Hypergolic Ignition of Various Compounds with Nitric Acid shows the ignition of powdered solid borane compounds with a drop of concentrated nitric acid. Reaction is completed within 10 ms of contact. The green color indicates the presence of boron.
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Credit: Stephen Heister, Timothee Pourpoint, Steven Son, Mark Pfeil, Jacob Dennis, and P. V. Ramachandran of Purdue University, via the Central States Section of the Combustion Institute