46 Mixter — Heat of Formation of Titanium Dioxide. 



The average is 96*8. Presumably the powder had oxidized. 

 For the sixth and seventh experiments another lump of titanium 

 from the same lot as first used was broken up and only the 

 coarser portion used. It dissolved too slowly in hydrochloric 

 acid, hence a pyrosulphate fusion was made. The result with 

 0*3109 gram was lOO'l per cent of titanium. 



In the first five experiments all of the oxide taken from the 

 bomb was washed to remove a slight amount of silver nitrate 

 present. Then it was dried, weighed, dissolved in molten potas- 

 sium pyrosulphate and from the fusion Ti0 2 was obtained in 

 the usual way. The weight of the Ti0 2 obtained less that of 

 the oxide taken was the amount of oxygen required to com- 

 pletely oxidize the oxide. In the sixth and seventh experi- 

 ments a better method was used, namely : a weighed amount 

 of finely powdered oxide from the bomb was heated until it 

 ceased to gain in weight, the color changing from brown to 

 nearly white. 



To find the thermal effect of 32 grams of oxygen combining 

 with titanium in the same ratio as in a combustion in the bomb, 

 let 



m 1 = mass of titanium placed in the bomb. 



m 2 = mass of the portion used of the titanium oxides 

 taken from the bomb. 



m z = mass of oxygen added to m to convert all of it into 

 Ti0 2 . 



x = mass of titanium in M 2 . 



y = total mass of oxygen combined in the bomb. 



x 48-1 



m 

 y = m, — - — m. 



u 1 x J 



Let h equal observed heat minus the heat due to cotton, then 



- 32 is the heat effect of 32 grams of oxygen combining with 



titanium under the conditions of the calorimetric experiment. 

 In calculating the heat effect of 32 grams of oxygen in experi- 

 ments 4 and 5, m 1 is multiplied by - 968 since the powdered 

 metal used was found to contain 96*8 per cent of titanium. 



The table contains the experimental data and the results 

 derived. 



The heat effects of 48*1 grams of titanium combining with 

 oxygen in the same ratios as in the bomb are, owing to incom- 

 plete oxidation, too low for the reaction Ti + 2 = Ti0 2 . They 

 prove, however, conclusively that the heat of combustion » of 



