Calcium hypochlorite
Calcium hypochlorite is an inorganic compound with chemical formula Template:Chem2, also written as Template:Chem2. It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow decomposition in moist air. This compound is relatively stable as a solid and solution and has greater available chlorine than sodium hypochlorite.[1] "Pure" samples have 99.2% active chlorine. Given common industrial purity, an active chlorine content of 65-70% is typical.[2] It is the main active ingredient of commercial products called bleaching powder,Template:Efn used for water treatment and as a bleaching agent.[3]
History
Charles Tennant and Charles Macintosh developed an industrial process in the late 18th century for the manufacture of chloride of lime, patenting it in 1799.[4] Tennant's process is essentially still used today,[4][3] and became of military importance during World War I, because calcium hypochlorite was the active ingredient in trench disinfectant.[4]
Uses
Sanitation
Calcium hypochlorite is commonly used to sanitize public swimming pools and disinfect drinking water. Generally the commercial substances are sold with a purity of 65% to 73% with other chemicals present, such as calcium chloride and calcium carbonate, resulting from the manufacturing process. In solution, calcium hypochlorite could be used as a general purpose sanitizer,[5] but due to calcium residue (making the water harder), sodium hypochlorite (bleach) is usually preferred.
Organic chemistry
Calcium hypochlorite is a general oxidizing agent and therefore finds some use in organic chemistry.[6] For instance the compound is used to cleave glycols, α-hydroxy carboxylic acids and keto acids to yield fragmented aldehydes or carboxylic acids.[7] Calcium hypochlorite can also be used in the haloform reaction to manufacture chloroform.[8] Calcium hypochlorite can be used to oxidize thiol and sulfide byproducts in organic synthesis and thereby reduce their odour and make them safe to dispose of.[9] The reagent used in organic chemistry is similar to the sanitizer at ~70% purity.[10]
Production
Calcium hypochlorite is produced industrially by reaction of moist slaked calcium hydroxide with chlorine gas. The one-step reaction is shown below:[3]
Industrial setups allow for the reaction to be conducted in stages to give various compositions, each producing different ratios of calcium hypochlorite, unconverted lime, and calcium chloride.[3] In one process, the chloride-rich first stage water is discarded, while the solid precipitate is dissolved in a mixture of water and lye for another round of chlorination to reach the target purity.[2] Commercial calcium hypochlorite consists of anhydrous Template:Chem2, dibasic calcium hypochlorite Template:Chem2 (also written as Template:Chem2), and dibasic calcium chloride Template:Chem2 (also written as Template:Chem2).[11][12]
Reactions
Calcium hypochlorite reacts rapidly with acids producing calcium chloride, chlorine gas, and water:Script error: No such module "Unsubst".
Safety
It is a strong oxidizing agent, as it contains a hypochlorite ion at the valence +1 (redox state: Cl+1).Script error: No such module "Unsubst".
Calcium hypochlorite should not be stored wet and hot, or near any acid, organic materials, or metals. The unhydrated form is safer to handle.Script error: No such module "Unsubst".
See also
References
Template:Notelist Template:Reflist
External links
Template:Calcium compounds Template:Hypochlorites
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- ↑ W.L Smith, Inorganic Bleaches, Production of Hypochlorite in Handbook of Detergents,Part F, (2009) Ed. U Zoller and Paul Sosis, CRC Press, Template:ISBN
- ↑ Script error: No such module "Citation/CS1".