it 



136 Mixter — Heat of Combination of Acidic Oxides. 



• 



was less than 98 per cent of metallic tungsten in the prepara- 

 tion, but the lower oxides give heat when oxidized. Hence 

 we may assume without essential error that the thermal effect 

 is proportional to the amount of tungsten, which is equivalent 

 to the amount of oxygen taken up. After each calorimetric 

 experiment the product in the bomb was dissolved in water 

 aod the small residue remaining was separated. It dissolved 

 completely in nitric acid, showing that no metallic tungsten 

 remained. The following experiments give the heat of burn- 

 ing tungsten in sodium per oxide : 



Experiment 1. 



Tungsten 8-241 X 0-9814 = 8*088 grams 



Water equivalent of system. _■ 3596* 



Sodium peroxide 21* 



Temperature interval _.. 2'859° 



Heat observed 3596 X 2-8593 = 10281° 



" of oxidation of iron in tungsten and 



used for ignition .. —157° 



10124 c 

 For 1 gram of tungsten 1252° 



Experiment 2. 



Tungsten 8*503 X 0*9814 = _ 8 377 grams 



Water equivalent of system 3552* " 



Sodium peroxide - 25* " 



Temperature interval 3*020° 



Heat observed 35523* X 02 = 10727° 



u of oxidation of iron in tungsten and 



used for ignition — 125 c 



10602° 

 For 1 gram of tungsten __ 1267° 



The average is 1260 c for 1 gram and 231200° for 184 grams. 

 For the heat effect of Na 2 + W0 3 we have 



3Na 2 2 + W = Na a W0 4 '+ 2Na 2 + .. 231800° 



3Na 2 + 30 = 3Na 2 2 + 58200° 



Na 2 + W + 30 ■= Na 2 W0 4 + 291000° 



W + 30 = W0 4 + 196300°* 



Na 2 + W0 3 = Na 2 W0 4 + .._ 94700° 



* Delepine et Hallopeau, C. R., cxxix, 600. 



