78 LABORATORY EXERCISES. 



B. Open a window, and place the two dishes near a 

 steam-pipe near the window. 



1. Does the moving air take the same course 



as before? 



2. Does the open window help or retard the 



ventilation of the room? 



NOTE. Gunpowder or flash-paper may be used instead of the 

 acid and ammonia. 



40. INSPIRED AND EXPIRED AIR. (Dem.) 



Materials : Thermometer, bottle fitted as described in C below J 

 lime-water. 



A. Difference in temperature. 



1. Note on a thermometer the temperature of 



the air in the room. 



2. Breathe for a few seconds on the bulb of the 



thermometer. Note temperature. 



3. What is the difference in temperature be- 



tween inspired and expired air? 



B. Difference in amount of moisture. 



1 . Breathe again upon the polished bulb of the 



thermometer. Describe result. 



2. What substance is thus shown to be one of 



the wastes excreted by the lungs? 



C. Differences in chemical composition. 



Secure a bottle fitted with a rubber stopper 

 with two holes. Through one hole in the stop- 

 per pass a glass tube (No. i) until it reaches 

 nearly to the bottom of the bottle. Pass the 

 end of another tube through the other hole, al- 



