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116-409: Khromtau has important Chromium deposits, which are currently exploited in underground mines by Kazchrome, a subsidiary of Eurasian Natural Resources Corporation (ENRC). Previously, Chromite ore was mined in open cast mines, which left enormous pits behind. The newly built mosque and the also new Russian orthodox church are juxtaposed on the main square of town. FC Gornyak soccer team played in

232-637: A color space , which when being abstracted as a mathematical color model can assign each region of color with a corresponding set of numbers. As such, color spaces are an essential tool for color reproduction in print , photography , computer monitors, and television . The most well-known color models are RGB , CMYK , YUV , HSL, and HSV . Because the perception of color is an important aspect of human life, different colors have been associated with emotions , activity, and nationality . Names of color regions in different cultures can have different, sometimes overlapping areas. In visual arts , color theory

348-412: A complementary color . Afterimage effects have also been used by artists, including Vincent van Gogh . When an artist uses a limited color palette , the human visual system tends to compensate by seeing any gray or neutral color as the color which is missing from the color wheel. For example, in a limited palette consisting of red, yellow, black, and white, a mixture of yellow and black will appear as

464-746: A Cr-Cr quintuple bond (length 183.51(4) pm) has also been described. Extremely bulky monodentate ligands stabilize this compound by shielding the quintuple bond from further reactions. Chromium is the 21st most abundant element in Earth's crust with an average concentration of 100 ppm. Chromium compounds are found in the environment from the erosion of chromium-containing rocks, and can be redistributed by volcanic eruptions. Typical background concentrations of chromium in environmental media are: atmosphere <10 ng/m ; soil <500 mg/kg; vegetation <0.5 mg/kg; freshwater <10 μg/L; seawater <1 μg/L; sediment <80 mg/kg. Chromium

580-491: A black object. The subtractive model also predicts the color resulting from a mixture of paints, or similar medium such as fabric dye, whether applied in layers or mixed together prior to application. In the case of paint mixed before application, incident light interacts with many different pigment particles at various depths inside the paint layer before emerging. Structural colors are colors caused by interference effects rather than by pigments. Color effects are produced when

696-414: A change to less toxic chromium(III) compounds. The mineral crocoite (which is also lead chromate PbCrO 4 ) was used as a yellow pigment shortly after its discovery. After a synthesis method became available starting from the more abundant chromite, chrome yellow was, together with cadmium yellow , one of the most used yellow pigments. The pigment does not photodegrade, but it tends to darken due to

812-477: A continuous spectrum. The human eye cannot tell the difference between such light spectra just by looking into the light source, although the color rendering index of each light source may affect the color of objects illuminated by these metameric light sources. Similarly, most human color perceptions can be generated by a mixture of three colors called primaries . This is used to reproduce color scenes in photography, printing, television, and other media. There are

928-521: A critical material during the emergency". The United States likewise considered chromium "essential for the German war industry" and made intense diplomatic efforts to keep it out of the hands of Nazi Germany . The high hardness and corrosion resistance of unalloyed chromium makes it a reliable metal for surface coating; it is still the most popular metal for sheet coating, with its above-average durability, compared to other coating metals. A layer of chromium

1044-419: A given type become desensitized. For a few seconds after the light ceases, they will continue to signal less strongly than they otherwise would. Colors observed during that period will appear to lack the color component detected by the desensitized photoreceptors. This effect is responsible for the phenomenon of afterimages , in which the eye may continue to see a bright figure after looking away from it, but in

1160-414: A high infrared and visible light reflectance. Chromium metal in air is passivated : it forms a thin, protective surface layer of chromium oxide with the corundum structure. Passivation can be enhanced by short contact with oxidizing acids like nitric acid . Passivated chromium is stable against acids. Passivation can be removed with a strong reducing agent that destroys the protective oxide layer on

1276-483: A larger chromite deposit was discovered near Baltimore , United States, which quickly met the demand for tanning salts much more adequately than the crocoite that had been used previously. This made the United States the largest producer of chromium products until the year 1848, when larger deposits of chromite were uncovered near the city of Bursa , Turkey. With the development of metallurgy and chemical industries in

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1392-451: A material is scored with fine parallel lines, formed of one or more parallel thin layers, or otherwise composed of microstructures on the scale of the color's wavelength . If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce Tyndall effect colors: the blue of the sky (Rayleigh scattering, caused by structures much smaller than the wavelength of light, in this case, air molecules),

1508-476: A nearly straight edge. For example, mixing green light (530 nm) and blue light (460 nm) produces cyan light that is slightly desaturated, because response of the red color receptor would be greater to the green and blue light in the mixture than it would be to a pure cyan light at 485 nm that has the same intensity as the mixture of blue and green. Because of this, and because the primaries in color printing systems generally are not pure themselves,

