Calcium phosphate

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Structural formula
3 Calcium ion 2 Phosphate ion
Surname Calcium phosphate
other names
  • Tricalcium phosphate
  • Tribasic calcium phosphate
  • Calcium orthophosphate
  • Tricalcium monophosphate
  • Tertiary calcium phosphate
Molecular formula Ca 3 (PO 4 ) 2
Brief description

white, odorless solid

External identifiers / databases
CAS number 7758-87-4
EC number 231-840-8
ECHA InfoCard 100,028,946
PubChem 24456
Wikidata Q278387
Drug information
ATC code

A12 AA01

Molar mass 310.18 g mol −1
Physical state



3.14 g cm −3

Melting point

1670 ° C


practically insoluble in water (0.02 g l −1 at 20 ° C)

safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
Toxicological data

> 5000 mg kg −1 ( LD 50ratoral )

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Calcium phosphate , tricalcium orthophosphate or tricalcium phosphate (Ca 3 (PO 4 ) 2 ) is a calcium salt of orthophosphoric acid and belongs to the phosphates . The term tricalcium phosphate is occasionally used for the very similar compound pentacalcium hydroxy triphosphate (Ca 5 (PO 4 ) 3 · OH) (= hydroxyapatite ).


Calcium phosphate does not occur in its pure form in nature. Calcium phosphate minerals such as apatite or whitlockite always contain other cations (e.g. sodium , magnesium or iron ) and anions ( hydroxide , carbonate , fluoride or chloride ). By far the most common and economically most important calcium phosphate mineral is apatite. Abiogenic apatite is an accessory component of numerous igneous rocks and the main component of the marine rock phosphorite . More than 80% of the world's apatite extraction comes from phosphorite deposits.

Apatite is also formed by or in living beings: the mineral substance of the bones and teeth of vertebrates therefore mainly consists of hydroxyapatite. In ivory , the total proportion is 55 to 61%. In addition, guano , a biogenic “sediment” made from animal excrement, contains small amounts of apatite. Biogenic calcium phosphate is an important source of phosphate for what is known as phosphogenesis , a step in the formation of phosphorites.


Calcium phosphate is a white and odorless solid that melts at 1670 ° C. It is practically insoluble in water.


The (water-insoluble) tertiary calcium phosphate is used to produce the (water-soluble) primary calcium phosphate Ca (H 2 PO 4 ) 2 , a widely used fertilizer, better known as superphosphate .

Calcium phosphate is also used to make phosphoric acid by allowing it to react with sulfuric acid :

In food technology, calcium phosphate is used as an acid regulator , setting agent or release agent; For example, for ready-to-use cake mixes, where it acts as a trickle aid to prevent the formation of lumps and to maintain the flowability. Calcium phosphate, together with calcium dihydrogen phosphate and calcium hydrogen phosphate, is approved in the EU as a food additive under the common number E 341 ("calcium phosphate") for certain foods with different maximum quantity restrictions, also for organic foods . According to the Additive Admissions Ordinance , these are - largely uniform for most of the approved phosphates - individual specifications for a wide range of numerous different types of food. The maximum permitted amounts vary from 0.5 to 50 grams per kilogram (in creamer for vending machines) or the lack of a fixed limit ( quantum satis - as required, for food supplements and sometimes for chewing gum). Phosphorus is suspected of causing hyperactivity , allergic reactions and osteoporosis . A permissible daily dose of 70 milligrams per kilogram of body weight was set for the total amount of phosphoric acid and phosphates ingested.

Tricalcium phosphate is used as a synthetic bone substitute material in bone surgery and implantology ; it is slowly reabsorbed and replaced by own bone.

Adjuvants in vaccines

Calcium phosphates were used as adjuvants in vaccines ( DTP and polio ) until the 1980s . However, calcium phosphate was not present as a salt itself, but rather non-stoichiometric forms of hydroxyapatite such as Ca 10 (PO 4 ) 6 (OH) 2 or Ca 9 (HPO 4 ) (PO 4 ) 5 (OH), all of which have the same C / P ratio like calcium phosphate. The OH group is helpful for surface charge and for the absorption of antigens.

See also

Web links

Individual evidence

  1. Entry on TRICALCIUM PHOSPHATE in the CosIng database of the EU Commission, accessed on March 21, 2020.
  2. a b c d e f Entry on calcium phosphate in the GESTIS substance database of the IFA , accessed on December 10, 2012 (JavaScript required)
  3. Data sheet calcium phosphate (PDF) from Merck , accessed on January 19, 2011.
  4. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 91st – 100th, improved and greatly expanded edition. Walter de Gruyter, Berlin 1985, ISBN 3-11-007511-3 , p. 655.
  5. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements . VCH 1988, pp. 611, 675.
  6. Steven J. Van Kauwenbergh: World Phosphate Rock Reserves and Resources. International Fertilizer Development Center Technical Bulletin. No. 75, p. 2 f. ( PDF 2.6 MB).
  7. Gabriel M. Filippelli: Phosphate rock formation and marine phosphorus geochemistry: The deep time perspective. Chemosphere. Vol. 84, No. 6 (special edition The Phosphorous Cycle ), 2011, pp. 759–766, doi : 10.1016 / j.chemosphere.2011.02.019
  8. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements . VCH 1988, p. 675.
  9. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 91st – 100th, improved and greatly expanded edition. Walter de Gruyter, Berlin 1985, ISBN 3-11-007511-3 , p. 652.
  10. Kari Köster, Eberhard Karbe, Horst Kramer, Helmut Heide, Rainer König: Experimental bone replacement through resorbable calcium phosphate ceramic. In: Langenbeck's archive for surgery . 1976, Vol. 341, No. 2, pp. 77-86, doi : 10.1007 / BF01262779
  11. ^ Jean-Daniel Masson et al .: Calcium phosphate: a substitute for aluminum adjuvants? In: Expert Review of Vaccines . tape 16 , no. 3 , March 2017, p. 289-299 , doi : 10.1080 / 14760584.2017.1244484 , PMID 27690701 .