CHAPTER VI. 



THE DIFFERENCE IN CHEMICAL ACTIVITY OF FREE AND SEMI-COM- 

 BINED WATER AS ILLUSTRATED BY THE EFFECT OF NEUTRAL 

 SALTS ON THE HYDROLYSIS OF ACETIC ANHYDRIDE. 1 



BY GERALD C. CONNOLLY. 



INTRODUCTION 



HYDROLYSIS. 



The term "hydrolysis" is applied to a number of chemical reactions 

 in which there is first the addition of water to a complex, and then 

 the decomposition of the product into simpler substances. From this 

 definition it is evident that the reactions included under hydrolysis are 

 numerous and varied. There are, in general, four main divisions of 

 hydrolysis : 



(1) Hydrolysis of metallic salts. 



(2) Hydrolysis of esters and closely associated substances, such as 



amides, nitriles, acid chlorides, acid anhydrides, etc. 



(3) Hydrolysis of complex carbohydrates and glucosides. 



(4) Hydrolysis of polypeptides and proteins. 



In this discussion we will confine ourselves almost entirely to the 

 first two divisions, for these are the only forms of hydrolysis which 

 come within the scope of this investigation. 



HYDROLYSIS OF ACETIC ANHYDRIDE. 



The hydrolysis of acetic anhydride has been studied by several inves- 

 tigators with varying degrees of success. The term "hydrolysis of 

 acetic anhydride" is used here in preference to the term "hydration 

 of acetic anhydride" used by other investigators, since it is more in 

 accordance with the definition of hydrolysis previously stated. The 

 work of previous investigators has been carefully reviewed in a prelim- 

 inary paper on this subject. Therefore it need only be referred to here 

 when bearing directly on the present work. 



Menschutkin and Vasilieff, 2 in studying the decomposition of acetic 

 anhydride by water, found that with a mixture of equal portions of 

 acetic anhydride and water at 19 only about one-half the anhydride 

 was hydrolyzed at the end of 6 hours, and 1 1 days were necessary for 

 complete hydrolysis. In table 105, taken from their work, a com- 

 parison is made between the velocities of decomposition of acetic 



1 See preliminary paper on this subject in Carnegie Inat. Wash. Pub. No. 230. 

 2 Jour. Russ. Phys. Chem. Soc., 21, 188 (1889). 



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