Friedrich Wilhelm Georg Kohlrausch (14.10.1840-17.01.1910) was a German experimental physicist and a member of the Berlin Academy of Sciences (1895). He was the son of R. Kohlrausch. He was born in Rinteln. He graduated from the University of Göttingen (1863). In 1866—70 he was professor at the University of Göttingen, in 1870 — 71 at the Zurich Polytechnic, in 1871—75 in Darmstadt and in 1875 — 88 at the universities of Würzburg and Strasbourg. In 1895—1905 he was director of the Physico-Technical Institute and professor at the university in Berlin (from 1900).
His research was in the fields of electricity, magnetism, optics and electrochemistry. He did much to improve instruments and methods for measuring electrical and magnetic quantities. He developed a method of measuring electric current in absolute units and a method of measuring the electrical resistance of electrolytes (the Kohlrausch bridge), as well as methods and instruments for recording changes in the Earth's magnetic field, in particular a portable bifilar magnetometer, a local variometer and others. He studied the electrical conductivity of electrolytes and established (1874) that it increases as the temperature rises. He discovered (1879) the independence of the migration of ions in electrolytes at infinite dilution (Kohlrausch's law). He determined the electrochemical equivalent of silver. He studied elastic aftereffect. He built a total internal reflection refractometer.
A foreign member of the St Petersburg Academy of Sciences (1894).