Klaus Clusius
Encyclopedia
Klaus Clusius was a German
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...

 physical chemist from Breslau (Wrocław), Silesia
Province of Silesia
The Province of Silesia was a province of the Kingdom of Prussia from 1815 to 1919.-Geography:The territory comprised the bulk of the former Bohemian crown land of Silesia and the County of Kladsko, which King Frederick the Great had conquered from the Austrian Habsburg Monarchy in the 18th...

. During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, he worked on the German nuclear energy project, also known as the Uranium Club; he worked on isotope separation techniques and heavy water production. After the war, he was a professor of physical chemistry at the University of Zurich
University of Zurich
The University of Zurich , located in the city of Zurich, is the largest university in Switzerland, with over 25,000 students. It was founded in 1833 from the existing colleges of theology, law, medicine and a new faculty of philosophy....

.

Education

Clusius studied at the Technische Hochschule Breslau (today, the Wrocław University of Technology) from 1922 to 1926. He received his doctorate in 1926, under Arnold Eucken, who was the director of the physicochemical institute there; his thesis was on the specific heat of solids at low temperatures. From 1926 to 1929, he was Eucken’s teaching assistant. From 1929 to 1930, under a Rockefeller Foundation Fellowship, he did postdoctoral studies and research at the University of Oxford
University of Oxford
The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...

, with Cyril Norman Hinshelwood
Cyril Norman Hinshelwood
Sir Cyril Norman Hinshelwood OM PRS was an English physical chemist.Born in London, his parents were Norman Macmillan Hinshelwood, a chartered accountant, and Ethe Frances née Smith. He was educated first in Canada, returning in 1905 on the death of his father to a small flat in Chelsea where he...

, and at the Leiden University
Leiden University
Leiden University , located in the city of Leiden, is the oldest university in the Netherlands. The university was founded in 1575 by William, Prince of Orange, leader of the Dutch Revolt in the Eighty Years' War. The royal Dutch House of Orange-Nassau and Leiden University still have a close...

. He completed his Habilitation
Habilitation
Habilitation is the highest academic qualification a scholar can achieve by his or her own pursuit in several European and Asian countries. Earned after obtaining a research doctorate, such as a PhD, habilitation requires the candidate to write a professorial thesis based on independent...

, in 1931, at the Georg-August-Universität Göttingen under Eucken, who had been the director of the physicochemical institute there since 1929. He then became Eucken’s teaching assistant.

Career

In 1934, Clusius became an ausserordentlicher Professor (extraordinarius professor) at the Julius-Maximilians-Universität 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:...

. From 1936, he was an ordentlicher Professor (ordinarius professor) at the Ludwig-Maximilians-Universität München. At that time or later, he became Director of the Physikalisch-Chemischen Institut der Universität München (Physical Chemistry Institute of the University of Munich). At the University, he conducted major experiments on heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

, and he developed a thermodiffusion isotope separation tube, in 1938, with his younger colleague Gerhard Dickel.

In December 1938, the German chemists Otto Hahn
Otto Hahn
Otto Hahn FRS was a German chemist and Nobel laureate, a pioneer in the fields of radioactivity and radiochemistry. He is regarded as "the father of nuclear chemistry". Hahn was a courageous opposer of Jewish persecution by the Nazis and after World War II he became a passionate campaigner...

 and Fritz Strassmann
Fritz Strassmann
Friedrich Wilhelm "Fritz" Strassmann was a German chemist who, with Otto Hahn in 1938, identified barium in the residue after bombarding uranium with neutrons, which led to the interpretation of their results as being from nuclear fission...

 sent a manuscript to Naturwissenschaften
Die Naturwissenschaften
Naturwissenschaften is a monthly peer-reviewed scientific journal published by Springer on behalf of several learned societies.- History :...

reporting they had detected the element barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...

 after bombarding uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

 with neutrons; simultaneously, they communicated these results to Lise Meitner
Lise Meitner
Lise Meitner FRS was an Austrian-born, later Swedish, physicist who worked on radioactivity and nuclear physics. Meitner was part of the team that discovered nuclear fission, an achievement for which her colleague Otto Hahn was awarded the Nobel Prize...

, who had in July of that year fled to The Netherlands and then went to Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

. Meitner, and her nephew Otto Robert Frisch
Otto Robert Frisch
Otto Robert Frisch , Austrian-British physicist. With his collaborator Rudolf Peierls he designed the first theoretical mechanism for the detonation of an atomic bomb in 1940.- Overview :...

