Sex. Syst. Monoecia, Polyandria.
(Galla; Tumor ramuli a Cynipe; Gallae tinctoriae excitatus, L.—Gallae: Excrescences, E.—Galls, the excrescences formed by Diplolepis Gallas tinctorium, D.)
History.—Hippocrates employed the nutgall (χηχις) as an astringent, both internally and externally. [Ed. Faes. pp. 609, 267, &c.] Dioscorides [Lib. i. cap. 146.] describes it as the fruit of the oak; and the same error is found in the works of comparatively recent writers, as of Pomet. [Hist. of Drugs, Engl. translation, 1712.]
Botany. Gen. Char.—Vide Quercus pedunculata.
Sp. Char.—Leaves ovate-oblong, sinuate-dentate, very smooth, deciduous. Fruit sessile, very long. [Olivier, Voy. dans l'Empire Ottom. t. ii. p. 64.]
Small tree or shrub, from four to six feet high. Stem crooked. Leaves on short petioles, with a few short mucronate teeth on each side. Acorn two or three times as long as the cupules.
Hab.—Asia Minor, from the Bosphorus to Syria, and from the Archipelago to the frontiers of Persia.
In general, the insects which give rise to galls are the gall-flies, constituting the genus Cynips, and forming the tribe Gallicolae (Diphlolepariae, Lat.) of the order Hymenoptera. But sometimes they are plant-lice, or Aphidii of the order Hemiptera. Thus the very astringent Chinese galls called Woo pei-tze (Fig. 285), of which I have elsewhere [Pharmaceutical Journal, vol. iio. p. 384, 1844.] given a description, are produced, as the late Mr. Double-day [Ibid. vol. vil. p. 310, 1848.] has shown, by an Aphidian.
The gall-flies (Cynips) are those by whose puncture the officinal galls are produced, and to which, therefore, our attention must be principally directed. The females of these insects are supplied with an ovipositor, called by Latreille the borer (terebra), channelled with lateral teeth.—By means of this instrument they are enabled to perforate the foliaceous or cortical parts of plants for the purpose of depositing their eggs, along with an acrid liquor, in the wound thus made. The irritation thereby produced gives rise to an influx of the juices of the plant to the wounded part, and an excrescence is formed, which is termed a gall (galla). Here the insect usually undergoes its transformations: the egg produces the larva (or maggot), which feeds on the juices of the plant, and is changed into the pupa. This afterwards becomes the perfect insect (imago), and, perforating the gall, produces a small, round hole, through which it escapes from its prison-house.
The external form and appearance of galls are very constant when formed by the same insect, on the same part of the same plant; but the galls of different species of vegetables, and of different parts of the same plants, as well as those of the same vegetable species, produced by a different insect, vary considerably. There is reason for believing that the form and appearance of the gall is determined more by the insect than by the plant; for we sometimes have on the same oak two kinds of galls, of very dissimilar appearance, produced by different insects.
Oak Galls.—Most, if not all plants, but especially the oaks, are liable to the production of galls. The oak galls vary considerably in size, shape, texture, and other properties, according to the species and part of the oak in which they grow, and the insect by whose puncture they are produced. From their fancied resemblance to nuts, apples, currants, &c, they have been respectively called, nut-galls, apple-galls, currant-galls, grape-galls, cherry-galls, artichoke-galls. [For further details respecting galls, the reader is referred to Reaumur's article on this subject, in his Mémoires pour servir à l'Histoire des Insectes, 4th. vol. iii. 1737. Also to Westwood's Introduction to the Modern Classification of Insects, 2 vols. 8vo. 1838-40.]
The largest species of British oak-galls is the oak-apple or oak sponge, produced by Cynips Quercus terminalis. They are astringent, like nutgalls.
The small round currant-galls are produced by C. Q. pedunculi. They are scattered over the rachis of the amentum, giving it the appearance of a bunch of currants.
The artichoke-gall or oak-strobile is a beautiful foliose gull, produced by C. Q. gemmae.
