Take of acetate of soda, two pounds; sulphuric acid, nine ounces; distilled water, nine fluid ounces: add the sulphuric acid, previously mixed with the water, to the acetate of soda put into a glass retort, then distil the acid in a water bath Care should be taken not to augment the heat towards the end.

Dublin.

"Take of acetate of potassa, one hundred parts; sulphuric acid, fifty-two parts. Pour the acid into a tubulated retort: then add to it in small portions and at different times, the acetate of potassa, allowing the mixture to cool after each addition; finally, with a moderate heat, distil the acid until the residue be dry.

"The specific gravity of this acid is to that of distilled water, as 1074 to 1000."

Acidum aceticum forte, Edin. Strong Acetic Acid,

"Take of dried sulphate of iron, one pound; acetate (super-acetate) of lead, ten ounces. Rub them together; then put them into a retort, and distil in a sand-bath with a moderate heat, as long as any acid comes over."

Syn. Acide Acetique (F.), Essigaure (G.), Azynzuur (Dutch), Acido acetico (I.).

These processes furnish the same acid as that which is contained in distilled vinegar, but it is completely free from extractive and mucilage, and is much stronger. In the processes of the London and the Dublin Colleges, the sulphuric acid, by reason of its superior affinity for soda and for potassa, decomposes the acetates, and sets free the acetic acid; which being volatile, must necessarily come over in a concentrated form, as the acetates contain little or no water, and much of water of the sulphuric acid is retained by the sulphates which remain in the retort.1 The Edinburgh process is that of Badollier, an apothecary of Chartres2, with the substitution of sulphate of iron for sulphate of copper. The affinity of the sulphuric acid of the sulphate of iron for the oxide of the acetate of lead, assisted by the heat, decomposes the acetate, the sulphuric acid uniting with the oxide of lead, and the acetic with the oxide of iron; from which, however, it is" again disengaged and distils over. M. Lowitz recommends a bisulphate to be used.

The dried state of the salts enables the acid to be obtained in a concentrated form.3 The processes of the London and Dublin colleges are the best; the acid obtained being stronger, not contaminated with any metallic impregnation, and free from sulphurous acid, a small portion of which the acid formed by the Edinburgh process generally contains.

Qualities. - Acetic acid has a grateful, fagrant, pungent odour, a very sour and acrid taste; and when applied to the skin, inflames it and raises a blister. It is limpid, colourless, and highly volatile; its odour is pungent and refreshing, its taste acrid; and, if much concentrated, it takes fire when heated in the open air; and burns with a white light. The sp. grav. of that procured by the London process, is 1.048, in which state it contains, in 100 parts by weight of real acid, 30.7 of water. It becomes solid and crystallizes at 28° of Fahrenheit, liquefying again at 40°, and is also beautifully crystallized when compressed with a force of 1100 atmospheres.4 It is capable of oxidizing iron, zinc, copper, nickel, and tin; combines with alkalies, earths, and metallic oxides, forming acetates; dissolves resins, gum resins, camphor1, and volatile oils; and combines with alcohol, which, when aided by heat, it converts into a species of ether. With water it unites in any proportion, and during the mixture heat is evolved : a mixture of 15 parts of it with 85 parts of water, is equal in strength to distilled vinegar.

From the experiments of Gay Lussac, 100 parts of pure acetic acid, free from water, or as it exists in dry acetate of potassa, appear to consist of 50.224 of carbon, 5.629 of hydrogen, and 44.147 of oxygen : or of 4 equivalents of carbon = 24.48 + 3 of oxygen = 24 + 3 of hydrogen - 3, making the equivalent = 51.48. But the strength of acetic acid can only be determined by its specific gravity. Thus, at 60° Fahr. acid of 1.06296 specific gravity contains of acid 1 atom + 1 atom of water, making the equivalent 60.48. That of the London college contains 30.8 of anhydrous acid + 69 2 of water in 100 parts.

1 The composition of the acetate of soda is 1 eq. of acid = 51.46 + 1 soda = 31.3 + 6 water = 54 - equiv. 136.76. The primary form of its crystal is an oblique rhombic prism.

2 Annates de Chimie, xxxvii. 3.

3 The process of the edition of the London Pharmacopoeia of 1787, for obtaining this acid by the simple distillation by dried acetate of copper, afforded a much stronger acid than either of these processes. An excellent acetic acid is obtained by decomposing the acetate of lead at once, by means of sulphuric acid; putting into the retort, before distilling, a small portion of oxide of manganese, as directed by M. Baup. Vide Journ. de Pharm. Dec. 1816.

4 Philosophical Trans, for 1826. Part III. art xviii.

Tests. - One hundred grains of this acid saturate eighty-seven grains of crystallized carbonate of soda.2 Its specific gravity is 1.048. Its purity is ascertained by diluting it with water, and testing as for distilled vinegar.

Incompatibles. - Alkalies and their carbonates, alkaline earths and their carbonates.

Medical properties and uses. - Acetic acid is stimulant and rubefacient. It is principally employed as a refreshing scent, in syncope, asphyxia, and nervous headachs; and for obviating the unpleasant smell of the confined air of crowded assemblies and of the sick room. It may be used as a counter-irritant, when applied to the skin, in cynanche tonsillaris, croup, and other internal inflammations. It is, also, an excellent application to warts and corns, which it seldom fails to remove; but in applying it, care must be taken to avoid eroding the surrounding skin. It is a useful and powerful substitute for a blister, when the effect of such an application is required to be rapidly obtained.

Officinal preparation.-Acidum Aceticum Camphoratum, E. D. Acetum Cantharidis, L. Potassae Acetas, L. Plumbi Acetas, L. Oxymel, L.