376 MB. JOHN £EIGH ON THE OHEMICAL CHANGES 



lbs. 



Gas...., 22| 



Tar..: 8i 



Ammonia wateT ...< 9| 



Coke 591 



100 

 These proportions will vary cc«isiderably, but still the 

 numbers will represent a general average of produce. It is 

 seen, from abOve, that considerably more than a third of the 

 weight of the gas produced, is distilled from the cannel iii 

 the form of tar, which contains, and is almost entirely 

 composed of, the richest carbo-hydrogen, and very little 

 oxygen ; whilst the gas, as it contains only about 45 per 

 cent, of compounds of carbon and hydrogen, by measure 

 amounting to about half its weight, really only contains 

 about 1 1 pounds of carbo-hydrogen, and of this only about 

 4 pounds will be defiant and richly illuminating gases. So 

 that in the tar is really contained as much illuminating 

 matter^ or nearly so, as in the gas — not twice as much as 

 would appear from the numbers ; for it must be borne in 

 mind, that in the oils composing the tat the carbon exists in 

 much greater proportion than the hydrogen, one of the 

 lightest, benzole, being a compound of carbon 12, hydrogen 

 6 ; naphthaline and the solid carburets being represented 

 by carbon 20, hydrogen 8, and even higher proportions of 

 carbon. So that, in the decomposition into illuminating gases, 

 much of the weight must be lost in the form of deposited 

 carbon. I think it is now tolerably apparent, that in the 

 form of distilled matters nearly one-half of the illuminating 

 matter derivable from coal and cannel is lost to the gas* 

 It is probable that a perfect system of gas-making would 

 produce from good cannel a gas containing 20 per cent, of 

 olefiant gas, or other illuminating gases. We have seen, 

 moreover, that a great waste of illuminating material takes 

 place in the present system, from the actual destruction of 

 illuminating gases when formed, by the large quantity of 



