Ammonium Phosphate - Formula, Properties, Uses, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:56 PM IST

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.

Mono Ammonium Phosphate

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.

general manufacturing process of phosphate fertilizer

Ammonium hydrogen phosphate chemical formula

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

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Formula for ammonium phosphate (chemical formula of ammonium phosphate)
Diammonium phosphate formula
Ammonium phosphate uses (mono ammonium phosphate uses)

Diammonium phosphate formula

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

Two grades of ammonium phosphate are available

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

Atomicity of ammonium phosphate ammonium phosphate molecular structure

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

manufacturing of ammonium phosphate

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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.

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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.

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NCERT Chemistry Notes :

Frequently Asked Questions (FAQs)

1. Give the balanced reaction when (NH4)3PO4 is added to Pb(NO3)4

4(NH4)3PO4 + 3 Pb(NO3)4 → Pb3(PO4)4 + 12 NH4NO3

2. What happens when Ammonium sulfate is heated above the temperature of 250°c?

Ammonium sulfate (NH4)2SO4 on heating gives ammonium bisulfate initially. On further heating ammonium bisulphates decomposes into NH3, N, SO2 and H2O.

3. A sample of ammonium phosphate contains 3.18 moles of hydrogen atom. Calculate The number of moles of oxygen atoms present in the sample.

149gm (molecular weight) of (NH4)3PO4 contains 12g of H.

3.18 moles of H = 3.18g of H

Therefore, 3.18gm of H present in (149×3.18)/ 12= 39.5gm (NH4)3PO4.

Now, 149gm of (NH4)3PO4 contains 64g of Oxygen.

Therefore, 39.5gm of (NH4)3PO4 will contain = (64×39.5)/ 149

=16.96 gm oxygen

Hence, 16.96g oxygen present in the sample.

Therefore, No. of moles of oxygen=16.96/ 16= 1.06 moles

4. Write down the ammonium phosphate formula?

(NH4)3PO4

5. What is the molecular weight of ammonium phosphate?

115.03gm/mole

6. What is the difference between monoammonium phosphate and diammonium phosphate?

Monoammonium phosphate (MAP) has the formula NH4H2PO4, while diammonium phosphate (DAP) has the formula (NH4)2HPO4. MAP has one ammonium ion per phosphate, while DAP has two. This affects their pH in solution and their effectiveness as fertilizers.

7. How does ammonium phosphate act as a flame retardant?

When heated, ammonium phosphate decomposes to release ammonia gas and form polyphosphoric acid. This acid creates a protective layer that chars and insulates the material, preventing oxygen from reaching the fuel and thus inhibiting combustion.

8. Why is ammonium phosphate an effective fertilizer?

Ammonium phosphate is an effective fertilizer because it provides two essential nutrients for plant growth: nitrogen (from the ammonium ion) and phosphorus (from the phosphate ion). It's also highly water-soluble, making these nutrients readily available to plants.

9. Why is ammonium phosphate used in fire extinguishers?

Ammonium phosphate is used in fire extinguishers because of its flame retardant properties. When heated, it releases ammonia and forms a coating of phosphoric acid, which smothers the fire and prevents reignition.

10. How does the structure of ammonium phosphate contribute to its properties?

The structure of ammonium phosphate, with its ammonium cations and phosphate anions, contributes to its high solubility in water, its ability to release ammonia gas when heated, and its effectiveness as a fertilizer due to the presence of both nitrogen and phosphorus.

11. Why is ammonium phosphate considered a salt?

Ammonium phosphate is considered a salt because it's formed by the reaction between a base (ammonia) and an acid (phosphoric acid). It's an ionic compound that dissociates into its constituent ions in water.

12. What happens to ammonium phosphate when it's heated?

When heated, ammonium phosphate decomposes, releasing ammonia gas (NH3) and forming phosphoric acid (H3PO4). Further heating can lead to the formation of various polyphosphates.

