502 Boltwood — Life of Radium. 



treatment a considerable portion (about half) of the solution 

 of ionium was lost through an accident. The amount of radium 

 in the original mineral is therefore of no significance, but the 

 growth of radium in this solution is shown in Table IV. 



Table IV. 



Growth of Radium in Solution 4- 



Time from Ra Em found Growth of 



Test start expressed radium 



No. in days in terms of Ra per day 



1 6 0-loOXlO-g. 0-00875X10"^ 



2 140 1-37 X 10- 9 g. s 



The amount of radium present at the start was - 20XlO~ 9 g., 

 and the amount of radium produced per year would be 3*19 X 

 10~ 9 gram. 



Ionium Solution 5. 



The separation of the ionium from the relatively impure 

 materials used in preparing the first four solutions involved 

 very considerable difficulties. The minerals themselves were 

 not entirely soluble in any one reagent and various insoluble 

 residues were obtained from time to time which further added 

 to the complications. It was therefore doubtful in the end 

 whether a complete separation of the ionium had been effected. 

 In order to avoid these difficulties a solution of ionium was 

 prepared from a specimen of very pure uraninite from North 

 Carolina. The material used consisted of exactly 40 grams of 

 the mineral which was essentially free from traces of secondary 

 alteration products. It was heated with an excess of dilute 

 nitric acid and the solution was evaporated to dryness. The 

 residue was moistened with a few drops of dilute nitric acid, 

 was treated with hot water and the solution was filtered. The 

 insoluble material removed in this manner weighed only 0*0663 

 gram after ignition, corresponding to 0"17 per cent of the 

 material taken. It consisted chiefby of silica equivalent to 0"l-± 

 per cent of the mineral and only 0*03 per cent of other sub- 

 stances. Its activity was not greater than that of about one 

 milligram of uranium. 



The filtrate from this residue was first treated with an 

 excess of hydrogen sulphide and the sulphides of lead, etc., 

 removed. The excess of hydrogen sulphide was expelled from 

 the solution, which was than heated to boiling and a solution 

 of 10 grams of oxalic acid added. An immediate precipitation 

 of oxalates occurred and the solution was allowed to stand for 

 three hours until cold. The precipitated oxalates were filtered 

 off. The filtrate was evaporated to dryness and ignited to 

 destroy the oxalic acid. The residue was dissolved in nitric 



