1824.] M. Arfwedson on Uranium. 261 



fused muriate of lime, previously exactly balanced to determine 

 its weight. 



From 2*3 grammes of uraniate of lead, previously heated to 

 redness, were obtained in this way 0*164gr. of water, equivalent 

 to 0-1459 oxygen.* 



0628 gramme of uraniate of lead, prepared at the same time, 

 were dissolved in nitric acid. The solution was mixed with 

 sulphuric acid in sufficient quantity to saturate the oxide of 

 lead, and then evaporated almost to dryness. I found it neces- 

 sary to dissolve the uraniate of lead in the first place in nitric 

 acid ; for if it be decomposed directly by sulphuric acid, it is not 

 possible to obtain the sulphate of lead white, and quite free from 

 oxide of uranium. The mass was finally digested in alcohol, 

 which dissolved the sulphate of uranium, and left the sulphate 

 of lead. This last salt was collected on a filter, and washed 

 with alcohol. After being heated to redness, it weighed 0*485 

 gr. which corresponds with 0*357 protoxide of lead. The 

 remainder of the 0-628 amounting to 0*271 was of course per- 

 oxide of uranium. Thus it appears that 2*3 uraniate of lead 

 consist of 1*307 protoxide of lead, and 0*993 of peroxide of 

 uranium. The oxygen in the former of these constituents is 

 0*0937 ; but the oxides of lead and uranium had together lost 

 0*1459 of oxygen; and consequently 0*0522 of oxygen must 

 have belonged to the peroxide of uranium. It follows ultimately 

 that 100 parts of peroxide of uranium contain 5*252 of oxygen. 



The experiment was repeated with a uraniate of lead of 

 another preparation ; because all the first stock was exhausted. 



1*26 gr. reduced by means of hydrogen gas, gave 0*0785 

 water, corresponding with 0*0698 oxygen ; 1*258 gr. of the salt 

 was decomposed by sulphuric acid, and was found to be a com- 

 pound of 0*173 protoxide of lead, and 1*085 peroxide of uranium. 

 1*26 gr. of the uraniate of course consist of 0*1733 protoxide of 

 lead and 1*0867 peroxide of uranium ; which together contain 

 0*0698 oxygen ; but 0*1733 protoxide of lead contain 0*0124 

 oxygen. Thus it appears that the oxygen in 1*0867 peroxide of 

 uranium is 0*0574; and 100 parts of peroxide of uranium con- 

 tain 5*282 oxygen. The preceding experiment gave 5*252 ; the 

 mean of both is 5*267. From this it follows, that 100 parts of 

 uranium, in order to become peroxide, must combine with 5*559 

 oxygen. 



But that the whole might not depend upon a single set of 

 experiments, I determined likewise to analyze 



Uraniate of Eari/tes. 



It was prepared in this manner. A mixture of the solutions 

 of permunate of uranium and muriate of barytes, both previously 

 boded, was precipitated by caustic ammonia. The precipitate 



• The oxygen in the water was reckoned 88'9<t per cent, according to the experi- 

 ment* of Berzeliug and Dulong. 



