Estimation of chromium in ores and beneficiated products: an ultrasonic approach

Cr(III) slowly forms a violet complex with EDTA at pH 3.5 +/- 0.2 under normal conditions. The complex formation can be catalyzed by irradiating the reacting mixture with ultrasonic waves. Quantitative formation of the complex was possible with ultrasonic waves of 15 W/cm(2) intensity within 7.5 min of sonication. This method may be successfully applied to the determination of chromium in ores and beneficiated products containing 20-60% Cr(2)O(3) without separating the analyte from the matrix elements.