Aluminium Phosphate - AlPO4

What is Aluminium Phosphate?

Aluminium phosphate are prepared by exposing soluble aluminium salts to alkaline conditions contains hydrated aluminium orthophosphate with the formula AlPO4. The highly viscous aluminium phosphate solutions tend to form polymeric aggregates, and equilibria are reached only very slowly.

It reacts slowly with gastric acid to form soluble aluminum salts and phosphoric acid. It absorbs bile acids less strongly than aluminium hydroxide.

Other name – Aluminium monophosphate


Aluminium Phosphate


2.57 g/cm³

Molecular Weight/ Molar Mass

121.9529 g/mol


3.0 to 7.5

Melting Point

1,800 °C

Chemical Formula


Aluminium Phosphate Structure – AlPO4

Physical Properties of Aluminium Phosphate – AlPO4


foul odor


White, crystalline powder



Covalently-Bonded Unit


Hydrogen Bond Acceptor



Insoluble in water.

Chemical Properties of Aluminium Phosphate – AlPO4

  • Aluminium phosphate reacts with hydrochloric acid forming phosphoric acid and aluminium trichloride.

AlPO4 + 3HCl → AlCl3 + H3PO4

  • Aluminium phosphate reacts with magnesium chloride forming magnesium phosphate and aluminium trichloride.

2AlPO4 + 3MgCl2 → Mg3(PO4)2 + 2AlCl3

Uses of Aluminium Phosphate – AlPO4

  • Aluminium phosphate tablets are official in B.P. and each tablet contains 500 mg of dried aluminium phosphate suitable for peppermint flavour.

  • Used as an antacid beneficial in patients were significant loss of phosphate occur due to the use of aluminium salts.

  • Used in the manufacture of vaccines as an adjunct to enhance immunogenicity

  • Aluminium phosphate-carbonate gels were used in water suspension of hydroxy aluminium carbonate with orthophosphoric acid.