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Methyl Blue

Methyl Blue

Ionisation: Acid

Common Name: Methyl blue
Suggested Name: Methyl blue
Other Names:

Cotton blue Helvetia blue

C.I. Number: 42780
C.I. Name: Acid blue 93
Color: Blue
Solubility Aqueous: Soluble
Solubility Ethanol: Soluble
Absorption Maximum: 607 (Conn) 596 (Gurr)
Empirical Formula: C37H27N3O9S3Na2
Formula Weight: 799.8 (Conn) 698 (Gurr)


This dye and water blue are the constituents of aniline blue WS. Any of the three will generally be found suitable for staining collagen in Masson's trichrome and Mallory's method for connective tissue. It is a constituent of Mann's methyl blue eosin method.

Note that Conn and Gurr give different structural formula for this dye. It may well be that two different compounds are sold under this name. Note also that Gurr does not give CI numbers or names, and these data are reliable only for the Conn formula.


  1. R. D. Lillie.
    Conn’s Biological Stains
    Williams & Wilkins, Baltimore, MD., U.S.A.
  2. Edward Gurr, 1971
    Synthetic dyes in biology, medicine and chemistry
    Academic Press, London, England.