Thursday, October 29, 2009

Estimation of Iodine Value of an oil using Hanus solution


AIM:
To determine the iodine value of a given sample of oil.
PRINCIPLE:
Iodine value is a measure of the degree of unsaturation of an oil.It is defined as the number of parts by mass of iodine absorbed by 100 parts by mass of an oil or fat.
REAGENTS:
Hanus solution( iodine monobromide), freshly prepared starch solution, carbon tetrachloride,10% solution of potassium iodide, standard sodium thiosulphate solution N/10
APPARATUS:
Iodine flasks, burette, measuring cylinder
PROCEDURE:


  • About 0.2 g of oil is weighed out into a clean dry iodine flask of 500ml capacity.

  • It is then dissolved in about 10ml of carbon tetrachloride.

  • 25ml of hanus solution is added to it from a burette.

  • The flask is gently rotated to mix the contents thoroughly.

  • The tip of the flask is moistened with potassium iodide.

  • The flask is kept in the dark for half an hour.

  • Then 20ml of 10% potassium iodide solution are added & the mixture diluted by adding 200ml of water.

  • The mixture is then titrated with standard thiosulphate solution using starch as indicator.

  • A blank is also determined.

4 comments:

  1. hi Asha
    pls tel me the preparation of hanus solution.and is the procedure remains same if we use wij's solution??
    sakshi

    ReplyDelete
  2. Hi Sakshi
    Hanus solution is iodine monobromide & wij's solution is iodine monochloride. Preparation of hanus solution is a lengthier one & it should be done only in the presence of your concerned teacher as well as an attender.
    Care should be taken while handling bromine. I will post the preparation of hanus solution in my blog.
    Wij's solution was used by me in the determination of iodine value of lauric acid. I think you can buy this reagent from outside & depending on the concentration you have to dilute it.

    Regards
    Asha

    ReplyDelete
  3. hi asha,
    I performed iodine value test by preparing hanus solution in my lab. But when next time I prepared the solution; the results were not comparable with the previous results.
    What could be the reason for this.

    ReplyDelete
    Replies
    1. Hello,
      Have you used same oil for testing Iodine value? I mean coconut oil or palm oil? If the same oil was used, then the reason lies in the preparation of hanus solution.

      Regards
      Asha

      Delete