Joseph Priestley: The Man Who Discovered Oxygen

Joseph Priestley (1733–1804) was an English clergyman, teacher, and pioneering chemist.
In 1774, he heated mercuric oxide with sunlight and collected a “new air.”
This gas made candles burn brighter and mice live longer—he had discovered oxygen.
Priestley called it “dephlogisticated air,” still thinking within the old phlogiston theory.
Around the same time, Carl Wilhelm Scheele also discovered oxygen, but published later.
Antoine Lavoisier correctly explained oxygen’s role in combustion and breathing, naming it “oxygen.”
Priestley also experimented with gases like carbon dioxide, leading to the invention of carbonated water.
He believed science should improve daily life, making discoveries accessible to everyone.
Despite his brilliance, his refusal to abandon phlogiston theory slowed acceptance of his ideas.
Priestley’s oxygen discovery transformed chemistry, opening the path to modern chemical understanding.