Procedure

Procedure

  • Weigh about 0.1 – 0.5g fat into a 250ml glass stoppered bottle.
  • Add 10ml of chloroform to dissolve the sample and 25ml of Hanus iodine solution.
  • Mix well and allow standing for 30 min. in dark with occasional shaking.
  • At the end of this period, add 10ml of 15% potassium iodide solution.
  • Shake vigorously and then wash down the sides of the bottle and the stopper with 100ml of distilled water.
  • Titrate against 0.025N sodium thiosulphate, adding it with constant shaking until the yellow colour almost disappears.
  • Add 1ml of starch solution which acts as an indicator and continue the titration with thiosulphate when the blue colour almost disappears.
  • Stopper the bottle and shake vigorously so that any iodine remaining in the chloroform layer will pass into potassium iodide solution.
  • Complete the titration, run a blank test without the sample.
Last modified: Monday, 14 November 2011, 5:27 AM