ammonium dichromate volcano

Ammonium dichromate, (NH₄)₂Cr₂O₇, is often known as Vesuvian Fire, for reasons you can see from the video below. It has been used in pyrotechnics and in the early days of photography. The volcano demonstration involves igniting a pile of the salt, which initiates the following conversion:

(NH₄)₂Cr₂O₇(s) → Cr₂O₃(s) + N₂(g) + 4H₂O(g)

This demonstration finds only limited use because the chromium(III) oxide ash produced by this reaction is toxic, possibly carcinogenic. This is also the reason I get the technicians to clean it up.