Saponification is the process by which the fatty acids in the glycerides of the oil are hydrolyzed by an alkali. Saponification value is the amount (mg) of alkali required to saponify a definite quantity (1g) of an oil or fat. This value is useful for a comparative study of the fatty acid chain length in oils.
A known quantity of oil is refluxed with an excess amount of alcoholic KOH. After saponification, the remaining KOH is estimated by titrating it against a standard acid.
» Hydrochloric acid 0.5N, accurately standardized.
» Alcoholic KOH – Dissolve 40g KOH in one liter of distilled alcohol keeping the temperature below 15.5oC while the alkaline is being dissolved. This solution should remain clear.
» Phenolphthalein Indicator – 1% in 95% alcohol.
» Air Condenser.
1. Alcohol is inflammable. Use electrical heating.
2. Alcohol should not get dried up during saponification. Effective cooling of alcohol vapor is essential.
3. Clarity and homogeneity of the test solution are indicators of complete saponification.
1. William Horowitz (ed) (1975) Official Methods of Analysis of AOAC Association of Official Analytical Chemists Washington 12th Ed p 490.
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