Determination of Chromium content in leather (SOPs)


CHROMIC OXIDE Leather (SOPs)

CHROMIUM OXIDE CONTENT BY WET OXIDATION METHOD



APPARATUS

  • Desiccator.
  • Erlenmeyer flask – 300 ml capacity
  • Conical flask – with stopper
  • Heating element.


REAGENTS

PROCEDURE
  • Sample the leather specimen to grounded form in leather mill machine.
  • Weigh about 1 g of grounded test specimen and transfer it to 300 ml Erlenmeyer flask or Kjeldahl flask.
  • Add 10 ml of concentrated nitric acid to the sample.
  • Then add 8 ml sulfuric acid followed by 25 ml of Perchloric acid, cover the flask and heat to boiling on a low flame for about 45 minutes.
  • As soon as, mixture turns to orange, lower the flame and heat slowly for 2 minutes.
  • Then cool in air and finally rapidly in cold water by diluting the contents to about 200 ml.
  • Again boil for 10 to 15 minutes using earthenware pebbles, to avoid bumping.
  • Again cool and add 15 ml phosphoric acid followed by 20 ml of potassium iodide solution.
  • Leave the solution in dark for 15 minutes.
  • After 15 minutes, take the solution and add 5 ml of starch indicator.
  • Titrate the solution with standard sodium thiosulphate solution to light green.




CALCULATION:-


Chromium (as Cr2O3), percent by weight =    2.534 *V*N / W
                 Where,


REFERENCE: - IS 582:1970 (LC 10) - methods of chemical testing of leather.










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