Friedrich Kohlrausch
Encyclopedia
Friedrich Wilhelm Georg Kohlrausch (October 14, 1840 – January 17, 1910) was a German
physicist
who 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.
Nowadays, Friedrich Kohlrausch is classed as one of the most important experimental physicists. His early work helped to extend the absolute system of Carl Friedrich Gauss
and Wilhelm Weber
to include electrical and magnetic measuring units.
, Friedrich Wilhelm Georg Kohlrausch was born on October 14, 1840, in Rinteln
, Germany
. After studying physics at Erlangen
and Göttingen
, Friedrich Kohlrausch completed his doctorate in Göttingen
.
, Kohlrausch was appointed a professor of physics at the University of Göttingen (1866-70).
During 1870 Kohlrausch became a professor at ETH Zurich
in Switzerland
. One year later, he moved to the Darmstadt University of Technology
in Germany
.
In 1875 he responded to an offer from the University of Würzburg
in southern Germany
, where he subsequently conducted his experiments in quantity determination and the conductivity of electrolytes. From 1888 he researched and taught at Strasbourg University.
He refused a professorship at the Humboldt University in Berlin
in 1894, but from 1900 he was also a professor there. He was elected a member of the Royal Swedish Academy of Sciences
during 1902.
, Zurich
, and Darmstadt
; Svante Arrhenius
, Wilhelm Ostwald
and Jacobus Henricus van 't Hoff
, the original Ionists, all trained with methods and equipment of Kohlrauschian lineage. Moreover, because Kohlrausch also continued to test and confirm the Ionist theory after it had been first proposed, his work tied "measuring physics" and its consequent capability of producing plenty of empirical data to the results and methods of the Ionists and their devotees.
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 used alternating current
to prevent the deposition of electrolysis products; this enabled him to obtain very precise results.
From 1875 to 1879, he examined numerous salt
solutions, acid
s and solutions of other materials. His efforts resulted in the law of the independent migration of ions, that is, 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 showed for weak (incompletely dissociated) electrolytes that the more dilute a solution, the greater its molar conductivity
due to increased ionic dissociation
.
as President of the Physikalisch-Technische Reichsanstalt (PTR – Imperial Physical Technical Institute), an office which he held until 1905.
Here, as in the past, his activities were focused on experimental and instrumental physics: he constructed instruments
and devised new measuring techniques to examine electrolytic conduction in solutions. He concluded the setup of the PTR, a task which had not yet been completed on the death of its first president. He introduced fixed regulations, work schedules and working hours for the Institute.
Under direction of Kohlrausch , the PTR created numerous standards and calibration standards which were also used internationally outside Germany
.
Kohlrausch was intent on creating optimum working conditions in the laboratories and to shield the labs from unwanted external influences. For six years, for instance, he fought against a streetcar line which was due to be laid near the PTR. However, before the streetcar was to make its first journey, the institute succeeded in developing an astatic torsion
magnetometer
which was uninfluenced by disturbing electromagnetic field
s. The use of this instrument and the shielded wire galvanometer
developed by du Bois and Rubens meant that precision electrical and magnetic work continued to be possible.
Over the years, Kohlrausch added experiments which met the needs of physical chemistry and electrical technology in particular. He improved precision measuring instruments and developed numerous measuring methods in almost all of the fields of physics known during his lifetime, including a reflectivity meter, a tangent galvanometer, and various types of magnetometers and dynamometers. The Kohlrausch bridge, which he invented at that time for the purpose of measuring conductivity, is still well known today.
Like Helmholtz and Siemens, Kohlrausch also saw the possibilities inherent in applied and basic research in the natural sciences and technology. He lay the foundations for scientific knowledge which promoted and advanced industry and technology. The PTR developed standardized precision instruments for university research institutes and industrial laboratories. It introduced uniform electrical units for Germany and also played a significant role in their international usage. In the period to 1905, there were many examples of the importance of the PTR for German industry, in particular for the high technologies of the time – the electrical, optical and mechanical industries.
