140 Studies on Solution. 



excess of aniline added. On shaking, this combines with the residual 

 acetic anhydride, precipitating acetanilid and liberating an equivalent 

 of acetic acid. In one bottle of each series the reaction was allowed to 

 go to completion without the addition of aniline, so as to control the 

 results obtained. 



The total amount of acetic acid was then determined in the bottle 

 by titration with the half-normal solution of sodium hydroxide in the 

 presence of phenolphthalein as indicator. Never less than 10 c.c. 

 nor more than 25 c.c. of alkali, as measured in a 50 c.c. burette, was 

 required to neutralize the acetic acid. 



Two temperatures, 15 and 25, were employed. Only one concen- 

 tration of acetic anhydride was used (approximately 5 per cent), 

 because if two were employed the results would not be comparable on 

 account of volume changes. For the salts molar, half-molar, and 

 quarter-molar solutions were taken in all cases, and whenever possible 

 solutions of greater concentration. 



Measurements of the velocity were not taken for longer than 60 

 minutes at 15 and 40 minutes at 25, for it was found that the hydroly- 

 sis of the acetic anhydride by water was then practically complete. 



CALCULATIONS. 



From the total amount of acetic acid, as determined by titration 

 with the alkali, that due to the water alone must be calculated. The 

 simple formula y = 2z x is used, where y is the amount of acetic acid 

 due to the water alone, z is the total amount of acetic acid measured by 

 titration, and x is the total amount of acid that can be formed if all the 

 acetic anhydride has been hydrolyzed. 



The results obtained for the "control" bottles, when substituted in 

 the formula, should give the same values for x and y, which would be 

 equivalent to 100 per cent hydrolysis. 



DATA. 



In tables 107 to 116 the concentrations of salt solutions are M, 

 molar; M/2, half-molar, etc. Time is expressed in minutes. All 

 results are expressed in percentages, 100 per cent meaning complete 

 hydrolysis of the acetic anhydride. In each table there is placed for 

 comparison a column showing the percentage decomposition of acetic 

 anhydride by water alone. 



