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A brown dye obtained from the husks of walnuts, Juglans regia. Juglone also acts as a natural Herbicide, providing a plant-free region for the seed to grow.

See also Walnut shell.

Synonyms and Related Terms

5-hydroxy-1,4-naphthoquinone; CI 7550; Natural Brown 7; nucin; regianin; juglona (Esp., Port.)

Physical and Chemical Properties

  • Yellow crystals.
  • Absorption max = 520 nm
  • Soluble in chloroform, benzene, alcohol, ether.
  • Alkaline solutions turn a reddish-purple color
Composition C10H6O3
Melting Point 155 C
Molecular Weight 174.16
CAS 451-39-0

Resources and Citations

  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • John S. Mills, Raymond White, The Organic Chemistry of Museum Objects, Butterworth Heineman, London, 2nd ed., 1994
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 5282