1624-490: A normal human would view as metamers . Some invertebrates, such as the mantis shrimp , have an even higher number of cones (12) that could lead to a richer color gamut than even imaginable by humans. The existence of human tetrachromats is a contentious notion. As many as half of all human females have 4 distinct cone classes , which could enable tetrachromacy. However, a distinction must be made between retinal (or weak ) tetrachromats , which express four cone classes in

1740-468: A number of methods or color spaces for specifying a color in terms of three particular primary colors . Each method has its advantages and disadvantages depending on the particular application. No mixture of colors, however, can produce a response truly identical to that of a spectral color, although one can get close, especially for the longer wavelengths, where the CIE 1931 color space chromaticity diagram has

1856-401: A perception of color. Behavioral and functional neuroimaging experiments have demonstrated that these color experiences lead to changes in behavioral tasks and lead to increased activation of brain regions involved in color perception, thus demonstrating their reality, and similarity to real color percepts, albeit evoked through a non-standard route. Synesthesia can occur genetically, with 4% of

1972-424: A single wavelength only, the pure spectral or monochromatic colors . The spectrum above shows approximate wavelengths (in nm ) for spectral colors in the visible range. Spectral colors have 100% purity , and are fully saturated . A complex mixture of spectral colors can be used to describe any color, which is the definition of a light power spectrum . The spectral colors form a continuous spectrum, and how it

2088-422: A solution of polyvinyl butyral . An 8% solution of phosphoric acid in solvent was added just before application. It was found that an easily oxidized alcohol was an essential ingredient. A thin layer of about 10–15 μm was applied, which turned from yellow to dark green when it was cured. There is still a question as to the correct mechanism. Chrome green is a mixture of Prussian blue and chrome yellow , while

2204-549: A spectral color has the maximal saturation. In Helmholtz coordinates , this is described as 100% purity . The physical color of an object depends on how it absorbs and scatters light. Most objects scatter light to some degree and do not reflect or transmit light specularly like glasses or mirrors . A transparent object allows almost all light to transmit or pass through, thus transparent objects are perceived as colorless. Conversely, an opaque object does not allow light to transmit through and instead absorbs or reflects

2320-431: A spectral color, relative to the context in which it is viewed, may alter its perception considerably. For example, a low-intensity orange-yellow is brown , and a low-intensity yellow-green is olive green . Additionally, hue shifts towards yellow or blue happen if the intensity of a spectral light is increased; this is called Bezold–Brücke shift . In color models capable of representing spectral colors, such as CIELUV ,

2436-407: A surface displays comes from the parts of the visible spectrum that are not absorbed and therefore remain visible. Without pigments or dye, fabric fibers, paint base and paper are usually made of particles that scatter white light (all colors) well in all directions. When a pigment or ink is added, wavelengths are absorbed or "subtracted" from white light, so light of another color reaches the eye. If

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2552-399: A variety of green, a mixture of red and black will appear as a variety of purple, and pure gray will appear bluish. The trichromatic theory is strictly true when the visual system is in a fixed state of adaptation. In reality, the visual system is constantly adapting to changes in the environment and compares the various colors in a scene to reduce the effects of the illumination. If a scene

2668-547: Is Cr with a half-life of 27.7 days. All of the remaining radioactive isotopes have half-lives that are less than 24 hours and the majority less than 1 minute. Chromium also has two metastable nuclear isomers . The primary decay mode before the most abundant stable isotope, Cr, is electron capture and the primary mode after is beta decay . Cr is the radiogenic decay product of Mn (half-life 3.74 million years). Chromium isotopes are typically collocated (and compounded) with manganese isotopes. This circumstance

2784-648: Is congenital red–green color blindness , affecting ~8% of males. Individuals with the strongest form of this condition ( dichromacy ) will experience blue and purple, green and yellow, teal, and gray as colors of confusion, i.e. metamers. Outside of humans, which are mostly trichromatic (having three types of cones), most mammals are dichromatic, possessing only two cones. However, outside of mammals, most vertebrates are tetrachromatic , having four types of cones. This includes most birds , reptiles , amphibians , and bony fish . An extra dimension of color vision means these vertebrates can see two distinct colors that

2900-428: Is 125 nanoohm - meters . Chromium has a high specular reflection in comparison to other transition metals. In infrared , at 425  μm , chromium has a maximum reflectance of about 72%, reducing to a minimum of 62% at 750 μm before rising again to 90% at 4000 μm. When chromium is used in stainless steel alloys and polished , the specular reflection decreases with the inclusion of additional metals, yet

3016-409: Is 8.5, which means that it can scratch samples of quartz and topaz , but can be scratched by corundum . Chromium is highly resistant to tarnishing , which makes it useful as a metal that preserves its outermost layer from corroding , unlike other metals such as copper , magnesium , and aluminium . Chromium has a melting point of 1907 °C (3465 °F), which is relatively low compared to

