Title: Determination of Saponification Value
1. Objective: To determine the Saponification Value of the sample.
- Principle: The saponification value is the number of milligrams of potassium hydroxide necessary to neutralise the free acids and to saponify the esters present in 1 g of the substance.
3. Procedure:
- Definitions:
- Saponification: A process by which triglycerides are reacted with Sodium or Potassium Hydroxide to produce glycerol and a fatty acid salt is called Saponification.
- Method:
Unless otherwise specified in the individual monograph, introduce about 2 g of the substance being examined, accurately weighed, into a 200 ml flask of borosilicate glass fitted with a reflux condenser. Add 25.0 ml of 0.5 M Ethanolic Potassium Hydroxide and a little pumice powder and boil under reflux on a water-bath for 30 minutes. Add 1 ml of Phenolphthalein solution and titrate immediately with 0.5 M Hydrochloric Acid (a ml). Carry out blank titration omitting the substance being examined (b ml).
Preparation of Reagents:
- 5 M Ethanolic Potassium Hydroxide: Dissolve 2.806 g of Potassium Hydroxide in sufficient ethanol (95%) and dilute to 100 ml with ethanol (95%).
- Phenolphthalein solution: Dissolve 1.0 g of Phenolphthalein in sufficient ethanol (95%) and dilute to 100 ml with ethanol (95%).
Calculate the saponification value from the expression
Saponification value = 28.05 x (b-a)
w
Where, w = weight in gram of the substance.
NOTE: If the oil has been saturated with carbon dioxide for the purpose of preservation, gently reflux the solution of the oil in Ethanol (95%) and Ether for 10 minutes before titration. The oil may be freed from the Carbon dioxide by exposing it in a shallow dish in a vacuum desiccator for 24 hours before weighing the sample.