Physics, asked by sreeja7, 1 year ago

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Answered by nikhil497146
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Priestley entered the service of the Earl of Shelburne in 1773 and it was while he was in this service that he discovered oxygen. In a classic series of experiments he used his 12inch "burning lens" to heat up mercuric oxide and observed that a most remarkable gas was emitted. In his paper published in the Philosophical Transactions of the Royal Society in 1775 he refers to the gas as follows: "this air is of exalted nature…A candle burned in this air with an amazing strength of flame; and a bit of red hot wood crackled and burned with a prodigious rapidity, exhibiting an appearance something like that of iron glowing with a white heat, and throwing sparks in all directions. But to complete the proof of the superior quality of this air, I introduced a mouse into it; and in a quantity in which, had it been common air, it would have died in about a quarter of an hour; it lived at two different times, a whole hour, and was taken out quite vigorous."
Although oxygen was his most important discovery, Priestley also described the isolation and identification of other gases such as ammonia, sulphur dioxide, nitrous oxide and nitrogen dioxide.
By 1780 the working relationship between Priestley and the Earl of Shelburne had cooled somewhat and he decided to move with his family to Birmingham, where he became preacher at the New Meeting House. This was one of the most liberal congregations in England. For Priestley his time at Birmingham was among the happiest in his life.
He soon became involved with the Lunar Society - a small group of academics, scientists and industrialists with wide ranging interests who were prominent in spearheading the Industrial Revolution in England. The Lunar Society was so named because its members met at full moon thereby facilitating travelling home in the dark after the meetings. Fellow members of the Lunar Society included Matthew Boulton, Erasmus Darwin (grandfather of Charles and also a pioneer in the theory of evolution), James Watt and Josiah Wedgwood.
Although Priestley played an active role in the Lunar Society his interests turned more and more towards theology. He became an active dissenter with outspoken criticism of the established church. These were dangerous times to be alive with the French Revolution (1789-91), which Priestley supported, sending shock waves around Europe. In 1791 on the second anniversary of the storming of the Bastille a "Church and King" mob in Birmingham destroyed the New Meeting House as well as Priestley's house and laboratory. He barely escaped with his life and most of his equipment and records were lost. Priestley briefly joined a dissenting group in London at Hackney but after renewed vitriol against him and his family he emigrated to the United States of America in 1794.
He was warmly welcomed in America and offered the chair of chemistry at the University of Pennsylvania, which had been founded by Benjamin Franklin. Priestley declined and settled in Northumberland, Pennsylvania in an area intended for British émigrés fleeing political persecution. He was befriended by Thomas Jefferson, who became President of the United States in 1800. However, Priestley's final years were sad and lonely; his favourite son died in 1795 and his wife a year later. He himself died on the 5th February 1804 aged seventy-one and is buried in Northumberland where his house has now been turned into a museum.
Priestley should be included in any pantheon of scientists. The bicentenary of his death is an opportune time to reassess his life and work and several events are planned during the year. He possessed enormous scientific skills and originality of thought as well as having the courage to promote unpopular views. He was a man of rare insight and talent.
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