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MITSCHERLICH, EILHARDT (1794–1863)

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Originally appearing in Volume V18, Page 628 of the 1911 Encyclopedia Britannica.
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MITSCHERLICH, EILHARDT (1794–1863) , See also:German chemist, was See also:born on the 7th of See also:January 1794 at Neuende near See also:Jever, in the See also:grand duchy of See also:Oldenburg, where his See also:father was pastor. His See also:uncle, CHRISTOPH WILHELM MITSCHERLICH (176o-1854), See also:professor at See also:Gottingen, was in his See also:day a celebrated See also:scholar. He was educated at Jever under the historian F. C. See also:Schlosser, when he went to See also:Heidelberg in 1811, devoted himself to See also:philology, giving See also:special See also:attention to the See also:Persian See also:language. In 1813 he went to See also:Paris to obtain permission to join the See also:embassy which See also:Napoleon I. was to send to See also:Persia. The events of 1814 put an end to this, and Mitscherlich resolved to study See also:medicine in See also:order that he might enjoy that freedom of travel usually allowed in the See also:East to physicians. He began at Gottingen with the study of See also:chemistry, and this so arrested his attention that he gave up the See also:journey to Persia. From his Gottingen days See also:dates the See also:treatise on certain parts of Persian See also:history, compiled from See also:MSS. in the university library 'and published in Persian and Latin in 1814, under the See also:title Mirchondi historia Thaheridarum historicis nostris hucusque incognitorum Persiae principum. In 1818 he went to See also:Berlin and worked in the laboratory of H. F. See also:Link (1767–1851).

There he made analyses of See also:

phosphates and phosphites, arsenates and arsenites, See also:con-firming the conclusions of J. J. See also:Berzelius as to their See also:composition; and his observation that corresponding phosphates and arsenates crystallize in the same foam was the germ from which See also:grew the theory of isomorphism which he communicated to the Berlin See also:Academy in See also:December 1819. In that See also:year Berzelius suggested Mitscherlich to the See also:minister See also:Altenstein as successor to M. H. See also:Klaproth at Berlin. Altenstein did not immediately carry out this proposal, but he obtained for Mitscherlich a See also:government See also:grant to enable him to continue his studies in Berzelius's laboratory at See also:Stockholm. He returned to Berlin in 1821, and in the summer of 1822 he delivered his first lecture as extraordinary professor of chemistry in the university, where in 1825 he was appointed See also:ordinary professor. In the course of an investigation into the slight See also:differences discovered by W. H. See also:Wollaston in the angles of the rhombohedra of the See also:carbonates isomorphous with calc-spar, he observed that the See also:angle in the See also:case of calc-spar varied with the temperature. On extending his inquiry to other aelotropic crystals he observed a similar variation, and was thus led, in 1825, to the See also:discovery that aelotropic crystals, when heated, expand unequally in the direction of dissimilar axes.

In the following year he discovered the See also:

change, produced by change of temperature, in the direction of the optic axes of selenite. His investigation (also in 1826) of the two crystalline modifications of See also:sulphur threw much See also:light on the fact that the two minerals calc-spar and See also:aragonite have the same composition but different crystalline forms, a See also:property which Mitscherlich called dimorphism. In 1833 he made a See also:series of careful determinations of the vapour densities of a large See also:Drawn from a photograph taken by Father J. Braun (reproduced in See also:Die liturgiscite Gewandung). By permission of B. See also:Herder. Reproduced by See also:kind permission of the See also:Archbishop of See also:Westminster. number of volatile substances, confirming See also:Gay-Lussac's See also:law. He obtained selenic See also:acid in 1827 and showed that its salts are isomorphous with the sulphates, while a few years later he proved that the same thing is true of the manganates and the sulphates, and of the permanganates and the perchlorates. He investigated the relation of See also:benzene to benzoic acid and to other derivatives. In 1829—1830 he published his Lehrbuch der Chemie, which embodied many See also:original observations. His See also:interest in See also:mineralogy led him to study the See also:geology of volcanic regions, and he made frequent visits to the See also:Eifel with a view to the discovery of a theory of volcanic See also:action.

He did not, however, publish any papers on the subject, though after his See also:

death his notes were arranged and published by Dr. J. L. A. See also:Roth in the See also:Memoirs of the Berlin Academy (1866). In December 1861 symptoms of See also:heart-disease made their See also:appearance, but he was able to carry on his academical See also:work till December 1862. He died at Schonberg near Berlin, on the 28th of See also:August 1863. Mitscherlich's published papers are chiefly to be found in the Abhandlungen of the Berlin Academy, in See also:Poggendorff's Annalen, and in the Annales de chimie et de physique. The 4th edition of the Lehrbuch der Chemie was published in 1844—1847, a 5th was begun in 1855, but was not completed.

End of Article: MITSCHERLICH, EILHARDT (1794–1863)

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