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Sudan IV

Sudan IV

Class: Azo
Ionisation: Lysochrome

Chemical structure of Sudan IV

Common Name: Sudan IV
Suggested Name: Sudan IV
Other Names:

Scarlet R or red Scharlach R Biebrich scarlet R

C.I. Number: 26105
C.I. Name: Solvent red 24
Color: Red
Solubility Aqueous: Insoluble
Solubility Ethanol: Insoluble
Absorption Maximum: 522-529 (Conn) 513-515 (Gurr) 520, 357 (Aldrich)
Empirical Formula: C24H20N4O
Formula Weight: 380.5


Sudan IV is a lysochrome (fat soluble dye) predominantly used for demonstrating triglycerides in frozen sections, but it may also stain some protein bound lipids in paraffin sections. It is less popular than oil red O as it has a more orange shade.

Compare this dye to the other common lysochromes sudan III, oil red O and sudan black B.

Gurr notes that a purified form of this dye has the name "Biebrich scarlet R". It should not be confused with the water soluble dye which is much more commonly referred to as Biebrich scarlet. This latter dye is not a lysochrome, but is used as a plasma stain in trichrome techniques.


  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.
  3. Aldrich chemical catalogue, 1992
    Aldrich Chemical Company, Milwaukee, WI, USA.