Cover practical saponification value and acid value with calculation and diagram

1. TOPIC: To Determination of Acid value &
Saponification value
Miss: Puja R. Basule
M-Pharm in Pharmaceutical Chemistry
B-Pharm 2nd Year 3rd Semester
Practical of Organic Chemistry-II

2. Ex.no.3: Determination of Acid value in oils and fats
• Acid Value
Synonym: Neutralization number, Acid number
Definition: The number of milligram of potassium hydroxide
(KOH) required to completely neutralize free fatty acid 1gm of
fat or oil.
Apparatus: Beaker, Conical flask, Burette,
pipette, Burette stand etc.
Chemicals: 0.1N Oxalic acid, KOH solution,
Phenolphthalein indicator, fat or oil sample.

3. • Principle: The acid value is determined by directly titrating
the oil & fat in an alcoholic medium against standard
potassium hydroxide or sodium hydroxide solution.

4. Procedure:
1) Standardize normality of Potassium hydroxide solution,
KOH
 10 ml of 0.1N oxalic acid is poured into conical flask 2-3
drops of phenolphthalein indicator is added to the solution
 The solution is titrated with 0.1N KOH solution till a
permanent pink colour appears.

5. 2) Determination of acid value of Fats and Oils
 Weight accurately 5g of a sample (oil or fat) transfer into a
conical flask
 Add 25ml of 95% ethanol
 Mix the mixture very well
 Add few drop of phenolphthalein indicator and titrated with
0.1N KOH solution.
Calculations
Where,
V=Volume in ml of standard KOH
N= Normality of the KOH
W= Weight in gm of the sample

6. Result: The acid value of a given sample (oil or fat) was
found to be 0.69mg/g

7. Significance
• The value is measure of the amount of free fatty acids which
have been liberated by hydrolysis from glycerides due to the
action of moisture & temperature.
• Therefore, oils with increased acid number are unsafe for
human consumption.
• Indicates the degree of rancidity of a fat.

8. What is Saponification?

9. Ex.no.5: To determine the saponification value of oil
or fats
• Definition: The no. of milligram of KOH required to Saponify
one gram of a fat or oil.
• Saponification no. is measure of the average molecular weight
of the fatty acids present.
Sample Saponification value
Soya bean oil 180-200
Cotton seed oil 180-200
Coconut oil 250
Butter fat 230-250

10. • Apparatus: Conical flask, 100ml beaker, Dropper, Reflux
condenser, water bath, Pipette (25ml), Burette.
• Chemicals: Ethanolic KOH (95% ethanol v/v), Potassium
hydroxide [0.5N], Hydrochloric acid [0.5N], Phenolphthalein
indicator.
• Principle: The saponification value of an oil or fat is
determined by refluxing an accurately weight amount of an oil
or fat with an excess of alcoholic KOH solution and then
titrating the unused KOH against a standard solution of an acid
phenolphthalein as indicator.

11. Procedure:
 Standardization of 0.5N KOH solution
 Pipette 20ml of 0.1M hydrochloric acid into flask
 Dilute with 50ml of water and add 0.1 ml of phenolphthalein
solution
 Titrate with the ethanolic potassium hydroxide solution until a
permanent pale pink colour is produced.
 Determination of Saponification
 Accurately weight 1gm of sample (fat or oil)
 Transfer into a round bottom flask
 Add 25ml of 0.5N KOH solution and attached to a reflux
condenser.
 Set another reflux condenser as blank with everything present
except the fat.

12.  Heat both flasks on a boiling water bath for 30min
 Leave to cool to room temperature and titrate with 0.5M HCL
and use phenolphthalein as indicator
 Until the pink color disappears
 Record your reading as (T)ml for test (B) ml for blank

13. Calculation: Burette Reading
Blank 45mL
Test sample 34mL

14. Significances:
• Saponification value also indicated the length of carbon chain
of the acid present in that particular oil or fat.
• The magnitude of saponification value gives an idea about the
average molecular weight of the fat or oil.
• Higher the molecular weight of the fat, the smaller is its
saponification value.
• Higher the saponification value, greater is the percentage of
the short chain acids present in the glycerides of the oil or fats.