300 COMBUSTION OP CHARCOAL 



X. 



Observations on the Combustion of several Sorts of Charcoal, 

 and on Hidrogen Gas: by Theodore de Saussure. 



(Concluded from p. 1 76.) 



Combustion of plumbago from Cornwall. 



Plumbagofr©m J^ Burned in oxigen gas 0*588 of a gramme [9*079 grs.] of 

 taming 0*04 of plumbago dried at a red heat. The combustion continued 

 iron, burned i» an hour, and left as a residuum 033 of a gr. [0*51 of a 

 gr.] of red oxide of iron. This compound, which is formed 

 during the operation*, would consist, according to Bu- 

 choizf, of 0'0231 of a gr. [0*357 of a gr.] of iron, and 

 0*0099 of a gr- [0*153 of a gr.l of oxigen. One hundred 

 parts of this plumbago therefore contain 4 parts of iron ; 

 and I burned 0*588 — 0*0231 =0*5649 of a gr. [8722 grs.] 

 of carbon. 

 Reiulu. The gas contained in the receiver occupied in the shade, 



previous to the combustion 1894*3 cent. cub. [1153*5 cub, 

 inch.]; thermom. at 23*12° [73*62° F.]; barometer, re- 

 duced to the temp, of 12*6° [54*5° F.J, 0*7329 of a met. 

 [28*83 inch.]. 



Two hours after the combustion the gas occupied 1899*3 

 cent. cub. [1156-57 cub. inch.]; thermom. at 25° [77° F.]; 

 barom. corrected at 0*7329 of a met. [28*83 inch.]. 



Reducing the volumes of gas, before and after combus- 

 tion, to the mean temperature of 12*5° [54*5° F.], and pres- 

 sure 075796 of a met. [29*82 inch.], we find that the gas 

 occupied, 



Before combustion, 1758*8 cent. cub. = 1071*022 cub. inch. 

 After combustion, 1750*4 ZZ 1065*907 



Diminution, •••••• 8*4 = 5*115 



* Messrs. Allen and Pepys, in making the same experiment, consi- 

 der the oxide of iron as completely formed in the phnnbago before the 

 combustion. This must occasion some slight difference in the results 

 of their operation. 



t Ann. de Chini. vol. LXV, p. 202 : or Journal, vol. XXV, p. 35.1. 



The 



