What is a white substance extracted from the lichen, Iceland moss (Cetraria Islandica). It consists of several ingredients, among which is cetraric acid, a white, crystalline, bitter substance called?

cetrarin — A white substance extracted from the lichen, Iceland moss (Cetraria Islandica). It consists of several ingredients, among which is cetraric acid, a white, crystalline, bitter substance. (Webster's 1913.)

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