Magnesium Phosphate Formula: Definition, Derivation, Properties

Magnesium phosphate formula is represented as \({{\rm{M}}{{\rm{g}}_3}{{\left( {{\rm{P}}{{\rm{O}}_4}} \right)}_2} \cdot }\) It is the magnesium acid salt of phosphoric acid. It is also known as trimagnesium phosphate. It exists in different hydrated forms with varying amounts of water of crystallisation \(\left[ {{\rm{M}}{{\rm{g}}_3}{{\left( {{\rm{P}}{{\rm{O}}_4}} \right)}_2} \cdot {\rm{x}}{{\rm{H}}_2}{\rm{O}}} \right].\)

Magnesium phosphate formula is derived by using the criss-cross method. Magnesium phosphate is utilised as a dietary s

upplement for treating magnesium deficiency. In this article, let’s discuss everything about magnesium phosphate in detail. Scroll down to learn more!

Magnesium Phosphate Chemical Formula

The chemical formula of magnesium phosphate is \({{\rm{M}}{{\rm{g}}_3}{{\left( {{\rm{P}}{{\rm{O}}_4}} \right)}_2} \cdot }\) It contains magnesium \(\left( {{\rm{M}}{{\rm{g}}^{2 + }}} \right)\) and phosphate \(\left( {{\rm{PO}}_4^{3 – }} \right)\) ions. There exists an ionic bond between magnesium and phosphate ions. Thus, it is considered an ionic compound.

Magnesium phosphate can be represented as,

or,

The molar mass of magnesium phosphate is \(262.855\;{\rm{g}}/{\rm{mol}}.\)

Magnesium Phosphate Chemical Formula Derivation

The chemical formula of magnesium phosphate can be derived using the criss-cross method.

In the criss-cross method, using the valency of the individual elements, we can easily write its chemical formula. The symbol of the positive ion of a compound is written on the left side, and the symbol of the negative ion is written on the right side. Their valency is interchanged and written as subscripts. Signs of the charges are ignored. The subscript one is not often written.

Using this, the chemical formula of magnesium phosphate can be written as,Magnesium phosphate contains magnesium \(\left( {{\rm{M}}{{\rm{g}}^{2 + }}} \right)\) and phosphate \(\left( {{\rm{PO}}_4^{3 – }} \right)\) radicals. The valency of magnesium radical is two, and that of phosphate ion is three. By criss-crossing this valency, the chemical formula of magnesium phosphate is written as \({{\rm{M}}{{\rm{g}}_3}{{\left( {{\rm{P}}{{\rm{O}}_4}} \right)}_2} \cdot }\) That is,

Preparation of Magnesium Phosphate

Magnesium phosphate can be prepared using the following methods: 

1. By the Reaction of Magnesium with Phosphoric Acid:

Magnesium phosphate is produced when magnesium metal is reacted with phosphoric acid. The chemical equation for the reaction can be represented as,

\(3{\rm{Mg}} + 2{{\rm{H}}_3}{\rm{P}}{{\rm{O}}_4}\, \to \,{\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2} + 3{{\rm{H}}_2}\)

2. By the Reaction of Magnesium Hydroxide and Phosphoric Acid: 

Magnesium hydroxide reacts with phosphoric acid to form magnesium phosphate and water. The chemical equation for the reaction can be represented as,

\(2{{\rm{H}}_3}{\rm{P}}{{\rm{O}}_4} + 3{\rm{Mg}}{({\rm{OH}})_2} \to {\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2} + 6{{\rm{H}}_2}{\rm{O}}\)

3. By the Reaction of Magnesium Oxide and Phosphoric Acid: 

Magnesium phosphate is produced when magnesium oxide reacts with phosphoric acid. The chemical equation for the reaction can be represented as,

\(3{\rm{MgO}} + 2{{\rm{H}}_3}{\rm{P}}{{\rm{O}}_4} \to {\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2} + 3{{\rm{H}}_2}{\rm{O}}\)

4. By the Reaction between Trisodium Phosphate and Magnesium Sulphate: 

Magnesium phosphate is precipitated when magnesium sulphate is reacted with trisodium phosphate. The chemical equation for the reaction can be represented as,

\(3{\rm{MgS}}{{\rm{O}}_4} + 2{\rm{N}}{{\rm{a}}_3}{\rm{P}}{{\rm{O}}_4} \to 3{\rm{N}}{{\rm{a}}_2}{\rm{S}}{{\rm{O}}_4} + {\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2} \downarrow \)

The above reaction is an example of precipitation reaction.

