(_Acidum Aceticum._)
(_e Ligno Destillatum._)
_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. │ │ │ │ │Grains of│
│ │ │ │ │ │ Sub- │
│ │ │ │ │ │carbonate│
│ │ │ │ │ │ of Soda │
│ │ │ │ │ │saturated│
│ │ │ │Percentage│ │ by 100 │
│ │Acetometer│Specific│ of real │Equivalents│grains of│
│ │strength. │Gravity.│ Acid. │in Minims. │ 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.