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Can you light diamond on fire?
Category: Chemistry
Published: March 27, 2014
By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and physics professor at West Texas A&M University
Yes, diamond can be burned. The most common form of burning in everyday life is carbon combustion. In carbon combustion, carbon atoms break their bonds with each other and with other atoms (which requires energy) to form bonds with oxygen atoms (which releases even more energy than first required). The net extra energy released in this reaction can then go on to rip more carbon atoms free of their non-oxygen neighbors, thus continuing the reaction, or the energy can escape as heat and light. Carbon bonded with oxygen makes carbon dioxide and carbon monoxide, which are the waste products of combustion. They drift away from the fire as gases. Since biological organisms, and the fuels derived from biological organisms, contain a lot of carbon, much of the burning that goes on around us is carbon combustion. This includes camp fires, candles, car engines, and gas stoves. Pure diamond consists only of carbon atoms bonded into a dense, strong crystal lattice, so diamond can also undergo carbon combustion. In fact, Antoine Lavoisier first determined that diamond is made out of carbon by burning it and showing that the combustion product was carbon dioxide. The book Diamond Films and Coatings by Robert Foster Davis states, "In 1772 the French chemist Antoine L. Lavoisier found that the products of diamond combustion behaved as, and most assuredly were, solely carbon dioxide... He determined that the ignition and burning of each produced equal amounts of ‘bound air'."
The presence of strong atomic bonds in diamond means that it takes a lot of energy to rip apart the carbon atoms in diamond in order to free them up to burn with oxygen. As a result, it takes a higher temperature to burn diamond than to burn wood. The ignition temperature of wood is about 300 degrees C while the ignition temperature of diamond in air is about 900 degrees C. Although diamond requires a higher temperature to burn, it does indeed burn via normal carbon combustion. You can even burn diamond in a regular flame if you are patient and conditions are right. To accelerate the burning of diamond, you can give it more heat and more oxygen. For instance, holding a blow torch to a diamond and then throwing it in a cup of liquid oxygen leads to an impressive display. Jewelers have to worry about this effect every day because they use flames to mold the metal in a diamond ring but don't want to burn the diamond.