Ammonium Nitrate Or NH4NO3, Reason of Beirut Massive Blast

Ammonium nitrate is a salt formed by nitrate and ammonium ions that is mainly used as a fertilizer due to its high nitrogen content.

TOPSHOT – A picture shows the scene of an explosion in Beirut on August 4, 2020. – A large explosion rocked the Lebanese capital Beirut on August 4. The blast, which rattled entire buildings and broke glass

2,750 tons of ammonium nitrate stored in a warehouse were the cause of the two explosions that devastated everything in Beirut, leaving at least 73 dead and more than 3,000 injured . This was confirmed by the Prime Minister of Lebanon, who explained that it had been stored for more than 6 years without any control measure. 

But what is ammonium nitrate? For what do you use it? Can it cause two explosions like the ones registered in Beirut?

What is Ammonium Nitrate?

The ammonium nitrate is a salt formed by ammonium and nitrate ions is used mainly as fertilizer because of its high nitrogen content. It is a white, odorless salt that is used as the base for many granular nitrogenous fertilizers, aminonitrates, highly soluble in water and purchased by farmers in large bags. They are not combustible products, but oxidants . Its detonation is possible in medium and high doses and in the presence of combustible substances or intense sources of heat.

A part of the production is dedicated to the production of nitrous oxide through controlled thermolysis. This reaction is exothermic and can be explosive if carried out in a closed container or heated too quickly.

It has different uses, from the industrial one , where it is used for the modification of the zeolite; as a fertilizer , where highly water soluble salt is the preferred source of nitrogen in fertilizers; And also as an explosive , as a strong oxidizing agent, it makes an explosive mixture when combined with a hydrocarbon, usually diesel fuel (oil), or sometimes kerosene.

That is why the storage of ammonium nitrate must follow strict regulations to isolate it from flammable liquids (gasoline, oils, etc.), corrosive liquids, flammable solids or substances that emit heat, among other prohibited substances, according to a technical sheet from the Ministry of French agriculture.

Ammonium nitrate has been the protagonist of numerous tragedies – accidental and criminal – in the world. One of his first accidents left 561 dead in 1921 at a BASF plant in Oppau, Germany.

In France , some 300 tons of ammonium nitrate stored in bulk in a hangar at the AZF chemical plant in Toulouse exploded on September 21, 2001, leaving 31 dead. The deflagration was heard 80 km away.

Also in the United States, a terrible explosion at the West Fertilizer plant , in Texas, killed 15 people in 2013, after an ammonium nitrate deposit exploded due to arson. The researchers questioned the absence of storage standards for the product at the Texas plant.


However, ammonium nitrate can also be used to make explosives. On April 19, 1995, Timothy McVeigh detonated a two-ton fertilizer bomb outside a federal building in Oklahoma City, leaving 168 dead and nearly 700 wounded.

Ammonium Nitrate formula Or Properties

Ammonium Nitrate is a white or colorless solid. It is hygroscopic, this means that it has a great affinity for water, absorbing ambient water vapor. It is a highly oxidized product, it can produce explosions by heating or percussion, especially if it is in finely divided powder form and in presence of catalysts such as permanganate potassium hydroxide or barium hydroxide. When heated under conditions of low risk or small amounts, its decomposition produces whitish or brown fumes, which are a mixture of: Nitrous Oxide, Nitrogen and higher Nitrogen Oxides, the latter are a mixture of Nitric Oxide and Nitrogen Dioxide.

  • Formula: NH 4 NO 3
  • Molecular mass: 80.04 g / mol
  • Melting point: 169.6 ºC
  • Boiling point: 210 ºC (decomposition)
  • Density: 1.72 g / ml
  • CAS No.: 6484 – 52 -2
  • LD50: 2,217 mg / kg (rat)

It can cause explosions, in the absence of water, or if it is exposed to high temperatures. It is mainly used as a fertilizer, due to its nitrogen supply, and it is also used as an explosive.

Molar mass of ammonium nitrate

To calculate the molecular mass, we only have to add all the atomic masses of the elements that make up the compound

We will have:


In the case of hydrogen, 4 means that there are 4 hydrogens, therefore we multiply the value of its atomic mass by 4, the same in oxygen


80 g/mol


How to make ammonium nitrate

Ammonium nitrate can be obtained by neutralizing nitric acid with ammonia, according to the following reaction:

NH 3 + HNO 3 = NH 4 NO 3

This reaction is exothermic and instantaneous. The heat produced in the reaction depends on the concentration of nitric acid used and ammonium nitrate, higher concentrations of the reagents will produce more heat of reaction. This generated heat can be used to evaporate the water from the solution.

