Names | |
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IUPAC name Ammonium nitrate | |
Identifiers | |
3D model (JSmol) | |
ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.026.680 |
EC Number |
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PubChem CID | |
RTECS number |
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UNII | |
UN number | 0222 – with > 0.2% combustible substances 1942 – with ≤ 0.2% combustible substances 2067 – fertilizers 2426 – liquid |
CompTox Dashboard (EPA) | |
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Properties | |
NH4NO3 | |
Molar mass | 80.043 g/mol |
Appearance | white crystalline solid |
Density | 1.725 g/cm3 (20 °C) |
Melting point | 169.6 °C (337.3 °F; 442.8 K) |
Boiling point | approx.210 °C (410 °F; 483 K) decomposes |
Endothermic 118 g/100 ml (0 °C) 150 g/100 ml (10 °C) 192 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] | |
−33.6×10−6 cm3/mol | |
Structure | |
orthorhombic [2] | |
Explosive data | |
Shock sensitivity | very low |
Friction sensitivity | very low |
Detonation velocity | 2500 m/s |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards | Explosive, Oxidizer |
GHS labelling: | |
Danger | |
H201, H271, H319 | |
P220, P221, P264, P271, P280, P372 | |
NFPA 704 (fire diamond) | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 2085–5300 mg/kg (oral in rats, mice) [3] |
Related compounds | |
Other anions | Ammonium nitrite |
Other cations | Sodium nitrate Potassium nitrate Hydroxylammonium nitrate |
Related compounds | Ammonium perchlorate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Ammonium nitrate is a chemical compound with the formula NH4NO3. It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is predominantly used in agriculture as a high-nitrogen fertilizer. [5]
Its other major use is as a component of explosive mixtures used in mining, quarrying, and civil construction. It is the major constituent of ANFO, a popular industrial explosive which accounts for 80% of explosives used in North America; similar formulations have been used in improvised explosive devices.
Many countries are phasing out its use in consumer applications due to concerns over its potential for misuse. [6] Accidental ammonium nitrate explosions have killed thousands of people since the early 20th century. [6] [7] Global production was estimated at 21.6 million tonnes in 2017. [8] By 2021, global production of ammonium nitrate was down to 16.7 million tonnes. [7]
Ammonium nitrate is found as the natural mineral gwihabaite (formerly known as nitrammite) [9] – the ammonium analogue of saltpetre (mineralogical name: niter) [10] [11] – in the driest regions of the Atacama Desert in Chile, often as a crust on the ground or in conjunction with other nitrate, iodate, and halide minerals. Ammonium nitrate was mined there until the Haber–Bosch process made it possible to synthesize nitrates from atmospheric nitrogen, thus rendering nitrate mining obsolete.
The industrial production of ammonium nitrate entails the acid-base reaction of ammonia with nitric acid: [12]
The ammonia required for this process is obtained by the Haber process from nitrogen and hydrogen. Ammonia produced by the Haber process can be oxidized to nitric acid by the Ostwald process. Ammonia is used in its anhydrous form (a gas) and the nitric acid is concentrated. The reaction is violent owing to its highly exothermic nature. After the solution is formed, typically at about 83% concentration, the excess water is evaporated off to leave 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.
Another production method is a variant of the nitrophosphate process:
The products, calcium carbonate and ammonium nitrate, may be separately purified or sold combined as calcium ammonium nitrate.
Ammonium nitrate can also be made via metathesis reactions:
As ammonium nitrate is a salt, both the cation, NH+4, and the anion, NO−3, may take part in chemical reactions.
Solid ammonium nitrate decomposes on heating. At temperatures below around 300 °C, the decomposition mainly produces nitrous oxide and water:
At higher temperatures, the following reaction predominates. [13]
Both decomposition reactions are exothermic and their products are gas. Under certain conditions, this can lead to a runaway reaction, with the decomposition process becoming explosive. [14] See § Disasters for details. Many ammonium nitrate disasters, with loss of lives, have occurred.
The red–orange colour in an explosion cloud is due to nitrogen dioxide, a secondary reaction product. [14]
A number of crystalline phases of ammonium nitrate have been observed. The following occur under atmospheric pressure.
Phase | Temperature (°C) | Symmetry |
---|---|---|
(liquid) | (above 169.6) | |
I | 169.6 to 125.2 | cubic |
II | 125.2 to 84.2 | tetragonal |
III | 84.2 to 32.3 | α-rhombic |
IV | 32.3 to −16.8 | β-rhombic |
V | below −16.8 | tetragonal [15] |
The transition between β-rhombic to α-rhombic forms (at 32.3 °C) occurs at ambient temperature in many parts of the world. These forms have a 3.6% difference in density and hence transition between them causes a change in volume. One practical consequence of this is that ammonium nitrate cannot be used as a solid rocket motor propellant, as it develops cracks. Stabilized ammonium nitrate (PSAN) was developed as a solution to this and incorporates metal halides stabilisers, which prevent density fluctuations. [16]
Ammonium nitrate is an important fertilizer with NPK rating 34-0-0 (34% nitrogen). [17] It is less concentrated than urea (46-0-0), giving ammonium nitrate a slight transportation disadvantage. Ammonium nitrate's advantage over urea is that it is more stable and does not rapidly lose nitrogen to the atmosphere.
Ammonium nitrate readily forms explosive mixtures with varying properties when combined with explosives such as TNT or with fuels like aluminum powder or fuel oil. Examples of explosives containing ammonium nitrate include:
ANFO is a mixture of 94% ammonium nitrate ("AN") and 6% fuel oil ("FO") widely used as a bulk industrial explosive. [18] : 1 It is used in coal mining, quarrying, metal mining, and civil construction in undemanding applications where the advantages of ANFO's low cost, relative safety, and ease of use matter more than the benefits offered by conventional industrial explosives, such as water resistance, oxygen balance, high detonation velocity, and performance in small diameters. [18] : 2
Ammonium nitrate-based explosives were used in the Sterling Hall bombing in Madison, Wisconsin, 1970, the Oklahoma City bombing in 1995, the 2011 Delhi bombings, the 2011 bombing in Oslo, the Myyrmanni bombing and the 2013 Hyderabad blasts.
In November 2009, the government of the North West Frontier Province (NWFP) of Pakistan imposed a ban on ammonium sulfate, ammonium nitrate, and calcium ammonium nitrate fertilizers in the former Malakand Division –comprising the Upper Dir, Lower Dir, Swat, Chitral, and Malakand districts of the NWFP – following reports that those chemicals were used by militants to make explosives. Due to these bans, "Potassium chlorate –the material which allows safety matches to catch fire –has surpassed fertilizer as the explosive of choice for insurgents." [19]
Ammonium nitrate is used in some instant cold packs, as its dissolution in water is highly endothermic. In 2021, King Abdullah University of Science and Technology in Saudi Arabia conducted experiments to study the potential for dissolving ammonium nitrate in water for off-grid cooling systems and as a refrigerant. They suggested that the water could be distilled and reused using solar energy to avoid water wastage in severe environments. [20]
It was once used, in combination with independently explosive "fuels" such as guanidine nitrate, [21] [22] as a cheaper (but less stable) alternative to 5-aminotetrazole in the inflators of airbags manufactured by Takata Corporation, which were recalled as unsafe after killing 14 people. [23] The current USA death total is 27. [24]
Numerous safety guidelines are available for storing and handling ammonium nitrate. Health and safety data are shown on the safety data sheets available from suppliers and from various governments. [25] [26] [27]
Pure ammonium nitrate does not burn, but as a strong oxidizer, it supports and accelerates the combustion of organic (and some inorganic) material. [25] [28] [29] It should not be stored near combustible substances.
While ammonium nitrate is stable at ambient temperature and pressure under many conditions, it may detonate from a strong initiation charge. It should not be stored near high explosives or blasting agents.
