Calcium hypochlorite

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Calcium hypochlorite or Calcium oxychloride
Calcium hypochlorite
Identifiers
CAS number 7778-54-3 YesY
ChemSpider 22912 YesY
EC number 231-908-7
UN number 1748
RTECS number NH3485000
Jmol-3D images Image 1
Properties
Molecular formula Ca(ClO)2
Molar mass 142.98 g/mol
Appearance white/gray powder
Density 2.35 g/cm3 (20 °C)
Melting point 100 °C
Boiling point 175 °C, decomposes
Solubility in water 21 g/100 mL, reacts
Solubility reacts in alcohol
Hazards
MSDS ICSC 0638
EU Index 017-012-00-7
EU classification Oxidant (O)
Corrosive (C)
Harmful (Xn)
Dangerous for the environment (N)
R-phrases R8, R22, R31, R34, R50
S-phrases (S1/2), S26, S36/37/39, S45, S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
Flash point Non-flammable
LD50 850 mg/kg (oral, rat)
Related compounds
Other anions Calcium chloride
Other cations Sodium hypochlorite
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Calcium hypochlorite also known as chlorine powder or bleach powder[1] is a chemical compound with formula Ca(ClO)2. It is widely used for water treatment and as a bleaching agent. This chemical is considered to be relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach).

Uses[edit]

Calcium hypochlorite is used for the disinfection of drinking water or swimming pool water. Generally it is sold as 68% calcium hypochlorite combined with calcium chloride and other salts. 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 an ingredient in bleaching powder, used for bleaching cotton and linen. It is used in bathroom cleaners, household disinfectant sprays, moss and algae removers, and weedkillers.

In addition, calcium hypochlorite may be used to manufacture chloroform.

Chlorine compounds, including calcium hypochlorite, are widely used in the food industry to kill bacteria and disinfect surfaces and production equipment.[2]

Safety[edit]

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.[citation needed]

Preparation[edit]

Calcium hypochlorite is manufactured by the calcium process:

2 Cl
2
+ 2 Ca(OH)
2
Ca(OCl)
2
+ CaCl
2
+ 2 H
2
O

Bleaching powder is a mixture obtained through the above reaction: calcium hypochlorite, calcium chloride and water with some unreacted slaked lime, Ca(OH)2.[3]

Properties[edit]

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: dry and hydrated. The hydrated form is safer to handle.

Calcium hypochlorite reacts with carbon dioxide to form calcium carbonate and release dichlorine monoxide:

Ca(ClO)
2
+ CO
2
CaCO
3
+ Cl
2
O

A calcium hypochlorite solution is basic. This is due to the hydrolysis performed by the hypochlorite ion, as hypochlorous acid is weak, but calcium hydroxide is a strong base. As a result, the hypochlorite ion is a strong conjugate base, and the calcium ion is a weak conjugate acid:

ClO
+ H2O → HClO + OH

Similarly, calcium hypochlorite reacts with hydrochloric acid to form calcium chloride, water and gaseous chlorine:

Ca(OCl)2 + 4 HCl → CaCl2 + 2 H2O + 2 Cl2

References[edit]

  1. ^ Gerald F. Connell. "KEY OPERATING STRATEGIES FOR CHLORINE DISINFECTION OPERATING SYSTEMS". Retrieved 19 October 2014. 
  2. ^ Chemical Products Synopsis: Calcium Hypochlorite (Technical report). Asbuiy Park, NJ: Mannsvile Chemical Products. 1987. 
  3. ^ Patnaik, Pradyot (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 0-07-049439-8. 

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