Calcium hypochlorite

Last updated
Calcium hypochlorite
Calcium hypochlorite.png
Names
Other names
  • Hypochlorous acid calcium salt
  • Bleaching powder
  • Chloride of lime
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.029.007 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-908-7
KEGG
PubChem CID
RTECS number
  • NH3485000
UNII
UN number 1748 2208
  • InChI=1S/Ca.2ClO/c;2*1-2/q+2;2*-1 Yes check.svgY
    Key: ZKQDCIXGCQPQNV-UHFFFAOYSA-N Yes check.svgY
  • InChI=1S/Cacl.ClO/c;1-2/q+2;2*-1
    Key: ZKQDCIXGCQPQNV-UHFFFAOYAV
  • Cl[O-].[Ca+2].Cl[O-]
Properties
Ca(OCl)2
Molar mass 142.98 g·mol−1
Appearancewhite/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
21 g/(100 mL) at 25 °C
Solubility reacts in alcohol
Hazards
GHS labelling:
GHS-pictogram-rondflam.svg GHS-pictogram-acid.svg GHS-pictogram-exclam.svg GHS-pictogram-pollu.svg
Danger
H272, H302, H314, H400
P210, P220, P221, P260, P264, P270, P273, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P330, P363, P370+P378, P391, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
3
0
1
OX
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
850 mg/kg (oral, rat)
Safety data sheet (SDS) ICSC 0638
Related compounds
Other anions
Other cations
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Calcium hypochlorite is an inorganic compound with chemical formula Ca(Cl O)2, also written as Ca(OCl)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]

Contents

History

Charles Tennant and Charles Macintosh developed an industrial process in the late 18th century for the manufacture of chloride of lime. [4] It was patented in 1799 and used heavily during World War I for disinfecting the trenches and wounds.[ citation needed ]

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 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. [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(OCl)2, dibasic calcium hypochlorite Ca3(OCl)2(OH)4 (also written as Ca(OCl)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:[ citation needed ]

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).[ citation needed ]

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

See also

Related Research Articles

<span class="mw-page-title-main">Chlorine</span> Chemical element, symbol Cl and atomic number 17

Chlorine is a chemical element; it has symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity on the revised Pauling scale, behind only oxygen and fluorine.

The term chloride refers either to a chloride ion, which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond. Many inorganic chlorides are salts. Many organic compounds are chlorides. The pronunciation of the word "chloride" is.

<span class="mw-page-title-main">Sodium hypochlorite</span> Chemical compound (known in solution as bleach)

Sodium hypochlorite is an alkaline inorganic chemical compound with the formula NaOCl. It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. It is the sodium salt of hypochlorous acid, consisting of sodium cations and hypochlorite anions.

<span class="mw-page-title-main">Chlorine dioxide</span> Chemical compound

Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually handled as an aqueous solution. It is commonly used as a bleach. More recent developments have extended its applications in food processing and as a disinfectant.

<span class="mw-page-title-main">Hypochlorous acid</span> Chemical compound

Hypochlorous acid is an inorganic compound with the chemical formula ClOH, also written as HClO, HOCl, or ClHO. Its structure is H−O−Cl. It is an acid that forms when chlorine dissolves in water, and itself partially dissociates, forming hypochlorite anion, ClO. HClO and ClO are oxidizers, and the primary disinfection agents of chlorine solutions. HClO cannot be isolated from these solutions due to rapid equilibration with its precursor, chlorine.

<span class="mw-page-title-main">Hypochlorite</span> Ion

In chemistry, hypochlorite, or chloroxide is an anion with the chemical formula ClO. It combines with a number of cations to form hypochlorite salts. Common examples include sodium hypochlorite and calcium hypochlorite. The Cl-O distance in ClO is 1.69 Å.

The chloralkali process is an industrial process for the electrolysis of sodium chloride (NaCl) solutions. It is the technology used to produce chlorine and sodium hydroxide, which are commodity chemicals required by industry. Thirty five million tons of chlorine were prepared by this process in 1987. The chlorine and sodium hydroxide produced in this process are widely used in the chemical industry.

<span class="mw-page-title-main">Piperonal</span> Chemical compound

Piperonal, also known as heliotropin, is an organic compound which is commonly found in fragrances and flavors. The molecule is structurally related to other aromatic aldehydes such as benzaldehyde and vanillin.

An alpha hydroxy carboxylic acid or α-hydroxy carboxylic acid (AHA) is a carboxylic acid containing a hydroxy functional group separated by one carbon atoms. They are related to beta hydroxy acids, in which the two functional groups are separated by two carbon atoms. Prominent examples are glycolic acid, lactic acid, mandelic acid, and citric acid.

Salt water chlorination is a process that uses dissolved salt for the chlorination of swimming pools and hot tubs. The chlorine generator uses electrolysis in the presence of dissolved salt to produce chlorine gas or its dissolved forms, hypochlorous acid and sodium hypochlorite, which are already commonly used as sanitizing agents in pools. Hydrogen is produced as byproduct too.

