Ammonium dichromate ((NH4)2Cr2O7) is ignited, initiating an exothermic conversion. Image 3 in a series of 4. Ammonium dichromate is sometimes known as Vesuvian Fire, because of its use in demonstrations of tabletop "volcanoes". However, this demonstration has become unpopular in schools due to the compound's carcinogenic nature. Like the well-known explosive ammonium nitrate, ammonium dichromate contains both an oxidizer (dichromate) and a reducer (ammonium), making it thermodynamically unstable. Its decomposition reaction proceeds to completion once initiated, producing voluminous dark green powdered chromium(III) oxide.