URANIUM. 7 



by which most of its salts are distinguished. 

 Such is its tendency to combine with other bodies 

 that it seems impossible to obtain it in a sepa- 

 rate state. It dissolves with ease in nitric acid, 

 and forms a lemon yellow solution of great in- 

 tensity, which crystallizes and forms the nitrate 

 of uranium in fine lemon yellow crystals, having 

 the form of right four-sided prisms with square 

 bases. If we throw down the oxide from this 

 salt by caustic ammonia or soda, it retains these 

 alkalies in combination, from which it cannot be 

 freed by washing. If we throw it down by car- 

 bonate of ammonia, we obtain a yellow powder, 

 which is most frequently a percarbonate of urani- 

 um ; but sometimes, a triple salt composed of 

 carbonate of ammonia and percarbonate of ura- 

 nium. If we throw it down by potash or soda, 

 we obtain a beautiful orange red powder, which 

 is a triple compound of percarbonate of uranium 

 and an alkaline carbonate. Arfwedson has 

 shown, that if we mix together solutions of per- 

 nitrate of uranium and any earthy or metallic 

 nitrate, and add caustic ammonia or potash to 

 the solution, the peroxide of uranium precipi- 

 tates in chemical combination with the earthy or 

 metallic oxide present. 



Thus it appears, that peroxide of uranium is 

 capable of uniting both with acids and with 

 bases ; so that it performs the double function 

 of an alkali and an acid. None of the simple 



A4, 



