The Extraction Spectrophotometric Determination of Cobalt with Violuric acid and Zephiramine

The extraction spectrophotometric determination of cobalt with violuric acid and zephiramine has been investigated. The cobalt-violuric acid-zephiramine complex can be extracted into chloroform. The complex extracted into organic layer has an absorption maximum at 372nm. An aqueous cobalt solution was transferred to a 100ml separation funnel, and 5ml of 4×(10)^<-3> M violuric acid was added. The pH was adjusted to between 7.5 and 8.5 with H_3BO_4-KCl-Na_2B_4O_7 buffer, and the volume was made up to 50ml with water. After 30 minutes, 3ml of 5×(10)^<-2> M zephiramine was added, and the solution was shaken for 3 minutes with 10ml of chloroform. The organic phase was dried over anhydorous Na_2SO_4,and the absorbance was measured at 372nm against reagent blank. Beer's law is obeyed up to 12μg cobalt per 10ml of chloroform. The moler absorptivity of the complex is 2.1×(10)^<-5> (cm)^<-1>・(mol)^<-1>・l at 372nm. The moler ratio of cobalt to violuric acid in the extracted species was estimated to be 1 : 3 by the continous variation method.