3132-566: Is Cr(VI). Chromium minerals as pigments came to the attention of the west in the eighteenth century. On 26 July 1761, Johann Gottlob Lehmann found an orange-red mineral in the Beryozovskoye mines in the Ural Mountains which he named Siberian red lead . Though misidentified as a lead compound with selenium and iron components, the mineral was in fact crocoite with a formula of PbCrO 4 . In 1770, Peter Simon Pallas visited

3248-457: Is a "substance of very high concern" (SVHC). Gaseous chromium has a ground-state electron configuration of [ Ar ] 3d 4s . It is the first element in the periodic table whose configuration violates the Aufbau principle . Exceptions to the principle also occur later in the periodic table for elements such as copper , niobium and molybdenum . Chromium is the first element in the 3d series where

3364-483: Is a strong oxidizing agent. Compounds of chromium(V) are rather rare; the oxidation state +5 is only realized in few compounds but are intermediates in many reactions involving oxidations by chromate. The only binary compound is the volatile chromium(V) fluoride (CrF 5 ). This red solid has a melting point of 30 °C and a boiling point of 117 °C. It can be prepared by treating chromium metal with fluorine at 400 °C and 200 bar pressure. The peroxochromate(V)

3480-412: Is an optimal color. With the current state of technology, we are unable to produce any material or pigment with these properties. Thus, four types of "optimal color" spectra are possible: In the first, the transition goes from 0 at both ends of the spectrum to 1 in the middle, as shown in the image at right. In the second, it goes from 1 at the ends to 0 in the middle. In the third type, it starts at 1 at

3596-451: Is another example of the +5 oxidation state. Potassium peroxochromate (K 3 [Cr(O 2 ) 4 ]) is made by reacting potassium chromate with hydrogen peroxide at low temperatures. This red brown compound is stable at room temperature but decomposes spontaneously at 150–170 °C. Compounds of chromium(IV) are slightly more common than those of chromium(V). The tetrahalides, CrF 4 , CrCl 4 , and CrBr 4 , can be produced by treating

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3712-538: Is bright enough to strongly stimulate the cones, rods play virtually no role in vision at all. On the other hand, in dim light, the cones are understimulated leaving only the signal from the rods, resulting in a colorless response (furthermore, the rods are barely sensitive to light in the "red" range). In certain conditions of intermediate illumination, the rod response and a weak cone response can together result in color discriminations not accounted for by cone responses alone. These effects, combined, are summarized also in

3828-412: Is characterized by its wavelength (or frequency ) and its intensity . When the wavelength is within the visible spectrum (the range of wavelengths humans can perceive, approximately from 390  nm to 700 nm), it is known as "visible light ". Most light sources emit light at many different wavelengths; a source's spectrum is a distribution giving its intensity at each wavelength. Although

3944-401: Is composed of four stable isotopes ; Cr, Cr, Cr and Cr, with Cr being the most abundant (83.789% natural abundance ). Cr is observationally stable , as it is theoretically capable of decaying to Ti via double electron capture with a half-life of no less than 1.3 × 10 years. Twenty-five radioisotopes have been characterized, ranging from Cr to Cr; the most stable radioisotope

4060-414: Is deposited on pretreated metallic surfaces by electroplating techniques. There are two deposition methods: thin, and thick. Thin deposition involves a layer of chromium below 1 μm thickness deposited by chrome plating , and is used for decorative surfaces. Thicker chromium layers are deposited if wear-resistant surfaces are needed. Both methods use acidic chromate or dichromate solutions. To prevent

4176-476: Is divided into distinct colors linguistically is a matter of culture and historical contingency. Despite the ubiquitous ROYGBIV mnemonic used to remember the spectral colors in English, the inclusion or exclusion of colors is contentious, with disagreement often focused on indigo and cyan. Even if the subset of color terms is agreed, their wavelength ranges and borders between them may not be. The intensity of

4292-447: Is formed, which can be stabilized as an ether adduct CrO 5 ·OR 2 . Chromic acid has the hypothetical formula H 2 CrO 4 . It is a vaguely described chemical, despite many well-defined chromates and dichromates being known. The dark red chromium(VI) oxide CrO 3 , the acid anhydride of chromic acid, is sold industrially as "chromic acid". It can be produced by mixing sulfuric acid with dichromate and

4408-463: Is illuminated with one light, and then with another, as long as the difference between the light sources stays within a reasonable range, the colors in the scene appear relatively constant to us. This was studied by Edwin H. Land in the 1970s and led to his retinex theory of color constancy . Both phenomena are readily explained and mathematically modeled with modern theories of chromatic adaptation and color appearance (e.g. CIECAM02 , iCAM). There

4524-610: Is mined as chromite (FeCr 2 O 4 ) ore. About two-fifths of the chromite ores and concentrates in the world are produced in South Africa, about a third in Kazakhstan, while India, Russia, and Turkey are also substantial producers. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan and southern Africa. Although rare, deposits of native chromium exist. The Udachnaya Pipe in Russia produces samples of

