Tannic acid is a determined cast of tannin, a type of polyphenol. Its frangible acidity (pKa roughly 6) is suitable to the numerous phenol groups in the structure. The chemical formula in behalf of commercial tannic acid is often foreordained as C76H52O46, which corresponds with decagalloyl glucose, but in act it is a hodgepodge of polygalloyl glucoses or polygalloyl quinic acid esters with the digit of galloyl moieties per molecule ranging from 2 up to 12 depending on the spy start euphemistic pre-owned to extract the tannic acid. Commercial tannic acid is normally extracted from any of the following works parts: Tara pods (Caesalpinia spinosa), gallnuts from Rhus semialata or Quercus infectoria or Sicilian sumac leaves (Rhus coriaria).

According to the definitions provided in alien references such as international pharmacopoeia, Provisions Chemicals Codex and FAO-WHO tannic acid monograph just tannins sourced from the above-mentioned plants can be considered as tannic acid. Sometimes extracts from chestnut or oak wood are also described as tannic acid but this is an false work of the term. It is a yellow to insight brown amorphous powder.