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6.4.3 Saponification
The glycerides of the fat may be readily decomposed into glycerol and salts of the constituent fatty acids (Soaps) by boiling with strong bases such as sodium or potassium hydroxide and the process is called saponification. Since fats are insoluble in water, the process is facilitated by the addition of alcohol which dissolves the fat.
The soap and glycerol are soluble in water, but the soap may be separated out by the addition of salt. The glycerol may be recovered from the aqueous solution by careful evaporation of the water followed by vacuum distillation.
The saponification of fats is important not only in the preparation of commercial soaps but also in the chemical examination of fats. Since fats are mixtures of glycerides and the glycerides in turn contain various chain length fatty acids, the saponification number is an index of the average molecular size of the fatty acids present. |