Monocalcium phosphate is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the chemical formula Ca(H₂PO₄)₂ ("AMCP" or "CMP-A" for anhydrous monocalcium phosphate). It is commonly found as the

monohydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was underst ...

("MCP" or "MCP-M"), Ca(H₂PO₄)₂·H₂O. Both salts are colourless solids. They are used mainly as superphosphate fertilizers and are also popular leavening agents.

Preparation

Material of relatively high purity, as required for baking, is produced by treating calcium hydroxide with phosphoric acid: Samples of Ca(H₂PO₄)₂ tend to convert to dicalcium phosphate:

Applications

Use in fertilizers

Superphosphate fertilizers are produced by treatment of " phosphate rock" with acids ("acidulation"). Using phosphoric acid,

fluorapatite Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula Ca5(PO4)3F (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, bl ...

is converted to Ca(H₂PO₄)₂: This solid is called triple superphosphate. Several million tons are produced annually for use as fertilizers. Using

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

is converted to a mixture of Ca(H₂PO₄)₂ and CaSO₄. This solid is called single superphosphate. Residual HF typically reacts with silicate minerals co-mingled with the phosphate ores to produce hexafluorosilicic acid (H₂SiF₆). The majority of the hexafluorosilicic acid is converted to aluminium fluoride and cryolite for the processing of aluminium. These materials are central to the conversion of aluminium ore into aluminium metal. When

is used, the product contains phosphogypsum (CaSO₄·2H₂O) and is called single superphosphate.

Use as leavening agent

Calcium dihydrogen phosphate is used in the food industry as a leavening agent, i.e., to cause baked goods to rise. Because it is acidic, when combined with an alkali ingredient, commonly

sodium bicarbonate Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...

(baking soda) or potassium bicarbonate, it reacts to produce carbon dioxide and a salt. Outward pressure of the carbon dioxide gas causes the rising effect. 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. AMCP and MCP are fast acting, releasing most carbon dioxide within minutes of mixing. It is popularly used in

pancake A pancake (or hotcake, griddlecake, or flapjack) is a flat cake, often thin and round, prepared from a Starch, starch-based batter (cooking), batter that may contain eggs, milk and butter and cooked on a hot surface such as a griddle or fryi ...

mixes. In double acting baking powders, MCP is often combined with the slow acting acid sodium acid pyrophosphate (SAPP).John Brodie, John Godber "Bakery Processes, Chemical Leavening Agents" in ''Kirk-Othmer Encyclopedia of Chemical Technology'' 2001, John Wiley & Sons.

Preparation

Applications

Use in fertilizers

Use as leavening agent

See also

References

Further reading