Skip to main content

Azure A

Azure A

Class: Thiazin
Ionisation: Basic

Chemical structure of Azure A

Common Name: Azure A
Suggested Name: Azure A
Other Names:

Methylene azure A

C.I. Number: 52005
C.I. Name:
Color: Blue
Solubility Aqueous: Soluble
Solubility Ethanol: Soluble
Absorption Maximum: 625-632 (Conn) 633 (Aldrich) 620-634 (Merck) 632 (Gurr)
Empirical Formula: C14H14N3SCl
Formula Weight: 291.8


Azure A is formed by the oxidation of Methylene blue and is strongly metachromatic. It is used in making azure eosin stains for blood smear staining. Compare the formula of the three azures and methylene blue.


  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