HYDEOGEN-ION CONCENTRATION OF BROTH MEDIA 



151 



Reference to tables 1 and 4, containing data for the two beef 

 infusion series, reveals differences in Ph changes as a result of auto- 

 claving. WTiereas every tube of series I showed an increased 

 acidity upon sterilization, the tubes of series IV from 5.0 to 5.8 

 inclusive exhibited a decrease in acidity; those of Ph 6.1-7.3 suf- 

 fered no alteration in reaction, while those lying in the 7.8-8.9 

 range showed a definite increase in acidity. Upon standing, the 

 greatest changes in both series are manifest in the 8.6 and 9.0 



TABLE 1 



Experiment I. Changes in reaction upon autoclaving and standing. {Beef 



infusion broth) 

 Composition : 



Distilled water 1000 cc. 



Chopped lean beef 300 grams 



Peptone (Parke, Davis & Co.) 10 grams 



NaCl 5 grams 



* The unexpected increase in alkalinity may have been more apparent than 

 real due to a fading of the standard buffer mixtures of the methjd red series. 



tubes. These changes are in the nature of increases in acidity 

 and are as great in magnitude as those produced by autoclaving. 

 A possibility of this sort has apparently been overlooked by many 

 observers. No differences worthy of mention appear as a result 

 of storiQg the broth under different conditions of temperature. 

 Passing to the two beef extract series (tables 2 and 5) a remark- 

 ably small number of alterations are notable iq one case (V). 

 An increase in acidity of 0.2 Ph occurred in the two lots of highest 



JOURNAL OP BACTERIOLOGY, VOL. VI, NO. 2 



