Ions, electrons, and ionizing radiations / by James Arnold Crowther.
- James Arnold Crowther
- Date:
- 1919
Licence: Public Domain Mark
Credit: Ions, electrons, and ionizing radiations / by James Arnold Crowther. Source: Wellcome Collection.
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![in the electroscope. By making experiments over the lake he found that the number of ions formed per second per cubic centimetre of gas was reduced to 4:8 when the electroscope was of aluminium and 6-3 when it was of brass. The difference in the two values suggests that the small residual effect is due to the metal of the electroscope. The effect is however so minute that it is difficult to decide with certainty. A single a-particle from radium produces more than 10° ions during its path of 3 cms. The passage of a single a-particle through each cubic centimetre of the gas, once every three hours, would therefore be sufficient to produce the average ionization found under these circumstances. The quantity of radio-active impurity in the metal necessary to produce an emission of this order is so minute that it is difficult to prove conclusively that the effect is not due to this cause, and Ruther- ford after a careful survey of the results has come to the con- clusion that ordinary matter is not radio-active. On the other hand experimenters who have actually worked on the subject generally incline to the view that there is a residual effect due to the actual] radio-activity of the elements themselves. The survey of the subject has, however, led to the discovery of one more radio-active substance, namely potassium, which is found to emit f-radiation of very much the same type as that from uranium. The activity of a surface of potassium salt is quite appreciable, being in general about one per cent. of that of a surface of a salt of uranium. Rubidium has also been found to possess a similar radio-activity. In neither case is anything yet known as to the nature of the product, or the period of the change.](https://iiif.wellcomecollection.org/image/b32782032_0272.jp2/full/800%2C/0/default.jpg)
