Phenyl Methane Dyes 153 



One comparatively recent complaint concerning certain samples 

 of basic fuchsin relates to their behavior in staining tubercle bac- 

 teria by the acid-fast technic. It has been claimed that with cer- 

 tain samples of the dye these organisms show a tendency to de- 

 colorize partially or wholly, thus resulting in poorly stained cells 

 that tend to appear as a string of beads. This has proved a 

 difficult complaint to investigate, because consistent results are 

 not obtained by different investigators. In fact, Yegian and 

 Porter (1944) have shown that a normally staining culture may be 

 converted into one which is not acid-fast or which shows beaded 

 staining by improper methods of smearing on the slide. This 

 observation makes it appear doubtful whether the complaints in 

 question may or may not be due to variations between the different 

 lots of fuchsin. 



In general it can be stated, that in spite of all variations re- 

 ported, the standardization of this dye seems to have been accom- 

 plished in a practical way, even if there is still much to be learned 

 about it from a theoretical standpoint. 



Nl2 ACID FUCHSIN C. I. NO. 692. 



Synonyms: Fuchsin S, SN^ SS, ST y or S III. Acid magenta. 



Acid ruhin. 



{An acid dye; absorption maximum: pararosanilin 5J!^0~5J^3, 



rosanilin 5J^3-5Jf6) 



This dye owes its acid character to the fact that it is a sulfonated 

 derivative of basic fuchsin. Acid fuchsins are ordinarily rather 

 complex mixtures. As there are four primary basic fuchsins pos- 

 sible, according to the degree of methyl substitution, and as each 

 may yield at least three different compounds on sulfonation, fully 

 a dozen acid fuchsins are theoretically possible, and samples are 

 hardly to be expected which are not mixtures of several. 



The generally accepted formula of one of the homologs present 

 in acid fuchsin, namely the di-sodium salt of rosanilin trisulphonic 

 acid, is: 



SOs-Na 



/ 

 CH3 /-\_NH2 



H2N_/~\_C SO3 



\_/ / 



/ /-\_NH2 



NaSOs \_/ 



C2oHi7N309S3Na2; Mol. Wt. 585.534 



The bond connecting one of the sulfonic groups with an amino 

 group attached to a different benzene ring is assumed to exist in 



