The Encyclopedia Americana (1920)/Kohlrausch, Friedrich

KOHLRAUSCH, kōl'roush, Friedrich, German physicist: b. Rinteln, 14 Oct. 1840; d. Marburg, 1910. He studied at Erlangen and Göttingen, and was teacher (docent) at the Frankfort Physikalischer Verein (1864). He became assistant professor (1870) and was appointed professor, successively, of the Polytechnikum, Zürich (1870); Darmstädter Polytechnikum (1871), and at Wurzburg (1875) and Strassburg (1888). He was appointed president of the Physikalischtechnischen Austalt (Imperial Physico-technical Institute) of Berlin (1895), and honorary professor of the Berlin University (1899). In 1905 he retired to reside at Marburg. His work was chiefly in the realm of electric currents, resistance, the constitution of galvanic currents, the defining of the Ohm and electro-chemical equivalents, thermo-electricity and conductivity of heat, total reflection of light, elasticity of matter, and especially reaction of elasticity. He constructed numerous magnetic and electric measuring instruments, a bifilar-magnetometer, an intensity-variation meter, a voltmeter, a switch-rheostat, etc. His exposition of the most important methods of measurements in physics is expounded in his ‘Leitfaden der praktischen Physik’ (Leipzig 1870; 10th ed., 1905), and ‘Lehrbuch der praktischen Physik’ (1910) which latter was a 10th revised edition. His work in the field of electrolysis has been termed “epoch-making.” He wrote also ‘Ueber die Leitungswiderstand des Quicksilbers’ (Munich 1888); ‘Das Leitvermögen der Elektrolyte, bis besondere der Lösungen’ (Leipzig 1898); ‘Kleiner Leitfaden der praktischen Physik’ (lib. 1900). The latter is an elementary work based on his ‘Leitfaden.’