153 



TABLE I. 



Carbon Dioxide ix Freshly Distilled Water. 



Titrated at room temperature 22°C. 



All yield water containing carbon dioxide and the amount of carbon 

 dioxide varied with the same make as well as different makes of stills. 



Test of Effect of Carbon Dioxide on Media Titrations. 



The results reported in Table II were an attempt to find out how 

 much the titration of media would be aflPected by the carbon dioxide 

 present in distilled water from one of the above stills. The point under 

 investigation being to determine the effect of carbon dioxide, the water 

 was prepared and titrations were made at about 70° C. so that it would be 

 evident that the results were not due to carbon dioxide being absorbed 

 by the media or water from the air of the room while cooling to room 

 temperature. Two two-liter flasks which had previously been proven 

 to be made of non-soluble glass were filled with distilled water. The 

 water in one flask was boiled for about five minutes to remove the car- 

 bon dioxide present while that in the other flask was heated to 75 °C. 



Duplicate twenty-five cc. aliquots of each media were weighed into 

 clean, carbon dioxide free, erlenmeyer flasks; 100 cc. of the hot carbon 

 dioxide free water was added to one of each of the duplicate aliquots 

 of media and 100 cc. of the hot yet unboiled water added to the other 

 flask of each set of duplicates. Two drops of phenolphthalein were added 

 to each flask after they had been shaken until the contents appeared 

 homogenous. Titrations were made with carbonate free N/10 sodium 

 hydroxide* and the faintest discernible, yet permanent pink coloration 



* Make a solution of the alkali (sodium) so strong that the carbonate contained will 

 be precipitated. Add the clear supernatant liquid which is carbonate free to carbon 

 dioxide free water and standardize. 



