The chemistry of the radio-elements / by Frederick Soddy.

  • Soddy, Frederick, 1877-1956.
Date:
1914
Catalogue details

Licence: In copyright

Credit: The chemistry of the radio-elements / by Frederick Soddy. Source: Wellcome Collection.

    42/64 (page 30)
    THE ORIGIN OF ACTINIUM Although the long outstanding problem of the origin of actinium has not yet been cleared up, the number of possibilities to be considered is now greatly reduced, and it is to be expected that the answer to this question will soon be forthcoming. There is little doubt that actinium is a relatively short-lived radio-element, and that its period cannot be greater than a century at most, Mme. Curie, from direct observation, estimated the period provisionally as only thirty years (I, p. 83). From the fact also that intensely active preparations of it have been prepared, it scarcely can be a primary element, and the first question to be considered is its parent. On this point the rules give an alternative (Fig. ii). Either it must be formed from radium, or one of its isotopes in group II. A, in a ;8-ray change, or. from Eka-tantalum,” group V. A, in an a-ray change. At first, before the discovery of uranium X^, the writer suggested that the unknown product of uranium X, in group V. A, might disintegrate dually, like the C members in group V. B, giving uranium II in a /3-ray, and actinium in an a-ray change.^ This could only have remained un- known if the period of this unknown member were very long. In this case “ Eka-tantalum ” would constitute a new radio-element, obtainable from minerals in quantities suffi- cient for chemical examination. The discovery of uranium Xg in this place, and its short life and absence of a-radiation, disproved this view. An experimental examination of a preparation of radium bromide, containing 13.2 milligrams of radium (element), which was ten years old, and had not been subjected to any interference during that time, disproved in turn the second alternative.^’^ No trace of actinium was found to be present in the preparation, although radio-thorium in distinct amount was obtained. The origin of this radio-thorium, presumably, is the minute amount of thorium which is known to be