20 



EXPERIMENTAL PHYSIOLOGY 



suit. After the burning is over smell (Caution!) the gas 

 in the bottle. Compare with the odor of burning sulphur 

 in Ex. IV. What is the name of this gas? Is the action 

 noted above combustion? Give your reasons (see Ex. VII.) 



E. Heat the end of the fine iron wire red hot and intro- 

 duce it into the fifth bottle. Describe the result. After 

 the action is over examine the red spots on the sides of the 

 bottle and compare them with the rust obtained in Ex. VI. 

 What is the difference between the two actions? 



Name the properties of oxygen that you have observed. 



IX. COMPOSITION OF AIR AND PROPERTIES OF NITROGEN. 



Apparatus. Pneumatic trough, bell jar closed at the top, evap- 

 orating dish, test tube, phosphorus. 



Directions. Fill the pneumatic trough so as just to cover 

 the support. Place the evaporating dish on the support. 

 Place in it a piece of phosphorus the size of a pea; light the 

 phosphorus, and cover quickly with the bell jar. 



A. Note the white fumes that 

 appear. What are these? (See 

 Ex. VIII, <7.) What is one of 

 the components of air? When 

 the jar is first put on note that 

 some bubbles are forced out be- 

 cause the heat causes the air to 

 expand a little. The phosphorus 

 stops burning when all the oxygen 

 in the bell jar is used up. Let 

 the apparatus stand until the white oxide of phosphorus has 

 been absorbed by the water and the gas in the jar is clear. 





FIG. 7. 



