Calcium hypochlorite is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

, also written as . It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow

decomposition Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ess ...

in moist air. This compound is relatively stable as a solid and solution and has greater available

chlorine Chlorine is a chemical element; it has Symbol (chemistry), 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 ...

than

sodium hypochlorite Sodium hypochlorite is an alkaline inorganic chemical compound with the formula (also written as NaClO). It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. It is the sodium salt of hypochlorous acid, consisting of ...

. "Pure" samples have 99.2% active chlorine. Given common industrial purity, an active chlorine content of 65-70% is typical. It is the main active ingredient of commercial products called bleaching powder, used for

water treatment Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, ...

and as a bleaching agent.

History

Charles Tennant Charles Tennant (3 May 1768 – 1 October 1838) was a Scottish chemist and industrialist. He discovered Calcium hypochlorite, bleaching powder and founded an industrial dynasty. Biography Charles Tennant was born at Laigh Corton, Alloway, Ayrs ...

and

Charles Macintosh Charles Macintosh FRS (29 December 1766 – 25 July 1843) was a Scottish chemist and the inventor of the modern waterproof raincoat. The Mackintosh raincoat (the variant spelling is now standard) is named after him. Biography Macintosh was ...

developed an industrial process in the late 18th century for the manufacture of chloride of lime, patenting it in 1799. Tennant's process is essentially still used today, and became of military importance during

World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

, because calcium hypochlorite was the active ingredient in

trench A trench is a type of digging, excavation or depression in the ground that is generally deeper than it is wide (as opposed to a swale (landform), swale or a bar ditch), and narrow compared with its length (as opposed to a simple hole or trapping ...

disinfectant.

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, but due to calcium residue (making the water harder),

(bleach) is usually preferred.

Organic chemistry

Calcium hypochlorite is a general

oxidizing agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...

and therefore finds some use in

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...

. For instance the compound is used to

cleave Cleave may refer to: * Cleave (surname) * Cleave (fiber), a controlled break in optical fiber * RAF Cleave, was an airfield in the north of Cornwall, England, May 1939 - Nov 1945 *The process of protein cleaving as a form of post-translational mod ...

glycol A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol may also be called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. They are used as protecting gro ...

s, α-hydroxy carboxylic acids and

keto acid In organic chemistry, keto acids or ketoacids (also called oxo acids or oxoacids) are organic compounds that contain a carboxylic acid group () and a ketone group ().Franz Dietrich Klingler, Wolfgang Ebertz "Oxocarboxylic Acids" in Ullmann's En ...

s to yield fragmented

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

s or

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

s. Calcium hypochlorite can also be used in the haloform reaction to manufacture

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

. Calcium hypochlorite can be used to oxidize

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

and

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

byproducts in organic synthesis and thereby reduce their odour and make them safe to dispose of. The reagent used in organic chemistry is similar to the sanitizer at ~70% purity.

Production

Calcium hypochlorite is produced industrially by reaction of moist slaked

calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime ( calcium oxide) is mixed with water. Annually, approxim ...

with

gas. The one-step reaction is shown below: : 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 Calcium chloride is an inorganic compound, a Salt (chemistry), salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with cal ...

. In one process, the chloride-rich first stage water is discarded, while the solid precipitate is dissolved in a mixture of water and

lye Lye is the common name of various alkaline solutions, including soda lye (a solution of sodium hydroxide) and potash lye (a solution of potassium hydroxide). Lyes are used as cleaning products, as ingredients in soapmaking, and in various other c ...

for another round of chlorination to reach the target purity. Commercial calcium hypochlorite consists of anhydrous , dibasic calcium hypochlorite (also written as ), and dibasic calcium chloride (also written as ).

Reactions

Calcium hypochlorite reacts rapidly with acids producing

, chlorine gas, and water: :

Safety

It is a strong

, as it contains a

hypochlorite In chemistry, hypochlorite, or chloroxide is an oxyanion with the chemical formula ClO−. It combines with a number of cations to form hypochlorite salts. Common examples include sodium hypochlorite (household bleach) and calcium 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

External links

Chemical Land
{{Hypochlorites Antiseptics Bleaches Hypochlorites Calcium compounds Oxidizing agents Household chemicals