Induced Pyrophoricity

When we read however, that an alloy of copper, zinc, and barium metal is described as pyrophoric, stable in air we realize that a second meaning, that of producing sparks when ground or abraded, is attached to the word pyrophoric, causing a need for clarification where the word pyrophoric is used without further ampliflcation. Metals and metal alloys of the spark-producing category—borderline cases both of pyrophoric behavior and of pyrotechnic interest—are the subject of this chapter. 

The ancient method of striking together flint and steel or flint and pyrites not only requires considerable effort, but it produces relatively cool sparks that ignite tinder or black powder but not liquids such as alcohol, benzene, or gasoline. These liquid fuels are easily ignited, however, by the very hot sparks from alloys of cerium. 

Lighter flint alloys contain additions of iron (up to 30%) for greater diemical and physical resistance. The properties of cerium and its alloys are described in some detail in the major inorganic encyclopedias and textbooks. 

Misch metal, ground under xylene in small ball mills and incorporated into bridgewire sensitive ignition mixtures and also in some delay formulas, was still in use in Germany during World War II. It seems to be quite unsuitable for items that have to be stored for a considerable time. 

Zirconium/lead alloys in a wide range of proportions spark or catch fire on impact and have been proposed for use as impact igniters for incendiary bullets, or as tracers that mark the impact of a projectile by the light effect. Similar alloys mixed with organic fuels are claimed in a U. S. patent as self-igniting incendiaries.  

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The finely-powdered metal is pyrophoric. Its radioactive isotopes Sr-89 and Sr-90 emit high-energy beta radiation. They are extremely hazardous because they deposit in bones replacing calcium. Their radiation can damage bone marrow and blood-forming organs, inducing cancer. 

Base-induced elimination of hydrogen chloride from the diphosphine (156) has given a new class of diphosphenes (157). Reduction of dialkylamino-dichlorophosphines with lithium aluminium hydride also affords these systems, which are reported to be pyrophoric, red liquids that are stable in solution for... 

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