16 EXPERIMENTAL PHYSIOLOGY 



VI. — ^Properties of Iron. 



Apparatus. — Several feet of fine wrought-iron wire, a magnet, an 

 evaporating dish. 



Directions. — Bring the magnet in contact with the iron. 

 Raise the magnet. Note that the iron is attracted to it. 

 See if other things are similarly attracted to it. 



Place a coil of the wire in a warm, dry place. Place a like 

 coil in the evaporating dish and cover with water. Leave 

 both coils for several days, and then examine them. Note 

 that one of them is covered with a reddish deposit (rust). 

 What conditions are favorable to this formation? (Rust 

 is a compound that iron forms with the oxygen of air and 

 water. It is this power of iron to unite with oxygen that 

 makes it valuable as a part of the blood in the animal body; 

 see Exercise XLIII, D, on page 71.) 



VII. — Oxygen and Oxidation. 



Apparatus. — Red oxide of mercury (mercuric oxide), test tube, 

 stick of charcoal, limewater and glass tube, alcohol lamp or Bunsen 

 burner. 



Directions. — ^Place in a test tube as much red oxide as 

 you can get on your finger nail. Heat the 

 test tube in the flame (see Fig. 4). Heat 

 the end of the charcoal stick until it glows, 

 and introduce it into the mouth of the 

 test tube. After heating the oxide hot you 

 will notice a change in the glow of the 

 charcoal. Describe it. Can you see any- 

 thing in the tube? If it be a colorless 

 Fig. 4. g^g ^]^^^ jg actiug ou the charcoal can that 



gas be air? Reasons for your statement? ^ 



