QUALITIES. _Form_, a dry mass composed of minute crystals, not deliquescent; _Colour_, bluish green. CHEMICAL COMPOSITION. Several constituents enter into its composition, viz. Acetate and sub-acetate of copper, carbonate of copper, and copper partly metallic and partly oxidized; it contains also the stalks of grapes and other extraneous substances. SOLUBILITY. Boiling water dissolves it in part, and produces in it a chemical change, by transforming one portion of the _sub_-acetate into the soluble acetate, and another into an oxyd of copper, which is precipitated; with cold water this substance demeans itself differently, the acetate is dissolved by it, whilst that portion which is in the state of _sub_-salt remains suspended in the form of a fine green powder. Vinegar converts all the _Ærugo_ into a soluble acetate, this liquid therefore ought never to be employed for favouring vomiting in cases where an overdose has been swallowed, for the reasons stated in the first part of this work, p. 136. Sulphuric acid poured on powdered _verdigris_ decomposes it with effervescence, and vapours of acetic acid are disengaged. It appears from the experiments and observations of Duval and Orfila, that sugar exercises a chemical action on it, by which its solubility is diminished, and that on this account it acts as a specific against its poisonous effects. USES. It is so uncertain and violent in its operation that it is rarely employed, except externally,[358] when it acts as a powerful detergent, and mild escharotic; and in the form of ointment, is a valuable application for many cutaneous affections, especially the aggravated kinds of Tetter. OFFICINAL PREPARATIONS. _Ærugo Præparata_, D. _Linimentum Æruginis._ L. D. ADULTERATIONS. There is a spurious article sold under the name of _English Verdigris_, which consists of sulphate of copper, triturated with acetate of lead; and to make the fraud still more complete, the soft mass is mixed with the stalks of Raisins. ÆTHER SULPHURICUS RECTIFICATUS. L. _Rectified Sulphuric Æther._