Mixter — Formation of the Oxides of Molybdenum, etc. 495 



The result for a gram molecule of tellurium dioxide is 

 159-5 X 636 = 101*400°. 



5 6 



Substance taken 10*060 grams 6*000 grams 



Comnosition of j Te0 3 8*209 " 5*478 « 



substance ( Te0 2 1*951 " 0*522 " 



Sulphur... 1*000 " 0*800 " 



Sodium peroxide 16* " 14* " 



Water equivalent of system.. 3,963* " 3,152* " 



Temperature interval . 2*802° 2*537° 



Heat effect 11,104° 7,996 c 



" " of oxygen evolved + 1,072° + 636° 



" " " Te0 2 — 1,241 c — 332 c 



u u a iron for ignition — 48 c — 48 c 



" " "sulphur — 5,27l c — 4,216 c 



" « " Te0 3 5,616 c 4,036° 



For 1 gram of Te0 3 _..- 684° 737° 



The mean of the results is 708, which gives for the reaction 

 Nsifi + Te0 3 = Na 2 Te0 4 + 175*5 X 708 = 124,300°. 



/Summary of results. 



3Na 2 2 + Te = Na 2 Te0 4 + 2Na 2 + 149*7° 



3Na 2 + 30 = 3Na 3 2 + 58*2° 



Na 2 + Te + 30 = Na 2 Te0 4 + 207*9° 



Na 2 + Te0 3 = Na 2 Te0 4 + 124*3° 



Te + 30 = Te0 3 + ._ > 83*6° 



Na 2 2 + Te0 2 = Na 2 Te0 4 + 101*4° 



Na 2 + O = Na 2 2 + 19*4° 



Na 2 + Te0 2 + O = Na 2 Te0 4 + 120*8° 



The heat of formation of crystalline tellurium dioxide is 

 207'9-120*8=87-l. Thomsen's result of 77*2° for Te0 2 Aq is 

 too low since TeCl 4 does not hydrolyze completely. The 

 result of experiments 5 and 6 giving 124*3° for the heat of 

 combination of Na 2 and Te0 3 is to be considered as approxi- 

 mate only on account of the large correction for oxygen set 

 free, and hence the heat of formation of Te0 3 derived is to be 

 regarded as an approximation. Since the trioxide and dioxide 

 of tellurium give nearly the same heat when fused with 

 sodium peroxide, it is evident that the oxidation of crystalline 



