Picric Acid

Property Data
Common name
Suggested name
Other names
C.I. number
C.I. name
Class
Ionisation
Solubility aqueous
Solubility ethanol
Absorption maximum
Colour
Empirical formula
Formula weight
Picric acid
Picric acid
Trinitrophenol
10305

Nitro
Acid
1.3%
9%
354 (Gurr), 360 (Conn)
Yellow
C6H3N3O7
229.114

Picric acid was the first synthetic dye to be made, in 1771 by Woulfe. It is now most commonly used in conjunction with acid fuchsin in the Van Gieson method which demonstrates collagen (red) in contrast to cytoplasm and muscle (yellow). It is also used, with or without other yellow acid dyes, to colour erythrocytes in trichrome methods for fibrin such as Lendrum's Picro-Mallory. It is a fixing agent and is a constituent of Bouin's fluid. It has been used as a differentiating acid in a variant of Heidenhain's iron hematoxylin, and is a trapping agent for methyl violet in the Gram Weigert stain for bacteria and fibrin.

 

Important safety note

 

Measuring picric acid safely

 

Making saturated ethanolic picric acid

 

 

Reference
R. D. Lillie.
Conn's Biological Stains
Williams & Wilkins, Baltimore, MD., U.S.A.

Edward Gurr, (1971)
Synthetic dyes in biology, medicine and chemistry
Academic Press, London, England.

Pope Sine, (2003)
Synthetic dyes
Rajat Publications, New Delhi, UK.

 


 

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