Loading...Calcium Hypochlorite or Sodium Hypochlorite may be used in Hypochlorite bleaching. Calcium Hypochlorite has cheap sources and hence less expensive than sodium Hypochlorite. But sodium Hypochlorite has some technical advantages.
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Common Recipe :
- Hypochlorite
- Wetting Agent
- Soda Ash
- Temperature
Bleaching Action:
When calcium hypochlorite or sodium Hypochlorite is hydrolyzed, hypochlorous acid is formed which ionize under a certain condition and give per-hydroxide Ion (OCl–) which are responsible for bleaching action.
Ca(OCl)2+2H2O———-> Ca(OH)2+ 2HOCl (HOCl = Hypoclorus Acid)
HOCl ======== (H+) (OCl–) Where (OCl–) is responsible for bleaching.
Like Ca(OCl)2 we can bleach with NaOCl.
NaOCl + H2O————-NaOH + HOCl Where, HOCl is hypochlorus Acid.
It cause Bleaching like as above
HOCl ========(H+) ( OCl–)
When Calcium Hypochlorite is used, it reacts with atmospheric carbon-dioxide to give calcium carbonate.
Ca(OCl)2+H2O +CO2 —————— CaCO3↓ + 2 HOCl
Calcium carbonate is deposited on the fabric surface and cause harsh handling and uneven dyeing. Hence, it have to separate and (Acid Treatement) / scouring is done to remove it.
CaCO3+2HCl ———————- CaCl2+ CO2+H2O
Sodium hypochlorite does not react with atmospheric carbon-dioxide and hence no additional treatment is required. This is the technical advantage of sodium hypochlorite over calcium hypochlorite.