, correctly interpreted these results as being nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...

. Frisch confirmed this experimentally on 13 January 1939.

Paul Harteck
Paul Harteck
Paul Karl Maria Harteck was a German physical chemist. He was arrested by the allied British and American Armed Forces and incarcerated at Farm Hall for six months in 1945 under Operation Epsilon.-Education:Harteck studied chemistry at the University of Vienna and the Humboldt University of Berlin...

 was director of the physical chemistry department at the University of Hamburg
University of Hamburg
The University of Hamburg is a university in Hamburg, Germany. It was founded on 28 March 1919 by Wilhelm Stern and others. It grew out of the previous Allgemeines Vorlesungswesen and the Kolonialinstitut as well as the Akademisches Gymnasium. There are around 38,000 students as of the start of...

 and an advisor to the Heereswaffenamt (HWA, Army Ordnance Office). On 24 April 1939, along with his teaching assistant Wilhelm Groth
Wilhelm Groth
Wilhelm Groth was a German physical chemist. During World War II, he worked on the German nuclear energy project, also known as the Uranium Club; his main activity was the development of centrifuges for the enrichment of uranium. After the war, he was a professor of physical chemistry at the...

, Harteck made contact with the Reichskriegsministerium (RKM, Reich Ministry of War) to alert them to the potential of military applications of nuclear chain reactions. Two days earlier, on 22 April 1939, after hearing a colloquium paper by Wilhelm Hanle
Wilhelm Hanle
Wilhelm Hanle was a German experimental physicist. He is known for the Hanle effect. During World War II, he made contributions to the German nuclear energy project, also known as the Uranium Club...

 on the use of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

 fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...

 in a Uranmaschine (uranium machine, i.e., nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

), Georg Joos
Georg Joos
Georg Jakob Christof Joos was a German theoretical physicist. He wrote Lehrbuch der theoretischen Physik, first published in 1932 and one of the most influential theoretical physics textbooks of the 20th Century.-Education:Joos began his higher education in 1912 at the Technische Hochschule...

, along with Hanle, notified Wilhelm Dames, at the Reichserziehungsministerium
Reichserziehungsministerium
The Reichserziehungsministerium was officially known as the Reichsministerium für Wissenschaft, Erziehung und Volksbildung .-Background:...

(REM, Reich Ministry of Education), of potential military applications of nuclear energy. The communication was given to Abraham Esau
Abraham Esau
Robert Abraham Esau was a German physicist.After receipt of his doctorate from the University of Berlin, Esau worked at Telefunken, where he pioneered very high frequency waves used in radar, radio, and television, and he was president of the Deutscher Telefunken Verband...

, head of the physics section of the Reichsforschungsrat
Reichsforschungsrat
The Reichsforschungsrat was created in Germany in 1937 under the Education Ministry for the purpose of centralized planning of all basic and applied research, with the exception of aeronautical research...

(RFR, Reich Research Council) at the REM. On 29 April, a group, organized by Esau, met at the REM to discuss the potential of a sustained nuclear chain reaction
Nuclear chain reaction
A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating number of these reactions. The specific nuclear reaction may be the fission of heavy isotopes or the fusion of light isotopes...

. The group included the physicists Walther Bothe
Walther Bothe
Walther Wilhelm Georg Bothe was a German nuclear physicist, who shared the Nobel Prize in Physics in 1954 with Max Born....

, Robert Döpel
Robert Döpel
Georg Robert Döpel was a German experimental nuclear physicist. He was a participant in a group known as the “first Uranverein,” which was spawned by a meeting conducted by the Reichserziehungsministerium, in April 1939, to discuss the potential of a sustained nuclear reaction...

, Hans Geiger, Wolfgang Gentner
Wolfgang Gentner
Wolfgang Gentner was a German experimental nuclear physicist.Gentner received his doctorate in 1930 from the University of Frankfurt. From 1932 to 1935 he had a fellowship which allowed him to do postdoctoral research and study at Curie's Radium Institute at the University of Paris...

 (probably sent by Walther Bothe
Walther Bothe
Walther Wilhelm Georg Bothe was a German nuclear physicist, who shared the Nobel Prize in Physics in 1954 with Max Born....

), Wilhelm Hanle
Wilhelm Hanle
Wilhelm Hanle was a German experimental physicist. He is known for the Hanle effect. During World War II, he made contributions to the German nuclear energy project, also known as the Uranium Club...

