ATTENDING THE FORMATION OF COAL, &c. 265 



gen as above ; part with oxygqn, forming carbonic acid and 

 carbonic oxide ; part with nitrogen, forming cyanogen ; 

 part with sulphur, forming sulphuret of carbon. So that 

 there is a perfect division of the elements amongst each 

 other; and it can never be that the whole of the hydrogen 

 shall unite with the carbon, and produce illuminating gases 

 only. Here, however, we have no actual or necessary pro- 

 duction of hydrogen, whose presence in the gas, therefore, 

 must be the result of a defect in the process of gas-making. 

 A little chlorine also is present in most canncls in the form 

 of chlorine salts, and is given off as muriatic acid, but al- 

 ways in combination with the ammonia. A little sulphu- 

 rous acid is likewise found in combination with the am- 

 monia. The muriatic and sulphurous acids never pass 

 into the gas holder, and need not be considered, being con- 

 densed with the ammonia. The cyanogen, sulphuretted 

 hydrogen, ammonia, and carbonic acid, constituting a very 

 minute proportion of the whole gas, ought to be all removed 

 in the process of purification ; so that there remain as con- 

 stant ingredients of the gas, as at present manufactured, 

 hydrogen, light carburetted hydrogen, olefiant gas, volatile 

 hydro-carbons, carbonic oxide, and a little nitrogen ; and of 

 these, the olefiant gas, volatile hydro-carbons, and light car- 

 buretted hydrogen, alone contribute to illumination. The 

 water formed and condensed from the distillation (gas water, 

 ammonia water), retains in solution carbonate, sulphite, 

 muriate, hydro-sulphate, and prussiate of ammonia ; the 

 tar which condenses from the distillation, consists of nume- 

 rous oils, called naphtha, heavy oil of tar, &c., composed 

 almost entirely of carbon and hydrogen. 



I add here a tabular view of the products of the distillation 

 of coal, with the composition of each. 



2 M 



