266 M. Arfwedson on Uranium* [April, 



barytes is reduced ; and the alloy of uranium andiron burns still 

 better than either of the others. 



Uranium appears to have a very weak affinity for sulphur. 

 The sulphuret may be obtained by the moist way, as is already 

 known, if a solution of uranium be precipitated by an alkaline 

 hydrosulphuret ; but I have not been able to succeed in forming 

 sulphuret of uranium by the dry way. When dry sulphuretted 

 hydrogen gas is passed over red-hot protoxide of uranium, the 

 oxide is reduced immediately, water and sulphur exhale, and a 

 body remains in all respects similar to the metallic uranium, 

 and which contains only 1*61 per cent, of sulphur. 



Salts of Uranium. 



The protosalts of uranium in a state of purity are not easily 

 prepared. If we dissolve protoxide of uranium in concentrated 

 sulphuric or muriatic acid (which, in the second case, goes on 

 very slowly), the solution at first is dark bottle-green; but it 

 becomes gradually lighter, and at last assumes a greenish-yellow 

 colour from the formation of peroxide. The sulphuric acid solu- 

 tion when evaporated deposits a light green confusedly crystal- 

 lized mass which contains a mixture of protoxide and peroxide 

 of uranium. The muriatic acid solution may be evaporated to 

 dryness without the deposition of any crystals. 



Persalts. — The persulphate of uranium is formed, when nitric 

 acid is added to a solution of protosulphate of uranium. This 

 addition, the green colour speedily passes to yellow, even with- 

 out the assistance of heat. 



The salt does not crystallize even when evaporated to the con- 

 sistence of a syrup. If we continue the application of the heat 

 after the salt has become dry, the oxide loses a portion of its 

 oxygen, and the mass acquires a greenish-yellow colour. 



Pernitrate of uranium is formed when the protoxide is dis- 

 solved in nitric acid. The solution goes on with rapidity, espe- 

 cially if assisted by heat. Nitrous gas is disengaged, and we 

 obtain a yellow liquid, which, when evaporated, shoots into long 

 prismatic crystals of a fine yellow colour. The salt dissolves 

 readily in water, and is decomposed in a comparatively low tem- 

 perature ; oxygen gas is also disengaged, and pernitrate of 

 uranium formed. When heated just to redness, it is decomposed 

 completely ; nitrous acid is driven off, and protoxide of uranium 

 remains. 



Permuriate of 'uranium is formed in the same way as the per- 

 sulphate. It does not crystallize, though evaporated to the 

 consistence of a syrup. The dry salt is very deliquescent. 



Percarbonate of uranium has been already described. 



Double Salts. 



Peroxide of uranium seems to have a great disposition to form 

 double salts in combination with other bases. It has been 



