of Radium and Uranium. 13 



The value obtained by Boltwood 17 for this ratio (045) 

 is somewhat lower than that given above. When the 

 experimental conditions are taken into consideration, 

 however, the agreement is as good as might be expected. 

 A determination has also been made by Meyer and 

 Paneth 18 who compared the radiation from a known 

 quantity of radium with the ionization produced by the 

 a-particles from one gram of uranium. They obtained 

 a value of 0-57 for the ratio. Aside from other objec- 

 tions to their method, the manner in which they obtained 

 the uranium salt used as a standard is open to the most 

 serious criticism. Comparatively crude uranyl nitrate 

 was subjected to purely chemical methods of purification, 

 methods which are generally recognized as unsuitable 

 for obtaining a pure uranium product. Very little, if 

 any, weight can therefore be attached to their determi- 

 nation of the value of the ratio. 



Discussion of Results. 



As already pointed out, if the entire series of trans- 

 formations from uranium I, through uranium II and 

 ionium, to radium is a simple and direct one, the value 

 to be expected for the uranium-radium ratio is approxi- 

 mately 0-57. The value found in this investigation is 

 049, which is lower by an amount far in excess of the 

 probable experimental error. The result suggests that 

 the number of radium atoms which disintegrate with the 

 emission of a-particles in the unit time is less than the 

 number of atoms of uranium I or uranium II which dis- 

 integrate in the same period. This indicates either (a) 

 that a series of branch products is split off from the 

 main series before the radium atom is produced, or (b) 

 that radium itself disintegrates in a complex manner, a 

 larger proportion (but not all) of the atoms being trans- 

 formed with the emission of a-particles. Unless the 

 accepted values for the ranges of the a-particles from 

 uranium are greatly in error (which appears to be rather 

 improbable) the progress of transformation from ura- 

 nium I to (and including) radium is at some point 

 irregular and is accompanied by the production of a col- 

 lateral series. This conclusion is supported by the 

 occurrence of actinium and its products in association 



17 This Journal, 25, 269, 1908. 

 ^Wien. Ber., 121, Abt. Ha, 19l2. 



