erythrin

from The Century Dictionary.

• noun A coal-tar color of the xanthene type, prepared by the methylation of eosin. It dyes silk a bluish red with a red fluorescence. Also called primrose.
• noun An organic principle (C₂₀H₂₂O₁₀) obtained from Roccella tinctoria, Lecanora tartarea, and other lichens, which furnish the blue dyestuff called litmus.
• noun Same as erythrite, 1.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) A colorless crystalline substance, C20H22O10, extracted from certain lichens, as the various species of Rocella. It is a derivative of orsellinic acid. So called because of certain red compounds derived from it. Called also erythric acid.
• noun (Min.) See Erythrite, 2.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun organic chemistry C20H22O10, an organic compound extracted from certain lichens, a derivative of orsellinic acid.
• noun Alternative form of erythrite.