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CONTRIBUTIONS TO THE KNOWLEDGE 



being again mixed with the same quantity of lime, used as 

 before. Thus little or no loss of soda occurs, this base being 

 simply used as a carrier of the carbonic acid from the gas to 

 the lime. The sediment of carbonate of lime may be thrown 

 away between each operation. The cost of purification by 

 this method would not exceed ^d. per 1000 cubic feet. 



The 4th experiment was made with the purifier charged in 

 the manner described, except that only 75 lbs. of soda were 

 employed. The result of this experiment shows^ that whilst 

 the whole of the carbonic acid can be readily removed by this 

 method, if the caustic soda be employed in sufficient quan- 

 tity, and the gas brought in contact with a large surface of it, 

 the quality of the gas is not in the least deteriorated in its 

 passage through the liquid, as is proved by the increased per 

 centage of olefiant gas. 



A distinction must be made between unpurified coal gas 

 and unpurified resin gas. The former contains many delete- 

 rious ingredients, which entirely prevent its use; the latter 

 does not contain any noxious principle, but simply has its 

 illuminating power diminished by the presence of carbonic 

 acid. Its purity of composition and freedom from all sub- 

 stances which can, during combustion, produce compounds 

 injurious to furniture, drapery goods, &c., gives the resin gas 

 great advantages over coal gas, which always contains more 

 or less bisulphuret of carbon, — which has hitherto defied all 

 attempts to remove it or diminish its quantity by any process 

 of purification — and which, during combustion, generates 

 sulphurous acid, the compound to which all the mischief 

 produced by coal is probably owing. The odour of the hydro- 

 carbon gas, while it is sufficiently strong to give warning of 

 any escape, is far less nauseous than that of the coal gas, and 

 might even by some persons be deemed pleasant ; whilst the 

 process of manufacture is so simple, that any person of mode- 

 rate intellect can at once conduct it. 



