CARBON DIOXIDE 



55 



Charcoal and Coke are made on the same principle, 

 namely, by heating coal, wood, or bones in an oven or 

 any place to which air does not have free access. This 

 prevents enough oxygen from getting to the burning 

 substance to permit complete or perfect oxidation. But 

 the heat produced will nevertheless drive out the water 

 and some gases and leave the coke and charcoal. 



Wood charcoal used to be made by cutting the wood 

 in lengths of about four or five feet and then making a 



WOOD ARRANGED FOR BURNING INTO CHARCOAL 



stack of this by standing it on end and covering it with 

 earth about a foot deep. An opening was left at the 

 top for the gases to escape. It was permitted to burn 

 for a day or two and then the fire was put out by 

 closing all openings by which air could enter or smoke 

 escape. This would extinguish the fire, because burning 

 cannot continue without oxygen and the escape of carbon 

 dioxide. After the fire was out the earth covering was 

 removed and the wood charcoal was ready for market. 



A large percentage of the soft coal mined in Pennsyl- 

 vania and neighboring states is made into coke. Long 

 double rows of brick coke-ovens are made and filled with 

 coal. An opening about one foot in diameter is left at 