Galls of various species are produced on oak-leaves. One of the larger sorts is red and succulent, and has been called the cherry gall. A smaller one is called by Reaumur the currant-gall. Mr. Westwood states that the large ones (as large as a boy's marble) are formed by C. Q. folii.
The large Mecca or Bussorah galls, [See a notice of this gall, by the author, in the Pharmaceutical Journal, vol. viii. p. 422.] sometimes called Dead-sea apples, mad-apples (mala insana), or apples of Sodom (poma sodomitica), are produced on the Quercus infectoria by a species of Cynips which Mr. Westwood calls C. insana.
A very irregular, deeply-furrowed, angular gall is formed on the capsule of the Quercus pedunculata by the Cynips Quercus calycis. This is the acorn gall. It is sometimes used in Germany by dyers as a substitute for nutgalls under the name of Knoppern or Knobben. These galls appear to me to be identical with some which I have received fiom M. Guibourt under the name of gallon de Hongrie ou du Piemont. The acorn, with its capsule, is usually attached to it. A very similar shaped gall, attached by its middle to a young branch, is frequently found intermixed: this M. Guibourt calls the horned gall (galle corniculée).
Nutgalls.—The nutgalls (gallae officinorum) of commerce are produced by the Cynips gallae tinctoriae on the Quercus infectoria. Ollivier [Op. cit.] says that this insect lives on this species of Quercus only.
On the sides and at the ends of the branches and shoots of this tree, the female makes a puncture and deposits her egg. An excrescence is soon formed, within which the larva is developed, which is changed first into the pupa and then into the the imago. As soon as the perfect insect is produced, it eats its way out. If we examine those galls from which the animal has escaped, we observe externally a circular hole, of about a line in diameter, leading to a canal of from 2 ½ to 3 ½ lines long, which passes to the centre of the gall. But in those galls in which the insect has not put off its pupa state, we find neither an external hole nor an internal canal. In the imperforated gall, the part sometimes called "the kernel" is the cocoon of the insect in the pupa state (Kirby and Spence). Guibourt [Hist. Nat. des Drogues simples, 4me édit. t. ii. 1849.] states that in the immediate envelop of the central cavity of the gall he detected starch grains, and, in the exterior covering, chlorophylle and volatile oil. Guibourt has also observed, around the spherical amylaceous mass, cells serving for the respiration of the insect.
Bluish black, heavy, not yet perforated. Ph. L.
Those galls from which the insect has escaped are commonly larger, lighter coloured, and less astringent: they are termed white galls.
The nutgalls of different countries vary in their size, shape, weight, and quality of surface.
1. Levant Nutgalls (Gallae Levanticae).—These are the ordinary nutgalls of the shops. They are in general about the size of a nut, somewhat round, tuberculated or warty; whence they were formerly called spiny or prickly galls (galles à 1'épine, gallae spinosae), to distinguish them from the smooth French and other galls. They are imported from Syria and Turkey. The most esteemed Syrian galls (gallae syricae) are the produce of Mosul on the Tigris: these are the Mosul galls (gallae mossulicae). The Aleppo galls (gallae haleppenses) usually pass for Mosul galls. Tripoli galls (gallae tripolitanae) come from Tripoli (also called Taraplus or Tarabulus, whence the corrupt name of "Tarablous galls"), and are inferior to the Aleppo galls. The Turkey galls (gallae turcicae) usually come from Constantinople or Smyrna. Smyrna galls (gallae smyrnenses) are not so heavy, are lighter coloured, and contain a larger admixture of white galls than those brought from Aleppo. The galls brought from Bombay (East India galls) are probably the produce of Persia or neighbouring parts. [Mat. Indica, vol. i. p. 145.]
In commerce, three kinds of Levant galls are distinguished, viz., black or blue, green, and white; but there is no essential distinction between the first two.
