NANOCOLOR® Chromate Photometric determination of chromate Photometric determination with diphenylcarbazide. In acidic medium, chromate ions react with diphenylcarbazide to form a red-violet colour complex. Chromium(III) ions are not determined unless they are converted to Cr(VI) by silver-catalysed oxidation with ammonium peroxodisulphate/ sulphuric acid. Read More »