Eosin

Chinese drawing
MFA# 2018.450

Description

Eosin

A red crystalline dye composed of the potassium, sodium, or lead salt of tetrabromofluorescein. First discovered by Heinrich Caro, a German chemist, in 1874, eosin was initially used as an acid dye for producing a blood red color in textiles (silk, wool, paper, leather, and cotton). It has also been used as a cosmetic colorant, a colorant in red inks and an iridescent ceramic glaze. In the late 19th and early 20th century, eosin was used as a red paint pigment, even though it is not permanent and discolors rapidly in sunlight. Alcoholic solutions have a strong green autofluorescence. Starting in 1876, eosin earned a significant place in histological staining. Current practice uses a mixture of hematoxylin and eosin on tissue where it stains cytoplasm (pink) and nuclei (dark blue). Eosin also products a deep red color with red blood cells.

Absorption spectrum

Synonyms and Related Terms

• Eosin Y: tetrabromofluorescein; eosin yellowish; Pigment Red 90; CI 45380; D&C Red No.22; Acid Red 87; Solvent Red 43; éosine (Fr.); eosina (Esp., Port.); bromeosin; bromofluoresceic acid;
• Eosin B: di-bromo derivative; eosin bluish; CI 45400; D&C Red No.21; Acid Red 91; saffrosine; eosine scarlet; imperial red; geranium lake; eosine yellowish
• Food dye version is now called erythrosine or Red 3
• Others: Eosin G; Eosin A

Risks

• Causes skin irritation.
• Fades rapidly in sunlight.
• Delasco: SDS

Physical and Chemical Properties

• Soluble in ethanol.
• Insoluble in water (potassium and sodium salts of eosin are water soluble).
• Maximum absorption wavelength = 520 nm.
• Maximum emission wavelength = 540 nm.
• Composition = C20H8O5Br4 (mol. wt. = 647.9 g/mol)
• CAS = 548-26-5
• Melting Point = 300 C

Resources and Citations

• M.Ballard (ed.), Important Early Synthetic Dyes. Chemistry, Constitution, Date, Properties. Conservation Analytical Laboratory, Smithsonian Institution, 1991.
• R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966
• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
• Monona Rossol, The Artist's Complete Health and Safety Guide, Allworth Press, New York, 1994
• The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 3639
• Encyclopedia Britannica, http://www.britannica.com Comment: "Chemical Compound."(Accessed 12 May 2004).
• Website: www.probes.com/handbook/sections - gives absorption max=524 and emission max=544
• Website: member.pgonline.com/~bryand/dyes/45380.htm - absorption max = 516
• Colour Index International online at www.colour-index.org Comment: discoverer and date
• Sigma Dyes, Stains and Natural Pigments, Infrared Library, Nicolet, 1991-1995 Comment: OMNIC: formula= C20H8O5Br4, CAS= 548-26-5
• The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
• Wikipedia: Eosin Accessed Feb.2026
• Hektoen International From silks to science: the history of hematoxylin and eosin staining
• CHSOS: Spectra (Reflectance, XRF, Raman, FTIR) for PR90 Eosin Y