What is a reddish brown or violet crystalline substance, C16H12O6, got from hematoxylin by partial oxidation, and regarded as analogous to the phthaleins called?

hematein — A reddish brown or violet crystalline substance, C16H12O6, got from hematoxylin by partial oxidation, and regarded as analogous to the phthaleins. (Webster's 1913.)

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