Priestley, the furious free thinker of the enlightenment, and Scheele, the taciturn apothecary of Uppsala.

AMERICANS are taught that the English Unitarian minister Joseph Priestley discovered oxygen in 1774. Scandinavians are taught that the Swedish apothecary Carl Wilhelm Scheele generated oxygen in Uppsala in 1771–2, several years before Priestley. Scheele claimed that he wrote Lavoisier, describing the experiments in September, 1774. However, Lavoisier denied seeing or receiving his letter. Among Nordic historians, Lavoisier has never been forgiven for this rebuff (1). Some historians have doubted whether such a letter was ever sent or received, because Scheele first published in 1777. Priestley brought the news of his discovery to Lavoisier in October 1774. It was undoubtedly Priestley who triggered Lavoisier to realize over the next few years that air contained a new element, oxygen, which combined with combustible materials in fire. Lavoisier spent most of a decade in experiments to clarify the chemistry of oxygen and in publications overturning the conventional Phlogiston Theory, causing a revolution in chemistry. My interest in this history began in 1996, when Julian Biebuyck invited me to present the annual Priestley lecture at Penn State University. This included a visit to Priestley’s last home in Northumberland, Pennsylvania, a 2-hour drive from the Medical School. The American Chemical Society was founded following a visit to Priestley’s laboratory on the centenary of Priestley’s discovery of oxygen in 1874. The restored house and laboratory are now a National Monument.