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Golden Ochre
Golden ochre, less often ''Gold Ochre'' (french: Ocre d’or, german: Gold Ocker от grc, ὠχρός yellow-pale, orange or ''french ochre'' (obsolete)) — one of the most famous and brightly colored varieties of ochre — is a natural or (rarely) artificial pigment. In terms of mineral composition, golden ochre is clay with an admixture of aluminosilicates and a high content of the yellow dye itself, iron hydroxide, most often in the form of brown iron ore or limonite. The exact composition of ochre and its impurities vary greatly depending on the place of origin. Golden ochre is one of the oldest paints, known as a painting material since the times of cave paintings. In wall painting it is one of the main yellow pigments. Golden ochre has good density, the same covering power, high light fastness, pure color and soft structure. To this day it is used in all painting techniques without exception. Description and properties The golden ochre pigment is a natural mixture th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roussillon, Isère
Roussillon () is a commune in the Isère department in southeastern France. Population See also *Communes of the Isère department The following is a list of the 512 communes in the French department of Isère. The communes cooperate in the following intercommunalities (as of 2020):Communes of Isère Isère communes articles needing translation from French Wikipedia {{Isère-geo-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfate
The sulfate or sulphate ion is a polyatomic ion, polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salt (chemistry), salts of sulfuric acid and many are prepared from that acid. Spelling "Sulfate" is the spelling recommended by International Union of Pure and Applied Chemistry, IUPAC, but "sulphate" was traditionally used in British English. Structure The sulfate anion consists of a central sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedron, tetrahedral arrangement. The symmetry is the same as that of methane. The sulfur atom is in the +6 oxidation state while the four oxygen atoms are each in the −2 state. The sulfate ion carries an overall charge (physics), charge of −2 and it is the conjugate acid, conjugate base of the bisulfate (or hydrogensulfate) ion, , which is in turn the conjugate base of , sulfuric acid. Organic sulf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manganese Dioxide
Manganese dioxide is the inorganic compound with the formula . This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for is for dry-cell batteries, such as the alkaline battery and the zinc–carbon battery.. is also used as a pigment and as a precursor to other manganese compounds, such as . It is used as a reagent in organic synthesis, for example, for the oxidation of allylic alcohols. is α polymorph that can incorporate a variety of atoms (as well as water molecules) in the "tunnels" or "channels" between the manganese oxide octahedra. There is considerable interest in as a possible cathode for lithium-ion batteries. Structure Several polymorphs of are claimed, as well as a hydrated form. Like many other dioxides, crystallizes in the rutile crystal structure (this polymorph is called pyrolusite or ), with three-coordinate oxide and octahedral metal cent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnesium Oxide
Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to remove moisture. Magnesium oxide was historically known as magnesia alba (literally, the white mineral from Magnesia), to differentiate it from '' magnesia negra'', a black mineral containing what is now known as manganese. Related oxides While "magnesium oxide" normally refers to MgO, the compound magnesium peroxide MgO2 is also known. According to evolutionary crystal structure prediction, MgO2 is thermodynamically stable at pressures above 116 GPa (gigapascals), and a semiconducting suboxide Mg3O2 is thermodynamically stable above 500 GPa. Because of its stability, MgO is used as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium Oxide
Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term "'' lime''" connotes calcium-containing inorganic materials, in which carbonates, oxides and hydroxides of calcium, silicon, magnesium, aluminium, and iron predominate. By contrast, ''quicklime'' specifically applies to the single chemical compound calcium oxide. Calcium oxide that survives processing without reacting in building products such as cement is called free lime. Quicklime is relatively inexpensive. Both it and a chemical derivative (calcium hydroxide, of which quicklime is the base anhydride) are important commodity chemicals. Preparation Calcium oxide is usually made by the thermal decomposition of materials, such as limestone or seashells, that contain calcium carbonate (CaCO3; mineral calcite) in a lime kiln. This is accomplished by heating the material to above ,Merck ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silicon Dioxide
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as a synthetic product. Notable examples include fused quartz, fumed silica, silica gel, opal and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries. Structure In the majority of silicates, the silicon atom shows tetrahedral coordination, with four oxygen atoms surrounding a central Si atomsee 3-D Unit Cell. Thus, SiO2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. In contrast, CO2 is a linear molecule. The starkly different structures of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron(III) Oxide
Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main source of iron for the steel industry. Fe2O3 is readily attacked by acids. Iron(III) oxide is often called rust, and to some extent this label is useful, because rust shares several properties and has a similar composition; however, in chemistry, rust is considered an ill-defined material, described as Hydrous ferric oxide. Structure Fe2O3 can be obtained in various polymorphs. In the main one, α, iron adopts octahedral coordination geometry. That is, each Fe center is bound to six oxygen ligands. In the γ polymorph, some of the Fe sit on tetrahedral sites, with four oxygen ligands. Alpha phase α-Fe2O3 has the rhombohedral, corundum (α-Al2O3) structure and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sienna
Sienna (from it, terra di Siena, meaning "Siena earth") is an earth pigment containing iron oxide and manganese oxide. In its natural state, it is yellowish brown and is called raw sienna. When heated, it becomes a reddish brown and is called burnt sienna.''Shorter Oxford English Dictionary'', 5th Edition (2002) It takes its name from the city-state of Siena, where it was produced during the Renaissance. Along with ochre and umber, it was one of the first pigments to be used by humans, and is found in many cave paintings. Since the Renaissance, it has been one of the brown pigments most widely used by artists. The first recorded use of ''sienna'' as a color name in English was in 1760. The normalized color coordinates for sienna are identical to kobe, first recorded as a color name in English in 1924. Earth colors Like the other earth colors, such as yellow ochre and umber, sienna is a clay containing iron oxide, called limonite, which in its natural state has a yello ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crocus Chrysanthus
''Crocus chrysanthus'', the snow crocus or golden crocus, is a species of flowering plant of the ''Crocus'' genus in the family Iridaceae. Native to the Balkans and Turkey, it bears vivid orange-yellow bowl-shaped flowers. It has smaller corms and a smaller flower than the giant Dutch crocus (''Crocus vernus''), although it produces more flowers per corm than the latter. Its common name, "snow crocus", derives from its exceptionally early flowering period, blooming about two weeks before the giant crocus, and often emerging through the snow in late winter or early spring. The leaves are narrow with a silver central stripe. Height: . The Latin specific epithet ''chrysanthus'' means "golden-flowered". Cultivars ''Crocus chrysanthus'' cultivars are selections from ''Crocus chrysanthus'' and hybrids of this species with several subspecies of '' Crocus biflorus'' and ''Crocus aerius''. Yellow cultivars are selections of ''Crocus chrysanthus''. Blue and white cultivars are hybrids o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient Rome
In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 BC), Roman Republic (509–27 BC) and Roman Empire (27 BC–476 AD) until the fall of the western empire. Ancient Rome began as an Italic settlement, traditionally dated to 753 BC, beside the River Tiber in the Italian Peninsula. The settlement grew into the city and polity of Rome, and came to control its neighbours through a combination of treaties and military strength. It eventually dominated the Italian Peninsula, assimilated the Greek culture of southern Italy (Magna Grecia) and the Etruscan culture and acquired an Empire that took in much of Europe and the lands and peoples surrounding the Mediterranean Sea. It was among the largest empires in the ancient world, with an estimated 50 to 90 million inhabitants, roughly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
