172 Dr. W. S. Lazarus-Barlow. On the Presence of [Feb. 14, 



No. 147 C. Natural leak 



Experimental leak 



No. 440. Mean natural leak 



Experimental „ 1st hour . 



„ „ 2nd ,, . 



No. 791. Natural leak... 



Experimeutalleak, 1st hour.. 



Natural leak after exhaustion, 



1st half hour 

 Ditto, 2nd half hour 



0'] 92 division per minute. 

 0-196 



0-239 

 0-410 

 0-531 

 0-484 



0-221 

 0-237 

 0-267 

 0-263 

 0-201 



(Flask found to be cracked, equilibrium value probably not attained.) 



No. 1 



iatural leak 0-303 division per minute. 



" immediately " 1-227 „ „ 



end of 1st hour 1-376 „ „ 



„ 2nd „ 1-676 „ „ 



„ 3rd „ 1-538 



No. 697 C. Mean natural leak 0-318 



Experimental, " immediately " 112 - 1 c 



„ end of 1st hour 146 3 



„ „ 2nd „ 153-8 



3rd „ 153-8 



Standard radium solution containing T57 



Natural leak 



Experimental, " immediately " 



„ end of 1st hour 



„ 2nd y, 



„ 3rd „ .. 

 „ 4th „ .. 



Natural leak after exhaustion, 



diately " 

 Ditto, 1st hour 



„ 2nd „ ..„. 



7 mgrm. of Ea — 



0- 319 division per minute. 



1- 370 divisions per minute. 



1- 714 



2- 083 

 2-143 

 2-000 



0-587 division per minute. 

 0-412 



0-307 „ 



Comparing the values obtained by the constant capacity electroscope with 

 the maximum values (less mean natural leak) obtained by the emanation 

 electroscope in the case of those substances examined by both methods, it 

 appears that a 20-per-cent. increase over the natural leak in the constant 

 capacity electroscope indicates the presence of radium, but, for values less 

 than this, the presence or absence of radium as detected in the emanation 

 electroscope cannot be predicted with certainty. 