, Gerhard Hoffmann
Gerhard Hoffmann
Gerhard Hoffmann was a German nuclear physicist. During World War II, he contributed to the German nuclear energy project, also known as the Uranium Club.-Education:...

, and Georg Joos
Georg Joos
Georg Jakob Christof Joos was a German theoretical physicist. He wrote Lehrbuch der theoretischen Physik, first published in 1932 and one of the most influential theoretical physics textbooks of the 20th Century.-Education:Joos began his higher education in 1912 at the Technische Hochschule...

; Peter Debye
Peter Debye
Peter Joseph William Debye FRS was a Dutch physicist and physical chemist, and Nobel laureate in Chemistry.-Early life:...

 was invited, but he did not attend. After this, informal work began at Göttingen by Joos, Hanle, and their colleague Reinhold Mannfopff; the group of physicists was known informally as the first Uranverein (Uranium Club) and formally as Arbeitsgemeinschaft für Kernphysik. The group’s work was discontinued in August 1939, when the three were called to military training.

The second Uranverein began after the HWA squeezed out the RFR of the REM and started the formal German nuclear energy project
German nuclear energy project
The German nuclear energy project, , was an attempted clandestine scientific effort led by Germany to develop and produce the atomic weapons during the events involving the World War II...

 under military auspices. The second Uranverein was formed on 1 September 1939, the day World War II began, and it had its first meeting on 16 September 1939. The meeting was organized by Kurt Diebner
Kurt Diebner
Kurt Diebner was a German nuclear physicist who is well known for directing and administrating the German nuclear energy project, a secretive program aiming to built weapon of mass destruction for the Nazi Germany during the course of World War II...

, former student of Gerhard Hoffmann
Gerhard Hoffmann
Gerhard Hoffmann was a German nuclear physicist. During World War II, he contributed to the German nuclear energy project, also known as the Uranium Club.-Education:...

 the University of Halle and advisor to the HWA, and held in Berlin. The invitees included Walther Bothe
Walther Bothe
Walther Wilhelm Georg Bothe was a German nuclear physicist, who shared the Nobel Prize in Physics in 1954 with Max Born....

, Siegfried Flügge
Siegfried Flügge
Siegfried Flügge was a German theoretical physicist and made contributions to nuclear physics. He worked at the Kaiser-Wilhelm Institut für Chemie and worked in the German Uranverein...

, Hans Geiger, Otto Hahn
Otto Hahn
Otto Hahn FRS was a German chemist and Nobel laureate, a pioneer in the fields of radioactivity and radiochemistry. He is regarded as "the father of nuclear chemistry". Hahn was a courageous opposer of Jewish persecution by the Nazis and after World War II he became a passionate campaigner...

, Paul Harteck
Paul Harteck
Paul Karl Maria Harteck was a German physical chemist. He was arrested by the allied British and American Armed Forces and incarcerated at Farm Hall for six months in 1945 under Operation Epsilon.-Education:Harteck studied chemistry at the University of Vienna and the Humboldt University of Berlin...

, Gerhard Hoffmann, Josef Mattauch
Josef Mattauch
Josef Mattauch was a German physicist known for his work in the investigation of the isotopic abundances by mass spectrometry. He developed the Mattauch isobar rule in 1934.-Mattauch-Herzog geometry mass spectrometer:...

, and Georg Stetter
Georg Stetter
Georg Stetter was an Austrian-German nuclear physicist. Stetter was Director of the Second Physics Institute of the University of Vienna. He was a principal member of the German nuclear energy project, also known as the Uranium Club. In the latter years of World War II, he was also the Director...

. A second meeting was held soon thereafter and included Klaus Clusius, Robert Döpel
Robert Döpel
Georg Robert Döpel was a German experimental nuclear physicist. He was a participant in a group known as the “first Uranverein,” which was spawned by a meeting conducted by the Reichserziehungsministerium, in April 1939, to discuss the potential of a sustained nuclear reaction...

, Werner Heisenberg
Werner Heisenberg
Werner Karl Heisenberg was a German theoretical physicist who made foundational contributions to quantum mechanics and is best known for asserting the uncertainty principle of quantum theory...

, and Carl Friedrich von Weizsäcker
Carl Friedrich von Weizsäcker
Carl Friedrich Freiherr von Weizsäcker was a German physicist and philosopher. He was the longest-living member of the research team which performed nuclear research in Germany during the Second World War, under Werner Heisenberg's leadership...

