page_title: Dicalcium phosphate
section_title: Preparation
hierarchical_section_title: Dicalcium phosphate / Preparation
caption_attribution_description: English: Zoom-in around one Ca center showing the H's on water ligand and HPO42-.
context_page_description: Dicalcium phosphate is the calcium phosphate with the formula CaHPO₄ and its dihydrate. The "di" prefix in the common name arises because the formation of the HPO₄2– anion involves the removal of two protons from phosphoric acid, H₃PO₄. It is also known as dibasic calcium phosphate or calcium monohydrogen phosphate. Dicalcium phosphate is used as a food additive, it is found in some toothpastes as a polishing agent and is a biomaterial.
context_section_description: Dibasic calcium phosphate is produced by the neutralization of calcium hydroxide with phosphoric acid, which precipitates the dihydrate as a solid. At 60 °C the anhydrous form is precipitated:
  H₃PO₄ + Ca(OH)₂ → CaHPO₄
  To prevent degradation that would form hydroxyapatite, sodium pyrophosphate or trimagnesium phosphate octahydrate are added when for example, dibasic calcium phosphate dihydrate is to be used as a polishing agent in toothpaste.
  In a continuous process CaCl₂ can be treated with (NH₄)₂HPO₄ to form the dihydrate:
  CaCl₂ + (NH₄)₂HPO₄ → CaHPO₄•2H₂O
  A slurry of the dihydrate is then heated to around 65–70 °C to form anhydrous CaHPO₄ as a crystalline precipitate, typically as flat diamondoid crystals, which are suitable for further processing.
  Dibasic calcium phosphate dihydrate is formed in "brushite" calcium phosphate cements (CPC's), which have medical applications. An example of the overall setting reaction in the formation of  "β-TCP/MCPM" (β-tricalcium phosphate/monocalcium phosphate) calcium phosphate cements is:
  Ca₃(PO₄)₂ + Ca(H₂PO₄)₂•H₂O + 7 H₂O → 4 CaHPO₄•2H₂O
caption: Portion of the lattice of dicalcium phosphate dihydrate, highlighting the 8-coordinated Ca2+ center and the location the protons on three ligands (green = Ca, red = oxygen, orange = phosphorus, white = hydrogen)
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