13. How does the pH of a solution change when ammonium phosphate is dissolved in water?

When ammonium phosphate dissolves in water, it slightly lowers the pH, making the solution mildly acidic. This is due to the ammonium ion acting as a weak acid, releasing small amounts of H+ ions into the solution.

14. How does the nitrogen-to-phosphorus ratio in ammonium phosphate affect its use in agriculture?

The nitrogen-to-phosphorus ratio in ammonium phosphate determines its suitability for different crops and soil conditions. For example, a 1:1 ratio (as in monoammonium phosphate) might be more suitable for phosphorus-deficient soils, while a higher nitrogen ratio could benefit nitrogen-loving crops.

15. How does the solubility of ammonium phosphate compare to other phosphate salts?

Ammonium phosphate is generally more soluble in water than many other phosphate salts, such as calcium phosphate. This high solubility makes it an excellent choice for fertilizers as it allows for quick nutrient uptake by plants.

16. What is the chemical formula of ammonium phosphate?

The chemical formula of ammonium phosphate is (NH4)3PO4. This compound consists of three ammonium (NH4+) ions and one phosphate (PO43-) ion.

17. What is the difference between orthophosphate and polyphosphate forms of ammonium phosphate?

Orthophosphates, like regular ammonium phosphate (NH4)3PO4, contain a single phosphate unit. Polyphosphates, formed when ammonium phosphate is heated, contain multiple phosphate units linked together. Polyphosphates often have different properties and applications compared to orthophosphates.

18. How does the crystal structure of ammonium phosphate influence its properties?

The crystal structure of ammonium phosphate, with its ionic bonds between ammonium cations and phosphate anions, contributes to its high solubility in water and its ability to readily dissociate into ions. This structure also influences its thermal decomposition behavior.

19. What is the significance of the NH4+/NH3 equilibrium in ammonium phosphate solutions?

The NH4+/NH3 equilibrium in ammonium phosphate solutions is important because it affects the solution's pH and the availability of nitrogen. This equilibrium shifts based on pH, temperature, and concentration, influencing the compound's behavior in various applications.

20. What is the significance of the N:P ratio in different forms of ammonium phosphate fertilizers?

The N:P ratio in ammonium phosphate fertilizers determines their suitability for different crops and soil conditions. For example, a 1:1 ratio might be more suitable for phosphorus-deficient soils, while a higher nitrogen ratio could benefit nitrogen-loving crops.

21. What safety precautions should be taken when handling ammonium phosphate?

When handling ammonium phosphate, one should wear protective gear such as gloves and safety glasses. It can cause eye and skin irritation. Avoid inhaling dust, and ensure proper ventilation. In case of contact, rinse thoroughly with water.

22. How does ammonium phosphate interact with other soil nutrients?

Ammonium phosphate can interact with other soil nutrients in complex ways. For example, it can temporarily tie up some micronutrients like zinc or iron, making them less available to plants. However, it can also enhance the uptake of certain nutrients by improving overall plant health.

23. What is the environmental impact of using ammonium phosphate fertilizers?

While ammonium phosphate provides essential nutrients, overuse can lead to environmental issues such as eutrophication of water bodies. Excess phosphates can run off into waterways, causing algal blooms. Proper application and soil management practices are crucial to minimize negative impacts.

24. How does ammonium phosphate compare to organic fertilizers in terms of nutrient availability?

Ammonium phosphate, being a synthetic fertilizer, provides nutrients in a readily available form for immediate plant uptake. Organic fertilizers, on the other hand, release nutrients more slowly as they decompose. This means ammonium phosphate has a quicker effect but may require more frequent application.

25. How does the presence of ammonium phosphate affect water quality in aquatic ecosystems?

Excess ammonium phosphate in water bodies can lead to eutrophication, causing algal blooms that deplete oxygen levels and harm aquatic life. It's crucial to manage its use to prevent runoff into water systems.

26. How does the use of ammonium phosphate in fertilizers impact soil microbial communities?

The application of ammonium phosphate can influence soil microbial communities. The influx of readily available nutrients can stimulate microbial growth initially. However, long-term use may shift the microbial population, potentially affecting soil health and nutrient cycling.

