| Ammonium nitrate | |
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Ammonium nitrate |
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| Identifiers | |
| CAS number | 6484-52-2 |
| ChemSpider | 21511 |
| UNII | T8YA51M7Y6 |
| 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 |
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| Properties | |
| Molecular formula | (NH4)(NO3) |
| Molar mass | 80.052 g/mol |
| Appearance | white solid |
| Density | 1.725 g/cm3 (20 °C) |
| Melting point |
169.6 °C |
| Boiling 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) [1] |
| 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 |
0
2
3
OX
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| LD50 | 2085–5300 mg/kg (oral in rats, mice)[2] |
| Related compounds | |
| Other anions | Ammonium nitrite |
| Other cations | Sodium nitrate Potassium nitrate Hydroxylammonium nitrate |
| Related compounds | Ammonium perchlorate |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
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.
Contents |
Heating or any ignition source may cause violent combustion or explosion.[3] 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.[4] Licenses are granted only to applicants (industry) with appropriate security measures in place to prevent any misuse.[5] 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:[6]
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:
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:
Ammonium nitrate gives ammonium chloride and nitric acid upon reaction with hydrochloric acid:
Ammonium nitrate is also formed in the atmosphere from emissions of NO, SO2 and NH3 and is a secondary component of PM10. [7]
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[8], and usually used in fertilizer products. Thus, the chances of direct personal exposure to the chemical are very low.[9][10]
Ammonium nitrate has toxicity of 2217 mg/kg.[8]
Short-term exposure to ammonium nitrate can cause symptoms ranging from minor irritation to nausea, vomiting, gastric irritation, headaches, dizziness and hypertension.[11]
| Area of exposure | Hazardous level |
|---|---|
| Ingestion | Moderate Hazardous |
| Skin contact | Moderate Hazardous (irritant) |
| Eye contact | Moderate Hazardous |
| Inhalation | Moderate Hazardous |
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:
Ammonium-nitrate-based explosives were used in the Oklahoma City bombing and in the 2011 Delhi bombing and the bombing in Oslo 2011.
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.[12]
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.