1819.] the different Species of Pit-Coal. 93 



By a train of reasoning precisely similar to that which was 

 followed in considering the products obtained from caking coal, 

 it may be shown that the number of atoms of each of these 

 constituents bear to each other the followincr ratios : 



© 



28 atoms carbon = 21-00 75-00 



14 atoms hydrogen. .. . = 1-75 6-25 



1 atom azote = 1-75 6*25 



3-1 atoms oxygen = 3-50 12*50 



28-00 100-00 



From the preceding table, we see that in splint coal (abstract- 

 ing the ashes) there is almost as great a quantity of carbon as in 

 caking coal ; yet the latter yields more coak than the former. 

 The reason of this apparent anomaly presents itself to our view 

 upon comparing the atoms of carbon and hydrogen in the two 

 species. In caking coal, the atoms of carbon are to those of 

 hydrogen as three to one. In splint coal as two to one. It is 

 this additional dose of hydrogen in the splint coal which enables 

 the heat to carry off a greater proportion of the carbon than in 

 caking coal, and of course reduces the weight of the coke. 

 Carbon itself is not volatile when heated ; it requires the pre- 

 sence of hydrogen to give it the gaseous state. 



3. Cherry Coal. 



This coal is decomposed with much greater facility than splint 

 coal, when heated along with peroxide of copper. Gas comes 

 over plentifully, though the heat to which it is raised scarcely 

 amounts to redness. 



From one grain of this coal treated in the usual way with 140 

 grains of peroxide of copper, I obtained the following gaseous 

 constituents reckoned under the medium pressure and tempera- 

 ture. 



Carbonic acid gas 5-27 cubic inches. 



Azotic gas 0*31 



The water evolved amounted to 0*9 gr. equivalent to 0- 1 gr. of 

 hydrogen. 



Hence the constituents of cherry coal are as follows : 



Carbon 0-666 



Hydrogen 0-100 



Azote 0-092 



Earth 0-100 



0-958 

 Oxygen 0-042 



1-000 

 These weights, when converted into atoms, become equiva- 

 lent to the numbers contained in the following table: 



