X, A, 1 Gibbs and Brill: Diethylsuccinosuccinate 61 



that the pure enol form is colorless, while the keto form is yellow 

 due to general absorption or the extension of an absorption band 

 lying near the visible region. The fixation of the labile hydrogen 

 atom or the saturation of the free affinities of the oxygen atoms 

 in the para position destroys the absorption band. The behavior 

 of this compound in the enol form is quite similar to that of 

 methylsalicylate. 