Overall, Kohlrausch was involved in the measurement of electrical, magnetic and electrochemical phenomena for almost 50 years. In 1905 Kohlrausch retired from his post as President of the PTR.
Friedrich Kohlrausch died in Marburg
on January 17, 1910 at the age of 70.
. It contained not only descriptions of experiments, experimental setups and measuring techniques, but also tables of physical quantities. It was issued in many editions (the 9th enlarged and revised edition of 1901 being entitled Lehrbuch der praktischen Physik; a more elementary work based on it being entitled Kleiner Leitfaden der praktischen Physik) and translated into English. It was considered the standard work on physical laboratory methods and measurements.
To this day, the textbook Praktische Physik (Practical Physics), which originated in Kohlrausch's Leitfaden der praktischen Physik, is standard reading for physicists and engineers in Germany
. This is attributable, above all, to the detailed descriptions provided of the measuring methods that form the basis of technical and experimental applications in many fields in physics.
Kohlrausch was also the author of Ueber den absoluten Leitungswiderstand des Quecksilbers (On the electrical resistance of mercury, 1888), and of many papers contributed to the Annalen der Physik und Chemie, and other scientific journals.
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
who investigated the conductive properties of electrolytes and contributed to knowledge of their behaviour. He also investigated elasticity
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....
, thermoelasticity, and thermal conduction as well as magnetic and electrical precision measurements.
Nowadays, Friedrich Kohlrausch is classed as one of the most important experimental physicists. His early work helped to extend the absolute system of Carl Friedrich Gauss
Carl Friedrich Gauss
Johann Carl Friedrich Gauss was a German mathematician and scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics.Sometimes referred to as the Princeps mathematicorum...
and Wilhelm Weber
Wilhelm Eduard Weber
Wilhelm Eduard Weber was a German physicist and, together with Carl Friedrich Gauss, inventor of the first electromagnetic telegraph.-Early years:...
to include electrical and magnetic measuring units.
Education
Son of Rudolf KohlrauschRudolf Kohlrausch
Rudolf Hermann Arndt Kohlrausch was a German physicist.-Biography:He was a native of Göttingen, the son of educator Heinrich Friedrich Theodor Kohlrausch...
, Friedrich Wilhelm Georg Kohlrausch was born on October 14, 1840, in Rinteln
Rinteln
Rinteln is a small town in Lower Saxony, Germany. It is located on the banks of the Weser river above the Porta Westfalica. Population: 28,500.It is accessed by the A2 autobahn .-History:...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. After studying physics at Erlangen
Erlangen
Erlangen is a Middle Franconian city in Bavaria, Germany. It is located at the confluence of the river Regnitz and its large tributary, the Untere Schwabach.Erlangen has more than 100,000 inhabitants....
and Göttingen
Göttingen
Göttingen is a university town in Lower Saxony, Germany. It is the capital of the district of Göttingen. The Leine river runs through the town. In 2006 the population was 129,686.-General information:...
, Friedrich Kohlrausch completed his doctorate in Göttingen
Göttingen
Göttingen is a university town in Lower Saxony, Germany. It is the capital of the district of Göttingen. The Leine river runs through the town. In 2006 the population was 129,686.-General information:...
.
Teaching
After a two-year work as a lecturer in FrankfurtFrankfurt
Frankfurt am Main , commonly known simply as Frankfurt, is the largest city in the German state of Hesse and the fifth-largest city in Germany, with a 2010 population of 688,249. The urban area had an estimated population of 2,300,000 in 2010...
, Kohlrausch was appointed a professor of physics at the University of Göttingen (1866-70).
During 1870 Kohlrausch became a professor at ETH Zurich
ETH Zurich
The Swiss Federal Institute of Technology Zurich or ETH Zürich is an engineering, science, technology, mathematics and management university in the City of Zurich, Switzerland....
in Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
. One year later, he moved to the Darmstadt University of Technology
Darmstadt University of Technology
The Technische Universität Darmstadt, abbreviated TU Darmstadt, is a university in the city of Darmstadt, Germany...
in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
In 1875 he responded to an offer from the University of Würzburg
University of Würzburg
The University of Würzburg is a university in Würzburg, Germany, founded in 1402. The university is a member of the distinguished Coimbra Group.-Name:...
in southern Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, where he subsequently conducted his experiments in quantity determination and the conductivity of electrolytes. From 1888 he researched and taught at Strasbourg University.
