The Colorful Colorless Gas
Heating this oxide in an oven in the presence of charcoal as a reducing agent gave the metal itself.Chromium oxide was discovered in 1797 by Louis-Nicholas Vauquelin, who prepared the metal itself in the following year.Vauquelin also analysed an emerald from Peru and discovered that its green colour is because of the presence of the new element, chromium.
Used to harden steel, to manufacture stainless steel, and to form alloys used in plating to produce a hard, beautiful surface and to prevent corrosion. Used to give glass an emerald green colour. It is responsible for the green colour of emeralds and the red colour of rubies.
It is green because of the inclusion of a little chromium into the beryl crytal lattice in place of some of the aluminium ions. Similarly, traces of chromium incorporated into the crystal lattice of corundum