178- EXAMINING AIR, SOIL, WATER, AND FLUIDS FOR BACTERIA 



3. Rubber stopper to fit the mouth of the flask, perforated with two 

 holes, and fitted as follows: Take a piece of glass tubing, 15 cm. in 

 length and bend up 3 cm. at either end at right angles to the main 

 length of tubing. Pass one of the bent ends through one of the per- 

 forations in the stopper; plug the opposite end with cotton. Take 

 a glass funnel, 5 or 6 cm. in diameter, with a stem 15 cm. long, and 

 bend the stem close up to the apex of the funnel in a gentle curve 

 through a quarter of a circle. Pass the long stem through the other 

 perforation of the rubber stopper. In addition, rubber tubing, screw 

 clamps and spring clips for tubing, a steam sterilizer, retort stand and 

 clamps are required. 



FIG. 106 



Arrangement of apparatus for air analysis. (Eyre.) 



Method of Procedure. 1. Fill the aspirating bottle with 10 liters 

 of water and attach a piece of rubber tubing with a screw clamp to 

 the delivery tube. Regulate the screw clamp by actual experiment 

 so that the tube delivers 1 c.c. of water per second. At this rate the 

 aspirator bottle is emptied in just under three hours. Close the rubber 

 tube below the clamp by means of a spring clip, and make up the 

 contents of the aspirator bottle to 10 liters. 



2. Sterilize the fitted rubber cork with its funnel and tubing by 

 boiling in the steam sterilizer for ten minutes. 



3. Remove the cotton plug from the 250 c.c. Erlenmeyer flask 

 containing 50 c.c. sterile bouillon and replace it by the rubber stopper 

 with its funnel and bent tube. Make sure that the end of the stem 

 of the funnel is immersed in the bouillon. 



