230 Biological Stains 



2. THIAZOLE DYES 



A small group of dyes of rather complex formula contain the 

 thiazole ring: 



\ /s 

 c I 

 II c- 



c II 

 / \N 



in which the indamine group is the chromophore. References to 

 these dyes in biological literature are rare, but the following have 

 been mentioned; two of them, it will be noticed are also azo dyes 

 and thus possess two chromophores. 



f5 



This is a useful dye in fluorescence microscopy; see Pick (1935) 

 and Jenkins (1937). 



FlO PRIMULIN C. I. NO. 81I 



Synonym: Primuline yellow, 

 A mixture, consisting mainly of the following: 



N N SOiNa 



/\/ll /\/II I 



CH, I I C\| I C\/-\ NH. 



~\/\ I \/\ I \_/~ 



s s 



CziHuNaOaSaNa; Mot. Wt. 475.523 



{An acid dye) 



Among various other thiazole dyes. Pick (1935) employed 

 primulin as a vital stain, for which it is useful because of its fluores- 

 cence under ultra-violet illumination. It has since become quite 

 widely used for the purpose. 



