S30 Di\ T. Andrews oji the Heat disengaged during the 



certain portion of carbon (which, notwithstanding the great 

 excess of oxygen, always escaped combustion), remained in the 

 platina dish after each experiment. By deducting the weight 

 of this residue from that of the carbon originally taken, the 

 weight of the carbon consumed was immediately obtained. 

 To obtain witii accuracy the weight of the charcoal, it was 

 introduced in the state of fine powder into the platina cup 

 already referred to; and after being heated nearly to ignition, 

 the latter was enclosed in a copper box, which, when covered 

 by its lid, communicated with the external air only by a very 

 small aperture. The whole was then allowed to cool in vacuo 

 over sulphuric acid ; and when cold, a stream of dry air was 

 admitted into the receiver. The aperture in the lid being 

 now closed, the weight of the entire was determined. 



To obtain complete combustion, a very large excess of 

 oxygen was employed; but even with this precaution, car- 

 bonic oxide was discovered in the residual gas in several of 

 the following experiments. 



In the subsequent tables, M designates the weight of the 

 substance burned ; T, the temperature of the air, and the other 

 letters the same quantities as before. 



We have, therefore, for the heat evolved during the com- 

 bination of — 



One gramme carbon with oxygen . 7678 

 One gramme oxygen with carbon . 2879 

 One litre oxygen with carbon . . . 4137 



