Boltwoocl — Radio-activity of Uranium Minerals. 289 



That the active substance separated on the copper plates and 

 bismuth buttons was wholly polonium was demonstrated by 

 measurements of its rate of decay, which corresponded closely 

 to that of polonium (Rutherford, Radioactive Transformations, 

 p. 127). 



Activity of Ionium. 



A preliminary notice of the occurrence in uranium minerals 

 of a new radio-active element showing a chemical behavior 

 similar to that of thorium has already been published.* Details 

 concerning the chemical and radio-active properties of this 

 interesting substance will be given in a later paper, f where it 

 will be shown that ionium emits a particles having a range of 

 a23proximately 2'8 cm in air and is the immediate substance from 

 which radium is produced. For the present it will be assumed 

 merely that the ionium is separated with the thorium in a 

 mineral, an assumption which is supported by the experiments 

 of Hahn,^: who has observed its presence in the purified tho- 

 rium salts prepared by technical methods. 



Experiment 1. One gram of uraninite (No. 4, Table IT) 

 was decomposed by heating with dilute nitric acid and the 

 solution was evaporated to dryness. The residue was treated 

 with a few drops of nitric acid and hot water, and the insol- 

 uble matter was filtered off. The sulphides were precipitated 

 with hydrogen sulphide and removed. After the removal of 

 the excess of hydrogen sulphide exactly 0*2 gram of thorium 

 nitrate was added to the solution. This nitrate had been 

 prepared shortly before by a method which insured its free- 

 dom from mesothorium,§ and the proportion of thorium oxide 

 in the salt had been accurately determined. The solution was 

 heated to boiling, an excess of oxalic acid was added, and the 

 mixture was allowed to stand for 24 hours. The precipitated 

 oxalates were filtered off, and ignited. The oxides were fused 

 with sodium bisulphate and the melt dissolved in water. The 

 precipitation with oxalic acid was repeated, the oxalates were 

 converted into oxides by intense ignition over the blast-lamp, 

 and the weight of the oxides was accurately determined. A 

 portion (90 per cent) of the oxides was removed, again con- 

 verted into the soluble sulphate, and the rare earths were pre- 

 cipitated as hydroxides with ammonia. The hydroxides, after 

 thorough washing with hot water, were dissolved in hydro- 

 chloric acid and the solution was evaporated to dryness. A few 

 drops of dilute hydrochloric acid were added to the residue of 



*Boltwood, this Journal, xxiv, 370, 1907 ; Nature, lxxvi, pp. 544, 589, 1907. 



t This Journal, May, 1908. 



JBer. d. chem. Ges., xxxx, 3304, 1907; ibid., xxxx, 4415, 1907. 



§ Boltwoocl, this Journal, xxiv, 93, 1907. 



