62 ELISHA MITCHELL SCIENTIFIC JOURNAL 



strongly active Thorium loses the largest part of its activity 

 within a few months, we have not yet secured Thorium 

 entirely free from the last remnant of activity. In company 

 with Dr. Baskerville I made some experiments about this, 

 using- the property of Barium and Lead to take with them the 

 activity, when precipitated in a mixture with an active salt 

 by means of sulphuric acid or Hydrogen sulphide. In these 

 experiments we did not use the original Thorium, but its three 

 components, about which Dr. Baskerville will speak to you in 

 a few moments. We dissolved a little quantity each of Ber- 

 zelium. Thorium and Caroiinium salt, one of which must 

 surely be the bearer of the original Thorium activity, added 

 a large excess of Barium chloride, kept the whole during 

 three days and then precipitated the Barium with sulphuric 

 acid. The Berzelium, Thorium and Caroiinium obtained from 

 the filtrate were then nearly inactive, but within two weeks 

 they regained their original activity. Nor did we succeed in 

 removing the activity from the original Thorium by adding a 

 large excess of Lead salt and precipitating the latter with 

 Hydrogen sulphide. 



While one may secure inactive Thorium direct from certain 

 minerals, it has been quite impossible so far to remove the 

 last remnant of activity from Thorium that has once been 

 active. 



As in the meantime Dr. Baskerville happened to divide the 

 old Thorium into three constituents, it is very interesting 

 indeed to investigate what part the three new elements take 

 in the radioactivity of the old Thorium. So far it has been 

 found that all three, although not in the same degree, are 

 active. But possibly the new elements are not yet pure 

 enough; hence we hope by further methods of purification to 

 reach that point, so that we can give with the description of 

 all their properties also this of the degree of their activity. 



