GAS, COAL 



541 



Cannel (Boghead) 



Cannel (Wigan) 



Coal . 



Oil ( . 



Resin . ..>_ 



Peat . -. .' 



Wood . 



Percentage of 

 Carbon 



80-35 

 85-95 

 88-15 

 78-90 

 79-47 

 60-41 

 50-00 



Percentage of 

 Hydrogen 



11-21 

 5-75 

 5-26 



10-97 

 9-93 

 5-57 

 5-55 



Percentage of 

 Oxygen 



6-71 



8-14 



6-41 



10-13 



10-59 



34-02 



44-45 



In addition to the three essential constituents above mentioned most of these mate- 

 rials contain small and variable proportions of sulphur, nitrogen, and inorganic 

 matter, the latter constituting, when the substance is burnt, what we term ash. When 

 these substances are heated to redness, they undergo decomposition, a considerable 

 quantity of inflammable gases and vapours being evolved, whilst a residue, consisting 

 of carbon, or of carbon and ash, remains behind in the solid form. When atmospheric 

 air has free access during this heating operation, the inflammable gases and vapours 

 burn with a more or less bright flame, as in a common fire ; whilst the carbonaceous 

 residue continues afterwards to glow, until nearly the whole of the carbon is consumed. 

 If, however, the application of heat be made without access of air, by inclosing the 

 materials for instance in an iron retort provided only with an outlet for the escape 

 of gases, the decomposition goes on in much the same manner as before, hut the 

 various products formed, being no longer exposed to the simultaneous action of 

 atmospheric oxygen, do not undergo combustion ; the inflammable gases and vapours 

 are evolved through the outlet pipe in an unburnt condition, and the carbonaceous 

 residue also remains unconsumed in the retort. Upon cooling the gases and vapours 

 thus evolved, the latter condense more or less into liquids which separate into two 

 layers, the lower one forming a dense black oily fluid, commonly known as tar, and 

 containing several solid hydrocarbons partly in solution and partly in suspension ; 

 whilst the other one consists chiefly of an aqueous solution of salts of ammonia, if the 

 organic matters operated upon contained nitrogen. Thus the volatile products of this 

 process of destructive distillation consist of solids, liquids, and gases. These consti- 

 tuents may be thus tabulated : 



I. GASEOUS. 



Name Chemical formulas 



Hydrogen ....... H H 



Light carburetted hydrogen .... C 2 H 4 CH 4 



Acetylene C 4 H 2 C 2 H 2 



Carbonic oxide CO CO 



Olefiantgas C 4 H 4 C 2 H 4 



Propylene . C 6 H 6 C 3 H S 



Butylene C R H 8 C 4 H 8 



Carbonic acid CO 2 CO 2 



Sulphuretted hydrogen SH SH 2 



Nitrogen N HT 



II. LIQUID. 



Name Chemical formate 



Aqueous layer : Water HO H 2 O 



Oily layer : Bisulphide of carbon .... CS 8 CS 2 



Benzol C 12 H C G H" 



Toluol C 14 H 8 C 7 H 8 



Cumol C 18 H 12 



Cymol C 20 H 14 



Aniline . ... C 12 H 7 N 



Picoline C I2 H 7 N C'HTO 



Leucoline C t8 H 8 N CH 8 W 



Carbolic acid (Phenol) . . . C 12 H 6 3 C H O 



Other hydrocarbons . . . . C n H n * 



ti >i > .... C n H n _ 6 



Here n means an even number, as 2, 4, 6, &c 



