Radio-activity / by E. Rutherford.

  • Ernest Rutherford
Date:
1905
Catalogue details

Licence: Public Domain Mark

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

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    22. Radio-active lead. Scvciul obsorviTs o;irly iiotifcd that the lead separated tVuni j)itchblendo showed strong radio- active pro])ei'ties, but considerable difference of opinion was expressed in regard to the permanence of its activity. Elster and Geitel* found that lead sulphate obtained from pitchblende was very active, but they considered that the activity was probably due to an admixture of radium or polonium with the lead, and, by suitable chemical treatment, the lead sulphate was obtained in an inactive state. Gieself also separated some radio-active lead but found that its activity diminished with the time. On the other hand, Hofmann and Strauss;]: obtained lead from pitchblende whose activity seemed fairly permanent. They state that the radio- active lead resembled ordinary lead in most of its reactions, but showed differences in the behaviour of the sulphide and sulphate. The sulphate was found to be strongly phosphorescent. These results of Hofmann and Strauss were subjected at the time of their publication to considerable criticism, and there is no doubt that the lead itself is not radio-active but contains a small quantity of radio-active matter which is separated with it. In later work§, it has been shown that radio-lead contains several radio-active con- stituents which can be removed temporarily from it by suitable chemical methods. There can be no doubt that the lead separated from pitchblende by certain methods does show considerable activity and that this activity is fairly permanent. The radio-active changes occurring in radio-lead are complicated and cannot be discussed with advantage at this stage, but will be considered in detail in chapter XL It will there be shown that the primary constituent present in lead is a slow transformation product of radium. This substance then slowly changes into the active constituent present in polonium, which gives out only easily absorbed rays. This polonium can be separated temporarily from the lead by suitable chemical methods, but the radio-lead still continues to produce polonium, so that a fresh supply may be obtained * Elster and Geitel, An7ial. d. Phys. 69, p. 83, 1899. t Giesel, Ber. d. D. Cliem. Ges. p. 3775, 1901. + Hofmann and Strauss, Ber. d. D. Chem. Ges. p. 3035, 1901. § Hofmann, Gonder and Wolfl, Annul, d. Phys. No. 13, p. 615, 1904.