α. Black or blue nutgalls (gallae nigra; seu caeruleae); green nutgalls (gallae virides).—These are gathered before the insect has escaped, and are called by the natives yerli. They vary from the size of a pea to that of a hazel-nut, and have a grayish colour. The smallest have a blackish-blue tint, and are distinguished by the name of black or blue galls; while the larger and greener varieties are called green galls. Externally they are frequently tuberculated, but the surface of the tubercles and of the intervening spaces is usually smooth. Their texture is compact, but fragile. They have no odour, but a styptic and powerfully astringent taste.
β. White galls (gallae albae).—These are for the most part gathered after the insect has escaped, and hence they are perforated with a circular hole. They are larger, lighter coloured (being yellowish or whitish), less compact, less heavy, and less astringent. They are of inferior value.
γ. The marmorine nutgalls (galles marmorines, Guibourt) of the French writers are a sort of Levant gall about the size of the black or blue galls, but without tubercles or warts. The surface, however, is dull and roughish, something like orange berries. Their shape is round, with sometimes a little elongation where the peduncle is attached.
δ. Small Aleppo nutgalls.—Occasionally there is imported from Aleppo a small sort of nutgall, called the coriander gall.
Somewhat larger than these is another sort of small Aleppo gall, called the small crowned Aleppo galls (gallae haleppenses coronatae). They are about the size of a pea, or a little larger, and crowned superiorly by a circle of points or tubercles like the fruit of the myrtle or Eugenia. Although very small, they are often perforated by a large hole, so that they must have attained their maximum size; and, therefore, are a distinct sort from the usual Aleppo kind.
Somewhat larger than these, and having a speckled surface, is a sort which I have received under the name of Turkish diamonds.
2. European Nutgalls.—Various sorts of nutgalls are produced in Europe. The Istria nutgalls are intermediate in size between the usual Levant galls and the small Aleppo sort. They are somewhat turbinate or pear-shaped, wrinkled, and usually have a short peduncle. The Morea nutgalls are about the size of the preceding. French nutgalls are spherical, very light, usually very smooth or even polished, but sometimes very slightly wrinkled. Hungarian, Italian, Bohemian, &c. nutgalls are but little known in England.
Composition.—Nutgalls were analyzed by Sir H. Davy, [Phil. Trans. for 1830.] who obtained the following results:—
|Matter soluble in water = 37; viz.||Tannin||26.0|
|Gallic acid, with a little extractive||6.2|
|Mucilage and matters rendered insoluble by evaporation||2.4|
|Carbonate of lime and saline matter||2.4|
|Matter insoluble in water (lignin)||63.0|
|Good Aleppo nutgalls||100.0|
Pelouze [Ann. de Chimie et de Physique, t. liv. p. 337.] found in 100 parts of nutgalls the following constituents: tannic acid 40.0, gallic acid 3.5, ellagic acid and insoluble matter 50, extractive colouring matter 6.5 = 100.0.
1. Tannic Acid (see p. 325).
2. Gallic Acid (see p. 326).
3. Ellagic or Bezoardic Acid (Acidum Ellagicum vel Bezoardicum), C14H2O7,3HO.—Discovered by Braconnot, who called it ellagic acid, from the French word galle spelt backwards. It is probably produced by the slow decomposition of the tannin contained in the nutgall. It is a yellowish gray insipid powder, scarcely soluble in cold water, a little more so in alcohol, but insoluble in ether. Like the tannic and gallic acids it forms a bluish black precipitate with the persalts of iron. Hot nitric acid, according to Braconnot, gives it a blood-red colour. The acid has recently acquired additional interest in consequence of the discovery by Mr. Thomas Taylor [Lond. and Edinb. Philosoph. Magazine for May 1844, and also for January 1846; and Catalogue of the Museum of the Royal College of Surgeons, published in July 1845.] (subsequently confirmed by Merklein and Wöhler [Ann. der Chem. u. Pharm. Bd. lv. S. 129, 1845.] ) that the Oriental Bezaar is an ellagic acid calculus formed in the intestines of animals (usually a species of wild goat, termed by the Persians Pasen), which feed on vegetable substances containing tannin, from which the ellagic acid is produced. Ellagic acid, therefore, must be regarded as identical with bezoarine (Bezoarstoff of John).
