Analysis of Brass Plating Solution Using EDTA

Complex salt of cupper and zinc cyanide is decomposed into CuO and ZnO, by H2O2, and then dissolved by HNO3. The total amount of Cu and Zn can be determined by titrating the solution with EDTA with PAN (α-Pyridyl-β-azonaphtol) as indicator. Zn can be titrated directly by EDTA in the presence of Cu which is masked by the addition of slight excess of thiosulfate at pH 5-6, using the PAN indicator and methanol. The amount of Cu in the mixture can be calculated by the difference of the above two.