92 THE PRODUCTION AND USE OF HEAT 



It is evident that one can not blow hard enough on the char- 

 coal to scatter the particles as the gas particles are scattered 

 and thus stop the burning. Rather, the blowing serves to 

 bring in fresh oxygen and to remove the carbon dioxide result- 

 ing from the burning thus favoring the burning. 



104. Luminous and Non-luminous Flames. It will be 

 recalled that the flames of the candle, of the kerosene lamp, of 

 acetylene and of the burning wood are yellow or red in color 

 and give much light. Such flames are said to be LUMINOUS. 

 The hydrogen flame, the gasoline flame as commonly used in 

 stoves, and the illuminating gas flame as used in stoves are 

 blue. Such flames are said to be NON-LUMINOUS. It will be 

 recalled that the non-luminous gasoline flame was made 

 to give light by placing a mantle around it (Art. 42). The 

 heat of the flame caused the mantle to become very hot 

 and thus to give light. The light producing ability of the 

 flames of the candle, of kerosene, of acetylene, and of wood is 

 due to the presence of red- or white-hot particles of carbon. 

 The carbon has been separated from the fuel burned by the 

 action of the heat on certain compounds in the fuel. This 

 carbon is heated by the burning of other elements in the fuel 

 and thus gives light. The carbon finally meets oxygen and it 

 too burns liberating heat. If anything interferes with the 

 burning of the carbon, a black smoke composed of unburned 

 carbon particles results. 



105. Incomplete Combustion. 



Exercise 31. Causing a Flame to Smoke 



Light a candle flame. Can you see any unburned carbon escaping 

 from the flame? Now introduce some cold object, as a glass tum- 

 bler, into the flame. What is the result? What do you find is being 

 deposited upon the cold surface? Why did it not burn? 



Light a kerosene lamp and replace the chimney. Turn the wick 

 higher until the lamp smokes. What is the smoke? Why does not 

 this smoke burn? Why does not the flame smoke when the wick is 

 turned lower as it should be (Art. 8, Ex. 4)? 



DISCUSSION OF EXERCISE 31. The fuels burned in the 

 above exercise were hydrocarbons. We have just seen that 



