Ellen Gleditsch — Life of Radium. 117 



Table 3. 



Growth of radium in test solution from uraninite, N. Carolina. 



Radium emanation found 

 Time from start expressed in Growth of radium 



Test 



in days 



1 



2-72 



2 



486-00 



terms of radium per day 



0'312 X 10~ 9 

 0-838 X 10" 9 



0-00005 X 10" 9 



The solution shows no appreciable augmentation of radium 

 and may be considered free from ionium. There is every 

 reason to believe that all the ionium was contained in the first 

 two solutions. 



The entire growth of radium was : 



per day : 0-025 X 10" 9 

 or per year : 9*13 X 10~ 9 



The radium present in the solution at the start was : 



1 3 X 10~ 9 .gram. 



The amount of radium in the mineral was determined in an 

 average sample. 110 grams of mineral contained 2'46 X 10 -5 

 grams of radium. 



Ra = °' 13 ? 10 ~' =,3--71, 10-* (year)-i 

 2-46 X 10- 5 ' VJ ; 



The half-value period of radium is given by : 



AT = log e 2 



m loo- 2 0-693 



or : T = ' = — = 1865 years. 



A 3-71, 10" 4 J 



The growth of ionium in this first ionium solution already 

 indicates that the period found by Boltwoocl (2000 years) is too 

 high. At the same time it must be admitted that the precipi- 

 tation as oxalates has not been a very effective one; and 4 per 

 cent of the ionium is found in the test solution. 



2. Ionium solution from Cleceite, Norway. 



Cleveite is a primary uraninite containing about 10 per cent 

 of rare earths; it occurs in pegmatite dikes in Norway. The 

 sample used was from Saetersdalen. 180 grams of the mineral 

 were treated with nitric acid (30 per cent) and most of it dis- 

 solved quickly. The residue consisted chiefly of silica and a 

 further treatment with hydrofluoric acid and sulphuric acid 

 reduced it to about five grams. This residue showed an activ- 

 ity about three times that of uranium and probably contained 

 a little radium. It was ignited with sodium carbonate, and the 

 fused mass was heated with water and a little hydrochloric 



