CHAPTER VI. 



EFFECT OF NEUTRAL SALTS ON THE HYDRATION OF ACETIC 



ANHYDRIDE. 



BY GERALD C. CONNOLLY. 



HYDRATION OF ACETIC ANHYDRIDE. 



The hydration of acetic anhydride has been studied by several 

 investigators with varying degrees of success. 



Menschutkin and Vasilieff / in studying the decomposition of acetic 

 anhydride by water, attempted to find a constant for the velocity of 

 hydration. They did not succeed because the two substances did not 

 mix in all proportions, and no solvent could be found that did not act 

 either on the substances themselves or on the products of the reaction. 

 They studied the change in a homogeneous mixture of acetic acid, 

 acetic anhydride, and water, and found that the reaction was not as 

 rapid as had generally been supposed. 



Hinsberg 2 showed that the acetic anhydride was soluble in the w r ater 

 in the anhydride state, and that the presence of water was not an obstacle 

 to the employment of the anhydride as such. 



A. and L. Lumiere and H. Barbier 3 showed that a solution of acetic 

 anhydride in water possesses practically all the properties of acetic 

 anhydride and was sufficiently stable for acetylation purposes. 



In a second paper 4 A. and L. Lumiere and H. Barbier stated that 

 12 per cent acetic anhydride was soluble in water, solution taking place 

 immediately on shaking. They prepared 5 and 10 per cent solutions 

 of acetic anhydride in cold water and set them aside. From these 

 solutions equal aliquot parts were withdrawn every 10 minutes and 

 added to a slight excess of aniline, the excess being known. Reaction 

 took place quantitatively between the aniline and the acetic anhydride 

 not hydrated by the water, forming acetanilide and an equivalent of 

 acetic acid. The total acid present was then determined by titration 

 with a normal solution of sodium hydroxide in the presence of phenol- 

 phthalein. They found that the rate of hydrations was at first rapid 

 and then decreased, the rate being more rapid the greater the initial 

 dilution of the anhydride and the higher the temperature. They 

 carried out two experiments at and two at 15. They also prepared 

 alcoholic solutions of the anhydride and showed that when molecular pro- 

 portions were used, esterification was incomplete, even after a month. 



Benrath, 5 by means of change in density, attempted to measure the 

 rate at which the anhydride combined with the water in a solution of 



. Russ. Phys. Chem. Soc., 21, 192 (1889). *Ibid., 3, 35,625(1906). 



2 Ber. d. deutsch. chem. Gesell.,23,2962 (1890). 8 Zeit. phys. Chem.,67,501 (1909). 



3 BulI. Soc. Chim., 3, 33,783 (1905). 



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