Chemical Characteristics.—Infusion of nutgalls reddens litmus paper, forms an inky compound (tannogallate of iron) on the addition of a sesquisalt of iron, and a yellowish white precipitate (tannate of gelatin) with a solution of gelatin. If a piece of skin, depilated by lime, be immersed in the infusion, and agitated with it from time to time, all the tannic acid is absorbed, the filtered liquor striking a blue colour (gallate of iron) with the sesquisalts of iron, but giving no precipitate with a solution of gelatin. Infusion of galls forms precipitates (metallic tannates or tanno-gallates) in many metallic solutions; it also produces a precipitate (a tannate) in aqueous solutions of the vegetable alkaloids.
|Metal.||Solution employed.||Precipitate according to [*]|
|Manganese||Neutral protochloride||Dirty yellow||0|
|Iron||Neutral protosulphate||Purple tint||0|
|Bismuth||Tartrate of bismuth and potassa||Yellow and copious||Orange.|
[* Discrepancies arise from the strength of the solutions as well as from their acid or basic diameters, so that neutral solutions should as far as possible be used.]
Physiological Effects.—As nutgalls contain a larger portion of tannic acid than any other known vegetable production, they possess in the highest degree the properties of an astringent (see vol. i. pp. 200 and 243).
Uses.—The following are the principal uses of nutgalls:—
1. As a tonic in intermittents.—Notwithstanding Poupart's favourable report of the use of galls in these cases, they scarcely deserve notice, as we have in arsenic, cinchona, and sulphate of quinia, much more effective and certain febrifuges.
2. As an astringent in hemorrhages, especially passive alvine hemorrhages.
3. In chronic mucous discharges, as old diarrhoeas.
4. As a chemical antidote (see vol. i., p. 198).—Nutgalls may be given in poisoning by ipecacuanha, emetina, the organic alkalies generally, and those vegetable productions whose activity depends on an organic alkali; as opium, white hellebore, Colchicum, nux vomica, &c. Their efficacy arises from the tannic acid, which combines with the vegetable alkali to form a tannate possessing less activity than the other salts of these bases; perhaps because of its slight solubility. Nutgalls are recommended as an antidote in cases of poisoning by emetic tartar, but I very much doubt their efficacy (see vol. i. p. 670).
5. As a topical astringent.—Nutgalls are applicable in any cases requiring the topical use of a powerful vegetable astringent. Thus, in the form of gargle, in relaxation of the uvula; as an injection, in gleet and leucorrhosa; as a wash, in flabby ulcers, with profuse discharge; prolapsus ani seu vaginae; in the form of ointment, in piles, &c.
Administration.—The dose of the powder is from ten to twenty grains. Nutgalls are also used in the form of infusion and tincture.
Roasted nutgalls (gallae torrefactae) are used in the manufacture of copying-ink (see p. 329).
Besides the following officinal formulas for the use of galls, others have been published by Mouchon. [Gaz. des Hop. Civ. et Milit. 13 Avril, 1837.]
1. INFUSUM GALLAE; Infusion of Galls.—Prepared by digesting ℨiv of coarsely powdered nutgalls in f℥vj of boiling water.—Employed as a chemical antidote and as a reagent or test (see ante, p. 324). The dose is from f℥ss to f℥ij; or, in cases of poisoning by the vegetable alkalies, f℥iv.
2. TINCTURA GALLAE, L.D. [U. S.]; Tinctura Gallarum, E.; Tincture of Galls.— (Galls, bruised, ℥v; Proof Spirit Oij. Macerate for seven [fourteen, D.] days, and filter. [Galls, bruised, ℥iv; Diluted Alcohol Oij. Macerate for fourteen days, and filter, U. S.] "This tincture may be prepared either by digestion or percolation, as directed for tincture of capsicum," E.)—A powerful astringent. Dose from fℨss to fℨij. Diluted with water, it forms a very useful and convenient astringent gargle and wash. Its principal use is as a chemical test, especially for the persalts of iron, gelatin, and the vegetable alkaloids. After it has been kept for some time its tannic acid becomes converted into gallic acid, and it then ceases to occasion precipitates in solutions of gelatin and of the vegetable alkaloids.
