vulgo, Pyroligneous Acid.
The acetic acid from wood has been very generally introduced to supersede the use of distilled vinegar for the purposes of Medicine and the Arts.[[333]] It is at length found to be capable of such complete separation from all foreign matter as to afford a perfectly pure acetic acid, invariable in its acidifying power, and immutable in its chemical properties. In justice to the skill and industry of Messrs. Beaufoy and Co. of South Lambeth, I beg to state that I have examined various specimens of this acid from their manufactory, and that I find it free from those impurities which have hitherto constituted an insuperable objection to its introduction into the Materia Medica. The purified Pyroligneous acid, manufactured by this company, and sold under the name of “Improved Distilled Vinegar,” is perfectly free from any unpleasant taste, as well as colour and sediment; and it forms a limpid and colourless solution with ammonia. The common distilled vinegar of the shops varies essentially in strength as well as purity, differing in acidifying power from 30 to 40 per cent. in value: it is sometimes 7 degrees, and at others less than 5, by the Revenue Acetometer;[[334]] and hence has arisen the difficulty of procuring an uniform article for medical application, a difficulty which the introduction of the pyroligneous acid seems calculated to overcome, as it may be procured from the manufacturers of any degree of concentration,[[335]] from 6 degrees of the Acetometer, or 2·826 per cent. of real acetic acid to 130 degrees, or 61·49 per cent. of acid; and even of still higher strength if required; their common, or Proof acid is about equivalent in strength to that of the best Malt Vinegar, of which 100 grains will saturate 14½ grains of crystallized Sub-carbonate of Soda, and consequently contains 4·73 per cent. of real acid, and will require at least one half part of water to reduce it to the strength of the best common distilled vinegar. It is found that acetic acid of 45 per cent. real acid, or of 95° of acetometer strength, dissolves Camphor and the Essential Oils very readily.
The “Acidum Aceticum Fortius,” which is now introduced into the Materia Medica of the London College, is directed to have a specific gravity of 1·046.[[336]] It is exactly six times the strength of Proof vinegar, or the strong Malt vinegar manufactured, but it requires to be diluted with nine times its weight of water to reduce it to the strength of the ordinary samples of distilled vinegar. Mr. Phillips states, that he has not met with acetic acid of greater specific gravity than 1·043,[[337]] being five times the strength of vinegar of specific gravity 1·009.[[338]] The strongest acid that can be procured is the Glacial acid, which exists in a crystallized state under 50° Fah. It contains 79 per cent. of real acid, and is consequently of the strength of 167·5 of the Acetometer. If this acid be kept perfectly still, it may be reduced several degrees below its crystallizing point in a fluid state, when the slightest agitation of the vessel instantly occasions it to solidify. It will greatly facilitate our inquiries into the strength of different samples of acetic acid to know, that the representative numbers of acetic acid and pure white marble coincide on the scale of equivalents; it therefore follows that the weight of marble dissolved by a hundred grains of any acetic acid, will at once represent the percentage of real acid in such a sample.
The Impure Pyroligneous acid, as it first comes over, contaminated with Tar, has, it is said, been very successfully employed as a lotion in Lepra, scrophulous ulcerations, chronic inflammation of the eyes, and edges of the eye-lids, and for promoting digestion of irritative ulcers, or those connected with carious bone. It has also been injected into sinuses to produce healthy discharge and adhesive inflammation.[[339]] M. Monge discovered that this acid has the property of preventing the decomposition of animal substances; it is sufficient to plunge meat for a few moments in this acid, even slightly empyreumatic, to preserve it as long as you please. “Putrefaction,” it is said, “not only stops but retrogrades.” To the empyreumatic oil a part of this effect has been ascribed, and hence has been explained the agency of wood smoke in the preservation of tongues, hams, herrings, &c.
Acidum Acetosum Forte, E. Acidum Aceticum. D.
Radical Vinegar.
The process for this preparation has not retained its place in the London Pharmacopœia, as it is now universally superseded by the Acetic acid distilled from wood. Since however it possesses peculiar chemical habitudes, it claims some notice in this work. The concentrated acid obtained from the decomposition of acetic salts, by the action of sulphuric acid, is pungent, acrid, and volatile, and when heated with free access of air, it takes fire very readily. Its solvent powers are much greater than those of distilled vinegar; it is capable of dissolving camphor, resins, and essential oils[[340]] copiously, but they are precipitated by dilution; it combines with alcohol, and forms a species of ether; with water it unites in any proportion, heat being evolved by the mixture. Gold, platinum, glass, and earthenware, can alone retain this acid without being corroded. It blisters the skin immediately.
I shall conclude this article by the introduction of a Table, which I have constructed with considerable care, for the use of the practical Chemist. The accuracy of the results may be depended upon, since it has been tested by several different modes of enquiry. The Medicinal Dynameter will give the equivalents in any other denomination that may be required.
| A Table exhibiting the acetometer strengths, specific gravities, percentage of real acid, equivalent value, and saturating power, of the more important preparations of Acetic Acid. | |||||
|---|---|---|---|---|---|
| ACIDS. | Acetometer strength. | Specific Gravity. | Percentage of real Acid. | Equivalents in Minims. | Grains of Sub-carbonate of Soda saturated by 100 grains of acid. |
| Acetum Destillatum | 5·9° | 1·005 | 2·80 | 810 | 8·58 |
| D° | 6° | 1·006 | 2·826 | 803 | 8·66 |
| D° | 7° | 1·007 | 3·42 | 663 | 10·48 |
| D° | 10° | 1·009 | 4·73 | 480 | 14·5 |
| Acetum (Proof) | 10° | 1·014 | 4·73 | 480 | 14·5 |
| Acid Acetic: Fort. | 50° | 1·043 | 23·67 | 96 | 72·5 |
| Acid Acet: Fort. P. L. | 60° | 1·048 | 28·43 | 80 | 87 |
| Acid: Acet: Fort. | 75° | 1·059 | 35·475 | 64 | 108·75 |
| Acid: Acetic, D. Acid: Acetos: Fort. E. | 145° | 1·070 | 68·5 | 33·1 | 210·25 |
| Acid: Acetic: Fort. (Glacial.) | 167.5° | 1·063 | 79 | 28·6 | 242·875 |
The reader will observe an anomaly with regard to the specific gravity of the acid of 145 of the acetometer, when compared with the glacial acid. The fact is, that by diluting this latter preparation with a small portion of water we augment its specific gravity, a circumstance peculiar to this acid.