712 



Chemistry. — " Pseudoternarij systems of acid anhydrides and 

 iDater. 1. Phthalic anhydride.'' By Dr. H. R. Kruyt. (Com- 

 municated by Prof. Ernst Cohen). 



(Communicated in the meeting of December 27, 1913). 



F'or reasons, which will be further explained in a following treatise 

 of this series, the knowledge of the heterogeneous equilibria in 

 systems of acid anhydrides and water seemed to me of importance. 

 The only quantitative investigation that lias been made on this 

 subject is found in the dissertation of E. van de Stadt ^) and relates 

 to phthalic- and succinic anhydride. The results thereof may be 

 summarised as follows: If we shake the acid with water at a 

 definite temperature we soon attain an equilibrium; if, however, we 

 shake the anhydride with water, we notice a continuous rise of the 

 total-solubility-) at which values are attained far above the solubility 

 of the acid; then follows a period of fall quite as regular as the 

 previous rise, no discontinuity occurs, in this process; finally we 

 again arrive, at the solubility of the acid. These results suggest the 

 following inter[)retation: the anhydride has a greater solubility than 

 the acid, hence occurs the provisional high total concentration, but 



Mr 



FiK. 1. 



1) Amsterdam 1901. Also Zeitschr. f. physik. Ghem. 31, 250 (1899) and 41, 

 353 (1902). 



-) By this is meant the acid concentration as found by titration wliich represents 

 the sum of the acid- and anhydride molecules. 



