ATTENDING THE FOKMATION OF COAL, fcc. 275 



hydrogen known, which at present is not, it would un- 

 doubtedly occupy the space of olefiant gas. In other words, 

 could olefiant gas, C. 4, H. 4, be resolved into 2 atoms of 

 C. 2, H. 2, i| would occupy double the space of the olefiant 

 gas itself. For olefiant gas itself occupies exactly the space 

 of the volatile hydro-carbon, C.8, H. 8; and it is ascertained, 

 as stated before, that when 1 volume of olefiant gas is passed 

 through a nearly white hot porcelain tube, it is certainly 

 decomposed, depositing all its carbon, and giving 2 volumes 

 of hydrogen. In other words, its bulk is doubled by the 

 decomposition; and 1 volume of the volatile hydro-carbon, 

 C. 8, H. 8, on being decomposed by heat, and depositing 

 carbon, forms 1 volume olefiant gas and 1 volume light 

 carburetted hydrogen zn to 2 volumes. 



One volume carbonic acid, on becoming converted into 

 carbonic oxide, occupies two volumes. 



The greater the heat employed, then, in the process of gas- 

 making, above a certain limit — viz., that requisite for the 

 decomposition of the liquid hydro-carbons — the greater 

 will be the bulk of the gas, and the poorer its quality; the 

 more light carburetted hydrogen, hydrogen, and carbonic 

 oxide it will contain, and the less volatile hydro-carbon and 

 olefiant gas. The analysis of the gas will therefore fur- 

 nish a test of the excellence of the process employed in the 

 manufacture, and a check on the workman, by exhibiting, 

 in the relative amounts of hydrogen, and of the illuminating 

 hydro-carbon, whether too great a heat has been employed. 

 A great quantity of gas may be made from coal, and very 

 badly made. The mere amount of gas produced is no proof 

 of the excellence of the manufacture. 



Cannel yielding 1 1,000 feet of gas per ton, of specific 

 gravity 600, would furnish for every 100 pounds distilled— 

 about 



