Guillaume Rouelle. Engraving of a lecture run by Guillaume Francois Rouelle (1703-1770), French chemist (at upper centre). In this lecture he caused an explosion by mixing nitric acid and turpentine. The audience escaped serious injury but a wig and a chimney were destroyed". During 1742-68 he was a popular, enthusiastic chemical demonstrator at the Jardin du Roi, Paris. He taught most of the French chemists of the late 18th century, the most famous being Antoine Lavoisier. Rouelle believed in Georg Stahl's incorrect phlogiston theory of combustion. Phlogiston was a flammable component of materials which was supposedly given off when they burned."