COMPOSITION OF AIR ATOMIC THEORY 65 



one may observe that the burning is not taking place im- 

 mediately at the surface of the wick, but occurs chiefly in 

 the outer part of the flame. 



That there is a gas in the flame may be easily proved. 

 Place a small tube so that the end shall be in the center of 

 the flame, and try to light the other end (fig. 36). If this 

 is properly done we shall have a small 

 gas flame burn big at the end of the 

 tube, some distance from the candle 

 flame. If the end of the tube is not 

 placed in the center of the flame, but 

 at the surface, the gas secured cannot 

 be burned, because the gas is burning 

 at the surface of the flame. If a large 

 piece of paper is held across the widest 

 part of the flame, the paper directly 

 above the center of the flame will not 

 at first 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. 



67. Products of the flame. When 

 the gas formed from the wax of the 

 candle has been burned, it lias not 

 passed out of existence, although it has 

 changed so that we may not at first be able to recognize it. 

 These changes are not merely in temperature and expansion, 

 which 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. 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. 



FIG. 86. Inflammable gas 

 secured from the flame 



By the use of a tube the uii- 

 burned gas from the center 

 of the flame may he con- 

 ducted outside and there 

 burned 



