- Ammonium nitrate
Ammonium nitrate Identifiers CAS number ChemSpider UNII UN number 0222 – with > 0.2% combustible substances
1942 – with <= 0.2% combustible substances
2067 – fertilizers
2426 – liquid
RTECS number BR9050000 Jmol-3D images Image 1 Properties Molecular formula (NH4)(NO3) Molar mass 80.052 g/mol Appearance white solid Density 1.725 g/cm3 (20 °C) Melting point
approx. 210 °C decomp.
Solubility in water 118 g/100 ml (0 °C)
150 g/100 ml (20 °C)
297 g/100 ml (40 °C)
410 g/100 ml (60 °C)
576 g/100 ml (80 °C)
1024 g/100 ml (100 °C) 
Structure Crystal structure trigonal Explosive data Shock sensitivity very low Friction sensitivity very low Explosive velocity 5270 m/s Hazards MSDS ICSC 0216 EU Index not listed Main hazards Explosive NFPA 704 LD50 2085–5300 mg/kg (oral in rats, mice) Related compounds Other anions Ammonium nitrite Other cations Sodium nitrate
Related compounds Ammonium perchlorate (what is: /?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
The chemical compound ammonium nitrate, the nitrate of ammonia with the chemical formula NH4NO3, is a white crystalline solid at room temperature and standard pressure. It is commonly used in agriculture as a high-nitrogen fertilizer, and it has also been used as an oxidizing agent in explosives, including improvised explosive devices. It is the main component of ANFO, a very popular explosive. It is used in instant cold packs, as hydrating the salt is an endothermic process.
Heating or any ignition source may cause violent combustion or explosion. Ammonium nitrate reacts with combustible and reducing materials as it is a strong oxidant. It is widely used in fertilizers and explosives. Ammonium nitrates are also used to modify the detonation rate of other explosives. Example will be ammonia dynamites (Nitroglycerin).
The increased level of misuse by terrorists prompted the need to change how these substances should be dealt with. For example in Australia, the Dangerous Goods Regulations came into effect in August 2005 to enforce licensing in dealing with such substances. Licenses are only granted to applicants (industry) with appropriate security measures in place to prevent any misuse. Additional uses such as education and research purposes may also be considered but individual use will not. Employees of those with licenses to deal with the substance are still required to be supervised by authorized personnel and are required to pass a security and national police check before a license may be granted.
The processes involved in the production of ammonium nitrate in industry, although chemically simple, are technologically challenging. The acid-base reaction of ammonia with nitric acid gives a solution of ammonium nitrate:
- HNO3(aq) + NH3(l) → NH4NO3(aq)
For industrial production, this is done using anhydrous ammonia gas and concentrated nitric acid. This reaction is violent and very exothermic. After the solution is formed, typically at about 83% concentration, the excess water is evaporated to an ammonium nitrate (AN) content of 95% to 99.9% concentration (AN melt), depending on grade. The AN melt is then made into "prills" or small beads in a spray tower, or into granules by spraying and tumbling in a rotating drum. The prills or granules may be further dried, cooled, and then coated to prevent caking. These prills or granules are the typical AN products in commerce.
The Haber process combines nitrogen and hydrogen to produce ammonia, part of which can be oxidized to nitric acid and combined with the remaining ammonia to produce the nitrate. Another production method is used in the so-called Odda process.
Ammonium nitrate is also manufactured by amateur explosive enthusiasts by metathesis reactions:
- (NH4)2SO4 + 2 NaNO3 → Na2SO4 + 2 NH4NO3
- Ca(NO3)2 + (NH4)2SO4 → 2 NH4NO3 + CaSO4
Sodium sulfate is removed by lowering the temperature of the mixture. Since sodium sulfate is much less water-soluble than ammonium nitrate, it precipitates, and may be filtered off. For the reaction with calcium nitrate, the calcium sulfate generated is quite insoluble, even at room temperature.
Ammonium nitrate reacts with alkali metal hydroxides, releasing ammonia and forming alkali metal nitrate:
- NH4NO3 + NaOH → NH3 + H2O + NaNO3
- NH4NO3 + KOH → NH3 + H2O + KNO3
- NH4NO3 + HCl → NH4Cl + HNO3
Ammonium nitrate is also formed in the atmosphere from emissions of NO, SO2 and NH3 and is a secondary component of PM10. 
Transformations of the crystal states due to changing conditions (temperature, pressure) affect the physical properties of ammonium nitrate. The following crystalline states have been identified:
System Temperature (°C) State Volume Change (%) - >169.6 liquid - I 169.6 to 125.2 cubic +2.1 II 125.2 to 84.2 tetragonal -1.3 III 84.2 to 32.3 α-rhombic +3.6 IV 32.3 to −16.8 β-rhombic −2.9 V −16.8 tetragonal -
The type V crystal is a quasi-cubic form which is related to caesium chloride, the nitrogens of the nitrates and the ammoniums are at the sites in a cubic array where Cs and Cl would be in the CsCl lattice. See C.S. Choi and H.J. Prask, Acta Crystallographica B, 1983, 39, 414-420.
