Boltwood — Ionium, a New Radio-active Element. 379 



removed and the substances precipitated by hydrogen sulphide 

 were separated. The nitrate from the sulphides was treated 

 with an excess of oxalic acid, the oxalates were further puri- 

 fied, and treated, as chorides, with an excess of sodium thio- 

 sulphate. After repeated precipitation with thiosulphate a 

 few milligrams of material which was free from actinium and 

 actinium products was finally obtained. This material con- 

 tained ionium having an activity about equal to that of a 

 half gram of pure uranium. The almost complete absence of 

 thorium in this product was quite unexpected, and it is not 

 impossible that the thorium and ionium may have been unde- 

 signedly separated in the early treatment of the residue. It is 

 not unlikely, moreover, that the greater proportion of the 

 thorium and ionium present in the original mineral is not 

 retained in the insoluble residue but is removed with the crude 

 uranium salts which are separated in the technical process of 

 manufacture. 



Production of Ionium by Uranium. 



If ionium is produced directly from uranium X it ought to 

 be possible under suitable conditions to determine this fact by 

 direct experiment. With this object in view I have made 

 some preliminary experiments, using a portion of my carefully 

 recrystallized uranium nitrate" prepared nearly four years 

 ago. By certain chemical operations, it was found possible to 

 separate a small quantity of material free from uranium and 

 emitting an a radiation. The final, permanent activity of this 

 substance was slight, but was of about the magnitude to be 

 expected for the activity of ionium if this had been formed 

 directly from the uranium. Further experiments on larger 

 quantities of uranium salts are now in progress and it is 

 hoped that the question of the production of ionium by ura- 

 nium can ultimately be decided with a satisfactory degree of 

 certainty. 



Chemical Properties of Ionium. 



The chemical properties of pure ionium can not be definitely 

 determined until it has been possible to examine weighable 

 amounts of this element. But from the data which has been 

 already obtained it would appear probable that it belongs to 

 the group of elements commonly known as the rare earths 

 and forms salts which are in general isomorphous with those 

 of thorium. The separation of ionium from thorium presents 

 indeed a difficult problem, and I have been unable to discover 

 any indications that even a partial separation can be effected 

 by the use of such characteristic reactions as the precipitation 



* This Journal, xx, 239, 1905. 



