View source for Pyrophoricity

{{Short description|Tendency of a chemical compound to ignite in open air}}
{{distinguish|Porphyria|Porphyriticity}}
{{Redirect|Pyrophorus|the bioluminescent beetle genus|Pyrophorus (beetle)}}
{{more citations needed|date=July 2019}}

A substance is '''pyrophoric''' (from {{langx|grc|πυροφόρος}}, {{lang|grc-Latn|pyrophoros}}, 'fire-bearing') if it ignites spontaneously in air at or below {{convert|54|°C|°F}} (for gases) or within 5 minutes after coming into contact with air (for liquids and solids).<ref>GHS, seventh revised version. https://www.unece.org/fileadmin/DAM/trans/danger/publi/ghs/ghs_rev07/English/ST_SG_AC10_30_Rev7e.pdf</ref> Examples are [[organolithium compound]]s and [[triethylborane]]. Pyrophoric materials are often [[water-reactive]] as well and will ignite when they contact water or [[humid]] air. They can be handled safely in atmospheres of [[argon]] or (with a few exceptions) [[nitrogen]]. [[Fire classification]] [[fire extinguisher]]s are designated for use in fires involving metals but not pyrophoric materials in general. A related concept is [[hypergolic propellant|hypergolicity]], in which two compounds spontaneously ignite when mixed.

==Uses==
The creation of [[spark (fire)|sparks]] from metals is based on the pyrophoricity of small metal particles, and pyrophoric alloys are made for this purpose.<ref>{{citation |url=https://books.google.com/books?id=tz5dh8VoIfQC&pg=PA259 |title=Dictionary Of Chemistry |author=N. Pradeep Sharma|date=September 1998 |publisher=Gyan Publishing House |isbn=9788121205931 }}</ref>   Practical applications include the sparking mechanisms in [[lighter]]s and various toys, using [[ferrocerium]]; starting fires without matches, using a [[firesteel]]; the [[flintlock mechanism]] in firearms; and [[spark testing]] ferrous metals.

==Handling==
{{citation needed section|date=January 2025}}
{{see also|Air-free technique}}
Small amounts of pyrophoric liquids are often supplied in a glass bottle with a [[PTFE|polytetrafluoroethylene]]-lined [[septum]]. Larger amounts are supplied in metal tanks similar to gas cylinders, designed so a needle can fit through the valve opening. A syringe, carefully dried and flushed of air with an [[inert gas]], is used to extract the liquid from its container.

When working with pyrophoric solids, researchers often employ a sealed [[Glovebox|glove box]] flushed with inert gas. Since these specialized glove boxes are expensive and require specialized and frequent maintenance, many pyrophoric solids are sold as solutions, or dispersions in [[mineral oil]] or lighter [[hydrocarbon]] solvents, so they can be handled in the atmosphere of the laboratory, while still maintaining an oxygen- and moisture-free environment.  Mildly pyrophoric solids such as [[lithium aluminium hydride]] and [[sodium hydride]] can be handled in the air for brief periods of time, but the containers must be flushed with inert gas before the material is returned to the container for storage.

