HEAT FROM COMBUSTION 59 



incomplete. By complete combustion is meant that all 

 of the material has been burned and none wasted. This 

 can be accomplished by giving the fire a proper amount 

 of air. Did you ever see heavy, black smoke coming out 

 a chimney? That smoke was part of the material which 

 should have been burned in the fire, and it meant a loss 

 to the one who was running the fire. The smoke showed 

 that there was incomplete combustion. If the com- 

 bustion had been complete there would have been no 

 visible smoke. 



There are other reasons, besides economy, why fires 

 should not be allowed to send off vast amounts of smoke. 

 The particles of smoke, called soot, slowly settle and spoil 

 the appearance of buildings, soil our linen, and affect our 

 health. It is very bad for us to breathe in smoke and 

 soot. In many cities it is against the law to allow chim- 

 neys to smoke to any unnecessary amount. 



Experiment 30. Complete and Incomplete Com- 

 bustion. 



Apparatus: Alcohol lamp filled with alcohol, alcohol 

 lamp filled with turpentine, Bunsen burner. 



Materials: Piece of broken chinaware, piece of iron 

 wire No. 28. 



a. Light the alcohol lamp. Is there 

 any smoke? Is the flame hot? Hold a 

 piece of fine iron wire in the flame and 

 notice how hot it becomes. Hold a piece 

 of chinaware in the flame. Does any- 

 thing collect upon it? 



b. Light the turpentine lamp. Is there any smoke? 



