Kohlrausch, Friedrich Wilhelm Georg

Born Oct. 14, 1840, in Rinteln, Lower Saxony; died Jan. 17, 1910, in Marburg. German physicist. Member of the Berlin Academy of Sciences (1895).

In 1863, Kohlrausch graduated from the University of Göttingen, becoming a professor there in 1866. From 1870 he was a professor in Zürich, and from 1888 in Strasbourg. After the death of H. von Helmholtz, he was director of the Physicotechnical Institute in Berlin (1895–1905).

Kohlrausch’s scientific works were devoted to electric and magnetic measurements and to electrolysis and thermoelectricity. Together with W. Weber he developed a method of measuring electric currents in absolute units and determined the ratio of the values of the charge of a capacitor expressed in electrical and magnetic units and discovered that it was numerically equal to the speed of light. He proposed a method for determining the electric resistance of electrolytes, established the law of the independence of the motion of ions in electrolytes (Kohlrausch law), and developed methods and instruments for measuring changes in the earth’s magnetic field. He derived the laws of elastic aftereffect on the basis of his experiments.