STERILIZING MEASURED AMOUNTS OF WATER IN 

 THE AUTOCLAVE^ 



H. A. NOYES 

 Purdue University Agricultural Experiment Station, Lafayette, Indiana 



Received for publication February 22, 1918 



It is customary for bacteriologists to measure out specific 

 amounts of water into flasks and then to sterilize the flasks and 

 water in the autoclave. Water is known to be lost during the 

 process of autoclaving but the amount lost is usually considered 

 to be so small that the errors occurring in bacterial dilutions 

 (from this source) are small in comparison to other errors made 

 in plating and dilution work. 



To ascertain just what the loss of water in autoclaving is and 

 just what effect this loss would have on dilutions, several tests 

 were made. Two of these tests are reported here. 



The following tables give the results of one sterilization of 

 water in bottles in the autoclave. In putting the water into the 

 eight ounce bot;tles, used in these tests, the technic was as fol- 

 lows: Each bottle was weighed to the nearest decigram and 99 

 grams or 90 grams, as desired, in excess of the weight of the bottle 

 was placed on the opposite pan of the balance. 99 cc. or 90 cc. 

 aliquots of distilled water were measured out by means of a 100 

 cc. graduated cylinder and poured into each bottle. In no case 

 was the amount of water poured in more than 0.35 of a gram away 

 from that desired. Water was then taken out or added so that 

 each bottle contained the weight desired. 



The bottles were sterilized for fifteen minutes under 18 pounds 

 pressure of live steam and then the pressure was reduced at the 



^ This report is part of the work done by the author in working out and classi- 

 fying errors in the plate method of enumerating bacteria. The investigations on 

 plate methods when completed will appear as a bulletin of the Indiana Agricul- 

 tural Experiment Station. 



537 



