Part 2: The tracer technique is developed
George de Hevesy is invited to Copenhagen by Niels Bohr and here he enters a productive period where he continues to build on his good idea about trace elements and discovers the element, which he names after Copenhagen, hafnium.
Invitation to Copenhagen
During World War 1, the Hevesy family lost their immense fortune. George de Hevesy had poor health and after World War I (1914-1918) the gifted young chemist had to find a place to work.
Niels Bohr invited him to Copenhagen, where he worked at the University of Copenhagen’s newly established Institute for Theoretical Physics, which after Niels Bohr’s death was renamed the Niels Bohr Institute.
During the period 1920-1926, when Hevesy worked in Copenhagen, he developed the tracer technique in collaboration with scientists at the leading research institutions in Copenhagen, the University of Copenhagen, the Royal Danish Veterinary and Agricultural University, the Technical University of Denmark (now DTU) and the Radium Station.
The tracers, or the indicator principle, had limited application, because thee only available radioactivity was in the form of Radium-D and Radium-F. These salts of heavy metals are highly toxic and their biological use is therefore limited.
The first studies dealt with the absorption and metabolism of lead in plants, published in 1923 and studies of the circulation of bismuth and lead in animal studies with Radium-F (an isotope of bismuth) and Radium-D (an isotope of lead).
The study with bismuth, which is used as a remedy for the treatment of syphilis, was carried out by Hevesy along with the Danish dermatologist and chief physician Svend Lomholt and the chemist Jens A. Christensen. The physiological and biological studies in the 1920s were limited by the poor availability of radioactive materials.
The discovery of hafnium
Hevesy’s great achievement in the 1920s at Bohr’s institute was in a whole different ball game; namely, the discovery of the missing element in the periodic table, hafnium, which is Latin for ‘Copenhagen’.
Together with Dirk Koster from Holland and Niels Bohr and using the principles of quantum mechanics, they could theoretically calculate methods that could separate hafnium from zirconium.
Niels Bohr was able to report on the one-week old discovery in December 1922 in Stockholm, when he gave his Nobel lecture.
Hevesy and Koster were naturally proud of their discovery of hafnium and many years later, when Hevesy received the Nobel Prize for the tracer principle, it was said that he was not really very happy about the Nobel Prize in 1943/44, because he thought it would have been more sensible for him to have received it for the discovery of the element hafnium.