A YEAR IN SCIENCE 121 



Directions: A. Temperature. Expose the ther- 

 mometer to the room temperature for five minutes 

 and record the temperature. Then breathe on the bulb 

 of the thermometer for a few minutes and record the 

 temperature of expired air. What change has taken 

 place in the temperature of the air while in the lungs ? 



B. Composition. For the composition of inspired 

 air see Exercise 38. 



a. Breathe on the glass plate. What collects on the 

 surface? Does expired air contain more or less mois- 

 ture than inspired air ? 



b. Into a wide mouth bottle pour lime water to 

 the depth of an inch. Fit the mouth of the bottle with 

 a rubber stopper fitted with a long and short glass 

 tube. Adjust the long tube so that the end is below 

 the level of the lime water. Draw air 



from the room through the lime water by 

 suction applied to the free end of the 

 short tube. Continue this for two minutes. 

 Insert the stopper with the tubes into a 

 second bottle containing lime water. Pass 

 expired air through the lime water by 



blowing into the free end of the long Fig - 32 - 

 tube. Continue this for. two minutes. How does the 

 lime water in the two bottles compare? Which contains 

 the greater amount of carbon dioxide, inspired or expired 

 air? 



c, Fill a bottle Avith expired air by downward 

 displacement of water. Turn the bottle mouth upward 