4640-609: Is no need to dismiss the trichromatic theory of vision, but rather it can be enhanced with an understanding of how the visual system adapts to changes in the viewing environment. Color reproduction is the science of creating colors for the human eye that faithfully represent the desired color. It focuses on how to construct a spectrum of wavelengths that will best evoke a certain color in an observer. Most colors are not spectral colors , meaning they are mixtures of various wavelengths of light. However, these non-spectral colors are often described by their dominant wavelength , which identifies

4756-604: Is stable at neutral pH . Some other notable chromium(II) compounds include chromium(II) oxide CrO , and chromium(II) sulfate CrSO 4 . Many chromium(II) carboxylates are known. The red chromium(II) acetate (Cr 2 (O 2 CCH 3 ) 4 ) is somewhat famous. It features a Cr-Cr quadruple bond . A large number of chromium(III) compounds are known, such as chromium(III) nitrate , chromium(III) acetate , and chromium(III) oxide . Chromium(III) can be obtained by dissolving elemental chromium in acids like hydrochloric acid or sulfuric acid , but it can also be formed through

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4872-576: Is still high in comparison with other alloys. Between 40% and 60% of the visible spectrum is reflected from polished stainless steel. The explanation on why chromium displays such a high turnout of reflected photon waves in general, especially the 90% in infrared, can be attributed to chromium's magnetic properties. Chromium has unique magnetic properties; it is the only elemental solid that shows antiferromagnetic ordering at room temperature and below. Above 38 °C, its magnetic ordering becomes paramagnetic . The antiferromagnetic properties, which cause

4988-428: Is then processed by the brain . Colors have perceived properties such as hue , colorfulness (saturation), and luminance . Colors can also be additively mixed (commonly used for actual light) or subtractively mixed (commonly used for materials). If the colors are mixed in the right proportions, because of metamerism , they may look the same as a single-wavelength light. For convenience, colors can be organized in

5104-449: Is then used to produce alloys such as stainless steel. Pure chromium metal is produced by a different process: roasting and leaching of chromite to separate it from iron, followed by reduction with carbon and then aluminium . Trivalent chromium (Cr(III)) occurs naturally in many foods and is sold as a dietary supplement , although there is insufficient evidence that dietary chromium provides nutritional benefit to people. In 2014,

5220-413: Is used to govern the use of colors in an aesthetically pleasing and harmonious way. The theory of color includes the color complements ; color balance ; and classification of primary colors (traditionally red , yellow , blue ), secondary colors (traditionally orange , green , purple ), and tertiary colors . The study of colors in general is called color science . Electromagnetic radiation

5336-523: Is used where high temperature would normally cause carburization , oxidation or corrosion . Incoloy 800 "is capable of remaining stable and maintaining its austenitic structure even after long time exposures to high temperatures". Nichrome is used as resistance wire for heating elements in things like toasters and space heaters. These uses make chromium a strategic material . Consequently, during World War II, U.S. road engineers were instructed to avoid chromium in yellow road paint, as it "may become

5452-580: Is useful in isotope geology . Manganese-chromium isotope ratios reinforce the evidence from Al and Pd concerning the early history of the Solar System . Variations in Cr/ Cr and Mn/Cr ratios from several meteorites indicate an initial Mn/ Mn ratio that suggests Mn-Cr isotopic composition must result from in-situ decay of Mn in differentiated planetary bodies. Hence Cr provides additional evidence for nucleosynthetic processes immediately before coalescence of

5568-571: The European Food Safety Authority concluded that research on dietary chromium did not justify it to be recognized as an essential nutrient . While chromium metal and Cr(III) ions are considered non-toxic, chromate and its derivatives, often called " hexavalent chromium ", is toxic and carcinogenic . According to the European Chemicals Agency (ECHA), chromium trioxide that is used in industrial electroplating processes

5684-529: The Kazakhstan First Division . They are now defunct. The colours of the bandy team Gornyak are green and white. They played a test match against Akzhaiyk at Medeu before the 2011 Asian Winter Games, but have no adult team in league as they used to. [1] Nowadays young players is the focus. The town sent a bandy team to the Spartakiade 2009. Aktobe Region, made up by players from Khromtau, won

5800-457: The Kruithof curve , which describes the change of color perception and pleasingness of light as a function of temperature and intensity. While the mechanisms of color vision at the level of the retina are well-described in terms of tristimulus values, color processing after that point is organized differently. A dominant theory of color vision proposes that color information is transmitted out of

5916-430: The color wheel : it is the collection of colors for which at least one of the two color channels measures a value at one of its extremes. The exact nature of color perception beyond the processing already described, and indeed the status of color as a feature of the perceived world or rather as a feature of our perception of the world—a type of qualia —is a matter of complex and continuing philosophical dispute. From

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6032-458: The long-wavelength cones , L cones , or red cones , are most sensitive to light that is perceived as greenish yellow, with wavelengths around 570 nm. Light, no matter how complex its composition of wavelengths, is reduced to three color components by the eye. Each cone type adheres to the principle of univariance , which is that each cone's output is determined by the amount of light that falls on it over all wavelengths. For each location in

