Oxides of Vanadium and Uranium. 155 



The last result should uot be included in the final value since 

 the oxide used in the experiment contained a small excess of 

 the dioxide. The average of experiments 22 and 23 is 338°. 

 For 1 gram molecule of U 3 6 the result is 285,100°. Exper- 

 iment 24 shows that the TJ 3 6 formed at high temperature 

 does not differ essentially from the ordinary so-called green 

 oxide. 



Summary of Residts. 



3U + 40 = U 3 B + - 845,200 c * 



U + 3Na 2 2 = Na 2 U0 4 + 2Na 2 + 341,800 * 



3Na 2 + 30 = 3Na 2 2 + 58,200 



U 4- 30, + Na 2 = Na 2 U0 4 400,000 



U0 3 + Na 2 = Na 2 U0 4 + 96,100* 



tl + 30 = U0 3 + 303,900 f 



UO, + Na„0, = Na 2 U0 4 + 110,900* 



Na 2 + 0"= Na 2 2 + 19,400 



U0 2 + 0+ Na 2 = Na 2 TT0 4 + 130,300 



U0 3 + Na„0 = Na 2 U0 4 + 96,100* 



UO, + = U0 3 + -. 34,200 f 



3U0 2 + 20 = U 3 8 mean + 75,300 * 



highest + 78,100* 



U 3 6 + Na 2 2 + 2Na 2 = 3Na 2 U0 4 + 285,100 * 



Na 2 + O = Na 2 2 + 19,400 



U 3 8 + O + 3Na 2 3 = 3NaJJ0 4 + 304,500 



3U0 3 + 3Na. O = 3Na a U0 4 + 288,300 



U 3 8 + O ='3UO s + 16,200 f 



* Experimental result. f Derived result. 



From the foregoing data the following are derived from the 

 combustions with 



Sodium 

 Oxygen dioxide 



3U + 40 2 845,200° 895,500° 



U + 2 256,600 269,700 



3U0 2 -I- 2 75,300 86,400 



The results with sodium dioxide are 5 per cent higher than 

 with oxygen in the first two cases and 11 per cent in the last. 

 Regarding the accuracy of the various figures this may be said : 

 845,200 is to be regarded as good since it is the mean of closely 

 results of burning in oxygen two different samples of metal 

 with different contents of oxygen. If it be assumed that the 

 oxide on the metal is U0 2 instead of U 3 B , which was taken 

 as the basis for correction in experiments 1 to 7, the result 

 will be a little higher. The burning of uranium dioxide in 



