272 M. Berzelius 07i Uranium. [Avril, 



from the residue carbonate of potash, and there remains an inso- 

 luble powder also of a tile red colour, which is a uranate of pot- 

 ash. 1-977 grm. of this compound dissolved in muriatic acid 

 and precipitated with ammonia, gave 1*686' grm. oxidule = 

 1'716 grm. oxide, and 04 grm. muriate of potash, = 0'253 grm. 

 potash. The oxygen of the oxide of uranium in this salt was 

 therefore double that of the potash. 



Uranate of potash, ignited in a current of hydrogen gas, 

 undergoes only a partial decomposition. After this treatment, 

 it still continues completely insoluble in water, but acids dissolve 

 from it uranate of potash, in which, therefore, the oxide is com- 

 bined with a still larger proportion of potash. The insoluble 

 residue consists of metallic uranium. 



As the uranate of barytes when precipitated by ammonia 

 from a solution of a salt of the oxide of uranium mixed with a 

 salt of barytes, is always accompanied with a variable quantity 

 of uranate of ammonia, the proportion of which depends in a 

 great measure on the relative proportions of the precipitant, and 

 of the two salts in the original solution, I considered it preferable 

 to form the salt by adding barytes water to a solution of nitrate 

 of oxide of uranium. The edulcoration of this precipitate is an 

 uncommonly tedious process, and 1 remarked that after having 

 been repeatedly boiled in fresh quantities of water, it still parted 

 with as much barytes as at first. In washing a few grammes of 

 the salt, I expended in this manner several gallons of water 

 before I felt satisfied that it had ceased to give off a sensible 

 quantity of barytes. Thus prepared, the salt has a flame yellow 

 colour, but it becomes pomegranate red after ignition. I decom- 

 posed it by solution in muriatic acid, and by precipitating the 

 barytes by sulphuric acid, and the oxide of uranium by ammonia. 

 From '2']28 grm. of the ignited salt, I obtained 0"451 grm. of 

 barytes and 1*677 grm. of oxide of uranium. The oxygen of the 

 barytes was, therefore, rather more than one-half of that of the 

 oxide of uranium ; but this excess is probably occasioned by 

 the difficulty of washing out completely the last portions of the 

 barytes. In the experiment in which iVi. Arfvvedson found the 

 oxide of uranium combined with the smallest proportion of 

 barytes, 100 parts were combined with lt)-9 parts of the earth, 

 which, by virtue of its affinity, prevented the oxide from being- 

 decomposed by ignition. The oxygen of the barytes in this 

 compound was, therefore, one-third of that of the oxide of 

 uranium. 



Hence it would appear, that when the oxide of uranium predo- 

 minates, it combines with bases in such a proportion that its 

 oxygen is thrice that of the base, and that when the base predo- 

 minates, the oxygen of the oxide of uranium is twice that of the 

 base. From the phenomena which take place during the treat- 



