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Eilhardt Mitscherlich

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MITSCHERLICH, EILHARDT German chemist, was born on Jan. 7, 1794 at Neuende near Jever, Olden burg, where his father was pastor. He was educated at Jever and went to Heidelberg in 181i ; he devoted himself to philology, and gave special attention to the Persian language. Mitscherlich resolved to study medicine in order that he might enjoy that freedom of travel usually allowed in the East to physicians. He began at Gottingen with the study of chemistry, and this so arrested his attention that he gave up the idea of a journey to Persia. From his Gottingen days dates the treatise on certain parts of Persian history, compiled from mss. in the university library and published in Persian and Latin in 1814, under the title Mirchondi historia Thaheridarum historicis nostris huiusque incognitorum Persiae principum. In 1818 he went to Berlin and worked in the laboratory of H. F. Link (1767-1851). There he made analyses of phosphates and phosphites, arsenates and arse nites, confirming the conclusions of J. J. Berzelius as to their composition; his observation that corresponding phosphates and arsenates crystallize in the same form was the germ from which grew the important theory of isomorphism which he communi cated to the Berlin academy in Dec. 1819. Shortly afterwards he went to Stockholm and studied under Berzelius ; 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 ordinary professor. He died at Schonberg, near Berlin, on Aug. 28, 1863.

In the course of Mitscherlich's crystallographic investigations he observed that the rhombohedral angles in the case of calc spar varied with the temperature, and that crystals, when heated expand unequally in the direction of dissimilar axes. His investi

gation (also in 1826) of the two crystalline modifications of sul phur brought to light the fact that certain substances could exist in different crystalline forms, a property which Mitscherlich called dimorphism. He obtained selenic 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 prepared benzene sulphonic acid (1833), nitrobenzene (1834) and investigated the relation of benzene to benzoic acid and to other derivatives (1835). In 1829-3o he published his Lehrbuch der Chemie, which embodied many original observations. His in terest in mineralogy led him to study the geology of volcanic re gions, and he tried to devise a theory of volcanic action. He did not, however, publish any papers on the subject, though after his death his notes were arranged and published by Dr. J. L. A. Roth in the Memoirs of the Berlin Academy (1866).

Mitscherlich's published papers are chiefly to be found in the Ab handlungen of the Berlin academy ; in the Annalen der Physik and Chemie (ed. J. C. Puggendorf, Halle, 179o, etc.) ; and in the Annales de chimie et de physique (1816, etc.). The 4th edition of the Lehrbuch der Chemie was published in 1844-47, a 5th was begun in 1855 but was not completed. His Gesammelte Schriften were edited by A. Mitscherlich in 1896, who also published Erinnerung von Eilhardt Mitscherlich (1894). See also A. D. von Hofmann, Chemische Erin nerungen (1882).