6 URANIUM, ANTIMONY, CHROMIUM, &c. 



Atom of peroxide of uranium weighs 28, and an atom of 



uranium , . i , /? 



and its ox. protoxide 27 ; hence the atomic weight or ura- 

 nium in the metallic state must be 26. 



2. It has been long known that uranium com- 

 bines with two proportions of oxygen, and forms 

 two oxides. Before proceeding farther, it will 

 be proper to give some account of these oxides ; 

 because none of the chemical books which I have 

 seen contain any thing on the subject. 



(!) Protoxide of uranium, obtained by expos- 

 ing the percarbonate of uranium and ammonia 

 to a red heat, is composed of small grains, hav- 

 ing a black colour, and a good deal of lustre ; 

 but when reduced to powder, it has a dark green 

 colour. It is soluble in muriatic and sulphuric 

 acid ; but the solution goes on very slowly, ex- 

 cept when the oxide is in the state of a hydrate. 

 The solutions are green, and the protoxide is 

 thrown down in the state of a brown coloured 

 hydrate, which dissolves very easily in acids, 

 forming a dark green solution. In nitric acid 

 the protoxide dissolves very readily with the evo- 

 lution of nitrous gas ; and by this solution it is 

 converted into peroxide. The protoxide of 

 uranium is tasteless, and not altered by exposure 

 to the air. It combines readily with the acids ; 

 all its salts have a green colour, and none that I 

 have tried is capable of crystallizing. 



ofunrium, ( 2 Peroxide of uranium has, I suppose, a 

 lemon yellow colour, at least this is the colour 



