the mixture to produce the ‘surfactant molecules’, which do not bond with the minerals present in the hard water, thus preventing the formation of their precipitates. In addition to a ‘surfactant’, the modern detergent contains several other ingredients. They are listed as follows: i) Sodium silicate, which prevents the corrosion and ensures that the detergent does not damage the washing machine. ii) Fluorescent whitening agents that give a glow to the clothes.
iii) Oxygen bleaches, such as ‘sodium perborate’, enable the removal of certain stains from the cloth. iv) Sodium sulphate is added to prevent the caking of the detergent powder. v) Enzymes are added to break down some stains caused by biological substances like blood and vegetable juice. vi) Certain chemicals that give out a pleasant smell are also added to make the clothes fragrant after they are washed with detergents.
. . Cleansing action of soap A soap molecule contains two chemically distinct parts that interact differently with water. It has one polar end , which is a short head with a carboxylate group ( – COONa) and one non-polar end having the long tail made of the hydrocarbon chain .
The polar end is hydrophilic (Water loving) in nature and this end is attracted towards water. The non-polar end is hydrophobic (Water hating) in nature and it is attracted towards dirt or oil on the cloth, but not attracted towards water. Thus, the hydrophobic part of the soap molecule traps the dirt and the hydrophilic part makes the entire molecule soluble in water. When a soap or detergent is dissolved in water, the molecules join together as clusters called ‘ micelles ’.
Their long hydrocarbon chains attach themselves to the oil and dirt. The dirt is thus surrounded by the non-polar end of the soap molecules (Figure . ). The charged carboxylate end of the soap molecules makes the micelles soluble in water.
Thus, the dirt is washed away with the soap. Advantages of detergents over soaps Detergents are better than soaps because they: ¾ can be used in both hard and soft