908 



Increase of conductivity of a 0.5 mol. H3BO3 solution at 25° in 



KOHLRAUSCH-HOLBORN-UnitS X 10®- 



Tliis intliience proved to be very great. 



We had expected it to be greater tlian that of gallic acid. From 

 the researches on free acids it was proved that here two influences 

 are making themselves felt; the first is the eventually increasing 

 influence of boric acid on the substances; the secomWs the decreasiitij 

 influence of boric acid as d medium on the conductivity of the acids. 



With an acid of the strength of gallic acid this decreasing in- 

 fluence is rather important; the dissociation constant is equal to 

 ±4X10-^,80 it is situated between that of glutaric and adipic acid. 



From this one may lix approximately the decreasing action of 

 different dilutions in percentages of the original conductivity '). 



Acid. 



K25X105 I 1/-4 mol. "48 mol. ; '/ge mol. I V192 mol. 



Instead of the increases of the conductivity which were found, 

 one calculates the figures mentioned below, viz. one obtains figures 

 entirely of the same order as those fixed for pyrogallol and pyro- 

 catechol; they are distinctly higher even and approach those of 

 gallic acid methyl ester. From this one may draw the conclusion 

 (hat the carboxyl group in the benzine nucleus exercises an mcr(?rtó-z?2(/ 

 influence on the rise of the conductivity caused by pairs of hydroxy 1 



1) Recueil 36, 177 (1917). 



