The 'discovery' of Oxygen is, still, one of the most hotly debated questions of the Golden Age of Natural Philosophy. The four leading claimants are as follows;
- Michał Sędziwój of Warsaw, a Polish alchemist and natural philosopher in the late sixteenth century (c.1592). Sędziwój realized that air is a mixture of substances, one of which (later called oxygen) is a life-giving substance. He correctly equated this "elixir of life" with the gas given off by heating niter (or saltpeter, the mineral form of potassium nitrate), driving off the nascent oxygen. This very effective method of extracting oxygen is still demonstrated in elementary chemistry labs every year.
- Oxygen was rediscovered by the Swedish pharmacist Carl Wilhelm Scheele sometime before 1773, but his finding was not published until after the independent rediscovery by Joseph Priestley.
- Joseph Priestly isolated and identified oxygen on August 1, 1774. Priestley published his discovery in 1775, and Scheele, in 1777; consequently, Priestley is usually given the credit for discovering oxygen.
- Antoine Laurent Lavoisier, working separately but concurrently with Scheele and Priestley, named the gas "oxygen." from two Greek words-οξυς (oxys), meaning acid or sharp, and γεινομαι (geinomai), meaning to engender-based on the (then and incorrect) belief that all acids contain oxygen and are formed from oxygen. Since then, the definition of an acid has been revised so that oxygen is not necessarily part of the molecular structure of every acid.