Abstract：The chromogenic reaction between the reagent Dibromomethyl carboxyazo and cobalt was studied. In ammonium citrate-ammonia solution at pH 10.2, cobalt reacted with Dibromomethyl carboxyazo, forming a blue complex which exhibited an absorption maximum at 660 nm with an apparent molar absorptivity of 1.77×104 L·mol-1·cm-1.Beers law was obeyed in the range of 0-3.2 mg/L for cobalt.The proposed method has been applied to determine cobalt in copper-cobalt alloy with RSD(n=5) smaller than 2%.The results were consistent with those obtained by nitroso-R salt spectrophotometry.
