Calcium phosphate

For the function of calcium phosphate in organisms, see Calcium metabolism.

The term calcium phosphate refers to 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. Calcium phosphates are white solids of nutritional value^[2] and are found in many living organisms, e.g., bone mineral and tooth enamel.^[3] 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).^[4] 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 (over-enrichment with nutrients and minerals).^[5]

Calcium phosphate

Calcium Phosphate nanowires seen in SEM
Identifiers
CAS Number	7758-87-4
EC Number	233-283-6
E number	E341 (antioxidants, ...)
PubChem CID	24456
UNII	K4C08XP666
InChI Key: QORWJWZARLRLPR-UHFFFAOYSA-H
Properties
Chemical formula	Ca3(PO4)2
Molar mass	310.18 g/mol
Appearance	White Solid
Odor	Odorless
Density	3.14 g/cu cm[1]
Melting point	1,670 °C (3,040 °F; 1,940 K)[1]
Solubility in water	Practically insoluble with water
Solubility in Ethanol	Insoluble with ethanol (also acetic acid)
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P101, P102, P103, P261, P264, P270, P271, P280, P302+P352, P304+P340, P305+P351+P338
NFPA 704 (fire diamond)	2 0 1
Flash point	Non-flammable
Safety data sheet (SDS)	fishersci.com
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Orthophosphates, di- and monohydrogen phosphates

These materials contain Ca²⁺ combined with PO³⁻
₄, HPO²⁻
₄, or H
₂PO⁻
₄:

• 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, a glassy precipitate of variable composition that may be present in biological systems.

Di- and polyphosphates

These materials contain Ca²⁺ combined with the polyphosphates, such as P
₂O⁴⁻
₇ and triphosphate P
₃O⁵⁻
₁₀:

• 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

Clinical significance

Calcium phosphate stones account for approximately 15% of kidney stone disease. Calcium phosphate stones tend to grow in alkaline urine, especially when Proteus bacteria are present. It is the most common type in pregnant women.^[6]

Calcium phosphate is the usual constitution of microcalcifications of the breast, particularly dystrophic calcifications. Microcalcifications as can be seen on mammography can be an early sign of breast cancer. Based on morphology, it is possible to classify by radiography how likely microcalcifications are to indicate cancer.^[7]

• 
  Urine crystals comparison, with calcium phosphate crystal depicted at top center.
• 
  Histopathology of dystrophic calcium phosphate microcalcifications in ductal carcinoma in situ (DCIS) of the breast, H&E stain.

References

1. "Calcium Phosphate".
2. Klaus Schrödter; Gerhard Bettermann; Thomas Staffel; Friedrich Wahl; Thomas Klein; Thomas Hofmann (2008). "Phosphoric Acid and Phosphates". Ullmann's Encyclopedia of Industrial Chemistry. Ullmann’s Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_465.pub3. ISBN 978-3527306732. S2CID 94458523.
3. "What Substances Make Up Your Teeth? – Affordable Dental Care". www.towncaredental.com. 2015-07-15. Retrieved 2021-01-29.
4. A. Y. Tamime, ed. (2006). Brined cheeses - The Society of Dairy Technology (SDT). Wiley-Blackwell. ISBN 978-1-4051-2460-7.
5. Xiao, Zhengyang; Tan, Albern X.; Xu, Vincent; Jun, Young-Shin; Tang, Yinjie J. (2022). "Mineral-hydrogel composites for mitigating harmful algal bloom and supplying phosphorous for photo-biorefineries". Science of the Total Environment. 847: 157533. Bibcode:2022ScTEn.84757533X. doi:10.1016/j.scitotenv.2022.157533. PMC 9755271. PMID 35878849.
6. Frassetto L, Kohlstadt I (2011). "Treatment and prevention of kidney stones: an update". Am Fam Physician. 84 (11): 1234–42. PMID 22150656.
7. Nalawade, Yojana V (November 2009). "Evaluation of breast calcifications". The Indian Journal of Radiology & Imaging. 19 (4): 282–286. doi:10.4103/0971-3026.57208. ISSN 0971-3026. PMC 2797739. PMID 19881103.