EXTRACTION OF RADIUM FROM THE OLARY ORES. 149 



-concentrates are mixed with three times their weight of 

 salt cake (acid sulphate of soda) and fused in a reverberatory 

 furnace of sufficient capacity to take 500 kilos of concen- 

 trates and 1500 of salt cake in a single charge. Three 

 -charges can be put through in twenty-four hours. The 

 fused product, crushed to pass a sieve of eight holes to the 

 linear inch, is fed, in small amounts at a time, into wooden 

 vats fitted with agitators. Gold water is fed continuously 

 into the vats at the bottom and an overflow is provided 

 near the top. By suitably adjusting the conditions, it is 

 possible to separate out on the bottoms of the vats a con- 

 siderable amount of comparatively coarse material which 

 is almost free from radium and uranium. The turbid liquid 

 overflowing carries in suspension the radium lead and 

 barium as sulphates, together with a considerable amount 

 of finely divided silica; while in solution we have the 

 uranium rare earths, and part of the iron and acid earths 

 contained in the ore. 



The coarse residues are removed from the vats daily, 

 re- washed to free them from any undissolved fused product 

 and sent to the dump. The composition of these residues 

 is given in Table III. 



The overflow from the dissolving vats is pumped to large 

 lead-lined settling tanks and allowed to stand all night. 

 The "slimes" settle completely in twelve hours, and the 

 clear liquid is drawn off daily and treated for the recovery 

 of the uranium. The slimes which amount, when dried, to 

 approximately 10 per cent, of the weight of the concen- 

 trates, are collected weekly and treated for the recovery 

 of the radium as described below. 



The further steps in the treatment process may con- 

 veniently be described under two heads: — 



(a) The recovery of the uranium. 



(b) The recovery of the radium. 



