The acetous acid, as offered to us by the spontaneous changes, in consequence of fermentation, contains a large proportion of mucilage. This is separated by distillation, or more certainly by freezing; but the mode which chemists have preferred is uniting it with copper or lead, and distilling it from these bases. In this way it undoubtedly acquires new properties, and, in the modern nomenclature,merits the title of acetic acid. It is then highly fragrant and volatile, confined only by the purest gold or crystal; and, in this state, combined with aromatics, it becomes a very useful and safe prophylactic, a preservative from the infection of putrid fevers. See Infection.

Acetous acid is formed of the vegetable principle carbon, united with hydrogen and oxygen; and this compound is not only the result of the gradual decomposition of saccharine matter in fermentation, but is produced more rapidly by the action of nitric acid on many vegetable bodies; this acid supplying the oxygen, which is otherwise absorbed from the atmosphere. Though very commonly a vegetable matter, its immediate principles are sometimes unexpectedly combined, and we discover it in animal and mineral productions. It will be obvious that its acid is destroyed by earths and alkalis, but the tartarous neutrals are also decompounded by it. Vinegar dissolves sugar, mucilages, and gums, and mixes in every proportion with alcohol. It softens gum resins; and, triturating with vinegar, renders gum ammoniac and asafoetida more readily soluble in water. It dissolves the peculiar acrimony of the alkalescent plants, and consequently forms the best menstruum for squills, colchicum, etc. Medicated vinegars are very common, and foreign pharmacopoeias offer a considerable number. See Acetum.

Acetated potash was formerly styled terra foliata tartari, and tartarum regeneratum: a more modern appellation, scarcely disused, is the diuretic salt. It is a deliquescent salt, and not adapted either for powder or pills. It may be decomposed by tamarinds and almost every acid, even the citric and phosphoric, and by almost every variety of neutral, either alkaline, earthy, or metallic. It is soluble in an equal weight of water at 60. The preparation is difficult and uncertain.

The acetated natron has been styled the sal vegeto minerale; but it has never been employed as a medicine, and even its chemical properties have not been properly investigated.

The acetated ammonia was formerly styled Mindere-rus spirit. It is a deliquescent salt, and we receive it usually in a liquid form, but seldom of a certain strength; though a medicine given in doses of half an ounce or an ounce does not require any minute accuracy. When procured in a solid state, its crystals are long, slender, flatted, and of a pearly white colour: they melt at 170, and sublime at 250°. It is decompounded by fixed alkalis, lime water, the acids of lemon, phosphorus, and tartar, as well as the three strong mineral acids; by-alum, Epsom salt, nitrated silver, muriated iron, acetated lead, and the vitriols.

The acid of tartar; in common language, is the cream of tartar, which is the deposition from wine, purified from the oily and colouring matter, and crystallized in irregular masses, formed by a confused mixture of needle-like crystals. In this state it is gritty between the teeth, and of a harsh unpleasant sourness; soluble in sixty times its weight of cold, and half the quantity of boiling water. It is not, however, a pure acid, but contains from twenty-three to thirty-three hundredths of potash. The purification of tartar is kept a secret; but it is probably effected by the admixture of pipe clay, since, by repeatedly washing the crystals of tartar, an earth of this kind remains. It has been a pharmaceutical problem to render cream of tartar more soluble in water, and borax has been employed for the purpose; but the latter is by this means decomposed.

The real acid of tartar is not deliquescent, and for this reason it is entitled the dry powder of lemonade. It is not the reputed salt of lemons, which is in reality the salt of wood sorrel, though it is supposed to add not a little to the bulk of this expensive preparation. The powder of lemonade is prepared by mixing a drachm of the essential salt of tartar with six drachms of sugar, and a drachm of the oleosaccharum of oil of lemons. It is obvious that alkalis and earths will destroy the acid, but the eyes and claws of crabs are not purely calcareous; and though with chalk it forms an indissoluble salt, with magnesia, on the contrary, it forms a soluble one,

But whatever its affinities are in the moist state, in a dry powder they are not exerted; and the acid of tartar forms the basis of a salt, from which the carbonic acid is readily separated in solution. We hinted at this mixture when we spoke of the exhibition of this acid; and the preparation consists of one drachm of the acid, with two of kali, or three of natron, adding a little sugar according to the taste. This acid decomposes all the salts, whose basis is the vegetable alkali. It decomposes also muriated lime and barytes, nitrated silver, muriated iron, acetated and nitrated mercury, acetated lead, and all the vitriols, as well as soaps of every kind.

The tartarised kali is the tartarised tartar of former authors, the soluble tartar of pharmaceutists, and is usually prepared by saturating the superabundant acid of the cream of tartar by adding kali. It is soluble in alcohol, and in four parts of cold water. It is decomposed by all acids and by acid fruits; by lime, barytes, strontia,and magnesia; partly by the sulphats of potash, soda, alumine, and magnesia; and by the muriats of barytes, lime, and ammonia; by cubic nitre, and the most common metallic salts.

The tartarised soda has been styled sal Rupellensis; but as the crystals of tartar are saturated with the soda, it is obvious that this is properly a triple salt, and has been justly called by the Edinburgh college, tartris po-tassae and sodae. Its crystals are very large and regular, in the form of prisms, of eight nearly equal sides, divided longitudinally almost to their axis. It is bitter, soluble in about five parts of water, effloresces, but does not deliquesce, in the air, and consists of about 54 parts of tartrite of potash and 46 of tartrite of soda. All acids decompose it; even the acid fruits, alum, muriated lime, Epsom salt, nitrated mercury, acetated lead, and the vitriols, have the same effect.