STAINING, PRACTICAL AND THEORETICAL 



STILBENE GROUP 



This is a subdivision of the azo group. Stilbene dyes contain 

 one or more azo groups in their molecules. They are all conden- 

 sation products of 5-nitro-toluene sulphonic acid. The chromo- 

 phore of the stilbene dyes may be the azo group or the azoxy 

 group, or both. 



Up to the present time only two stilbene dyes appear to have 

 been used in microscopy. They are both acid dyes of high mole- 

 cular weight. One is Mikado orange G, and the other Sun yellow 

 G. The structure of the latter dye is given below: 



SUN YELLOW G 



Michronie No. 720. Molecular weight 837. An acid dye, pH 7-3*. 

 Solubility at 15° C: water 1%, absolute alcohol o-oo8%. 



NaOsS 



SOsNa 



CH 



NaOaS ^ SOsNa 



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



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