Ammonium nitrate

Ammonium nitrate is a chemical compound with the formula NH₄NO₃. It is a white, crystalline salt made of ammonium and nitrate ions. This compound dissolves easily in water and can absorb moisture from the air, but it does not form water-containing crystals.

People mainly use ammonium nitrate in agriculture as a high-nitrogen fertilizer, which helps plants grow. It also plays an important role in making explosive mixtures for mining, quarrying, and construction. In fact, it is the main ingredient in ANFO, an industrial explosive used widely in North America.

Because of worries about how it might be misused, many countries are stopping its use in products that ordinary people can buy. Sadly, accidental explosions involving ammonium nitrate have caused the deaths of many people since the early 1900s. In 2017, about 21.6 million tonnes of ammonium nitrate were made worldwide, but by 2021, production had dropped to 16.7 million tonnes.

Occurrence

Ammonium nitrate can be found as a natural mineral called gwihabaite in the very dry parts of the Atacama Desert in Chile. It often appears as a crust on the ground or mixed with other minerals. People used to mine it there, but now we can make it from air using a special process, so mining is no longer needed.

Production, reactions and crystalline phases

Ammonium nitrate is made when ammonia mixes with nitric acid. This creates a fast reaction that gives off heat. The result is turned into small beads or granules to make the final product.

When heated, ammonium nitrate breaks down and can produce gases. In some cases, this can cause a very fast reaction. There are different crystal forms of ammonium nitrate, and they change at certain temperatures. This change can affect how the material behaves, which is why special stabilizers are added to keep it stable.

Applications

Ammonium nitrate is commonly used as a fertilizer because it provides nitrogen, which plants need to grow. It is not as strong as some other fertilizers, but it stays useful for longer without losing its nitrogen to the air.

Ammonium nitrate can also be mixed with other materials to create explosives. These mixtures are used in mining and construction where cost and safety are important. Sadly, these materials have sometimes been misused in harmful ways.

It is also used in instant cold packs, where it creates a cooling effect when mixed with water. Scientists are exploring ways to use this property for cooling in places without reliable electricity.

Safety, handling, and storage

There are many safety rules for storing and handling ammonium nitrate. You can find health and safety information on special sheets provided by sellers and governments.

Ammonium nitrate does not catch fire by itself, but it can help other materials burn faster. It should be kept away from things that can catch fire. It is important to store it safely because, under certain conditions, it can explode if hit very hard. It should never be stored near explosives.

When heated, ammonium nitrate can break down and release gases like NO_x, HNO₃, NH₃, and H₂O. It should not be heated in a small, closed space. Keeping it dry is very important, as it can absorb moisture from the air and become a large solid block. Special rules exist in some places to prevent misuse of this material.

Health hazards

Ammonium nitrate is not dangerous to health and is often used in fertilizer products.

It has a level that shows how much a person would need to be exposed to before it might cause harm, which is about two-thirds of what is needed for table salt.