Triglycerides or triacylglycerols are composed of three fatty acids each in ester linkage with a single glycerol. Since the polar hydroxyls of glycerol and the polar carboxylates of the fatty acids are bound in ester linkages, triacyl glycerols are non polar hydrophobic molecules, which are insoluble in water. Saponification is the hydrolysis of fats or oils under basic conditions to afford glycerol and the salt of the corresponding fatty acid.
The saponification number is the number of milligrams of potassium hydroxide required to neutralize the fatty acids resulting from the complete hydrolysis of 1 g of fat. It gives information concerning the character of the fatty acids of the fat. The longer the carbon chain, the less acid is liberated per gram of fat hydrolyzed. It is also considered as a measure of the average molecular weight or chain length of all the fatty acid present. The long chain fatty acids found in fats have low saponification value because they have a relatively fewer of carboxylic functional groups per unit mass of the fat and therefore high molecular weight. The principle in this experiment is fats (triglycerides) upon alkaline hydrolysis (either with KOH or NaOH) yield glycerol and potassium or sodium salts of fatty acids (soap).
In this experiment, there are 3 types of oil or fat are used such as palm oil, corn oil and sunflower oil. The result shows that sunflower oil has the highest saponification number. So that, it means that sunflower oil has the shortest chain of fatty acid and lower molecular weight. Corn oil is the shorter fatty acid chains and the long fatty acid chains is the palm oil with high molecular weight. However, all the results obtained are differ from the theoretical value. The actual saponification number of these oils is shown in the Table 2: