View source for Ammonium nitrate

{{short description|Chemical compound with formula NH4NO3}}
{{Use dmy dates|date=August 2020}}
{{chembox
| Watchedfields = changed
| verifiedrevid = 476998591
| ImageFile = Ammonium-nitrate-2D.svg
| ImageAlt = Structural formula
| ImageName = Structural formula of ammonium cation (left) and nitrate anion (right)
| ImageFile1 = Ammonium-nitrate-xtal-3D-balls-A.png
| ImageAlt1 = Ammonium nitrate crystal structure
| ImageName1 = H=white, N=blue, O=red
| ImageFile2 = Ammonium_Nitrate.jpg
| ImageAlt2 = Sample of white powder and spherules
| IUPACName = Ammonium nitrate
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 21511
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = T8YA51M7Y6
| ChEBI = 63038
| ChEMBL = 1500032
| InChI = 1/NO3.H3N/c2-1(3)4;/h;1H3/q-1;/p+1
| InChIKey = DVARTQFDIMZBAA-IKLDFBCSAH
| SMILES = [O-][N+]([O-])=O.[NH4+]
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/NO3.H3N/c2-1(3)4;/h;1H3/q-1;/p+1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = DVARTQFDIMZBAA-UHFFFAOYSA-O
| CASNo = 6484-52-2
| CASNo_Ref = {{cascite|correct|CAS}}
| UNNumber = [[List of UN Numbers 0201 to 0300|0222]] – ''with > 0.2% combustible substances''<br/>[[List of UN Numbers 1901 to 2000|1942]] – ''with ≤ 0.2% combustible substances''<br/>[[List of UN Numbers 2001 to 2100|2067]] – ''fertilizers''<br/>[[List of UN Numbers 2401 to 2500|2426]] – ''liquid''
| RTECS = BR9050000
| PubChem = 22985
| EC_number = 229-347-8
  }}
|Section2={{Chembox Properties
| Formula = NH<sub>4</sub>NO<sub>3</sub> 
| MolarMass = 80.043&nbsp;g/mol
| Appearance = white crystalline solid
| Density = 1.725 g/cm<sup>3</sup> (20&nbsp;°C)
| Solubility = Endothermic<br/>118 g/100 ml (0&nbsp;°C)<br/>150 g/100 ml (10&nbsp;°C)<br/>192 g/100 ml (20&nbsp;°C)<br/>297 g/100 ml (40&nbsp;°C)<br/>410 g/100 ml (60&nbsp;°C)<br/>576 g/100 ml (80&nbsp;°C)<br/>1024 g/100 ml (100&nbsp;°C)<ref>Pradyot Patnaik. ''Handbook of Inorganic Chemicals''. McGraw-Hill, 2002, {{ISBN|0-07-049439-8}}</ref>
| MeltingPtC = 169.6
| MeltingPt_notes = 
| BoilingPt  = ''approx.''
| BoilingPtC = 210
|BoilingPt_notes = decomposes
| MagSus = {{val|-33.6e-6|u=cm<sup>3</sup>/mol}}
  }}
|Section3={{Chembox Structure
| Coordination =
| CrystalStruct = [[orthorhombic crystal system|orthorhombic]]<ref>{{Cite journal |last1=Kaniewski |first1=Maciej |last2=Huculak-Mączka |first2=Marta |last3=Zieliński |first3=Jakub |last4=Biegun |first4=Marcin |last5=Hoffmann |first5=Krystyna |last6=Hoffmann |first6=Józef |date=2021 |title=Crystalline Phase Transitions and Reactivity of Ammonium Nitrate in Systems Containing Selected Carbonate Salts |journal=Crystals |language=en |volume=11 |issue=10 |pages=1250 |doi=10.3390/cryst11101250 |doi-access=free |issn=2073-4352}}</ref>
  }}
|Section6={{Chembox Explosive
| ShockSens = very low
| FrictionSens = very low
| DetonationV = 2500 [[metre per second|m/s]]
| REFactor = }}
|Section7={{Chembox Hazards
| GHSPictograms = {{GHS07}} {{GHS03}} {{GHS01}}
| GHSSignalWord = '''Danger'''
| HPhrases = {{H-phrases|201|271|319}}
| PPhrases = {{P-phrases|220|221|271|280|264|372}}
| MainHazards = Explosive, Oxidizer
| NFPA-H = 1
| NFPA-F = 0
| NFPA-R = 3
| NFPA-S = OX
| LD50 = 2085–5300&nbsp;mg/kg (oral in rats, mice)<ref>{{cite book |author1=Martel, B. |author2=Cassidy, K. |title=Chemical Risk Analysis: A Practical Handbook |publisher=Butterworth–Heinemann |year=2004 |page=362 |isbn=1-903996-65-1}}</ref>
  }}<ref>{{cite web|url=http://www.ehs.neu.edu/laboratory_safety/general_information/nfpa_hazard_rating/documents/NFPAratingAC.htm |title=Hazard Rating Information for NFPA Fire Diamonds |access-date=13 March 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150217114736/http://www.ehs.neu.edu/laboratory_safety/general_information/nfpa_hazard_rating/documents/NFPAratingAC.htm |archive-date=17 February 2015 }}</ref>
|Section8={{Chembox Related
| OtherAnions = [[Ammonium nitrite]]
| OtherCations = [[Sodium nitrate]]<br/>[[Potassium nitrate]]<br/>[[Hydroxylammonium nitrate]]
| OtherCompounds = [[Ammonium perchlorate]]
  }}
}}

'''Ammonium nitrate''' is a [[chemical compound]] with the formula {{Chem2|NH4NO3}}. It is a white crystalline salt consisting of [[ion]]s of [[ammonium]] and [[nitrate]]. It is highly soluble in water and [[hygroscopic]] as a solid, although it does not form [[Water of crystallization|hydrates]]. It is predominantly used in [[agriculture]] as a high-nitrogen [[fertilizer]].<ref name=Ullmann>{{cite encyclopedia|first=Karl-Heinz |last=Zapp |title=Ammonium Compounds |encyclopedia=[[Ullmann's Encyclopedia of Industrial Chemistry]] |year=2012 |publisher=Wiley-VCH |location=Weinheim |doi=10.1002/14356007.a02_243|isbn=9783527303854 }}</ref>

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 device]]s. 

Many countries are phasing out its use in consumer applications due to concerns over its potential for misuse.<ref name=Dallas>[https://www.dallasnews.com/news/news/2013/10/05/ammonium-nitrate-sold-by-ton-as-u.s.-regulation-is-stymied Ammonium nitrate sold by ton as U.S. regulation is stymied.] {{Webarchive|url=https://web.archive.org/web/20180228041244/https://www.dallasnews.com/news/news/2013/10/05/ammonium-nitrate-sold-by-ton-as-u.s.-regulation-is-stymied |date=28 February 2018 }} – [[The Dallas Morning News]]</ref> [[List of ammonium nitrate incidents and disasters|Accidental ammonium nitrate explosions]] have killed thousands of people since the early 20th century.<ref name=Dallas /><ref name="auto">{{Cite web|url=https://knoema.com//atlas/topics/Agriculture/Fertilizers-Production-Quantity-in-Nutrients/Ammonium-nitrate-production|title=Ammonium nitrate production by country, 2023 - knoema.com|website=Knoema}}</ref> Global production was estimated at 21.6&nbsp;million tonnes in 2017.<ref>{{cite web|title=Ammonium nitrate production by country, 2019|url=https://knoema.com//atlas/topics/Agriculture/Fertilizers-Production-Quantity-in-Nutrients/Ammonium-nitrate-production|access-date=2020-08-14|website=Knoema|language=en-US}}</ref> By 2021, global production of ammonium nitrate was down to 16.7 million tonnes.<ref name="auto"/>

==Occurrence==
Ammonium nitrate is found as the natural mineral [[gwihabaite]] (formerly known as nitrammite)<ref>{{cite web|url=https://www.mindat.org/min-6983.html|title=Gwihabaite|website=www.mindat.org}}</ref> – the ammonium analogue of [[nitre|saltpetre]] (mineralogical name: niter)<ref>{{cite web|url=https://www.mindat.org/min-2917.html|title=Niter|website=www.mindat.org}}</ref><ref>{{cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=21 March 2011|website=www.ima-mineralogy.org}}</ref> – 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 process|Haber–Bosch process]] made it possible to synthesize nitrates from atmospheric nitrogen, thus rendering nitrate mining obsolete.

==Production, reactions and crystalline phases==
The industrial production of ammonium nitrate entails the [[acid-base reaction theories|acid-base reaction]] of [[ammonia]] with [[nitric acid]]:<ref>{{cite patent |country=US|number=4927617|title=Process of producing concentrated solutions of ammonium nitrate|pubdate=1990-05-22|inventor1-last=Villard|inventor2-first=Yves|inventor2-last=Cotonea|inventor1-first=Alexandre|assign= Societe Chimique des Charbonnages S.A.}}</ref>
:HNO<sub>3</sub> + NH<sub>3</sub> → NH<sub>4</sub>NO<sub>3</sub>
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]]:

:[[calcium nitrate|Ca(NO<sub>3</sub>)<sub>2</sub>]] +  [[ammonia|2 NH<sub>3</sub>]] + [[carbon dioxide|CO<sub>2</sub>]] + H<sub>2</sub>O → 2 NH<sub>4</sub>NO<sub>3</sub> + CaCO<sub>3</sub>

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 [[Salt metathesis reaction|metathesis reaction]]s:
:[[ammonium sulfate|(NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>]] + [[barium nitrate|Ba(NO<sub>3</sub>)<sub>2</sub>]] → 2 NH<sub>4</sub>NO<sub>3</sub> + [[barium sulfate|BaSO<sub>4</sub>]]
:[[Ammonium sulfate|(NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>]] + [[Calcium nitrate|Ca(NO<sub>3</sub>)<sub>2</sub>]] → 2 NH<sub>4</sub>NO<sub>3</sub> + [[Calcium sulfate|CaSO<sub>4</sub>]]
:[[ammonium chloride|NH<sub>4</sub>Cl]] + [[silver nitrate|AgNO<sub>3</sub>]] → NH<sub>4</sub>NO<sub>3</sub> + [[silver chloride|AgCl]]
===Reactions===
As ammonium nitrate is a [[salt (chemistry)|salt]], both the cation, {{chem2|NH4+}}, and the anion, {{chem2|NO3-}}, may take part in chemical reactions. 

Solid ammonium nitrate decomposes on heating. At temperatures below around 300&nbsp;°C, the decomposition mainly produces [[nitrous oxide]] and water:

: NH<sub>4</sub>NO<sub>3</sub> → N<sub>2</sub>O + 2 H<sub>2</sub>O

At higher temperatures, the following reaction predominates.<ref>{{Greenwood&Earnshaw2nd|page=469}}</ref>

: 2 NH<sub>4</sub>NO<sub>3</sub> → 2 N<sub>2</sub> + O<sub>2</sub> + 4 H<sub>2</sub>O

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.<ref name="CEN"/> See {{section link||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.<ref name="CEN">{{Cite web|url=https://cen.acs.org/safety/industrial-safety/chemistry-behind-Beirut-explosion/98/web/2020/08|title=The chemistry behind the Beirut explosion|website=Chemical & Engineering News}}</ref>

===Crystalline phases===
A number of crystalline phases of ammonium nitrate have been observed. The following occur under atmospheric pressure. 

:{| class="wikitable"
|-
! Phase
! Temperature (°C)
! Symmetry
|-
| (liquid)
| (above 169.6) 
| 
|-
| I
| 169.6 to 125.2
| [[Cubic crystal system|cubic]]
|-
| II
| 125.2 to 84.2
| [[Tetragonal crystal system|tetragonal]]
|-
| III
| 84.2 to 32.3
| α-[[Orthorhombic crystal system|rhombic]]
|-
| IV
| 32.3 to −16.8
| β-[[Orthorhombic crystal system|rhombic]]
|-
| V
| below −16.8
| [[Tetragonal crystal system|tetragonal]]<ref>{{cite journal |first1=C. S. |last1=Choi |first2=H. J. |last2=Prask |title=The structure of ND<sub>4</sub>NO<sub>3</sub> phase V by neutron powder diffraction |journal=Acta Crystallographica B |year=1983 |volume=39 |issue=4 |pages=414–420 |doi=10.1107/S0108768183002669 |doi-access=free |bibcode=1983AcCrB..39..414C }}</ref>
|}
The transition between β-rhombic to α-rhombic forms (at 32.3&nbsp;°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.<ref>{{cite journal |last1=Kumar |first1=Pratim |title=Advances in phase stabilization techniques of AN using KDN and other chemical compounds for preparing green oxidizers |journal=Defence Technology |date=December 2019 |volume=15 |issue=6 |pages=949–957 |doi=10.1016/j.dt.2019.03.002|doi-access=free }}</ref>

==Applications==
===Fertilizer===
Ammonium nitrate is an important fertilizer with [[NPK rating]] 34-0-0 (34% nitrogen).<ref>{{cite web |url=http://www.caes.uga.edu/commodities/fieldcrops/forages/events/SHC12/03%20Fertilization%20Outlook%20for%20Hay%20Producers/Nutrient%20Content%20of%20Fertilizer%20Materials.pdf |title=Nutrient Content of Fertilizer Materials |access-date=27 June 2012 |archive-url=https://web.archive.org/web/20121224131002/http://www.caes.uga.edu/commodities/fieldcrops/forages/events/SHC12/03%20Fertilization%20Outlook%20for%20Hay%20Producers/Nutrient%20Content%20of%20Fertilizer%20Materials.pdf |archive-date=24 December 2012 |url-status=dead }}</ref> 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.

===Explosives===
{{See also| List of ammonium nitrate disasters}}
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:

* [[Amatex]] (ammonium nitrate, [[TNT]] and [[RDX]])
* [[Amatol]] (ammonium nitrate and [[TNT]])
* [[Ammonal]] (ammonium nitrate and aluminum powder)
* [[ANFO]] (ammonium nitrate and [[fuel oil]])
* [[Astrolite]] (ammonium nitrate and [[hydrazine]] rocket fuel)
* [[Goma-2]] (ammonium nitrate, [[Ethylene glycol dinitrate|nitroglycol]], [[nitrocellulose]], [[dibutyl phthalate]] and [[fuel]])
* [[Minol (explosive)]] (ammonium nitrate, [[TNT]] and aluminum powder)
* [[Nitrolite]] (ammonium nitrate, [[TNT]] and [[nitroglycerin]] +)
* [[RDX|DBX]] (ammonium nitrate, [[RDX]], [[TNT]] and aluminum powder)
* [[Tovex]] (ammonium nitrate and [[methylammonium nitrate]])

====Mixture with fuel oil====
{{main|ANFO}}
ANFO is a mixture of 94% ammonium nitrate ("AN") and 6% [[fuel oil]] ("FO") widely used as a bulk industrial [[explosive]].<ref name=Cook>{{cite book |last=Cook |first=Melvin A. |title=The Science of Industrial Explosives |publisher=IRECO Chemicals |year=1974 |page=1 |asin=B0000EGDJT}}</ref>{{rp|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.<ref name=Cook/>{{rp|2}}

====Terrorism====
Ammonium nitrate-based explosives were used in the [[Sterling Hall bombing]] in Madison, Wisconsin, 1970, the [[Oklahoma City bombing]] in 1995, the [[2011 Delhi bombing]]s, the [[2011 Norway attacks|2011 bombing in Oslo]], the [[Myyrmanni bombing]] and the [[2013 Hyderabad blasts]].

In November 2009, the government of the [[Khyber Pakhtunkhwa|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]]{{Snd}}comprising the [[Upper Dir]], [[Lower Dir]], [[Swat, Pakistan|Swat]], [[Chitral]], and [[Malakand District|Malakand]] districts of the NWFP – following reports that those chemicals were used by militants to make explosives. Due to these bans, "[[Potassium chlorate]]{{Snd}}the material which allows [[safety matches]] to catch fire{{Snd}}has surpassed fertilizer as the explosive of choice for insurgents."<ref>{{cite web|url=https://www.usatoday.com/story/news/world/2013/06/25/ammonium-nitrate-potassium-chlorate-ieds-afghanistan/2442191/|title=Afghan bomb makers shifting to new explosives for IEDs|first=Tom Vanden|last=Brook|website=USA TODAY}}</ref>

===Niche uses===
Ammonium nitrate is used in some [[instant cold pack]]s, 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.<ref>{{cite news |last1=Coxworth |first1=Ben |title=Sunlight and salt water join forces in electricity-free cooling system |url=https://newatlas.com/good-thinking/sunlight-salt-water-electricity-free-cooling-system/ |access-date=21 September 2021 |work=New Atlas |publisher=Gizmag Pty Ltd. |date=20 September 2021}}</ref>

It was once used, in combination with independently explosive "fuels" such as [[guanidine nitrate]],<ref>{{cite patent|country=US|number=5531941|title=Process for preparing azide-free gas generant composition|inventor1-last=Poole|inventor1-first=Donald R.|assign= Automotive Systems Laboratory|pubdate=1996-07-02}}</ref><ref>[https://www.nytimes.com/2014/12/10/business/compound-in-takata-airbags-is-inquirys-focus.html Airbag Compound Has Vexed Takata for Years] – [[The New York Times]]</ref> as a cheaper (but less stable) alternative to [[5-aminotetrazole]] in the inflators of [[airbag]]s manufactured by [[Takata Corporation]], which were recalled as unsafe after killing 14 people.<ref>[https://www.nytimes.com/2016/08/27/business/takata-airbag-recall-crisis.html?hpw&rref=automobiles&action=click&pgtype=Homepage&module=well-region&region=bottom-well&WT.nav=bottom-well A Cheaper Airbag, and Takata's Road to a Deadly Crisis.] – [[The New York Times]]</ref> The current  USA death total is 27.<ref>{{cite web |title=Takata Spotlight |url=https://www.nhtsa.gov/vehicle-safety/takata-recall-spotlight |website=NHTSA.gov |access-date=31 May 2024}}</ref>

==Safety, handling, and storage==
Numerous safety guidelines are available for storing and handling ammonium nitrate. Health and safety data are shown on the [[safety data sheet]]s available from suppliers and from various governments.<ref name="epa_safe_storage">[https://purl.fdlp.gov/GPO/gpo45474 Chemical Advisory: Safe Storage, Handling, and Management of Ammonium Nitrate] [[United States Environmental Protection Agency]]</ref><ref>{{cite web|url=http://www.hse.gov.uk/pubns/indg230.pdf|title=Storing and handling ammonium nitrate|access-date=22 March 2006|archive-url=https://web.archive.org/web/20110704142701/http://www.hse.gov.uk/pubns/indg230.pdf|archive-date=4 July 2011|url-status=live}}</ref><ref>{{cite web|url=http://www.sciencelab.com/msds.php?msdsId=9927336|title=Ammonium nitrate MSDS|access-date=25 January 2012|archive-date=18 August 2011|archive-url=https://web.archive.org/web/20110818021106/http://www.sciencelab.com/msds.php?msdsId=9927336|url-status=dead}}</ref> 

Pure ammonium nitrate does not burn, but as a strong oxidizer, it supports and accelerates the combustion of organic (and some inorganic) material.<ref name="epa_safe_storage"/><ref>{{cite book| author= Pradyot Patnaik| title= Handbook of Inorganic Chemicals| publisher= McGraw-Hill| year= 2002| isbn= 0-07-049439-8}}</ref><ref>{{cite web|title=Ammonium nitrate|url=https://pubchem.ncbi.nlm.nih.gov/compound/Ammonium-nitrate|access-date=2020-08-06|website=PubChem}}</ref> 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.<ref name="orica">{{cite web|date=2012-04-01|title=Report for Kooragang Island Update PHA MOD1 Report|url=http://www.orica.com/ArticleDocuments/493/2012_Orica-KI_revised_PHA.pdf.aspx |archive-url=https://web.archive.org/web/20140812063130/http://www.orica.com/ArticleDocuments/493/2012_Orica-KI_revised_PHA.pdf.aspx |archive-date=2014-08-12 |url-status=live|access-date=2020-08-06|website=Orica Mining Services}}</ref><ref name="epa_safe_storage"/>

Contact with certain substances such as [[chlorate|chlorates]], [[mineral acid|mineral acids]] and [[metal sulfide|metal sulfides]], can lead to vigorous or even violent decomposition capable of igniting nearby combustible material or detonating.<ref>{{cite web|url=http://www.aidic.it/lp2013/webpapers/141cagnina.pdf|archive-url=https://web.archive.org/web/20160414164158/http://www.aidic.it/lp2013/webpapers/141cagnina.pdf|url-status=dead|title=Chemical Engineering Transactions|archive-date=14 April 2016}}</ref><ref>{{cite web|title=Ammonium Nitrate|url=https://webwiser.nlm.nih.gov/substance?substanceId=453&identifier=Ammonium%20Nitrate&identifierType=name&menuItemId=7&catId=64|access-date=2020-08-06|website=webwiser.nlm.nih.gov|language=en}}</ref>

Ammonium nitrate begins decomposition after melting, releasing [[NOx|{{NOx}}]], [[Nitric acid|HNO<sub>3</sub>]], [[Ammonia|NH{{su|b=3}}]] and [[Water|H<sub>2</sub>O]]. It should not be heated in a confined space.<ref name="epa_safe_storage"/> The resulting heat and pressure from decomposition increases the sensitivity to detonation and increases the speed of decomposition. Detonation may occur at 80 [[Standard atmosphere (unit)|atmospheres]]. Contamination can reduce this to 20 atmospheres.<ref name="orica" /> 

Ammonium nitrate has a [[critical relative humidity]] of 59.4% at 30&nbsp;°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.<ref>{{cite web 
| url= http://www.productstewardship.eu/fileadmin/user_upload/user_upload_prodstew/documents/Guidance_for_compatibility2.pdf |archive-url=https://web.archive.org/web/20150608193905/http://www.productstewardship.eu/fileadmin/user_upload/user_upload_prodstew/documents/Guidance_for_compatibility2.pdf |archive-date=2015-06-08 |url-status=live
| title=Guidance for Compatibility of Fertilizer Blending Materials
| author= Fertilizers Europe
| date= 2006
}}</ref>

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.<ref>{{cite web|url=http://www.legislation.nsw.gov.au/sessionalview/sessional/subordleg/2005-531.pdf |archive-url=https://web.archive.org/web/20120323124216/http://www.legislation.nsw.gov.au/sessionalview/sessional/subordleg/2005-531.pdf |archive-date=2012-03-23 |url-status=live|title=Dangerous Goods (HCDG) Regulations}}</ref> Licenses are granted only to applicants (industry) with appropriate security measures in place to prevent any misuse.<ref>Ammonium Nitrate-Regulating its use, Balancing Access & Protection from {{cite web| url= 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| archive-url= https://web.archive.org/web/20110311054639/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| url-status= dead| archive-date= 11 March 2011| title= Worksafe Victoria}}</ref> 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.

==Health hazards==
Ammonium nitrate is not hazardous to health and is usually used in fertilizer products.<ref name="MSDS">{{cite web| url =http://www.cfindustries.com/pdf/Ammonium-Nitrate-Amtrate-MSDS.pdf| title =Ammonium nitrate MSDS| author =CF Industries| url-status =dead| archive-url =https://web.archive.org/web/20140327104129/http://www.cfindustries.com/pdf/Ammonium-Nitrate-Amtrate-MSDS.pdf| archive-date =27 March 2014}}</ref><ref>{{cite web|url=http://chemicalland21.com/industrialchem/inorganic/ammonium%20nitrate.htm|title=Chemicalland21 – Ammonium Nitrate|url-status=dead|archive-url=https://web.archive.org/web/20120110035253/http://chemicalland21.com/industrialchem/inorganic/ammonium%20nitrate.htm|archive-date=10 January 2012}}</ref><ref>{{cite news| title= Ammonium Nitrate| publisher= Paton Fertilizers Pty Ltd | year= 2005}}</ref>

Ammonium nitrate has an [[median lethal dose|LD<sub>50</sub>]] of 2217&nbsp;mg/kg,<ref name=MSDS1>{{cite web|url=http://www.sciencelab.com/msds.php?msdsId=9927336|title=Material Safety Data Sheet, Ammonium nitrate MSDS|access-date=25 January 2012|archive-date=18 August 2011|archive-url=https://web.archive.org/web/20110818021106/http://www.sciencelab.com/msds.php?msdsId=9927336|url-status=dead}}</ref> which for comparison is about two-thirds that of [[sodium chloride|table salt]].

==Disasters==
{{main|List of ammonium nitrate disasters}}
Ammonium nitrate decomposes, non-explosively, into the [[gas]]es [[nitrous oxide]] and [[water vapor]] when heated. However, it can be induced to decompose explosively by [[detonation]].<ref>{{cite journal |last1=Chaturvedi |first1=Shalini |last2=Dave |first2=Pragnesh N. |title=Review on Thermal Decomposition of Ammonium Nitrate |journal=Journal of Energetic Materials |date=January 2013 |volume=31 |issue=1 |pages=1–26 |doi=10.1080/07370652.2011.573523|bibcode=2013JEnM...31....1C |s2cid=94427830 }}</ref> 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]].<ref>{{cite news|date=4 August 2020|title=Lebanon's president calls for two-week state of emergency in Beirut after blast|language=en|work=Reuters|location=Beirut|url=https://www.reuters.com/article/us-lebanon-security-blast-president-idUSKCN2502TZ|access-date=4 August 2020|quote=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".}}</ref>

Ammonium nitrate can explode through two mechanisms:
* Shock induced detonation. An explosive charge within or in contact with a mass of ammonium nitrate causes the ammonium nitrate to detonate. Examples of such disasters are [[Ammonium nitrate disasters#Kriewald, Germany, 1921|Kriewald]], [[Ammonium nitrate disasters#Morgan, New Jersey, 1918 (Now Sayreville)|Morgan]] (present-day [[Sayreville, New Jersey]]), [[Oppau explosion|Oppau]], and [[Tessenderlo]].
* [[Deflagration to detonation transition]]. The ammonium nitrate explosion results from a fire that spreads into the ammonium nitrate ([[Texas City Disaster|Texas City, TX]]; [[Brest, France|Brest]]; [[West Fertilizer Company Explosion|West, TX]]; [[2015 Tianjin explosions|Tianjin]]; [[2020 Beirut explosions|Beirut]]), or from ammonium nitrate mixing with a combustible material during the fire ([[Gibbstown, New Jersey|Gibbstown]], Cherokee, [[Nadadores]]). The fire must be confined at least to a degree for successful transition from a fire to an explosion.

== See also ==
* [[Resource recovery]]

==References==
{{Reflist}}

===Sources===
{{refbegin}}
* Properties: UNIDO and International Fertilizer Development Center (1998), ''Fertilizer Manual'', Kluwer Academic Publishers, {{ISBN|0-7923-5032-4}}.
{{refend}}

==External links==
* {{ICSC|0216|02}}
* [http://www.hse.gov.uk/pubns/indg230.pdf "Storing and Handling Ammonium Nitrate"], United Kingdom [[Health and Safety Executive]] publication INDG230 (1986)
* [https://purl.fdlp.gov/GPO/gpo45474 Chemical Advisory: Safe Storage, Handling, and Management of Ammonium Nitrate] [[United States Environmental Protection Agency]]
*Calculators: [http://www.aim.env.uea.ac.uk/aim/surftens/surftens.php surface tensions], and [http://www.aim.env.uea.ac.uk/aim/density/density_electrolyte.php densities, molarities and molalities] of aqueous ammonium nitrate

{{Ammonium salts}}
{{Nitrates}}
{{Nitrogen compounds}}
{{Authority control}}

[[Category:Ammonium compounds]]
[[Category:Nitrates]]
[[Category:Explosive chemicals]]
[[Category:Rocket oxidizers]]
[[Category:Pyrotechnic oxidizers]]
[[Category:Nitrogen cycle]]
[[Category:Soil improvers]]
[[Category:Inorganic fertilizers]]
[[Category:Oxidizing agents]]