The production of ammonium nitrate from the neutralization of nitric acid with ammonia, must be done under strict controls, to avoid explosions, burns and other accidents. The reactors in which the reaction occurs, the flow of ammonia and nitric acid is controlled by a valve system, so that the mixture of the same is as effective as possible. The pH and reaction temperature are regulated, to avoid overheating and volatilization or decomposition of the reagents.

Ammonium nitrate uses and Applications

Ammonium nitrate in combination with an oil derivative, gives rise to an explosive called ANFO (ammonium nitrate fuel oil), which has been used in terrorist attacks, for example the attack on AMIA in Argentina in 1994, among others . ANFO is also used by mining companies or demolition companies, since it is a very cheap, easy to get and quite safe explosive. The ratio of ammonium nitrate and petroleum derivative is variable, but is generally in the range of 90 to 97% ammonium nitrate and 3 to 10% kerosene or other derivative.

Ammonium nitrate is used primarily as a fertilizer for its good nitrogen content. Nitrate is used directly by plants, while ammonium is oxidized by microorganisms in the soil to nitrite or nitrate and serves as a longer-lasting fertilizer.

A part of the ammonium nitrate produced is transformed to nitrous oxide, through the application of heat.

NH 4 NO 3 = 2 H 2 O + N 2 O

This reaction must be very controlled, it is exothermic and can be explosive if heat is supplied too quickly or if it is carried out in an airtight container. Various accidents have occurred in factories of nitrogenous compounds and in boats that transported them, causing injuries and deaths.

Agricultural use

It is a popular fertilizer. Nitrate easily moves with water from the soil to the roots, where it is immediately available for absorption by plants. The ammonium fraction is absorbed by the roots or gradually converted to nitrate by soil microorganisms. Many vegetable growers prefer an immediately available source of nitrate for plant nutrition and use ammonium nitrate. Ranchers like it for pasture and hay fertilization as it is less susceptible to volatilization losses than urea-based fertilizers when left on the soil surface.


Ammonium nitrate is commonly mixed with other fertilizers , but these mixtures cannot be stored for long periods due to a tendency to absorb moisture from the air. The very high solubility of ammonium nitrate makes it very suitable for making solutions for fertigation or foliar sprays.

Management practices

It is also very soluble in the soil, and the nitrate portion can move beyond the root zone in wet conditions. Nitrate can also be converted to nitrous oxide gas in very humid conditions through the denitrification process. The ammonium portion is not subject to considerable loss until it oxidizes to nitrate.

Concern about the illegal use of this fertilizer for explosives has caused strict government regulation in many parts of the world. Restrictions on sales and transportation have caused some fertilizer distributors to stop handling this material.

Ammonium nitrate in explosives

A low-density form of compressed ammonium nitrate is widely used as an explosive in the mining industry and on construction sites.

Other uses

Instant cold compresses are made with two bags: one containing dry ammonium nitrate and the second containing water. When the barrier separating the bags is broken, it dissolves quickly in an endothermic reaction, reducing the temperature of the container to 2 or 3 degrees Celsius in a very short time.

Liquid ammonium nitrate

Liquid ammonium nitrate is white crystals dissolved in water. Although the material itself is non-combustible, it will accelerate the combustion of combustible materials. Toxic nitrogen oxides are produced in fires involving this material. It is used to make fertilizers and explosives.

Calcium ammonium nitrate

The BASF process is distinguished by using a by-product of the manufacture of phosphate fertilizers, calcium nitrate following the reaction:
Ca (NO 3 ) 2 , 4 H 2 O + 2 NH 3 + CO 2 —— > 2 NH 4 NO 3 + CaCO 3 + 3 H 2 O

It is a strong oxidizer. Molten nitrate oxidizes metals like zinc and lead which dissolve under its action. Metallic impurities like copper accelerate its decomposition. It partially vaporizes before melting and decomposes at 185 ° C:
NH 4 NO 3 ——> N 2 O + H 2 O

The reaction is slightly different when it detonates:
NH 4 NO 3 ——> 2N 2 + 4H 2 O + O 2

Ceric ammonium nitrate test

Ceric ammonium nitrate test

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