Bleaching powder (CaOCl2)

Bleaching powder is a mixture of calcium hypochlorite, Ca(OCl)2 and calcium chloride CaCl2. Thus, its chemical composition is Ca(OCl)2 + CaCl2 or can be written as CaOCl2 or Ca(OCl)Cl (Calcium chloro hypochlorite).

Bleaching powder is manufactured by passing chlorine gas over dry slaked lime at 400 C.

Ca(OH)2 + Cl2   CaOCl2 + H2O


  1. It is an yellowish white powder with strong smell of chlorine and is soluble in water. Aqueous solution of bleaching powder contains chloride and hypochlorite ions.

CaOCl2  ↔ Ca 2+ + Cl- + ClO-

  1. In presence of small quantities of dilute acids, it liberates nascent oxygen. Thus it act as oxidizing agent.

2CaOCl2 + H2SO  CaCl2 + CaSO4 + 2HClO

HClO  HCl + [O]

  1. When bleaching powder is treated with excess of dilute acid or CO2, whole of the chlorine present in the molecules is evolved. The amount chlorine so liberated is called available chlorine. A good sample of bleaching powder contains 35-38% available chlorine.

CaCl2 + 2HCl  CaCl2 + H2O + Cl2

CaOCl2 + CO  CaCO3 + Cl2