151 



Miiter — Heat of Formation of the 



The average, 410 C X 270*5 = 110,900 c for the heat effect of 

 UO, + tf aA = Na s U0 4 . 



In the following combustions of uranium dioxide with oxygen 

 the same lot of dioxide was used except in the 21st experiment. 

 For this the dioxide was from the reductions of the higher 

 oxides resulting from burning the dioxide in oxygen. 



17 18 19 20 21 



Uranium dioxide (a) _. . 9-262 11*304 12-000 10-400 51-40 grms. 



Cotton 0-1148 0-0957 0-1025 0-1048 0-304 " 



Composition of product 



of combustion U 3 O,. 90 U 3 7 . 99 U,0,. 8I U,0,,, U 3 7 . a6 



Uranium dioxide burned 



to U s 6 (b) 8-799 11-247 10-810 9-984 50-11 " 



Water equivalent of 



system. 1383 1384 1281 1292 2619 " 



Temperature interval . . 0-905° 1-048° 1-132° 1-006° 2-139° 



Heat effect 1251 c 1450° 1450° 1300° 5664° 



" " of cotton —461 —386 —414 423 1211 



" " ofUO a (c).__ 790 1064 1036 877 4453 



" " 1 gram UO,4- 90 c 95° 96 c 88° 87 c 



b 



The mean, 92 c X 270*5 = 24-900 c at constant volume and 

 25,100° at constant pressure for the heat of oxidation of 1 gram 

 molecule of uranium dioxide when U 3 6 is the product. 



Urano- Uranic Oxide. 



This oxide, U 3 8 , used in experiments 22 and 23, was made 

 by igniting the nitrate, then heating the residue and allowing 

 it to cool slowly in oxygen. The weight was unchanged 

 when heated and coated again in oxygen. The oxide used in 

 experiment 24 was that formed by burning uranium dioxide in 

 experiment 21, and which has the composition U 3 795 . 



22 23 24 



Urano-uranic oxide... 10-000 10-000 10-000 grams. 



Sulphur 1-000 1-000 1-000 " 



Sodium dioxide. 13- 12-8 13- " 



Water equivalent of system . 3075 3047 2867 " 



Temperature interval 2*737° 2-757° 2-949° 



Heat effect 8416 8400 8454 



" " of sulphur —5270 —5270 —5270 



" " of iron —40 —40 —40 



" " of oxvgen set free +281 +282 +313 



" " ofU,0 B . 3387 3372 3467 



" " 1 gram of U 3 8 ._ 339 c 337 c 347 c 