3. UNGUENTUM GALLAE, D. [U. S.]; Ointment of Galls.—(Galls, in very fine powder, ℨJ; Ointment of White Wax ℨvij. Mix them.)—[Galls, in powder, ℥j; Lard ℥vij. Mix them, U. S.]—Astringent. Mixed with zinc ointment it is applied to piles after the inflammatory stage is passed. The above is Dr. Cullen's formula; but Mr. B. Bell [Syst. of Surgery.] recommends an ointment composed of equal parts of powdered galls and hog's lard or butter, in external hemorrhoidal swellings. [A smoother ointment, and one which leaves no gritty, rough deposit on irritable surfaces, is prepared by adding ℨJ of Aqueous Extract of Galls to ℥j of Simple Ointment.—Ed.]
4. UNGUENTUM GALLAE COMPOSITUM, L; Unguentum Gallae et Opii, E.; Compound Ointment of Galls.—(Galls, in fine powder, ℨvj; Opium, powdered, ℨss; Lard ℥vj. Mix.—The Edinburgh College orders of Galls, in fine powder, ℨij; Opium, in powder, ℨj; Axunge ℥j.)—An excellent astringent application to blind piles (i. e. piles without hemorrhage) and prolapsus ani. The opium diminishes the pain which the galls might otherwise occasion, where the hemorrhoidal tumours are very sensible. From ℨss to ℨi of camphor is frequently added to this ointment.
5. ACIDUM TANNICUM, L.D. [U. S.]; Acidum Quercitannicum; Tannic Acid: in the impure state called Tannin, the Tanning Principle, or Materia Scytodephica (σκυτοδεφικος, belonging to curriers).—Extracted from nutgalls by ether in the percolation or displacement apparatus. [Pelouze, Ann. de Ckim. et de Physique, t. liv.] The ether employed is that of commerce (which contains about 10 per cent. of water). The tannic acid at first dissolves in the ether, but is afterwards precipitated, in the form of a thick syrup, by the water contained in the ether. The syrupy layer is to be repeatedly washed with pure ether, and afterwards evaporated in vacuo, or at a temperature not exceeding 212° F. The residue is almost pure tannic acid.
Galls, in tolerably fine powder, ℥viij; Sulphuric Ether Oiij; Distilled Water ℥v. Incorporate the water and ether by agitation, and pour the resulting solution, in successive portions, upon the galls, previously introduced into a glass or porcelain percolator. The liquid which accumulates in the lower bottle will consist of two distinct strata, the heavier of which is to be separated and evaporated to dryness, finally applying an oven heat, which, however, should not exceed 212°. From the lighter liquid the ether may be removed by distilling it by means of a water-bath, and with the aid of a Liebig's condenser.—D.
Tannic acid is a spongy, brilliant, light, odourless white, or commonly yellowish, solid. It dissolves in water, alcohol, and ether; but less so in ether than in alcohol. In the solid state it is unalterable in the air; but, dissolved in water, it absorbs oxygen, and is transformed into carbonic acid, which escapes, and gallic acid, which remains in solution: hence it should be dissolved only at the time we are about to use it.
The following are the characteristics of this substance: It has an intensely astringent taste, and produces, with a solution of gelatin, a white precipitate (tannate of gelatin); with a solution of a sesquisalt of iron, a deep blue compound (tannate of iron: see vol. i. p. 711); and with solutions of the vegetable alkalies, white precipitates (tannates) slightly soluble in water, but very soluble in acetic acid. The mineral acids also cause precipitates with concentrated solutions of tannic acid, as do the alkalies and their carbonates. Gelatinous alumina rapidly absorbs tannic acid from its solution, and forms an insoluble compound with it.
