Priestley's hundred of experiments on different types of "air" led to the identification of numerous gases, including ammonia, nitrogen dioxide, and (most importantly) oxygen, which he obtained by heating mercuric oxide. Although the Swedish chemist Scheele had succeeded in isolating oxygen at least two years before Priestley, Priestley has long been credited with the discovery of oxygen, as he was the first to publish his discovery. Priestley's experiments with gases led Cavendish and Watt to discover the compound nature of water, and it was this revelation, coupled with Priestley's isolation of oxygen, that formed the experimental basis of Lavoisier's new oxidation chemistry.
Dibner, Heralds, 40; DSB; Norman Library of Science, 1750.
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