1911 Encyclopædia Britannica/Orcin
ORCIN, a dioxytoluene, C6H3(CH3)(OH)2 (1 : 3 : 5), found in many lichens, e.g. Rocella tinctoria, Lecanora, and formed by fusing extract of aloes with potash. It may be synthesized from toluene; more interesting is its production when acetone dicarboxylic ester is condensed with the aid of sodium. It crystallizes in colourless prisms with one molecule of water, which redden on exposure. Ferric chloride gives a bluish-violet coloration with the aqueous solution. Unlike resorcin it does not give a fluorescein with phthalic anhydride. Oxidation of the ammoniacal solution gives orcein, C28H24N2O7, the chief constituent of the natural dye archil (q.v.). Homo-pyrocatechin is an isomer (CH3 : OH : OH＝1 : 3 : 4), found as its methyl ether (creosol) in beech-wood tar.