Adjective
Alt. of Pyrophorous
Source: Webster's dictionaryBlackening reveals oxidation due to irradiation by oxygen atoms. citation citation Precautions Finely divided metallic osmium is pyrophoric and reacts with oxygen at room temperature, forming volatile osmium tetroxide. Source: Internet
Finely divided neptunium metal presents a fire hazard because neptunium is pyrophoric ; small grains will ignite spontaneously in air at room temperature. Source: Internet
It can take as much as thirty years after the ingestion of thorium for symptoms to manifest themselves. citation Powdered thorium metal is pyrophoric and often ignites spontaneously in air. Source: Internet
It is highly pyrophoric : the autoignition temperature of caesium is −116 °C, and it ignites explosively in air to form caesium hydroxide and various oxides. Source: Internet
Their reactivity increases going down the group: while lithium, sodium and potassium merely burn in air, rubidium and caesium are pyrophoric (spontaneously catch fire in air). Source: Internet
Precautions Care needs to be taken when machining hafnium because it is pyrophoric —fine particles can spontaneously combust when exposed to air. Source: Internet