In the new Guide for first teaching in 2014 under Stoichiometric relationships, it states in the Theory of Knowledge part of 1.1 “Lavoisier’s discovery of oxygen, which overturned the phlogiston theory of combustion, is an example of a paradigm shift. How does scientific knowledge progress?”

This seems a strange statement to me as it is generally accepted that Lavoisier did not discover oxygen.

Attributing who made the first discovery of many scientific findings can be notoriously difficult and contentious. For example, was it Alexander Fleming who first discovered penicillin as most texts and websites claim or was it Clodomiro Twight, a Costa Rican? Often it is nationalistic and political factors which determine who history credits with the first discovery. Fleming worked at St Mary’s Hospital, Paddington where the newspaper magnate Lord Beaverbrook had connections and Beaverbrook used his newspapers to publicise Fleming’s work even though Clodomiro Twight published his finding before Fleming.  Similar controversy surrounds the discovery of oxygen. Certainly the first publication of the discovery appears to have been made by Joseph Priestly. It seems likely that Priestly first isolated what he called ‘dephlogisticated air’ in August 1774 at Bowood House in the UK. Later that year while he was in Paris he replicated his experiment for Antoine Lavoisier. In March he communicated his discovery in letters to several people and read out a paper to the Royal Society which was published in the Society’s Journal Philosophical Transactions (An Account of further Discoveries in Air, 65 (1775): 384–94). His preparation of oxygen was achieved by heating mercury oxide by using a lens to focus the sun’s rays on the oxide and then he showed that mice survived when exposed to the gas produced, He also breathed the ‘dephlogisticated air’ in himself and wrote that it was” five or six times better than common air for the purpose of respiration and inflammation”. In fact it seems probable that the first discovery of oxygen was made some two years earlier than Priestly by a Swedish scientist, Carl Wilhelm Scheele. Scheele obtained oxygen by heating not only mercuric oxide but also some metal nitrates and called the gas ‘fire air’ because it supported combustion. Scheele wrote about this in a manuscript sent to his publisher in 1775 but the work, Treatise on Air and Fire, was only published in 1777.  

So why has the IB listed only Lavoisier as the discoverer of oxygen? Priestly showed his experiment to Lavoisier in 1774 and Scheele posted a letter to Lavoisier detailing his discovery on 30 September 1774 (A copy of this letter was found after Scheele’ death, although Lavoisier claimed to have never seen it). There seems little doubt that Lavoisier did not independently discover oxygen and to some extent was culpable of academic dishonesty by not acknowledging the work of others. However what he did do was to realise the significance of the discovery.  He was the first to call ‘dephlogisticated air’ and ‘fire air’ oxygen which he derived from the Greek meaning producer of sharp taste as he thought that all acids contained oxygen. He also used quantitative chemistry to show that during combustion substances combine with oxygen and thus conclusively disproved the phlogiston theory.

There is a lot of good TOK in the statement in 1.1 of the new programme but for the IB Chemistry programme to imply that it was Lavoisier alone who discovered oxygen is patently misleading.