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Indigo Carmine

Dye

Indigo Carmine

Class: Indigoid
Ionisation: Acid

Chemical structure of Indigo Carmine

Common Name: Indigo carmine
Suggested Name: Indigo carmine
Other Names:

Indigocarmine

C.I. Number: 73015, 75781
C.I. Name: Acid blue 74, Natural blue 2
Color: Blue
Solubility Aqueous: 1.5% (Conn), 0.3% (Aldrich)
Solubility Ethanol: 1.5% (Conn), 0.3% (Aldrich)
Absorption Maximum: 606 (Gurr), 608 (Conn)
Empirical Formula: C16H8N2Na208S2
Formula Weight: 466.36

Description

Indigo carmine has two different CI numbers and CI names as it may be made either from synthetic indigo (CI 73015, acid blue 74) or from natural indigo (CI 75781, natural blue 2).

It was more popular in the past than at present. It has been used as a collagen stain in a Van Gieson type method giving blue collagen and is sometimes used in methods having red nuclear stains, with which it contrasts well.

It is an indicator at pH 11.5 - 14, changing from blue to yellow.

References

  1. R. D. Lillie.
    Conn’s Biological Stains
    Williams & Wilkins, Baltimore, MD., U.S.A.
  2. Green, Floyd J,
    The Sigma-Aldrich handbook of stains, dyes and indicators.
    Aldrich Chemical Company, Milwaukee, WI, USA.
  3. Gurr, Edward,
    Synthetic dyes in biology, medicine and chemistry
    Academic Press, London, UK