It dissolves the vegetable inspissated juices, and several of the gummy resins, and extracts the virtues of sundry plants in tolerable perfection; but at the lame time its acidity makes a notable alteration in them, or superadds a virtue of a different kind. Some drugs, however, for particular purposes, it excellently assists or coincides with, as garlic, squills, am-moniacum: and in many cases, where this acid itfelf is principally depended on, it may be ad-vantageously impregnated with the flavour of certain vegetables: molt of the odoriferous flowers impart to it their fragrance; and the blue, bright red, and some others, tinge it at the same time of a fine purplish or red colour.

It unites, like the mineral acids, with rectified spirit of wine, into what is called adulcified liquor, provided the vinegar has been highly concentrated. On distilling the mixture with a boiling heat, a large proportion of a subtile fluid is obtained, similar in its general properties to the aether prepared with the other acids (a).

It mingles equally with blood and its serum, and with most of the fluids of animals; not thickening or coagulating them, like the acids of the mineral kingdom; but tending rather, as Boerhaave juftly observes, to attenuate and resolve coagulations. It is likewise, when taken internally, less stimulating than the mineral acids, and less disposed to affect: the kidneys * (b).

This mild unctuous acid is a medicine of great use in the different kinds of inflammatory and putrid distempers, both internal and external. It is one of the most certain antiphlo-giflics and sudorifics in high fevers, and one of the best preservatives against pestilential and other putredinous contagions. Fainting, vomiting, lethargic and hysteric paroxyfms, are likewise frequently relieved, by vinegar, applied to the mouth and nose, or received into the stomach: lethargic persons are often found to be excited more effectually by vinegar blown into the nose, than by the far more pungent volatile spirits. Boerhaave observes, that this acid counteracts, in a peculiar manner, the effects of spirituous liquors.

(a) M. le Compte de Lauraguais, Hift. Acad. Par. 1759.

* (b) It is less liable to undergo changes in the first pas-sages than the native vegetable acids, which have yet to go through the process of fermentation. Cullen.

The daily use of vinegar, with food, is salu-tary in hot bilious dispositions, and where there is a tendency to inflammation or putrefaction. It is prejudicial to children, to aged, hysterical, and hypochondriacal persons, in cold pale phlegmatic habits, where the vessels are lax, the circulation languid, and the power of diges-tion weak. It tends in all cases, if used freely, to prevent corpulence; Hoffman (a) suspects that it produces this effect by impeding the formation of chyle, or destroying the union of the unctuous and serous fluids of which chyle is composed; an effect common to all acids, as appears from their coagulating milk and artificial emulsions. I have known great corpulence reduced by the liberal use of vinegar, which is the acid commonly employed for this purpose, but not with impunity; diseases suc-ceeding, which eluded the power of medicines, and proved at length fatal.

Combinations of vinegar with different earthy bodies differ in virtue according to the nature of the earth. A solution of the aluminous earth in this acid is strongly styptic; of vegetable earths, or magnesia alba, bitterish and gently purgative: both these solutions are milder, and less ungrateful, than thole of the same earths made in the mineral acids, and though as yet unknown in practice, certainly deserve to be introduced. Solutions of different animal and the calcareous mineral earths are bitterish and subaustere, in various degrees; and supposed to act as mild resolvents, sub-astringents, or diaphoretics.

(a) Philosophia corp. human, morbosi, par. iii. cap. 3. § 7.

Combinations of vinegar with fixt alkaline salts, are useful aperients, diuretics, and cathartics. I have known two drams of the alkali, dissolved in as much vinegar as was sufficient to saturate it, occasion ten or twelve copious watery stools, and a plentiful discharge of urine, without griping or fatiguing the patient. A mixture of alkali and distilled vinegar, evaporated to* a dry salt, is kept in the shops; purified to perfect whiteness, by gentle fusion and solution in water *: this preparation is given in doses of ten or twenty grains as a mild aperient, and to a dram or two as a purgative and diuretic.

It is difficult, in the common way of managing the process, to hit the exact point of saturation between the acid and the alkali. After fourteen parts of distilled vinegar have been gradually poured upon one part of the salt, the addition of a little more of the acid will occasion no further effervescence while the mixture is cold; but if well heated and stirred, the effervescence begins again, and continues till four or five parts of fresh acid have been added: on exhaling the aqueous fluid, the remaining dry salt will generally still raise an effervescence with fresh vinegar, and require two or three parts more of the acid to render it completely neutral. There is, therefore, this advantage, in reducing the salt to a dry form, that the perfect neutralization is obtained with greater certainty than when the ingredients are barely mixed together. The purification of the dry salt, or separation of its oil, is intended to render it fitter for weak stomachs, on which it would not fit so easily in its common impure state; though the medicine, thus purified, is in some particular cases less to be depended upon than the oily salt. It may be observed, that the imperfection of the oily salt, which the purification is designed to remedy, does not depend upon the oil as such, but on its receiving some degree of burnt taint from the too strong heat commonly employed in the evaporation, and may therefore be effectually prevented by the prudent use of a water-bath. A test of the purity of the salt is its perfect solubility in rectified spirits of wine, without any refiduum.

* Sal diureti-cus. Terra foliatatartari, & arcanum tartari, vulgo. Kali aceta-tum Ph. Lond.

Alkali fixurn vegetable a-cetatum, vul-go. Tartarum regeneratum, Ph. Ed.

Aqua Ammonias ace-tatae Ph. Lond.

Spiritus Min-dereri Ph. Ed.

Combinations of vinegar with volatile alkaline salts, commonly made with distilled vinegar added gradually to the salt till the effer-vefcence ceases, scarcely yield any solid salt, the saline matter evaporating with the watery fluid, or even before it: on distilling the mixture in a retort, a salt sometimes concretes about the sides of the receiver, but liquefies again as the vessels grow cold. These mixtures have little purgative virtue, but operate powerfully as aperients; by urine, if the patient walks about in the cool air; by perspiration or sweat, if kept warm in bed. They are principally made use of in this last intention, in doses of half an ounce: and as they act without irritation, they have place in inflammatory cases, where the warm fudorifics, if they fail of exciting a sweat, aggravate the distemper.

Great care ought to be taken in the neutralization of this liquor, which is very difficult to be hit exactly by the common method. The best way of judging of the saturation is, by trying the liquor from time to time with certain coloured vegetable juices, or on paper stained with them. A thick writing paper may be stained pale blue on one side with the blue preparation of archil commonly called lacmus; and pale red on the other side by a mixture of the same infusion with so much dilute spirit of salt as is just sufficient to redden it. If a small flip of this paper be dipt occasionaliy into the liquor to be tried, or a drop of the liquor applied upon both sides of the paper; the red side turns blue so long as any of the alkali remains unsaturated; the blue side turns red when the acid begins to prevail; and no change at all is produced when the saturation is complete. This way of trial I strongly recommend to the apothecary in making all neutral mixtures, as he may thus at all times find, expeditiously and with certainty, the exact point of neutralization, which is not perhaps possible to be found by the common way of judging from the effervescence: how precarious and indeterminate a mark the cessation of effervescence is, is apparent from the observations on the preceding preparation. Where lacmus cannot be procured, the paper may be coloured with the juices of certain blue flowers, as violets, iris, cyanus, etc. or with the blue juice pressed out from scrapings of the cortical part of common radish roots: with thefe juices it is sufficient to stain the paper on one side, this one colour discovering both acidity and alkalescence, the former changing it red, and the latter green; but the change produced by liquors slightly alkaline is much less conspicuous than that produced by the same liquors on the red paper above-mentioned, which is therefore to be preferred.