xxi CAKr.oN AND SOMK OF ITS COMPOUNDS iiW 



but that a gas slowly collects and fills the tube. Take out the 

 tube and apply a light to the gas. Observe that it burns with 

 a blue flame. 



\\e have, therefore, obtained the gas expected, and if the 

 tube be examined oxide of iron is seen to be present. On 



FIG. 138. Preparation of Carbon Monoxide. 



burning, the gas again forms carbon dioxide, and its composition 

 may be represented by CO, the name carbon monoxide l being 

 given to it. We may then state : 



Carbon dioxide and iron yield carbon monoxide and iron 

 oxide, or 



4CO 2 + 3Fe = 4CO + Fe 3 O 4 . 



The burning of carbon monoxide may be also expressed by the 

 following equation: 



Changes in a Coke Fire. The formation of this gas in coke 

 fires may now be readily explained. By the burning of the carlx >n 

 in the lower parts of the fire, where the air enters and sufficient 

 oxygen is present, carbon dioxide results, but when this passes 

 over the heated charcoal in the upper parts where insufficient 

 oxygen is present, it parts with some of its oxygen, forming 

 carbon monoxide. Thus, 



1 It is sometimes spoken of as carbonic oxide, but the name used above is pref- 

 erable. 



