Abstract：The by-product (cadmium cluster) of zinc hydrometallurgy contains high contents of zinc, lead, copper and other impurities, which interferes with the determination of cadmium by titration method. The end-point jump is not obvious even if the direct titration is conducted after separating the impurities. For the back titration-displacement titration, the pH of solution after replacing cadmium with potassium iodide is hardly controlled. Moreover, the pre-separation of lead is required and the operation is complicated. In order to establish a method suitable for the determination of cadmium content in cadmium cluster, the sample was first decomposed with acid, and then the contents of zinc, lead and cadmium were determined by EDTA titration combined with atomic absorption spectrometry (AAS). In the hexamethylenetetramine buffer solution at pH 5.5-6.2, thiourea was added to mask the interference of Cu2+. Excessive EDTA standard solution was used to complex zinc, lead and cadmium. Back titration was performed with zinc standard solution using xylenol orange as the indicator. The results obtained were the total contents of zinc, lead and cadmium (in Zn). Then the contents of zinc and lead were determined by atomic absorption spectrometry (AAS). The content of cadmium could be obtained by subtraction. It was found that only large weight of sample could ensure the representativeness of samples for the analysis of chemical composition in cadmium cluster. The determination of zinc and lead by AAS was not interfered by the coexisting ions in system. The proposed method was applied for the determination of zinc, lead and cadmium in cadmium cluster. The relative standard deviations (RSD, n=11) were 0.69%-1.2%, 0.65%-1.6% and 0.11%-0.12%, respectively. The found results were consistent with those obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES) and back titration-displacement titration.
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