144 HEATING. 



No facts in chemistry, therefore, can be more decidedly 

 proved, than that one atom of hydrogen and one atom of 

 oxygen (the former being double the bulk of the latter) unite in 

 the formation of water; and, further, that one atom of carbon 

 vapor and two atoms of oxygen (the latter being double the bulk 

 of the former) unite in the formation of carbonic acid gas. 



Thus, the ultimate fact of which we were in search is, that 

 the one condensed volume of the gas, as generated from the 

 coal, requires two volumes, or double its bulk of oxygen, that 

 being the quantity required for the saturation of its constituents 

 when separated. 



Now, this is the entire alphabet of the combustion of the car- 

 buretted hydrogen gas. 



Having thus ascertained the quantity of oxygen required for 

 the saturation and combustion of the two constituents of coal 

 gas, the only remaining point to be decided is, the quantity of 

 air that will be required to supply this quantity of oxygen. 



This is easily ascertained, seeing that we know precisely the 

 proportion which oxygen bears, in volume, to that of the air. 

 For, as the oxygen is but one-fifth of the bulk of the air,^ne 

 volumes of the latter will necessarily be required to produce one 

 of the former ; and, as we want tivo volumes of oxygen for each 

 volume of the coal gas, it follows, that to obtain those two vol- 

 umes, we must provide ten volumes of air. 



Thus, then, by strict chemical proof, we have obtained these 

 facts : First, that each volume of coal gas requires two vol- 

 umes of oxygen ; secondly, that to obtain these two volumes of 

 oxygen we must employ eight atoms of air ; thirdly, that these 

 eight atoms of air are equal to ten volumes of the coal gas ; 

 each volume of the latter, in fact, requiring ten volumes, or ten 

 times its bulk of air : thus, 



Ten volumes of air are the same as eight atoms ; 



Eight atoms of air produce four atoms of oxygen ; 



Four atoms of oxygen are equal to two volumes of the same ; and 



Two volumes of oxygen saturate one volume of the coal gas : 



Therefore, ten volumes of air are required for each one volume of this gas. 



We now see why ten volumes of air are required for each 



