As early as 1866, tannic acid, gallic acid, wood spirit, acetic acid, essential oil and eucalyptol were produced from various species of eucalyptus, and researches made by Australian chemists, notably by Messrs.
That obtained from the sessilefruited oak is richer in tannic acid than that yielded by Q.
The astringent principle is a peculiar kind of tannic acid, called by chemists quercitannic, which, yielding more stable compounds with gelatine than other forms, gives oak bark its high value to the tanner.
The cups are the most valuable portion of the valonia, abounding in tannic acid; immature acorns are sometimes exported under the name of "camatina."
This substance differs from the mucins by being precipitated by tannic acid but not by acetic acid, and being endowed with a higher proportion of sulphur.
Since the introduction of iron ships teak has supplanted oak, because it contains an essential oil which preserves iron and steel, instead of corroding them like the tannic acid contained in oak.
Pomegranate root, or, better, the sulphate of pelletierine in dose of 5 grains with an equal quantity of tannic acid, may be used to replace the male fern.
In the surgical treatment of haemorrhage minor means of arresting bleeding are: cold, which is most valuable in general oozing and local extravasations; very hot water, 130° to 160° F., a powerful haemostatic; position, such as elevation of the limb, valuable in bleeding from the extremities; styptics or astringents, applied locally, as perchloride of iron, tannic acid and others, the most valuable being suprarenal extract.
The treatment of strychnine poisoning is to immediately evacuate the stomach with a stomach-pump or emetic, chloroform being administered to allay the spasms. If the patient can swallow, draughts of water containing tannic acid may be given.
The dressing of the pelt or skin that is to be preserved for fur is totally different to the making of leather; in the latter tannic acid is used, but never should be with a fur skin, as is so often done by natives of districts where a regular fur trade is not carried on.
The results of applying tannic acid are to harden the pelt and discolour and weaken the fur.
TANNIN, or Tannic Acid, the generic name for a widely disseminated group of vegetable products, so named from their property of converting raw hide into leather.
Common tannin, or tannic acid, C, 4 H, 0 0 9.2H 2 O, occurs to the extent of 50% in gall-nuts, and also in tea, sumach and in other plants.
Tannic acid is official in both the British and United States Pharmacopoeias.
From tannic acid is also made gallic acid, which resembles tannic acid but has no astringent taste.
In the intestine tannic acid controls intestinal bleeding, acting as a powerful astringent and causing constipation; for this reason it has been recommended to check diarrhoea.
Tannic acid is largely used in the treatment of various ulcers, sores and moist eruptions.
For bleeding haemorrhoids tannic acid suppositories are useful, or tannic acid can be dusted on directly.
Tannic acid is absorbed as gallic acid into the blood and eliminated as gallic and pyrogallic acids, darkening the urine.
This power is possessed alike by a glass of brandy, by solution of lime, soluble salts of zinc, copper, or silver, by tannic and gallic acids, as well as vegetable juices and extracts which contain them.
Tannic acid, for instance, precipitates codeine as a tannate, salts of many of the heavy metals form precipitates of meconates and sulphates, whilst the various alkalis, alkaline carbonates and ammonia precipitate the important alkaloids.
Brazilwood (Caesalpinia echinata), valuable for its timber and colouring extract, and "roco" (Bixa orellana), the "urucn" of Brazil which furnishes the anatto of commerce, are widely distributed in central and southern Colombia, and another species of the first-named genus, the C. coariaria, produces the "divi-divi" of the Colombian export trade - a peculiarly shaped seed-pod, rich in tannic and gallic acids, and used for tanning leather.
Unlike tannic acid, gallic acid does not precipitate albumen or salts of the alkaloids, or, except when mixed with gum, gelatin.
With phosphorus oxychloride at 520° C. gallic acid yields tannic acid, and with concentrated sulphuric acid at 100°, rufigallic acid, C14H808, an anthracene derivative.
Substances containing tannic or gallic acid turn black when compounded with a ferric salt, so it cannot be used in combination with vegetable astringents except with the infusion of quassia or calumba.
- Tannic acid is present in small quantities in the great majority of plants, but in notable quantity in gall-nuts, oak bark, bearberry leaves, rhatany root, catechu, kino, red gum, bael fruit, logwood and witch hazel, all of which are largely used as medicines.
In these the variety of tannic acid is not exactly the same, but although there are slight chemical differences, they all possess the power of tanning raw hides and of preserving albuminous tissues.
The action of tannic acid is strictly local, and depends upon its power of precipitating albumen and of destroying germs. It thus acts as an astringent on all mucous membranes.