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 

 up to its middle, and plug its open end with 

 two small cotton -wool plugs (p l 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\ 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 



FIG. 7. 



and p 2 , small 

 cotton -wool 

 plugs. 



c' 



P' 



FIG. 8. Aspirating Apparatus. 



FIG. 9. 



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

 connections as required. 



