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Eosin Y

Eosin Y

Class: Fluorone
Ionisation: Acid

Chemical structure of Eosin Y

Common Name: Eosin Y
Suggested Name: Eosin Y ws
Other Names:

Eosine Yellowish Bromoeosine Tetrabromofluorescein

C.I. Number: 45380
C.I. Name: Acid red 87
Color: Red
Solubility Aqueous: 40%
Solubility Ethanol: 40%
Absorption Maximum: 515-518 (Conn) 517 (Gurr) 514 (Aldrich)
Empirical Formula: C20H6O5Br4Na2
Formula Weight: 691.9


Eosin Y is the most common counterstain to alum hematoxylin in the Hematoxylin and Eosin method (H&E). It stains satisfactorily from both aqueous and ethanolic solutions. It is one of the dyes in Papanicolaou's EA solutions for staining exfoliative cytology for cervical cancer screening. It can be used to make Romanowsky stains. It is widely used in numerous procedures. It is strongly fluorescent, but this property is hardly ever used.

The free radical, eosinol Y is made by treating the dye with hydrochloric acid. It is sometimes called Eosin Y, spirit soluble. Eosinol Y is soluble in ethanol and slightly soluble in xylene, but not in water, and is useful for staining difficult tissues.


  1. R. D. Lillie.
    Conn’s Biological Stains
    Williams & Wilkins, Baltimore, MD., U.S.A.
  2. Susan Budavari, Editor,
    The Merck Index, Ed. 12
    Merck & Co., Inc., Whitehouse Station, NJ, USA
  3. Edward Gurr, 1971
    Synthetic dyes in biology, medicine and chemistry
    Academic Press, London, England.
  4. Aldrich chemical catalogue, 1992
    Aldrich Chemical Company, Milwaukee, WI, USA.