OF THE MANUFACTURE OF GAS. 



87 



perform their work very imperfectly, compared with the 

 water gas. 



The generation of water gas free from carbonic acid, 

 although of no consequence in the process applied to coals 

 and cannels, is a problem of great importance in its applica- 

 tion to resin. The relative quantity of this gas produced 

 varies so considerably, (from 10*78 to 4*72 per cent.,) owing 

 no doubt to the degree of heat at which the decomposition 

 takes place, and also probably to the rapidity with which 

 the water is admitted into the retorts, that it is not impossible, 

 by varying the condition, to get rid of it altogether. Its 

 quantity appears to decrease as the temperature increases, 

 but I have hitherto been unable entirely to prevent its for- 

 mation. It is therefore requisite to have an efficient means 

 for removing it from the gaseous mixture before it arrives at 

 the holder, since this gas is not only entirely useless, being 

 perfectly incombustible, but has a decidedly injurious influence 

 on the combustion of the gas, by cooling the flame, and thus 

 greatly diminishing the illuminating power. Lime, both in 

 its wet and dry state, is quite inefficient for the removal of 

 this carbonic acid, since the carbonate of lime first formed 

 prevents further contact between the gas and the purifying 

 agent. I therefore recommend caustic soda, produced by 

 mixing lime with a solution of common soda, as a most 

 efficient and inexpensive purifying agent when applied in the 

 following manner : — Let 1 cwt. of soda be dissolved in not 

 less than 120 gallons of water, (and proportionately for smaller 

 quantities ;) add to this 70 or 80 lbs. of quick lime ; mix the 

 whole well together and transfer it to the purifier, where it 

 should be occasionally well agitated ; after about 8000 cubic 

 feet of gas have passed through, the mixture should be run oif 

 and allowed to settle in a suitable tank, from which the clear 

 liquor floating above the sediment of carbonate of lim.e must 

 be pumped up into the supply tank for the purifier, and. 



