Mixter — Heat of Formation of Titanium, Dioxide. 393 



Art. XXXIY. — The Heat of Formation of Titanium 

 Dioxide, and third paper on the Heat of Combination of 

 Acidic Oxides icith Sodium Oxide • by W. G. Mixter. 



[Contributions from the Sheffield Chemical Laboratory of Yale University] 



The thermochemistry of titanium is limited to that of the 

 reaction TiCl 4 +Aq=57,870 c (Thomsen). As the heat of for- 

 mation of the tetrachloride is not known, that of the oxide or 

 acid can not be calculated. Good results might be obtained 

 by burning titanium in oxygen if it could be ground to a fine 

 powder. A coarse powder burns well in sodium peroxide, and 

 hence this method was used.* 



The metal used in the investigation was made by Dr. M. A. 

 Hunter in the laboratory of the General Electric Company. 

 The specimen was in irregular nuggets, was malleable when 

 hot and brittle when cold. The density of a bright piece of 

 the metal was found to be 4*51 and that of the pulverized 

 portion 4*49 at 18°. Moissanf states that the density of tita- 

 nium is 4*87. But the purest he made in the electric furnace 

 contained two per cent of carbon. 



For use in the combustions the metal was pulverized in 

 diamond mortar and then ground in an agate one which it 

 did not scratch. It was impossible to grind it to a fine powder, 

 as some particles were flattened and others rounded. It was 

 assumed that the impurities adhering to the nuggets were 

 converted into dust by the grinding and also that the steel 

 from the mortar was dust. Accordingly the dust was floated 

 off in water and only the coarser portion retained. A qualita- 

 tive analysis revealed no impurities in the metal. For a 

 determination of titanium 0*5662 gram w r as dissolved in molten 

 potassium pyrosulphate, the fusion w r as dissolved in cold water 

 and the titanic acid was precipitated by boiling. The titanium 

 dioxide obtained weighed 0*9453 gram, equivalent to 0*5676 

 gram of titanium or 100*2 C per cent. The following are the 

 thermal data : 



1 2 



Titanium _ 2*000 grams 2-001 grams 



Sulphur 1-000 " 1-000 " 



Sodium peroxide 20 " 20 " 



Water equivalent of system.. 3,003 " 2,979 " 



Temperature interval . _ 4*958° 4*958° 



*The details of the sodium-peroxide method are given in the first paper, 

 on the Heat of Combination of Acidic Oxides with Sodium Oxide, in this 

 Journal, xxvi, 125. 



fC. E., cxx, 290. 



