BACKGROUND
Principle: Saponification value is defined as the number of milligrams of KOH required to completely hydrolyse (saponify) one gram of the oil/fat. In practice a known amount of the oil or fat is refluxed with excess amount of standard alcoholic potash solution and the unused alkali is titrated against a standard acid.1
Aim: To determine saponification value of the given oil/fat.
Reaction:
REQUIREMENTS
Sample: Oil or fat
Apparatus: Conical flask
Reflux and condenser
Water bath
Burette and Pipette
Chemical: 0.5 N HCl
phenolphthalein
0.5 N alcoholic potassium-hydroxide solution
PROCEDURE
About 2 g of the given oil or fat is taken in a conical flask but weighed accurately (w g). The oil/fat is dissolved in 25 ml of 0.5 N alcoholic potassium-hydroxide solution. Then the reaction mixture is refluxed using a water condenser on a water-bath for half an hour. The resulting solution is cooled and titrated against a 0.5 N HCl solution adding 1 ml of phenolphthalein. The number of ml of acid required is noted (a). An exactly identical blank experiment (leaving the fat or oil) is performed. Number of ml of hydrochloric acid required is noted (b).
Observation
Samples No. | Initial Burette Reading (ml) | Final Burette Reading (ml) | Difference (ml) | Average (ml) | |
For Excess KOH remaining | 1 | a = | |||
2 | |||||
For Blank | 1 | b = | |||
2 |
Calculation
CONCLUSION
Saponification value of the given oil/fat is …….
REFERENCES
- Advanced Practical Organic Chemistry by O. P. Agarwal; Published by Krishna Prakashan Media (P) Ltd; Page No. 275
- Indian Pharmacoepia 2010, Part I; Page No. 93
- Practical Pharmacognosy by Saroja Joshi and Vidhu Aeri; Published by Frank Bros . & Co. (Publishers) Ltd.; First Edition: 2009; Page No. 296
Also read:
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