We are going to see a soap making experiment in a school lab. Firstly, we should know what is soap: Soap is a sodium salt or potassium salt of long-chain fatty acids having cleansing action in the water. They are used as cleansing agents to remove dirt, and oil from the skin and clothes. Examples: sodium stearate, sodium oleate, and sodium palmitate formed using stearic acid oleic acid, and palmitic acid.
A Soap Making Experiment in a School Laboratory in Bangladesh:
Principle: An Oil or Fat is a mixture of higher fatty acids and glycerides or triesters of glycerin. Among the higher saturated fatty acids, especially palmitic acid (C15H33COOH), stearic acid (C17H35COOH), and unsaturated fatty acids, oleic acid (C17H33COOH) are present. So heating a sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution with an oil or fat, like all other esters, turns into the sodium or potassium salt of alcohol (in this case glycerin) and an acid. Sodium or potassium salts of fatty acids are soaps. Reaction Formula: C17H35COOH + NaOH —-> C17H35COONa + H2O. [Stearic acid + sodium hydroxide —-> soap + water].
Necessary Materials: 2 beakers, tripod stand, wire net, Buchner funnel, filter paper, suction pump (water driven), glass rod.
Necessary Chemicals: Coconut oil or any other oil or fat, caustic soda, salt (sodium chloride).
The procedure of Soap Making in the Lab:
- Take about 50gm of coconut oil in a large glass beaker.
- Take about 20 grams of caustic soda in another beaker about 100 ml dissolved in water.
- Pour this solution into the first beaker.
- The beaker was then placed on a tripod stand on a wire net and heated with a bunsen burner to keep it boiling.
- At one time there was no difference seen between the two levels.
- Then remove the Bunsen burner and let it cool.
- Then add about 10 grams of common salt (sodium chloride) little by little and stir with a glass rod so that it dissolves in the solution. Now I noticed that the soap kept separating from the solution.
- Leave it in that state for half an hour.
- After that put the filter paper in the Buchner funnel and filter with the help of an absorption pump. The residue obtained on the filter paper is soap. Dry it in the air to get the dry soap.
Cautions:
- Aprons and goggles should always be used in the laboratory.
- A mixture of oil and caustic soda is slowly heated.
- When the mixture begins to boil, the flame is moved away.
- Add salt and mix well.
- While filtering the mixture is poured dropwise onto the filter paper.
Source of information: The Practical book for class ix-x published by The Royal Scientific Publications.
