Iodine value of the given oil or fat

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BACKGROUND

Principle: Iodine value of an oil or fat is the number of grams of iodine, which is absorbed by 100 g of the substance (oil or fat) under described conditions. It can be determined by the following method.

Aim: To determine Iodine value of the sample (oil or fat)

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REQUIREMENTS

Chemical:        Carbon tetrachloride

Iodine monochloride

0.1 M sodium thiosulphate, 

Starch solution

Apparatus:     Volumetric flask

Pipette

Burette

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PROCEDURE

(Iodine Monochloride (ICl) Method or Wijs Method)

An accurately weighed quantity (w g) of the sample (oil or fat) is taken in a 500 ml iodine flask. 10 ml of carbon tetrachloride (CCl4) is added to dissolve it. 20 ml of iodine monochloride (ICl) solution is added. The mix solution is allowed to stand in the dark at a temperature between 15° – 25° C for 30 minutes, inserting the stopper. Then 15 ml of potassium iodide solution is added. The flask and the stopper are ringed with 100 ml of water, shaken and titrated with 0.1 M sodium thiosulphate solution using freshly prepared starch solution as indicator, which is added towards the end of the titration. The number of ml required is noted as (a). The procedure is repeated without the sample and the number of ml required is noted as (b). Iodine value is calculated from the observed data.

Observation

No. of

Observation

Initial Burette Reading (ml)

Final Burette Reading (ml)

Difference (ml)

Average (ml)

For Test

1

a =

2

For Blank

1

b =

2

Calculation

Iodine value = 1.269 (b – a)/w

Here, w = weight in grams of the sample.

[N.B.- The approx. weight in grams of the sample to be taken can be calculated by dividing 20 by the highest expected iodine value. If more than half of the halogen is absorbed, the test must be repeated with a lesser quantity of sample.]

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CONCLUSION

Iodine value of the given sample of oil/fat is …….

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REFERENCES

  1. Advanced Practical Organic Chemistry by O. P. Agarwal; Published by Krishna Prakashan Media (P) Ltd; Page No. 276. Indian Pharmacoepia 2010, Part I; Page No. 86.
  2. Practical Pharmacognosy by Saroja Joshi and Vidhu Aeri; Published by Frank Bros. & Co. (Publishers) Ltd.; First Edition: 2009: 296.
  3. Hand Book of Analysis and Quality Control for Fruit and Vegetable Products, second edition by S. Ranganna, Published by Tata McGraw -Hill Publishing Company limited, New Delhi, Page No.- 218.


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