The Story Behind Oxygen Discovery

The Story Behind Oxygen Discovery

Who Discovered Oxygen?

In August 1774 Joseph Priestley isolated an "air" that appeared to be completely new, but he did not have an opportunity to pursue the matter because he was about to tour Europe with Shelburne. While in Paris, Priestley replicated the experiment for others, including French chemist Antoine Lavoisier. After returning to Britain in January 1775, he continued his experiments and discovered "vitriolic acid air" (sulphur dioxide, SO2).

In March he wrote to several people regarding the new "air" that he had discovered in August. One of these letters was read aloud to the Royal Society, and a paper outlining the discovery, titled "An Account of further Discoveries in Air", was published in the Society's journal Philosophical Transactions. Priestley called the new substance "dephlogisticated air", which he made in the famous experiment by focusing the sun's rays on a sample of mercuric oxide. He first tested it on mice, who surprised him by surviving quite a while entrapped with the air, and then on himself, writing that it was "five or six times better than common air for the purpose of respiration, inflammation, and, I believe, every other use of common atmospherical air". He had discovered oxygen gas (O2).

Priestley assembled his oxygen paper and several others into a second volume of Experiments and Observations on Air, published in 1776. He did not emphasise his discovery of "dephlogisticated air" but instead argued in the preface how important such discoveries were to rational religion. His paper narrated the discovery chronologically, relating the long delays between experiments and his initial puzzlements. Thus, it is difficult to determine when exactly Priestley "discovered" oxygen. Such dating is significant as both Lavoisier and Swedish pharmacist Carl Wilhelm Scheele have strong claims to the discovery of oxygen as well, Scheele having been the first to isolate the gas and Lavoisier having been the first to describe it as purified "air itself entire without alteration".

In his paper "Observations on Respiration and the Use of the Blood", Priestley was the first to suggest a connection between blood and air, although he did so using phlogiston theory. In typical Priestley fashion, he prefaced the paper with a history of the study of respiration. A year later, clearly influenced by Priestley, Lavoisier was also discussing respiration at the Académie des sciences. Lavoisier's work began the long train of discovery that produced papers on oxygen respiration and culminated in the overthrow of phlogiston theory and the establishment of modern chemistry.

Joseph Priestley

Joseph Priestley

Joseph Priestley was an English chemist, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist who published over 150 works. He has historically been credited with the independent discovery of oxygen in 1774 by the thermal decomposition of mercuric oxide, having isolated it. Although Swedish chemist Carl Wilhelm Scheele also has strong claims to the discovery, Priestley published his findings first. Scheele discovered it by heating potassium nitrate, mercuric oxide, and many other substances about 1772.

During his lifetime, Priestley's considerable scientific reputation rested on his invention of carbonated water, his writings on electricity, and his discovery of several gases, the most famous being what Priestley dubbed "dephlogisticated air" (oxygen). Priestley's determination to defend phlogiston theory and to reject what would become the chemical revolution eventually left him isolated within the scientific community.

The Story Behind Oxygen Discovery
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