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Webster 1913 Edition

Noun.

(Chem.)

A dyestuff resembling alizarin, found in madder root, and extracted as an orange or red crystalline substance.

purpurin ‎(countable and uncountable, plural purpurins)

A red anthraquinone dye, extracted from madder, that is used as a biological stain
(biochemistry) A protein of the lipocalin family
A brownish or deep red decorative glass used in ancient times