124 The Philippine Jownal of Science 1914 



sulphuric acid, which exists only in solution and is at once broken 

 up by dilution with water, while thiophthaloxime in sulphuric 

 acid represents true chemical combination and corresponds to 

 similar addition products, such as benzaldoxime hydrochloride, 

 phenolphthalein oxime hydrochloride, etc. 



The absorption spectrum of thiophthaloxime sulphate in 

 alcohol is very different from that given by the oxime in con- 

 centrated sulphuric acid (dot curve, fig, 5). The general 

 transmission of the former extends much farther into the ultra- 

 violet, and the two bands are more refrangible. The spectrum 

 is distinctly approaching the phthalide type, and shows the 

 decreased activity of the side ring caused by satisfying the two 

 extra normal valencies of the nitrogen atom. 



The spectrum given by phthalanil oxime shows the decreased 

 activity of the lactone ring when anhydride oxygen is replaced 

 by the aniline residue. The reduction is entirely analogous to 

 that noted in comparing the spectra of phthalophenone and 

 phthalophenone anilide in alcohol as well as in sulphuric acid 

 solutions. 



The action of alkali on phthalanil oxime in alcohol is to shift 

 the band nearer the red, reduce the more refrangible band, and 

 extend general absorption into the visible region with the pro- 

 duction of a yellow color. Concentrated sulphuric acid has only 

 a slight effect, and the change to acetate has even less. 



The absorption spectra of various other closely related com- 

 pounds will be presented in a future paper. 



SUMMARY 



1. The absorption spectra of various phthalides containing 

 sulphur replacing oxygen have been studied in ordinary solvents 

 and in concentrated sulphuric acid. 



2. Dithiophthalimide and thiophthaloxime have been pre- 

 pared, and satisfactory proof has been obtained from their 

 spectra in support of the unsymmetrical structure for phthal- 

 oxime. 



3. Further evidence has been presented that color production 

 upon salt formation in oximes of this type is not due to molecu- 

 lar rearrangement, but is dependent upon changes in partial 

 valency equilibrium. 



4. The theory regarding color in thionyl derivatives of phthal- 

 ides has been extended. 