Molten ammonium nitrate is very sensitive to shock and detonation, particularly if it becomes contaminated with incompatible materials such as combustibles, flammable liquids, acids, chlorates, chlorides, sulfur, metals, charcoal and sawdust. [30] [25]
Contact with certain substances such as chlorates, mineral acids and metal sulfides, can lead to vigorous or even violent decomposition capable of igniting nearby combustible material or detonating. [31] [32]
Ammonium nitrate begins decomposition after melting, releasing NOx, HNO3, NH
3 and H2O. It should not be heated in a confined space. [25] The resulting heat and pressure from decomposition increases the sensitivity to detonation and increases the speed of decomposition. Detonation may occur at 80 atmospheres. Contamination can reduce this to 20 atmospheres. [30]
Ammonium nitrate has a critical relative humidity of 59.4% at 30 °C. At higher humidity it will absorb moisture from the atmosphere. Therefore, it is important to store ammonium nitrate in a tightly sealed container. Otherwise, it can coalesce into a large, solid mass. Ammonium nitrate can absorb enough moisture to liquefy. Blending ammonium nitrate with certain other fertilizers can lower the critical relative humidity. [33]
The potential for use of the material as an explosive has prompted regulatory measures. For example, in Australia, the Dangerous Goods Regulations came into effect in August 2005 to enforce licensing in dealing with such substances. [34] Licenses are granted only to applicants (industry) with appropriate security measures in place to prevent any misuse. [35] 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.
Ammonium nitrate is not hazardous to health and is usually used in fertilizer products. [36] [37] [38]
Ammonium nitrate has an LD50 of 2217 mg/kg, [39] which for comparison is about two-thirds that of table salt.
Ammonium nitrate decomposes, non-explosively, into the gases nitrous oxide and water vapor when heated. However, it can be induced to decompose explosively by detonation. [40] Large stockpiles of the material can also be a major fire risk due to their supporting oxidation, a situation which can easily escalate to detonation. Explosions are not uncommon: relatively minor incidents occur most years, and several large and devastating explosions have also occurred. Examples include the Oppau explosion of 1921 (one of the largest artificial non-nuclear explosions), the Texas City disaster of 1947, the 2015 Tianjin explosions in China, and the 2020 Beirut explosion. [41]
Ammonium nitrate can explode through two mechanisms:
An explosive is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An explosive charge is a measured quantity of explosive material, which may either be composed solely of one ingredient or be a mixture containing at least two substances.
Nitrate is a polyatomic ion with the chemical formula NO−
3. Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insoluble nitrate is bismuth oxynitrate.
Nitric acid is the inorganic compound with the formula HNO3. It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% HNO3, it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%.
Trinitrotoluene, more commonly known as TNT (and more specifically 2,4,6-trinitrotoluene), and by its preferred IUPAC name 2-methyl-1,3,5-trinitrobenzene, is a chemical compound with the formula C6H2(NO2)3CH3. TNT is occasionally used as a reagent in chemical synthesis, but it is best known as an explosive material with convenient handling properties. The explosive yield of TNT is considered to be the standard comparative convention of bombs and asteroid impacts. In chemistry, TNT is used to generate charge transfer salts.
ANFO ( AN-foh) (or AN/FO, for ammonium nitrate/fuel oil) is a widely used bulk industrial high explosive. It consists of 94% porous prilled ammonium nitrate (NH4NO3) (AN), which acts as the oxidizing agent and absorbent for the fuel, and 6% number 2 fuel oil (FO). The use of ANFO originated in the 1950s.
Sodium nitrate is the chemical compound with the formula NaNO
3. This alkali metal nitrate salt is also known as Chile saltpeter to distinguish it from ordinary saltpeter, potassium nitrate. The mineral form is also known as nitratine, nitratite or soda niter.
Nitromethane, sometimes shortened to simply "nitro", is an organic compound with the chemical formula CH
3NO
2. It is the simplest organic nitro compound. It is a polar liquid commonly used as a solvent in a variety of industrial applications such as in extractions, as a reaction medium, and as a cleaning solvent. As an intermediate in organic synthesis, it is used widely in the manufacture of pesticides, explosives, fibers, and coatings. Nitromethane is used as a fuel additive in various motorsports and hobbies, e.g. Top Fuel drag racing and miniature internal combustion engines in radio control, control line and free flight model aircraft.
