| Résumé : |
1. Scope : The procedure described is suitable for the determination of chromium(VI) in natural waters, in solutions leached from leather or in waste waters, in concentrations of 0.5-4 mg/litre. The chromium(VI) must be in solution and this is generally the case. The presence of barium, lead and silver ions may lead to the precipitation of chromates ; in such cases the chromium(VI) present would be underestimated..
2. Principle : The procedure involves the photometric determination of chromium(VI) after reactionwith 1,5-diphenylcarbazide. It is based on German standard DIN 38406-E-10-3.
Chromium(VI) oxidises 1,5-diphenylcarbazide to 1,5-diphenylcarbazone which gives rise to a red/violet complex with chromium. the degree of spectral adsorption (i.e. extinctionp of this dye shows a linear relationship to the chromium(VI) concentration and is measured at 550 nm.
Chromium(III) and other metals are precipitated from a phosphate-buffred solution by the addition of aluminium sulphate prior to the chromium(VI) determination. Valency change of chromium due to oxidising or reducing substances is avoided through the addition of sulphites in the neutral sample followed by oxidation with hypochlorite. |
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Accueil
Photometric determination of chromium (VI) using 1,5-diphenylcarbazide in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 72 (Année 1988)
