f 411 ) 



Dl'. VoKHMAN' lias firsl of all prepared iliesc aiiliyclrkles, then dis- 

 solved tlieiii in a large aiiiouiil of water aii<l deteniiined the velocity 

 of iheir transforiiiation into acids. 



The anhydrides investigated were those of snecinic acid (Cj, glntaric 

 acid ^('jj, adi[)inic acid (Cj, pimelic acid (C-), snberic acid {t\), 

 azelaic acid ((\) and sebacic acid (C^J. Many of these acids arc dif- 

 licnlt to ])ro('ure. Init Dr. A'okrmax has sncceeded in greatly impro- 

 ving their mode of [)reparation, for the [)articnlars of which we refer 

 to a commnnicatiün shortly to appear in the Recneil. 



In order to determine the velocity with which these anhydrides 

 pass into acids when introduced into ^vater, it was necessary to be 

 able to determine at any given moment the (|naiitity of acid which 

 had already been formed. This is done by measuring the electric 

 condnctivity of the solntion, taking it for granted that the solution 

 of the anhydride does not conduct the current. 



This snpposition is first of all jnstitied by the observation that 

 the conductive power of the anhydride solntion is smaller the sooner 

 it is measnred after it has been prepared and secondly because the 

 acid anhvdrides do not belong to the class of electrolvtes. In order 

 to obtain the concentration of the acid in the solntion from its con- 

 dnctivity it is only necessary to measure the conductivities of solutions 

 of the acids at the temperature employed over the range of con- 

 centrations which is considered in the experiments. These measure- 

 ments were conducted by Dr. Voerman, who generally used the 

 acids which were recovered from the anhvdrides by the action of 

 water in order to work under quite the same conditions as existed 

 in his velocity determinations. As might, however, have been expected 

 the same values were obtained for the conductivity of the acids 

 themselves and those recovered from their anhydrides. 



As the concentration of the acid, after the complete conversion 

 of the anhydride, in the velocity measurements did not exceed ^/j, 

 norinal, the quantity of water may be taken as constant, so that the 

 con^'ersion may be represented by the equation for unimolecnlar 

 reactions. This indeed, gave satisfactory values for the constant 

 occurring therein. 



It is, however, only in the case of the anhydrides of succinic and 



glntaric acids that Dr. Vokkman has obtained satisfactory determi- 



1 C 

 nations, at 25°, of the values of K =: 1~ it in minutes, C = 



t,-t, C, 



grm. mol. per Litre). 



He obtained the values 0.1683, and 0.1708 showing that the 

 5-ring is somewhat more stable than the (>rin2:. In the case of the 