27. How does ammonium phosphate compare to other nitrogen fertilizers in terms of nitrogen loss to the atmosphere?

Ammonium phosphate generally has lower nitrogen loss to the atmosphere compared to some other nitrogen fertilizers like urea. The phosphate component helps to stabilize the ammonium, reducing volatilization losses.

28. How does the hygroscopic nature of ammonium phosphate affect its storage and use?

Ammonium phosphate is hygroscopic, meaning it tends to absorb moisture from the air. This property can lead to caking during storage, affecting its flowability. Proper storage in airtight containers is important to maintain its quality and ease of use.

29. How does the use of ammonium phosphate in agriculture impact the phosphorus content of surface waters?

Overuse or improper application of ammonium phosphate can lead to phosphorus runoff into surface waters. This excess phosphorus can cause eutrophication, leading to algal blooms and potential ecological imbalances in aquatic ecosystems.

30. How does ammonium phosphate affect the cation exchange capacity (CEC) of soil?

While ammonium phosphate itself doesn't directly increase CEC, the ammonium ions it provides can occupy exchange sites on soil particles. Over time, as plants take up these ions, it can indirectly influence the soil's CEC by affecting the balance of other cations.

31. How does the presence of ammonium phosphate affect the water retention capacity of soil?

Ammonium phosphate can indirectly affect soil water retention by influencing soil structure and organic matter content. Improved plant growth due to nutrient availability can lead to increased organic matter, which enhances water retention capacity.

32. What is the significance of ammonium phosphate in the context of sustainable agriculture?

In sustainable agriculture, the use of ammonium phosphate raises questions about resource depletion (particularly phosphorus), energy use in production, and environmental impacts. Balancing its benefits with these concerns is crucial for developing sustainable farming practices.

33. How does ammonium phosphate compare to other phosphate fertilizers in terms of phosphorus use efficiency?

Ammonium phosphate generally has high phosphorus use efficiency compared to some other phosphate fertilizers. The presence of ammonium can enhance phosphorus uptake by plants, and its high solubility makes the phosphorus readily available.

34. How does ammonium phosphate affect soil pH when used as a fertilizer?

When used as a fertilizer, ammonium phosphate can initially lower soil pH slightly due to the release of H+ ions from the ammonium. However, as plants take up the ammonium ions, the soil pH may increase over time.

35. What is the role of ammonium phosphate in food additives?

In food additives, ammonium phosphate serves as a dough conditioner and leavening agent. It helps improve dough texture, increase volume, and enhance the overall quality of baked goods.

36. Why is ammonium phosphate sometimes used in brewing and winemaking?

In brewing and winemaking, ammonium phosphate serves as a yeast nutrient. It provides nitrogen and phosphorus, essential for yeast growth and fermentation. This can help ensure a complete and efficient fermentation process, especially in musts or worts that are deficient in these nutrients.

37. What role does ammonium phosphate play in the phosphorus cycle?

As a phosphorus-containing compound, ammonium phosphate contributes to the phosphorus cycle when used in agriculture. It adds phosphorus to the soil, which can be taken up by plants, consumed by animals, and eventually returned to the soil through decomposition or waste products.

38. Why is ammonium phosphate sometimes used in molecular biology laboratories?

In molecular biology, ammonium phosphate is used in some DNA precipitation protocols. Its high solubility and ability to alter solution conditions make it useful for precipitating nucleic acids out of solution.

39. How does temperature affect the solubility of ammonium phosphate?

Like many salts, the solubility of ammonium phosphate generally increases with temperature. This property is important to consider in various applications, from fertilizer use to industrial processes.

40. How does ammonium phosphate interact with calcium in soil?

Ammonium phosphate can react with calcium in soil to form less soluble calcium phosphate compounds. While this can reduce the immediate availability of phosphorus, it also helps prevent phosphorus from being washed away and provides a slow-release source of the nutrient.

