VERDIGRIS is the popular name for diacetate of copper (2CuO,C,IL0.+6Aq), a substance which is largely used for commercial purposes, and as an external application In surgery. It Is prepared on a large scale by piling up copper-plates with alternate layers of mare or fermenting grape-skins. In the course of a few weeks, the surface of the copper is covered with a crust of the salt, is detached, made into a thick paste with vinegar, and pressed into molds. The salt thus obtained is in the form of a bluish green tough mass, which is not easily pulverized. The formatitm of the salt by this pro cess is due to the alcohol in the grape-skins being slowly oxidized into acetic acid, while the copper absorbs oxygen from the air, and the oxide thus formed unites with the acetic acid. Verdigris may be obtained more directly by placing the copper sheets in cloths dipped in vinegar. Verdigris is permanent in the air; when heated, it first loses water, and then acetic acid, the residue being metallic copper. Water resolves it into an insol uble tribasic acetate, and a soluble subsesquiacetate of copper—a point which must be recollected in employing this salt. It is used by the surgeon as a caustic. application to venereal warts and fungous growths ; it is also a good application in ophthalmia tarsi, and has been of much service in stimulating old and indolent ulcers, in the ulcerated sore throat of scarlatina, and in malignant ulcer of the tongue. It may be used in the
form of an ointment or a liniment. The latter, formerly known as reel yEgyptiacum, is composed of 1 ounce of powdered verdigris, 7 ounces of vinegar, and 14 of honey. The verdigris is dissolved in the vinegar, and to the strained solution the honey is added, and the Whole is boiled to a proper consistence. It should be applied with a camel-hair pencil.
Verdigris is an active irritant poison, but is much more commonly the source of acci dental than intentional poisoning, it being often formed in copper vessels used for cook ing, or in the very reprehensible practice of putting copper coins into pickles to give them a fine green color. If copper vessels for cooking are kept perfectly clean, they seem not to be dangerous, provided (1) no acid matter be placed in them; (2) that the boiled materials are at once poured out, and not allowed to stand to cool in them ; and (3) that the vessels are always at once cleaned. But the interior of such vessels should always be tinned, care being frequently taken that the tinning remains entire. In cases of poisoning the best treatment consists in the free administration of white of eggs and milk.