Quercitannic acid is one of the two forms of

tannic acid Tannic acid is a specific form of tannin, a type of polyphenol. Its weak acidity ( pKa around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46, which correspon ...

found in

oak bark Tanbark is the bark of certain species of trees, traditionally used for tanning hides into leather. The words " tannin", "tanning", " tan," and "tawny" are derived from the Medieval Latin ''tannare'', "to convert into leather." Bark mills ar ...

and leaves. The other form is called gallotannic acid and is found in oak galls. The quercitannic acid molecule is also present in

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. It was formerly called Dutch pink, English pink, or Italian pink. The name is a shortened fo ...

, a yellow dye obtained from the bark of the Eastern black oak (''Quercus velutina''), a forest tree indigenous in North America. It is described as a yellowish brown amorphous substance. In 1838,

Jöns Jacob Berzelius Baron Jöns Jacob Berzelius (; by himself and his contemporaries named only Jacob Berzelius, 20 August 1779 – 7 August 1848) was a Swedish chemist. Berzelius is considered, along with Robert Boyle, John Dalton, and Antoine Lavoisier, to be ...

wrote that quercitannate is used to dissolve morphine. In 1865 in the fifth volume of "A dictionary of chemistry", Henry Watts wrote :

It exhibits with
ferric In chemistry, iron(III) refers to the element iron in its +3 oxidation state. In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) denoted by Fe3+. The adjective ferric or the prefix ferri- is often used to s ...

salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively ...
the same reactions as gallo
tannic acid Tannic acid is a specific form of tannin, a type of polyphenol. Its weak acidity ( pKa around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46, which correspon ...
. It differs however from the latter in not being convertible into
gallic acid Gallic acid (also known as 3,4,5-trihydroxybenzoic acid) is a trihydroxybenzoic acid with the formula C6 H2( OH)3CO2H. It is classified as a phenolic acid. It is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants ...
, and not yielding
pyrogallic acid Pyrogallol is an organic compound with the formula C6H3(OH)3. It is a water-soluble, white solid although samples are typically brownish because of its sensitivity toward oxygen. It is one of three isomers of benzenetriols. Production and reac ...
by dry distillation. It is precipitated by sulfuric acid in red flocks. ( Stenhouse, Ann. Ch. Pharm. xlv. 16.)
According to Rochleder (ibid lxiii. 202), the
tannic acid Tannic acid is a specific form of tannin, a type of polyphenol. Its weak acidity ( pKa around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46, which correspon ...
of black tea is the same as that of oak-bark.

In 1880, Etti gave for it the molecular formula C₁₇H₁₆O₉. He described it as an unstable substance, having a tendency to give off water to form

anhydride An organic acid anhydride is an acid anhydride that is an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the pa ...

s (called

phlobaphene Phlobaphenes (or phlobaphens, CAS No.:71663-19-9) are reddish, alcohol-soluble and water-insoluble phenolic substances. They can be extracted from plants, or be the result from treatment of tannin extracts with mineral acids (tanner's red). The nam ...

s), one of which is called ''oak-red'' (C₃₄H₃₀O₁₇). For him, it was not a glycoside. In Allen’s "Commercial Organic Analysis", published in 1912, the formula given was C₁₉H₁₆O₁₀. Other authors gave other molecular formulas like C₂₈H₂₆O₁₅, while another formula found is C₂₈H₂₄O₁₁. According to Lowe, two forms of the principle exist – one soluble in water, of the formula C₂₈H₂₈O₁₄, and the other scarcely soluble, C₂₈H₂₄O₁₂. Both are changed by the loss of water into oak red, C₂₈H₂₂O₁₁. Quercitannic acid was for a time a standard used to assess the phenolic content in

spice A spice is a seed, fruit, root, bark, or other plant substance primarily used for flavoring or coloring food. Spices are distinguished from herbs, which are the leaves, flowers, or stems of plants used for flavoring or as a garnish. Spices a ...

s, given as ''quercitannic acid equivalent''.Government standards for spices. Journal of the American Pharmaceutical Association, Volume 12, Issue 12, pages 1091–1094, December 1923,

References

{{reflist Tannins