Gallic acid is an important component of iron gall ink, the standard European writing and drawing ink from the 12th to 19th centuries, with a history extending to the Roman empire and the Dead Sea Scrolls. Pliny the Elder (23-79 AD) describes the use of gallic acid as a means of detecting an adulteration of verdigris and writes that it was used to produce dyes. Galls (also known as oak apples) from oak trees were crushed and mixed with water, producing tannic acid. It could then be mixed with green vitriol (ferrous sulfate) — obtained by allowing sulfate-saturated water from a spring or mine drainage to evaporate — and gum arabic from acacia trees; this combination of ingredients produced the ink.
Gallic acid was one of the substances used by Angelo Mai (1782–1854), among other early investigators of palimpsests, to clear the top layer of text off and reveal hidden manuscripts underneath. Mai was the first to employ it, but did so "with a heavy hand", often rendering manuscripts too damaged for subsequent study by other researchers.
Gallic acid was first studied by the Swedish chemist Carl Wilhelm Scheele in 1786. In 1818, French chemist and pharmacist Henri Braconnot (1780–1855) devised a simpler method of purifying gallic acid from galls;gallic acid was also studied by the French chemist Théophile-Jules Pelouze (1807–1867), among others.
The name is derived from oak galls, which were historically used to prepare tannic acid. Despite the name, gallic acid does not contain gallium.
Gallic acid is found in a number of land plants, such as the parasitic plant Cynomorium coccineum,the aquatic plant Myriophyllum spicatum, and the blue-green alga Microcystis aeruginosa.Gallic acid is also found in various oak species,Caesalpinia mimosoides,and in the stem bark of Boswellia dalzielii,among others. Many foodstuffs contain various amounts of gallic acid, especially fruits (including strawberries, grapes, bananas),as well as teas,cloves, and vinegars.Carob fruit is a rich source of gallic acid (24-165 mg per 100 g).
Post time: Feb-23-2021