Ammonium Nitrate is not an extreme hazardous chemical, and usually used in fertilizer products. Thus, the chances of direct personal exposure to the chemical are very low.
Acute health effects
Area of exposure Hazardous level Ingestion Moderate Hazardous Skin contact Moderate Hazardous (irritant) Eye contact Moderate Hazardous Inhalation Moderate Hazardous
Long-term health effects
No data suggest that there are any chronic effects with long-term exposure.
Types of effect Effect level Carcinogenic effects None Mutagenic effects None Teratogenic effects None Developmental toxicity None Prolonged exposure None
Ammonium nitrate decomposes into gases including oxygen and Nitrogen to make Nitrous oxide when heated (non-explosive reaction); however, ammonium nitrate can be induced to decompose explosively by detonation. Large stockpiles of the material can be a major fire risk due to their supporting oxidation, and may also detonate, as happened in the Texas City disaster of 1947, which led to major changes in the regulations for storage and handling.
There are two major classes of incidents resulting in explosions:
- In the first case, the explosion happens by the mechanism of shock-to-detonation transition. The initiation happens by an explosive charge going off in the mass, by the detonation of a shell thrown into the mass, or by detonation of an explosive mixture in contact with the mass. The examples are Kriewald, Morgan (present-day Sayreville, New Jersey), Oppau and Tessenderlo.
- In the second case, the explosion results from a fire that spreads into the ammonium nitrate itself (Texas City, Brest, Oakdale), or from a mixture of ammonium nitrate with a combustible material during the fire (Repauno, Cherokee, Nadadores). The fire must be confined at least to a degree for successful transition from a fire to an explosion (a phenomenon known as "deflagration-to-detonation transition", or DDT). Pure, compact AN is stable and very difficult to ignite, and there are numerous cases when even impure AN did not explode in a fire.
Ammonium nitrate decomposes in temperatures normally well above 200°C. However the presence of impurities (organic and/or inorganic) will often reduce the temperature point when heat is being generated. Once the AN has started to decompose, then a runaway reaction will normally occur as the heat of decomposition is very large. AN evolves so much heat that this runaway reaction is normally impossible to stop. This is a well-known hazard with some types of N-P-K Fertilizers, and it is responsible for the loss of several cargo ships.
Under normal handling conditions, ammonium nitrate is not harmful. However, inhalation of high concentrations of ammonium nitrate dust can cause respiratory tract irritation. Symptoms may include: coughing, sore throat, shortness of breath, or even suffocation. When swallowed in high concentrations, ammonium nitrate may cause headache, dizziness, abdominal pain, vomiting, bloody diarrhea, weakness, a tingling sensation, heart and circulation irregularities, convulsions, collapse, and suffocation. Ammonium nitrate forms a mild acid when mixed with water. This acid can cause irritation to the eyes, nose, and skin.
In November 2009, a ban on ammonium sulfate, ammonium nitrate, and calcium ammonium nitrate fertilizers was imposed in the former Malakand Division—comprising the Upper Dir, Lower Dir, Swat, Chitral, and Malakand districts of the North West Frontier Province (NWFP) of Pakistan—by the NWFP government, following reports that those chemicals were used by militants to make explosives. In January 2010, these substances were also banned in Afghanistan for the same reason.
- ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
- ^ Martel, B.; Cassidy, K. (2004). Chemical Risk Analysis: A Practical Handbook. Butterworth–Heinemann. pp. 362. ISBN 1-903996-65-1.
- ^ Pradyot Patnaik (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 0-07-049439-8.
- ^ Dangerous Goods (HCDG) Regulations
- ^ Ammonium Nitrate-Regulating its use, Balancing Access & Protection from "Worksafe Victoria". http://www.worksafe.vic.gov.au/wps/wcm/connect/wsinternet/worksafe/home/forms+and+publications/publications/import_ammonium+nitrate+-+regulating+its+use%2C+balancing+access+_+protection.
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- ^ Int Panis, LLR (2008). "The Effect of Changing Background Emissions on External Cost Estimates for Secondary Particulates". Open Environmental Sciences 2: 47–53. http://www.bentham.org/open/toenvirj/articles/V002/47TOENVIRSJ.pdf.
- ^ "Chemicalland21". http://chemicalland21.com/industrialchem/inorganic/ammonium%20nitrate.htm.
- ^ "Ammonium Nitrate". Paton Fertilizers Pty Ltd. 2005. Available from"Duralite". http://www.duralite.com.au/safety/AMMONIUM%20NITRATE.pdf.
- ^ Martel, B.; Cassidy, K. (2004). Chemical Risk Analysis: A Practical Handbook. Butterworth–Heinemann. ISBN 1-903996-65-1.
- ^ The Hazards and Dangers of Ammonium Nitrate [Ammonium Nitrate Dangers | http://www.nortechlabs.com/hazards-ammonium-nitrate.html]
- Properties: UNIDO and International Fertilizer Development Center (1998), Fertilizer Manual, Kluwer Academic Publishers, ISBN 0-7923-5032-4.
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