Almost colourless; its solution in water is strongly astringent; with a solution of isinglass it produces a white precipitate. In other respects it agrees with the characters assigned to gallic acid. Ph. Lond.
Tannic acid is composed of C18H8O12=C18H5O9,3HO; consequently its equivalent or atomic weight is 212. Its symbol is Tan,3HO; or Qt,3HO.
Tannic acid is employed in medicine, in chemistry, and in the arts.
Considered as a medicine, tannic acid is a powerful agent of the astringent class. As a topical remedy it is probably the most powerful of all vegetable astringents or styptics. Its chemical action on fibrine, albumen, and gelatin explains this. It is the active principle of a very large proportion of vegetable astringents (see vol. i., pp. 200 and 243). Given to a dog in doses of from 7 ½ grains to about 93 grains, it did not affect the health of the animal: it caused constipation, but its appetite remained the same. The urine gradually became darker coloured and opake, and was found to contain both gallic and pyrogallic acids and humus-like substances. The tannic acid had become converted into these bodies in its passage through the animal system. [Wöhler and Frerichs, Chemical Gazette, vol. vi. p. 231, 1848.] The gallic acid was detected by the blackish blue precipitate produced by the persalts of iron, and by no precipitate being produced with gelatin. Pyrogallic acid was detected by the bluish black precipitate produced by the protosalts of iron. On the human subject tannic acid also operates as a constipating agent when given in a sufficient dose and frequently repeated. Cavarra [Cavarra, Lond. Med. Gaz. vol. xx. p. 171, 1837.] states that 2 ½ grains taken three days successively produced this effect on himself. The remote effects of tannic acid are not so obvious, but they appear to be astringent, though in a much feebler degree. As the tannic acid becomes changed into gallic acid in its passage through the system, it is probably the latter agent which operates on remote parts as an astringent when tannic acid is administered. If this opinion be correct, tannic acid would act, as Dr. Garrod [Lancet, Dec. 30, 1848.] has suggested, less powerfully as a remote astringent than an equal weight of gallic acid. But, as a topical astringent, tannic is far more powerful than gallic acid; because its chemical reaction on albumen, gelatin, and fibrine is more energetic.
Tannic acid is used as an astringent chiefly in hemorrhages and profuse secretions; and also to constringe relaxed fibres. In hemorrhages, it has been used both topically, as a styptic (in bleeding gums, piles, and uterine hemorrhage), and remotely, as an astringent (in hemorrhage from the lungs, stomach, bowels, kidneys, and uterus). In chronic fluxes it has likewise been employed both as a topical and a remote remedy: topically in gonorrhoea, gleet, leucorrhoea, and ophthalmia; remotely in pulmonary catarrh, diarrhoea, dysentery, leucorrhoea, gonorrhoea, and cystirrhoea. To restrain the phthisical sweatiug it has been recommended by Charvet and others, and Giadorow [Annali universali. di Medicina, quoted by Dr. Dunglison, in his New Remedies, 5th edit. 1846.] states that, given in combination with opium, he cured (?) two cases of diabetes by it. To constringe fibres, it is applied to spongy gums and prolapsed bowel. As an application to sores, it has been employed by Ricord in chancres, and by Mr. Druitt [Provincial Med. Journal, Oct. 9, 1844.] in sore nipples. Dr. Scott Alison [ London Journal of Medicine, 1850.] has recently recommended its use in various other cases: as a tonic or peptic in dyspepsia; as an "histogenetic" to promote the genesis and improve the quality of the blood, in rickets, &c; as a nervine in nervous debility and languor; and to arrest or retard the growth of heterologous formations (tubercle, malignant disease, &c). It has likewise been given as an antidote to check excessive vomiting from ipecacuanha or emetina.—Tannic acid may be administered in doses of from 3 to 10 or more grains, in powder, pill, or solution. When we employ it as a remote agent, the pill-form seems to be the most appropriate mode of exhibition.—As a lotion or injection, it may be used in the form of aqueous solution containing from 4 to 6 or more grains in the fluidounce. It has also been employed in the form of ointment composed of ℨij of the acid dissolved in fℨij of distilled water and mixed with ℥xij of lard.
