Rays of Radioactive Substances. 323 



separation of the active products from uranium by the 

 methods of Crookes and Becquerel. The results of these 

 investigations will appear shortly, but the authors of this 

 communication are indebted to Mr. Soddy. of the Chemical 

 Department, for his kindness in making the chemical pre- 

 parations of thorium and uranium which are tested in this 

 paper. 



On examination it was found that the Th. X. emitted 

 both deviable and non-deviable rays, and also a radioactive 

 emanation. The deviable radiation is complex, as in the 

 case of the ordinary thoria, and contains a large fraction of 

 easily absorbed deviable rays. If a large number of suc- 

 cessive precipitations are performed the thoria can be almost 

 completely freed from deviable rays, although about 30 per 

 cent, of the non-deviable rays still remain. 



We thus see that non-deviable rays persist in thoria when 

 the product responsible for deviable rays is completely re- 

 moved. 



Very similar actions have been observed for the active 

 products separable from uranium by the methods of Crookes 

 and Becquerel. Crookes* obtained very active residues from 

 uranium by two methods. In one case it was found that if 

 ether was added to uranium nitrate part of the nitrate was 

 soluble in the ether. The part that was insoluble in the 

 ether was far more radioactive than the part which was not. 

 In the other case the nitrate was dissolved in water and an 

 excess of ammonium carbonate added. A small precipitate 

 remaining behind was found intensely active compared with 

 an equal weight of uranium. This active fraction was called 

 by Crookes Ur. X. 



Becquerel t found that as a result of continued precipita- 

 tion of barium sulphate in a mixture of uranium and barium 

 chloride, he could entirely free the uranium from the photo- 

 graphic action, while the barium sulphate carried with it a 

 very active fraction. In course of time the uranium re- 

 covered the original radioactivity, while the barium sulphate 

 became inactive. 



On examination of the Ur. X. of Crookes and the active 

 barium sulphate of Becquerel, it was found that the radiation 

 was composed almost entirely of deviable rays. The con- 

 ductivity due to the deviable rays was more than § of the 

 total, while the conductivity due to the deviable rays of a 

 thin layer of uranium is not more than one per cent, of the 

 total (see § 7). 



* Proc. Roy. Soc, May 1900. 

 t C. R. Dec. 9, 1901. 



