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Rare metals and rare earths
Rare earths of a lanthanum subset, or lanthanides, are applied in production of permanent magnets, in iron and steel industry and non-ferrous metallurgy, in nuclear, electronic, chemical and other industries. |
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Non-metals
Non-metals are chemical elements that form simple elements with no
metal-specific qualities. Non-metals typically include 22 elements: gases - hydrogen,
nitrogen,
oxygen, fluor, chlorine and inert gases; liquids - bromine; solids - boron, carbon,
silicon, phosphorus,
arsenic, sulphur,
selenium, tellurium, iodine, astatine. |
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Gold (Au) is a precious metal of a canary yellow colour; it is most sturdy and forgeable, compared to other metals. It can be easily flattened into most thin leaves; 1g of gold can be flattened into a leaf of 1 m2. Gold is very shiny and can be easily polished.
Relative density of gold is 19,32g/sm3; its melting point is 1063°Ñ, its Brinell number is 20.
Gold is very chemically resistant: neither oxygen, nor sulphur affects it, even at heating. Gold is resistant to moisture; it does not react with acids, alkalis, salts.
There exist no natural pure gold. It always has some mechanical impurities. Pure gold is a theoretical notion, its degree of purity is expressed through being 999; 999,9 and etc. pure. Gold, as every other metal, is being stamped. Pure gold stamp Gold 99,9% means, that this alloy contains 99,9% of gold, the rest is taken by impurities.
Pure gold is mostly used in alloys applied to manufacture jewelry, coins and medals. Copper, silver, nickel, palladium are basically used as basic additions (ligatures) in jewelry. The ligature composition determines the colour of a gold alloy: from white, if nickel or palladium is there, to red, if copper is used. In Russia in jewelry reddish gold is traditionally used, in Europe – yellowish gold.
Stamps for gold alloys used in jewelry are set and guaranteed by the state. Produced items undergo assay check and are stamped with an assay brand, which numbers determine the purity of the metal.back |
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