VII 



EXAMINATION OF AIR 



111 



(2) Draw out a glass tube (5 mm. in diameter and 12 to 

 15 cm. in length) at one end and fuse it off here. 



(3) Fill the tube with the powdered sugar A 

 up to its middle, and plug its open end with 



two small cotton -wool plugs (p 1 and j? 2 ), as 

 shown in the diagram (Fig. 7). 



(4) Sterilise this tube in the hot-air steriliser 

 at 100 C. for half an hour to one hour. 



(5) When cool remove the plug p 2 , and 

 connect the sugar tube with the aspirating 

 apparatus (Fig. 8). 



(6) Fix the sugar tube by means of a clamp 

 (C 1 , Fig. 9), and with a pair of sterile forceps 

 break off its drawn-out end. 



(7) Loosen the clamp of the aspirating ap- 

 paratus and aspirate by alternately changing the positions 



A 



Flo 7< 

 and *> 2 > sma11 



cotton -wool 



P lu s - 





FIG. 8. Aspirating Apparatus. 



FIG. 9. 



of bottles I and II, at the same time altering the 

 connections as required. 



