OF THE MANUFACTUBE OF GAS. • 109 



The foregoing experiments give us a much more complete 

 insight into this process of gas making than did the previous 

 ones on resin gas; and they also bring to light several circum- 

 stances highly favourable to it, which could scarcely have 

 been predicted previous to the actual trials being made. The 

 first and most important of these is the disappearance of the 

 carbonic acid contained in the water gas during its passage 

 through the coal retort. This disappearance is so complete 

 that the resulting gaseous mixture actually contains a much 

 smaller percentage than does the gas obtained by the distilla- 

 tion of the coal alone. It is true that the gases examined in 

 the above experiments had streamed through small wet and 

 dry lime purifiers ; but I have shown that in the production 

 of gas from resin, lime \fras almost useless for removing car- 

 bonic acid in these purifiers, and that, even when charged with 

 caustic soda, they still left 3.59 per cent, in the gas. It is 

 therefore certain, that the carbonic acid of the water gas is de- 

 stroyed by some action taking place during its passage through 

 the coal retort ; thus obviating all trouble and expense of 

 removing this gas by any purifying process whatever. There 

 is little doubt that this removal of the carbonic acid depends 

 upon its conversion into carbonic oxide gas by the carbon- 

 aceous matters in the coal retort ; and of these the coke is 

 probably the most active, since the volatile matters do not 

 differ materially from those produced during the distillation 

 of resin; and these, we have seen, fail to remove the acid gas* 



Another favourable circumstance occurring in the process 

 consists in the relatively small quantity of carbonic oxide that 

 is produced ; a large proportion of this gas would be equally 

 objectionable with a high per centage of light carburetted 

 hydrogen, so far as the quantity of carbonic acid formed 

 during its subsequent combustion is concerned; a reference 

 to the composition of the foregoing gases shows us, however, 

 that in all cases the amount of carbonic acid generated is less 

 than that formed by the combustion of an equal volume of 



