Soaps & Detergents
Soaps
» 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.
Detergents
» 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)