Calcium hypochlorite
history| EINECS = 231-908-7 | RTECS = NH3485000 | UNNumber = 1748 , }} | Section2 = | Section3 = , , , , | SPhrases = , , , , | NFPA-H = 3 | NFPA-F = 0 | NFPA-R = 1 | NFPA-O = OX | FlashPt = Non-flammable | LD50 = 850 mg/kg (oral, rat) , }} | Section8 = }} Calcium hypochlorite is a chemical compound with formula ()2. It is widely used for water treatment and as a bleaching agent (bleaching powder). This chemical is considered to be relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach).
Preparation
It is manufactured by the calcium process and the sodium process. The calcium process proceeds as follows:
:2 + 2 → + + 2
The sodium process proceeds as follows:
:2 + 3 + 2 NaOH → + + 2 + 2 NaCl
Bleaching powder is actually a mixture of calcium hypochlorite (Ca(ClO)2) and the basic chloride CaCl2, Ca(OH)2, H2O with some slaked lime, Ca(OH)2. Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
Properties
Calcium hypochlorite is a yellow white solid which has a strong smell of chlorine. It is not highly soluble in water, and is more preferably used in soft to medium-hard water. It has two forms: a dry form and a hydrated form. The hydrated form is safer to handle.
Calcium hypochlorite reacts with carbon dioxide to form calcium carbonate and release chlorine:
:2 Ca(ClO)2 + 2 CO2 → 2 CaCO3 + 2 Cl2 + O2
Calcium hypochlorite reacts with hydrochloric acid to form calcium chloride: :Ca(ClO)2 + 4 HCl → CaCl2 + 2 H2O + 2 Cl2
Calcium hypochlorite is used for the disinfection of drinking water or swimming pool water. It is used as a sanitizer in outdoor swimming pools in combination with a cyanuric acid stabilizer, which reduces the loss of chlorine due to ultraviolet radiation. The calcium content hardens the water and tends to clog up some filters; hence, some products containing calcium hypochlorite also contain anti-scaling agents.
Calcium hypochlorite is also an ingredient in bleaching powder, used for bleaching cotton and linen. It is also used in bathroom cleaners, household disinfectant sprays, moss and algae removers, and weedkillers.
In addition, calcium hypochlorite may be used to manufacture chloroform.
Calcium hypochlorite is best kept in a cool dry place away from any organic material. It is known to undergo self heating and rapid decomposition accompanied by the release of toxic chlorine gas.
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