In chemistry, tannic acid is employed as a reagent or test. Its solution should be fresh made when used.
In the arts it serves various useful purposes. It is the active principle of the tanning substances. In the manufacture of white wines it is used to coagulate the substance called glaïadine, which is apt to excite the viscous fermentation in these wines.
6. ACIDUM GALLICUM, L. D. [U. S.]; Gallic Acid.—It is usually prepared by exposing for a long time an infusion of nutgalls to the air; removing now and then a mouldy skin which forms on the surface of the liquid. A sediment of impure gallic acid is obtained, which requires to be purified by solution in boiling water, decolorized by animal charcoal, and crystallized.
In this process the tannic acid of the nutgalls absorbs atmospheric oxygen, and is converted into gallic acid, carbonic acid, and water.
|C18H8O12||+ O4||= 2(C7H3O5)||+ 4CO2||+ 2HO|
|/ \||/ \||/ \||/ \|
|Hydrated tannic acid.||Gallic acid.||Carbonic acid.||Water.|
This process is favoured by the presence of a nitrogenized matter which acts as a ferment; and the decomposition is termed the gallic fermentation. The mouldy skin which forms on the surface is called mycoderma, and resembles mother of vinegar (see ante, p. 85 [There's no mention of mother of vinegar on page 85, but there's mentions of mycoderma. -Henriette]).
Galls, in coarse powder, lb. j; Distilled Water, as much as may be necessary. Having placed the galls in a porcelain dish, pour on as much water as will convert them into a thick paste, and keep them in this moistened condition for six weeks, at a temperature of between 60° and 70°, adding water from time to time, so as to supply what is lost by evaporation. Let the residue be boiled for twenty minutes, with forty-five ounces of water, and then placed on a calico filter. The filtered solution, on cooling, will afford a copious precipitate. Let this be drained on a calico filter, then subjected to strong expression, after having been first enveloped in blotting paper, and again dissolved in ten ounces of boiling water. When, upon ceasing to apply heat, the solution has cooled down to 80°, pour it off from the crystals which have formed, and, having washed these with three ounces of ice-cold water, dry them—first in blotting paper, and finally by a steam or water heat
By boiling the undissolved portion of the galls with forty-five additional ounces of water, filtering into a capsule containing the liquor decanted from the crystals formed in the preceding process, evaporating down to the bulk of ten ounces, and cooling to 80°, an additional quantity of the crystallized acid will be obtained.
Or: Galls lb. j; Oil of Viitiol of commerce f℥xxvj; Water Ov. ℥xiv. Steep the galls for twenty-four hours in one pint of the water, then transfer them to a glass or porcelain percolator, and pour on a pint and a half of the water in successive portions. Dilute five ounces of the oil of vitriol with an equal bulk of water, and, when the mixture has cooled, add it to the infusion obtained by percolation, stirring well, so as to bring them into perfect contact. Let the viscid precipitate which forms be separated by a filter, and to the solution which passes through, add five ounces more of the oil of vitriol, which will yield an additional precipitate. This being added to that previously obtained, let both be enveloped in calico, and subjected to powerful pressure. Dissolve the residue in the rest of the oil of vitriol, this latter being first diluted with what remains of the water; boil the solution for twenty minutes, then allow it to cool, and set it by for a week. Let the deposit which has formed at the end of this period be pressed, dried, and then dissolved in three times its weight of boiling water, clearing the solution, if necessary, by filtration, and, when it has cooled down to 80°, decant the liquid from the crystalline sediment which has formed, and wash the latter with three ounces of ice-cold water. Finally, let it be transferred to blotting paper, and, when deprived by this of adhering liquid, let it be dried perfectly, at a temperature not exceeding 212°.
