Georg von Hevesy developed radioactive tracer analysis, a method widely used in chemistry and medicine. For this accomplishment, which had far-reaching consequences in physiology, biochemistry, and mineralogy, he was awarded the Nobel Prize in chemistry in 1943. Hevesy was also the co-discoverer of the element hafnium.
Georg Charles von Hevesy was born in Budapest, Hungary, on August 1, 1885, to Louis Bisicz and his wife, the former Baroness Eugenie Schosberger. The family, who was given a title by Emperor Franz Joseph I in 1895, first changed their name to Hevesy-Bisicz and then simplified it to Hevesy; Hevesy always used the "von" in German correspondence and publications. (Many sources refer to him as "de Hevesy," while his first name often appears as "George" or "György.") Both sides of the family were well-to-do; facing no financial obstacles, Hevesy moved smoothly through the Piarist Gymnasium in Budapest, then studied physics and chemistry at the University of Budapest, and finally earned his doctorate at the University of Freiburg in 1908 with a thesis on the chemical behavior of sodium hydroxide in fused sodium metal.
Hevesy received his degree and became an assistant at the Eidgenössische Technische Hochschule in Zürich, commencing a career in which he knew or worked with nearly every major scientist of the first half of the twentieth century. He was acquainted with Albert Einstein, for example, in Zürich, where he continued his work with fused salts. After two years he moved on to work with Fritz Haber at the Technische Hochschule in Karlsruhe, but he realized that he lacked the research techniques for the electron-emission studies that Haber had set for him. Hevesy suggested that he join Ernest Rutherford' s group at the University of Manchester in England, and Haber agreed. He received an honorary research fellowship and left in 1911.
Develops Radioactive Tracer Analysis
At Manchester Hevesy worked with, among others, Neils Bohr, Frederick Soddy, Henry Moseley, and Hans Geiger. His first project was the chemistry of the radioactive decay products of actinium, and the effort yielded the finding that successive alpha decay products differ in chemical valence in steps of two. This provided support for the proposal Soddy had recently put forward concerning the existence of alpha-decay--the ejection of an alpha particle, or helium nucleus, from the radioactive nucleus. It was here, however, that Hevesy began the research which was to occupy him for the rest of his life, and it was Rutherford who set him on the road to it. The Austrian government had given Rutherford a hundred kilos of radioactive lead whose activity was known to be that of "radium-D," a decay product of radium. Hevesy was assigned the task of separating the radium-D from "all that lead." Over many months, he tried every chemical separation he knew, with a uniform lack of success. We now know that radium-D is the radioactive isotope lead-210; it is, in other words, a form of lead with the same number of protons and electrons, and hence the same chemistry, as any other lead, but with a different number of neutrons in its nucleus. Separation of isotopes can be done only by painstaking physical methods, and chemical separation is impossible.
Having failed in the separation study, Hevesy then acted on the principle of the popular saying, "If life hands you lemons, make lemonade." Since he could not separate it, he decided to use radium-D to trace the course of lead in chemical processes. Working with Friedrich Paneth at the Vienna Institute of Radium Research in 1913, he was able to conduct precise solubility studies of lead salts by mixing an insignificant mass of radium-D with a regular lead salt, then determining the amount dissolved not by the usual tedious gravimetric methods, but by simple measurement of the proportion of radioactivity found in solution. He was also able to demonstrate lead exchange between solid and solution, and the migration of lead atoms in the metal. He and Paneth showed that the electrochemical properties of radium-D were identical with those of lead, thereby adding to the growing evidence of the existence of isotopes.
In 1913 Hevesy returned to Hungary, where he served for a time as a lecturer at the University of Budapest before joining the Austro-Hungarian army during World War I. His post during the war was as technical supervisor at the state electrochemical copper plant, and he was able to continue his research on a limited basis. After the war he became a full professor at Budapest, continuing his lead tracer work, but the political situation in Hungary was disintegrating rapidly, and in 1920 he accepted an invitation to join Bohr's Institute for Theoretical Physics at the University of Copenhagen.
Participates in the Discovery of Hafnium
His first project there, carried out with Johannes Bro, was an attempt at isotopic separation by fractional distillation. They had limited success with metallic mercury, but obtained fairly pure isotopic samples of chlorine, whose two stable isotopes differ by about six percent in mass. Hevesy wished to learn X-ray spectroscopy, and in 1923 he turned for help to physicist Dirk Coster. The two of them set about finding element seventy-two, which Bohr's recent revision of the periodic table suggested should be a transition metal corresponding to zirconium. They found the anticipated spectral lines in extracts of zirconium ores, and were able to isolate and characterize the new element as its fluoride. They named it "hafnium" after the Latin name for Copenhagen.
In 1923 Hevesy also returned to his work with radioactive lead tracers, and for the first time he ventured into biology to study the uptake of lead in bean seedlings. This work was published in 1924, the year in which Hevesy married Pia Riis, who would bear him three daughters and a son. Two years later, he moved his new family to the University of Freiburg, where he developed X-ray fluorescence as an analytical tool, while expanding the university's X-ray spectroscopy program. As an administrator, however, Hevesy came into increasing contact with the new Nazi regime, and this caused him to return to Copenhagen in 1934.
Heavy water (water in which some of the hydrogen atoms are the heavier isotope hydrogen-2, or deuterium) had just become available, and in Copenhagen Hevesy was pleased to have this first non-toxic isotope available to study animal and human physiology. He and his colleagues quickly demonstrated the rapid exchange of internal and external water in goldfish, and measured the average turnover time of a water molecule in the human body (about thirteen days) and the approximate number of water molecules in the body (1027).
In 1934, Irène and Frédéric Joliot-Curie succeeded in producing artificial radioisotopes by alpha particle bombardment. Hevesy seized the possibilities of this development by making radioactive phosphorus-32 from sulfur-32, a very large advance for the study of physiology. Here was an element central to all animal physiology, and a means of following its intake, circulation, exchange, and excretion. A number of discoveries followed from the use of this tracer, including the dynamic exchange of serum and bone phosphate and the synthesis and distribution of DNA and RNA. Today, these discoveries form the foundation of our understanding of body chemistry.
Phosphorus was only the first element that Hevesy used or introduced into use as a radioactive tracer. Others included calcium-45, potassium-42, sodium-24, chlorine-38, and carbon-14. There is little of physiological importance that lies outside this list except nitrogen, oxygen, and sulfur, and it is clear just how fundamental his contributions to science have been. It was in recognition of these accomplishments that Hevesy was awarded the Nobel Prize in chemistry in 1943. Announced in 1944 and overshadowed by the closing battles of World War II, the award received little public notice.
At the time he received the Nobel Prize, Hevesy had moved again. He had left Copenhagen in 1943, moving away from the Nazis for a second time, and settled in Stockholm. He worked at the Institute for Organic Chemistry there for the remainder of his life, becoming a Swedish citizen in 1945. Much of his later research focused on physiology and medicine, particularly the study of cancer. He published over four hundred books and papers in the course of his career and received many awards and honors, including honorary doctorates from nearly a dozen universities and honorary memberships in many scientific societies. He was also a foreign member of the Royal Society. In addition to the Nobel Prize, he received the Cannizzaro Prize in 1929 from the Academy of Sciences in Rome, the Copley Medal of the Royal Society in 1950, and the Faraday Medal in 1959. He also received the Atoms for Peace Award in 1959. Hevesy died at a clinic in Freiburg on July 5, 1966, after a long illness.
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