Combined Potentiometric Determinations of Manganese, Chromium, and Vanadium in Steels

Abstract

The steel is dissolved in “Spekker Acid.” Manganese, chromium, and vanadium are oxidized to Mn⁷⁺, Cr⁶⁺, and V⁵⁺, respectively, by ammonium persulphate in the presence of silver nitrate. Manganese is titrated with sodium nitrite, the equivalence point being indicated at 890 mv. Chromium and vanadium are then titrated together with ferrous ammonium sulphate, the end point occurring at 500 mv. Vanadium is selectively re-oxidized at room temperature by potassium permanganate, and the excess is destroyed with sodium nitrite. The vanadium is then titrated with ferrous ammonium sulfate to the end point at 500 mv, as before.

The method is rapid and accurate. It has the advantage that all three determinations are performed on the one solution.

Published with the permission of the Director, Mines Branch, Department of Mines and Technical Surveys, Ottawa, Canada. Her Majesty the Queen, in Right of Canada, reserves the right to reprint this article.