Permanganate‐Azide Test for Total Chromium in Water

Abstract

chromium and a diphenylcarbazide reagent, resulting in a characteristic reddish-violet color, following Beer's Law. This reaction does not occur with trivalent or bivalent chromium. To facilitate the determination of the total chromium which may be present in a water, it has been found feasible to oxidize the polyvalent chromium ions to the hexavalent state. Once this has been accomplished, the chromium is measured colorimetrically or photometrically by utilizing the diphenylcarbazide color reaction. The original standard method for total chromium (1) utilized perchloric acid for the oxidation operation. The shortcomings of this procedure were evidenced by its lack of precision. It was also a difficult method to use on waters containing significant quantities of organic material. In the attempt to find a more reliable test for total chromium, comparative studies of new procedures were conducted by the Nassau County Division of Laboratories and Research, Hempstead, N.Y., the US Public Health Service, and the New York State Health Department Laboratories (2). The results of these studies led to the inclusion of the alkaline bromate and the permanganate oxidation procedures in the current issue of Standard Methods (3). The Nassau County Division of Laboratories and Research has found the latter procedure the more desirable. It circumvents the undesirable effect of organic or reducing materials which may be present in the water under examination.