He refused a professorship at the Humboldt University in Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
in 1894, but from 1900 he was also a professor there. He was elected a member of the Royal Swedish Academy of Sciences
Royal Swedish Academy of Sciences
The Royal Swedish Academy of Sciences or Kungliga Vetenskapsakademien is one of the Royal Academies of Sweden. The Academy is an independent, non-governmental scientific organization which acts to promote the sciences, primarily the natural sciences and mathematics.The Academy was founded on 2...
during 1902.
Research work
Kohlrausch was an important researcher of electrochemistry for many reasons. First, the experiments from which he deduced his law of independent migration of ions became canonical and disseminated from Kohlrausch's laboratories in GöttingenGöttingen
Göttingen is a university town in Lower Saxony, Germany. It is the capital of the district of Göttingen. The Leine river runs through the town. In 2006 the population was 129,686.-General information:...
, Zurich
Zürich
Zurich is the largest city in Switzerland and the capital of the canton of Zurich. It is located in central Switzerland at the northwestern tip of Lake Zurich...
, and Darmstadt
Darmstadt
Darmstadt is a city in the Bundesland of Hesse in Germany, located in the southern part of the Rhine Main Area.The sandy soils in the Darmstadt area, ill-suited for agriculture in times before industrial fertilisation, prevented any larger settlement from developing, until the city became the seat...
; Svante Arrhenius
Svante Arrhenius
Svante August Arrhenius was a Swedish scientist, originally a physicist, but often referred to as a chemist, and one of the founders of the science of physical chemistry...
, Wilhelm Ostwald
Wilhelm Ostwald
Friedrich Wilhelm Ostwald was a Baltic German chemist. He received the Nobel Prize in Chemistry in 1909 for his work on catalysis, chemical equilibria and reaction velocities...
and Jacobus Henricus van 't Hoff
Jacobus Henricus van 't Hoff
Jacobus Henricus van 't Hoff, Jr. was a Dutch physical and organic chemist and the first winner of the Nobel Prize in chemistry. He is best known for his discoveries in chemical kinetics, chemical equilibrium, osmotic pressure, and stereochemistry...
, the original Ionists, all trained with methods and equipment of Kohlrauschian lineage. Moreover, because Kohlrausch also continued to test and confirm the Ionist theory after it had been first proposed, his work tied "measuring physics" and its consequent capability of producing plenty of empirical data to the results and methods of the Ionists and their devotees.
Electrolyte conductivity in solution
In 1874 he demonstrated that an electrolyteElectrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
has a definite and constant amount of electrical resistance. By observing the dependence of conductivity upon dilution
Dilution
Dilution may refer to:* Reducing the concentration of a chemical* Serial dilution, a common way of going about this reduction of concentration* Homeopathic dilution* Dilution , an equation to calculate the rate a gas dilutes...
, he could determine the transfer velocities of the ions (charged atoms or molecules) in solution. He used alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
to prevent the deposition of electrolysis products; this enabled him to obtain very precise results.
From 1875 to 1879, he examined numerous salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
solutions, acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
s and solutions of other materials. His efforts resulted in the law of the independent migration of ions, that is, each type of migrating ion has a specific electrical resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
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 showed for weak (incompletely dissociated) electrolytes that the more dilute a solution, the greater its molar conductivity
Molar conductivity
Molar conductivity is defined as the conductivity of an electrolyte solution divided by the molar concentration of the electrolyte, and so measures the efficiency with which a given electrolyte conducts electricity in solution. Its units are siemens per meter per molarity, or siemens meter-squared...
due to increased ionic dissociation
Dissociation (chemistry)
Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller particles, ions, or radicals, usually in a reversible manner...
