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Chromium(III) Oxide
Chromium(III) oxide (or chromia) is an inorganic compound with the formula . It is one of the principal oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite. Structure and properties has the corundum structure, consisting of a hexagonal close packed array of oxide anions with of the octahedral holes occupied by chromium. Similar to corundum, is a hard, brittle material (Mohs hardness 8 to 8.5). It is antiferromagnetic up to 307 K, the Néel temperature. It is not readily attacked by acids. Occurrence occurs naturally as the mineral eskolaite, which is found in chromium-rich tremolite skarns, metaquartzites, and chlorite veins. Eskolaite is also a rare component of chondrite meteorites. The mineral is named after Finnish geologist Pentti Eskola. Production The Parisians Pannetier and Binet first prepared the transparent hydrated form of in 1838 via a secret process, sold as a pigment. It is derived from the mineral chromite, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eskolaite
Eskolaite is a rare chromium oxide mineral (chromium(III) oxide Cr2O3). Discovery and occurrence It was first described in 1958 for an occurrence in the Outokumpu ore deposit of eastern Finland. It occurs in chromium bearing tremolite skarns, metamorphosed quartzites and chlorite bearing veins in Finland; in glacial boulder clays in Ireland and in stream pebbles in the Merume River of Guyana. It has also been recognized as a rare component in chondrite meteorites. The mineral is named after the Finnish geologist Pentti Eskola (1883–1964). Structure and physical properties Eskolaite crystallizes with trigonal symmetry in the space group ''R'c'' and has the lattice parameters a = 4.95 Å and c = 13.58 Å at standard conditions. The unit cell contains six formula units. The lattice is analogous to that of corundum, with Cr3+ replacing Al3+. See also * List of minerals named after people This is a list of minerals named after people. The chemical composition follows name. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentti Eskola
Pentti Elias Eskola (8 January 1883 – 6 December 1964) was a Finnish geologist who specialised in the petrology of granites and developed the concept of metamorphic facies. He won the Wollaston Medal in 1958, the Vetlesen Prize in 1964, and was given a state funeral upon his death. The mineral eskolaite is named in his honor. Eskola was born in Lellainen, the son of a farmer. He graduated from the University of Helsinki The University of Helsinki ( fi, Helsingin yliopisto, sv, Helsingfors universitet, abbreviated UH) is a public research university located in Helsinki, Finland since 1829, but founded in the city of Turku (in Swedish ''Åbo'') in 1640 as the R ... in 1906 and received a doctorate in 1914 with a dissertation on the petrology of the Orijärvi Region. Eskola was a student of Wilhelm Ramsay. He visited Norway and the US in 1920-21 working at the Geophysical Laboratory in Washington, D. C. and with the Geological Survey of Canada during which time he exa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromic Acid
The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of chromic acid may be used as a cleaning mixture for glass. Chromic acid may also refer to the molecular species, H2CrO4 of which the trioxide is the anhydride. Chromic acid features chromium in an oxidation state of +6 (or VI). It is a strong and corrosive oxidising agent. Molecular chromic acid Molecular chromic acid, H2CrO4, has much in common with sulfuric acid, H2SO4. Only sulfuric acid can be classified as part of the 7 strong acids list. Due to the laws pertinent to the concept of "first order ionization energy", the first proton is lost most easily. It behaves extremely similar to sulfuric acid deprotonation. Since the process of polyvalent acid-base titrations have more than one proton (especially when the acid is starting substance and the base is the titrant), protons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium Trioxide
Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple solid under anhydrous conditions, bright orange when wet and which dissolves in water concomitant with hydrolysis. Millions of kilograms are produced annually, mainly for electroplating. Chromium trioxide is a powerful oxidiser and a carcinogen. Production, structure, and basic reactions Chromium trioxide is generated by treating sodium dichromate with sulfuric acid: :H2SO4 + Na2Cr2O7 → 2 CrO3 + Na2SO4 + H2O Approximately 100,000 tonnes are produced annually by this or similar routes. The solid consists of chains of tetrahedrally coordinated chromium atoms that share vertices. Each chromium center therefore shares two oxygen centers with neighbors. Two oxygen atoms are not shared, giving an overall stoichiometry of 1:3. : The st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium(II) Oxide
Chromium(II) oxide (CrO) is an inorganic compound composed of chromium and oxygen. It is a black powder that crystallises in the rock salt structure.Egon Wiberg, Arnold Frederick Holleman (2001) ''Inorganic Chemistry'', Elsevier Hypophosphites may reduce chromium(III) oxide to chromium(II) oxide: : H3PO2 + 2 Cr2O3 → 4 CrO + H3PO4 It is readily oxidized by the atmosphere. CrO is basic, while is acidic, and is amphoteric.Chemistry 7th edition, by Raymond Chang page 645 (problem 15.100) See also * Chromium(IV) oxide * Chromium(VI) oxide Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is an inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple s ... References Chromium(II) compounds Transition metal oxides Reducing agents Chromium–oxygen compounds Rock salt crystal structure {{inorganic-compound-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Monoxide
Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simplest molecule of the oxocarbon family. In coordination complexes the carbon monoxide ligand is called carbonyl. It is a key ingredient in many processes in industrial chemistry. The most common source of carbon monoxide is the partial combustion of carbon-containing compounds, when insufficient oxygen or heat is present to produce carbon dioxide. There are also numerous environmental and biological sources that generate and emit a significant amount of carbon monoxide. It is important in the production of many compounds, including drugs, fragrances, and fuels. Upon emission into the atmosphere, carbon monoxide affects several processes that contribute to climate change. Carbon monoxide has important biological roles across phylogene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium(III) Chloride
