152 



LAURENCE F. FOSTER AND SAMUEL B. RANDALL 



Ph, namely the 8.6 and 9.0 tubes. These two lots were practically 

 the only ones to exhibit changes upon standing, the 9.0 registering 

 an acidity change of 0.7 Ph after fourteen days standing. In series 

 II (table 2) decreases in acidity are noted in the acid and alka- 

 line ranges upon autoclaving while within the range 6.6-7.3 the 

 broth remained unchanged. In every lot of this series the acidity 

 increased upon standing, the greatest changes occurring in the 



TABLE 2 



Experiment I. Changes in reaction upon autoclaving and standing. (Beef extract 



broth) 



Composition: 



Distilled water 1000 cc. 



Liebig's beef extract 3 grams 



Peptone (Parke, Davis & Co.) 10 grams 



NaCI 5 grams 



* Precipitate. 



t A slight fading of the standard buffer mixtures of the thymol blue series 

 may have occurred thus accounting for the apparent increase in alkalinity. 



more acid and alkaline ranges. Here, as previously mentioned 

 in the case of beef infusion broth, the changes on standing seem to 

 be independent of the environmental temperature. 



The results in the bacto-beef series (table 3) are similar to those 

 noted in the case of beef infusion. A decreased acidity in general 

 appears in the range, 5.0-6.2, the 6.6-8.2 tubes remain practic- 

 ally unchanged, while the most alkaline members, 8.6 and 9.0 

 show increases in acidity upon autoclaving. Upon standing at 



