid-alcohol medium and reduced in the +3 valent state. The colour reaction of Ru (Ⅲ) salts with 1, 4-diphenyl-thiosemizide is investigated. Maximum colour development can be obtained using 6 mol/1 HCl-alcohol solution, heating for 30 min at 85℃. A red-violet stable Ru complex with maximum absorbance at 560 nm is obtained for determinating the Ru concent. The sample contains about 8 μg of Ru, the error of the method used is better than 4％.