719 



something about tlie ring tension eventually occui-ring in those acid 

 anhydrides, it iiad to be decided whether the dissociation constant 

 of the acids was the only or principal factor which, besides that 

 ring tension, could exert an intlnence on the hydratation velocity. 

 The hydratation of the anhydrides of the fatty acids seemed to him the 

 most appropriate one, because in this the factor of the ring tension 

 is excluded, whilst that of the dissociation constant can be readily 

 applied. Moreover, the values of the dissociation constants of the 

 fatty acids do not diverge much, so that other factors can exert 

 their influence distinctly. While the detailed account of this invest- 

 igation will be published in another form '), we give here a short 

 summary of the results obtained. 



The hydratation velocity of the acid anhydrides was determined 

 in the manner indicated by Voi-^rman '^), namely by measuring the 

 conductivity of the aqueous solutions in which it is assumed that 

 only the acid determines the conductivity and that this is not 

 modified by the anhydride still present. 



The conductivity of the acids and the dissociation constant to be 

 deduced therefrom had to be accurately known, because from the 

 conductivity found in the hydratation the concentration of the acid 

 formed (and consequently that of the anhydride consumed) had to 

 be calculated. As the values given in the literature for the diss, 

 const, often differ considerably, we judged it necessary to make 

 new determinations thereof. 



They were carried out in the usual manner already frequently 

 described by us. 



A correction for the conductivity of the water itself (1 — 1.5 X lO-**) 

 was not applied, because this conductivity is caused in the carefully 



Dissociation-constants of the fatty acids. 



^) Dissertation of P. E. Verkade to appear shortly. 



~) Recueil 23, 265 (1902). Dissertation Groningen 1903. 



