URANIUM. 3 



of minerals mechanically mixed. Galena and 

 copper pyrites may be occasionally observed in- 

 terspersed through it. Arfwedson informs us 

 that he found in it arsenic, cobalt, and zinc, in 

 addition to the iron, and copper, and lead which 

 had been noticed by Klaproth. In the speci- 

 mens of pitchblende which I examined I could 

 find no traces of arsenic, cobalt, or zinc ; but 

 copper and iron existed in abundance, and like- 

 wise some lead. My method of obtaining the 

 peroxide of uranium was the following : The 

 pitchblende was reduced to powder, and digest- 

 ed in nitric acid till every thing soluble was 

 taken up. The solution was rendered as neutral 

 as possible by evaporation. A current of sul- 

 phuretted hydrogen gas was then passed through 

 it till every thing precipitable by that means was 

 thrown down. The precipitate was at first dark 

 brown, and it always retained that colour to the 

 very end ; not the least appearance of any thing 

 yellow (to lead to the suspicion of the presence 

 of arsenic) could be detected. The solution, 

 thus freed from copper and lead, was filtered, 

 and, after being heated to drive off the sulphuret- 

 ted hydrogen, was precipitated by, caustic am- 

 monia. The precipitate thus obtained was 

 washed and separated on the filter ; and, while 

 still moist, was digested in a pretty strong solu- 

 tion of carbonate of ammonia. A fine lemon 



yellow solution was obtained ; and there remain- 



A 2 



