## Ammonium nitrate

**Formula**

$NH4NO3$

**Pyrotechnic use**

Oxidiser

**Synonyms**

ammonia nitre

**Description**

Ammonium nitrate is an oxidiser. It is very hygroscopic and therefore not used
very often in fireworks. It finds some use in composite propellants, but
performance is not as good as perchlorate-based propellants.

**Sources**

Ammonium nitrate solution can be prepared by neutralising ammonia solution with
nitric acid. It is advised to use a slight excess of ammonia. That is to make
sure no remaining acid will be present in the ammonium nitrate obtained on
evaporation and crystallisation. Otherwise traces of the acid solution may be
enclosed in the crystals, possibly leading to spontaneous ignition of mixtures
made with it. Large quantities of ammonium nitrate can also be cheaply bought
as fertilizer. ammonium nitrate can be extracted from ferilizer with water
leaving the ammonium sulfate(solid) behind. Ammonium nitrate can also be found
as the active agent in instant cold packs.

**Hazards**

Large masses of ammonium nitrate have been known to explode on some occasions
although it is very insensitive. Smaller quantities are less likely to
detonate. The risk of detonation increases when ammonium nitrate is molten or
mixed with fuels such as metal powders or organic substances. Ammonium nitrate
should never be mixed with chlorates as this may result in ammonium chlorate
formation, possibly leading to spontaneous ignition. Mixtures of metal powders
and ammonium nitrate are likely to heat up spontaneously and may ignite,
especially when moist. This can sometimes be prevented by the addition of small
amounts of boric acid (1 to 2%), but in general it is better to avoid these
mixtures at all. The hygroscopic nature of ammonium nitrates makes this problem
worse (also see aluminium). Toxicity: Oral rat LD50: 2217 mg/kg
