have basic properties. As stated above, they lack the chromophore 

 group, and hence are colorless. 



1. DI-PHENYL METHANE DERIVATIVES 



The di-phenyl methanes are of practically no biological signif- 

 icance. Only one deserves mention here. 



AURAMIN C. I. NO. 655 



Synonyms: Canary yellow. Pyoktaninum aureum. 



Pyoktanin yellow. 



CH3 CH3 



\N_/-\_C_/-\v_N/ 



/ \_/ I \_/ \ 



CH3 NHa CH3 



CI/ 



Altho of some use as a drug, auramin has little value in micro- 

 scopic technic. It has been used by Fischel, however, in the vital 

 staining of salamander larvae, and by Vinassa for staining plant 

 sections.* 



2. TRI-PHENYL METHANE DERIVATIVES 



There are two groups of tri-phenyl methanes to concern us, the 

 amino and the hydroxy derivatives. The former, which are much 

 the more numerous, are very strongly basic, thanks to the amino 

 groups, unless sulfonated like light green or acid fuchsin. The 

 rosolic acid dyes, on the other hand, are hydroxy phenyl methanes, 

 the amino groups being replaced by hydroxyl groups; they are 

 therefore acid instead of basic dyes. 



There are likewise two subdivisions of the amino derivatives, 

 the di-amino tri-phenyl methanes and the tri-amino tri-phenyl 

 methanes. These two groups are derivatives respectively of: 

 di-amino tri-phenyl methane 



H.N_/~\ H 



\_/\ / 

 C 



H.N_/— \/ \/"~\ 

 \_/ \_/ 



and tri-amino tri-phenyl methane, or pararosanilin. 



H.N /^\ H 



H.N /~\/ \/~X NH, 



The individual dyes of this series are substitution products of these 



*Literature References to the procedures mentioned in this chapter may be 

 found on pp. 110 to 128 and 138 to 145. 



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