SECTION ONE 



NITRO GROUP 



Chromophore : NO2 



The nitro dyes form a comparatively small group. Picric 

 acid (2, 4, 6-trinitro-phenol) belongs to this group. All nitro 

 dyes are yellow in colour. They are all acid dyes. Members of 

 this group used as microscopical stains are: martius yellow, 

 Manchester yellow, naphthol yellow S, aurantia, and naphthol 

 yellow T. 



Examples of nitro dyes are given below: 



AURANTIA 



Michrome No. 4. Molecular weight 456. An acid dye. Solu- 

 bility at i^° C: water o-i%, absolute alcohol 0-55%. 



NO2 NO2 



I L 



02N^^^\-N=<^>=N0 . ONH4 

 NO2 NOs 



MARTIUS YELLOW 



Michrome No. 170. Molectdar weight 251. An acid dye. 

 Solubility at 15° C; water 1-25%, absolute alcohol nil. 



0-NH4 

 NO2 



