BIOELECTRIC PHEXOMEXA 309 



in the same manner as an electrode reversible to cations. 

 The remarkable feature is that the reversibility relates to 

 salts of cations in general, and not only to those of a 

 single cation, as in the case of silver or other metallic 

 electrode. All of the alkali and alkali-earth cations 

 (those of the chief physiological interest) gave typical 

 results; thus with KCl the following obser\ations 

 were made;^ the non-aqueous phase was salicylic 

 aldehyde saturated with salicylic acid: 



Concentration E.M.F. 



of KCl Millivolts 



O. 1 6 



0.02 30 



0-004 55 



0.0008 89 



0.00016 130 



It was further shown that this effect is dependent on 

 the acid character of the non-aqueous phase; i.e., on 

 its ability to take up cations (reversibly) by salt forma- 

 tion; other solutions of weak acids, e.g., of benzoic acid 

 in phenol, behaved similarly. But when the non- 

 aqueous phase is basic in chemical character, the potential 

 changes in the opposite direction, the dilute solution 

 becoming more negative, instead of more positi\'e, with 

 increasing dilution, and the behavior is such as to indicate 

 reversibility to anions. Beutner found this to be the 

 case when the weakly basic compounds, aniline and 

 toluidine, were used as the water-insoluble phase in an 

 arrangement similar to the foregoing.^ 



^ Cf. American Journal of Physiology, XXXI (1913), 347- 



* For a complete account of Ikutncr's investigations cf. his recent 

 book, Entstehung eleklrischer Strome in kbcndcn Gruebcn (Stuttgart, 

 1920). 



