The elements of materia medica and therapeutics: Cupri acetates. - Acetates of copper.

The elements of materia medica and therapeutics
by Jonathan Pereira, M.D. F.R.S. & L.S.
Fourth Edition, enlarged and improved, including notices of themost of the medicinal substances in use in the civilized world, and forming an Encyclopædia of Materia Medica.
Vol. I.
London: printed for Longman, Brown, Green, and Longmans, Paternoster Row.
1854.Five compounds of oxide of copper and acetic acid are known; of these, three are subsalts, and two are neutral.

Subacetates:
Trisacetate of Copper 3CuO,A,2HO
Diacetate of Copper, hydrated (blue verdigris) 2CnO,A,6HO
Subsesquiacetate of Copper, crystallised 3CuO,2A,6HO

Acetates:
Acetate, crystallised (crystallited verdigris) CuO.A.HO
Acetate, crystallised, penthydrated CuO,A,5HO

L. Gmelin enumerates, on the authority of Berzelius, another compound, the formula of which is 48CuO,A,12HO.


1. Cupri Subacetates. — Subacetates of Copper.

¹ Opera, ed. Fæs. 635, 636, aud 894.

² De Lapidibut.

³ Lib v. cap. xci.

⁴ Hist. Nat. xxxiv.History. — Hippocrates employed verdigris, which he terms [---], or rust of copper, in diseases of the eye, and as an astringent in hemorrrhoids.¹ Theophrastus,² Dioscorides,³ and Pliny,⁴ describe the method of procuring it. The Romans called it ærugo, the term by which it is now known in the Materia Medica of the London Pharmacopoeia. It is usually termed diacetate of copper; but this name is objectionable, since verdigris frequently occurs is i subsesquiacetate mixed with the trisacetate. I prefer the less precise, though more accurate term, subacetate of copper, as it includes all the subacetates composing verdigris. This is the name given by the Dublin Colleg.

Prepaeation. — At Montpelier it is thus made: — The refuse of grapes is allowed to ferment with sour wine, and is then laid in alternate strata with plates of copper: acetous fermentation takes place, and the metal become; oxidized by the combined influence of the air and acid. In about fifteen days the plates are covered with the acetate of copper: they are then wetted, and exposed for a month to the air: the acetate absorbs the water, and uniting with more oxide of copper, forms a subacetate, which is scraped off, and packed in leathern sacks for exportation. At Grenoble, verdigris is obtained by sprinkling plates of copper with ready-made vinegar. In this country it is prepared by exposing thin plates of copper to the action of acetic acid. The method now practised consists in alternating plates of copper with pieces of woollen cloth steeped in acetic acid: they gradually become corroded, and superficially covered with verdigris, which is from time to time removed, and the operation repeated as long as the plate lasts. French verdigris is imported in sacks weighing from 25 to 30 pounds.

Properties. — It occurs in masses or in powder. One variety is of a pale bluish-green colour (green verdigris); another is blue (blue verdigris). The taste is astringent and metallic; the odour is somewhat similar to, though more disagreeable than, acetic acid. Verdigris is insoluble in alcohol. Water resolves it into a soluble acetate and an insoluble trisacetate.

Characteristics. — When digested with strong sulphuric acid, it evolves acetic acid, which is readily distinguished by its odour. Heated in a ghw tube it gives out acetic acid: the residue contains metallic copper. If verdigris be boiled in distilled water, a solution is obtained, which is known to contain copper by its colour, and by the before-mentioned tests for its cupreous compounds.

¹ Dumas, Traité de Chimie, v. 1 69.

² Braude's Manual of Chemistry.

³ Benelitu, Traité tie Chimie, iv. 347 and 349.Composition. — Blue verdigris is the hydrated diacetate of copper. Green verdigris consists of the subsesquiacetate and the trisacetate.³ The composition of these salts is as follows: — [---]

Purity. — The following are the characters of its purity given by two of the British Colleges: —

Is partly soluble in water: almost entirely dissolved by diluted sulphuric acid by means of heat. Ammonia added in excess throws nothing down from this solution. — Ph. Lond.

It is dissolved in a great measure by muriatic acid, not above five per cent, of impurity being left. — Ph. Edin.

Chalk and sulphate of copper are employed to adulterate verdigris. The first effervesces with the mineral acids. The characteristics of the second have been already pointed out.

Physiological Effects. — The action of verdigris on the system is very similar to that of the other preparations of copper: thus, taken in small and repeated doses, it operates on the nervous system, and is called tonic and antispasmodic; in larger doses it acts as an emetic; and, in excessive doses, it is a powerful poison, producing both gastro enteritis (indicated by vomiting, purging, and pain,) and an affection of the nervous system (marked by insen sibility, convulsions, and even tetanus).

Uses. — Verdigris, when taken into the stomach, being variable and dan gerous in its operation, is never administered internally. It was formerly employed in obstinate syphilis, when mercurials failed.

The powder is sometimes employed as an escharotic. It is sprinkled over foul and indolent ulcers, or, when mixed with powdered savin, is applied to destroy venereal wart3. When used for the latter purpose it rarely fails.

1. Cupri subacetas præparatum, D.; Prepared Verdigris. (Take of Subacetate of Copper a convenient quantity: Reduce it to a powder by careful trituration in a porcelain mortar, and separate the finer parts for use by means of a sieve.) — The object of this process is to obtain a very fine powder. The water, however, effects a chemical change on the verdigris, and converts it into a soluble acetate and an insoluble trisacetate.