Chemicals that can spontaneously ignite very quickly when exposed to air, without the presence of an ignition source, are called pyrophoric materials. They can be solids, liquids, or gases and ignite in the presence of oxygen (air) due to highly reactive properties.
Examples of Pyrophoric Chemicals
- Organolithium compounds (e.g., tert-Butyllithium, sec-Butyllithium)
- Alkyl and Aryl Lithium compounds
- Diethylzinc (organozincs)
- Trimethylaluminum (aluminum alkyls)
- Sodium Hydride, Potassium Hydride, Lithium Aluminum Hydride (metal hydrides)
- Finely divided metals like Calcium, Magnesium, Titanium, Zinc, Zirconium
- Silane, Diborane, Phosphine (gaseous pyrophorics)
- White Phosphorus
Characteristics
- They ignite spontaneously at or below about 54 °C (129 °F) upon exposure to air.
- Many are also water-reactive and will ignite when exposed to moisture.
- They require strict handling and storage protocols, typically under inert atmospheres or mineral oil to prevent air contact.
- Pyrophoric metals and compounds are used in various industries but are hazardous due to their tendency to ignite without any external ignition source.
Handling Precautions
- Store under inert gases or non-reactive liquids.
- Use in controlled environments such as glove boxes or fume hoods with safety equipment.
- Immediate fire hazards require preparation of appropriate extinguishing materials like Class D fire extinguishers.
Pyrophoric materials are distinct in their spontaneous ignition risk and include a wide range of reactive substances commonly used in chemical synthesis and industrial applications.
