Mixtev — Beat of Formation of Titanium Dioxide. 395 



same compound results in both cases. Moreover, it makes no 

 difference in the heat effect of Ti + 20 derived whether we 

 assume the formation of Na 2 2 .Ti0 3 obtained by Mellikoff 

 and Pessarjewsky* or JSTa 2 O.Ti0 3 . Taking the latter com- 

 pound, the calculations are as follows : 



3Xa 2 2 + Ti = Na 2 O.Ti0 3 + 2Na 2 + 227,100 c 



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



285,300 c 

 Na 2 + Ti0 + O = Na o 0.Ti0 3 69,700 c 



Ti + 20 = Ti0 2 (amorphous) + 215,600 



Na 2 2 + Ti0 2 = Na 2 O.Ti0 3 + 50,300 c 



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



Na s O + Ti0 2 + O = Na 2 O.Ti0 3 + ._ 69,700 c 



The large heat of formation of titanium dioxide was to be 

 expected because of the difficulty of reducing the oxide to the 

 metal. The heat of combination of Ti0 2 or Ti0 3 with Na 2 

 cannot be calculated from the experimental results, but it is 

 less than that of silicon dioxide. 



Lead. 



Lead, in a finely divided form for the work, was obtained by 

 scraping a revolving cylinder of the metal with a thin tool. 

 The experimental data were as follows : 



Lead 20 grams 



" unburned 0*94 



" burned 19*06 



Sulphur 1 



Sodium peroxide 20 



Water equivalent of system 3,982 



Temperature interval 2*822° 



Heat observed ] 1 ,237 c 



" of oxidation of sulphur — 5,271 c 



" " " " iron — 48 c 



" " oxygen absorbed — 62 c 



5,856 c 



For 1 gram of lead .... 307 c 



" 206*9 grams 63,500° 



*Ber. d. deutsch. cliem. Gesell., zxxi, 953. 