6148-411: The opponent process theory of color, noting that color blindness and afterimages typically come in opponent pairs (red-green, blue-orange, yellow-violet, and black-white). Ultimately these two theories were synthesized in 1957 by Hurvich and Jameson, who showed that retinal processing corresponds to the trichromatic theory, while processing at the level of the lateral geniculate nucleus corresponds to

6264-469: The visible spectrum , and almost 90% of infrared light . The name of the element is derived from the Greek word χρῶμα, chrōma , meaning color , because many chromium compounds are intensely colored. Industrial production of chromium proceeds from chromite ore (mostly FeCr 2 O 4 ) to produce ferrochromium , an iron-chromium alloy, by means of aluminothermic or silicothermic reactions . Ferrochromium

6380-445: The 3d electrons start to sink into the core; they thus contribute less to metallic bonding , and hence the melting and boiling points and the enthalpy of atomisation of chromium are lower than those of the preceding element vanadium . Chromium(VI) is a strong oxidising agent in contrast to the molybdenum (VI) and tungsten (VI) oxides. Chromium is the third hardest element after carbon ( diamond ) and boron . Its Mohs hardness

6496-593: The Cr-centered Keggin anion [α-CrW 12 O 40 ] . Chromium(III) hydroxide (Cr(OH) 3 ) is amphoteric , dissolving in acidic solutions to form [Cr(H 2 O) 6 ] , and in basic solutions to form [Cr(OH) 6 ] . It is dehydrated by heating to form the green chromium(III) oxide (Cr 2 O 3 ), a stable oxide with a crystal structure identical to that of corundum . Chromium(VI) compounds are oxidants at low or neutral pH. Chromate anions ( CrO 4 ) and dichromate (Cr 2 O 7 ) anions are

6612-826: The Solar System. Cr has been posited as a proxy for atmospheric oxygen concentration. Chromium is a member of group 6 , of the transition metals . The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist. Many Cr(0) complexes are known. Bis(benzene)chromium and chromium hexacarbonyl are highlights in organochromium chemistry . Chromium(II) compounds are uncommon, in part because they readily oxidize to chromium(III) derivatives in air. Water-stable chromium(II) chloride CrCl 2 that can be made by reducing chromium(III) chloride with zinc. The resulting bright blue solution created from dissolving chromium(II) chloride

6728-602: The Spartakiade in 2013. [2] For the 2014-15 season, two youth teams were allowed to participate in the leagues of Sverdlovsk Oblast . [3] Two players from Khromtau, Sultan Kadyrzhanov [4] and Kuanysh Tiemiralin [5] has played in Kazakhstan's only professional club, Akzhaiyk [6] from Oral . Sultan was also part of the Kazakh team at the 2011 Asian Winter Games and his World Championship debut came in 2018. A national youth championship has been organised. [7] 2016 Gornyak won

6844-526: The V1 blobs, color information is sent to cells in the second visual area, V2. The cells in V2 that are most strongly color tuned are clustered in the "thin stripes" that, like the blobs in V1, stain for the enzyme cytochrome oxidase (separating the thin stripes are interstripes and thick stripes, which seem to be concerned with other visual information like motion and high-resolution form). Neurons in V2 then synapse onto cells in

6960-555: The Western world, the need for chromium increased. Chromium is also famous for its reflective, metallic luster when polished. It is used as a protective and decorative coating on car parts, plumbing fixtures, furniture parts and many other items, usually applied by electroplating . Chromium was used for electroplating as early as 1848, but this use only became widespread with the development of an improved process in 1924. Approximately 28.8 million metric tons (Mt) of marketable chromite ore

7076-417: The achromatic colors ( black , gray , and white ) and colors such as pink , tan , and magenta . Two different light spectra that have the same effect on the three color receptors in the human eye will be perceived as the same color. They are metamers of that color. This is exemplified by the white light emitted by fluorescent lamps, which typically has a spectrum of a few narrow bands, while daylight has

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7192-446: The chromate stored in the chromate conversion coating, which is able to migrate to local defects, are the benefits of this coating method. Because of environmental and health regulations on chromates, alternative coating methods are under development. Chromic acid anodizing (or Type I anodizing) of aluminium is another electrochemical process that does not lead to the deposition of chromium, but uses chromic acid as an electrolyte in

7308-429: The chrome oxide green is chromium(III) oxide . Color Color ( American English ) or colour ( British and Commonwealth English ) is the visual perception based on the electromagnetic spectrum . Though color is not an inherent property of matter , color perception is related to an object's light absorption , reflection , emission spectra , and interference . For most humans, colors are perceived in

7424-458: The chromium atoms to temporarily ionize and bond with themselves, are present because the body-centric cubic's magnetic properties are disproportionate to the lattice periodicity . This is due to the magnetic moments at the cube's corners and the unequal, but antiparallel, cube centers. From here, the frequency-dependent relative permittivity of chromium, deriving from Maxwell's equations and chromium's antiferromagnetism , leaves chromium with

