140 Minster — Combustion of Silicon and Silicon Carbide. 



after dissolving the fused mass in a large volume of cold water. 

 The mean of two results which agreed closely was 71000 c for one 

 molecule of silicon dioxide. The difference of 13000 c between 

 the calculated and observed result is due either to an error of 5 

 per cent in the heat of oxidation of silicon or to the formation 

 of a mixture of silicates in the experiments with silica. In the 

 latter instance the conditions are less favorable to the forma- 

 tion of only the orthosilicate. Hence we may consider that 

 84000° deduced from the reaction of silicon with sodium per- 

 oxide is the better result. 



Summary of results. 



SiC, 20 2 = 283800° 



Si crystalline, C amorphous = 2000 



Si " , 0„ = 191000° 



2Na„0, Si0 2 amorphous = 84000° 



The figures given for the heat effect of the union of silicon 

 and carbon are too small to indicate more than this, namely,, 

 that the formation of silicon carbide from its elements is accom- 

 panied with very small evolution or absorption of heat. 



