At the University, he conducted major experiments on heavy water, and he developed a thermodiffusion isotope separation tube, in 1938,[4] with his younger colleague Gerhard Dickel.
[1][3][5] In December 1938, the German chemists Otto Hahn and Fritz Strassmann sent a manuscript to Naturwissenschaften reporting they had detected the element barium after bombarding uranium with neutrons;[6] simultaneously, they communicated these results to Lise Meitner, who had in July of that year fled to The Netherlands and then went to Sweden.
[9] Paul Harteck was director of the physical chemistry department at the University of Hamburg and an advisor to the Heereswaffenamt (HWA, Army Ordnance Office).
On 24 April 1939, along with his teaching assistant Wilhelm Groth, 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 on the use of uranium fission in a Uranmaschine (uranium machine, i.e., nuclear reactor), Georg Joos, along with Hanle, notified Wilhelm Dames, at the Reichserziehungsministerium (REM, Reich Ministry of Education), of potential military applications of nuclear energy.
[10][11][12][13] The second Uranverein began after the HWA squeezed out the RFR of the REM and started the formal German nuclear energy project under military auspices.
The invitees included Walther Bothe, Siegfried Flügge, Hans Geiger, Otto Hahn, Paul Harteck, Gerhard Hoffmann, Josef Mattauch, and Georg Stetter.
A second meeting was held soon thereafter and included Klaus Clusius, Robert Döpel, Werner Heisenberg, and Carl Friedrich von Weizsäcker.
That same year, Clusius, Paul Harteck, Rudolf Fleischmann, Wilhelm Groth and others initiated experiments with the Clusius-Dickel thermodiffusion isotope separation tube with uranium hexafluoride.
Further research was high-precision calorimetry, elucidation of chemical reaction pathways using 15-nitrogen, electrochemical and low temperature fractionation methods for large scale production of nitrogen and oxygen isotopes.