T 



CHAPTER VI 



THE QOXOXE-IMINE DYES 



HE dyes of the quinone-imine group contain two chromo- 

 phore groups, the indamin group — N = , and the quinoid 

 benzene ring 



They are derivatives of the theoretical compound paraquinone- 

 di-imine, which, if it existed in its free state, would have the 

 formula 



HN 



NH 



In the typical indamin formula one of the imine hydrogen atoms is 

 replaced by a phenyl group, thus: 



In the thiazins the introduction of a sulfur atom, attached to 

 both the phenyl and the quinone groups, forms a third closed ring. 



as: 



-NH 



\/~N=\/ 

 imino-thio-diphenylimine 



In the oxazins an oxygen atom, and in the azins a nitrogen atom 

 takes the place of the sulfur of the thiazins, thus: 



/X— NH 



\/~N=X/ 

 oxazin 



H 



I 



\/~N= 

 azin 



NH 



1. THE INDAMINS 



The indamin dyes are methylated amino derivatives of in- 

 damin. No dye in this group is a common biological stain. The 



101 



