Who discovered the Oxygen

Brief biography of Joseph Priestley, British experimental chemist credited for discovery of oxygen, although he is not alone in his claim. Joseph Priestley (1733-1804) was an 18th-century British theologian, philosopher, educator, and political theorist. Credited with the discovery of oxygen, he shares it with karl Wilhelm Scheele and Antoine Lavoisier who also claim the credit.

Priestley was not a scientist but a Unitarian minister but he had active interest in philosophy, history, languages and politics. It was not until he met Benjamin Franklin in 1766 that his scientific fascination was instilled. Amateur in science, he dedicated most of his time to teaching and preaching.

Physics was the subject of Priestley’s first scientific endeavor. Encouraged by Benjamin Franklin, he wrote The History and Present State of Electricity (1767) such as discovery that graphite conducts electricity.

Priestley’s Beginnings in Chemistry

Priestley became more intrigued with chemical experiments. On taking up a new ministerial post in Leeds in 1767, he gained access to an unlimited supply of ‘fixed air’ (carbon dioxide) to use in his work.

Among other things, this led to his creation of soda water (carbon dioxide in water), an enormous impact on the soft drinks industry.

By improving the design of a piece of apparatus called “pneumatic trough,” filling it with mercury and heating solids floating in it, he was able to isolate and capture gases above the mercury.

Soon he had discovered four new chemical compound: nitrous oxide (laughing gas), nitrogen oxide, nitric oxide and hydrogen chloride.

Discovery of Other Gases

Priestley’s most successful period came under the patronage of Lord Shelburne at this estate in Wiltshire, from 1773-1780. Employed as a librarian and teacher to Shelburne’s children, Priestly was given the freedom to pursue scientific studies.

In time, he discovered chemical compounds nitrogen, carbon monoxide, sulphur dioxide, ammonia and silicon tetrafluoride. However, it was his discovery of oxygen gas for which he is famous.

Discovery of Oxygen

In 1774, Priestley stumbled into oxygen while heating mercury oxide, noticing that it enhanced the burning of a candle’s flame, prolonged the life of mice. Karl Scheele had also discovered oxygen independently in 1772 but only published his results until 1777.

As well as his later observation of the significance of sunlight in the growth of plants, this was an important foundation in subsequent research into photosynthesis. Priestley, however, did not realize the significance of his discovery leaving it to Antoine Lavoisier whom he told of his findings in 1775. He called his gas “dephlogisticated” air which means his gas contains “phlogiston” substance, central to combustion, released during the process.


Priestley’s scientific work practically ceased after his forced migration to the US in 1794, as his Birmingham laboratory was subjected to mob violence due to his political support for the French Revolution.

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