of Radium J torn Uranium. 773 



Natural leak of electroscope 1*56 divisions per minute. ^ Leak 

 after the introduction of the air from the uranium solution: — 



Corrected rates of leak 

 (divisions per minute). 



to 10 divisions in 42 seconds 12 - 74 



15 to 25 „ 353 , 15-44 



30 to 40 „ 35-8 15-20 



45 to 55 ., 37 „ 1465 



Electroscope recharged. 



to 10 divisions in 384 seconds 14*06 



15 to 25 „ 360 „ 151 



30 to 40 „ 370 „ 14-6 



Microscope reset. 



to 20 divisions in 63 2 seconds 174 



25 to 35 „ 28-4 „ 19-5 



Microscope reset. 



to 10 divisions in 32 seconds 17*2 



The air in the electroscope was then sucked out : 



1 minute afterwards to 5 divisions in 30 secs.l 8*4 



4 minutes afterwards to 5 ,, 57*3 „ 3*7 



6 „ 0to5 ,, 91 „ 1-8 



18 ,, ,, 37 divisions in 13 minutes 13 



10 „ „ |ll „ 5 „ | 06 



Similar results were always obtained when the emanation 

 from the uranium was tested, and also when minute quantities 

 of the radium emanation itself were introduced into the 

 electroscope for the purpose of calibration. 



A further test of the identity of the emanation from the 

 uranium with that from radium was obtained by taking four 

 series of observations in which the period of accumulation of 

 the emanation from the uranium was varied. For the case 

 of radium the quantity of emanation accumulating attains a 

 practical maximum after three or four weeks, and generally 

 if I represents the rate of leak due to this maximum, and 

 It that due to the quantity of emanation accumulating in t 

 seconds T 



ii=l_ e -« 



where \ = 2.10~ 6 . The following results were obtained: — 



Date. 



Time of 

 accumulation. 



Rate of Leak. 



Natural Leak. 



Corrected 

 Rate of Leak. 



Dec. 17, 1904 



Dec. 21, 1904 



Jan. 7, 1905 



Jan. 9, 19<»5 



9 months 



4 days 

 17< ; 

 53*5 hours 



16-7 



120 



180 



95 



1-56 



1-8 

 235 



2-8 



151 

 102 

 16-65 



6-7 



