Aluminium Phosphate

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What is Aluminium Phosphate?

Aluminium Phosphate, or Aluminium (III) Phosphate, is an inorganic salt that is found in several minerals and is often used as a catalyst. It is also used in the pharmaceutical industry for manufacturing chemotherapeutic drugs. It occurs naturally in the form of the mineral berlinite. It is prepared chemically when soluble Aluminium salts are exposed to alkaline conditions. It is represented as AlPO4, which consists of hydrated Aluminium Orthophosphate. The Aluminium Phosphate solutions form polymeric aggregates wherein equilibrium is reached very slowly. It forms soluble Aluminium salts and Phosphoric acid by slowly reacting with Gastric acid. 

However, it absorbs the bile acids weaker than Aluminium Hydroxide. Here, we will learn what is Aluminium Phosphate, what is the formula for Aluminium Phosphate, what is Aluminium Phosphate used for, and the properties of Aluminium Phosphate.

Aluminium Phosphate Structure- AlPO4

Aluminium Phosphate generally occurs as an anhydrous salt. However, its dihydrate and pentahydrate structures occur as well, which are represented as AlPO4.2H2O and AlPO4.5H2O.

The Aluminium Phosphate compound is formed by the Phosphate anion and Aluminium cation. Its anhydrous salt structure is much similar to several other minerals like quartz and has a trigonal crystal structure. However, its dihydrate form has a structure similar to NaCl in which 6 cations are coordinated to 6 anions. The structure of Aluminium Phosphate AlPO4 is shown below. This representation is commonly used for organic molecules.

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Chemical Formula of Aluminium Phosphate

Let us take a look at what is the chemical formula for aluminium phosphate.

Aluminium Phosphate is also called Aluminium Monophosphate or Mono-Aluminium Phosphate. It is formed by the Phosphate anion PO43-, and the Aluminium cation Al3+. Hence, the chemical or molecular formula of Aluminium Phosphate is AlPO4.

It occurs as a white crystalline powder. However, it is a colourless liquid in its aqueous form. It is insoluble in water and occurs in the form of a mineral berlinite. Aluminium phosphate is found in minerals like variscite and meta-variscite in its dihydrate form. Since it has piezoelectric properties, it is widely used in the electronic and electrical industries.

Now that you know about what is Aluminum Phosphate and what is the chemical formula for Aluminum Phosphate, let us take a look at some of its properties.

Physical Properties of Aluminium Phosphate AlPO4 

Let us now discuss the physical properties of Aluminium Phosphate AlPO4 .


White crystalline powder


Foul odour



Hydrogen Bond Acceptor


Covalently-Bonded Unit



Insoluble in water. Highly soluble in HCl and HNO3

Melting Point

1800 °C or 3270 °F or 2070 K

Boiling Point

Decomposes at boiling point

Chemical Properties of Aluminium Phosphate AlPO4

Now let us go through the chemical properties of Aluminium Phosphate AlPO4.

  1. Aluminium Phosphate reacts with Hydrochloric Acid to form Aluminium Trichloride and Phosphoric acid. The reaction is as follows.

AlPO4 + 3HCl → AlCL3 + H3PO4

  1. Aluminium Phosphate reacts with Magnesium Chloride to form Magnesium Phosphate and Aluminium Trichloride. The reaction is given as follows.

2AlPO4 + 3MgCl2 → Mg3(Po4)2 + 2AlCl3

FAQ (Frequently Asked Questions)

1. What is Aluminum Phosphate used for?

Answer: Aluminium Phosphate is used in the following ways across different industries.

  1. Aluminium tablets are used to maintain blood pressure and every tablet consists of 500mg of dry Aluminium Phosphate which gives a peppermint flavour.

  2. It is used as an antacid.

  3. It is also used to manufacture vaccines to enhance immunogenicity.

  4. Aluminium Phosphate-Carbonate gel was used in the water suspension of hydroxy Aluminium Carbonate along with orthophosphoric acid.

  5. Aluminium Phosphate, with or without the combination of several other compounds, is used as a white colourant for several pigments, cement, corrosion inhibitors, and even dental cement.

2. What is sodium Aluminum Phosphate?

Answer: Sodium Aluminium Phosphate, or SAlP, is an organic compound that consists of Sodium salts of Aluminium Phosphate. The most common Sodium Aluminium Phosphates are NaH14Al3(PO4)8·4H2O and  Na3H15Al2(PO4)8.

The acidic Sodium Aluminium Phosphates have their use as baking powders for chemical leavening of baked items. On heating, Sodium Aluminium Phosphate combines with baking soda and gives carbon dioxide. Most of this reaction happens at baking temperatures than when the batter or dough is mixed at room temperature. Sodium Aluminium Phosphates have an added advantage since they have a neutral flavour.

3. What does Sodium Aluminum Phosphate do to your body?

Answer: The food-grade Aluminium Sodium Phosphate is recognized safe by FDA. This can be because the amount of Sodium Aluminium Phosphate added to the food is comparatively less. However, when it is used in the form of a food additive it tends to impact the health differently when compared to its natural state. Higher levels of Sodium Aluminium Phosphate can elevate the mortality rates. It also increases the risk of cardiovascular and kidney diseases. Higher phosphate levels are also linked to vascular damage and accelerated aging. Hence, most people prefer having Sodium Aluminium Sulphate in its naturally occurring form.