General Knowledge

Soaps & Detergents


» Soaps are sodium or potassium salts of higher fatty acids, such as oleic acid (C17H33COOH), stearic acid (C17H35COOH) and palmitic acid (C15H31COOH).

» Soaps are prepared by saponification of glycerides.

» Only sodium and potassium soaps are soluble in water and are used for cleaning purpose. Some important soaps are:
    Sodium palmitate (C15H31COONa)
    Sodium stearate (C17H35COONa)

» Toilet soaps are prepared by using better grades of fats and oils. Colour and perfumes are also added to make these more attractive.

» Transparent soaps are prepared by dissolving the soap in ethanol and then evaporating excess ethanol.

» Medicated soaps containing substances of medicinal value.

» Laundry soaps contain sodium rosinate, sodium silicate, borax, and sodium carbonate.


» Synthetic detergents are soap less as they do not contain any soap. These are cleansing agents and have all properties of soaps. Detergents contain a Sulphonic Acid group (—SO3H) instead of a carboxylic acid group (—COOH) on one end of the hydrocarbon chain.

» Detergents get preference over soaps because they work even in hard water.

» Detergents with straight chain of hydrocarbons are preferred over branched chain as the latter are non-biodegradable and cause environmental pollution.

Detergents are of three types :
Anionic detergents : (sodium lauryl sulphate and sodium dodecyl benzene sulphonate)
Cationic detergent : (cetyl trimethyl ammonium bromide)
Non-ionic detergent : (polyethylene glycol stearate)