PRIESTLEY, JOSEPH (1733-1804), English chemist and Nonconformist minister, was born on March 13, 1733, at Field head, a hamlet in the West Riding of Yorkshire. His father, Jonas Priestley, a woollen-cloth dresser of moderate means, was a Non conformist. At the age of 12 the son was sent to a neigh bouring grammar school, but later Kirkby, a minister at Heck mondwike, took entire charge of his education. From the age of 16 to nearly 20 he worked at Chaldee and Syriac, began to read Arabic, and mastered 'S Gravesande's Natural Philosophy, to gether with various textbooks of logic and metaphysics. He also learned French, German and Italian. In 1752 he went to Daventry to attend the Nonconformist academy there.
In 1755 he was appointed to a small congregation at Needham Market, in Suffolk. In 1758 he obtained a more congenial congre gation at Nantwich, where he opened a school at which the ele mentary lessons were varied with experiments in natural philoso phy. Three years later he removed to Warrington as classical tutor in a new academy, and there he attended lectures on chemistry by Dr. M. Turner of Liverpool and pursued the studies in electricity which gained him the fellowship of the Royal Society in 1766 and supplied him with material for his History o) Electricity. In 1767 he was appointed to the charge of Mill Hill Chapel at Leeds, where he wrote many political tracts attacking the Government policy towards the American colonies. He also began his researches into "different kinds of airs," getting a plenti ful supply of "fixed air" from a brewery next door to his house.
In 1772, the year in which he was chosen a foreign associate of the French academy of sciences, Priestley accepted the position of librarian and literary companion to Lord Shelburne (afterwards st Marquess of Lansdowne) at Calne, with a salary of .125o a year and a house. He travelled with his patron on the Continent and in Oct. 1774 he met Lavoisier and his friends in Paris and gave them an account of the experiment by which on the previous Aug. I he had prepared "dephlogisticated air" (oxygen). In 178o he left Lord Shelburne, who allowed him an annuity of II so for life, and settling at Birmingham was appointed junior minister of the New Meeting Society. There he found friends in Matthew Boul ton, James Keir, James Watt and Erasmus Darwin. On July 1791 the Constitutional Society of Birmingham arranged a dinner to celebrate the anniversary of the fall of the Bastille. Priestley, according to his own account, "had little to do with it." But his predilections in favour of the revolutionists were notorious, and the mob seized the occasion to burn his chapel and sack his house at Fairhill. He and his family escaped, but his possessions were destroyed and the labour of years annihilated. He retreated to London, where he felt safe, though he continued to be an object of "troublesome attention," and even the fellows of the Royal Society shunned him. He received an invitation to become morn ing preacher at Gravel Pit Chapel, Hackney, and there he re mained until 1794, when he determined to emigrate to America. Settling at Northumberland, Pennsylvania, he lived there for nearly ten years, until his death on Feb. 6, Priestley made very important contributions to pneumatic chemistry—the study of gases—and was the inventor of the "pneumatic trough" which allowed gases to be collected and examined. By heating spirits of salt he obtained "marine acid air" (hydrochloric acid gas), and he was able to collect it because he happened to use mercury, instead of water, in his pneumatic trough. Then he treated oil of vitriol in the same way, but got
nothing until by accident he dropped some mercury into the liquid, when "vitriolic acid air" (sulphur dioxide) was evolved. Again he heated fluorspar with oil of vitriol, as K. W. Scheele had done, and because he was employing a glass vessel he got "fluor acid air" (silicon fluoride). Heating spirits of hartshorn, he was able to collect "alkaline air" (ammonia), again because he was using mercury in his pneumatic trough ; then, trying what would happen if he passed electric sparks through the gas, he decomposed it into nitrogen and hydrogen, and "having a notion" that mixed with hydrochloric acid gas it would produce a "neutral air," per haps much the same as common air, he synthetized sal ammoniac. Dephlogisticated air (oxygen) he prepared in Aug. 1774 by heat ing red oxide of mercury with a burning-glass, and he found that in it a candle burnt with a remarkably vigorous flame and mice lived longer than in an equal volume of ordinary air. He con cluded that it was not common air, but the substance "in much greater perfection," that rendered common air respirable and a supporter of combustion. Of the analogy between combustion and respiration—both true phlogistic processes in his view—he had convinced himself three years before, and his paper, "On Different Kinds of Air" (Phil. Trans., 1772) described experiments which showed that growing plants are able to "restore" air which has been vitiated, whether by being breathed or by having candles burnt in it. He noted that when hydrogen and oxygen were ex ploded together a mist or dew coated the inside of the vessel, but it was Cavendish who showed that the dew consisted of water.
Priestley had an unusual gift, as well as a passion, for experi menting, although he had received no scientific education; prob ably for this reason he supported the doctrine of phlogiston to the very last in spite of the fact that his own researches had probably given Lavoisier (q.v.) the clue to the oxygen theory of combustion. But although his theoretical knowledge was weak his observations and experiments had a profound influence on the development of chemistry.
Priestley was a most voluminous writer, and his works (excluding his scientific writings) as collected and edited by his friend J. T. Rutt in 1857-32 fill 25 octavo volumes. His chief theological and philo sophical works were Institutes of Natural and Revealed Religion (3 vols., 1772-74) ; History of the Corruption of Christianity (2 vols., 5782) ; General History of the Christian Church to the Fall of the Western Empire, vols. i. and ii. (179o), vols. iii. and iv. (18o2—o3) ; and Disquisitions relating to Matter and Spirit ( I 777) His chief books on chemistry were six volumes of Experiments and Observations on different Kinds of Air, published between 1774 and 1786; Experiments on the Generation of Air from Water (5793); Experiments and Observations relating to the Analysis of Atmospheric Air, and Considerations on the Doctrine of Phlogiston established and that of the Composition of Water refuted (i800). He also published (1767) a treatise on the History and Present State of Electricity, which embodies some original work, and (1772) a History of Discoveries relating to Vision, Light and Colours, which is a mere compilation.
See also T. E. Thorpe, Joseph Priestley (1906), 0. Lodge, "Joseph Priestley" in Nine Famous Birmingham Men (ed. J. H. Muirhead, 1909).