Calcium pyrophosphate: Difference between revisions
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m Fixed stoichiometry of a chemical reaction. Na<sub>2</sub>NO<sub>3</sub> isn’t a thing, and even if it was, there would still be two nitrate ions unaccounted for. Also added more wikilinks. |
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==Preparation== |
==Preparation== |
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Crystals of the tetrahydrate can be prepared by reacting [[sodium pyrophosphate]], Na<sub>4</sub>P<sub>2</sub>O<sub>7</sub> with [[calcium nitrate]], Ca(NO<sub>3</sub>)<sub>2</sub>, at carefully controlled pH and temperature:<ref name="Christofferson" /> |
Crystals of the tetrahydrate can be prepared by reacting [[sodium pyrophosphate]], Na<sub>4</sub>P<sub>2</sub>O<sub>7</sub> with [[calcium nitrate]], Ca(NO<sub>3</sub>)<sub>2</sub>, at carefully controlled pH and temperature:<ref name="Christofferson" /> |
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:Na<sub>4</sub>P<sub>2</sub>O<sub>7</sub>(aq) |
:Na<sub>4</sub>P<sub>2</sub>O<sub>7</sub>(aq)+2 Ca(NO<sub>3</sub>)<sub>2</sub>(aq)→ Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>·4 H<sub>2</sub>O + 4 NaNO<sub>3</sub> |
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The dihydrate, sometimes termed CPPD, can be formed by the reaction of [[pyrophosphoric acid]] with [[calcium chloride]]:<ref name="ROPPchapter4" /> |
The dihydrate, sometimes termed CPPD, can be formed by the reaction of [[pyrophosphoric acid]] with [[calcium chloride]]:<ref name="ROPPchapter4" /> |
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:CaCl<sub>2</sub> + H<sub>4</sub>P<sub>2</sub>O<sub>7</sub>(aq) → Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>·2 H<sub>2</sub>O + HCl. |
:CaCl<sub>2</sub> + H<sub>4</sub>P<sub>2</sub>O<sub>7</sub>(aq) → Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>·2 H<sub>2</sub>O + HCl. |
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The anhydrous forms can be prepared by heating dicalcium phosphate:<ref name="ROPPchapter4" /> |
The anhydrous forms can be prepared by heating [[dicalcium phosphate]]:<ref name="ROPPchapter4" /> |
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:2 CaHPO<sub>4</sub> → Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub> + H<sub>2</sub>O |
:2 CaHPO<sub>4</sub> → Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub> + H<sub>2</sub>O |
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At 240-500 °C an amorphous phase is formed, heating to 750 °C forms β-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>, heating to 1140 - 1350 °C forms the α-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>. |
At 240-500 °C an amorphous phase is formed, heating to 750 °C forms β-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>, heating to 1140 - 1350 °C forms the α-Ca<sub>2</sub>P<sub>2</sub>O<sub>7</sub>. |
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Revision as of 20:51, 20 August 2019
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| Names | |
|---|---|
| IUPAC name
Calcium diphosphate
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| Other names
Diphosphoric acid, calcium salt (1:2); Dicalcium diphosphate; Dicalcium pyrophosphate
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| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.029.292 |
| E number | E450(vi) (thickeners, ...) |
| MeSH | Calcium+pyrophosphate |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| Ca2O7P2 | |
| Molar mass | 254.053 g/mol |
| Appearance | White powder |
| Density | 3.09 g/cm3 |
| Melting point | 1,353 °C (2,467 °F; 1,626 K) |
| insoluble | |
| Solubility | soluble in HCl, nitric acids |
Refractive index (nD)
|
1.585 |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Related compounds | |
Other anions
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Calcium phosphate |
Other cations
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Magnesium pyrophosphate Sodium pyrophosphate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Calcium pyrophosphate (Ca2P2O7) is a chemical compound, an insoluble calcium salt containing the pyrophosphate anion. There are a number of forms reported: an anhydrous form, a dihydrate, Ca2P2O7·2H2O and a tetrahydrate, Ca2P2O7·4H2O. Deposition of dihydrate crystals in cartilage are responsible for the severe joint pain in cases of calcium pyrophosphate deposition disease (pseudo gout) whose symptoms are similar to those of gout.[1] Ca2P2O7 is commonly used as a mild abrasive agent in toothpastes.[2]
Preparation
Crystals of the tetrahydrate can be prepared by reacting sodium pyrophosphate, Na4P2O7 with calcium nitrate, Ca(NO3)2, at carefully controlled pH and temperature:[3]
- Na4P2O7(aq)+2 Ca(NO3)2(aq)→ Ca2P2O7·4 H2O + 4 NaNO3
The dihydrate, sometimes termed CPPD, can be formed by the reaction of pyrophosphoric acid with calcium chloride:[2]
- CaCl2 + H4P2O7(aq) → Ca2P2O7·2 H2O + HCl.
The anhydrous forms can be prepared by heating dicalcium phosphate:[2]
- 2 CaHPO4 → Ca2P2O7 + H2O
At 240-500 °C an amorphous phase is formed, heating to 750 °C forms β-Ca2P2O7, heating to 1140 - 1350 °C forms the α-Ca2P2O7.
Structure of anhydrous and hydrated forms
The stable tetrahydrate was originally reported to be rhombohedral but is now believed to be monoclinic. Additionally there is an unstable monoclinic form.[3]
The dihydrate is triclinic, with hydrogen bonding between the two water molecules and hydrogen bonds to the O atoms on the anion.[2] An hexagonal dihydrate has also been reported.[4]
The anhydrous form has 3 polymorphs, α-, β-, and a metastable γ. The high temperature form α- is monoclinic, with 8 coordinate calcium, the lower temperature form β- is tetragonal, with calcium in four different coordination environments, 2 that are 7 coordinate, one eight and one 9. In both the pyrophosphates are essentially eclipsed.[5][6]
References
- ^ Calcium Pyrophosphate Deposition Disease at eMedicine
- ^ a b c d Ropp, R.C. (2013). "Group 15 (N, P, As, Sb and Bi) Alkaline Earth Compounds". Encyclopedia of the Alkaline Earth Compounds. pp. 199–350. doi:10.1016/B978-0-444-59550-8.00004-1. ISBN 978-0-444-59550-8.
- ^ a b Christoffersen, Margaret R.; Balic-Zunic, Tonci; Pehrson, Søren; Christoffersen, Jørgen (2000). "Growth and precipitation of a monoclinic calcium pyrophosphate tetrahydrate indicating auto-inhibition at pH7". Journal of Crystal Growth. 212 (3–4): 500–506. Bibcode:2000JCrGr.212..500C. doi:10.1016/S0022-0248(00)00231-1.
- ^ Mandel, Gretchen S.; Renne, Kathleen M.; Kolbach, Ann M.; Kaplan, Wayne D.; Miller, Jay D.; Mandel, Neil S. (1988). "Calcium pyrophosphate crystal deposition disease: Preparation and characterization of crystals". Journal of Crystal Growth. 87 (4): 453–462. Bibcode:1988JCrGr..87..453M. doi:10.1016/0022-0248(88)90093-0.
- ^ Parodi, J. A.; Hickok, R. L.; Segelken, W. G.; Cooper, J. R. (1965). "Electronic Paramagnetic Resonance Study of the Thermal Decomposition of Dibasic Calcium Orthophosphate". Journal of the Electrochemical Society. 112 (7): 688. doi:10.1149/1.2423665.
- ^ Webb, N. C. (1966). "The crystal structure of β-Ca2P2O". Acta Crystallographica. 21 (6): 942–948. doi:10.1107/S0365110X66004225.