Dinitrogen pentoxide is the chemical compound with the formula N2O5. It is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It exists as colourless crystals that sublime slightly above room temperature, yielding a colorless gas.
Ammonal is an explosive made up of ammonium nitrate and aluminium powder, not to be confused with T-ammonal which contains trinitrotoluene as well to increase properties such as brisance. The mixture is often referred to as Tannerite, which is a brand of ammonal.
Calcium nitrate are inorganic compounds with the formula Ca(NO3)2(H2O)x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the tetrahydrate. Both anhydrous and hydrated forms are colourless salts. Hydrated calcium nitrate, also called Norgessalpeter (Norwegian salpeter), is mainly used as a component in fertilizers, but it has other applications. Nitrocalcite is the name for a mineral which is a hydrated calcium nitrate that forms as an efflorescence where manure contacts concrete or limestone in a dry environment as in stables or caverns. A variety of related salts are known including calcium ammonium nitrate decahydrate and calcium potassium nitrate decahydrate.
Guanidine nitrate is the chemical compound with the formula [C(NH2)3]NO3. It is a colorless, water-soluble salt. It is produced on a large scale and finds use as precursor for nitroguanidine, fuel in pyrotechnics and gas generators. Its correct name is guanidinium nitrate, but the colloquial term guanidine nitrate is widely used.
Nitroguanidine - sometimes abbreviated NGu - is a colorless, crystalline solid that melts at 257 °C and decomposes at 254 °C. Nitroguanidine is an extremely insensitive but powerful high explosive. Wetting it with > 20 wt.-% water effects desensitization from HD 1.1 down to HD 4.1 . Nitroguanidine is used as an energetic material, i.e., propellant or high explosive, precursor for insecticides, and for other purposes.
Potassium nitrite (distinct from potassium nitrate) is the inorganic compound with the chemical formula KNO2. It is an ionic salt of potassium ions K+ and nitrite ions NO2−, which forms a white or slightly yellow, hygroscopic crystalline powder that is soluble in water.
The Oppau explosion occurred on September 21, 1921, when approximately 4,500 metric tons of a mixture of ammonium sulfate and ammonium nitrate fertilizer stored in a tower silo exploded at a BASF plant in Oppau, now part of Ludwigshafen, Germany, killing 500–600 people and injuring about 2,000 more.
Tovex is a water-gel explosive composed of ammonium nitrate and methylammonium nitrate that has several advantages over traditional dynamite, including lower toxicity and safer manufacture, transport, and storage. It has thus almost entirely replaced dynamite. There are numerous versions ranging from shearing charges to aluminized common blasting agents. Tovex is used by 80% of international oil companies for seismic exploration.
Urea nitrate is a fertilizer-based high explosive that has been used in improvised explosive devices in Afghanistan, Pakistan, Iraq, and various terrorist acts elsewhere in the world such as in the 1993 World Trade Center bombings. It has a destructive power similar to better-known ammonium nitrate explosives, with a velocity of detonation between 3,400 m/s (11,155 ft/s) and 4,700 m/s (15,420 ft/s). It has chemical formula of CH5N3O4 or (NH2)2COHNO3.
Methylammonium nitrate is an explosive chemical with the molecular formula CH6N2O3, alternately CH3NH3+NO3−. It is the salt formed by the neutralization of methylamine with nitric acid. This substance is also known as methylamine nitrate and monomethylamine nitrate, not to be confused with methyl nitramine or monomethyl nitramine.
Sable Chemical Industries Limited is the sole manufacturer of ammonium nitrate (NH4NO3) in Zimbabwe.
Calcium ammonium nitrate or CAN, also known as nitro-limestone or nitrochalk, is a widely used inorganic fertilizer, accounting for 4% of all nitrogen fertilizer used worldwide in 2007.
Aoun, in remarks published on the Presidency Twitter account, said it was "unacceptable" that 2,750 tonnes of ammonium nitrate was stored in a warehouse for six years without safety measures and vowed that those responsible would face the "harshest punishments".