SECTION ONE 



THIAZINE GROUP 



Chromophore . 



/ 



C— N= 



II 

 C 



s = c 



+ 



The chromogen consists of this configuration as the inner ring 

 of a three-ring arrangement, the outer two being aromatic nuclei. 



About eleven thiazine dyes are used in microtechnique (Gurr, 

 i960). Only one of these is acid; the others are basic dyes. 

 Members of this group, best known to biologists, are methylene 

 blue, toluidine blue, and thionin. The structures of these three 

 dyes are given below: 



METHYLENE BLUE 



Michrome No. 416. Molecular weight 320. A basic dye, 

 pH 2-^*. Solubility at 15° C: water 9*5%, absolute alcohol 6%. 



(H3C)2N- 



N(CH3)2 



J ci- 



THIONIN (Ehrlich) 



Michrome No. 215. Molecular weight 264. A basic dye, 

 pH 2-2^*. Solubility at 15° C' water 1%, absolute alcohol 1%. 



H2N- 



NH2 



CI- 



1% in neutral distilled water; see pages 17 and 29. 



63 



