OF THK MANUFACTURE OF GAS. 



83 



amount of hydrocarbons; 2nd, The volume of carbonic acid 

 generated by hydrocarbons, plus the volume of the same gas 

 produced by the non-luminiferous gases; and 3rd, The 

 volume of carbonic acid generated by the non-luminous 

 gases alone. From these data it is easy to calculate the 

 amount of carbonic acid generated by one volume of the 

 hydrocarbons. Thus, if we represent the per centage of 

 hydrocarbons absorbed by sulphuric acid by A., the volume 

 of carbonic acid generated by 100 vols, of the original gas by 

 B., the carbonic acid formed by the gas remaining after the 

 absorption of hydrocarbons from 100 vols, of original gas by 

 C, and the volume of carbonic acid generated by the com- 

 bustion of the hydrocarbons alone by x, we have the follow- 

 ing equation — 



x—c — b ; 



and therefore the amount of carbonic acid generated by 1 



c b 



vol. of the hydrocarbons is represented by — ^ — , but as 1 vol. 



A. 



of carbon vapour generates 1 vol. of carbonic acid, this 



fraction also expresses the quantity of carbon vapour in 1 



vol. of the luminiferous constituents. For the purpose of 



comparison, however, I prefer to represent the value of 



these hydrocarbons in their equivalent volume of olefiant gas, 



1 vol. of which contains 2 vols, of carbon vapour ; to effect 



this the last expression need only be changed to ^r— ^ Thus 



if there exist in a specimen of gas 10 per cent, of hydro- 

 carbons, one volume of which contains 3 vols, of carbon 

 vapour, the quantity of olefiant gas to which this 10 per cent, 

 is equivalent will be 15. 



The necessity for this valuation will be evident when I 

 state that one volume of the hydrocarbons absorbable by 

 chlorine, or fuming sulphuric acid, (for both these materials 

 condense precisely the same ingredients if light be perfectly 

 excluded during the action of the chlorine,) contains quanti- 



