Detergent is better than soap for the following reasons:
(i) Soap does not work well in hard water since the Ca2+; Mg2+ ions of hard water react with soap forming insoluble substances. So, it creates unnecessary wastage of soap and also does harm to the fiber of the cloth fibres.
RCOONa + Ca2+ (RCOO)2 Ca
On the other hand, detergent works well in both hard acidic water and soft water, since detergent reacts with Ca2+, Mg2+ ions of hard water producing water soluble calcium or magnesium salts. So no harm is done to the garments.
R – OSO3 – Na– + Ca2+ (R – O – SO3)2 Ca
(ii) Detergent is more soluble in water than soap.
(iii) Detergent is active in both acidic and basic media which soap can’t do.
(iv) Detergent is a better cleaning agent than soap.
(v) Detergent can be equally used both in aqueous and non-aqueous media as they have both hydrophilic & hydrophobic ends in their structures.
(vi) Detergent can be used both in solid and liquid loans. But soap can’t used in such ways.
In terms of usage; soaps will undergo substitution reactions with minerals such as Calcium or Magnesium in “Hard Water”. These derivatives are insolunle, and will form “scum” on the surface of the water, detracting from the effectiveness of the soap. Detergents on the other hand are less likely to form these alternate salts, but when they do these salts that form are soluble.