Calcium phosphate
Calcium phosphate is the name given to a family of mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

s containing calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s (Ca2+) together with orthophosphates (PO43-), metaphosphate
A metaphosphate ion is an oxyanion that has the empirical formula PO3−. The structure of a metaphosphate ion can be described as being made up of PO4 structural units in which each unit shares two corners with another unit...

s or pyrophosphate
In chemistry, the anion, the salts, and the esters of pyrophosphoric acid are called pyrophosphates. Any salt or ester containing two phosphate groups is called a diphosphate. As a food additive, diphosphates are known as E450.- Chemistry :...

s (P2O74-) and occasionally hydrogen
Hydrogen ion
Hydrogen ion is recommended by IUPAC as a general term for all ions of hydrogen and its isotopes.Depending on the charge of the ion, two different classes can be distinguished: positively charged ions and negatively charged ions....

 or hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...

 ions .

It is the principal form of calcium found in bovine milk. Seventy percent of bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

 is made up of hydroxyapatite, a calcium phosphate mineral (known as bone mineral
Bone mineral
Bone mineral is the inorganic component of bone. Bone mineral is formed from carbonated hydroxyapatite with lower crystallinity....

). Tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

 is composed of almost ninety percent hydroxyapatite.

Chemical Properties

Unlike most other compounds calcium phosphate is increasingly insoluble at higher temperatures. Thus heating causes precipitation.

In milk it is found in higher concentrations than would be possible at the normal pH because it exists in a colloidal form in micelles bound to casein
Casein is the name for a family of related phosphoprotein proteins . These proteins are commonly found in mammalian milk, making up 80% of the proteins in cow milk and between 60% and 65% of the proteins in human milk....

 protein with magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

, zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 and citrate
A citrate can refer either to the conjugate base of citric acid, , or to the esters of citric acid. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate.-Other citric acid ions:...

 - collectively referred to as colloidal calcium phosphate (CCP)


It is used in the production of phosphoric acid
Phosphoric acid
Phosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...

 and fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

s, for example in the Odda process
Nitrophosphate process
The nitrophosphate process was a method for the industrial production of nitrogen fertilizers invented by Erling Johnson in the city of Odda, Norway around 1927....

. Overuse of certain forms of calcium phosphate can lead to nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

-containing surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

 and subsequent adverse effects upon receiving waters such as algal bloom
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...

s and eutrophication
Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...


Calcium phosphate is used in baking as a raising agent, with E number
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

 E341. It is also used in cheese products.

Tricalcium phosphate is also used as a nutritional supplement and occurs naturally in cow milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...

, although the most common and economical forms for supplementation are calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 (which should be taken with food) and calcium citrate
Calcium citrate
Calcium citrate is the calcium salt of citric acid. It is commonly used as a food additive , usually as a preservative, but sometimes for flavor. In this sense, it is similar to sodium citrate. Calcium citrate is also used as a water softener because the citrate ions can chelate unwanted metal...

 (which can be taken without food). Hydroxyapatite (e.g. calcium hydrogen phosphate) as a food supplement has not been currently studied well, so its usage as a supplement is discouraged.

It is used in a variety of dental products for remineralization
Remineralisation of teeth
Remineralisation of teeth is a process in which minerals are returned to the molecular structure of the tooth itself. Teeth are porous allowing fluids and demineralisation beneath the surface of the tooth. When demineralised, these pores become larger...

 and as a diluent in some medications where it will give the tablet a grey colour in the absence of additional colouring agents.

Another practical application of the compound is its use in gene transfection
Transfection is the process of deliberately introducing nucleic acids into cells. The term is used notably for non-viral methods in eukaryotic cells...

 of cells. It is not too well understood, but the calcium phosphate precipitate DNA and form a complex that is thought to help the DNA enter the cell.

Calcium phosphates

  • Calcium dihydrogen phosphate
    Calcium dihydrogen phosphate
    Monocalcium phosphate is a chemical compound with the formula Ca2. It is commonly found as the monohydrate, Ca2·H2O.-Fertilizer:Phosphorus is an essential nutrient and therefore is a common component of agricultural fertilizers...

    , E341(i): Ca(H2PO4)2
  • Calcium hydrogen phosphate, E341(ii): CaHPO4
  • Tricalcium phosphate
    Tricalcium phosphate
    Tricalcium phosphate is a calcium salt of phosphoric acid with the chemical formula Ca32. It is also known as tribasic calcium phosphate or "bone ash" ....

     (or tricalcic phosphate), E341(iii): Ca3(PO4)2, sometimes referred to simply as calcium phosphate or calcium orthophosphate
  • Hydroxyapatite Ca5(PO4)3(OH)
  • Apatite
    Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...

     Ca10(PO4)6(OH, F, Cl, Br)2
  • Octacalcium phosphate
    Octacalcium phosphate
    Octacalcium phosphate is a calcium phosphate with a formula Ca8H26.5H2O. OCP may be a precursor in creation of the tooth enamel, dentine and bones in living organisms....


In addition to the above, of the compounds occurring in the CaO-H2O-P4O10 phase diagram, Ca4P2O9 (probably Ca3(PO4)2.CaO) is notable.
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