Photometric determination of total chromium using diphenyl carbazide

5 Photometric determination of total chromium using diphenyl carbazide General remarks 

In mineral acid solution, hexavalent chromium compounds form with diphenyl carbazide an intensely red-purple coloured complex with an absorption maximum at 540 nm ( = 34,200). The measurement is performed in the aqueous phase. The complex forms instantaneously and is stable in sulphuric acid solution. The colour intensity of the solution is proportional to the concentration of chromate ions in the water sample. Trivalent chromium compounds are oxidized to chromate before complex formation and as such are also included in the measurement. 

A) The method is suitable for determining total chromium in water in concentrations of approx. 0.01 mg/1 and over. 

To prevent chromium losses the water sample should be stored in polyethylene containers. Pyrex or normal glass is not suitable. Interference due to self-coloration of the sample can be eliminated by measuring the extinction after a determination run without the addition of diphenyl carbazide. 

Cuvettes path length 1, 2 and 3 cm Separating funnel, 200 ml Measuring flasks, 100 ml and 1 litre Bulb pipettes, 2, 5, 10 and 100 ml Phosphoric acid  

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