.
Measuring techniques & instruments
During 1895 he succeeded Hermann von HelmholtzHermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
as President of the Physikalisch-Technische Reichsanstalt (PTR – Imperial Physical Technical Institute), an office which he held until 1905.
Here, as in the past, his activities were focused on experimental and instrumental physics: he constructed instruments
Measuring instrument
In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the process of measurement gives a number relating the item...
and devised new measuring techniques to examine electrolytic conduction in solutions. He concluded the setup of the PTR, a task which had not yet been completed on the death of its first president. He introduced fixed regulations, work schedules and working hours for the Institute.
Under direction of Kohlrausch , the PTR created numerous standards and calibration standards which were also used internationally outside Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
Kohlrausch was intent on creating optimum working conditions in the laboratories and to shield the labs from unwanted external influences. For six years, for instance, he fought against a streetcar line which was due to be laid near the PTR. However, before the streetcar was to make its first journey, the institute succeeded in developing an astatic torsion
Torsion
The word torsion may refer to the following:*In geometry:** Torsion of a curve** Torsion tensor in differential geometry** The closely related concepts of Reidemeister torsion and analytic torsion ** Whitehead torsion*In algebra:** Torsion ** Tor functor* In medicine:** Ovarian...
magnetometer
Magnetometer
A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...
which was uninfluenced by disturbing electromagnetic field
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
s. The use of this instrument and the shielded wire galvanometer
Galvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
developed by du Bois and Rubens meant that precision electrical and magnetic work continued to be possible.
Over the years, Kohlrausch added experiments which met the needs of physical chemistry and electrical technology in particular. He improved precision measuring instruments and developed numerous measuring methods in almost all of the fields of physics known during his lifetime, including a reflectivity meter, a tangent galvanometer, and various types of magnetometers and dynamometers. The Kohlrausch bridge, which he invented at that time for the purpose of measuring conductivity, is still well known today.
Like Helmholtz and Siemens, Kohlrausch also saw the possibilities inherent in applied and basic research in the natural sciences and technology. He lay the foundations for scientific knowledge which promoted and advanced industry and technology. The PTR developed standardized precision instruments for university research institutes and industrial laboratories. It introduced uniform electrical units for Germany and also played a significant role in their international usage. In the period to 1905, there were many examples of the importance of the PTR for German industry, in particular for the high technologies of the time – the electrical, optical and mechanical industries.
Overall, Kohlrausch was involved in the measurement of electrical, magnetic and electrochemical phenomena for almost 50 years. In 1905 Kohlrausch retired from his post as President of the PTR.
Friedrich Kohlrausch died in Marburg
Marburg
Marburg is a city in the state of Hesse, Germany, on the River Lahn. It is the main town of the Marburg-Biedenkopf district and its population, as of March 2010, was 79,911.- Founding and early history :...
on January 17, 1910 at the age of 70.
Writings
In the University of Göttingen, Kohlrausch documented his practical experiments resulting in the book Leitfaden der praktischen Physik (Guidelines to Practical Physics), which was published in 1870 as the first book of its type in GermanyGermany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. It contained not only descriptions of experiments, experimental setups and measuring techniques, but also tables of physical quantities. It was issued in many editions (the 9th enlarged and revised edition of 1901 being entitled Lehrbuch der praktischen Physik; a more elementary work based on it being entitled Kleiner Leitfaden der praktischen Physik) and translated into English. It was considered the standard work on physical laboratory methods and measurements.
To this day, the textbook Praktische Physik (Practical Physics), which originated in Kohlrausch's Leitfaden der praktischen Physik, is standard reading for physicists and engineers in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. This is attributable, above all, to the detailed descriptions provided of the measuring methods that form the basis of technical and experimental applications in many fields in physics.
Kohlrausch was also the author of Ueber den absoluten Leitungswiderstand des Quecksilbers (On the electrical resistance of mercury, 1888), and of many papers contributed to the Annalen der Physik und Chemie, and other scientific journals.