It is a decompostion reaction, of Ammonium dichromate, this reaction produce steam, Nitrogen gas and Chromium(III) oxide. The decomposition produce large amount of solid, which seems to be a Volcano eruption, hence this is called "Volcano" Experiment.
Watch more at http://www.youtube.com/cforchemistry
Music: Artifact by Kevin MacLeod @ incompetech.com
Licensed under Creative Commons "Attribution 3.0"