Analytical Method: Chromium (total) in tannery effluents

Instruments and Reagents:

Cat.No. 173016  Spectroquant® VIS Spectrophotometer Prove 100 or

Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or

Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600 or

Cat.No. 109748  Spectroquant® Photometer NOVA 30 or

Cat.No. 109751  Spectroquant® Photometer NOVA 60 or

Cat.No. 173632  Spectroquant® Colorimeter Move 100

Cat.No. 114946  Rectangular cells 10 mm and/or

Cat.No. 114947  Rectangular cells 20 mm and/or

Cat.No. 114944  Rectangular cells 50 mm
Cat.No. 114552  Spectroquant® Chromium Cell Test
Cat.No. 114758  Spectroquant® Chromium Test
Cat.No. 100731  Sulfuric acid 96 % for analysis
Cat.No. 107209  Hydrogen peroxide 30 % (Perhydrol®) for analysis
Cat.No. 105092  Potassium peroxodisulfate for analysis
Cat.No. 116754  Water  for analysis
Sample preparation:
In a 250-ml glass beaker place 10 ml of homogenised water sample and evaporate to dryness on a heating plate. Add 5 ml of 96 % sulphuric acid and evaporate superfluous water. Treat the blackish - brown residue with 5 ml of Perhydrol® (Caution, very slow addition!) and evaporate slowly and carefully until superfluous Perhydrol® has been removed. The solution tends to produce a strong foam, which, in the course of the process, decolorises. If the solution becomes brown or black, allow to cool, add further 10 ml Perhydrol® and repeat heating process. Repeat the whole process until a clear colorless solution is obtained. Heat until all superfluous Perhydrol® has been evaporated and allow to cool to room temperature. Add 25 ml water for analysis and approx. 5 mg Potassium peroxodisulfate to the now color less residue. Heat the mixture and keep it 5 minutes at the boiling point. Because of the oxidation of the chromate the solution change the color to yellow during boiling. Transfer to a 100-ml volumetric flask. Fill up to the mark with water and mix well.
Determine with the above mentioned test kits.
Chromium (total) concentration in mg/l Cr = analysis result in mg/l Cr x 10


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