. Also at this time, the Kaiser-Wilhelm Institut für Physik (KWIP, Kaiser Wilhelm Institute for Physics, after World War II the Max Planck Institute for Physics
Max Planck Institute for Physics
Max Planck Institute for Physics is a physics institute in Munich, Germany that specializes in High Energy Physics and Astroparticle physics. It is part of the Max-Planck-Gesellschaft and is also known as the Werner Heisenberg Institute, after its first director.It was founded as the Kaiser Wilhelm...

), in Berlin-Dahlem
Dahlem (Berlin)
Dahlem is a locality of the Steglitz-Zehlendorf borough in southwestern Berlin. Until Berlin's 2001 administrative reform it was a part of the former borough of Zehlendorf. Dahlem is one of the most affluent parts of the city and home to the main campus of the Free University of Berlin with the...

, was placed under HWA authority, with Diebner as the administrative director, and the military control of the nuclear research commenced.

In 1939, Clusius and Dickel announced the separation of chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

 isotopes, an accomplishment which had been sought for decades. That same year, Clusius, Paul Harteck
Paul Harteck
Paul Karl Maria Harteck was a German physical chemist. He was arrested by the allied British and American Armed Forces and incarcerated at Farm Hall for six months in 1945 under Operation Epsilon.-Education:Harteck studied chemistry at the University of Vienna and the Humboldt University of Berlin...

, Rudolf Fleischmann
Rudolf Fleischmann
Rudolf Fleischmann was a German experimental nuclear physicist from Erlangen, Bavaria. He worked for Walther Bothe at the Physics Institute of the University of Heidelberg and then at the Institute for Physics of the Kaiser Wilhelm Institute for Medical Research...

, Wilhelm Groth
Wilhelm Groth
Wilhelm Groth was a German physical chemist. During World War II, he worked on the German nuclear energy project, also known as the Uranium Club; his main activity was the development of centrifuges for the enrichment of uranium. After the war, he was a professor of physical chemistry at the...

 and others initiated experiments with the Clusius-Dickel thermodiffusion isotope separation tube with uranium hexafluoride
Uranium hexafluoride
Uranium hexafluoride , referred to as "hex" in the nuclear industry, is a compound used in the uranium enrichment process that produces fuel for nuclear reactors and nuclear weapons. It forms solid grey crystals at standard temperature and pressure , is highly toxic, reacts violently with water...

. In 1942, with about four physical chemists, Clusius further explored isotope separation and conducted experiments on heavy water production problems.

During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, Clusius gave talks outside of the Third Reich, just as did Werner Heisenberg
Werner Heisenberg
Werner Karl Heisenberg was a German theoretical physicist who made foundational contributions to quantum mechanics and is best known for asserting the uncertainty principle of quantum theory...

.

From 1947 to 1963, Clusius was an ordinarius professor of physical chemistry at the Universität Zürich
University of Zurich
The University of Zurich , located in the city of Zurich, is the largest university in Switzerland, with over 25,000 students. It was founded in 1833 from the existing colleges of theology, law, medicine and a new faculty of philosophy....

.

Honors

Clusius received honors which included:
  • 1958 – Marcel-Benoist-Preis

  • Member of the Deutsche Akademie der Naturforscher Leopoldina

  • Honorary doctorate from the Technische Hochschule Hannover

Internal Reports

The following reports were published in Kernphysikalische Forschungsberichte
Kernphysikalische Forschungsberichte
Kernphysikalische Forschungsberichte was an internal publication of the German Uranverein, which was initiated under the Heereswaffenamt in 1939; in 1942, supervision of the Uranverein was turned over to the Reichsforschungsrat under the Reichserziehungsministerium...

(Research Reports in Nuclear Physics), an internal publication of the German Uranverein
German nuclear energy project
The German nuclear energy project, , was an attempted clandestine scientific effort led by Germany to develop and produce the atomic weapons during the events involving the World War II...

. The reports were classified Top Secret, they had very limited distribution, and the authors were not allowed to keep copies. The reports were confiscated under the Allied Operation Alsos
Operation Alsos
Operation Alsos was an effort at the end of World War II by the Allies , branched off from the Manhattan Project, to investigate the German nuclear energy project, seize German nuclear resources, materials and personnel to further American research and to prevent their capture by the Soviets, and...

 and sent to the United States Atomic Energy Commission
United States Atomic Energy Commission
The United States Atomic Energy Commission was an agency of the United States government established after World War II by Congress to foster and control the peace time development of atomic science and technology. President Harry S...

 for evaluation. In 1971, the reports were declassified and returned to Germany. The reports are available at the Karlsruhe Nuclear Research Center and the American Institute of Physics
American Institute of Physics
The American Institute of Physics promotes science, the profession of physics, publishes physics journals, and produces publications for scientific and engineering societies. The AIP is made up of various member societies...

