188 



Biological Stains 



assumed that this dye is not soluble in alcohol. This is not true, 

 however. 



A typical absorption curve of eosin Y is given in graph 2, Fig. 

 24, in which it is compared with the similar spectral data for eosin 

 B and ethyl eosin. 



Like fluorescein, eosin Y shows greenish yellow fluorescence, 

 especially in alcoholic solution. This fluorescence is visible in 



.6- 



9.5 



>-.4 



H 



(/) 



Z 

 UJ 



o 



O 



-I 



o 

 0.2 



.1- 



400 



.3- 



420 



440 



460 



480 500 



520 



540 



)" 



Fig. 24. Spectral curves of three eosins: 

 Eosin B. 2. Eosin Y. 



3. Ethyl eosin. 



ordinary light, but although quite strong, "is not so pronounced nor 

 visible in such great dilution as in the case of fluorescein. It is 

 interesting that in this series of fluoran derivatives, tinctorial 

 power increases but fluorescence decreases with the ascending 

 members of the series; thus the erythrosins are less fluorescent than 

 eosin, while phloxine and rose bengal show scarcely any fluorescence 

 in ordinary light. In spite of the marked fluorescence of eosin Y, 

 it does not seem to have been suggested as a fluorochrome. 



