Working of  bleaching agents: Let us discuss working of following bleaching agents:


 i) Sodium hypochlorite (NaOCl)

ii) Hydrogen peroxide (H2O2)

iii) Sodium Chlorite (NaClO2)

      Before bleaching, cotton fabric should be prepared well i.e it should be desized (if woven and having sizing chemicals) and scoured. If  material is not prepared well then there are chances of uneven bleaching effect.

i) Sodium Hypochlorite (Manufacture, Reaction and Mechanism): It is a stronger oxidative bleaching chemicals used in textile industry. This manufacture by bubbling chlorine into a solution of sodium hydroxide.

2NaOH + Cl2 --------------   NaOCl  + NaCl

when acid is added to a hypochlorite   solution,   chlorine gas is liberated

NaOCl + HCl---------------- NaCl  +  Cl2    +  H2O

        Commercial NaOCl mostly contains 12-15% active chlorine while household bleach contain around 5% active chlorine. NaOCl is strong alkaline having pH around 12 and free caustic present in the solution act as a stablizer. To make it stable, it should be kept in dark room. 

NaOCl  +  H2O----------------- Na + +  OCl- (Hypochlorous ion)

OCl- + H2O-------------------- HOCl  +  OH-

Hypochlorous acid (HOCl) is a active bleaching agent.