Joseph Priestley Essay, Research Paper

Joseph Priestley was born in England on March 13, 1733, and showed a great talent for science and languages from an early age. Priestley performed many important scientific experiments, among them the discovery that the gas produced by the fermentation of grain (later identified as carbon dioxide) could be dissolved in water to produce the pleasant drink called seltzer. Also, as a result of meeting Benjamin Franklin in London in 1766, Priestley became interested in electricity and was the first to observe that graphite was an electrical conductor. However, Priestley’s greatest discovery occurred in 1774 when Priestley heated mercury in air and found that it became coated with “red rust of mercury.” He then took this and heated it separately with the result that it was converted back to mercury. The “air” given off was captured over mercury. He observed that candles burned very brightly in it and that a mouse placed in a sealed vessel with it could breathe it much longer than ordinary air. A strong believer in the phlogiston theory, Priestley considered it to be air from which the phlogiston had been removed. His more quantitative experiments convinced him that ordinary air is one fifth dephlogisticated air, the rest considered by him to be phlogiston. Because of his nonconformist political views (he supported both the American and French revolutions), he was forced to leave England (a mob burned his house in Birmingham in 1791). He spent his last decade peacefully in the United States, and died in 1804.