724 



In consequence of Voerman's observations (1. c.) we first believed 

 tluit the anhydride might be polymerised and that a succession of 

 depolymerisation and hydratation was measured. As, however, the 

 anhydride did not give the least indications of polymerisation even 

 in strongly associating liquids, CgH^ and C^H^NO^, we gave up this 

 idea in favour of the following assumption. 



We can imagine the j)rocey8 to be divided into two j)hases: the 

 first is the union with water or the hydratation i)ro})er ; the second 

 is the splitting of the hydrate into two molecules of acid. 



Now in the case of the lower acid anhydrides the first process 

 will take place very i-apidiy causing the second one to be measured 

 only; hence, the reaction exhibits the form of the simple unimole- 

 cular change. 



If the velocity of the fii'st in regard to the second is no longer 

 practically infinite, we are then dealing with the succession of two 

 unimolecular processes occurring in the same direction and the uni- 

 molecular-calculated constant will exhibit a reguhu- change ^). 



We give here three of these observation series obtained with very 

 carefully purified synthetic /.vcvaleric anhydride. 



FalUng constant of the hydratation of the isovaleric anhydride. 



Constant 

 X106 



2000 



1800 



1600 



1400 



1200 



1000 L 



0-point 0-point 0-point time 2/3 mm. = 1'. 



1st Series 2nd Series 3rd Series 



The further discussion of these observations in connection with the 



1) OsTWALD. Lehrbuch Allg. Gh. II, 2, 285. 



