Ellen Gleditsch — Life of Radium. 115 



The chief point will then be to make sure that all ionium 

 has been removed from the mineral. The following method 

 was adopted. All the rare earths contained in a mineral 

 solution were precipitated and removed by filtration. To the 

 solution was added a solution of a small quantity of rare earths 

 containing no radium or ionium and the precipitation was 

 repeated. After filtration a new quantity of rare earths was 

 brought in the solution and precipitated. The first two 

 precipitates were put together and, after a treatment, that will 

 be described later, were brought into solution and formed the 

 main solution. The third precipitate was treated separately 

 but in exactly the same way and constituted the test solution. 



If this test solution showed no growth of radium there 

 could be no doubt that all ionium had been removed from the 

 mineral and was in the main solution. 



Experimental Results. 



I shall now give a short description of the preparation of the 

 ionium solutions and the measurement of the growth of radium 

 in them. 



1. Ionium solution from Uraninite, North Carolina. 



The mineral was a very pure uraninite carefully freed from 

 all alteration products ; it contained 69*4 per cent uranium. 

 110 grams of the finely powdered mineral were dissolved in 

 warm nitric acid (30 per cent). The solution was evaporated to 

 dryness, the residue was moistened with nitric acid and dis- 

 solved in hot water. Filtration left only a very slight residue. 

 This residue was treated with hydrofluoric acid and evaporated 

 with some drops of sulphuric acid. A dilute hydrochloric acid 

 dissolved most of it ; the undissolved part was melted with 

 potassium hydrosnlphate and then it was completely dissolved 

 in water which was acidified with a little hydrochloric acid. 

 These two solutions were both precipitated with ammonia and 

 the slight precipitates were dissolved in dilute nitric acid 

 and added to the mineral solution. 



The main solution was now treated with an excess of hydro- 

 gen sulphide, the sulphides formed were removed by filtration 

 and a current of air was passed through the solution in order 

 to expel the hydrogen sulphide. The solution was heated to 

 boiling and some grams of oxalic acid were added. The solu- 

 tion was left over night and the oxalates formed were filtered 

 off (1). A solution containing about l - 25 grams of rare earths, 

 mostly thorium, was added to the filtrates" and, after heating, 

 the earths were precipitated by oxalic acid (2). After removal 

 of the oxalates 1*25 grams of rare earths were again added to 

 the filtrate and then an excess of oxalic acid ; the oxalates (3) 



