THE CLASSIFICATION OF DYES 171 



page 

 XANTHENE 178 



Basic. Pyronine G 



Acid. Eosin Y, erythrosine B, phloxine, fast acid 

 violet A2R 



AZINE AND RELATED DYES (quinone-imine dyes) 179 



Oxazine 180 



Basic. Brilliant cresyl blue, Nile blue A, 

 gallamine blue, coelestine blue, 



gallocyanine. (The three last- 

 named are partly acidic.) 



Thiazine 180 



Basic. Thionine, azure C, azure A, azure 

 B, methylene blue, new methyl- 

 ene blue, methylene green, tolu- 

 idine blue 



Azine 181 



Basic. Neutral red, safranine O, mauveine, 

 amethyst violet, Janus green B 



(contains also an azo chromophore) 

 Acid. Azocarmine G, induline (nigrosine) 



THE TRIARYLMETHANE DYES 



The basic triarylmethane dyes, like basic dyes in general, are 

 used for colouring chromatin. Crystal violet is one of the best 

 dyes for chromosomes (p. 225). Methyl green is particularly 

 valuable in mixtures with the basic xanthene dye, pyronine G, 

 because it is possible to arrange the proportions in such a way that 

 DNA is coloured green (or blue), and RNA red (p. 230). Dahlia is 

 a useful vital dye for various cytoplasmic inclusions. 



Basic fuchsine can be converted by sulphurous acid to a colour- 

 less substance that becomes coloured in the presence of aldehydes. 

 This forms the basis of certain important histochemical tests 

 (p. 308). 



Acid fuchsine is one of the best dyes for mitochondria (p. 241), 

 and it can also be used for the differential colouring of collagen, 

 though other acid dyes of the same group — methyl blue, aniline 



