AIR 



469 



3. Remove the cotton-wool plug from the flask, and 

 replace it by the rubber stopper with its fittings. Make 

 sure that the end of the stem of the funnel is immersed 

 in the bouillon. 



4. Place the flask in a glass or metal vessel and pack 

 it round with pounded ice. Arrange the flask with its 

 ice casing just above the neck of the aspirator bottle. 



FIG. 216. Arrangement of apparatus for air analysis. 



5. Connect up the free end of the glass tube from 

 the flask after removing the cotton-wool plug with 

 the air-entry tube in the mouth of the aspirating 

 bottle (Fig. 216). 



6. Open the tap fully, and allow the water to run. 

 Replenish the ice from time to time if necessary. 



(In emptying itself the aspirator bottle will aspirate 

 10 litres of air slowly through the water in the Erlen- 

 meyer flask.) 



7. When the aspiration is completed, disconnect the 

 flask and remove it from its ice packing. 



