Upon performing colorimetric determination of chromium with diphenyl-carbazide (DPC), the following were found. The color development proceeded not only in dilute sulphuric acid solution, but also in solutions of HNO
3, HCl, HClO
4 and CH
3COOH or in mixed solutions of these acids. Wide concentration ranges (about 0.01-0.5N) of these single acids allowed perfect development of the Cr
6+ coloration with DPC. Mixed solutions of 0.1-1% of these acids also resulted in perfect color development. HC1O
4 proved to be the most excellent oxidant of Cr
3+ to Cr
6+ for the reaction with DPC compared with Mn0
2 and Pb0
2. The mixed acid (HC10
4+H
2SO
4) was more suitable than single HC1O4 for this oxidation.
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