ACIDIFIABLE COMBUSTIBLES. 



of water. Hence, the specific gravity of ether 

 vapour is 2*569i ; for it consists of 



1 volume of quadro-carburetted hydrogen 1 '9444 

 1 volume of vapour ef water . . 0-6250 



2-5694 = sp. gr. 

 of ether vapour. 



Fifth s P e. The fifth consists of 



ClCSt 



6 volumes carbon vapour ^ 



~ T , , > condensed into 1 volume. 



6 volumes hydrogen gas J 



Its specific gravity is 2*9166. It requires nine 

 times its volume of oxygen gas to consume it 

 completely : and when 1 volume of it is con- 

 sumed in this way, there remain behind 6 vol- 

 umes of carbonic acid gas as a residue. 



I find, that the vapour of naphtha, from coal, 

 constitutes a gaseous compound of this kind. It 

 is not condensed by passing it through water ; 

 and is, I believe, what gives coal gas its peculiar 

 smell. 



These gaseous bodies are chiefly used for 

 lighting the streets and illuminating houses. 

 Now, it is obvious, that the quantity of light 

 which they will emit while burning, will be pro- 

 portional to the number of volumes of carbon 

 condensed into 1 volume of the gas. Olefiant 

 gas burns with great brilliancy ; but the vapour 

 of naphtha will give three times as much light, 