7540-511: The colors on the straight line in the CIE xy chromaticity diagram (the " line of purples "), leading to magenta or purple -like colors. The third type produces the colors located in the "warm" sharp edge of the optimal color solid (this will be explained later in the article). The fourth type produces the colors located in the "cold" sharp edge of the optimal color solid. The optimal color solid , Rösch – MacAdam color solid, or simply visible gamut ,

7656-409: The colors reproduced are never perfectly saturated spectral colors, and so spectral colors cannot be matched exactly. However, natural scenes rarely contain fully saturated colors, thus such scenes can usually be approximated well by these systems. The range of colors that can be reproduced with a given color reproduction system is called the gamut . The CIE chromaticity diagram can be used to describe

7772-445: The deep shade of red pigment chrome red , which is simply lead chromate with lead(II) hydroxide (PbCrO 4 ·Pb(OH) 2 ). A very important chromate pigment, which was used widely in metal primer formulations, was zinc chromate, now replaced by zinc phosphate. A wash primer was formulated to replace the dangerous practice of pre-treating aluminium aircraft bodies with a phosphoric acid solution. This used zinc tetroxychromate dispersed in

7888-419: The energy-consuming change in oxidation state, the use of chromium(III) sulfate is under development; for most applications of chromium, the previously established process is used. In the chromate conversion coating process, the strong oxidative properties of chromates are used to deposit a protective oxide layer on metals like aluminium, zinc, and cadmium. This passivation and the self-healing properties of

8004-626: The extended V4 occurs in millimeter-sized color modules called globs . This is the part of the brain in which color is first processed into the full range of hues found in color space . A color vision deficiency causes an individual to perceive a smaller gamut of colors than the standard observer with normal color vision. The effect can be mild, having lower "color resolution" (i.e. anomalous trichromacy ), moderate, lacking an entire dimension or channel of color (e.g. dichromacy ), or complete, lacking all color perception (i.e. monochromacy ). Most forms of color blindness derive from one or more of

8120-480: The extended V4. This area includes not only V4, but two other areas in the posterior inferior temporal cortex, anterior to area V3, the dorsal posterior inferior temporal cortex, and posterior TEO. Area V4 was initially suggested by Semir Zeki to be exclusively dedicated to color, and he later showed that V4 can be subdivided into subregions with very high concentrations of color cells separated from each other by zones with lower concentration of such cells though even

8236-417: The eye by three opponent processes , or opponent channels, each constructed from the raw output of the cones: a red–green channel, a blue–yellow channel, and a black–white "luminance" channel. This theory has been supported by neurobiology, and accounts for the structure of our subjective color experience. Specifically, it explains why humans cannot perceive a "reddish green" or "yellowish blue", and it predicts

8352-535: The formation of chromium(III) oxide. It has a strong color, and was used for school buses in the United States and for the postal services (for example, the Deutsche Post ) in Europe. The use of chrome yellow has since declined due to environmental and safety concerns and was replaced by organic pigments or other alternatives that are free from lead and chromium. Other pigments that are based around chromium are, for example,

8468-515: The formation of discrete, stable, metal, carbide particles at the grain boundaries. For example, Inconel 718 contains 18.6% chromium. Because of the excellent high-temperature properties of these nickel superalloys , they are used in jet engines and gas turbines in lieu of common structural materials. ASTM B163 relies on chromium for condenser and heat-exchanger tubes, while castings with high strength at elevated temperatures that contain chromium are standardised with ASTM A567. AISI type 332

8584-420: The gamut that can be reproduced. Additive color is light created by mixing together light of two or more different colors. Red , green , and blue are the additive primary colors normally used in additive color systems such as projectors, televisions, and computer terminals. Subtractive coloring uses dyes, inks, pigments, or filters to absorb some wavelengths of light and not others. The color that

8700-466: The gamut. Another problem with color reproduction systems is connected with the initial measurement of color, or colorimetry . The characteristics of the color sensors in measurement devices (e.g. cameras, scanners) are often very far from the characteristics of the receptors in the human eye. A color reproduction system "tuned" to a human with normal color vision may give very inaccurate results for other observers, according to color vision deviations to

8816-496: The insoluble iron oxide. The chromate is converted by sulfuric acid into the dichromate. The dichromate is converted to the chromium(III) oxide by reduction with carbon and then reduced in an aluminothermic reaction to chromium. The creation of metal alloys account for 85% of the available chromium's usage. The remainder of chromium is used in the chemical , refractory , and foundry industries. The strengthening effect of forming stable metal carbides at grain boundaries, and

8932-459: The latter cells respond better to some wavelengths than to others, a finding confirmed by subsequent studies. The presence in V4 of orientation-selective cells led to the view that V4 is involved in processing both color and form associated with color but it is worth noting that the orientation selective cells within V4 are more broadly tuned than their counterparts in V1, V2, and V3. Color processing in

