Tin Isotopes

F. W. Aston. The Isotopes of Tin.
Nature, 109, p. 813, 1922 (June, 24).

Aston succeeded in carrying out an analysis of tin by means of a mass spectrograph. Until now this analysis had been hindered by the low sensitivity of the photographic plate to canal rays. To increase the sensitivity it was necessary to increase the concentration of coarse silver bromide in the surface layer. This

was achieved by dissolving part of the gelatin with acid. Plates treated in this way proved to be 10–20 times more sensitive, while their other properties remained unchanged.

Tin tetrachloride served for the investigation of tin, and eight lines were found, corresponding to the following atomic weights (approximately): 116 (c), 117 (f), 118 (b), 119 (e), 120 (a), 121 (h), 122 (g), 124 (d). The assignment of these lines to tin was satisfactorily confirmed by the presence of analogous groups corresponding to $\mathrm{Sn}(\mathrm{CH}_3)$, $\mathrm{Sn}(\mathrm{CH}_3)_2$, and $\mathrm{Sn}(\mathrm{CH}_3)_3$. The distribution of the intensities of the lines, indicated by the letters in parentheses, agreed well with the accepted atomic weight of tin, 118.7.

As for the atomic weights of the isotopes, the differences between them proved to be exactly integral, whereas the atomic weights themselves in all cases were 2 or 3 per mille less than the integers written above.

In the same note Aston reports that the presence of two weak components of xenon, 128 and 130, which had previously only been suspected, has now been satisfactorily proved.

*) Shpolsky.