208 



HYDROGEN ION CONCENTRATION 



Some of Beutner's measurements are shown in table 33. 

 Thus we have an "electromotive series" for oily Hquids as well 

 as for the metals. 

 But also the chain 



Aqueous 

 salt solution 



Nitrobenzene 



Nitrobenzene 

 + picric acid 



Aqueous 

 salt solution 



studied long ago by Cremer^" may also be included in this group of 

 chains. For in this case the salt distribution on the two sides is 

 unequal; the dissolved picric acid effecting a higher concentration 

 of cations, which, in addition, is but httle dependent upon the con- 

 centration of the salt in the adjacent aqueous phase. 



TABLE 33 



Benzaldehyde 

 Benzaldehyde 

 Benzaldehyde 

 Benzaldehyde 

 Benzaldehyde 

 Benzaldehyde 

 Benzaldehyde 

 Benzaldehyde 

 Benzaldehyde 



with Cresol 



with Phenol 



with Guaiacol 



with Toluidine 



with Benzyl alcohol... 

 with Amyl alcohol. . . . 

 with Acetoacetic ester 

 with Acetophenone — 

 with Dimethylaniline. 



V0LT3 



The nitrobenzene dissolved on the right side in the picric acid 

 imparts to the latter a new character. The addition of an organic 

 acid to an oil renders the oil ''more positive" in the electromotive 

 series. In pure oils, however, it has not been found as a rule that 

 they are more positive according to the strength of their acidity. 

 Furthermore, it is not merely a question of the amount of acid in 

 the oil, but also of the degree of dissociation of this acid. The 

 dielectric constant of the oil phase is also of great importance. Of 

 two oils containing the same amount of acid the one with the smaller 

 dielectric constant is the more negative. Thus: 



Nitrobenzene saturated with nitrobenzoic acid 



Positive 



Without added 

 benzene 



+ an equal 

 volume of Negative 

 benzene 



i» M. Cremer, Zeitschr. f. Biol. 47, 1 (1906). 



