with verdegris; and vestiges of this metal have been detected in the well known cordial, called _Shrub_. In order to prevent the _contingent_ dangers attendant upon copper vessels, they ought always to be _tinned_;[311] and it is a very curious and interesting fact, that this latter metal, although it may cover the copper surface only imperfectly, will nevertheless protect us from its effects; for _M. Proust_ has shewn that the superior readiness with which _tin_ is oxidized and acted upon by acids, when compared with copper, will not allow this latter metal to appropriate to itself a single atom of oxygen. But copper vessels, notwithstanding this fact, unless well tinned, should be dismissed from the service of the kitchen. The Senate of Sweden, in the year 1753, prohibited them entirely, and ordered that none but such as were made of iron should be used in their fleets and army. VERDEGRIS. _Ærugo._ The verdegris of commerce is a compound mass, consisting of the acetate, and sub-acetate of copper, carbonate of copper, and copper partly metallic, and partly oxidized; it, moreover, contains the stalks of grapes and other extraneous matter. Boiling water dissolves it in part, and, at the same time, occasions in it a chemical change, by transforming one portion of the _sub_-acetate into the soluble acetate, and another, into an oxide of copper, which is precipitated. With cold water, verdegris demeans itself very 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. Sulphuric acid poured on its powder decomposes it with effervescence, and vapours of acetic acid are disengaged; a character by which this substance may be easily identified. BLUE VITRIOL. _Sulphate of Copper._ _Blue Copperas—Roman Vitriol._ This salt occurs in crystals of a deep rich blue colour, and whose form is that of a rhomboidal prism; their taste is harsh, acrid, and styptic; on exposure to air they slightly effloresce, and assume a greenish hue. When treated with sulphuric acid, no effervescence occurs, a circumstance which at once distinguishes this salt from _ærugo_. _Symptoms of Poisoning by the Salts of Copper._ The operation of these bodies, upon the human system, is betrayed by an acrid, styptic, coppery taste, in the mouth; nausea; head-ache; a dry and parched tongue; vomiting; coppery eructations; a cutaneous eruption; violent pains in the bowels; very frequent alvine evacuations, sometimes green, and often bloody and blackish; great and painful distention of the abdomen; small and irregular pulse; heat of skin; ardent thirst; difficult and laborious respiration; hiccup; syncope; cold sweats; convulsions—death. It does not, however, kill so speedily as arsenic, or corrosive sublimate.