The gallic acid obtained by either of the preceding processes may be rendered nearly white by dissolving it in twenty times its weight of boiling distilled water, and causing the solution to traverse a stratum of prepared animal charcoal spread upon a calico filter. When the liquid passes through colourless, it should be evaporated to one-sixth of its volume, and then suffered to cool, in order to the separation of the crystallized acid.—D.
Pure gallic acid is a colourless, crystallizable acid, with an acidulous and styptic taste. It is soluble in water, alcohol, and slightly so in ether. It produces a deep blue colour with the salts of the sesquioxide of iron, in which circumstance it agrees with tannic acid, but it differs from the latter acid in not precipitating gelatin of the salts of the alkaloids. To detect gallic acid mixed with tannic acid, the latter is to be previously removed from its solution by immersing in it a piece of skin depilated by lime. The tannic acid is absorbed. The gallic acid may then be detected by the salts of the sesquioxide of iron.
Colourless; destroyed by fire. Soluble both in water and in rectified spirit. It strikes a bluish black colour with solutions of the sesquioxide of iron; but produces no precipitate with a solution of isinglass. Ph. Lond.
It does not occasion any precipitate with the salts of the protoxide of iron. By this it is distinguished from pyrogallic acid.
Gallic acid consists of C7H3O5; hence its equivalent or atomic weight is 85. When heated to 410° or 420° F., it gives out carbonic acid, and is resolved into pyroyallic acid (C6H3O3). If this acid is heated to 480°. F., it gives out water and becomes metagallic acid (C12H3O3).
Gallic acid is employed in medicine as an astringent; but as a topical agent it is greatly inferior to tannic acid. Unlike the latter acid it causes precipitates neither in gelatinous nor in albuminous solutions: and a piece of skin does not absorb gallic acid from its aqueous solution, as it does tannic acid from its solution. Its chemical action on the constituents of the animal tissues is thus much weaker than that of tannic acid. No obvious effects result from the introduction of a few grains into the stomach. Twenty-four grains have produced a sweetish taste and a slight feeling of internal heat; but no other effect. [Chevallier, Dict. des Drogues, t. i. p. 93, Paris, 1827.] It has been administered in doses of from fifteen to thirty grains against the Taenia Solium, but without any benefit. For the reasons already stated (see ante, p. 326) it is probable that, in equal doses, it is more powerful, as a remote astringent, than tannic acid. Dr. Todd [London Medical Gazette, N. S. vol. viii. p. 101, January 19, 1849.] says that in all cases of hemorrhage, whether haemoptysis, haematemesis, haematuria, or any other form dependent on hemorrhagic tendency, he considers it to be the best styptic we possess. The dose of it is from three to ten grains or more three or four times a day. It may be used in the same forms as tannic acid (see ante, p. 326).
|C7H2O5||= C6H2O3||+ CO2|
|/ \||/ \||/ \|
|Hydrous gallic acid.||Pyrogallic acid.||Carbonic acid.|
Pyrogallic acid is a crystallizable volatile acid. It is more soluble in water than gallic acid. It produces a very intense blue colour with the salts of the protoxide of iron, and by exposure to the air it absorbs oxygen, and is converted into a dark brown substance, which is insoluble in water and alcohol.
Pyrogallic acid, in an impure form, is employed in the preparation of a hair dye and of copying ink. By the dry distillation of galls, it is obtained partly in the form of a sublimate, partly in the fluid form. The sublimate and fluid are to be dissolved in distilled water, the solution deodorized by animal charcoal, concentrated by evaporation, and then mixed with spirit of wine and some agreeable volatile oil. The resulting compound is a hair-dye, which stains the hair dark brown; and the tint is not removed by sweat or moisture. It must be cautiously applied, as it stains the hands. [Pharmaceutical Journal, vol. iii. p. 585, 1844.] Roasted nutgalls are used in the manufacture of copying ink on account of the dark colour which the pyrogallic acid produces with the sulphate of the protoxide of iron.