Calcium phosphate is a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. They are white solids of nutritious value. Calcium phosphates are found in many living organisms, e.g., bone mineral and tooth enamel. In milk, it exists in a colloidal form in micelles bound to casein protein with magnesium, zinc, and citrate - collectively referred to as colloidal calcium phosphate (CCP). Various calcium phosphate minerals are used in the production of phosphoric acid and fertilizers. Overuse of certain forms of calcium phosphate can lead to nutrient-containing surface runoff and subsequent adverse effects upon receiving waters such as algal blooms and eutrophication.
Orthophosphates, di- and monohydrogen phosphates
These materials contain Ca2+ combined with PO43−,H2PO4− , and/or HPO42−:
- 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) and a dihydrate CaHPO4(H2O)2 (mineral: brushite)
- 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, a glassy precipitate of variable composition that may be present in biological systems.
Di- and polyphosphates
- 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 Ca5(PO4)3(OH)
- Apatite Ca10(PO4)6(OH, F, Cl, Br)2
- Tetracalcium phosphate (CAS#1306-01-0): Ca4(PO4)2O
- Klaus Schrödter; Gerhard Bettermann; Thomas Staffel; Friedrich Wahl; Thomas Klein; Thomas Hofmann (2008). Phosphoric Acid and Phosphates. Ullmann’s Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_465.pub3.
- A. Y. Tamime, ed. (2006). Brined cheeses - The Society of Dairy Technology (SDT). Wiley-Blackwell. ISBN 978-1-4051-2460-7.