Diamond burning in liquid oxygen. Clip 4 of 4. The white hot diamond is dropped into liquid oxygen, a powerful oxidising agent. The diamond continues to burn in the oxygen, even at this very low temperature of -183 degrees Celsius, or 90K. The carbon in the diamond reacts with the oxygen to form carbon dioxide as the only product. This experiment was first performed by the chemist Smithson Tennant in 1797, who used it to show that diamond is made solely of carbon.