Mixter — Combustion of Silicon and Silicon Carbide. 137 



Experiment 11. 



Silicon carbide . 1-0130 grams. 



" " in residue ... 0-0984 " 



Silicon " " 0-0089 



Silicon carbide burned 0-9057 " 



Carbon 11220 " 



Iron for ignition. 0-0530 " 



Oxygen - 11" " 



Water and water equivalent of system. 3387-5 " 



Temperature interval. 

 22-573 — 18-314 + 0-012 = 4-271° 



Heat observed 15322 c 



of oxidation of iron — 85 c 



" " " carbon — 885 7 C 



Minutes. 



Temperature, 







18-308 



1 



18-311 



2 



18-314 I 



7 



22-573 



8 



22-571 



9 



22-567 



10 



22-563 



11 



22-561 



" " " silicon carbide 6380° 



For 1 gram of silicon carbide 7044 u 



If the weight of carbide equivalent to the free silicon left by 

 a combustion be deducted from the amount of carbide taken 

 for an experiment, and the carbon equivalent to the free sili- 

 con be added to that taken, the results calculated on this basis 

 will be essentially the same as those given. The following 

 table shows the proportions of silicon carbide and free silicon 

 remaining after the combustions: 









Silicon carbide. 



Silicon. 



Experiment 



, 7 



7057° 



18 per 



cent. 



- 7 per cent. 



(( 



8 



6659 



25 " 



u 



3 " " 



cc 



9 



6963 



20 " 



cc 



" " 



a 



10 



6882 



33 " 



cc 



3-8 " " 



cc 



11 



7044 



10 " 



cc 



Q.g a cc 



It was found in the work on silicon that where the products 

 of combustion contain much free silicon there is a variable 

 error. For this reason the figures of experiments 8 and 10 

 should not be included in the final result. The mean of the 

 other three experiments is 7009 calories for the heat of combus- 

 tion of 1 gram of silicon carbide in oxygen at 20°. For 40"4: 

 grams it is 282164 calories at constant volume and 283750 cal- 

 ories at constant pressure. 



