Uranium 

 Product. 



1*57 



Iron 

 Precipitate 



7'36 



0'51 



... 



... ... ... 



1-2 



... 



5*81 



8*21 



... 



EXTRACTION OF RADIUM FROM THE OLARY ORES. 151 



Rare earths 



Lead oxide 

 Vanadic oxide 

 Chromium oxide 



Sodium salts 



(b) Recovery of the Radium. 



The thickened insoluble residue or slime from the settling 

 tank is mixed with half its dry weight of strong sulphuric 

 acid and allowed to stand for several days. It is then 

 washed, first by decantation and then on a vacuum filter, 

 till the washings give only a very slight precipitate with 

 barium chloride. The acid treatment and washing reduces 

 the bulk of the slime considerably, removing large amounts 

 of acid earths and iron salts. The washed slime in quanti- 

 ties of about 200 kilos, dry weight, is then boiled in large 

 steel boilers with an excess of a 20 per cent, solution of 

 sodium carbonate for two days, the solution being replaced 

 once during the boiling. This treatment dissolves a large 

 amount of silica, and converts much of the lead, radium and 

 barium sulphates to carbonates. The slime is then washed 

 till the wash water gives no reaction for sulphates ; this 

 takes two days for each lot of 200 kilos. The washed slime 

 is then fed into a warm dilute solution of hydrochloric acid, 

 agitated for a couple of hours, and allowed to settle all 

 night. The clear solution is siphoned off and the lead, barium 

 and radium precipitated as sulphates. After washing once 

 by decantation, the slime is again treated as above described. 

 Two treatments suffice to extract most of the radium, but 

 the slime is reserved for a further treatment if necessary. 

 The plant as at present arranged, can treat the slime from 

 ten tons of concentrates per week. The weekly yield of 

 crude sulphate is about 12 kilos. 



During the past two years I have made a number of 

 experiments, both in the laboratory and on the working 



