Ida Noddack - Element Discovery Priority

Element Discovery Priority

Noddack and her husband looked for the then still unknown elements 43 and 75 at the Physikalisch-Technische Reichsanstalt. In 1925, they published a paper (Zwei neue Elemente der Mangangruppe, Chemischer Teil) claiming to have done so, and called the new elements Rhenium and Masurium. Only the discovery of rhenium was confirmed. They were unable to isolate element 43 and their results were not reproducible. Their choice of the term masurium was also considered unacceptably nationalistic and may have contributed to a poor reputation amongst scientists of the day.

Artificially produced element 43 was definitively isolated in 1937 by Emilio Segrè and Carlo Perrier from a discarded piece of molybdenum foil from a cyclotron which had undergone beta decay. It was eventually named technetium due to its artificial source. No isotope of technetium has a half-life longer than 4.2 million years and was presumed to have disappeared on earth in as a naturally occurring element. In 1961 minute amounts of technetium in pitchblende produced from spontaneous 238U fission were discovered by B. T. Kenna and P. K. Kuroda. Based on this discovery, Belgian physicist Pieter van Assche constructed an analysis of their data to show that the detection limit of Noddacks' analytical method could have been 1000 times lower than the 10−9 value reported in their paper, in order to show the Noddacks could have been the first to find measurable amounts of element 43, as the ores they had analyzed contained uranium. Using Van Assche's estimates of the Noddacks' residue compositions, NIST scientist John T. Armstrong, simulated the original X-ray spectrum with a computer, and claimed that the results were "surprisingly close to their published spectrum!" Gunter Herrmann from the University of Mainz examined van Assche's arguments, and concluded they were developed ad hoc, and forced to a predetermined result. According to Kenna and Kuroda 99technetium content expected in a typical pitchblende (50% uranium) is about 10 −10 g/kg of ore. F. Habashi pointed out that uranium was never more than about 5% in Noddacks' columbite samples, and the amount of element 43 could not exceed 3 × 10 −11 µg/kg of ore. Such a low quantity could not be weighed, nor give X-ray lines of element 43 clearly distinguishable from the background noise. The only way to detect its presence is to carry out radioactive measurements, a technique the Noddacks did not use, but Segrè and Perrier did.

Following on the van Assche and Armstrong claims, an investigation was made into the works of Masataka Ogawa who had made a prior claim to the Noddacks. In 1908 he claimed to have isolated element 43, calling it Nipponium. Using an original plate (not a simulation), Kenji Yoshihara determined Ogawa had not found the Period 5 Group 7 element 43 (eka-manganese), but had successfully separated Period 6 Group 7 element 75 (dvi-manganese) (rhenium), preceding the Noddacks by 17 years.