Oxides of Vanadium and Uranium. 



151 



The first five experiments were made with the metal contain- 

 ing 99*4 per cent of uranium, and the last two with the 98 per 

 cent lot. From the result it is found that 1 gram of oxygen com- 

 bining to form U 3 O a gives a heat effect of 6590°. What is the 

 composition of oxide coating on the metal taken is not known, 

 but it probably is a lower oxide and hence the heat effect of its 

 formation may be a little higher. However this may be, the 

 product of 6590 by the oxygen content of metal taken is added 

 to the observed heat effect in the following experiments : 



12 3 4 5 6 7 



Metal taken... 1-7294 2-1944 2*1136 2-8266 4-7255 5-0623 4-4108 grm. 



Composition of 



metal IT (a)... 1*7190 2-1812 2-1009 2-8096 4-6971 4-9611 4*3226 " 

 0(b)... 0*0104 0*0132 0*0127 0*0170 0*0284 0*1012 0*0882 " 



Cotton 0*0899 0*1005 0*1012 0*0928 0*0822 0*0830 0*0795 " 



Water equiva- 

 lent of system, 1352 1343 1466 1329 2979 2995 2867 " 



Temperature in- 

 terval 1*601° 2*119° 1-916° 2*704° 1*857° 1*836° 1*674° 



Heat effect 2168 c 2846° 2809 c 3594° 5532° 5549° 4803 c 



Heat effect of 

 cotton —363 —404 —405 —374 —329 —335 —321 



Heat effect of b +68 +87 + 84 + 112 + 187 + 666 + 581 



Heat effect of 

 uranium (c) .. 1873 2529 2488 3332 5390 5830 5063 



Heat effect 1 

 gram of urani- 

 um- 1089° 1169° 1184 c 1186° 1147 c 1175° 1176 C 



a 



Composition of 

 product of com- 

 hnstion U,0,.„ TJ,0, M TT 3 O 804 U 3 O 8 . 00 U 3 O,. 10 IT 3 0,. 88 IT 3 7 . 94 



Excluding the results of 1 and 5, in which the oxidation was 

 less complete than in the others, the mean is 1178 c . For the 

 heat of formation of U 3 8 we have 1178 c X 238*5 X 3 = 842,- 

 900 c at constant volume and 815,200° at constant pressure. 



The metal having 98 per cent of uranium was not all in a 

 powder adapted for combustion with sodium dioxide, hence 

 the friable pieces were broken up and only the fine powder 

 used. It was now found to contain 97' 5 per cent of uranium. 

 Allowance is made as before for the oxygen content of the 

 metal in reducing the following observations : 