41. Why is ammonium phosphate sometimes used in matches?

In matches, ammonium phosphate serves as both a flame retardant and a source of nitrogen. It helps control the burning rate of the match and contributes to the production of nitrogen gas, which aids in propelling the flame.

42. What is the role of ammonium phosphate in some types of baking powder?

In some baking powders, ammonium phosphate acts as an acid component. When combined with a base (like sodium bicarbonate) and exposed to moisture and heat, it produces carbon dioxide gas, which helps leaven baked goods.

43. Why is ammonium phosphate sometimes used in fireproofing materials?

Ammonium phosphate is used in fireproofing materials due to its flame-retardant properties. When heated, it decomposes to form a protective layer of phosphoric acid, which chars and insulates the material underneath, slowing the spread of fire.

44. How does the presence of ammonium phosphate affect the freezing point of water?

Like other dissolved salts, ammonium phosphate lowers the freezing point of water. This colligative property depends on the concentration of the solution and is why salt solutions are used in some de-icing applications.

45. How does ammonium phosphate contribute to the buffering capacity of soil?

Ammonium phosphate can contribute to soil buffering capacity through the phosphate component. Phosphate ions can accept or donate protons, helping to resist changes in soil pH within a certain range.

46. Why is ammonium phosphate sometimes used in the production of ceramics?

In ceramics production, ammonium phosphate can be used as a flux or as a source of phosphorus in glazes. When heated, it decomposes, leaving behind phosphorus oxide which can influence the melting behavior and final properties of the ceramic.

47. What is the role of ammonium phosphate in some types of dry chemical fire extinguishers?

In dry chemical fire extinguishers, ammonium phosphate serves as the main extinguishing agent. When discharged, it forms a fine powder that smothers the fire and, upon heating, releases substances that interrupt the chemical reactions in the flame.

48. How does ammonium phosphate affect the electrical conductivity of soil?

The addition of ammonium phosphate to soil generally increases its electrical conductivity due to the introduction of ions. This change in conductivity can be used as an indicator of soil fertility and salt content.

49. Why is ammonium phosphate sometimes used in the production of some types of cheese?

In cheese production, ammonium phosphate can be used as a buffering agent to control acidity during the fermentation process. It can also serve as a nutrient source for the bacteria involved in cheese ripening.

50. How does the presence of ammonium phosphate influence plant root development?

Ammonium phosphate can stimulate root development, particularly the growth of fine roots and root hairs. The readily available phosphorus promotes root growth, while the ammonium form of nitrogen can enhance nutrient uptake efficiency.

51. How does ammonium phosphate interact with clay minerals in soil?

Ammonium phosphate can interact with clay minerals in complex ways. The ammonium ions can be fixed by certain clay minerals, while phosphate ions can be adsorbed onto clay surfaces. These interactions affect nutrient availability and soil structure.

52. Why is ammonium phosphate sometimes used in the production of flame-resistant textiles?

Ammonium phosphate is used in flame-resistant textiles due to its ability to form a protective char when heated. This char acts as an insulating layer, reducing the spread of flames and protecting the underlying fabric.

53. What is the role of ammonium phosphate in some types of explosives?

In some explosives, ammonium phosphate serves as an oxidizing agent. It provides oxygen for the combustion reaction, contributing to the explosive force. However, its use is limited compared to other more potent oxidizers.

54. Why is ammonium phosphate sometimes used in the production of some types of toothpaste?

In toothpaste, ammonium phosphate can serve as a buffering agent to control pH. It may also contribute to remineralization of tooth enamel by providing phosphate ions, although its use for this purpose is less common than other phosphate compounds.

55. Why is understanding the chemistry of ammonium phosphate important for environmental science?

Understanding ammonium phosphate chemistry is crucial for environmental science because it impacts nutrient cycles, water quality, soil health, and agricultural productivity. This knowledge is essential for developing sustainable practices and mitigating environmental impacts of fertilizer use.