Question

Glycerol is added to soap. It functions:
A. as a filler
B. to increase lathering
C. to prevent rapid drying
D. to make soap granules

Answer 1

Soaps are compounds of sodium and potassium salts of long chain fatty acids. The reaction that produces soaps is known as saponification reaction. Soaps are widely used as cleansing agents due to their properties to eliminate dirt and oil.

Complete step-by-step answer: Soap is made from sodium or potassium salts of long chain carboxylic acids. Soaps consist of two parts, hydrophilic or ionic and hydrophobic, or the carbon chain part. The hydrophilic or ionic part that has sodium and potassium ions is water soluble, while the hydrophobic part that has the hydrocarbon chain is water repelling. As soap is mixed with water, the ionic part gets dissolved in water resulting in micelle formation, while the carbon chain gets attached with dirt and oil, and gets removed with agitation of the cloth.
In the preparation of soaps, glycerol, which is a type of polyol, also known as glycerin in common language, is added. The role of glycerol in soap is to retain moisture. It acts as a humectant, which prevents the soap from becoming dry and leaves a moisturizing and hydrating effect for the soap.

Hence, glycerol in soap is added to prevent rapid drying. So, option C is correct.

Note: Glycerol is a part of glycerides, which are compounds containing more than two alcohol groups. The presence of these glycerols, in face products and moisturizers, gives our skin a hydrated feel, and prevents drying of skin.