Radio-activity / by E. Rutherford.

  • Ernest Rutherford
Date:
1904
Catalogue details

Licence: Public Domain Mark

Credit: Radio-activity / by E. Rutherford. Source: Wellcome Collection.

    37/426 page 21
    The activity of these substances, when removed from the active element, is however only transient, and decays gradually with the time. This activity is not due to the presence of the radio-element itself. For example, barium separated from radium is strongly active, although the spectroscopic examination shows no trace of the radium lines. In order to explain this temporary activity in inactive matter it has been supposed that the non-active matter is made active by ‘'induction” during its mixture with the active material. The underlying idea has been that inactive bodies themselves acquire the property of radio-activity. There is no evidence however that such is the case. The evidence rather points to the conclusion that the activity is due, not to any alteration of the inactive body itself, but to an admixture with it of a very small quantity of intensely active matter. The active matter that causes this so- called “induced” activity is itself a product of the disintegration of the radio-element and differs from it in chemical properties. The subject is a complicated one, and it cannot be discussed with advantage at this stage; it will, however, be considered in detail in section 187. On the above view the active bismuth contains a small quantity of matter, which weight for weight is probably far more active than radium, but the activity of which decays with time. The active matter is allied in chemical properties to bismuth, but possesses some distinct analytical properties which allow of a partial separation. The absence of any new lines in the spectrum is to be expected if, even in the most active bismuth prepared, the active matter exists in very small quantity. 19. The discussion of the nature of polonium was renewed by the discovery of Marckwald1 that a substance similar to polonium, of which the activity did not decay with time, could be separated from pitchblende. The method of separation from the bismuth chloride solution obtained from uranium residues was very simple. A rod of bismuth, dipped in the active solution, rapidly became coated with a black deposit, which was intensely active. This deposit was continued until the whole of the activity was removed from the solution. From 850 grammes of bismuth solution, 1 Ber. deutscli. chem. Ges., p. 2285, 1902 ; Phys. Zeit,, No. 1 b, p. 51, 1902.
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