Formula

C27H22O17.

Derivation

Tannic Acid is obtained by exposing powdered galls to a damp atmosphere for several days, when sufficient ether is added to form a soft paste, which is allowed to stand for twenty-four hours. It is then subjected to pressure as quickly as possible, and the mass again treated with ether, to which 1/16 of its bulk of water has been added; this is allowed to stand as before, and is again subjected to pressure. The expressed liquids are now combined and allowed to evaporate spontaneously; then, by the aid of a little heat, brought to a syrupy consistence, when it is dried on plates in a hot air chamber, at a temperature not exceeding 212° F. Pure tannic acid is solid, uncrystallizable, either white or slightly yellowish, inodorous, astringent to the taste, but without bitterness, and with an acid reaction. It is obtained in the form of vesicular masses, or thin, glistening scales, or in the shape of fine threads of a pseudo-crystalline appearance. Tannic acid exists also in rhatany, catechu, and other vegetable astringents, as it is their chief principle.

Medical Properties And Action

Tannic Acid is considered to be the most active of all vegetable astringents and styptics, and especially powerful on albumen, gelatin and fibrin. It is very soluble in water, and less so in alcohol and ether. Taken internally it produces no nausea, is perfectly safe, and its use may be continued for a long time without any ill effects. It may also be administered before and after meals, at all times, and be combined with many other remedies, such as iron, cod-liver oil, bitters, etc. Like gallic acid, it is capable of taking oxygen even from the blood globules, when in contact with alkalies.

It constringes the tissues, temporarily decreasing their vascularity, and causing contraction of their blood vessels. It arrests secretion and condenses relaxed and feeble tissues. When mixed with blood, it forms a clot rapidly on account of coagulation of the albumen.

Tannic acid is converted into gallic acid in the blood, by absorbing oxygen from the red corpuscles; this absorption does not occur in the stomach.

Tannic acid unites with albumen, fibrin and gelatin, forming insoluble tannates, thus preserving the parts beneath from the influence of irritating agents until resolution occurs.

Its solution reddens litmus paper, and it is decomposed and entirely dissipated when thrown upon red-hot iron.

Listerine is one of the best solvents for tannic acid. One ounce of listerine will dissolve half an ounce of tannic acid.

Therapeutic Uses

Internally it is administered in hemorrhages of the lungs, stomach, kidneys or uterus, chronic bronchial catarrh, phthisis, after softening has taken place, intermittent fever, whooping-cough, chronic diarrhoea, diseases of the genitourinary' organs, dyspepsia, diphtheria, nervous diseases, etc. Externally it is applied to hemorrhages and profuse secretions, mercurial salivation, diseases of the eye, nasal polypus, gonorrhoea and gleet, bed-sores, relaxation of uvula, skin diseases, ulcers, etc.

Dose

Of tannic acid, gr. j to in pill.

Dental Uses

In dental practice tannic acid is a valuable agent for local use in the treatment of such diseases as mercurial stomatitis, ulceration of the gums and mucous membrane of the mouth, hypertrophy of the gums, hemorrhage following the extraction of teeth and wounds of mucous membrane, fungous growth of pulp, sensitive dentine, sponginess of the gums, for the temporary relief of odontalgia, disease of the antrum. In mercurial salivation tannic acid, in the form of powder, moistened with water, will render the spongy gums firmer and more comfortable, causing contraction of the vessels and checking a tendency to absorption and the consequent loosening of the teeth. A strong solution of tannin in alcohol is beneficial in obtunding the sensitiveness of dentine, or the tannin may be in the form of a powder, combined with morphine and creasote. Tannic acid, in the form of a paste or ointment, made by rubbing two scruples of tannin with twenty drops of glycerine, and then with an ounce of lard, makes a good astringent application. A gargle composed of tannic acid and glycerine is a useful application for abrasions caused by artificial teeth and other irritants. A preparation known as Elixir of Vitriol and Tannin, saturated solution, is a powerful astringent and hemostatic when applied to bleeding surfaces, fungous growths, etc.

An English preparation known as Styptic Colloid, is a saturated solution of tannin and gun cotton, and is highly recommended for its styptic and deodorizing properties, as it solidifies blood and albumen by mere contact, and can be applied directly by means of a camel's-hair brush, or, mixed with an equal quantity of ether, in the form of spray. No irritation follows its use, and for hemorrhage from the extraction of teeth, or, in the treatment of necrosed or carious maxillary bones, it is very efficient. Cold or warm water will not dissolve it; but an ether and alcohol solution may be used to remove the dressing.

Tannic acid, as an internal remedy, has also been successfully administered for checking hemorrhage after tooth-extraction. Dr. W. L. Roberts says: Tannic acid, administered internally, in proper doses, will stop, I believe, any case of such hemorrhage in from thirty minutes to one and one-half hour's time. He recommends three grains of tannic acid in one-third glass of water, giving as a dose two teaspoonfuls of the solution every five minutes until three doses are taken; then two teaspoonfuls every fifteen minutes if required. Dr. Roberts further says, that such treatment has never failed him.

A styptic and antiseptic cotton can be prepared by saturating purified cotton with tannic acid, 5 parts; carbolic acid, 4 parts; alcohol, 50 parts. The cotton should be dried and preserved airtight.