1. INTRODUCTION
Fats and oils are a mixture of triglycerids. Triglycerides are made up of three fatty acids linked
to glycerol by fatty acyl esters. Fatty acids are long chain hydrocarbons with carboxyl groups (COOH
groups). These fatty acids can be classified into saturated or unsaturated based on the number of double
bonds present in the fatty acid. Saturated fatty acids contain only single bond between the carbon atoms
and are tend to be solids at room temperature. Unsaturated fatty acids contain double bonds between the
carbon atom in addition to the single bonds present in the fatty acid chain. They are likely to exists as
liquids at room temperature. The double bonds present in the naturally occurring unsaturated fats are in
the Cis form. Trans fatty acids are associated with health problems and cardiovascular diseases.
Unsaturated fatty acids can be converted into saturated by the process of hydrogenation. Depending upon
the degree of unsaturation, the fatty acids can combine with oxygen or halogens to form saturated fatty
acids. So it is important to know the extend to which a fatty acid is unsaturated. There are different
methods for checking the unsaturation level in fatty acids, one among them is by determining the iodine
value of fats. Iodine value or number is the number of grams of iodine consumed by 100g of fat. A higher
iodine value indicates a higher degree of unsaturation.
unsaturated fatty acids
THEORY
Iodine value (IV) is a measure of the total number of double bonds present in fats and oils. It is expressed
as the number of grams of iodine that will react with the double bonds in 100 grams of fats or oils. The
determination is conducted by dissolving a weighed sample in a non-polar solvent such as cyclohexane,
then adding glacial acetic acid. The double bonds are reacted with an excess of a solution of iodine
monochloride in glacial acetic acid (“Wijs’ solution”). Mercuric ions are added to hasten the reaction.
After completion of the reaction, the excess iodine monochloride is decomposed to iodine by the addition
of aqueous potassium iodide solution, which is then titrated with standard sodium thiosulphate solution.

2. TITLE
Determination Of Iodine Number From Supplied Sample
MATERIALS
10% KI solution, 2gms NaHCO3, 6ml concentrated HCL, K2Cr2O7 solution, distilled water, iodine
solution, Na2S2O3 solution, olive oil, chloroform, starch solution, Hanus iodine reagent
APPARATUS
Retort stand, burette, conical flasks, reagent bottle, beakers
PROCEDURES
(A) Standardization of the supplied 0.1N Na2S2O3 solution
1) 30ml 10% KI, 2 grams NaHCO3 and dissolved with 6ml of concentrated hydrochloric acid.
2) The solution is slowly shake and then run in the flask. 10ml previously prepared standard K2Cr2O7
solution is added to the flask. The mouth of the flask is covered with a watch glass, shake and kept in the
dark for 5 minutes.
3) After 5minutes, the watch glass is removed and the inner side of the flask is washed with 50ml of
distilled water until the solution attains a yellowish green color. 1ml of starch solution is added.
4) Sodium thiosulphate is used for titration purpose until the greenish color changes to light green color
(end point) against a white background.
(B) Determination of iodine value of supplied oils
1) 2drop of oil(150mg) is taken and stored in a clean, dry 250ml glass stoppered reagent bottle.5ml of
chloroform added to the 2 bottles, 1 bottle with oil and the other without oil. The without oil containing
bottle will serve as a control. 15ml of Hanus iodine reagent is added to each bottle.
2) The solution is mixed well and placed in the dark for exactly 30minutes. After that, 7.5ml 10% KI
solution is added to each bottle and mixed it up. 37.5ml of distilled water is used to wash down the sides
of the containers.
3) The solution is titrate with previously standardized sodium thiosulphate solution until the solution
becomes light yellow. Then 0.5-1ml of 1% starch solution is added and the titration is consider completed
once the disappearance of blue color.

3. RESULT
Percentage error of burette: ±0.1ml
Table 1: Titration volume for standardize the supplied 0.1N sodium thiosulphate.
No. of
Observation
Initial Burette
Reading (ml)
Final Burette
Reading (ml)
Total volume of
Na2S2O3 used (ml)
Color
observation
Without starch 0.00 8.70
10.50
Yellowish-
green
With starch
8.70 10.30 Greenish blue
10.30 10.50 Light green
Table 2: Titration volume for sample supplied (sunflower oil)
No. of
Observation
Initial Burette
Reading (ml)
Final Burette
Reading (ml)
Total volume of
Na2S2O3 used (ml)
Colour
Observation
Without starch 0.00 7.70
8.00
Light yellow
With starch 7.70 8.00 colourless
Table 3: Titration volume for sample supplied (without sunflower oil)
No .of
Observation
Initial Burette
Reading (ml)
Final Burette
Reading (ml)
Total volume of
Na2S2O3 used (ml)
Colour
Observation
Without starch 9.00 18.40
10.50
Light yellow
With starch 18.40 19.50 colourless
Table 4: Titration volume for sample supplied (olive oil)
No. of
Observation
Initial Burette
Reading (ml)
Final Burette
Reading (ml)
Total volume of
Na2S2O3 used (ml)
Colour
Observation
Without starch 0.00 8.10
8.30
Light yellow
With starch 8.10 8.30 colourless

