viii, a, 3 Pratt and Gibbs: Two Phthaloximes 173 



The molecular equilibrium of phthaloxime salts may be rep- 

 resented by the formula: 



C=0- 



/ \ '•• 



C 6 H 4 M 



\ / / 

 C=NO 



This indicates merely the partial valency equilibrium between 

 negative carbonyl and positive metal, and shows a ring forma- 

 tion resembling the quinoid configuration. It is to be noted that 

 neither phthalic acid nor phthalimide can give analogous salts, 

 although the compounds themselves present a condition similar 

 to that of the oxime. The addition of alkali to solutions of these 

 substances causes no radical change in the position of their ab- 

 sorption bands, but causes a marked increase in the width of the 

 original band of the latter, indicating a difference in degree of 

 the existing equilibrium rather than a change in character. 



The application of the partial valency theory to colored salts 

 has been utilized by Werner 18 in the case of the yellow benzil- 

 oxime. He gives these compounds the following structure: 



CeHs — C C — C6H5 , 



II II 



N 



\)-M- ' 



but makes no mention of the equilibrium that must exist between 

 the unsaturated groups before the entrance of the metal atom. 

 Hantzsch has also used similar conceptions in much of his later 

 work, and has applied partial valency structures to many com- 

 pounds in which it is otherwise very difficult to explain the ab- 

 sorption spectra. 



Lassar-Cohn calls attention to the resemblance between phthal- 

 oxime and the nitrolic acids, and Hantzsch and Kanasirski 1T 

 have studied the absorption spectrum of the latter. They find 

 that ethyl nitrolic acid, 



/N0 2 

 H 3 C-C 



^NOH, 



"Ber. d. deutschen chem. Ges. (1908), 41, 1062. 

 "Ibid. (1909), 42, 889. 



119480 3 



