Copper. This metal is found in the metallic state, and in combination with oxygen, sulphur, acids, and other minerals, and in the organic kingdom, in the ashes of plants, and in the blood of animals. The copper of commerce is principally prepared from copper pyrites, a mixed sulphuret of iron and copper, found in Cornwall and other parts of the world. Copper is only prepared from 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 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.

3241. Test for the Quantity of Copper in a Compound

3241. Test for the Quantity of Copper in a Compound. The quantity of copper present in any compound may be estimated by throwing it down from its solution by pure potassa, after which it must be carefully collected, washed, dried, ignited, and weighed. This will give the quantity of the oxide from which its equivalent of metallic copper may be calculated; every 5 parts of the former being nearly equal to 4 of the latter: or, more accurately, every 39.7 parts are equal to 31.7 of pure metallic copper. Copper may also be precipitated at once in the metallic state, by immersing a piece of polished steel into the solution; but this method will not give very accurate results.

3242. To Separate Lead from Copper

3242.    To Separate Lead from Copper. Copper may be separated from lead by adding sulphuric acid to the nitric solution, and evaporating to dryness, when water digested on the residuum will dissolve out the sulphate of copper, but leave the sulphate of lead behind. From this solution the oxide of copper may be thrown down as before.

3243. To Separate Zinc from Copper

3243.    To Separate Zinc from Copper. Copper may be separated from zinc by sulphuretted hydrogen, which will throw down a sulphuret of copper, which may be dissolved in nitric acid, and treated as in last receipt.

3244. To Separate Tin from Copper

3244.    To Separate Tin from Copper. Digest in nitric acid ; the copper will be dissolved, but the tin will remain in an insoluble peroxide.

3245. To Separate Silver from Copper

3245.    To Separate Silver from Copper. Digest, in a state of filings or powder, in a solution of chloride of zinc, which dissolves the copper and leaves the silver unchanged.