Monochloramine, often called chloramine, is the chemical compound with the formula NH2Cl. Together with dichloramine (NHCl2) and nitrogen trichloride (NCl3), it is one of the three chloramines of ammonia. It is a colorless liquid at its melting point of −66 °C (−87 °F), but it is usually handled as a dilute aqueous solution, in which form it is sometimes used as a disinfectant. Chloramine is too unstable to have its boiling point measured.

Chloramines refer to derivatives of ammonia and organic amines wherein one or more N−H bonds have been replaced by N−Cl bonds. Two classes of compounds are considered: inorganic chloramines and organic chloramines. Chloramines are the most widely used members of the halamines.

Calcium chlorate is the calcium salt of chloric acid, with the chemical formula Ca(ClO3)2. Like other chlorates, it is a strong oxidizer.

<span class="mw-page-title-main">Bleach</span> Chemicals used to whiten or disinfect

Bleach is the generic name for any chemical product that is used industrially or domestically to remove colour (whitening) from fabric or fiber or to disinfect after cleaning. It often refers specifically to a dilute solution of sodium hypochlorite, also called "liquid bleach".

<span class="mw-page-title-main">Haloform reaction</span> Chemical reaction involving repeated halogenation of an acetyl group (–COCH3)

In chemistry, the haloform reaction is a chemical reaction in which a haloform is produced by the exhaustive halogenation of an acetyl group, in the presence of a base. The reaction can be used to transform acetyl groups into carboxyl groups or to produce chloroform, bromoform, or iodoform. Note that fluoroform can't be prepared in this way.

Electrochlorination is the process of producing hypochlorite by passing electric current through salt water. This disinfects the water and makes it safe for human use, such as for drinking water or swimming pools.

<span class="mw-page-title-main">Water chlorination</span> Chorination of water

Water chlorination is the process of adding chlorine or chlorine compounds such as sodium hypochlorite to water. This method is used to kill bacteria, viruses and other microbes in water. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera, dysentery, and typhoid.

Potassium hypochlorite is a chemical compound with the chemical formula KOCl, also written as KClO. It is the potassium salt of hypochlorous acid. It consists of potassium cations and hypochlorite anions. It is used in variable concentrations, often diluted in water solution. Its aqueous solutions are colorless liquids that have a strong chlorine smell. It is used as a biocide and disinfectant.

A mixed oxidant solution (MOS) is a type of disinfectant that has many uses including disinfecting, sterilizing, and eliminating pathogenic microorganisms in water. An MOS may have advantages such as a higher disinfecting power, stable residual chlorine in water, elimination of biofilm, and safety. The main components of an MOS are chlorine and its derivatives, which are produced by electrolysis of sodium chloride. It may also contain high amounts of hydroxy radicals, chlorine dioxide, dissolved ozone, hydrogen peroxide and oxygen from which the name "mixed oxidant" is derived.

<span class="mw-page-title-main">Chlorine-releasing compounds</span>

Chlorine-releasing compounds, also known as chlorine base compounds, is jargon to describe certain chlorine-containing substances that are used as disinfectants and bleaches. They include the following chemicals: sodium hypochlorite, chloramine, halazone, and sodium dichloroisocyanurate. They are widely used to disinfect water and medical equipment, and surface areas as well as bleaching materials such as cloth. The presence of organic matter can make them less effective as disinfectants. They come as a liquid solution, or as a powder that is mixed with water before use.

References

  1. also chlorine powder, chloride of lime, chlorinated lime, "dry chlorine"
  1. Gerald F. Connell. "Key operating strategies for chlorine disinfection operating systems" (PDF). Retrieved 19 October 2014.
  2. 1 2 "Calcium Hypochlorite - 3V Tech". www.3v-tech.com.
  3. 1 2 3 Vogt, H.; Balej, J; Bennett, J. E.; Wintzer, P.; Sheikh, S. A.; Gallone, P.; Vasudevan, S.; Pelin, K. (2010). "Chlorine Oxides and Chlorine Oxygen Acids". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a06_483.pub2. ISBN   978-3527306732. S2CID   96905077.
  4. "Calcium hypochlorite". Chemistry World.
  5. Chemical Products Synopsis: Calcium Hypochlorite (Technical report). Asbuiy Park, NJ: Mannsvile Chemical Products. 1987.
  6. 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.
  7. 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.
  8. Cohen, Julius (1900). Practical Organic Chemistry for Advanced Students. New York: Macmillan & Co. p. 63.
  9. 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.
  10. "8.41799 Calcium hypochlorite for synthesis". Sigma-Aldrich. Assay (iodometric): 67.0 - 75.0 %
  11. 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
  12. 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.{{cite journal}}: CS1 maint: multiple names: authors list (link)