90 THE PRODUCTION AND USE OF HEAT 



removed, is called WOOD CHARCOAL. Place it on the edge of the 

 gauze so that the end of the stick of charcoal extends beyond the 

 gauze and heat the charcoal strongly by means of a flame. Does 

 the charcoal get red hot? Does it burn after the flame is removed? 

 Does the charcoal burn with a flame? Does it give off much 

 heat? Do you find any ash remaining after the charcoal has 

 burned? The glowing embers of a wood fire are due to the burning 

 of the wood charcoal after the volatile matter has been removed 

 and burned. 



Caution. Be sure to quench the glowing charcoal lying on the gauze 

 by throwing it into water. If left, it might set fire to the building. 



FIG. 69. Burning wood FIG. 70. Distillation of wood, 



on gauze. 



Exercise 29. The Distillation of Wood 



Select a piece of wood about 1 in. long and of such a size as will slip 

 into a test tube. Close the test tube with a one-hole stopper through 

 which passes a short glass tube (Fig. 70). Heat the test tube as shown 

 in the figure, carefully observing what takes place. Does smoke 

 appear? Try lighting it as it comes from the small tube. Does 

 liquid appear in the tube? Keep the tube inclined so that the liquid 

 will stay near the stopper. If you allow it to run back and meet the 

 hot glass it will probably break the tube. When the wood ceases to 

 give off smoke, cool the tube, remove the stopper and pour the liquid 

 into a shallow vessel. What is its color, odor, and appearance? 



101. Discussion of the Exercise. The liquid distilled from 

 the wood is known as PYROLIGNEOUS (pi-ro-lig'-ne-us) ACID 

 (pyro meaning fire, and ligneous meaning woody). It is, 

 therefore, acid obtained from woody substances by means of 

 fire. It is composed largely of water but it also contains 

 acetic acid (the acid of vinegar) and wood alcohol and other 

 substances of commercial value. When wood is burned in a 

 stove or grate these substances, except the water, together 



