The Radio-activity of Metals and their Salts. 

 Table I. 



281 



Lead 



PbS0 4 (l) 

 PbS0 4 (2) 

 PbS0 4 (3) 

 PbO 



9-3 



6-8 

 7-0 



7-2 

 8-2 



6-4 

 6-4 

 6-4 



8-6 



Tin 



SnS(l) 

 SnS (2) 

 SnS (3) 



4-4 

 4-1 

 39 



3-8 



3-4 

 3-4 

 3-4 



Bismuth 

 Bi 2 3 



6-0 

 5-7 



5-4 



Mercury 

 Hg 2 r 

 HgO 



0-9 

 0-5 

 0-6 



0-86 

 0-84 



8. I think it will be agreed by those who have had experi- 

 ence of the difficulties of similar measurements that the agreement 

 is sufficiently good to confirm the theory that the activity of the 

 common elements, like that of the radio-active elements, is an 

 atomic property. It must be remembered that an activity repre- 

 sented on this scale by 05 can only just be detected: the devia- 

 tions of observation and theory do not amount to much more than 

 this quantity. Only in the case of mercury are the deviations 

 large in relative, though not in absolute, amount. It should be 

 noticed that the whole activity of mercury is just on the borders 

 of the sensitiveness of the method. 



9. Attention must be drawn to the agreement of the values 

 obtained for each of the three samples of lead sulphate and each 

 of the three samples of tin sulphide. In the case of each metal 

 the three specimens were prepared from the same solution by 

 three distinct methods. In the case of lead the samples were 

 prepared as follows : — 



(1) By direct precipitation of lead acetate by sulphuric acid. 



(2) By precipitation with hydrochloric acid and subsequent 

 conversion into sulphate by boiling with sulphuric acid. 



