Sigma Xi Colloquium Series

Thursday, January 27, 2000

10:30 –11:30 am

Green Auditorium

The Disputed Discovery of Element 43 (Technetium)

John T.Armstrong, Surface and Microanalysis Division, NIST, and

P.H.M. Van Assche, Physics Dept., KULeuven, Belgium.

In 1925, Noddack, Tacke and Berg reported discovery of element Z=43, which they named Masurium, based on line identification of x-ray emission spectra from chemically concentrated residues of various U-rich minerals. Their results were disputed and eventually the discovery of element 43 (Technetium) was generally credited to Perrier and Segre, based on their chemical separation of neutron-irradiated molybdenum in 1937. Using first principles x-ray emission spectral generation algorithms from the N.I.S.T. DTSA spectral processing program, we have simulated the x-ray spectra that would be expected using their likely analytical conditions (from their papers and contemporaneous reports) and the likely residue compositions suggested by Noddack et al. and Van Assche. The resulting spectra are in close agreement with that reported by Noddack et al., place limits on the possible residue compositions, and are supportive of the presence of detectable amounts of element 43 in their sample. Moreover, the calculated mass of element 43 shown in their spectrum is consistent with the amount that would be now expected from the spontaneous fission of U present in the ores they studied. The history of the original masurium/technetium controversy and the means used to reexamine the original record will be presented in this scientific detective story.

   

Further information, contact Bob Fletcher, 301-975-3912.