.
  • Klaus Clusius I. Bericht über Trennversuche von Metallionen mit Hilfe des Nernstschen Verteilungssatzes G-18 (1 June 1940)

  • Klaus Clusius and M. Maierhauser II. Bericht G-19 (28 July 1940)

  • Klaus Clusius, Gerhard Dickel, and M. Maierhauser III. Bericht G-20 (13 January 1941)

  • Klaus Clusius, M. Maierhauser, and Gerhard Dickel Bericht über die im Jahre 1940/41 ausgeführten Versuche zur Entwicklung eines Auswaschverfahrens zur Isotopentrennung G-73 (1941)

  • Klaus Clusius, Gerhard Dickel, and Ludwig Waldmann
    Ludwig Waldmann
    Ludwig Waldmann was a German physicist who specialized in transport phenomena in gases. He derived the Waldmann-Snider equation.-Career:...

     Über die Beeinflussung des Wirkungsgrades von Draht-Trennrohren durch Zentrierung und Einbaur von Scheiben G-132 (20 February 1942)

  • Klaus Clusius and M. Maierhauser Über die Weiterentwicklung des Verfahrens zur Isotopentrennung mittels des Nernst’schen Verteilungssatzes G-133 (March 1942)

  • Klaus Clusius and Kurt Starke
    Kurt Starke
    Kurt Starke was a German radiochemist. During World War II, he worked on the German nuclear energy project, also known as the Uranium Club. He independently discovered the transuranic element neptunium. From 1947 to 1959, he taught and did research in Canada and the United States...

     Zur Gewinnung von schwerem Wasser G-134 (24 February 1942)

  • Klaus Clusius and Kurt Starke Zur Theorie der franktionierten Destillation von H2-HD-D2 Gemischen G-189 (29 June 1942)

  • Klaus Clusius Isotopentrennung G-207 (5 May 1943)

  • Kurt Diebner
    Kurt Diebner
    Kurt Diebner was a German nuclear physicist who is well known for directing and administrating the German nuclear energy project, a secretive program aiming to built weapon of mass destruction for the Nazi Germany during the course of World War II...

    , Werner Czulius, W. Herrmann
    Walter Herrmann (physicist)
    Walter Herrmann was a German nuclear physicist who worked on the German nuclear energy project during World War II...

    , Georg Hartwig, F. Berkei and E. Kamin Über die Neutronenvermehrung einer Anordnung aus Uranwürfeln und schwerem Wasser (G III) G-210

Selected literature

  • K. Clusius and C. N. Hinshelwood Homogeneous Catalysis of Gaseous Reactions. Part I. The Decomposition of Isopropyl Ether under the Influence of Halides, Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, Volume 128, No. 807, 75-81 (1930)

  • Klaus Clusius and Gerhard Dickel Neues Verfahren zur Gasentmischung und Isotopentrennung, Die Naturwissenschaften
    Die Naturwissenschaften
    Naturwissenschaften is a monthly peer-reviewed scientific journal published by Springer on behalf of several learned societies.- History :...

    Volume 26, 546 (1938)

  • Klaus Clusius and Gerhard Dickel Zur Trennung der Chlorisotope, Die Naturwissenschaften Volume 27, 148 (1939)

  • Klaus Clusius and Gerhard Dickel Das Trennrohrverfahren bei Flüssigkeiten, Die Naturwissenschaften Volume 27, 148-149 (1939)

  • G. Böhm and K. Clusius, Die Struktur aufsteigender H2-O2-Flammen, Zeitschrift für Naturforschung A Inhaltsverzeichnis Band 3a, Heft 7, 386-391 (1948)

  • K. Clusius and H. Haimerl, Variationen zum chemischen Austauschverfahren, Anreicherung von 34S, Zeitschrift für Naturforschung A Inhaltsverzeichnis Band 3a, Heft 8-11, 611-616 (1948)

  • Klaus Clusius Flüssiger Wasserstoff, Neujahrsblätter der Naturforschenden Gesellschaft in Zürich Number 158 (1956). Institutional citation: Physikalisch-chemisches Institut der Universität Zürich
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