Oxides of Vanadium and Uranium. 



153 



It has been shown* that the heat of the reaction, Na 2 + 

 R0 3 , increased regularly with the atomic weights where R, is 

 chromium, molybdenum, and tungsten. Uranium falls a little 

 below the line extended from the others as shown in the figure 

 in which the atomic weights are platted as abscissas and the 

 heat effects as ordinates. 



100 



60 



Cr 



Mo 



W 



U 



Uranium forms peruranates, hence the question, Do uranium 

 oxides react in fusion with sodium peroxide to make a perura- 

 nate ? The calorimetric results show that only sodium uranate 

 results, since in experiment 12, where the amount of sodium 

 dioxide present was only sufficient to form sodium sulphate, 

 the heat effect is the same as it was in the other experiments 

 with an excess of dioxide. All of the fusions in the bomb 

 were orange color. Those of 10 and 11 mostly dissolved in 

 cold water with evolution of oxygen, yielding an orange or 

 reddish solution of peruranate. The solution, gradually at 

 room temperature and quickly on boiling, became lighter 

 colored and deposited a hydrous mixture of uranates having 

 approximately the composition 3Na 2 0, 8U0 3 4- XH 2 0. The 

 solution of peruranate mentioned was the result of the action 

 of water on the mixture of sodium uranate and dioxide, for it 

 was found that the former dissolves in a cold solution of sodium 

 dioxide with formation of peruranate. 



Uranium Dioxide. 



Uranium dioxide was made by reducing the trioxide mixed 

 with a little green oxide by hydrogen at a dull red heat. The 

 combustions with sodium dioxide were as follows : 



14 



15 



16 



Uranium dioxide 



5-000 



10-000 



5-000 



Sulphur 



1-000 



1-000 



1-000 



Sodium dioxide 



14- 



14- 



14- 



Water equivalent of sys- 









tem 



2967 



3101 



3077 



Temperature interval 



2-478° 



3-037° 



2-393' 



Heat effect 



7352 c 

 — 5270 



9418 c 

 — 5270 



7363 



" " of sulphur.. 



— 5270 



" " of iron 



— 40 



— 40 



— 40 



" of U0 2 



2042 



4108 



2053 



" 1 gram UO . 



408 c 



411 c 



410° 



grams 



* This Journal, xxix, 490. 



