Oxygen, an invisible gas, sustains nearly all complex life on Earth, fueling everything from our breath to the burning of a candle. Pinpointing a single moment or location for its discovery is intricate, as its recognition involved multiple independent investigations across different nations. This layered historical narrative reveals a fascinating interplay of scientific observation, experimental technique, and theoretical interpretation.
Carl Wilhelm Scheele’s Early Work
Carl Wilhelm Scheele, a Swedish pharmacist and chemist, independently isolated oxygen several years before others, though his findings were not published until later. Working in Uppsala and later Köping in the early 1770s, Scheele conducted numerous experiments involving the heating of various compounds. He meticulously heated substances such as manganese oxide, potassium nitrate, and mercuric oxide, observing the release of a novel gas.
Scheele collected this gas and noted its properties, including its ability to support combustion more vigorously than ordinary air. He referred to this gas as “fire air” because of its capacity to promote burning processes. Despite his work occurring around 1771-1772, the publication of his book, Chemical Treatise on Air and Fire, was significantly delayed until 1777. This delay meant that others received credit for the discovery earlier, contributing to the historical ambiguity surrounding oxygen’s initial isolation.
Joseph Priestley’s Independent Isolation
Joseph Priestley, an English theologian and natural philosopher, independently isolated oxygen in Wiltshire, England, in August 1774. His experiment involved focusing sunlight onto a sample of mercuric oxide using a large “burning glass.” This process released a gas that Priestley collected and studied.
Priestley observed that a candle burned with an unusually bright flame when introduced into this gas, and a mouse placed within it lived for a significantly longer period than in normal air. He initially named this gas “dephlogisticated air,” based on the prevailing phlogiston theory of combustion, which suggested that substances released a hypothetical element called phlogiston when they burned. Priestley believed this air was ordinary air from which phlogiston had been removed, making it exceptionally pure.
Antoine Lavoisier and the Naming of Oxygen
Antoine Lavoisier, a French chemist working in Paris during the late 1770s, played a pivotal role in understanding the true nature of the gas isolated by Scheele and Priestley. He built upon their observations, conducting precise quantitative experiments that distinguished between the new gas and common air. Lavoisier’s rigorous methodology involved carefully weighing reactants and products.
Lavoisier recognized that this gas was not “fire air” or “dephlogisticated air” but a distinct chemical element that combined with other substances during combustion and respiration. Through his experiments, he disproved the phlogiston theory, demonstrating that burning was a process of combining with this specific gas. In 1777, Lavoisier named the element “oxygen,” deriving the term from Greek words meaning “acid-forming,” as he initially believed it was a component of all acids. His work transformed chemistry by correctly identifying oxygen’s role in chemical reactions.