Patent of the month March


Preparation of Radiothorium – The only patent of Lise Meitner

On the occasion of International Women's Day on March 8, we celebrate the Austrian science pioneer Lise Meitner. The outstanding nuclear physicist became Germany's first female professor of physics and was significantly involved in the discovery of nuclear fission.

While Otto Hahn, with whom she had a long-standing scientific collaboration, received the Nobel Prize for Chemistry for it, Lise Meitner's scientific achievements have not been given adequate recognition until now. As a thoroughbred scientist, she applied only once for a patent for one of her research results in 1913. The US-application US1076141A with the title "Preparation of Radiothorium" is therefore our Patent of the month March!

The disclosure briefly describes the preparation of radiothorium, the thorium isotope 228 (228Th). The isotope can be extracted by precipitating at the cathode by electrolysis. From the very beginning, Lise Meitner was interested in radioactivity when she started her studies at the University of Vienna in 1901. In 1906, she received her PhD in theoretical physics and went to Berlin one year later for further scientific studies, especially to listen to Max Planck's lectures.

Until her emigration in 1938, the born Jewish woman conducted research in Berlin. First unofficially together with Otto Hahn as an "unpaid guest" in Planck's laboratory. After the establishment of women's studies in Prussia in 1909, she no longer had to slip in the institute through the back entrance, but still worked unpaid. It wasn't until 1918 that Lise Meitner received an adequate salary as head of the radiophysical department of the newly founded Kaiser Wilhelm Institute for Chemistry. Together with Hahn, she discovered various radioactive nuclides and gained international recognition. In her Swedish exile, she continued the meanwhile 30-year-long collaboration with Otto Hahn and his assistant Fritz Straßmann via scientific correspondence.

In 1939, she succeeded, together with her nephew, the nuclear physicist Otto Frisch, in providing the first physical-theoretical explanation, including concrete calculations, of an experiment by Hahn and Straßmann. The latter had triggered a "bursting" of the uranium atomic nucleus in an experiment due to irradiation with neutrons and had proven this with radiochemical methods. But the two chemists were only able to interpret their observations in a rudimentary way. Meitner and Frisch provided the correct explanation and coined the term "nuclear fission", which soon became internationally established.

The discovery of nuclear fission became one of the most momentous events in the history of science, as it opened up a new source of energy of previously unknown magnitude. Research into nuclear energy for both peaceful and military purposes mobilized scientists worldwide. A convinced pacifist, Lise Meitner condemned the development of the atomic bomb and propagated the peaceful use of nuclear energy throughout her life.

Otto Hahn was awarded the Nobel Prize for his discovery in 1945. Meitner and Frisch missed out, although the decisive approach in nuclear physics came from them. All in all, Lise Meitner was nominated 48 times for the Nobel Prize (in physics as well as chemistry), and never received it! Whether she had been deliberately left out by Hahn and other colleagues, who rarely emphasized her share, is the subject of a controversial discussion sparked by chemist and feminist Ruth Lewin Sime in 1996.

However, the renowned researcher received many honours for her life's work. In recent years, she has returned to the public eye in as streets and schools have been named after her, as well as prizes, elements and asteroids.

The Patent & Standards Centre would like to wish all female inventors and scientists good luck for the future!

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Ruth Lewin Sime: Lise Meitner. Ein Leben für die Physik

Insel Verlag, Frankfurt am Main 2001
ISBN 9783458170662