Question

What is a 'soap'? How is it prepared?

Answer 1

Soaps : Soaps are generally mixtures of sodium and potassium salts of higher fatty acids such as stearic, palmitic and oleic acids. For effective cleansing action of soap, its fatty acid unit must contain $12$ to $18$ carbon atoms. Soaps with less than $12$ carbon fatty acids are comparatively soluble in water whereas soaps containing more than $22$ carbon atoms are not useful because of their insolubility in water.
Preparation : Shaving creams, shampoos etc. are mostly potassium soaps.
Soaps are usually obtained by the hydrolysis of oils and fats with sodium or potassium hydroxide.
Transparent soaps are prepared by dissolving ordinary soaps in alcohol and then removing the insoluble part by filtration. The solid transparent mass is obtained on evaporating off alcohol.