|IUPAC name||Calcium dihydrogen phosphate|
3D model (JSmol)
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|Molar mass||234.05 g/mol|
|Except where noted otherwise, data are given for|
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references
Calcium dihydrogen phosphate (also called mono-calcium orthophosphate) Ca(H2PO4)2 is a chemical compound. It is commonly found as the dihydrate, Ca(H2PO4)2·H2O, which releases a water molecule before it melts at 109 °C. It decomposes at 203 °C.
Phosphorus is an important nutrient and so is a common component of fertilizers. Phosphate rock, Ca3(PO4)2 is available but is too insoluble to be an efficient fertilizer. Therefore it is frequently converted into the more soluble calcium dihydrogen phosphate, generally by the use of sulfuric acid H2SO4, the result is hydrated to turn the calcium sulfate into the dihydrate gypsum and sold as "superphosphate of lime"
- Ca3(PO4)2 + 4 H2SO4 + 2 H2O → 2 CaSO4·2H2O + Ca(H2PO4)2·H2O
Alternately phosphate rock may be treated with phosphoric acid to produce a purer form of calcium dihydrogen phosphate and is sold as "triple phosphate".
- Ca3(PO4)2 + 4 H3PO4 → 3 Ca(H2PO4)2
Calcium dihydrogen phosphate is also used in the food industry as a leavening agent to cause baked goods to rise. Because it is acidic, when combined with an alkali ingredient – commonly sodium bicarbonate (baking soda) or potassium bicarbonate – it reacts to produce carbon dioxide and a salt. The carbon dioxide gas is what leavens the baked good. When combined in a ready-made baking 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 overall pH of the product.
Apart from acting as leavening agent, it also inhibits microbial activity because of the phosphate ions present in the molecule.