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TENNANT, SMITHSON (1761–1815), chemist, born on 30 Nov. 1761 at Selby, Yorkshire, was son of Calvert Tennant, vicar of Selby, by his wife Mary Daunt. After receiving his early education in the grammar schools at Tadcaster and Beverley, he studied medicine in 1781 at Edinburgh, where he attended the lectures of Joseph Black [q. v.] In 1782 he became pensioner and then fellow commoner at Christ's College, Cambridge, where he studied chemistry and botany, and satisfied himself of the truth of the antiphlogistic theory of combustion, which was not at that time generally accepted in England. In 1784 he travelled in Denmark and Sweden, and visited the Swedish chemist Scheele. He was elected a fellow of the Royal Society in 1785, and in 1786 he removed from Christ's College to Emmanuel. He graduated M.B. in 1788. During the following years he travelled in Europe, and on his return took up his residence in London in the Temple, and in 1796 graduated M.D. at Cambridge. At this period he became interested in agricultural matters, and, after some preliminary trials in Lincolnshire, purchased land in Somerset, near Cheddar, which he farmed with some success, although resident for the greater part of the year in London. He lived a very retired life, occupied in literary and scientific studies. In 1804 he was awarded the Copley medal of the Royal Society, in recognition of his investigations. In 1812 he delivered a course of informal lectures on mineralogy in his chambers to a number of friends. In 1813 he was appointed professor of chemistry at Cambridge, and in 1814 delivered his first and only course of lectures, which met with a good reception. On 22 Feb. 1815 he accidentally met his death in France, near Boulogne, through the collapse of a bridge over which he was riding.

Although Tennant's published work is small in volume, it includes several discoveries of capital importance. In his first paper (Phil. Trans. 1791, ii. 182) he demonstrated that when marble is heated with phosphorus, the carbon of the fixed air which it contains is liberated. This experiment affords the analytical proof of the composition of fixed air (carbonic acid gas) which had been synthetically proved by Lavoisier. In his next paper, ‘On the Nature of the Diamond’ (ib. 1797, p. 123), Tennant proved that this precious stone consists of carbon, and yields the same weight of carbonic acid gas as had been previously obtained by Lavoisier from an equal weight of charcoal. In 1799 he showed (ib. 1799, ii. 305) that the lime from many parts of England contains magnesia, and that this substance and its carbonate are extremely injurious to vegetation. In 1804 he published his discovery of two new metals, osmium and iridium, which occur in crude platinum and are left behind when the metal is dissolved in aqua regia (ib. 1804, p. 411).

Tennant was a man of wide culture and of severe taste in literature and arts. He was a brilliant conversationalist, and ‘in quick penetration united with soundness and accuracy of judgment he was perhaps without an equal.’ In addition to the papers mentioned above he published the following: ‘On the Action of Nitre upon Gold and Platina’ (ib. 1797, ii. 219); ‘On the Composition of Emery’ (ib. 1802, p. 398); ‘Notice respecting Native Concrete Boracic Acid’ (Geol. Soc. Trans. 1811, p. 389); ‘On an Easier Mode of procuring Potassium’ (Phil. Trans. 1814, p. 578); ‘On the Means of procuring a Double Distillation by the same Heat’ (ib. 1814, p. 587).

[Memoir in Annals of Philosophy, 1815, vi. 1, 81. This was reprinted for private circulation with a few additions under the title ‘Some Account of the late Smithson Tennant,’ 1815. It is stated that it was drawn up by some of his friends, but the main portion of the work was due to Whishaw.]

A. H.-n.

Dictionary of National Biography, Errata (1904), p.263
N.B.— f.e. stands for from end and l.l. for last line

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63 i 55-56 Tennant, Smithson: omit in Wensleydale