Rays of positive electricity and their application to chemical analyses / [Sir J.J. Thomson].

  • Thomson, J. J. (Joseph John), 1856-1940.
Date:
1921
Catalogue details

Licence: In copyright

Credit: Rays of positive electricity and their application to chemical analyses / [Sir J.J. Thomson]. Source: Wellcome Collection.

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    will be prepared to accept it unless every other explanation has been shown to be untenable. It would strengthen greatly the proof if we could detect the parts of the atom which remain after the helium had been given off. I have made efforts to do this, but have not obtained decisive results. The difficulties are very considerable. Consider, for example, the case of lithium : if we took the helium away we should get a substance with atomic weight 3 ; we do find this sub- stance when we bombard lithium salts, but we also find it when we bombard salts which do not contain any lithium. Then take sodium : the residue after the liberation of helium would have the atomic weight 23 — 4 = 19. This is the atomic weight of fluorine, a substance with such energetic chemical properties that it would enter into chemical com- bination and so escape detection. Beryllium would seem to be the most promising, for the atomic weight of the residue would be 9 — 4 = 5, and this would give rise to a new line which could not be confused with any other. Unfortunately, though a great deal of helium is given off by minerals like the beryls which contain beryllium, the beryllium salts which I have tried give out exceptionally small quantities of helium. ON THE NATURE OF X3, THE SUBSTANCE GIVING THE “3” LINE When salts and minerals are bombarded we find when we analyse by the positive rays the gases given off, a line corresponding to a substance with atomic weight 3 as well as the helium line. In fact the “3” line occurs even more frequently in such cases than the helium line, for it is rare to find it absent after any solid has been bombarded by cathode rays, and it not infrequently occurs when no trace of the helium line can be detected.