254 M. Arfwedson on Uranium. [April, 



Method of preparing pure Oxide of Uranium. 



I expected at first to have been able to obtain pure oxide of 

 uranium without any tedious processes, by means of one of its 

 properties which has not been known for any considerable time ; 

 namely, that it dissolves with facility in carbonate of ammonia, 

 and is again precipitated from the solution by boiling; for 

 should some copper accompany it in the solution, the oxide of 

 uranium which first is precipitated ought to be quite free from all 

 admixture of that metal. 



A portion of pechblende from Johann Georgenstadt in Saxony, 

 which was apparently very pure, was reduced to a fine powder, 

 and digested with nitric acid till it was completely decomposed. 

 After this a little muriatic acid was added, which dissolved a 

 considerable portion of the straw-yellow matter, insoluble in 

 nitric acid. The filtered solution was supersaturated with car- 

 bonate of ammonia in great excess. A portion of the precipitate 

 was again dissolved by the carbonate, but the greatest part 

 remained undissolved ; and this proportion continued unaltered 

 though the whole was heated. The ammoniacal solution was 

 separated from the precipitate, and was examined by means of 

 processes which I consider it unnecessary to particularize in this 

 place, and to my astonishment 1 found it to contain the following 

 different substances; namely, oxide of uranium, oxide of copper, 

 a considerable proportion of oxide of cobalt, a little oxide of 

 zinc ; and the precipitate, besides all these bodies, contained 

 much arsenic mixed with oxides of iron and lead. If to these 

 we add the silica and sulphur not dissolved by the acids, we 

 shall find that the pechblende contains no fewer than nine differ- 

 ent substances. To free oxide of uranium from so many other 

 bodies occasioned a great number of fruitless trials. But I at 

 last succeeded in discovering the following method, by means 

 of which, so far as I can see, the protoxide of uranium may be 

 obtained in a state of complete purity. 



Finely pulverized pechblende is dissolved by means of a gentle 

 heat in a mixture of nitric and muriatic acids. When the 

 decomposition of the mineral is completed, and most of the acid 

 expelled, a little muriatic acid is to be added, after which the 

 liquid is to be diluted with a good deal of water. The sulphur, 

 silica, and a portion of the gangue, remain finally undissolved. 

 A current of sulphuretted hydrogen gas must now be passed 

 through the liquid as long as any precipitate continues to fall. 

 The precipitate is at first dark-brown, consisting of sulphurets of 

 copper, arsenic, and lead ; but at last it becomes yellow, and 

 consists of sulphuret of arsenic. The liquid is now free from 

 copper, lead, and arsenic, but it contains iron, cobalt, and a 

 little zinc. 



Let it be filtered and digested with a little additional nitric 

 acid to peroxidize the iron. By this process the light green 



