July 28 marks the passing of Otto Hahn. Hahn was a German chemist credited with the discovery of nuclear fission.
Hahn wanted to be an industrial chemist. In order to improve his English language skills, he obtained a position in William Ramsay‘s laboratory. Ramsay taught him how to be a good experimentalist and introduced him to the relatively new field of radioactive elements. Hahn was working with samples of radium when he discovered what he thought was a new element, radiothorium. It would be known later that radiothorium was an isotope of thorium, thorium-228, and not a new element. He continued his studies in Canada under Ernest Rutherford and isolated three other new elements that turned out to be isotopes of known elements: thorium C (polonium-212), radium D (lead-210) and radioactinium (thorium-227).
When he returned to Germany, he began to work with Emil Fischer. He would discover three more element/isotopes: mesothorium I (radium-228), mesothorium II (actinium-228) and ionium (thorium-230). During World War I, he was briefly assigned to work with Fritz Haber to develop chemical weapons for Germany’s war effort before returning to radiochemistry and his partnership with Lise Meitner. The two of them would finally isolate their first genuine element which they called proto-actinium. Today, the name is shortened to protactinium.
Hahn and Meitner had a long lasting work relationship. The pair of them would work together until the rise of the Nazi party caused Meitner to flee to Stockholm. Hahn helped her leave and gave her his mother’s diamond ring to use as a bribe if necessary. The two of them would still correspond whenever possible through Hahn’s assistant, Fritz Strassmann. One set of projects they were working on was bombarding uranium with neutrons to try and produce transuranic elements. Strassmann wrote to Meitner that he had been identifying barium among the samples of uranium. Barium is nearly half the atomic weight of uranium and Hahn felt that it was possible the uranium nucleus had ‘burst’ somehow. Meitner and her nephew Otto Frisch calculated it was possible for a uranium nucleus to split or ‘fission’ when hit by a neutron. Hahn would win the 1944 Nobel Prize in Chemistry for the discovery of nuclear fission.
Hahn spent World War II working on fission reactions where he identified 25 elements and 100 different isotopes. While he did not work on any German atomic weapon program, he and nine other German scientists were captured in July of 1945. He was interned at Farm Hall, England where he learned he won the Nobel Prize through an English newspaper.
After the war, Hahn was instrumental in rebuilding German science. He served as the president of the newly formed Max Planck Society. He became a spokesman against the weaponization of atomic fission, nuclear weapons, and other misuses of nuclear energy.
Some consider Hahn to be the father of radiochemistry. His book Applied Radiochemistry was the standard handbook for anyone working in the field in the 1930s-40s.
Other Notable Events of July 28
2004 – Francis Crick died.
Crick was a British molecular biologist who was one of the co-discoverers of the structure of the deoxyribonucleic acid (DNA) molecule with James Watson. This discovery would earn them two-thirds of the 1963 Nobel Prize in Medicine.
2002 – Archer John Porter Martin died.
Martin was a British chemist who shared the 1952 Nobel Prize in Chemistry with Richard Synge for the invention of partition chromatography. He also developed gas-liquid chromatography.
1930 – Allvar Gullstrand died.
Gullstrand was a Swedish ophthalmologist who was awarded the 1911 Nobel Prize in Medicine for his studies into the refractive properties of the eye to focus images.
1925 – Baruch Samuel Blumberg was born.
Blumberg is an American physician who shares the 1976 Nobel Prize in Medicine with D. Carleton Gajdusek for their research into the origins and spread of infectious diseases. Blumberg discovered an antigen that causes an antibody response against hepatitis B. This lead to the development of an effective vaccine to fight hepatitis B.
1915 – Charles Hard Townes was born.
Townes is an American physicist who was awarded half the 1964 Nobel Prize in Physics for the development of the first working maser. A maser is a device that produces coherent microwave radiation and stands for Microwave Amplification by Stimulated Emission of Radiation. The other half of the prize went to Nikolay Basov and Alexandr Prokhorov for the theoretical groundwork behind masers.
1867 – Charles Dillon Perrine was born.
Perrine was an Argentine astronomer who discovered sixth and seventh moons of Jupiter, known as Himalia and Elara today.