Mixter — Heat of Combination of Acidic Oxides. 125 



Art. XV. — The Heat of Combination of Acidic Oxides 

 ' with Sodium Oxide, and the Heat of Oxidation of Chro- 

 mium / by W. Gr. Mixter. 



[Contributions from the Sheffield Chemical Laboratory of Yale Univ.] 



It is the purpose of the writer to accumulate data on the 

 heat effect of the union of acidic oxides with sodium oxide, 

 and to determine if the position in the Periodic System and 

 the magnitude of the atomic weight of an element have a 

 marked influence on this heat effect. Much has been accom- 

 plished by Thomsen, Berthelot and others who have derived 

 the heat of formation of salts from the observed heat of neu- 

 tralization in solution — a method not applicable in all cases 

 to salts which hydrolyse largely. The reaction with sodium 

 peroxide avoids errors due to hydrolysis and gives fairly accu- 

 rate results, as shown in a previous paper* in which 2Na a O a ,C a 

 = 133500 c was the observed heat and 132500° that derived from 

 Thomsen's data. As a test of the method two determinations 

 were made and in each rather more than two grams of rhom- 

 bic sulphur were burned in a bomb with an excess of sodium 

 peroxide. The heat effect for one gram was 5275 c and 5267 c 

 respectively ; mean 5271° and for 32 grams of sulphur, 168670°. 

 The heat effect of Na 2 0, S0 3 is derived thus : — 



3Na 2 O a , S — 168700° 

 3Na n O , 30 = 58200° 



Na 2 , S , 30 = 226900° 

 S , 30 = • 103200°f 



Na 2 , SO a = 123700° 



From Thomsen's data we have 



2Na , S , 40 = 328590° 



2Na , O = 99760°}; 



S , 30 = 103200° 



Na 2 , S0 3 = 125630° 



Thomsen used Beketoff's result for 2Na , O ; deForcrand§ 

 considers it too high and that 91000° is probably more accu- 

 rate. The calculated heat effect of Na 2 , S0 3 will not be 

 changed by using this number. 



S. W. Parr|| mentioned that oxygen is sometimes liberated in 

 combustion with sodium peroxide and the writer has found 



* This Journal, xxiv, 134. 



f Thomsen, Thermoehemische Untersuchungen, ii, 254. 

 % Ibid., iii, 232. § 0. R., cxxvii, 1449. 



1 J. Am. Chem. Soc, xxix, 1606. 



