Discovery of Oxygen

Oxygen was independently isolated by two chemists within a few years of each other, a genuine priority dispute rather than a single settled discovery. Carl Wilhelm Scheele produced the gas by heating mercuric oxide and other compounds as early as 1771 to 1772 and called it fire air, but publication of his findings was delayed until 1777. Joseph Priestley isolated the same gas independently on 1 August 1774, calling it dephlogisticated air, and published promptly; because he published first, Priestley is usually credited as the discoverer even though Scheele's experimental work came earlier. Priestley described the experiment to Antoine Lavoisier in Paris in October 1774; Lavoisier repeated it, showed the gas was a distinct element involved in combustion and respiration rather than a modified form of ordinary air, and around 1777 to 1778 gave it the name oxygen, from Greek roots meaning acid-former, based on his mistaken belief that it was a necessary component of all acids. Neither Scheele nor Priestley accepted Lavoisier's interpretation of what the gas was; both remained committed to versions of the phlogiston theory Lavoisier's work eventually displaced.