Priestley Joseph


, Joseph 1733-1804.
British chemist noted for work on the isolation of gases and his discovery of oxygen (1774).


(prēst′lē), Joseph 1733-1804.
British chemist who discovered oxygen (1774) and ten other gases, including hydrogen chloride, sulphur dioxide, and ammonia.
Biography When Joseph Priestley met Benjamin Franklin in 1766, it was the beginning of a friendship that would have an enormous impact on science. Franklin's enthusiasm about his experiments with electricity convinced Priestley to conduct his own experiments. Priestley developed an improved technique for isolating gases in a sealed glass vessel. Using a magnifying glass to focus the rays of the sun on a piece of mercuric oxide, he discovered a gas that made a candle burn more brightly, while all the other gases he tested put out the candle's flame. Priestley did not appreciate the full implications of his discovery, however. When he told the French chemist Antoine Lavoisier about his discovery, Lavoisier repeated Priestley's experiments and was able to prove that air was not an element but was made up of various parts, and that combustion required the presence of Priestley's gas. Lavoisier gave the element its name, oxygen.