This method can also be employed using magnesium chloride. That is, by the reaction between trisodium phosphate and magnesium chloride. The chemical equation for the reaction can be represented as,

\(3{\rm{MgC}}{{\rm{l}}_2} + 2{\rm{N}}{{\rm{a}}_3}{\rm{P}}{{\rm{O}}_4} \to {\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2} \downarrow + 6{\rm{NaCl}}\)

5. By heating the naturally occurring hydrates of magnesium phosphate to around \({\rm{400}}\,^\circ {\rm{C}},\) we can get anhydrous magnesium phosphate, \({\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2}.\)

Properties of Magnesium Phosphate

Let’s discuss about magnesium phosphate’s physical and chemical features.

Physical Properties of Magnesium Phosphate

The physical properties of magnesium phosphate are as follows:

1. Magnesium phosphate appears as a white crystalline powder.
2. Generally, most phosphate salts are soluble in water. But magnesium phosphate is insoluble in water because magnesium salts are usually insoluble in water. Magnesium cations generally form insoluble compounds. It is soluble in salt solutions. 
3. The melting point of magnesium phosphate is \({\rm{1457}}\,{\rm{K}}{\rm{.}}\)

Chemical Properties of Magnesium Phosphate

The chemical properties of magnesium phosphate are as follows:

1. The reaction of Magnesium phosphate with Hydrochloric Acid

Magnesium phosphate reacts with hydrochloric acid to give magnesium chloride salt and phosphoric acid as the products. The chemical equation for the reaction can be represented as,

\({\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2} + 6{\rm{HCl}} \to 3{\rm{MgC}}{{\rm{l}}_2} + 2{{\rm{H}}_3}{\rm{P}}{{\rm{O}}_4}\)

2. The reaction of Magnesium phosphate with Sodium Hydroxide

Magnesium phosphate reacts with sodium hydroxide to form sodium phosphate and magnesium hydroxide. The chemical equation for the reaction can be represented as,

\({\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2} + 6{\rm{NaOH}} \to 2{\rm{N}}{{\rm{a}}_3}{\rm{P}}{{\rm{O}}_4} + 3{\rm{Mg}}{({\rm{OH}})_2}\)

Phosphates or phosphate salts are generally good acidity regulators.

Uses of Magnesium Phosphate

Magnesium phosphate has several uses. Some of the uses of Magnesium Phosphate are as follows:

1. Magnesium phosphate is majorly used as an acidity regulator in foods.
2. It is used in fertilisers.
3. It is used as a dentifrice polishing agent.
4. It is used in cosmetics, shampoos, toothpaste, perfumes, etc.
5. It is used as an adsorbent, stabilizer for plastics, etc.
6. It is also used in non-pesticidal agricultural products.
7. It is also used to treat vitamin E deficiency.
8. Magnesium phosphate is used as a dietary supplement for treating magnesium deficiency.
9. For silicate-containing cleaning agents, it is used as an anticaking agent.

Summary

We are now familiar with magnesium phosphate. It is an inorganic chemical compound with the formula \({\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2}.\) It is also known as trimagnesium phosphate. It is the magnesium salt of phosphoric acid and is considered an ionic compound. It can be prepared by the action of phosphoric acid on magnesium, magnesium hydroxide or magnesium oxide. The other preparation methods, the physical and chemical properties and their several uses are detailed in this article.

FAQs on Magnesium Phosphate

Q.1. What is the formula for magnesium phosphate?
Ans: The chemical formula of magnesium phosphate is \({\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2}.\)

Q.2. What is the use of magnesium phosphate?
Ans: Magnesium phosphate has several uses. It is used in fertilizers, dietary supplements, adsorbents, stabilisers for plastics, etc.

Q.3. How can we write the chemical formula of magnesium phosphate?
Ans: The chemical formula of magnesium phosphate can be written using the criss-cross method. Magnesium phosphate contains magnesium \(\left( {{\rm{M}}{{\rm{g}}^{{\rm{2 + }}}}} \right)\) and phosphate \(\left( {{\rm{PO}}_4^{3 – }} \right)\) radicals. The valency of magnesium radical is two, and that of phosphate ion is three. By criss-crossing this valency, the chemical formula of magnesium phosphate is written as \({\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2}.\)

Q.4. What is the name for \({\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2}\)?
Ans: The chemical name of \({\rm{M}}{{\rm{g}}_3}{\left( {{\rm{P}}{{\rm{O}}_4}} \right)_2}\) is magnesium phosphate or trimagnesium phosphate.

Q.5. Is magnesium phosphate safe?
Ans: Magnesium phosphate is recognized as safe by Food and Drug Administration (FDA).

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