244 ANNUAL OP SCIENTIFIC DISCOVERY. 



rules. In the usual process of gas manufacture there are generated, in 

 addition to these illuminating hydro-carbons, ten other classes of gaseous 

 constituents, impurities and diluents. With the exception of bisulphuret 

 of carbon and some organic compounds containing sulphur, all the impu- 

 rities are removed in the usual process of purification, which have now 

 been brought to great perfection ; but the presence of these sulphur com- 

 pounds in coal gas is very objectionable, and constitutes the chief barrier 

 to the universal employment of gas in dwelling-houses. The attention of 

 the manufacturer ought, therefore, now to be earnestly directed to the 

 discovery of means for preventing the formation of these compounds, as 

 it will probably be found impossible to remove them from the gas when 

 once they have been formed. In addition to traces of these sulphur com- 

 pounds, purified coal gas contains only the following ingredients : 



Olefiant gas, . . . C 2 II 2 



Propylene? C 3 H 3 



Butylene ? C 4 H 4 



10 



e 



. 



II 



Other hydrocarbons, . . . unknown. 



.2 j Light carburetted hydrogen, . C H 2 



;* t 



]$ S Hydrogen, H 



"** \ 



Q ( Carbonic oxide, ....CO 



The light emitted during the combustion of coal gas is due entirely to 

 the first or illuminating class of constituents, which yield an amount of 

 light proportional to the quantity of carbon contained in a given volume ; 

 thus, propylene and butylene yield respectively 50 and 100 per cent, more 

 light than olefiant gas, because they contain respectively 50 and 100 per 

 cent, more carbon in a given volume. It would not be desirable to employ 

 a gas containing only luminiferous ingredients, even if it were possible to 

 manufacture such a gas, because it is exceedingly difficult to consume 

 these constituents without the production of smoke attendant on imperfect 

 combustion. A diluting material is therefore necessary to give the flame 

 a sufficient volume, so as to separate the particles of carbon farther asunder, 

 and thus diminish the risk of their imperfect combustion. All the three 

 diluents above mentioned perform this office equally well; but if we study 

 their behavior during combustion, we shall find that in a sanatory point of 

 view hydrogen is greatly to be preferred. The two objections most fre- 

 quently urged against the use of gas in apartments are, first, the heat 

 whioti it communicates to the atmosphere ; and, second, the deterioration 

 of the air by the production of carbonic acid. Now, in their action upon 

 the atmosphere in which they are consumed, the above three diluents 

 present striking differences in these two respects. One cubic foot of light 

 carburetted hydrogen, at 60 F. and 30 in. barometrical pressure, consumes 

 two cubic feet of oxygen during its combustion, and generates one cubic 

 foot of carbonic acid, yielding a quantity of heat capable of heating 51 Ibs. 



