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Methylene Blue

Methylene Blue

Class: Thiazin
Ionisation: Basic

Chemical structure of Methylene Blue

Common Name: Methylene blue
Suggested Name: Methylene blue
Other Names:

Swiss blue

C.I. Number: 52015
C.I. Name: Basic blue 9 Solvent blue 8
Color: Blue
Solubility Aqueous: 3.55%
Solubility Ethanol: 3.55%
Absorption Maximum: 661 (Aldrich) 664-666 (Conn) 668, 609 (Merck) 665 (Gurr)
Empirical Formula: C16H18N3SCl
Formula Weight: 319.9


Methylene blue is a very commonly used dye. It stains nuclei blue and is often used for that purpose. Following "ripening", a process involving atmospheric, or chemical, oxidation and the production of the three strongly metachromatic dyes Azure A, B, and C. This solution is called polychrome methylene blue and is very valuable for staining rapid frozen sections. Due to its strong metachromatic staining properties, it can be used for the demonstration of mucins, cartilage, mast cells, etc. A comparison of these dyes shows the relationship clearly.


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