Chromium(III) oxide, often called chromic oxide, has been used as a green paint pigment, as a catalyst in organic synthesis, as a polishing powder, and to make metallic chromium. One way to make chromium(III) oxide is by reacting sodium dichromate, Na2Cr2O7, with ammonium chloride at 800 to 1000°C to form chromium(III) oxide, sodium chloride, nitrogen, and water.