Suspend 5.5 g of oxalic acid dihydrate in 10 cm 3 of cold water in a 600 cm 3 beaker. Add, in small portions with stirring, 1.8 g of potassium dichromate. CARE ! Cr(VI) is a suspected carcinogen The orange mixture soon warms up spontaneously, almost to boiling point, and a vigorous evolution of gas occurs. When the reaction has ceased, decant one half of the hot green-black liquid into a 100 cm3 beaker. (Save the other half for the next preparation.). Stir in 1.1 g of potassium oxalate monohydrate and when all the solid has dissolved add 2 cm3 of ethanol. Heat the reaction mixture on a water bath until solid begins to deposit from solution. Then add, with stirring, 5 cm3 of ethanol and cool in an ice bath. When cold, filter off the green-black solid and wash with three 5 cm3 portions of cold 2:1 ethanol/water and then with 10 cm3 ethanol (No flames). The product is dried in air and the yield calculated as a percentage based on chromium. The overall reaction is: