PRELIMINARY EXPERIMENTS XXV 



loop be left long enough in the air, it will become cloudy. 

 The reason it clouds so quickly when the candle is being 

 burned is that a large amount of CO 2 is formed. Besides 

 being made by real flames, CO 2 is formed every time we 

 breathe out air. Renew the film of water in the loop and 

 breathe against it gently for two or three minutes. 



The presence of CO 2 in the breath may be shown better 

 by pouring off some of the clear limewater into a clean 

 glass and blowing into it through a straw. 



Why does water put out a fire? The answer is, not 

 alone because it wets and shuts off the supply of free 

 oxygen, but because it cools the carbon, which must be 

 hot in order to unite with the oxygen, and prevents the 

 oxygen of the air from getting as near the carbon as 

 before. 



