SAVING FUEL 75 



Open the holes. The flame ceases to smoke. Place a wire in it. 

 It heats quickly. Regulate the sizes of the openings until the 

 greatest possible heat is obtained. 



(6) By means of a ringstand hold a wire gauze two or three 

 inches above a Bunsen burner. Turn on the gas and apply a 

 lighted match above the gauze. The gas above the gauze will 

 take fire, but that below will not. (Figure 33.) Turn off the gas and 

 then turn it on again. Now light the gas below the gauze. The 

 gas above the gauze does not ignite. The gauze conducted the heat 

 off so rapidly into the surrounding air that the gas 

 on the side of the gauze away from the flame was 

 not raised to its kindling temperature and so did 

 not burn. 



In Experiment 25 it was found that if the 

 holes at the bottom of a Bunsen burner are 

 closed so that an abundant supply of air 

 (that is, of oxygen in the air) is not mixed FIGURE 33 

 with the gas, the burner smokes. When 

 these holes are regulated so that the right amount of air is 

 supplied, there is a hot flame and no smoke. It was found 

 in the second part of the experiment that gas would not 

 burn unless it was raised to its kindling temperature. This 

 illustrates what happens, to a greater or less extent, in all 

 stoves and furnaces especially where soft coal is burned. 



Every one knows that when a fresh supply of soft coal is 

 thrown upon a fire, it smokes. This is because the fresh 

 coal acts as a blanket. It decreases the supply of fresh 

 air from below, and lowers the temperature in the upper 

 part of the stove or furnace. Not all the gases from the 

 coal that are driven off by the heat below are burned where 

 they are formed, because the blanket of coal has cut down' 

 the draft and thus lowered the supply of oxygen. 



These light gases rise, therefore, into the upper part of 



