The Origin of Radium


IN an earlier communication to NATURE (September 26, p. 544) I mentioned some experimental proof which had been obtained of the existence in uranium minerals of a new radio-active element differing from those which have previously been identified. More conclusive evidence of the individuality of this new substance has now been obtained through the examination of the properties of its radiation. The rays which it a emits are much more readily absorbed by aluminium than the a rays from polonium, with which it has been directly compared. Their apparent range in air determined by the scintillation method is less than 3 centimetres, arid a more accurate determination is somewhat difficult, since it has not yet been found possible to obtain the new substance entirely free from thorium. Certain operations are now being carried out with considerable quantities of a uranium mineral containing no thorium which it is hoped will result in the separation of a highly active preparation of the new body free from other radio-active substances. The short range of the particles is, however, sufficiently characteristic to serve as a definite means of identification.

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