Tannic Acid: Properties, Structure, Test, & Uses

Tannic acid is a type of polyphenol and is also called Aecidium tannic or Gallo tannic acid. Tannic acid is a weak acid since it contains several phenol groups. Tara pods, Quercus infect Oria, gallnuts from Rhus simulate, and Sicilian Sumac leaves are all-natural sources. Tannic acid has the chemical formula C₇₆H₅₂O₄₆. Condensed tannins and hydrolysable tannins are the two primary forms of Aecidium Tinicum. The word tannin comes from the Celtic name for oak tree, which was traditionally used to make leather.

Key Terms: Tannic Acid, polyphenol, Weak Acid, Tannins, Chemical Formula, Alkaloid Precipitation, Gymnosperms

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Properties of Tannic Acid

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The following are the Properties of Tannic Acid:

• Tannic acid has the chemical formula C₇₆H₅₂O₄₆.
• Tannic acid has a molecular weight of 1701.19 g/mol.
• It has a density of 2.12 g/cm³
• It decomposes over 200 °C and has the same melting point
• Tannic acid's pKa is around 6.

Read More: Dehydration of Alcohol

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Structure of Tannic Acid

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The structure of Tannic Acid is shown below:

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Tests for Tannic Acid

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Tannins can be analysed using one of three methods: precipitation of alkaloids or proteins, interaction with phenolic rings, or depolymerization.

• Alkaloid Precipitation: Cinchonine, caffeine, strychnine, and quinine are alkaloids that precipitate tannins and polyphenols. The quantitation technique makes use of this characteristic.
• Goldbeater’s Skin Test: If ox or goldbeater's skin is dipped in HCl acid, rinsed in water, immersed in tannin solution for 5 minutes, washed in water, and then treated with 1% FeSO4 solution, it creates a blue-black colour if tannin is present.
• Ferric Chloride Test: In general, ferric chloride (FeCl3) is used to test for phenolics. The powdered plant leaves of the test plant (1.0 g) are then weighed into a beaker, followed by 10 ml of distilled water. The mixture is then boiled for five minutes. Then two drops of 5% FeCl3 are added. The presence of tannins is shown by the formation of a greenish precipitate. Alternatively, a part of the water extraction is diluted with distilled water in a 1:4 ratio, and a few drops of 10% ferric chloride solution are added. Tannins are represented by a green or blue colour.

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Difference between Tannic Acid and Tannin Acid

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Following are the Differences between Tannic Acid and Tannin Acid

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Occurrence of Tannic Acid

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Following is the information regarding the Occurrence of Tannic Acid:

• Tannins are found throughout the plant kingdom in various species. 
• They are commonly seen in both angiosperms and gymnosperms. 
• Mole investigated tannin distribution in 44 monocotyledon groups (Cronquist) and 180 dicotyledon families. 
• Tannin-free species have been found in the majority of dicot families (which are tested by their ability to precipitate proteins). 
• Actinidiaceae, Aceraceae, Bixaceae, Anacardiaceous, Myricaceae for dicot, Grossulariaceae, Najadaceae, and Typhaceae for monocot are the best-known families with all the species examined possessing tannin.
• Tannin was found in 73 per cent of the oak species examined (N = 22) in the Fagaceae family. 
• In the Mimosaceae, only 39 per cent of the species studied (N = 28) have tannin, while the Solanaceae rate lowers to 6 per cent and the Asteraceae rate reduces to 4 per cent.
• There are no tannin-rich species in a few families, including Cucurbitaceae, Boraginaceae, and Papaveraceous.
• The majority of the plentiful polyphenols are considered to be condensed tannins, which are present in almost all plant groups and can account for up to 50% of the dry weight of the leaf.
• Tannins in tropical woods are more cathartic than gallic, as opposed to gallic tannins found in temperate woods.
• Because of pests, birds, and other diseases, the bioavailability of other tannins contained in plants may be reduced.

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Uses of Tannic Acid

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There are multiple uses for Tannic Acid. Some of them are:

• Tannic acid is used in the manufacture of albumin tannate, which is an antidiarrheal medication.
• It also has a wide range of applications in the food business, where it may be used as a colour stabiliser, flavour enhancer, and clarifying agent.
• It can be employed in the dyeing of cellulose fibres.
• This acid can be used to prevent corrosion while preserving ferrous metal artefacts.
• It is also employed as a coagulant in the production of rubber.
• This acid is used to provide yarn or polyamide carpets with anti-staining qualities.
• Tortoiseshell may be created by combining it with gelatine and albumin.
• It can be used as a reagent in analytical chemistry.

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Health Hazards of Tannic Acid

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Tannic acid has the potential to harm the respiratory tract, eyes, skin, and gastrointestinal tract. It also causes discomfort, irritability, impaired vision, and flushing. When this acid enters the body through the skin, it can produce irritation and redness. When consumed, it can cause diarrhoea, nausea, and vomiting.

Read More: Sulphur Cycle

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Things to Remember

The following are some important points:

• Tannic acid may be found in nutgalls, which are created by insects on the twigs of some oak trees.
• Tannic acid, purified, is occasionally used as medication.
• Tannic acid is used to treat a variety of ailments, including cold sores, diaper rash, heat rash, and others, although there is no clear scientific evidence to support these claims.
• Tannic acid is used as a flavouring ingredient in foods and beverages.
• Tannic acid is used in the production of ointments and suppositories, tanning hides, making ink, and killing dust mites on furniture.