PRINCIPLES OF COMBUSTION. 141 



Carbonic acid. 



Thus, as far as the carbon is concerned, we obtain the infor- 

 mation we sought, namely, its saturating equivalent of oxygen, 

 and which we find to be just double its own volume ; or, by 

 weight, as 16 is to 6. But, without the aid of chemistry, we 

 should here have remained satisfied ; combustion would appear 

 to have been complete ; there would be no smoke, and no visi- 

 ble indication of an imperfect or unfinished process. Yet, chem- 

 istry tells us, we have only disposed of the one. constituent of 

 the gas, namely, the carbon, and that the hydrogen, the second 

 constituent, remains yet to be accounted for, and converted to 

 heating purposes. * 



It is true, the carbon was, in weight, equal to six parts out of 

 eight (the original weight of the gas.) In bulk, however, it was 

 but one fifth; and when it is recollected, that, although the 

 illuminating properties of the carbon are superior to those of the 

 hydrogen, yet that the heating properties of the hydrogen are 

 far superior to those of the carbon, we can appreciate the loss sus- 

 tained should these four fifths of the gas remain unconsumed. 



To this may be added, the probable injury done to the heat- 

 ing powers of the flame by the conversion of any part of this 

 otherwise valuable hydrogen into one of the most destructive 

 compounds which can be met with in the furnace or flues, 



* I have here stated the case of the oxygen uniting with the carbon, 

 before the hydrogen. Chemists are undecided on this point ; and, indeed, 

 the evidence at present is quite contradictory. 



It is to be observed, however, that the argument, drawn from the 

 combustion of the carbon before the hydrogen, or vice versa, is the same, 

 as regards the point now under consideration. Whichever half passes 

 off uncombined, is lost. 



