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 (212 °F; 373 K)
Boiling point 175 °C (347 °F; 448 K) 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]

Sanitation[edit]

Calcium hypochlorite is commonly used to sanitize public swimming pools and disinfect drinking water. Generally the commercial substance is sold with a purity of a 68% (with other additives and contaminants varying based upon the product's intended purpose). For instance as a swimming pool chemical it is often mixed with cyanuric acid stabilizers and anti-scaling agents (in order to reduce the loss of chlorine from ultraviolet radiation and to prevent calcium hardening). Calcium hypochlorite is also used in kitchens to disinfect surfaces and equipment.[2] Other common uses include bathroom cleansers, household disinfectant sprays, algaecides, herbicides, and laundry detergents.

Organic chemistry[edit]

Calcium hypochlorite is a general oxidizing agent and therefore has many uses in organic chemistry.[3] For instance the compound is used to cleave glycols, α-hydroxy carboxylic acids and keto acids to yield fragmented aldehydes or carboxylic acids.[4] Calcium hypochlorite is also used in the haloform reaction to manufacture chloroform.[5]

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 passing chlorine gas through a solution of calcium hydroxide:

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

Bleaching powder was made by passing chlorine gas with slightly moist slaked lime. This formed a white powder. The exact constitution depends on the maufacturing conditions. It is not a simple mixture of calcium hypochlorite, calcium chloride and calcium hydroxide. It is believed to be a variable mixture consisting pricipally of calcium hypochlorite Ca(OCl)2 , dibasic calcium hypochlorite, Ca3(OCl)2(OH)4 and dibasic calcium chloride, Ca3Cl2(OH)4.[6]

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. ^ Nwaukwa, Stephen; Keehn, Philip (1982). "The oxidation of aldehydes to acids with calcium hypochlorite [Ca(OCl)2]". Tetrahedron Letters 23 (31): 3131–3134. doi:10.1016/S0040-4039(00)88577-9. 
  4. ^ Nwaukwa, Stephen; Keehn, Philip (1982). "Oxidative cleavage of α-diols, α-diones, α-hydroxy-ketones and α-hydroxy- and α-keto acids with calcium hypochlorite [Ca(OCl)2]". Tetrahedron Letters 23 (31): 3135–3138. doi:10.1016/S0040-4039(00)88578-0. 
  5. ^ Cohen, Julius (1900). Practical Organic Chemistry for Advanced Students. Newyork: Macmillan & Co. p. 63. 
  6. ^ W.L Smith, Inorganic bleaches, Production of Hypochlorite in Handbook of Detergents,Part F, (2009) Ed. U Zoller and Paul Sosis, CRCPress, ISBN 978-0-8247-0349-3

External links[edit]