9048-503: The layers' thickness. Structural color is studied in the field of thin-film optics . The most ordered or the most changeable structural colors are iridescent . Structural color is responsible for the blues and greens of the feathers of many birds (the blue jay, for example), as well as certain butterfly wings and beetle shells. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, soap bubbles , films of oil, and mother of pearl , because

9164-400: The light is not a pure white source (the case of nearly all forms of artificial lighting), the resulting spectrum will appear a slightly different color. Red paint, viewed under blue light, may appear black . Red paint is red because it scatters only the red components of the spectrum. If red paint is illuminated by blue light, it will be absorbed by the red paint, creating the appearance of

9280-432: The light it receives. Like transparent objects, translucent objects allow light to transmit through, but translucent objects are seen colored because they scatter or absorb certain wavelengths of light via internal scattering. The absorbed light is often dissipated as heat . Although Aristotle and other ancient scientists had already written on the nature of light and color vision , it was not until Newton that light

9396-462: The luster of opals , and the blue of human irises. If the microstructures are aligned in arrays, for example, the array of pits in a CD, they behave as a diffraction grating : the grating reflects different wavelengths in different directions due to interference phenomena, separating mixed "white" light into light of different wavelengths. If the structure is one or more thin layers then it will reflect some wavelengths and transmit others, depending on

9512-526: The majority of transition metals. However, it still has the second highest melting point out of all the period 4 elements , being topped by vanadium by 3 °C (5 °F) at 1910 °C (3470 °F). The boiling point of 2671 °C (4840 °F), however, is comparatively lower, having the fourth lowest boiling point out of the Period 4 transition metals alone behind copper , manganese and zinc . The electrical resistivity of chromium at 20 °C

9628-428: The metal. Chromium metal treated in this way readily dissolves in weak acids. The surface chromia Cr 2 O 3 scale, is adherent to the metal. In contrast, iron forms a more porous oxide which is weak and flakes easily and exposes fresh metal to the air, causing continued rusting . At room temperature, the chromia scale is a few atomic layers thick, growing in thickness by outward diffusion of metal ions across

9744-420: The mid-wavelength (so-called "green") cones; the other cones will inevitably be stimulated to some degree at the same time. The set of all possible tristimulus values determines the human color space . It has been estimated that humans can distinguish roughly 10 million different colors. The other type of light-sensitive cell in the eye, the rod , has a different response curve. In normal situations, when light

9860-437: The most chromatic colors that humans are able to see. The emission or reflectance spectrum of a color is the amount of light of each wavelength that it emits or reflects, in proportion to a given maximum, which has the value of 1 (100%). If the emission or reflectance spectrum of a color is either 0 (0%) or 1 (100%) across the entire visible spectrum, and it has no more than two transitions between 0 and 1, or 1 and 0, then it

9976-514: The national championship for junior players born in 1999-2000 on home ice [8] [9] [10] and in 2017 there was a victory in Oral . [11] Chromium Chromium is a chemical element ; it has symbol Cr and atomic number 24. It is the first element in group 6 . It is a steely-grey, lustrous , hard, and brittle transition metal . Chromium is valued for its high corrosion resistance and hardness . A major development in steel production

10092-426: The native metal. This mine is a kimberlite pipe, rich in diamonds , and the reducing environment helped produce both elemental chromium and diamonds. The relation between Cr(III) and Cr(VI) strongly depends on pH and oxidative properties of the location. In most cases, Cr(III) is the dominating species, but in some areas, the ground water can contain up to 39 μg/L of total chromium, of which 30 μg/L

10208-608: The opponent theory. In 1931, an international group of experts known as the Commission internationale de l'éclairage ( CIE ) developed a mathematical color model, which mapped out the space of observable colors and assigned a set of three numbers to each. The ability of the human eye to distinguish colors is based upon the varying sensitivity of different cells in the retina to light of different wavelengths . Humans are trichromatic —the retina contains three types of color receptor cells, or cones . One type, relatively distinct from

10324-448: The other two, is most responsive to light that is perceived as blue or blue-violet, with wavelengths around 450  nm ; cones of this type are sometimes called short-wavelength cones or S cones (or misleadingly, blue cones ). The other two types are closely related genetically and chemically: middle-wavelength cones , M cones , or green cones are most sensitive to light perceived as green, with wavelengths around 540 nm, while

10440-643: The oxidative roasting of chromite ore with sodium carbonate . The change in equilibrium is visible by a change from yellow (chromate) to orange (dichromate), such as when an acid is added to a neutral solution of potassium chromate . At yet lower pH values, further condensation to more complex oxyanions of chromium is possible. Both the chromate and dichromate anions are strong oxidizing reagents at low pH: They are, however, only moderately oxidizing at high pH: Chromium(VI) compounds in solution can be detected by adding an acidic hydrogen peroxide solution. The unstable dark blue chromium(VI) peroxide (CrO 5 )

