On October 14, 1840, German physicist Friedrich Wilhelm Georg Kohlrausch was born. Kohlrausch investigated the conductive properties of electrolytes and contributed to knowledge of their behaviour. He also investigated elasticity, thermoelasticity, and thermal conduction as well as magnetic and electrical precision measurements.
Friedrich Kohlrausch studied physics at Erlangen and Göttingen, Germany. He was appointed professor of physics at the University of Göttingen in 1866 and became professor at ETH Zurich in Switzerland in 1870. During the following years, Kohlrausch also worked at the Darmstadt University of Technology and the University of Würzburg.
During his time at Würzburg, Kohlrausch conducted his influential research work on quantity determination and the conductivity of electrolytes. In 1874, Kohlrausch was able to demonstrate that an electrolyte has a definite and constant amount of electrical resistance. He observed the dependence of conductivity upon dilution and could determine the transfer velocities of the ions. He used alternating current to prevent the deposition of electrolysis products; this enabled him to obtain very precise results.
During the later 1870s, Friedrich Kohlrausch examined several salt solutions and further materials, resulting in the law of the independent migration of ions. It means that each type of migrating ion has a specific electrical resistance no matter what its original molecular combination may have been, and therefore that a solution’s electrical resistance was due only to the migrating ions of a given substances. Kohlrausch was able to demonstrate for weak electrolytes that the more dilute a solution, the greater its molar conductivity due to increased ionic dissociation.
Starting from 1888, Friedrich Kohlrausch taught at Strasbourg University and became a professor at the Humboldt University in Berlin in 1900. Two years later he was elected a member of the Royal Swedish Academy of Sciences.
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