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

  • Frederick Soddy
Date:
1914
Catalogue details

Licence: In copyright

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

    46/64 page 34
    From an entirely independent field from that of radio- active change, and all the more welcome on that account, evidence has recently been forthcoming upon the ques- tions of the homogeneity of chemical elements and the spectroscopic identity of isotopes. Sir Joseph Thomson has recently perfected an entirely new method for the determina- tion of the masses of the positive ions in an ultra-rarefied gas under the action of the electric discharge—for the masses, that is, of the material particle constituting the so-called “ positive-rays ” or “ canalstrahlen.” The method depends on the well-known principle due to the same discoverer of deflecting the trajectory of the ion by the simultaneous application of electric and magnetic fields. Both magnetic and electric forces act, in this case, in the same plane at right angles to the direction of the ion, and produce simul- taneous deflections in two planes at right angles to this direction. In this way all the particles having the same ratio, ejm, of the charge to the mass, fall upon a photo- graphic plate, placed at right angles to the initial direction of the ion, on a parabola, and from the number of parabolas the number of different kinds of ion in the gas may be at once found. From the parabola corresponding to the uni- valent hydrogen ion, which is found upon all plates, the value for ejm of the other ions may be deduced. From certain peculiarities in the photographic traces, for which the original paper may be consulted, singly charged ions may be distin- guished from multiply charged ions, and thus the value of m found. Several ions were so recognised, corresponding with no previously known particle. Some of these, notably “ Xg,” which is now regarded as Hg, the hydrogen analogue of ozone, are probably new molecular species, highly interest- ing in themselves, but not directly connected with the present subject.
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