vin, a, 3 Pratt and Gibbs: Two Phthaloximes 177 



depends. Two possible formulas representing the oxime salts 

 may be expressed as: 



CeH/ > I and ' C 6 H 4 0^ 



\ C ===N C=N=0, 



the second of which would explain color formation as depending 

 upon the quinoid condition of the benzene ring and might be con- 

 sidered as in equilibrium with the first. The theory of partial 

 valency may also be applied to the second formula giving a con- 

 jugated linking in the side chain that may be represented by 

 the formula: 



< 



'\ 



M 



=N==0 " 



The salts would then belong to the enol-nitroso type. 



No method is available to decide definitely between these two 

 explanations of the very marked change that takes place when 

 phthaloxime is converted into its highly colored salts. The par- 

 tial valency theory explaining color as dependent upon a changed 

 condition of equilibrium brought about by a positive metal atom 

 without actual molecular rearrangement has much to recommend 

 it, and seems to be in better accord with our present ideas of 

 chromophoric chemistry. 



ABSORPTION SPECTRA OF THE PHTHALOXIMES, THEIR METHYL 

 ETHERS, ACETATES, AND BENZOATES 



The complete curves of the absorption spectra of the two 

 phthaloximes are shown in fig. 1. Solutions in absolute alcohol 

 were employed when not otherwise stated, and the spectra 

 photographed with a Hilger spectrograph 23 using a nickel arc 

 as the source of light. 



The curves are plotted with logarithms of thickness of layer 

 in millimeters of ten thousandth molar concentration as ordi- 

 nates, and oscillation frequencies of the limits of transmission 

 as abscissa. 



" The purchase of this instrument was made possible through the gen- 

 erosity of Mr. Enrique Zobel, Mr. Antonio Roxas, Mr. Manuel Earnshaw, 

 Dr. Ariston Bautista y Lim, the San Miguel Brewery, and the Germinal 

 Tobacco Factory. 