4. Table 5: Titration volume for sample supplied (without olive oil)
No .of
Observation
Initial Burette
Reading (ml)
Final Burette
Reading (ml)
Total volume of
Na2S2O3 used (ml)
Colour
Observation
Without starch 0.00 9.00
9.30
Light yellow
With starch 9.00 9.30 colourless
CALCULATION
To find the strength of Na2S2O3,
S1V1=S2V2
where, S1 = the strength of K2Cr2O7 (0.1N)
S2= the strength of Na2S2O3
V1= volume of oxalic acid
V2= the volume of Na2S2O3 (11.2ml)
S2=
= 0.09524N
Therefore, the strength of Na2S2O3 is 0.09524N.
Since 0.1N of Na2S2O3 solution/L contains 12.7g of Iodine,
0.09524N of Na2S2O3 solution/L =
= 12.10 grams of Iodine
(A)Determination of iodine value of supplied oils (sunflower oil)
Volume of 0.1 N Na2S2O3 solution used for blank = X ml
Volume of 0.1 N Na2S2O3 solution used for oil = Y ml
Iodine number = x
= x
= 10.08 / 0.1N of Na2S2O3

5. = 100.8 / 1.0N of Na2S2O3
Therefore, the Iodine number for sunflower oil is 100.8 / 1.0N of Na2S2O3.
(B)Determination of iodine value of supplied oils (olive oil)
Volume of 0.1 N Na2S2O3 solution used for blank = X ml
Volume of 0.1 N Na2S2O3 solution used for oil = Y ml
Iodine number = x
= x
= 11.31 / 0.1N of Na2S2O3
= 113.1 / 1.0N of Na2S2O3
Therefore, the Iodine number for olive oil is 113.1 / 1.0N of Na2S2O3.
DISCUSSION
The iodine value, or iodine adsorption value, is used in analytical chemistry to measure the
amount of unsaturation of oils and fats. Animal and vegetable oils and fats — known chemically as
triglycerides — have chains of carbon atoms that can bond with hydrogen. When the carbon atoms in
these chains are bonded to the maximum possible number of hydrogen atoms, the triglyceride is said to be
saturated, but when there are one or more double bonds between carbon atoms, there is less hydrogen in
the molecule, and the fat is said to be unsaturated. Triglycerides with one double bond are known as
monounsaturates and those with more than one double bond are known as polyunsaturates. Iodine can
combine with fats that have carbon double bonds and, therefore, the number of such bonds can be
deduced from the amount of iodine with which they will combine.
Fatty acids react with a halogen [ iodine] resulting in the addition of the halogen at the C=C double
bond site. In this reaction, iodine monochloride reacts with the unsaturated bonds to produce a di-
halogenated single bond, of whichone carbon has bound an atom of iodine.

6. After the reaction is complete, the amount of iodine that has reacted is determined by adding a solution of
potassium iodide to the reaction product.
ICl + KI ---------------> KCl + I2
This causes the remaining unreacted ICl to form molecular iodine. The liberated I2 is then titrated with a
standard solution of 0.1N sodium thiosulphate.
I2 + 2 Na2S2O3 -----------------> 2 NaI + Na2S2O4
In this experiment, the iodine number for olive oil is higher than the iodine number for sunflower oil. It
simply shows that olive oil contains more unsaturated triglycerides compare to sunflower oil.
Unsaturated fats, which include monounsaturated and polyunsaturated fats, have the reputation of being
healthier than saturated fats. The main health benefit of unsaturated fatty acid is its ability to help lower
cholesterol and triglyceride levels (triglycerides are the most common type of fat in our body and high
levels of it can be found in many people with high cholesterol levels and heart problems). As we all know,
a high cholesterol level means a high risk of heart disease, as well as stroke. Yet, this is only one benefit
that our body can enjoy from eating foods enriched in unsaturated fatty acids. Other benefits can include:
Giving the body energy. Fat can be broken down by the body and turned into energy.
Helping to reduce inflammation, especially in such conditions as arthritis.
Helping to reduce asthma type symptoms.
Helping to ensure proper development of the baby during one’s pregnancy.
CONCLUSION
The iodine value for olive oil and sunflower oil is 113.1 and 100.8 respectively. The degree of iodine
value indicates that the content of unsaturated triglyceride in certain fatty acid. Therefore, The
unsaturated triglyceride content in olive oil is higher than in sunflower oil, which also indicates that olive
oil is more healthy to consume compare to sunflower oil.
REFERENCES
1. Essential Biochemistry, 2004, Charlotte W. Pratt, Kathleen Cornely, John Wiley & Sons, Inc.
2. Introduction to General, Organic, and Biochemistry, 2007, Bettelheim, Thomson Higher Education
3. Pre-U Text STPM Biology, 2009, Lee Ching, Pearson Malaysia Sdn. Bhd.
4. http://www.wisegeek.com/what-is-an-iodine-value.htm
5. http://en.wikipedia.org/wiki/Iodine_value
6. http://www.3fatchicks.com/how-unsaturated-fatty-acid-benefits-our-body/