Calcium hypochlorite: Difference between revisions

| verifiedrevid = 450959568

| Name = Calcium hypochlorite

| ImageFile = Calcium hypochlorite.png

| ImageSize =

| ImageName = Calcium oxychloride

| OtherNames = {{ubl|Hypochlorous acid calcium salt|Bleaching powder|Chloride of lime}}

| IUPACName =

| SystematicName =

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| InChI = 1S/Cacl.ClO/c;1-2/q+2;2*-1

| SMILES = Cl[O-].[Ca+2].Cl[O-]

| CASNo_Ref = {{cascite|correct|CAS}}

| EINECS = 231-908-7

| PubChem = 24504

| RTECS = NH3485000

| UNNumber = 1748 2208

| ChEBI = 31342

| ChEMBL = 2251447

| KEGG = D01727

| UNII = 11DXB629VZ

}}

| Formula = {{chem2|Ca(OCl)2}}

| Ca=1|O=2|Cl=2

| Appearance = white/gray powder

| Density = 2.35 g/cm³ (20 °C)

| Solubility = 21 g/(100 mL) at 25 °C

| SolubleOther = reacts in [[Alcohol (chemistry)|alcohol]]

| MeltingPtC = 100

| MeltingPt_notes =

| BoilingPtC = 175

| BoilingPt_notes = decomposes

}}

| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0638.htm ICSC 0638]

| GHSPictograms = {{GHS03}}{{GHS05}}{{GHS07}}{{GHS09}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|272|302|314|400}}

| PPhrases = {{P-phrases|210|220|221|260|264|270|273|280|301+312|301+330+331|303+361+353|304+340|305+351+338|310|321|330|363|370+378|391|405|501}}

| NFPA-H = 3

| NFPA-F = 0

| NFPA-R = 1

| NFPA-S = OX

| FlashPt = Non-flammable

| LD50 = 850 mg/kg (oral, rat)

}}

| Section4 =

| Section5 =

| Section6 =

|Section8 = {{Chembox Related

|OtherAnions = {{ubl|[[Calcium chloride]]|[[Calcium chlorite]]|[[Calcium chlorate]]|[[Calcium perchlorate]]}}

|OtherCations = {{ubl|[[Lithium hypochlorite]]|[[Sodium hypochlorite]]|[[Potassium hypochlorite]]|[[Barium hypochlorite]]|[[Silver hypochlorite]]}}

|OtherCompounds = {{ubl|[[Hypochlorite]]|[[Chlorine monoxide]]|[[Hypochlorous acid]]|[[Methyl hypochlorite]]}}

}}

'''Calcium hypochlorite''' is an [[inorganic compound]] with [[chemical formula]] {{chem2|Ca(ClO)2|auto=1}}, also written as {{chem2|Ca(OCl)2}}. It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow [[Chemical decomposition|decomposition]] in moist air. This compound is relatively stable as a solid and solution and has greater available [[chlorine]] than [[sodium hypochlorite]].<ref>{{cite web|author1=Gerald F. Connell|title=Key operating strategies for chlorine disinfection operating systems|url=http://www.environmental-expert.com/Files%5C5306%5Carticles%5C13866%5C500.pdf|access-date=19 October 2014}}</ref> "Pure" samples have 99.2% [[active chlorine]]. Given common industrial purity, an active chlorine content of 65-70% is typical.<ref name=3V>{{cite web |title=Calcium Hypochlorite - 3V Tech |url=https://www.3v-tech.com/en/technologies-and-solutions/13/calcium-hypochlorite |website=www.3v-tech.com |language=en}}</ref> It is the main active ingredient of commercial products called '''bleaching powder''',{{efn|also '''chlorine powder''', '''chloride of lime''', '''chlorinated lime''', "dry chlorine"}} used for [[water treatment]] and as a [[bleaching agent]].<ref name="Ullmann" />

==History==

[[Charles Tennant]] and [[Charles Macintosh]] developed an industrial process in the late 18th century for the manufacture of chloride of lime, patenting it 1799.<ref name=CWTrench/> Tennant's process is essentially still used today,<ref name=CWTrench/><ref name=Ullmann/> and became of military importance during [[World War I]], because calcium hypochlorite was the active ingredient in [[trench warfare|trench]] disinfectant.<ref name=CWTrench>{{cite web|url=https://www.chemistryworld.com/podcasts/calcium-hypochlorite/3008985.article |title=Calcium hypochlorite |publisher=Chemistry World}}</ref>

