EXAMINATION OF WATJER AND SEWAGE 145 



Dilution flasks, filled with loo c.c. filtered tap water 

 or better loo c.c. 0.8 per cent NaCl solution, After 

 sterilization in the autoclave these flasks are assumed 

 to contain 99 c.c. each. 



Sugar-free meat infusion broth in bulk for fermenta- 

 tion tubes and in tubes — 20. 



In addition to these media the media Usted on p. 105 

 should be prepared. 



The reaction of all media should be adjusted to i 

 per cent acid to phenolphthalein. 



SECTION 2 



BACTERIOLOGICAL EXAMINATION OF WATER 



EXERCISE I. COLLECTION OF SAMPLES 



1. Tie a piece of filter paper or lead foil over 6 glass- 

 stoppered bottles of about 125 c.c. capacity. Sterilize 

 these in the hot-air oven for one hour at 160° C. 



2. Befpre taking the sample from surface waters 

 remove the paper cap, dip the bottle about 12. inches 

 below the surface, remove the stopper under water, 

 replace the stopper as soon as the bottle is filled, wipe 

 dry with a clean cloth or absorbent cotton, and replace 

 the paper cap. 



3. Pack the samples in ice in a suitable container. 

 They should be kept on ice until ready for examination 

 either in the laboratory or in the field. 



4. Samples from pumps should be collected after 

 several pails of water have been wasted. 



5. Samples from hydrants should be taken after 

 the water has been running freely for at least 15 

 minutes. 



