What Lavoisier did next makes my heart sing, such is the elegance of the experiment. He heated diamond in a vacuum so that there, with no air to react with the diamond, it might survive to higher temperatures. It’s one of those experiments that is easy to propose but much harder to carry out, especially in the eighteenth century, when vacuums themselves were not so easy to produce. What happened next astounded Lavoisier: the diamond still wasn’t impervious to red heat, but this time it turned into pure graphite—proof that these two materials were indeed made of the same stuff, carbon.
