252 Mr. H. Richardson : Analysis of the 



this by experiment from the third effect to be 1*54 10~ 5 

 Hence 



T-3 .10- 12 , 



which is in good agreement with the value T = 2 . 10" 

 found from the first effect. 



XXVII. Analysis of the 7 Rays from the Uranium Products. 

 By H. Richardson, M.Sc, Beyer Fellow, University of 

 Manchester ~\. 



IX previous papers % it has been shown that the 7 rays 

 emitted by the radium, thorium, and actinium products 

 can be analysed into groups of different penetrating powers. 

 All the radioactive substances which emit /3 rays have been 

 examined except the uranium products, viz. uranium X] and 

 uranium X 2 . In order to complete the series the analysis 

 of the 7 rays from these substances has been undertaken, 

 and confirmatory evidence concerning the atomic weight of 

 actinium has been obtained. 



The uranium X used in the experiments was separated 

 from 3 kilograms of pure uranium nitrate. The method of 

 separation employed was that used by Soddy and Russell § 

 in their early investigations on the penetrating pow T er of the 

 7 rays from uranium X. It consists in the fractional 

 crystallization of the uranium nitrate from a solution of 

 density 2'06. Under these conditions, the uranium nitrate 

 which crystallizes out only carries with it about one-seventh of 

 the total amount of uranium X present, and the remaining 

 six-sevenths may be poured off with the mother liquor. By 

 repeating this process about three-quarters of the uranium 

 X can be obtained in a solution which contains only a few 

 grams of uranium nitrate. The uranium X was finally 

 separated by precipitation with ammonia and ammonium 

 carbonate in the presence of ferric chloride. By this means 

 the uranium X was obtained together with a small amount 

 of ferric hydroxide, and the whole source thus consisted of 



* The value given by Professor Corbino for E is 7*7 . 10~ 5 . This is to 

 be multiplied by 2 on account of an error corrected in the second of his 

 papers referred to ; and it should be divided by 10 since in another place 

 he has used the ampere as the unit of current instead of the absolute unit. 



t Communicated by Prof. E. Rutherford, F.R.S. 



1 Rutherford and Richardson, Phil. Mag. xxv. p. 722 (1913), xxvi. 

 p. 324 (1913). 



§ Soddy and Russell, Phil. Mag. xviii. p. 620 (1909). 



