Abstract
A simple and rapid method for analysing chromium plating solutions with a single sampling is presented. Chromium (VI) oxide, chromium (III) and impurities (iron, copper and nickel) are determined by spectrophotometric methods. The procedure involves a nearly complete separation of ions of the metals from chromium (VI) by precipitation of the hydroxides. The amount of chromium (VI) in filtrate is measured at 445nm after acidifying the solution with sulfuric acid. The precipitates of the hydroxides are dissolved in dilute hydrochloric acid, and chromium (III) is measured at 375nm after oxidizing with hydrogen peroxide in an alkaline medium of sodium hydroxide. Iron, copper and nickel in the hydrochloric solution are determined colorimetrically by the 1, 10-phenanthrolin method, the cuprizon method and the dimethylglioxime method, respectively. Direct determination of iron and copper are found to be possible by the 1, 10-phenanthrolin method and the cuprizon method in the presence of a large quantity of chromium (VI). Five samples taken from chromium plating solutions for industrial use were analyzed by conventional methods, (the titrimetric method for chromium trioxide and trivalent chromium and the atomic absorption method for iron, copper and nickel) and compared with the results obtained by the present method.