==Uses==

===Sanitation===

Calcium hypochlorite is commonly used to [[swimming pool sanitation|sanitize public swimming pools]] and [[water treatment|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,<ref>{{cite tech report|institution=Mannsvile Chemical Products |date=1987 |title=Chemical Products Synopsis: Calcium Hypochlorite |location=Asbuiy Park, NJ}}</ref> but due to calcium residue (making [[hard water|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]].<ref>{{cite journal|last1=Nwaukwa|first1=Stephen|last2=Keehn|first2=Philip|title=The oxidation of aldehydes to acids with calcium hypochlorite [Ca(ClO)₂]|journal=Tetrahedron Letters|date=1982|volume=23|issue=31|pages=3131–3134|doi=10.1016/S0040-4039(00)88577-9}}</ref> For instance the compound is used to [[Bond cleavage|cleave]] [[Diol#Vicinal diols|glycol]]s, [[Alpha hydroxy acid|α-hydroxy carboxylic acids]] and [[keto acid]]s to yield fragmented [[aldehyde]]s or [[carboxylic acid]]s.<ref>{{cite journal|last1=Nwaukwa|first1=Stephen|last2=Keehn|first2=Philip|title=Oxidative cleavage of α-diols, α-diones, α-hydroxy-ketones and α-hydroxy- and α-keto acids with calcium hypochlorite [Ca(ClO)₂]|journal=Tetrahedron Letters|date=1982|volume=23|issue=31|pages=3135–3138|doi=10.1016/S0040-4039(00)88578-0}}</ref> Calcium hypochlorite can also be used in the [[haloform reaction]] to manufacture [[chloroform]].<ref>{{cite book|last1=Cohen|first1=Julius|title=Practical Organic Chemistry for Advanced Students|date=1900|publisher=Macmillan & Co.|location=New York|page=63|url=https://books.google.com/books?id=0xRIAAAAIAAJ}}</ref>

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.<ref>{{cite book |last1=National Research Council |title=Prudent Practices in the Laboratory: Handling and Disposal of Chemicals |date=1995 |publisher=The National Academies Press |location=Washington, DC |page=161 |doi=10.17226/4911 |isbn=978-0-309-05229-0}}</ref> The reagent used in organic chemistry is similar to the sanitizer at ~70% purity.<ref>{{cite web |title=8.41799 Calcium hypochlorite for synthesis |url=https://www.sigmaaldrich.com/BE/en/product/mm/841799 |website=Sigma-Aldrich |quote=Assay (iodometric): 67.0 - 75.0 %}}</ref>

==Production==

Calcium hypochlorite is produced industrially by treating moist slaked [[Lime (material)|lime]] ({{chem2|Ca(OH)2}}) with [[chlorine]]. The one-step reaction is shown below:<ref name=Ullmann>{{cite encyclopedia|last1=Vogt|first1=H.|last2=Balej|first2=J|last3=Bennett|first3=J. E.|last4=Wintzer|first4=P.|last5=Sheikh|first5=S. A.|last6=Gallone|first6=P.|last7=Vasudevan|first7=S.|last8=Pelin|first8=K.|year=2010|chapter=Chlorine Oxides and Chlorine Oxygen Acids|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|publisher=Wiley-VCH|doi=10.1002/14356007.a06_483.pub2|isbn=978-3527306732|s2cid=96905077}}</ref>

:{{chem2|2 Cl2 + 2 Ca(OH)2 → CaCl2 + Ca(OCl)2 + 2 H2O}}

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]].<ref name=Ullmann/> 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.<ref name=3V/> Commercial calcium hypochlorite consists of anhydrous {{chem2|Ca(OCl)2}}, dibasic calcium hypochlorite {{chem2|Ca3(OCl)2(OH)4}} (also written as {{chem2|Ca(OCl)2*2Ca(OH)2}}), and dibasic calcium chloride {{chem2|Ca3Cl2(OH)4}} (also written as {{chem2|CaCl2*2Ca(OH)2}}).<ref>W.L Smith, Inorganic Bleaches, Production of Hypochlorite in ''Handbook of Detergents,Part F'', (2009) Ed. U Zoller and Paul Sosis, CRC Press, {{ISBN|978-0-8247-0349-3}}</ref><ref>{{cite journal|author=Aleksandrova, M.M.; Dmitriev, G.A.; Avojan, R.L.|title=The probable model of the crystal structure of the twobase calcium hypochlorite|journal=Armyanskii Khimicheskii Zhurnal|year=1968|volume=21|page=380-386}}</ref>

== Reactions ==

Calcium hypochlorite reacts rapidly with acids producing [[calcium chloride]], chlorine gas, and water:{{cn|date=November 2023}}

:{{chem2|Ca(ClO)2 + 4 HCl → CaCl2 + 2 Cl2 + 2 H2O}}

==Safety==

It is a strong [[oxidizing agent]], as it contains a [[hypochlorite]] ion at the valence +1 (redox state: Cl+1).{{cn|date=November 2023}}

Calcium hypochlorite should not be stored wet and hot, or near any acid, organic materials, or metals. The unhydrated form is safer to handle.{{cn|date=November 2023}}

== See also ==

* [[Calcium hydroxychloride]]

* [[Sodium hypochlorite]]

* [[Winchlor]]

{{notelist}}

{{Hypochlorites}}