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To Separate Tin from Copper

may also be used for cleaning fine copper coins, but care must be taken not to use the Digest in nitric acid; the copper will be dismixture that has previously been employed for cleaning silver, or a coating of the latter metal may be the consequence. (See Nos. 3224 and 3225.) solved, but the tin will remain in an insoluble peroxide. 3245. To Separate Silver from Copper. Digest, in a state of filings or powder, Silver coins are often covered with a dense in a solution of chloride of zinc, which disgreen oxide. To remove this they should be solves the copper and leaves the silver unthe silver unsteeped for 10 minutes in a solution of am- changed. monia, then immersed in water and wiped 3246. To Separate Copper from its with a soft towel if necessary, a fresh Alloys. Copper may be separated in abso- . Copper may be separated in absoquantity of the solution may be applied. lute purity from antimony, arsenic, bismuth, Copper coin may be cleaned by immersing in lead, iron, &c., as it exists in bell-metal, brass, pure sweet oil and wiping dry with a soft bronze, and other commercial alloys, by rag. fusing, for about half an hour, in a crucible, 10 parts of the metal with 1 part each of copper scales (black oxide), and bottle glass. The pure copper is found at the bottom of Copper. This metal is found in the the crucible, whilst the other metals or impuri metallic state, and in combination with ties are either volatilized or dissolved in the oxygen, sulphur, acids, and other minerals, flux. sure to a moderate temperature. and in the organic kingdom, in the ashes of 3247. Copper in Fine Powder. A plants, and in the blood of animals. The solution of sulphate of copper is heated to the copper of commerce is principally prepared boiling-point, and precipitated with sublimaprecipitated with sublimafrom copper pyrites, a mixed sulphuret of ted zinc. (See No. 30.) The precipitated cop- No. 30.) The precipitated copiron and copper, found in Cornwall and other per is then separated from the adherent zinc parts of the world. Copper is oniy prepared by diluted sulphuric acid, and dried by expofrom its ores on the large scale. The copper pyrites are first roasted, and then smelted, by which process coarse metal is produced; this is again submitted to calcination and smelting, when fine metal is obtained. It afterwards undergoes the process of refining and toughening. This metal is malleable and ductile. It has a specific gravity of 8.8 to 8.9, fuses at about 2000 Fahr., and volatilizes at higher temperatures. It is easily soluble in nitric acid, and is attacked more or less rapidly by acids in general. It forms numerous compounds, all of which are more or less poisonous. Exposure to a damp atmosphere as rapidly as possible, to prevent oxidation. produces on its surface a green colored oxide, known as verdigris. Copper may be readily alloyed with other metals, except iron and lead, with which it unites with difficulty. 3248. Reduction of Copper in Fine Powder. M. Schiff gives the following process for obtaining copper in a state of fine division: A saturated solution of sulphate of copper, together with some crystals of the salt, are introduced into a bottle or flask, and agitated with some granulated zinc. The zinc displaces the copper from its solution, fresh sulphate dissolving as the action goes on, until the whole is exhausted. Heat is disengaged during the operation. The precipitated copper must be washed and dried