Calcium Hypochlorite

Calcium hypochlorite
Names
	Other names Hypochlorous acid calcium salt, bleaching powder, chloride of lime
Identifiers
CAS Number	7778-54-3 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:31342;
ChEMBL	ChEMBL2251447;
ChemSpider	22912 ;
EC Number	231-908-7;
KEGG	D01727;
PubChem CID	24504;
RTECS number	NH3485000;
UNII	11DXB629VZ;
UN number	1748 2208
	InChI InChI=1S/Ca.2ClO/c;21-2/q+2;2-1 Key: ZKQDCIXGCQPQNV-UHFFFAOYSA-N ; InChI=1S/Cacl.ClO/c;1-2/q+2;2*-1 Key: ZKQDCIXGCQPQNV-UHFFFAOYAV;
	SMILES Cl[O-].[Ca+2].Cl[O-];
Properties
Chemical 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 at 25 °C
Solubility	reacts in alcohol
Hazards
Safety data sheet	ICSC 0638
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H272, H302, H314, H400
GHS precautionary statements	P210, P220, P221, P260, P264, P270, P273, P280, P301+312, P301+330+331, P303+361+353, P304+340, P305+351+338, P310, P321, P330, P363, P370+378, P391, P405, P501
NFPA 704 (fire diamond)	0 3 1 OX
Flash point	Non-flammable
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	850 mg/kg (oral, rat)
Related compounds
Other anions	Calcium chloride
Other cations	Sodium hypochlorite
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Calcium hypochlorite is an inorganic compound with formula Ca(ClO)₂. 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,^{[lower-alpha 1]} used for water treatment and as a bleaching agent.^[3]

History

Charles Tennant and Charles Macintosh developed an industrial process for the manufacture of Chloride of Lime in the late 18th Century.^[4] It was patented in 1799 and used heavily during World War I for disinfecting the trenches and wounds.

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 treating moist slaked lime (Ca(OH)₂) with chlorine. The one-step reaction is shown below:^[3]

2 Cl
2 + 2 Ca(OH)
2 → Ca(ClO)
2 + CaCl
2 + 2 H
2O

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 Ca(ClO)₂, dibasic calcium hypochlorite Ca₃(ClO)₂(OH)₄ (also written as Ca(ClO)₂·2Ca(OH)₂), and dibasic calcium chloride Ca₃Cl₂(OH)₄ (also written as CaCl₂·2Ca(OH)₂).^[11]^[12]

Reactions

Calcium hypochlorite reacts rapidly with acids producing calcium chloride, chlorine gas, and water:

Ca(ClO)
2 + 4HCl → CaCl
2 + 2Cl
2 + 2H
2O

Safety

It is a strong oxidizing agent, as it contains a hypochlorite ion at the valence +1 (redox state: Cl+1).

Calcium hypochlorite should not be stored wet and hot, or near any acid, organic materials, or metals. The unhydrated form is safer to handle.

References

↑ also chlorine powder, chloride of lime, chlorinated lime, "dry chlorine"

↑ "Key operating strategies for chlorine disinfection operating systems". http://www.environmental-expert.com/Files\5306\articles\13866\500.pdf.
↑ ^2.0 ^2.1 "Calcium Hypochlorite - 3V Tech" (in en). https://www.3v-tech.com/en/technologies-and-solutions/13/calcium-hypochlorite.
↑ ^3.0 ^3.1 ^3.2 Vogt, H.; Balej, J; Bennett, J. E.; Wintzer, P.; Sheikh, S. A.; Gallone, P.; Vasudevan, S.; Pelin, K. (2010). Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a06_483.pub2. ISBN 978-3527306732.
↑ "Calcium hypochlorite". Chemistry World. https://www.chemistryworld.com/podcasts/calcium-hypochlorite/3008985.article.
↑ Chemical Products Synopsis: Calcium Hypochlorite (Technical report). Asbuiy Park, NJ: Mannsvile Chemical Products. 1987.
↑ Nwaukwa, Stephen; Keehn, Philip (1982). "The oxidation of aldehydes to acids with calcium hypochlorite [Ca(ClO)₂]". Tetrahedron Letters 23 (31): 3131–3134. doi:10.1016/S0040-4039(00)88577-9.
↑ 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(ClO)₂]". Tetrahedron Letters 23 (31): 3135–3138. doi:10.1016/S0040-4039(00)88578-0.
↑ Cohen, Julius (1900). Practical Organic Chemistry for Advanced Students. New York: Macmillan & Co.. p. 63. https://books.google.com/books?id=0xRIAAAAIAAJ.
↑ National Research Council (1995). Prudent Practices in the Laboratory: Handling and Disposal of Chemicals. Washington, DC: The National Academies Press. p. 161. doi:10.17226/4911. ISBN 978-0-309-05229-0.
↑ "8.41799 Calcium hypochlorite for synthesis". https://www.sigmaaldrich.com/BE/en/product/mm/841799. "Assay (iodometric): 67.0 - 75.0 %"
↑ 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
↑ Aleksandrova, M.M.; Dmitriev, G.A.; Avojan, R.L. (1968). "The probable model of the crystal structure of the twobase calcium hypochlorite". Armyanskii Khimicheskii Zhurnal 21: 380-386.

External links

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Original source: https://en.wikipedia.org/wiki/Calcium hypochlorite. Read more

[3] so chlorine powder, chloride of lime, chlorinated lime, "dry chlorine"

[1] "Key operating strategies for chlorine disinfection operating systems". http://www.environmental-expert.com/Files\5306\articles\13866\500.pdf.

[3V-2] 2.0 ^2.1 "Calcium Hypochlorite - 3V Tech" (in en). https://www.3v-tech.com/en/technologies-and-solutions/13/calcium-hypochlorite.

[Ullmann-4] 3.0 ^3.1 ^3.2 Vogt, H.; Balej, J; Bennett, J. E.; Wintzer, P.; Sheikh, S. A.; Gallone, P.; Vasudevan, S.; Pelin, K. (2010). Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a06_483.pub2. ISBN 978-3527306732.

[:0-5] "Calcium hypochlorite". Chemistry World. https://www.chemistryworld.com/podcasts/calcium-hypochlorite/3008985.article.

[6] Chemical Products Synopsis: Calcium Hypochlorite (Technical report). Asbuiy Park, NJ: Mannsvile Chemical Products. 1987.

[7] Nwaukwa, Stephen; Keehn, Philip (1982). "The oxidation of aldehydes to acids with calcium hypochlorite [Ca(ClO)₂]". Tetrahedron Letters 23 (31): 3131–3134. doi:10.1016/S0040-4039(00)88577-9.

[8] 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(ClO)₂]". Tetrahedron Letters 23 (31): 3135–3138. doi:10.1016/S0040-4039(00)88578-0.

[9] Cohen, Julius (1900). Practical Organic Chemistry for Advanced Students. New York: Macmillan & Co.. p. 63. https://books.google.com/books?id=0xRIAAAAIAAJ.

[10] National Research Council (1995). Prudent Practices in the Laboratory: Handling and Disposal of Chemicals. Washington, DC: The National Academies Press. p. 161. doi:10.17226/4911. ISBN 978-0-309-05229-0.

[11] "8.41799 Calcium hypochlorite for synthesis". https://www.sigmaaldrich.com/BE/en/product/mm/841799. "Assay (iodometric): 67.0 - 75.0 %"

[12] 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

[13] Aleksandrova, M.M.; Dmitriev, G.A.; Avojan, R.L. (1968). "The probable model of the crystal structure of the twobase calcium hypochlorite". Armyanskii Khimicheskii Zhurnal 21: 380-386.