HgO is sometimes used in the production of mercury as it decomposes quite easily. When it decomposes, oxygen gas is generated. Historically, in 1774, Joseph Priestley discovered the oxygen released by heating mercuric oxide, although he did not identify the gas as oxygen. Rather, Priestly called it "dephlogisticated air", as that was the paradigm that he was working under at the time. Lavoisier called "dephlogisticated air" as "oxygen" due to the acidic compounds that the gas produce. This is why the textbook account of the discovery of oxygen is inaccurate in the sense that it is really impossible to answer who "discovered" oxygen. This was, however one of the major milestones of chemistry.
- Almqvist, Ebbe (2003). History of Industrial Gases. Springer. p. 23. ISBN 0306472775.
- Stephen, Leslie (1896). Dictionary of National Biography. Smith, Elder. p. 373.
- Moore, John W. (2005). Chemistry: The Molecular Science. Thomson Brooks/Cole. p. 941. ISBN 0534422012. Unknown parameter