725' 



relation applying to the unimolecular follow reactions will be 

 given elsewhere; we call, however, already now the attention to 

 the fact that Benratii ') has fonnd thai in glacial acelic acid (he 

 reaction between equivalent qnantities of water and acetic anhydride 

 proceeds nnimolecnlarly, which can only be explained by assuming 

 that in glacial acetic acid they are dissolved Jointly as hydrate (in 

 fact that the hydration proceeds exceedingly rapidly) and tiiat this 

 hydrate splits np into the acid molecules '). 



Farther, we have also succeeded in demons! i-ating the formation 

 of other additional com[)Ounds with the acid anhydrides of which 

 those with isovaleric anhydride exhibit a greater stability than those 

 with the lower acid aidiydrides. 



Thus we conld isolate the additive products of hydroferricyanic 

 acid with wovaleric and heptylic anhydride in a crystalline condition 

 and analyse the same whereas these two gave with 70 7o perchloric 

 acid colorations that pointed to additi\e action. 



With great probability we may conclude already now that the 

 conversion of acid anhydrides into acids proceeds in two phases; 

 presumably there first takes place a linking of the anhydride to the 

 watermolecu les which occurs very rapidly with the lower terms; 

 this is then succeeded by the splitting reaction which takes place 

 more slowly. 



The analogy existing between the acid anhydrides, the esters, and 

 the ethers and between the acid formation, the saponification and 

 the alcohol formation causes the elucidation of the first reaction to 

 become of a more general significance. 



If, on further working out the results obtained, it appears that 

 the process studied by us proves with certainty the linking of water 

 followed by hydrolysis, we may expect this to be also the case with 

 the other processes mentioned. 



Like in so many other chemical transformations we again get here 

 the impression that the reaction proper is preceded by a previous 

 stage, namely the mutual influence of the molecules. 



This is often shown by the formation of an additive product, but 

 here, as in the case of the catalytic phenomena, the reaction proper 

 will proceed more rapidly when this additive product forms more 

 quickly and possesses less stability. 



1) Z. Ph. Gh. 67. 501 (1909). 



~) Benrath measures the density of a mixture of acetic anhydride, glacial acelic 

 acid and water during the hydration; he finds a cliange in density of about one 

 unit in the second decimal. 



