Calcium Phosphate: Formula, Uses and Risks

Calcium phosphate is the name of a group of compounds formed of calcium and different kinds of phosphates. It is the main form of calcium found in cows’ milk, bones, and tooth enamel.

In industry and at home phosphates are mostly used as food additives and as polishing agents in toothpaste, as well as in fertiliser production.

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Monocalcium phosphate Dicalcium phosphate Tricalcium phosphate Hydroxyapatite
Formula Ca(H2PO4)2 CaHPO4 Ca3(PO4)2 Ca5(PO4)3(OH)

CAS: 7758-23-8 calcium diacid phosphate (monocalcium phosphate)

CAS: 7757-93-9 calcium acid phosphate (dicalcium phosphate)

CAS: 7789-77-7 calcium acid phosphate dihydrate (dicalcium phosphate dihydrate)

CAS: 7758-87-4 tricalcium phosphate

CAS: 12167-74-7 hydroxyapatite (durapatite)

2D Structure

 

Monocalcium phosphate
Monocalcium phosphate
Dicalcium phosphate
Dicalcium phosphate
Tricalcium phosphate
Tricalcium phosphate
Hydroxapatite
Hydroxapatite

3D Structure

 

Dicalcium phosphate
Dicalcium phosphate
Monocalcium phosphate
Monocalcium phosphate
Dicalcium phosphate dyhydrate
Dicalcium phosphate dihydrate
Dicalcium phosphate
Dicalcium phosphate
Tricalcium phosphate
Tricalcium phosphate
Tricalcium phosphate
Tricalcium phosphate
Hydroxapatite
Hydroxapatite
Hydroxapatite
Hydroxapatite

 

Characteristics of calcium phosphate

  Monocalcium phosphate Dicalcium phosphate Tricalcium phosphate Hydroxyapatite
Formulas Ca(H2PO4)2 CaHPO4 Ca3(PO4)2 Ca5(PO4)3(OH)
Molecular mass 234.05 g/mol 136.056 g/mol 310.174 g/mol 502.306 g/mol
Boiling point 203°C      
Melting point 109°C Decomposes At high pressure, 1391°C  
Density 2.220 g/cm3 2.929 g/cm3 3.14 g/cm3  
Water solubility 2 g/100ml 0.02 g/100ml 0.002 g/100g  

 

Toxicity

Calcium toxicity is very rare. Prolonged ingestion of alkaline calcium salts can cause metabolic alkalosis and hypercalcaemia. Hypercalcaemia may cause abdominal pain, delirium, and kidney stones.

Uses

Monocalcium phosphate (also known as calcium dihydrogen phosphate, calcium acid phosphate, calcium diorthophosphate, calcium biphosphate, calcium superphosphate, phosphobic acid, monobasic calcium phosphate, monocalcium orthophosphate), Ca(H2PO4)2 – H2O – H2O, is mainly used as a leavening agent in the production of self-raising flower.

Other uses include the mineral enrichment of food; as a stabilizer in dairy products; and as an additive in animal feed to replace dicalcium phosphate. It is also used in plaster casts as a retardant.

Dicalcium phosphate [CAS: 7757-93-9], (also known as calcium hydrogen phosphate, phosphoric acid), CAHPO4, is used in the food industry in the fortification of various products.

It is also used in the pharmaceutical industry as a pelleting and thickening agent.

Dicalcium phosphate in its dihydrate form, and sometimes in its anhydrous salt form, is used as a supplement in animal feed.

The dihydrate is used in toothpastes due to its polishing properties and low abrasivity. It is also used to prevent toothpaste from hardening.

Tricalcium phosphate [CAS: 7758-87-4], (also known as tribasic calcium phosphate, tricalcium bis(phosphate), and bone phosphate of lime), Ca3(PO4)2, is added to various products such as table salt, sugar, and fertilisers, as an anticaking agent.

It is used in toothpastes that contain dicalcium phosphate to adjust its polishing ability. It is also used in the production of luminescent material.

Hydroxyapatite [CAS: 12167-74-7] (also known as duraptite), Ca5(PO4)3OH is found in bones and teeth. It has been used to treat diseases, such as in the prevention and treatment of osteoporosis.

Industrially, it is made through the neutralisation of phosphoric acid with slaked lime before subsequent filtration, drying, and trituration. Commercial tricalcium phosphate consists mainly of hydroxyapatite.

Women who suffer from primary biliary cirrhosis cannot properly absorb calcium, phosphate, or vitamin D, and they experience rapid bone thinning.

The usefulness of hydroxyapatite in such cases has been investigated. It has been found that there is significant growth in bone thickness in patients treated with hydroxyapatite compared with those in the control group (who were not treated with it).

