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SAPONIFICATION

SAPONIFICATION. BACKGROUND.

phylicia-fauna
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SAPONIFICATION

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  1. SAPONIFICATION

  2. BACKGROUND • When fatty acids are heated with alkali metals or alkaline earth metals, salts of fatty acids are formed, which are called soaps. The soaps of sodium and potassium are used in daily life. Sodium soaps are hard, therefore small amounts of silicate is mixed with them to make them soft and useable as toilet soaps. Potassium salts are soft but costly, they are used in liquid soaps, shampoo and shaving creams. In hospitals, tinture green soap is most commonly used which is an alcoholic solution of potassium soap. Calcium and magnesium soaps are insoluble in water.

  3. principle • The process of soap formation is called saponification. Triglycerides present in the given lipid on treatment with hot alkali (NaOH) will be hydrolyzed to prroduce glycerol and sodium salts of fatty acids (soap). When calcium chloride or magnesium chloride is added to the soap solution, the calcium or magnesium salts of fatty acids are formed which are precipitated because they are highly insoluble. Similarly, when the soap solution is acidified, the soap is converted to free fatty acids which being insoluble in water are precipitated.

  4. reagents • Ethanol • Saturated solution of sodium hydroxide in alcohol • Saturated solution of NaCl in water • Saturated solution of CaCl2 in water • Saturated solution of KCl in water • Concentrated HCl

  5. procedure • Take a clean dry test tube and add 0.5 ml of the provided oil. Then add 2.5 ml of ethanol to it and mix it well. • After mixing, add 10 ml of 10 % alcoholic sodium hydroxide. Shake well and keep the test tubes in boiling water bath for 15 minutes. Add water to make a total volume of 20 ml. shake well to dissolve. • Take four test tubes and label them as A, B, C and D. divide the above solution into following four test tubes, i.e., 5 ml in each.

  6. To test tube A, add 5 ml of NaCl and shake. • To test tube B, add 3 drops of CaCl2 and shake. • To test tube C, add 3 drops of KCl solution and shake. • To test tube D, add 3 ml of concentrated HCl and shake. • Do not disturb these test tubes for 15 minutes.

  7. interpretation • In test tube A, sodium salt of fatty acid rises up and forms a pale white layer. • In test tube B, a white precipitate of calcium salt of fatty acids is formed. • In test tube C, potassium salt of fatty acid rises up. • In test tube D, a white precipitate of liberated free fatty acids is obtained.

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