• Webster's Revised Unabridged Dictionary
    • n Indoin (Chem) A substance resembling indigo blue, obtained artificially from certain isatogen compounds.
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Century Dictionary and Cyclopedia
    • n indoin A blue flocculent precipitate obtained when propiolic acid in sulphuric-acid solution is treated with reducing agents such as metallic iron, zinc, or copper. It differs from indigo in not easily yielding a sulphonic acid on heating.
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