================================================================== | | | | | | | | | | FORMULAS OF OXIDES | SYMBOL | ATOMIC | DENSITY | MELTING |___________________ | | WEIGHT | | POINT | | | | | | | "ous" | "ic" ________|________|________|_________|_________|__________|________ | | | | | | Copper | Cu | 63.6 | 8.89 | 1084 deg. | Cu_{2}O | CuO Mercury | Hg | 200.00 | 13.596 | -39.5 deg. | Hg_{2}O | HgO Silver | Ag | 107.93 | 10.5 | 960 deg. | Ag_{2}O | AgO ================================================================== ~The family.~ By referring to the periodic arrangement of the elements (page 168), it will be seen that mercury is not included in the same family with copper and silver. Since the metallurgy of the three elements is so similar, however, and since they resemble each other so closely in chemical properties, it is convenient to class them together for study. 1. _Occurrence._ The three elements occur in nature to some extent in the free state, but are usually found as sulphides. Their ores are easy to reduce. 2. _Properties._ They are heavy metals of high luster and are especially good conductors of heat and electricity. They are not very active chemically. Neither hydrochloric nor dilute sulphuric acid has any appreciable action upon them. Concentrated sulphuric acid attacks all three, forming metallic sulphates and evolving sulphur dioxide, while nitric acid, both dilute and concentrated, converts them into nitrates with the evolution of oxides of nitrogen. 3. _Two series of salts._ Copper and mercury form oxides of the types M_{2}O and MO, as well as two series of salts. In one series the metals are univalent and the salts have formulas like those of the sodium salts. They are called cuprous and mercurous salts. In the other series the metals are divalent and resemble magnesium salts in formulas. These are called cupric and mercuric salts. Silver forms only one series of salts, being always a univalent metal. COPPER ~Occurrence.~ The element copper has been used for various purposes since the earliest days of history. It is often found in the metallic state in nature, large masses of it occurring pure in the Lake Superior region and in other places to a smaller extent. The most valuable ores are the following: Cuprite Cu_{2}O. Chalcocite Cu_{2}S. Chalcopyrite CuFeS_{2}. Bornite Cu_{3}FeS_{3}. Malachite CuCO_{3}.Cu(OH)_{2}. Azurite 2CuCO_{3}.Cu(OH)_{2}.