I was curious about the combustion of pure carbon, such as graphite or diamond. I know that in the presence of hydrogen, the biproduct is H2O, and in the presence of oxygen the biproduct is CO2. But what about the burning of pure carbon in a sealed chamber using, say, a bomb calorimeter. Also, I know that the incomplete combustion of carbon forms soot, which is, essentially, carbon. So what is the deal? How does pure carbon burn?