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Gold Mining Companies Of South Africa
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile metal in a pure form. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions. Gold often occurs in free elemental ( native state), as nuggets or grains, in rocks, veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). Gold is resistant to most acids, though it does dissolve in aqua regia (a mixture of nitric acid and hydrochloric acid), forming a soluble tetrachloroaurate anion. Gold i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler substances by any chemical reaction. The number of protons in the nucleus is the defining property of an element, and is referred to as its atomic number (represented by the symbol ''Z'') – all atoms with the same atomic number are atoms of the same element. Almost all of the baryonic matter of the universe is composed of chemical elements (among rare exceptions are neutron stars). When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds. Only a minority of elements, such as silver and gold, are found uncombined as relatively pure native element minerals. Nearly all other naturally occurring elements occur in the Earth as compounds or mixtures. Air is primarily a mixture o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrum
Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. Its color ranges from pale to bright yellow, depending on the proportions of gold and silver. It has been produced artificially, and is also known as "green gold".Emsley, John (2003Nature's building blocks: an A–Z guide to the elements Oxford University Press. . p. 168 Electrum was used as early as the third millennium BC in Old Kingdom of Egypt, sometimes as an exterior coating to the pyramidions atop ancient Egyptian pyramids and obelisks. It was also used in the making of ancient drinking vessels. The first known metal coins made were of electrum, dating back to the end of the 7th century or the beginning of the 6th century BC. For several decades, the medals awarded with the Nobel Prize have been made of gold-plated green gold. Etymology The name "electrum" is the Latinized form of the Greek word ἤλεκτρον (''ḗlektron''), mentioned in the ''Odyssey' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Metal
A base metal is a common and inexpensive metal, as opposed to a precious metal such as gold or silver. In numismatics, coins often derived their value from the precious metal content; however, base metals have also been used in coins in the past and today. Specific definitions In contrast to noble metals, base metals may be distinguished by oxidizing or corroding relatively easily and reacting variably with diluted hydrochloric acid (HCl) to form hydrogen. Examples include iron, nickel, lead and zinc. Copper is also considered a base metal because it oxidizes relatively easily, although it does not react with HCl. In mining and economics, the term base metals refers to industrial non-ferrous metals excluding precious metals. These include copper, lead, nickel and zinc. The U.S. Customs and Border Protection agency is more inclusive in its definition of commercial base metals. Its list includes—in addition to copper, lead, nickel, and zinc—the following metals: iron and st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convention. The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons. A cation is a positively charged ion with fewer electrons than protons while an anion is a negatively charged ion with more electrons than protons. Opposite electric charges are pulled towards one another by electrostatic force, so cations and anions attract each other and readily form ionic compounds. Ions consisting of only a single atom are termed atomic or monatomic ions, while two or more atoms form molecular ions or polyatomic ions. In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of a free electron and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrachloroaurate
Chloroauric acid is an inorganic compound with the chemical formula . It forms hydrates . Both the trihydrate and tetrahydrate are known. Both are orange-yellow solids consisting of the planar anion. Often chloroauric acid is handled as a solution, such as those obtained by dissolution of gold in aqua regia. These solutions can be converted to other gold complexes or reduced to metallic gold or gold nanoparticles. Properties Structure The tetrahydrate crystallizes as and two water molecules. The oxidation state of gold in and anion is +3. The salts of (tetrachloroauric(III) acid) are tetrachloroaurates(III), containing anions (tetrachloroaurate(III) anions), which have square planar molecular geometry. The Au–Cl distances are around 2.28 Å. Other d8 complexes adopt similar structures, e.g. tetrachloroplatinate(II) . Solute properties Solid chloroauric acid is a hydrophilic ( ionic) protic solute. It is soluble in water and other oxygen-containing solvents, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrochloric Acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H+, and an anion, A-. The dissociation of a strong acid in solution is effectively complete, except in its most concentrated solutions .... It is a component of the gastric acid in the digestive systems of most animal species, including humans. Hydrochloric acid is an important laboratory reagent and industrial chemical. History In the early tenth century, the Persian physician and alchemist Abu Bakr al-Razi ( 865–925, Latin: Rhazes) conducted experiments with sal ammoniac (ammonium chloride) and vitriol (hydrated sulfates of various metals), which he distilled together, thus producing the gas hydrogen chloride. In doing so, al-Razi may have stumbled upon a primitive method ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitric Acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% , it is referred to as ''fuming nitric acid''. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%. Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is also commonly used as a strong oxidizing agen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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