Boltwood — Ionium, a New Radio-active Element. 371 



Sometime before this Rutherford had published* a brief 

 account of an experiment in which he had attempted, without 

 success, to detect the growth of radium in a solution of Gie- 

 sel's " emanating substance," and had stated that measurements 

 extending over a period of three months indicated that if 

 radium was produced at all, it was produced at a very small 

 fraction of the theoretical rate. 



In spite of the unpromising outlook, the following experi- 

 ment was undertaken with the object of further investigating 

 the existing relations. A kilogram of rather low grade car- 

 notite ore was treated for some time with hot, dilute hydro- 

 chloric acid and the considerable residue of insoluble matter 

 remaining was removed by filtration. The solution was then 

 treated with hydrogen sulphide and the precipitated sulphides 

 filtered off. The filtrate was heated to boiling, and about two 

 grams of thorium nitrate (from monazite), followed by a large 

 excess of oxalic acid, were added. The mixture was allowed 

 to stand for several days, when the precipitated oxalates were 

 removed, converted into nitrates, and the precipitation with 

 oxalic acid was repeated. The second precipitate, consisting 

 almost wholly of thorium oxalate, was ignited to form the 

 oxide, the oxide was treated with sulphuric acid to obtain the 

 sulphate, and the sulphate in dilute solution was treated with 

 an excess of ammonium hydroxide. The hydroxide was 

 filtered off, washed thoroughly with hot water, dissolved in 

 dilute hydrochloric acid and again precipitated with ammonia. 

 After washing with water, the second precipitate of hydrox- 

 ides was dissolved in a small volume of hydrochloric acid and 

 the solutionf was sealed up in a glass bulb. About two 

 months later the gases in the bulb were removed by boiling 

 the solution and the activity of the radium emanation present 

 was determined in an air-tight electroscope. The bulb was 

 then sealed up for a further period of 193 days, when the 

 gases were again collected and tested. The amount of radium 

 emanation found in the second case was nearly twice as great 

 as that found in the first. It was evident that the amount of 

 radium contained in the solution had increased during the 

 interval between the tests and that the particular substance 

 from which radium was derived had been separated with the 

 thorium. In view of the results of my earlier experiments on 

 the activity of the thorium treated in this manner, I was led to 

 assume that the active substance associated with the thorium 

 was actinium, or at all events the " actinium " described by 

 Debierne in his early papers. The results obtained on the 

 growth of radium were published in the form of a prelimi- 



*Phil. Trans. Roy. Soc. Lond., cciv, 218, 1904. 



f This solution is referred to in the following pages as "solution 1." 



