The atomic weight of xenon

Abstract

The values of 130.2 and 82.9 for the atomic weights of xenon and krypton respectively in the International Table of Atomic Weights are based on the determinations made by Moore of the densities of the two gases and on the calculations of Watson of their deviations from the gas laws.J The accuracy of these values was first called in question by Aston in 1922, who examined the gases in his early mass spectrograph and deduced from the relative intensities of the lines of the isotopes the figures 131.3 and 83.5. More recently, using the improved mass spectrograph and a more accurate method of computing intensities he has obtained the values 131.27 ± 0.04 and 83.77 ± 0.02, and since his measurements for other elements, notably mercury, zinc, molybdenum, chromium and tin, give values which accord very closely with the best chemical determinations, it appeared likely that the accepted atomic weights both of xenon and krypton were in error.