Abstract
WITH ions from a spark between a thorium or uranium electrode and a tin electrode, it was found that easily resolved doublets are given by the mass-spectrograph, formed by the doubly charged thorium ions with the tin isotope at 116 in one case, and in the case of uranium with the isotope at 119 (Fig. 1). The mass difference is found to be 0·120 ± 0·003 for thorium (the average of six doublets of nearly equal intensity), and 0·131 d= 0·003 in the case of uranium (average of the values for the five best doublets). The packing fraction for the tin isotopes has been determined by Dr. Aston1 as 7·3 ± 1. Using this value, the atomic mass of thorium (oxygen = 16·000) is 232·070 and that of uranium 238·088.
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References
F. W. Aston, Proc. Roy. Soc., A, 115, 506 (1927).
A. J. Dempster, NATURE, 136, 180 (1935).
O. Hahn, L. Meitner, F. Strassmann, Ber. deut. chem. Gesell, 69, 913 (1936).
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DEMPSTER, A. Atomic Masses of Uranium and Thorium. Nature 138, 120 (1936). https://doi.org/10.1038/138120a0
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DOI: https://doi.org/10.1038/138120a0
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