134 Mixter — Combustion of Silicon and Silicon Carbide. 



Minutes. Temperature. Temperature interval. 



18-126 21-836— 18-132 + 0-013=3'Vl7° 



1 18-1-28 



2 18-132 Heat observed 3432-8x3-7i7=12760 c 



8 21-836 " of oxidation of iron — 85 c 



9 21-832 



10 21-829 12675 c 



11 21-827 



12 21-825 For 1 gram of silicon carbide 91 10 C 



13 21-923 



The results of the combustions with sodium peroxide are as 

 follows for 1 gram of each substance : 



Acetylene Crystalline Silicon 



carbon silicon carbide 



11 103 c 8342 c 9156 c 



11149° 8379 c 9110 c 



Mean 11126° 8360 c 9133° 



For 12 grams of acetylene carbon 1335 12 c 



it 28-4 " '■' crystalline silicon 237424° 



370936° 

 For 40-4 grams of silicon carbide -- 368973° 



Difference 1963° 



The above results indicate that the formation of silicon 

 carbide is accompanied with but little thermal change. The 

 heat of combustion of the diamond according to Favre and 

 Silbermann is 93240°, 14S8° less than that of acetylene carbon in 

 oxygen; assuming, if the diamond had been burned with 

 sodium peroxide, that the result would have been 1488° less, we 

 have 515° for the heat of formation of silicon carbide from 

 the diamond and crystalline silicon. 



Using Thomsen's* data for the union of sodium oxide and car- 

 bon dioxide, deForcraud'sf for the heat of formation of sodium 

 peroxide from the oxide, and the heat of combustion of acety- 

 lene carbon, the thermal effect of carbon and sodium peroxide 

 may be calculated thus : 



Na,0, CO„ = 75920° 



C, 2 = 94728° 



170648° 

 2Na„0— 0„ = —38380° 



2Na 2 2 , C = 132268° 



* Thermochemische Untersucben iii, 2c 

 |C. E. cxxvii, 514. 



