Pyrophoric chemicals ignite spontaneously when exposed to oxygen. Pyrophoricity is the basis for sparks being generated from a metal alloy being struck as in a flintlock musket, lighter or sparking toy.
Word origin: Greek pyro = fire, pyrophorus = fire-bearing
Features of a pyrophoric chemical:
(1) gas, solid or liquid that has the potential to spontaneously ignite on exposure to air
(2) at temperatures < 55°C (<= 130°F).
Examples of chemicals and chemical classes that are pyrophoric:
(1) alkali metals (sodium, potassium, cesium)
(2) lithium and organolithium compounds (alkyllithium, etc)
(3) metal alkyls (alkylzincs, alkylmagnesiums) or metal hydrides
(4) finely powdered metals (including iron, aluminum, plutonium and uranium)
(5) iron sulfide
(6) petroleum hydrocarbon sludge
(7) white phosphorus
Pyrophoric chemicals often
(1) react violently or ignite on exposure to water or in high humidity.
(2) are corrosive
(3) may form peroxides
Safe handling of a pyrophoric chemical requires:
(1) storage under an oxygen-free, inert atmosphere such as nitrogen or argon
(2) handling in a glove box with controlled atmosphere
(3) availability of powdered lime (calcium oxide), soda ash or sand to completely cover any spill
(4) fires require specialized fire extinguishers (Class D)
(5) disposal as hazardous waste
