744 



Prof. E. Kutherford on the 



I. 



ii. 



III. 



IV. 



V. 



Time of 



Time oi' 



Observed movement 



q in divs. 



qt in divs. 



prep i ration. 

 4 days 



collection. 



of el'ectr scope. 



per mm. 



per nun. 



4 days 



"05 div. per min. 



•26 



•15 



8 „ 



4 „ 



•120 



•23 



•26 



12 „ 



4 „ 



'194 



•24 



•41 



16 „ 



4 „ 



•265 



•24 



"55 



22 



6 ,, 



443 ,; 



•23 



•72 



33 „ 



11 „ 



•965 



•27 



1 27 



40 ,; 



7 ,, 



106 



■275 



1-57 



; oo „ 



10 „ 



1-44 



•255 



1-82 



! «o „ 



80 „ 



1S5 



•27 



232 



: iu •• 



51 „ 



3 93 „ 



•259 



4-11 



The amount of radium at different times is shown graphi- 

 cally in fig. 1 (curve actinium II. j, drawn on the same scale 

 as the curve for actinium II. It will be seen from column IV. 

 that the rate of production of radium per week, within the 

 limits of experimental error, is constant over the whole 

 interval of 111 days. If radium had been produced directly 

 from actininm B, the rate of growth observed at an interval 

 of 8 days should have been about '11 or less than half that 

 actually observed. We may thus conclude that (1) radium 

 is not produced directly from actinium B, and (2) that if 

 radium is produced directly from actinium, a product of slow 

 transformation must exist between actinium B and radium. 



On account of my departure from Montreal, the experiments 

 were stopped after 111 days. The electroscope was removed 

 and set up in Manchester and the solution tested at intervals. 

 The results indicate that the rate of growth is still the same 

 after a period of 246 days. 



§ 3. Experiments with Actinium III. 

 The variation of the a ray activity of a thin film of the 

 solution actinium II. is shown in fig. 2 on the same scale as 

 that of actinium I. It will be seen that the variation of the 

 activity is very similar to that observed for actinium I., and 

 is to be explained in a similar manner. As in the first case, 

 only a part of the actinium was precipitated by the addition 

 of ammonium sulphide. The residue of the actinium remained 

 in the filtrates. After suitable treatment of the latter, 

 ammonia was added in order to precipitate the remaining 

 actinium. A very small precipitate was obtained which was 

 not more than one hundredth of the weight of that initially 



