Monocalcium phosphate is aninorganic compound with thechemical formula Ca(H₂PO₄)₂ ("AMCP" or "CMP-A" for anhydrous monocalcium phosphate). It is commonly found as themonohydrate ("MCP" or "MCP-M"), Ca(H₂PO₄)₂·H₂O. Both salts are colourless solids. They are used mainly assuperphosphate fertilizers and are also popularleavening agents.^[1]

Monocalcium phosphate

Names
IUPAC name Calcium bis(dihydrogen phosphate)
Other names Acid calcium phosphate Calcium acid phosphate Calcium diorthophosphate Calcium biphosphate Calcium superphosphate Monobasic calcium phosphate Monocalcium orthophosphate Phosphoric acid, calcium salt (2:1)
Identifiers
CAS Number	7758-23-8 Y 10031-30-8 (monohydrate) Y
3D model (JSmol)	Interactive image
ChemSpider	22862 N
ECHA InfoCard	100.028.943
E number	E341(i)(antioxidants, ...)
PubChemCID	24454
UNII	701EKV9RMN Y 0N4E6L5449 (monohydrate) Y
CompTox Dashboard(EPA)	DTXSID2044262
InChI InChI=1S/Ca.2H3O4P/c;2*1-5(2,3)4/h;2*(H3,1,2,3,4)/q+2;;/p-2 N Key: YYRMJZQKEFZXMX-UHFFFAOYSA-L N InChI=1/Ca.2H3O4P/c;2*1-5(2,3)4/h;2*(H3,1,2,3,4)/q+2;;/p-2 Key: YYRMJZQKEFZXMX-NUQVWONBAY
SMILES OP(=O)(O)[O-].OP(=O)(O)[O-].[Ca+2]
Properties
Chemical formula	CaH4P2O8
Molar mass	234.05 g/mol
Appearance	White powder
Density	2.220 g/cm3
Melting point	109 °C (228 °F; 382 K)
Boiling point	203 °C (397 °F; 476 K) (decomposes)
Solubility in water	2 g/100 mL
Refractive index (nD)	1.5176
Structure
Crystal structure	Triclinic
Hazards
NFPA 704 (fire diamond)	1 0 0
Flash point	Non-flammable
Related compounds
Otheranions	Calcium pyrophosphate
Othercations	Magnesium phosphate Dicalcium phosphate Tricalcium phosphate Strontium phosphate
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Material of relatively high purity, as required for baking, is produced by treating calcium hydroxide withphosphoric acid:

Samples of Ca(H₂PO₄)₂ tend to convert todicalcium phosphate:

Superphosphate fertilizers are produced by treatment of "phosphate rock" with acids ("acidulation"). Usingphosphoric acid,fluorapatite is converted to Ca(H₂PO₄)₂:

This solid is calledtriple superphosphate. Several million tons are produced annually for use asfertilizers. Usingsulfuric acid,fluorapatite is converted to a mixture of Ca(H₂PO₄)₂ and CaSO₄.This solid is calledsingle superphosphate.

Residual HF typically reacts with silicate minerals co-mingled with the phosphate ores to producehexafluorosilicic acid (H₂SiF₆). The majority of the hexafluorosilicic acid is converted toaluminium fluoride andcryolite for the processing of aluminium.^[1] These materials are central to the conversion of aluminium ore intoaluminium metal.

Whensulfuric acid is used, the product containsphosphogypsum (CaSO₄·2H₂O) and is called single superphosphate.^[2]

Calcium dihydrogen phosphate is used in the food industry as aleavening agent, i.e., to cause baked goods to rise. Because it is acidic, when combined with an alkali carbonate ingredient, commonlysodium bicarbonate (baking soda) orpotassium bicarbonate, it reacts to producecarbon dioxide and asalt. Outward pressure of the carbon dioxide gas causes the rising effect. When combined in a ready-madebaking powder, the acid and alkali ingredients are included in the right proportions such that they will exactly neutralize each other and not significantly affect the overallpH of the product. AMCP and MCP are fast acting, releasing most carbon dioxide within minutes of mixing. It is popularly used inpancake mixes. In double-acting baking powders, MCP is often combined with the slow-acting acidsodium acid pyrophosphate (SAPP).^[3]

• Dicalcium phosphate
• Triple superphosphate

• Havlin, J.L., J.D. Beaton, S.L. Tisdale, and W.L. Nelson. 2005.Soil Fertility and Fertilizers. 7th edn. Pearson Prentice Hall, N.J.,ISBN 0130278246