20 THE ROYAL SOCIETY OF CANADA 



responding small excesses of phenol, whilst the effect of larger ex- 

 cesses of phenol is greater than the effect of correspondingly larger ex- 

 cesses of pyridine. Thus the equilibrium 



(C6H50H)2 C5H5N ^ 2C6H5OH + C5H5N (2) 



can not be dominant either. 



The effect of excess of pyridine and of phenol on the extraction of 

 these bodies from benzene solution by aqueous acid and alkali respec- 

 tively which is described in the earlier paper, as well as the effect of 

 similar excesses on the apparen^t dissociation of the pyridine phenate 

 in benzene solution described in this paper can be satisfactorily ex- 

 plained as follows: 



If we start with the compound CeHsOH C5H5N 

 this dissociates as follows: 



CeHsOH C5H5N ^ C6H5OH + C5H5N (1) 



Excess of pyridine will depress this dissociation in a normal manner 

 and the effect of the excess will be proportional to the amount of 

 pyridine added. Excess of phenol will in the first instance behave 

 similarly to excess of pyridine, but in this case the excess will also 

 promote a second reaction 



CeHsOH + CeHôOH CsHsN Z^ (C6H50H)2 C5H5N 



and thus the excess not only depresses dissociation (1), but also re- 

 moves the compound CeHôOH C5H5N from the right hand side of 

 equilibrium (1) thus tending still further to diminish the concentra- 

 tion of the free pyridine. Thus the effect of excess of phenol will be 

 much greater than the effect of excess of pyridine. 



It was further shown that on increasing dilution of the benzene 

 solution the differences in the effect of addition of excess of phenol 

 and of excess of pyridine on the extraction efficiency tend to become 

 less and to disappear. 



