When did Antoine Lavoisier discover oxygen?
Antoine Lavoisier was never credited with the discovery of any element. Nor does he deserve that honor. The dates and events surrounding the discovery of oxygen offer the following blunt reminders to anyone seeking a place in scientific posterity:
Document and date your work.
Recognize the importance of your discovery.
Interpret your work correctly and thoroughly, or you may not receive credit for it.
Tell someone what you've done.
Tell the community, not just a colleague.
Acknowledge your competitors.
Carl Wilhelm Scheele discovered that red-hot manganese oxide (MnO2) produces a gas. He called the gas "fire air" because of the brilliant sparks it produced when it came in contact with hot charcoal dust. He recognized that heating mercuric oxide produced the same gas. The reaction is now known to be
2 Hg() + O2(g)
He collected the gas in pure form using a small bag. He explained the properties of fire air using the phlogiston theory, which was soon discredited by Lavoisier. He carefully recorded the experiment in his notes, but waited several years before publishing them.
Pharmacist Pierre Bayen discovers that heating mercury oxides resulted in a discharge of gas and a loss of mass. He collected the gas, and noted that it was slightly denser than air. Bayen was timid about publishing anything but direct observations. He did not interpret his results and he did not examine the gas further. Had he done so, he would have realized that the gas he had collected was not ordinary air. He realized his mistake after Lavoisier published his work, and tried to lay claim to the discovery, but he was too late. He has been forgotten by history.
August 1, 1774
Joseph Priestley independently repeats the production of oxygen from mercuric oxide in his laboratory at Lord Shelburne's country mansion near Calne, England. He wrote, "What surprised me more than I can well express, was that a candle burned in this air with a remarkably vigorous flame..." Priestley carefully documented his work, recognized the significance of what he had done, and published his results promptly. Posterity gives Priestley credit for the discovery of oxygen.
September 16, 1774
Lavoisier observes that heating mercuric oxide produces metallic mercury. He thought the reaction might have been caused by contact with iron; he made no note of gas evolution in his notebook.
October 15, 1774
Lavoisier received a letter from Scheele that carefully described the preparation of "fire air" by heating silver carbonate. Lavoisier never answered the letter.
Priestley visits Lavoisier in Paris and discussed his experiments with the decomposition of mercuric oxide over dinner. In 1800, he recalled that dinner at Lavoisier's house:
Having made the discovery some time before I was in Paris, in the year 1774, I mentioned it at the table of Mr. Lavoisier, when most of the philosophical people of the city were present, saying that it was a kind of air in which a candle burned much better than in common air, but that I had not then given it a name. At this, all the company, and Mr. and Mrs. Lavoisier as much as any, expressed great surprise.
March 8, 1775
Priestley demonstrates that sealed containers of the new gas can support life longer than atmospheric air. He called the gas "dephlogisticated air", using terminology and ideas from the soon-to-be-discredited phlogiston theory to explain his observations. He tried breathing the gas himself, and reported that he felt "peculiarly light and easy for some time afterwards. Who can tell but that, in time, this pure air may become a fashionable article in luxury."
Lavoisier announced to the Academy of Science in Paris that he had isolated a component of air that he called "eminently breathable air" by decomposition of mercuric oxide. (Carmen Giunta has published Lavoisier's paper in his collection of classic papers from the history of chemistry. Giunta highlights changes in the paper between 1775 and its actual publication date in 1778.)
Scheele reports his preparation of oxygen in his Treatise on Fire and Air. He was aware of Priestley's and Lavoisier's claims, but he did not make any claim of his own. Lavoisier biographer Jean-Pierre Poirier describes Scheele as "self-effacing" and speculates that Scheele did not want to be accused of plagiarism- even though the discovery was rightly his! Scheele does receive parenthetical credit today.
In his Traité Élémentaire de Chimie, Lavoisier describes the preparation of oxygen in detail by heating the red oxide of mercury. Lavoisier refers to oxygen as "this air, which Mr. Priestley, Mr. Scheele, and I discovered about the same time" [Partington].
Priestley denounced Lavoisier's claim in his book Experiments and Observations on Different Kinds of Air, saying that Lavoisier had borrowed his idea for preparing oxygen from mercuric oxide, and had not clearly realized at the time that oxides contained only a component of atmospheric air, not atmospheric air in whole. Lavoisier's attempt to wrestle credit for the discovery from Priestley was witnessed by his colleague Edmond Genet [Poirier]:
I also had the advantage during my stay at Birmingham of becoming acquainted with Dr. Priestley who had the kindness to repeat for my gratification his most interesting experiments on air and gases of which I sent an account to the Academy of Paris. At that time, Lavoisier was pursuing the same subject, and I was surprised on my return to hear him read a memorial at one of the sittings of the Academy which was simply a repetition in different words of Priestley's experiments which I had reported. He laughed, and said to me, "My friend, you know that those who start the hare do not always catch it."