This document describes the procedure for determining the iodine value of oils and fats. The iodine value is the number of grams of iodine absorbed by 100g of an oil or fat when treated with Wijs solution. It provides a measure of the degree of unsaturation in fatty acids, with higher values indicating more double bonds and unsaturated fatty acids. The procedure involves treating the oil sample with excess iodine monochloride, then titrating the excess iodine with sodium thiosulfate and calculating the iodine value based on the titration results.

1. DETERMINATION OF
IODINE VALUE
PRESENTED BY
HARISH PUDI
M PHARM, 2nd SEM
DEPT OF PHARMA ANALYSIS,
PES COLLEGE OF PHARMACY.

2. CONTENTS
 DEFINITION
 IMPORTANCE
 PRINCIPLE
 METHODS
 PROCEDURE
 CALCULATION

3. IODINE VALUE
The iodine value of an oil/fat is the number of grams of iodine absorbed by
100g of the oil/fat, when determined by using Wijs solution.
Analytical importance
 The most important application of the iodine value is to determine the amount of
unsaturation contained in fatty acids.
 Iodine number is directly proportional to content of unsaturated fatty acids, and it
is used to analyze the degree of adulteration.
 This unsaturation is in the form of double bonds which react
with iodine compounds.
 The higher the iodine value, the more unsaturated fatty acid bonds are present in
a fat.

4. Principle:
The oil/fat sample taken in carbon-tetrachloride is treated with a known
excess of iodine monochloride solution in glacial acetic (Wijs solution). The
excess of iodine monochloride is treated with potassium iodide and the
liberated iodine estimated by titration with sodium thiosulfate solution.

5. Methods for the determination of iodine value
 Huebl's iodine
 Wijs iodine value
 Iodine by H. P. Kaufmann
Huebl's iodine
Introduced the iodine value was Hübl which titrated fats in the presence of
mercuric chloride with iodine, but with the actual reagent (probably iodine
chloride) is formed in situ from mercuric chloride and iodine. Pure iodine
accumulates concerned not to alkenes, which is why the still valid definition
of iodine is only a formal one.
Wijs iodine value
Addition of iodine chloride and back-titration with sodium thiosulphate

6. Iodine by H. P. Kaufmann
(Bromination of the double bonds in the dark, reducing the excess bromine
with iodide, back titration of iodine with thiosulfate)
The fat is mixed with an excess of bromine. This bromine is added to the double
bonds in the unsaturated fats. This reaction must be carried out in the dark, since
the formation of bromine radicals is suppressed by light. This would lead to
undesirable side reactions, and thus falsifying a result consumption of bromine.

7. Procedure: Expected Iodine Weight to be take for Value estimation (g)

8. Weigh accurately an appropriate quantity of the dry oil/fat. into a 500 ml conical
flask with glass stopper, to which 25 ml of carbon tetrachloride have been added.
.
Mix the content well. Add 50 to 60 percent of Wij’s solution over that actually
needed.
Pipette 25 ml of Wij's solution and replace the glass stopper after wetting with
potassium iodine solution.
Swirl for proper mixing and keep the flasks in dark for half an hour for non-drying
and semi-drying oils and one hour for drying oils.
Carry out a blank simultaneously. After standing, add 15 ml of potassium iodide
solution, followed by 100 ml of recently boiled and cooled water, rinsing in the
stopper also.
PROCEDURE

9. Titrate liberated iodine with standardized sodium thiosulphate solution, using starch
as indicator at the end until the blue colour formed disappears after thorough shaking
with the stopper on.
Conduct blank determinations in the same manner as test sample but without oil/fat.
Slight variations in temperature appreciably affect titre of iodine solution as
chloroform has a high coefficient of expansion.
It is thus necessary that blanks and determinations are made at the same time.

10. Calculation:
Iodine value = 12.69 (B – S) N
W
Where,
B = volume in ml of standard sodium thiosulphate solution required for the
blank.
S = volume in ml of standard sodium thiosulphate solution required for the
sample.
N = normality of the standard sodium thiosulphate solution.
W = weight in g of the sample.

11. THANK YOU