COMPOSITION OF AIR : ATOMIC THEORY 



57 



be burned. The part of the paper which is first burned forms 

 a ring corresponding to the position of the outer part of the 

 flame. The same tests may be carried out with the flame of 

 illuminating gas in a Bunsen burner. 



57. Products of the flame. When the gas formed from the 

 wax of the candle has been burned, it has not passed out of 

 existence. It has changed so that we 



may not at first be able to recognize it, 

 but it still exists. The changes that 

 have taken place in it are not merely 

 changes in temperature, expansion, 

 and the like, such as we have been 

 discussing in former chapters, for if 

 this were true the gas which passes 

 away from the flame would condense 

 into a liquid, and the liquid would 

 harden into the kind of wax with which 

 we started. It may readily be observed 

 that this does not take place. The 

 molecules which leave the flame and 

 mingle with the air are different from 

 the molecules of the wax as they come 

 to the flame. Let us see, then, what sort 

 of substance we can find coming from 

 the flame, and learn how the changes 

 occur which give us other substances in 

 place of the wax with which we started. 



58. Water produced by a flame. If a cold object, as a piece 

 of iron or a test tube full of water, is held in the flame, soot 

 may collect on it. We shall not give attention to the soot for 

 the present. Another thing that we shall find in the flame is 

 not ordinarily expected. Drops of water collect upon the cold 

 object, but if the object is allowed to get hot, the water evapo- 

 rates again. The water came from the flame. It must have 

 been formed in the flame, for we did not supply water to it. 



FIG. 34. Inflammable gas 

 secured from the flame 



By the use of a tube the un- 

 burned gas from the center 

 of the flame may be con- 

 ducted outside and there 

 burned 



