ANALYSIS OF GASEOUS MIXTURES. 303 



generally employed in the analysis of our own gas, and 

 that of the neighbouring towns. In this process, the rela- 

 tive value of the different gases is determined by the quan- 

 tity of oxygen required to effect the complete combustion 

 of the gas. This is done by firing the mixed gases by elec- 

 tricity in graduated tubes, and calculating the oxygen con- 

 sumed in the production of carbonic acid and water from 

 the gas. 



By a combination of these two methods I have arranged 

 a plan of analysis, by which the general value as well as the 

 constitution of any coal gas can be determined with accu- 

 racy, and the illuminating gases can receive an expression 

 sufficiently high to indicate even small amounts of differ- 

 ences in their proportions. 



I first determine, by an analysis with oxygen alone, the 

 number of volumes of oxygen required for complete com- 

 bustion, by 100 volumes of the gas to be examined, and 

 the quantity of carbonic acid produced; I then, from 

 another portion of the same gas, withdraw the olefiant 

 and other illuminating gases by fuming sulphuric acid, and 

 determine the exact amount of these ; I then subject a por- 

 tion of the residual gas to examination with oxygen again, 

 and determine the number of volumes required ; the differ- 

 ence in the two examinations gives the amount of oxygen 

 required by the illuminating gases removed by the sulphuric 

 acid, and of carbonic acid produced. In the second portion 

 of the residual gas I determine the quantity of each con- 

 stituent gas, and estimate the amount of each in the whole 

 mixture. 



This is accomplished in the way generally practised, viz., 

 by exploding the residual gas with oxygen, determining the 

 amount of oxygen consumed, and of carbonic acid produced; 

 and from these data, calculating the proportions of light car- 

 buretted hydrogen, hydrogen, carbonic oxide, and nitrogen. 



