PART III.

Acids. — Acidum Aceticum.

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free the acetic acid; which must necessarily come over in aconcentrated form, as the acetate does not contain much water,and the greater part of the water of the sulphuric acid is re-tained by the sulphate of potass which is formed in the retort.The Edinburgh process is that of Badollier, an apothecary ofChartres ', with the substitution of sulphate of iron for sul-phate of copper. The affinity of the sulphuric acid of thesulphate of iron to the oxide of the acetate of lead, assisted bythe heat, decomposes the acetate, and the sulphuric aciduniting with the lead, the acetic acid is disengaged, and distilsover. The dried state of the salts enables the acid to be ina concentrated form. 2 The process of the Dublin College isthe best; the acid obtained being stronger, not contaminatedwith any metallic impregnation, and free from sulphurousacid, a small portion of which the other generally contains. 3

Qualities. — Acetic acid has a grateful, fragrant, pungentodour; a very sour acrid taste; and, when applied to the skininflames it and raises a blister. It is limpid, colourless, highlyvolatile, and if much concentrated, takes fire when heated in theopen air. The sp. grav. of the strongest that can be procuredis 1-063; in which state it contains 100 parts by weight of realacid and 14'78 of water. 4 It becomes solid and crystallizesat 38 3 of Fahrenheit, liquefying again at 40°; is capable ofoxidizing iron, zinc, copper, nickel, and tin; combines withalkalies, earths, and metallic oxides, forming acetates ; dissolvesresins, gum-resins, camphor 5 , and volatile oils : and combineswith alcohol, which, when aided by heat, it converts into aspecies of ether. With water it unites in any proportion, andduring the mixture heat is evolved. From the experimentsof Gay Lussac 100 parts of pure acetic acid appear to con-sist of 50-224 of carbon, 5-629 of hydrogen, and 44-147 ofoxygen.

Medical properties and uses. — Acetic acid is stimulant andrubefacient. It is principally employed as a refreshing scent,in syncope, asphyxia, and nervous head-achs; and for obviat-ing the unpleasant smell of the confined air of crowded as-semblies and of the sick-room. It is, also, an excellent

1 Annates de Chimie, xxxvii. 3.

s The process of the edition of the London Pharmacopoeia of 1787, for obtainingthis acid by the simple distillation of dried subacetate of copper, afforded a muchstronger acid than either of these processes. An excellent acetic acid is obtainedby decomposing the superacetate of lead at once, by means of sulphuric acid;putting into the retort, before distilling, a small portion of oxide of manganese, asdirected by M. Baup. Vide Joum. de Pharm. Dec. 1816.

3 It may be completely freed from this acid by redistilling it from black oxideof manganese mixed with a small portion of carbonate of potass. Alc/iolson'sJournal, xiii. 42. 4 Ann. de Chim. lxviii. 88.

5 Henry's aromatic vinegar is a solution of camphor, and some essential oil inacetic acid.

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