Bolt-wood — Life of Radium. 501 



Table II. 



Growth of Radium in Solution 2. 



Time Radium emanation Radium. 



from start found growth 



Test No. days in terms of Ra per day 



0-0252X10" 



1 9 0-636X10 



2 32 1-31 



(V094.H a a t( 



3 196 5-35 " " " 



The average growth calculated from (1) and (3) was equiva- 

 lent to 0*0247 XlO -9 g. radium per day and the amount of 

 radium present at the start. was 0*65 XlO -9 gram. The 

 amount of radium produced per year would be 9'01XlO _9 g., 

 giving a value for X equal to 2 - 9xl0 -4 and a half-value period 

 of 2400 years. 



Ionium Solution 3. 



The ionium contained in this solution was separated from 

 200 grams of Joachimsthal uraninite by the chemical opera- 

 tions described in a former paper.* The mineral taken con- 

 tained 2"13XlO _? gram of radium per gram, or a total of 

 4*26 XlO -5 gram of radium. The data obtained on the 

 growth of radium in this solution are given in Table III. 



Table III. 

 Growth of Radium in Solution 3. 





Time from 



Ra Em found 



I 



Growth 





start 



expressed 





radium 



Test No. 



in days 



in terms of Ra 



per day 



1 



5-9 



0-0987 X10- a 



&• 





2 



23-9 



0-648 " " 



a 



0-0333X10 



3 



46 



1-397 " " 



a 



0-0339 " " 



4 



209 



6-97 " " 



a 



0-0342 " " 



The average amount of radium produced per day calcu- 

 lated from the results of the first and last tests only, was 

 0*0341 XlO -9 g., and the amount of radium in the solution at 

 the start was only - 0346XlO -9 gram. The amount of radium 

 produced per year in this solution would be 12-45 XlO" 9 gram, 

 giving a value of 2*92 XlO -4 for A. and indicating a half- value 

 period of about 2400 years for radium. 



Ionium Solution 4- 



This solution was prepared from about 100 grams of second- 

 ary uranium minerals, chiefly guinmite and uranophane, by 

 the chemical operations which have been already described in 

 the earlier paper.f During the later stages of the chemical 



* This Journal, xxv, 373, 1908. 

 f This Journal, xxv, 373, 1908. 



