Relative Activity of Radium and Uranium, 61. 



Tbe value obtained by Boltwood* for this ratio (0*45) is 

 somewhat lower than that given above. When the experi- 

 mental conditions are taken into consideration, however, the 

 agreement is as good as might be expected. A determina- 

 tion has also been made by Meyer and Panethf, who com- 

 pared the radiation from a known quantity of radium with 

 the ionization produced by the ^-particles from one gram of 

 uranium. They obtained a value of 0*57 for the ratio. 

 Aside from other objections 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 

 uranvl nitrate was subjected to purely chemical methods of 

 purification, methods which are generally recognized as un- 

 suitable for obtaining a pure uranium product. Very little, if 

 any, weight can therefore be attached to their determination 

 of the value of the ratio. 



Discussion of Results. 



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

 tions 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 approximately 0*57. The 

 value found in this investigation is 0*19, which is lower by 

 nu 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 disintegrate 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 (6) 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 uranium I. to (and including) 

 radium is at some point irregular and is accompanied by the 

 production of a collateral series. This conclusion is sup- 

 ported by the occurrence of actinium and its products in 

 association with radium in uranium minerals, and by the 

 impossibility of tracing the origin of actinium to any point 

 in the series subsequent to radium. 



* Am. Journ. Sci. xxv. p. 269 (1908). 

 t Wien. Ber. cxxi. Abt. Ila (1912). 



