A substance is pyrophoric (from , pyrophoros, 'fire-bearing'
/ref> Examples are organolithium compounds 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 extinguishers are designated for use in fires involving metals but not pyrophoric materials in general. A related concept is hypergolicity, in which two compounds spontaneously ignite when mixed.
Uses
The creation of sparks from metals is based on the pyrophoricity of small metal particles, and pyrophoric alloys are made for this purpose.
Practical applications include the sparking mechanisms in
and various toys, using
ferrocerium; starting fires without matches, using a
firesteel; the flintlock mechanism in firearms; and
spark testing ferrous metals.
Handling
Small amounts of pyrophoric liquids are often supplied in a glass bottle with a
PTFE-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 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
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White phosphorus
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, especially potassium, rubidium, caesium, including the alloy NaK
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Finely divided metals (iron,
[ magnesium,][ calcium, zirconium, uranium, titanium, tungsten, bismuth, hafnium, thorium, osmium, neodymium)
]
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Some metals and alloys in bulk form (cerium)
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metal or nonmetal halides (diethylethoxyaluminium, dichloro(methyl)silane)
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Potassium graphite (KC8)
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Metal (sodium hydride, lithium aluminium hydride, uranium trihydride)
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Partially or fully alkylated derivatives of metal and nonmetal hydrides (diethylaluminium hydride, trimethylaluminium, triethylaluminium, butyllithium), with a few exceptions (i.e. dimethylmercury and tetraethyllead)
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Copper fuel cell catalysts (zinc oxide, aluminium oxide)
[C.W. Corti et al. / Applied Catalysis A: General 291 (2005) 257]
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Grignard reagent (compounds of the form RMgX)
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Used hydrogenation catalysts such as palladium on carbon or Raney nickel (especially hazardous because of the adsorbed hydrogen)
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Iron(II) sulfide: often encountered in oil and gas facilities, where corrosion products in steel plant equipment can ignite if exposed to air
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Lead and carbon powders produced from decomposition of lead citrate
[ Pyrophoric lead composition and method of making it]
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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
[ DOE | Office of Health, Safety and Security | Nuclear Safety and Environment | Uranium , retrieved 3 September 2013; archived on 24 August 2010.]
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Neptunium
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Several compounds of plutonium are pyrophoric, and they cause some of the most serious fires occurring in United States Department of Energy facilities
[ DOE | Office of Health, Safety and Security | Nuclear Safety and Environment | Plutonium , retrieved 3 September 2013; archived on 28 September 2010.]
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Petroleum hydrocarbon (PHC) sludge
Liquids
Gases
Explanatory notes
External links
