Everything about Pyrophoricity totally explained
A
pyrophoric substance will ignite spontaneously; that is, its
autoignition temperature is below
room temperature. Examples are
iron sulfide and many reactive
metals including
uranium, when powdered or sliced thinly. 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 few exceptions)
nitrogen. Most pyrophoric fires should be extinguished with a Class D
fire extinguisher for burning metals.
Uses
The creation of
sparks from metals is based on the pyrophoricity of small metal particles. This can be useful, including: the sparking mechanisms in
lighters and various toys, using
ferrocerium; starting fires without matches, using a
firesteel; the
flintlock mechanism in firearms; and
spark testing metals.
Safe handling of pyrophoric materials
Liquids
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.
Solids
Pyrophoric solids require the use of a sealed glove box flushed with inert gas. Glove boxes are expensive, and require maintenance. Thus, many pyrophoric solids are sold as solutions, or dispersions in mineral oil or lighter hydrocarbon solvents. 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 storage.
Disposal
Small amounts of pyrophoric materials and empty containers must be disposed of carefully, by quenching the residue. Less reactive substances can be disposed of by diluting heavily with an unreactive solvent like
hexane, placing the container in a
cooling bath, and adding water dropwise. More reactive substances can be quenched by slowly adding the dilute solution to
dry ice, then adding a mildly reactive substance, which doesn't freeze in dry ice, to the mixture (wet
diethyl ether,
acetone,
isopropyl alcohol, and
methanol are often used)
List of pyrophoric materials
Solids
- Finely divided metals (magnesium, calcium, zirconium, uranium)
- Alkali metals (sodium, potassium)
- Metal hydrides or nonmetal hydrides (germane, diborane, sodium hydride, lithium aluminium hydride, uranium trihydride)
- Grignard reagents (compounds of the form RMgX)
- Partially or fully alkylated derivatives of metal and nonmetal hydrides (diethylaluminium hydride, trimethylaluminium, butyllithium, triethylboron)
- Uranium is pyrophoric, as shown by the vaporization of depleted uranium penetrator rounds into burning dust upon impact with their targets. In finely divided form it's readily ignitable, and uranium scrap from machining operations is subject to spontaneous ignition.
- Alkylated metal alkoxides or nonmetal halides (diethylethoxyaluminium, dichloro(methyl)silane)
- Metal carbonyls (dicobalt octacarbonyl, nickel carbonyl)
- Used hydrogenation catalysts such as Raney nickel (especially hazardous because of the adsorbed hydrogen)
- Copper fuel cell catalysts, for example, Cu/ZnO/Al2O3
- Phosphorus (white, or yellow)
- Plutonium: several compounds are pyrophoric, and it causes some of the most serious fires occurring in United States Department of Energy facilities.
- Methanetellurol (CH3TeH)
- Iron Sulfide: often encountered in oil and gas facilities where corrosion products in steel plant equipment can ignite if exposed to air.
Gases
Arsine
Diborane
Phosphine
Silane
Liquids
Hydrazine
Metalorganics of main group metals (for example aluminium, gallium, indium, zinc and cadmium etc.)Further Information
Get more info on 'Pyrophoricity'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://pyrophoricity.totallyexplained.com">Pyrophoricity Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
