Monocalcium phosphate is an inorganic compound with the chemical formula Ca(H2PO4)2 (“AMCP” or “CMP-A” for anhydrous monocalcium phosphate). It is commonly used as a fertilizer and as a food additive. It is commonly found as the monohydrate (“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.
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
Preparation
Material of relatively high purity, as required for baking, is produced by treating calcium hydroxide with phosphoric acid:
Ca(OH)2 + 2 H3PO4 → Ca(H2PO4)2 + 2 H2O
Samples of Ca(H2PO4)2 tend to convert to dicalcium phosphate:
Ca(H2PO4)2 → Ca(HPO4) + H3PO4
Natural Occurrence
Monocalcium phosphate can be found in trace amounts in nature, typically in the form of phosphate rock. However, it is not commonly found as a pure substance in nature. Phosphate rock is a major natural source of phosphorus, from which various forms of phosphate, including MCP, are derived through industrial processing.
Industrial Production
Production from Phosphate Rock: MCP is typically manufactured by reacting phosphate rock (primarily calcium phosphate) with phosphoric acid. The reaction process yields MCP, which is then purified and processed into various forms. Other Production Methods: MCP can also be synthesized by neutralizing phosphoric acid with calcium compounds (e.g., calcium carbonate, calcium hydroxide).
Occurrence
- Phosphorus in Biological Systems: Phosphates, including MCP, are naturally present in biological systems, as phosphorus is a vital nutrient for living organisms. It is essential for DNA, RNA, and energy transfer (ATP).
- Calcium Phosphate in Bone: While MCP is a distinct compound, it is similar to other forms of calcium phosphate found in bones and teeth, such as hydroxyapatite.
Applications
- In Fertilizers: Monocalcium phosphate is a source of phosphorus and calcium, both essential nutrients for plant growth. It is typically used in granular or powdered form and is often found in fertilizers that help promote root development and flowering in plants.
- In Animal Feed: It is also used as a supplement in animal feed to ensure that animals receive adequate phosphorus for bone formation and other metabolic functions.
- Food Additive: In food processing, it can be used as a leavening agent in baking powder, where it reacts with alkaline substances to produce carbon dioxide gas, helping dough or batter rise.
- Other Uses: MCP may be involved in water treatment and some industrial applications as well.