==Pyrophoric materials==
===Solids===
* [[White phosphorus]]
* [[Alkali metal]]s, especially [[potassium]], [[rubidium]], [[caesium]], including the alloy [[NaK]]
* Finely divided metals ([[iron]],<ref name=pm>{{citation |title=Powder metallurgy: science, technology and applications |page=48 |author=Angelo & Subramanian |year=2008 |quote=Powders of aluminium, iron and magnesium are highly pyrophoric in nature}}{{better citation needed|reason=This text is not available readily, and the ones that are claim that this only happens as a result of botched procedure (too low a temperature during atomization leading to partial re-oxidation during an oxide reduction / atomization process) which meshes with what I know of things, namely that I've spilled 100nm-2µm range aluminum flake and even finer magnalium powder on my hand and the biggest pain caused by it was the difficulty in rinsing all of it off.  There are so many pre-conditions to make these pyrophoric in air that it's silly to say that they are in general.|date=January 2025}}</ref> [[aluminium]],<ref name=pm/> [[magnesium]],<ref name=pm/> [[calcium]], [[zirconium]],{{Citation needed|date=March 2017}} [[uranium]], [[titanium]], [[tungsten]], [[bismuth]], [[hafnium]], [[thorium]], [[osmium]], [[neodymium]])
* Some metals and alloys in bulk form ([[cerium]])
* [[Alkylate]]d metal [[alkoxide]]s or nonmetal [[halides]] (diethylethoxyaluminium, dichloro(methyl)silane)
* [[Graphite intercalation compound#Potassium graphite|Potassium graphite]] (KC<sub>8</sub>)
* Metal [[hydride]]s ([[sodium hydride]], [[lithium aluminium hydride]], [[Uranium(III) hydride|uranium trihydride]])
* Partially or fully alkylated derivatives of metal and nonmetal hydrides (diethylaluminium hydride, [[trimethylaluminium]], [[triethylaluminium]], [[butyllithium]]), with a few exceptions (i.e. [[dimethylmercury]] and [[tetraethyllead]])
* [[Copper]] fuel cell catalysts ([[zinc oxide]], [[aluminium oxide]])<ref>C.W. Corti et al. / Applied Catalysis A: General 291 (2005) 257</ref>
* [[Grignard reagent|Grignard reagents]] (compounds of the form RMgX)
* Used [[hydrogenation]] [[catalysts]] such as [[palladium on carbon]] or [[Raney nickel]] (especially hazardous because of the adsorbed hydrogen)
* [[Iron(II) sulfide]]: often encountered in oil and gas facilities, where corrosion products in steel plant equipment can ignite if exposed to air
* [[Lead]] and [[carbon]] powders produced from decomposition of [[lead citrate]]<ref>[http://www.freepatentsonline.com/3297590.pdf Pyrophoric lead composition and method of making it]</ref><ref>{{cite journal|doi=10.1021/j100877a023 | volume=70 | title=The Reaction of Pyrophoric Lead with Oxygen | year=1966 | journal=The Journal of Physical Chemistry | pages=1478–1482 | author=Charles J| issue=5 }}</ref>
* [[Uranium]], as shown in the disintegration of [[depleted uranium]] penetrator rounds into burning dust upon impact with their targets; in finely divided form it is readily ignitable, and uranium scrap from machining operations is subject to spontaneous ignition<ref>[http://158.132.155.107/posh97/private/Case/hbk1081e.html#ZZ30 DOE | Office of Health, Safety and Security | Nuclear Safety and Environment | Uranium] {{Webarchive|url=https://web.archive.org/web/20150221194246/http://158.132.155.107/posh97/private/Case/hbk1081e.html#ZZ30 |date=2015-02-21 }}, retrieved 3 September 2013; [https://web.archive.org/web/20100824105716/http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hbk1081e.html archived] on 24 August 2010.</ref>
* [[Neptunium]]
* Several compounds of [[plutonium]] are pyrophoric, and they have caused some of the most serious fires occurring in [[United States Department of Energy]] facilities<ref>[http://158.132.155.107/posh97/private/Case/hbk1081d.html#ZZ281 DOE | Office of Health, Safety and Security | Nuclear Safety and Environment | Plutonium] {{Webarchive|url=https://web.archive.org/web/20150221215850/http://158.132.155.107/posh97/private/Case/hbk1081d.html#ZZ281 |date=2015-02-21 }}, retrieved 3 September 2013; [https://web.archive.org/web/20100928002539/http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hbk1081d.html#ZZ281 archived] on 28 September 2010.</ref>
*Petroleum hydrocarbon (PHC) sludge

=== Liquids ===
* [[Diphosphane]]
* [[Metalorganics]] of main group metals (e.g. [[aluminium]], [[gallium]], [[indium]], [[zinc]], [[cadmium]], etc.)
* [[Triethylborane]]
* [[tert-Butyllithium|''tert''-Butyllithium]]
* [[Diethylzinc]]
* [[Triethylaluminium]]

=== Gases ===
* Nonmetal [[hydride]]s ([[arsine]], [[phosphine]],{{efn-lr|Phosphine, PH<sub>3</sub> is only pyrophoric if impure, with  P<sub>2</sub>H<sub>4</sub> present.}} [[diborane]], [[germane]], [[silane]])
* [[Metal carbonyl]]s ([[dicobalt octacarbonyl]], [[nickel carbonyl]])

== Explanatory notes ==
{{Notelist-lr}}

== References ==

{{Reflist|colwidth=35em}}

==External links==
*[https://web.archive.org/web/20100527183802/http://www.hss.energy.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hdbk1081.pdf US Dept. of Energy Handbook, "Primer on Spontaneous Heating and Pyrophoricity"] (archived)
*{{Cite web |url=http://prtl.uhcl.edu/portal/page/portal/RSK/Safety/Lab%20Safety/High%20Hazard%20Materials/DDCC509064554644E0401DAC7AB601FB |title=List of pyrophoric materials |archive-url=https://web.archive.org/web/20150709154008/http://prtl.uhcl.edu/portal/page/portal/RSK/Safety/Lab%20Safety/High%20Hazard%20Materials/DDCC509064554644E0401DAC7AB601FB |archive-date=2015-07-09}}
*{{cite web |title=Pyrophoric Chemicals Guide |url=http://www.dehs.umn.edu/PDFs/PyrophoricMaterialsListAppendix.pdf |website=Environmental Health and Safety |publisher=University of Minnesota |access-date=27 March 2021 |archive-url=https://web.archive.org/web/20141031032636/http://www.dehs.umn.edu/PDFs/PyrophoricMaterialsListAppendix.pdf |archive-date=31 October 2014 |language=English |url-status=dead}}

[[Category:Chemical properties]]
[[Category:Fire making]]
[[Category:Pyrophoric materials| ]]

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