Quercitron

Quercitron is a yellow natural dye obtained from the bark of the Eastern Black Oak (Quercus velutina), a forest tree indigenous in North America. The name is a shortened form of quercicitron, from Latin quercus, oak, and citron, lemon, and was invented by Edward Bancroft (1744–1821), who by act of parliament in 1785 was granted special privileges in regard to the importation and use of the substance. The dyestuff is prepared by grinding the bark in mills after it has been freed from its black epidermal layer, and sifting the product to separate the fibrous matter, the fine yellow powder which remains forming the quercitron of commerce. The ruddy-orange decoction of quercitron contains quercitannic acid, whence its use in tanning, and an active dyeing principle, quercitrin, C₂₁H₂₀O₁₂. The latter substance is a glycoside, and in aqueous solution under the influence of mineral acids it yields quercetin, C₁₅H₁₀O₇, which is precipitated, and the methyl-pentose rhamnose.