HYDROGEN IONS, ETC., OF BACTERIOLOGICAL MEDIA 559 



indicated by the symbols Rh(pH n - 8) in which n = the ini- 

 tial pH. The amount of acid required to raise the hydrogen ion 



The Buffer Index in terms of per cent normal hydrochloric acid. 



n 1 2 ^ ^ S 6 1 2 '^ 4 ^ 6 



Text-Fig. 1. Graphic Representation of the Buffer Indices of a Number 

 OF Samples of Bouillon 



concentration from pH n to pH 5.0 may be called the ''reserve 

 alkalinity" (Washburn 1910) of the medium indicated 'by the 

 symbols Ron (pH n - 5). The ''buffer index" indicated by 