Chromium(III) chloride (also called chromic chloride) describes any of several chemical compounds with the formula CrCl3, where can be 0, 5, and 6. The anhydrous compound with the formula CrCl3 is a violet solid. The most common form of the trichloride is the dark green hexahydrate, CrCl3. Chromium chlorides find use as catalysts and as precursors to dyes for wool. Structure Anhydrous chromium(III) chloride adopts the YCl3 structure, with Cr3+ occupying one third of the octahedral interstices in alternating layers of a pseudo-cubic close packed lattice of Cl− ions. The absence of cations in alternate layers leads to weak bonding between adjacent layers. For this reason, crystals of CrCl3 cleave easily along the planes between layers, which results in the flaky (micaceous) appearance of samples of chromium(III) chloride. If pressurized to 9.9 GPa it goes under a phase transition. File:Chromium(III)-chloride-sheet-from-monoclinic-xtal-3D-balls-SF-overlay.png, Space-filling m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphoteric
In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used. One type of amphoteric species are amphiprotic molecules, which can either donate or accept a proton (). This is what "amphoteric" means in Brønsted–Lowry acid–base theory. Examples include amino acids and proteins, which have amine () and carboxylic acid () groups, and self-ionizable compounds such as water. Ampholytes are amphoteric molecules that contain both acidic and basic functional groups. For example, an amino acid has both a basic group and an acidic group , and exists as several structures in chemical equilibrium: :H2N-RCH-CO2H + H2O H2N-RCH-COO- + H3O+ H3N+-RCH-COOH + OH- H3N+-RCH-COO- + H2O In approximately neutral aqueous solution (pH ≅ 7), the basic amino group is mostly protonated and the carboxylic acid is mostly deprotonated, so that the predominant sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refractory
In materials science, a refractory material or refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycrystalline, polyphase, inorganic, non-metallic, porous, and heterogeneous. They are typically composed of oxides or carbides, nitrides etc. of the following materials: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium. ASTM C71 defines refractories as "...non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above ." Refractory materials are used in furnaces, kilns, incinerators, and reactors. Refractories are also used to make crucibles and moulds for casting glass and metals and for surfacing flame deflector systems for rocket launch structures. Today, the iron- and steel-industry and metal casting sectors use approx ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Razor Strop
A razor strop or simply a strop (sometimes called a razor strap or strap) is a flexible strip of leather, canvas, denim fabric, balsa wood, or other soft material, used to straighten and polish the blade of a straight razor, a knife, or a woodworking tool such as a chisel. In many cases stropping re-aligns parts of the blade edge that have been bent out of alignment. In other cases, especially when abrasive polishing compound is used, stropping may remove a small amount of metal (functionally equivalent to lapping). Stropping can also burnish (i.e. push metal around on) the blade. The strop may be a hanging strop or a hand-held paddle. Various abrasive compounds may be applied to the strop to aid in polishing the blade while stropping to obtain a mirror-like finish. Common abrasive compounds include half-micron diamonds, green chromium(III) oxide, white rouge ( aluminum oxide), and jeweller's rouge ( iron(III) oxide). Use Stropping is traditionally associated with straig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium(IV) Oxide
Chromium dioxide or chromium(IV) oxide is an inorganic compound with the formula CrO2. It is a black synthetic magnetic solid. It once was widely used in magnetic tape emulsion. With the increasing popularity of CDs and DVDs, the use of chromium(IV) oxide has declined. However, it is still used in data tape applications for enterprise-class storage systems. It is still considered by many oxide and tape manufacturers to have been one of the best magnetic recording particulates ever invented. Preparation and basic properties CrO2 was first prepared by Friedrich Wöhler by decomposition of chromyl chloride. Acicular chromium dioxide was first synthesized in 1956 by Norman L. Cox, a chemist at E.I. DuPont, by decomposing chromium trioxide in the presence of water at a temperature of and a pressure of 200 MPa. The balanced equation for the hydrothermal synthesis is: :3 CrO3 + Cr2O3 → 5 CrO2 + O2 The magnetic crystal that forms is a long, slender glass-like rod � ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viridian
Viridian is a blue-green pigment, a hydrated chromium(III) oxide, of medium saturation and relatively dark in value. It is composed of a majority of green, followed by blue. Specifically, it is a shade of spring green, which places the color between green and teal on the color wheel, or, in paint, a tertiary blue–green color. Viridian takes its name from the Latin ''viridis'', meaning "green". The first recorded use of ''viridian'' as a color name in English was in the 1860s (exact year uncertain). __TOC__ Variations of viridian Paolo Veronese green Paolo Veronese green is the color that is called ''Verde Verones'' in the ''Guía de coloraciones'' (''Guide to colorations'') by Rosa Gallego and Juan Carlos Sanz, a color dictionary published in 2005 that is widely popular in the Hispanophone realm. ''Paolo Veronese green'' was a color formulated and used by the noted 16th-century Venetian artist Paolo Veronese. ''Paolo Veronese green'' began to be used as a color name in En ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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