Ammonium Phosphate - Formula, Properties, Uses, FAQs

Introduction
Ammonium phosphate ((NH4)3PO4) is a salt of ammonia and phosphoric acid. It is also known as ammonium orthophosphate. It consists of ammonium cations and phosphate anions (NH4 plus and PO42-). It is a water-soluble salt and if the aqueous solution is boiled, it liberates ammonia.

Formula for ammonium phosphate (chemical formula of ammonium phosphate)

The molecular formula of ammonium phosphate is- (NH4)3PO4

Ammonium phosphate fertilizer

Ammonium phosphates can be applied to soil as nitrogen and phosphorus containing fertilizer either directly, or as a solution, or in a suspension form. The distribution pattern depends on the proportion of insoluble phosphates present in the soil. Ammonium orthophosphates are preferred to a generic class of phosphorus fertilizers. These are manufactured by reacting anhydrous ammonia with orthophosphoric acid or super phosphoric acid on a large scale. These are prepared either in solid or liquid form.

There are two main types of ammonium phosphate - monoammonium phosphate (MAP) and diammonium phosphate (DAP). These two major types of ammonium phosphate are inter-convertible by changing ammonia or phosphoric acid as per requirement.

Mono-ammonium phosphate or Ammonium hydrogen phosphate is manufactured by reacting ammonia with phosphoric acid in a reactor and consequently centrifuging and drying in a rotary dryer in the manufacturing industry. While manufacturing of diammonium phosphate requires a two-stage reactor system in order to avoid loss of ammonia. Thereafter, the granulation followed by neutralization processes is completed in a rotary dryer, which is heated by a furnace using fuel.

Ammonium hydrogen phosphate chemical formula

The molecular formula of Ammonium hydrogen phosphate or monoammonium phosphate is- NH4H2PO4

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• NCERT Solutions for Class 11 Chemistry
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Diammonium phosphate formula

The molecular formula of Diammonium phosphate formula is- (NH4)2HPO4

Two grades of ammonium phosphate are available

1. Monoammonium phosphate (MAP): Anhydrous ammonia is added to liquid phosphoric acid to produce monoammonium phosphate (MAP). It is fertilizer or can be considered as fertilizer intermediate with high P2O5 content, i.e., almost 55%. Its nitrogen content is about 11-12%.

Properties:

• Ammonium phosphate molecular weight (molar mass of nh4 3po4/molecular mass of ammonium phosphate/ ammonium phosphate molar mass): Molecular mass of ammonium phosphate is- 115.03gm/mole
• Appearance: White crystal
• Odour: Odourless
• Melting point: 1900C
• Density: 1.803gm/mL
• Solubility: Moderately soluble in water
• pH: 4-4.5
• These fertilizers are highly soluble in water and react fast in the soil to give nitrogen and phosphorus in a chemical combination.
• Pure ammonium phosphates are used mainly as liquid fertilizers since it is completely soluble in water.
• Diammonium phosphate is unstable at temperatures above 1500˚C whereas monoammonium phosphate is stable even at higher temperatures than 1500˚C.
• Monoammonium and diammonium phosphates usually form a part of concentrated compound fertilizer and are used instead of pure states.

2. Diammonium phosphate (DAP): it is manufactured by adding more ammonia with phosphoric acid. In diammonium phosphate (DAP) nitrogen content is about 16 to 18% and phosphorus content is about 20 to 21 % phosphorus (46% P2O5).

