Kohlrausch was a professor of physics at the universities of Göttingen (1866–70) and Darmstadt (1871–75), among other schools. In 1874 he demonstrated that an electrolyte has a definite and constant amount of electrical resistance. By observing the dependence of conductivity upon dilution, he could determine the transfer velocities of the ions (charged atoms or molecules) in solution. He later served as professor of physics at the universities of Würzburg (1875–88) and Strassburg (1888–95) and joined the faculty of the University of Berlin in 1895.