96 PROCEEDINGS OP SECTIOX B. 



chem. Soc, 1889, 21, 192). Luniiere and Barbier (Bull. Soc. Chini., 

 1906, III., 35, 625) ; Benratli (Zeitschr. Phys. Ckem., 1909, 67, 501) ; 

 Eivelt and Sidgwick (Journ. Chem. Soc, 1910, 97. 733 ; and 1677) ; 

 and Orton and Jones (Ibid., 1912, 101, 1708). 



Four difEerent methods of analysis have been followed, the most 

 rapid of which is that depending on conductivity measurements and 

 adopted by Rivett and Sidgwick (loc. cit.). 



The author used this method with slight modifications as to tha 

 form of the cell, and a general account was given of the apparatus and 

 of the method of conducting an experiment where the anhydride was 

 either a solid or a liquid. Some difierences arise in the methods of 

 obtaining the figures required for calculation of the order of the 

 reaction, according as the procedure is that suited for a solid or that for 

 a liquid anhydride. Provided that the rate of solution is greater 

 than the rate of hydration, measurements of the latter are possible 

 ■\vithin certain limits. In all cases the hydration follows the unimole- 

 / ^ 



cular law - log —. = Iz, where i is measured in seconds, and x is the 



i ^ A-x 



concentration of liydrated anhydride whose initial concentration is A. 

 The concentration of the water remains practically unaltered in the 

 dilute solutions dealt with, and is included in Ic. 



Some twelve anhydrides have been investigated, but of them 

 only three hydrated sufficiently slowly for measurements to be possible 

 either at 25 deg. or at deg. The work on these substances is briefly 

 summarized in the following account : — 



A. Derivatives of succinic acid. (For this acid, velocity con- 

 stant = 0-00116)— 



1. Diacetyltartaric Anhydride. — Prepared by heating tartaric 



acid and acetyl chloride in a flask with a reflux condenser 

 for several hours and subliming the product in a stream 

 of carbon dioxide. M.P. 128-129 deg. Hydration too 

 fast to be measured. An account of the conductivity 

 and dissociation of this acid is given by Deakin and 

 Rivett in Journ. Chem. Soc, 1911, 101, 127. 



2. Dibromsuccinic Anhydride. — Formed from the acid and 



acetyl chloride by heating in a sealed tube at 100 deg. 

 and purified by distillation under low pressure. B.P. 

 145 deg., under 29 mm. Hydration is very rapid, but 

 measurable. The values of k obtained at 25 deg. for 

 various concentrations of anhvdride are summarized in 

 Table I. 



