Boltwood — Ionium, a New Radio-active Element. 373 



one gram of thorium nitrate was added to the filtrate and a 

 second precipitation of thorium oxalate was made in the solution. 

 The solution obtained by heating the mineral with hydro- 

 chloric acid was worked up by the same series of chemical 

 operations as that used in the preparation of the first solution 

 (p. 371). After the precipitate of thorium oxalate had been 

 removed more thorium nitrate was added and a second pre- 

 cipitation of the oxalate was made in the same solution. The 

 object of the second addition of the thorium salt was to 

 insure the removal of any of the new substance which had 

 escaped the first treatment. The four oxalate precipitates 

 were combined, were converted into chlorides and were again 

 treated with oxalie acid. The final oxalate was converted into 

 the chloride, was twice precipitated as the hydroxide to remove 

 the radium as completely as possible, and was finally obtained 

 as the chloride, in which form it was sealed up in a glass bulb 

 and the growth of radium observed. About thirty per cent 

 more radium was produced in this solution in a given time 

 than was produced in the first solution in the same period. 



Solution 3. This solution was prepared from a quantity of 

 Joachimsthal pitchblende weighing 200 grams. The chemi- 

 cal operations were essentially the same as those carried out 

 in the preparation of solution 2, except that the mineral was 

 first decomposed with dilute nitric acid. A considerable 

 residue remained after treating the insoluble material with 

 hydrofluoric and sulphuric acids. This residue was obtained 

 in solution by a series of operations, including fusion with 

 sodium carbonate, and this solution was separately treated with 

 thorium. The entire thorium material ultimately recovered 

 was freed from radium as completely as possible by repeated 

 precipitation with ammonia, and the growth of radium was 

 measured in this solution in the usual manner. 



Solution 4. This was prepared from about 100 grams of 

 secondary uranium minerals, consisting chiefly of gummite and 

 uranophane. No thorium was introduced into the solution 

 of this material, which contained naturally about one per 

 cent of thorium oxide and about two per cent of other rare 

 earths, but instead there was added a solution of about two 

 grams of oxides of rare earths obtained from a specimen of 

 cerite. This cerite had been found to be wholly free from 

 thorium, uranium or other active substances. The rare earths 

 were then separated in the usual manner, by precipitation as 

 oxalates The oxalates were converted into chlorides and the 

 thorium was removed in the customary manner by treatment 

 with sodium thiosulphate. The precipitate obtained was 

 digested with hot, dilute hydrochloric acid, the sulphur was 

 filtered off and the treatment with sodium thiosulphate was 