Health

  • Calcium is necessary for many physiological activities, some of which are less obvious than others. It is essential for the normal functioning of organs and body systems, including the muscles, nervous system and cardiac function.
  • Phosphates are important for the normal functioning of the organism as a whole, and are an essential component of teeth and bones. There is evidence, osteoporosis, rickets, osteomalacia, and hyperparathyroidism.
  • Acute calcium poisoning is rare. It is usually only a product of intravenous administration. Symptoms of hypercalcaemia include lethargy, muscle weakness, vomit, nausea, and constipation.
  • Some calcium salts cause gastrointestinal irritation.
  • Skin exposure to caustic calcium salts may cause irritation.
  • Life threatening symptoms are very rare, and these include complications from a change in mental state, to pneumonia and cardiac arrhythmia.
  • Highly concentrated phosphoric acid is corrosive to all tissue it comes into contact with.
  • It can cause severe skin burns at concentrations of 75% or more.
  • Inhalation of fumes may cause eye, nose, throat and respiratory tract irritation. It may also cause coughing.
  • When ingested, it can produce nausea, vomiting, abdominal pain, bloody diarrhoea, acidosis, shock, irritation, or burns of the oropharyngeal mucosa, the oesophagus and stomach.

Safety and risks

The Globally Harmonised System of Classification and Labelling of Chemicals (GHS) is an internationally agreed system, created by the United Nations, and designed to replace the different rules of classification and labelling used in different countries, through the use of a consistent approach.

The hazard classes (and their corresponding chapter in the GHS), the rules of classification and labelling, and the recommendations for monocalcium phosphate are the following (European Chemicals Agency, 2017; United Nations, 2015):

United Nations, 2015, p. 382
United Nations, 2015, p. 382
United Nations, 2015, p. 384
United Nations, 2015, p. 384

The hazard classes (and their corresponding chapter in the GHS), the rules of classification and labelling, and the recommendations for dicalcium phosphate are the following (European Chemicals Agency, 2017; United Nations, 2015):

United Nations, 2015, p.385
United Nations, 2015, p.385
United Nations, 2015, p.371
United Nations, 2015, p.371
United Nations, 2015, p.399
United Nations, 2015, p.399

The hazard classes (and their corresponding chapter in the GHS), the rules of classification and labelling, and the recommendations for dicalcium phosphate are the following (European Chemicals Agency, 2017; United Nations, 2015):

United Nations, 2015, p. 382
United Nations, 2015, p. 382
United Nations, 2015, p. 385
United Nations, 2015, p. 385
United Nations, 2015, p. 395
United Nations, 2015, p. 395

References

  1. ChemIDplus, (2017). 3D structure of 1306-06-5 – Durapatite [USAN] [imagen] chem.nlm.nih.gov.
  2. ChemIDplus, (2017). 3D structure of 7758-87-4 – Calcium phosphate, tribasic [NF]  [imagen] Retrieved from: chem.nlm.nih.gov.
  3. ChemIDplus, (2017). 3D structure of 7758-23-8 – Calcium bis(dihydrogen phosphate) [imagen] Retrieved from: chem.nlm.nih.gov.
  4. ChemIDplus, (2017). 3D structure of 7789-77-7 – Calcium phosphate dihydrate, dibasic [USP:JAN] [imagen] Retrieved from: chem.nlm.nih.gov.
  5. European Chemicals Agency (ECHA). (2017). Summary of Classification and Labelling. Notified classification and labeling. Calcium bis(dihydrogenorthophosphate) 7758-23-8. Retrieved from: echa.europa.eu.
  6. European Chemicals Agency (ECHA). (2017). Summary of Classification and Labelling. Notified classification and labeling. Calcium hydrogenorthophosphate 7757-93-9 Retrieved from: echa.europa.eu.
  7. European Chemicals Agency (ECHA). (2017). Summary of Classification and Labelling. Notified classification and labeling. Calcium hydrogenorthophosphate dihydrate 7789-77-7. Retrieved from: echa.europa.eu.
  8. European Chemicals Agency (ECHA). (2017). Summary of Classification and Labelling. Notified classification and labeling. Pentacalcium hydroxide tris(orthophosphate) 12167-74-7. Retrieved from: echa.europa.eu.
  9. Hazardous Substances Data Bank (HSDB). TOXNET. (2017). Calcium bis(dihydrogen phospate). Retrieved from: toxnet.nlm.nih.gov.
  10. Hazardous Substances Data Bank (HSDB). TOXNET. (2017). Calcium hydrogen phospate. Retrieved from: toxnet.nlm.nih.gov.
  11. Hazardous Substances Data Bank (HSDB). TOXNET. (2017). Hydroxyapatite. Retrieved from: toxnet.nlm.nih.gov.
  12. National Center for Biotechnology Information. PubChem Compound Database.  (2016). Calcium biphosphate. Retrieved from: pubchem.ncbi.nlm.nih.gov.
  13. National Center for Biotechnology Information. PubChem Compound Database.  (2016). Calcium hydrogen phosphate. Retrieved from: pubchem.ncbi.nlm.nih.gov.
  14. National Center for Biotechnology Information. PubChem Compound Database (2016). calcium hydrogenphosphate dihydrate. Retrieved from: pubchem.ncbi.nlm.nih.gov.
  15. National Center for Biotechnology Information. PubChem Compound Database.  (2016). Compound Summary for CID 516943. Retrieved from pubchem.ncbi.nlm.nih.gov.
  16. National Center for Biotechnology Information. PubChem Compound Database.  (2016). Durapatite. Retrieved from: pubchem.ncbi.nlm.nih.gov.
  17. Schrödter, K., Bettermann, G., Staffel, T., Wahl, F., Klein, T., & Hofmann, T. (2000). Phosphoric Acid and Phosphates. En Ullmann’s Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA. Retrieved from dx.doi.org.

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