Diammonium phosphate molecular weight

The molecular mass of diammonium phosphate is- 132.06 g/mol

Atomicity of ammonium phosphate

The atomicity of ammonium phosphate molecule is 20

Manufacture of ammonium phosphate

Raw Materials

Ammonia, Phosphoric acid

Reactions

NH3 + H3PO4 NH4H2PO4

NH3 + NH4H2PO4 (NH4)2HPO4

Sources of raw material

Ammonia can be synthesized by the Haber process

Phosphoric can be manufactured by electric arc furnace, blast furnace, or wet process

Ammonium phosphate can be produced on large scale in the industry by following two principal steps-

a) Neutralization

b) Granulation

Neutralization

Quantities of phosphoric acid and ammonia required during manufacturing in the neutralization step are different for mono ammonium phosphate (MAP) and diammonium phosphate (DAP). In the production mono ammonium phosphate, the ammonia to phosphoric acid ratio should be maintained at 0.6 in the neutralizer and 1.0 in the granulator. While for diammonium phosphate, the ratios of ammonia to phosphoric acid should be maintained at 1.4 in the neutralizer and 1.0 in the granulator.

• Step 1: Phosphoric acid is added to ammonia to the first of three continuous mixed reactors. In the first neutralizer, beneath the slurry level, anhydrous ammonia is added in a particular amount so that almost 80% neutralization can occur in the 1st tank.
• Step 2: Further ammonia is added in the 2nd and 3rd neutralizer to obtain conversion of diammonium phosphate with higher nitrogen content. The heat obtained from the exothermic reaction inside the tank is enough to heat the slurry nearly to the boiling point (130°C).
• Step 3: Unreacted and excess ammonia (in the vaporized state) is collected from the top of each tank and sent to the source container of the liquid ammonia to reduce excess loss.
• Step 4: The hot slurry, containing about 16 to 20% water, then is pumped into the granulator.
• Step 5: More ammonia is added to the granulator to increase the molar ratio to approximately 2.0.

Granulation

• Step 6: From the third neutralizer, the hot slurry is mixed with KCl.
• Step 7: Then the KCl mixed slurry is then absorbed in a bed of dry recycled fertilizer which is moving through a rotating drum granulator.
• Step 8: A rotary adiabatic dryer then reduces the moisture to less than 1%.
• Step 9: The resulting Dried product is then separated into three parts on a double-deck screen.
• Step 10: thereafter, a small section of the product from the lower screen of the deck is transferred for the bagging operations.
• Step 11: the oversized and the smaller-sized granules are again sent to the granulator for further processing.

Powder ammonium phosphate

Ammonium phosphate is powdered to in used as a fertiliser for its high phosphorus content (as P2O5).

Besides this, a few fertilizers, such as ammonium phosphate sulphate fertilizer, ammonium phosphate-chloride, and ammonium phosphate-nitrate are produced by different types of processes which include the neutralization of ammonia with a mixture of phosphoric acid. Few plant waste acids like sulfuric acid, nitric acid, or hydrochloric are also added. The fertilizers thus formed are free flowing and less hygroscopic as compared to the individual components. These fertilizers are also successfully used in different types of soils.

Also read :

• NCERT solutions for Class 12 Chemistry Chapter 13 Amines
• NCERT Exemplar Class 12 Chemistry solutions Chapter 13 Amines
• NCERT notes Class 12 Chemistry Chapter 13 Amines

Ammonium phosphate uses (mono ammonium phosphate uses)

• These fertilizers are used as highly effective and non-chloride nitrogen, Potassium containing compound fertilizer in agriculture. Its nitrogen and phosphorus content is totally (N+P2O5) about 73%.
• This is also used in manufacturing yeast, vinegar, yeast foods, and bread improvers.
• This can be used in buffer solutions and in an analytical chemistry laboratory
• This can also be applied in preventing the fabric from fire, fire prevention coating, and as dry powder for a fire extinguisher.
• It is used as fermenting agent, a nourishing agent in food grade.

Also check-

• NCERT Exemplar Class 11th Chemistry Solutions
• NCERT Exemplar Class 12th Chemistry Solutions
• NCERT Exemplar Solutions for All Subjects

NCERT Chemistry Notes :

• NCERT notes Class 11 Chemistry
• NCERT notes Class 12 Chemistry
• NCERT Notes For All Subjects