Chromium Metal: Chromic Oxide Reduced by Aluminium (Thermit)

Aluminium takes the oxygen from chromic oxide with so much heat that the chromium comes out molten. Thorpe (1912-13) gives Goldschmidt's thermit: chromic oxide mixed with aluminium powder in a magnesia-lined crucible, lit through a fuse of aluminium powder and barium peroxide with a magnesium ribbon. The heat carries the reaction through the whole charge, and carbon-free chromium sinks under a slag of alumina. White heat: outdoors on dry sand, face shield, stand well back. The picture: chromium metal (Wikimedia Commons).