PHLOXINE C. I. NO. 7 74 OF 778 



Synonyms: Erythrosin BB. New pink. 



(An acid dye; absorption maximum of C. I. No. 778 about 537.5.) 



If fluorescein is prepared from dichlor or tetrachlor-phthalic 

 acid, instead of from simple phthalic acid, its derivatives have a 

 deeper, more pleasing shade than the ordinary eosins. Of these 

 derivatives, phloxine contains four bromine atoms and thus cor- 

 responds to Eosin Y. It contains two or four chlorine atoms ac- 

 cording to whether it is prepared from the dichlor- or the tetra- 

 chlor-phthalic acid; and there are two Colour Index numbers cor- 

 responding to these two compounds, the former being No. 774, the 

 latter No. 778. It is uncertain which is desired by the biologist. 



The dichlor compound is : 



Br Br 



NaO I I 



O /\_0 



Br I Br 



Cl_/\_ 



COOXa 



CI 



Unna uses phloxine in combination with several other acid dyes 

 in studying the process of chromolysis. The dye has seldom been 

 specified for biological work; yet there is reason to believe that it is 

 a more valuable stain than anyone has realized in the past, and that 

 it has frequently been used under other names. 



Chamberlain (19'24 page 58) mentions having used it successfully 

 in place of Magdala red in staining algae. His original technic 

 called for Magdala red; but true Magdala red does not serve his 

 purposes. Inasmuch as erythrosin (see above) was evidently sold 

 in the past as Magdala red and Chamberlain can duplicate his 

 original results with phloxine, the chances are that some of the 

 Magdala red formerly available was either phloxine or else that 

 phloxine and erythrosin give similar results by Dr. Chamberlain's 

 technic. 



It has, furthermore, been found that no sample of eosin at 

 present available of either domestic or foreign origin works in the 

 well-known Mallory eosin-methylene-blue stain ; but after investi- 

 gating both phloxine and rose bengal. Dr. Mallory reports the 

 former to be "the best eosin I have yet found for use in the 

 eosin-methylene blue stain for parafin sections of tissues fixed 

 in Zenker's fluid."* Here again is a case where phloxine apparently 

 was obtained before the war under an incorrect name and the incor- 

 rect name used in the publication of a well-known technic. 



*Quoted from personal letter. 



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