The term calcium phosphate refers to a family of materials and

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s containing

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

ions (Ca²⁺) together with inorganic

phosphate Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...

anions. Some so-called calcium phosphates contain

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

and hydroxide as well. Calcium phosphates are white solids of nutritional value and are found in many living organisms, e.g., bone mineral and

tooth enamel Tooth enamel is one of the four major Tissue (biology), tissues that make up the tooth in humans and many animals, including some species of fish. It makes up the normally visible part of the tooth, covering the Crown (tooth), crown. The other ...

. In milk, it exists in a colloidal form in micelles bound to casein protein with

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

, and citrate–collectively referred to as colloidal calcium phosphate (CCP). Various calcium phosphate minerals, which often are not white owing to impurities, are used in the production of

phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, ...

and fertilizers. Overuse of certain forms of calcium phosphate can lead to

nutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

-containing

surface runoff Surface runoff (also known as overland flow or terrestrial runoff) is the unconfined flow of water over the ground surface, in contrast to ''channel runoff'' (or ''stream flow''). It occurs when excess rainwater, stormwater, meltwater, or other ...

and subsequent adverse effects upon receiving waters such as algal blooms and

eutrophication Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...

(over-enrichment with nutrients and minerals).

Orthophosphates, di- and monohydrogen phosphates

These materials contain Ca²⁺ combined with , , or : * Monocalcium phosphate, E341 (CAS# 7758-23-8 for anhydrous; CAS#10031-30-8 for monohydrate: Ca(H₂PO₄)₂ and Ca(H₂PO₄)₂(H₂O) * Dicalcium phosphate (dibasic calcium phosphate), E341(ii) (CAS# 7757-93-9): CaHPO₄ (mineral: monetite), dihydrate CaHPO₄(H₂O)₂ (mineral: brushite) and monohydrate CaHPO₄(H₂O) * Tricalcium phosphate (tribasic calcium phosphate or tricalcic phosphate, sometimes referred to as calcium phosphate or calcium orthophosphate, whitlockite), E341(iii) (CAS#7758-87-4): Ca₃(PO₄)₂ * Octacalcium phosphate (CAS# 13767-12-9): Ca₈H₂(PO₄)₆·5H₂O * Amorphous calcium phosphate is a glassy precipitate of variable composition that may be present in biological systems.

Di- and polyphosphates

These materials contain Ca²⁺ combined with the

polyphosphate A polyphosphate is a Salt (chemistry), salt or ester of polymeric oxyanions formed from tetrahedral PO4 (phosphate) structural units linked together by sharing oxygen atoms. Polyphosphates can adopt linear or a cyclic (also called, ring) structure ...

s, such as and triphosphate : * Dicalcium diphosphate (CAS#7790-76-3]: Ca₂P₂O₇ * Calcium triphosphate (CAS# 26158-70-3): Ca₅(P₃O₁₀)₂

Hydroxy- and oxo-phosphates

These materials contain other anions in addition to phosphate: *

Hydroxyapatite Hydroxyapatite (International Mineralogical Association, IMA name: hydroxylapatite) (Hap, HAp, or HA) is a naturally occurring mineral form of calcium apatite with the Chemical formula, formula , often written to denote that the Crystal struc ...

Ca₅(PO₄)₃(OH) *

Apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

Ca₁₀(PO₄)₆(OH,F,Cl,Br)₂ * Tetracalcium phosphate (CAS#1306-01-0): Ca₄(PO₄)₂O

Culinary use

Calcium phosphate was approved by the FDA in the USA for use as a white food coloring because of a 2023 petition from Innophos Inc. of Cranbury, New Jersey

Clinical significance

Calcium phosphate stones account for approximately 15% of

kidney stone disease Kidney stone disease (known as nephrolithiasis, renal calculus disease, or urolithiasis) is a crystallopathy and occurs when there are too many minerals in the urine and not enough liquid or hydration. This imbalance causes tiny pieces of cry ...

. Calcium phosphate stones tend to grow in alkaline urine, especially when ''Proteus'' bacteria are present. It is the most common type in pregnant women. Calcium phosphate is the usual constitution of microcalcifications of the

breast The breasts are two prominences located on the upper ventral region of the torso among humans and other primates. Both sexes develop breasts from the same embryology, embryological tissues. The relative size and development of the breasts is ...

, particularly dystrophic calcifications. Microcalcifications as can be seen on mammography can be an early sign of

breast cancer Breast cancer is a cancer that develops from breast tissue. Signs of breast cancer may include a Breast lump, lump in the breast, a change in breast shape, dimpling of the skin, Milk-rejection sign, milk rejection, fluid coming from the nipp ...

. Based on morphology, it is possible to classify by radiography how likely microcalcifications are to indicate cancer. File:Urine crystals comparison.png, Urine crystals comparison, with calcium phosphate crystal depicted at top center. File:Histopathology of dystrophic microcalcifications in ductal carcinoma in situ.jpg, Histopathology of dystrophic calcium phosphate microcalcifications in ductal carcinoma in situ (DCIS) of the breast, H&E stain.

References

{{DEFAULTSORT:Calcium Phosphate Calcium compounds Phosphates Excipients E-number additives