URANIN1TE. 193 



fully saturated, set aside in a covered vessel for twenty- 

 four hours. The sulphuretted hydrogen is then ex- 

 pelled by a gentle heat, and the precipitate filtered oft'. 



The precipitate contains arsenic, antimony, copper, 

 and the rest of the lead and bismuth. 



The solution is then heated to ebullition, and fuming 

 nitric acid gradually added to the boiling liquid, until 

 all the protoxide of iron is reconverted into sesquioxide, 

 and the solution has acquired a pure yellow color. 

 It is then precipitated by an excess of ammonia, and 

 the yellowish-brown precipitate filtered off. 



Part of the nickel, cobalt, zinc, lime and magnesia 

 remain in solution, but the remainder is precipitated 

 together with the sesquioxides of uranium and iron. 



The washed precipitate is treated with a hot, pretty 

 strong solution of carbonate of ammonia containing 

 free ammonia, with which the precipitate is digested, 

 at a moderate heat, until it has the appearance of hy- 

 drated sesquioxide of iron. The solution of uranium 

 is rapidly filtered off, while hot, and the residue of 

 hydrated sesquioxide of iron (still containing uranium) 

 is washed, the washings being received apart fronflhe 

 filtrate. 



The solution (which is yellow, or colored reddish 

 by the cobalt) deposits on cooling, if sufficiently con- 

 centrated, crystals of the pure double carbonate of 

 ammonia and sesquioxide of uranium, which may be 

 collected, and washed several times with cold water. 

 When ignited, this salt leaves pure dark green proto- 

 sesquioxide of uranium. 



The mother-liquor is mixed with the washings and 

 sulphide of ammonium carefully added, drop by drop, 

 as long as it produces a dark brown precipitate, which 

 is immediately filtered off. 



The precipitate consists of the sulphides of cobalt, 

 nickel and zinc. 



The yellow filtrate is then boiled till the greater part 

 17 