10556-446: The oxide in a charcoal oven, for which he is credited as the one who truly discovered the element. Vauquelin was also able to detect traces of chromium in precious gemstones , such as ruby and emerald . During the nineteenth century, chromium was primarily used not only as a component of paints, but in tanning salts as well. For quite some time, the crocoite found in Russia was the main source for such tanning materials. In 1827,

10672-456: The pale green [CrCl(H 2 O) 5 ]Cl 2 and violet [Cr(H 2 O) 6 ]Cl 3 . If anhydrous violet chromium(III) chloride is dissolved in water, the violet solution turns green after some time as the chloride in the inner coordination sphere is replaced by water. This kind of reaction is also observed with solutions of chrome alum and other water-soluble chromium(III) salts. A tetrahedral coordination of chromium(III) has been reported for

10788-488: The population having variants associated with the condition. Synesthesia has also been known to occur with brain damage, drugs, and sensory deprivation. The philosopher Pythagoras experienced synesthesia and provided one of the first written accounts of the condition in approximately 550 BCE. He created mathematical equations for musical notes that could form part of a scale, such as an octave. After exposure to strong light in their sensitivity range, photoreceptors of

10904-415: The principal ions at this oxidation state. They exist at an equilibrium, determined by pH: Chromium(VI) oxyhalides are known also and include chromyl fluoride (CrO 2 F 2 ) and chromyl chloride ( CrO 2 Cl 2 ). However, despite several erroneous claims, chromium hexafluoride (as well as all higher hexahalides) remains unknown, as of 2020. Sodium chromate is produced industrially by

11020-423: The production of pure chromium, the iron must be separated from the chromium in a two step roasting and leaching process. The chromite ore is heated with a mixture of calcium carbonate and sodium carbonate in the presence of air. The chromium is oxidized to the hexavalent form, while the iron forms the stable Fe 2 O 3 . The subsequent leaching at higher elevated temperatures dissolves the chromates and leaves

11136-545: The red end of the spectrum, and it changes to 0 at a given wavelength. In the fourth type, it starts at 0 in the red end of the spectrum, and it changes to 1 at a given wavelength. The first type produces colors that are similar to the spectral colors and follow roughly the horseshoe-shaped portion of the CIE xy chromaticity diagram (the spectral locus ), but are generally more chromatic , although less spectrally pure. The second type produces colors that are similar to (but generally more chromatic and less spectrally pure than)

11252-429: The reduction of chromium(VI) by cytochrome c7 . The Cr ion has a similar radius (63  pm ) to Al (radius 50 pm), and they can replace each other in some compounds, such as in chrome alum and alum . Chromium(III) tends to form octahedral complexes. Commercially available chromium(III) chloride hydrate is the dark green complex [CrCl 2 (H 2 O) 4 ]Cl. Closely related compounds are

11368-409: The reflected color depends upon the viewing angle. Numerous scientists have carried out research in butterfly wings and beetle shells, including Isaac Newton and Robert Hooke. Since 1942, electron micrography has been used, advancing the development of products that exploit structural color, such as " photonic " cosmetics. The gamut of the human color vision is bounded by optimal colors. They are

11484-428: The rest of about 18% of the world production. The two main products of chromium ore refining are ferrochromium and metallic chromium. For those products the ore smelter process differs considerably. For the production of ferrochromium, the chromite ore (FeCr 2 O 4 ) is reduced in large scale in electric arc furnace or in smaller smelters with either aluminium or silicon in an aluminothermic reaction . For

11600-535: The retina, and functional (or strong ) tetrachromats , which are able to make the enhanced color discriminations expected of tetrachromats. In fact, there is only one peer-reviewed report of a functional tetrachromat. It is estimated that while the average person is able to see one million colors, someone with functional tetrachromacy could see a hundred million colors. In certain forms of synesthesia , perceiving letters and numbers ( grapheme–color synesthesia ) or hearing sounds ( chromesthesia ) will evoke

11716-600: The same site as Lehmann and found a red lead mineral that was discovered to possess useful properties as a pigment in paints . After Pallas, the use of Siberian red lead as a paint pigment began to develop rapidly throughout the region. Crocoite would be the principal source of chromium in pigments until the discovery of chromite many years later. In 1794, Louis Nicolas Vauquelin received samples of crocoite ore . He produced chromium trioxide (CrO 3 ) by mixing crocoite with hydrochloric acid . In 1797, Vauquelin discovered that he could isolate metallic chromium by heating

11832-478: The same species. In each such class, the members are called metamers of the color in question. This effect can be visualized by comparing the light sources' spectral power distributions and the resulting colors. The familiar colors of the rainbow in the spectrum —named using the Latin word for appearance or apparition by Isaac Newton in 1671—include all those colors that can be produced by visible light of

11948-442: The scale. Above 950 °C volatile chromium trioxide CrO 3 forms from the chromia scale, limiting the scale thickness and oxidation protection. Chromium, unlike iron and nickel, does not suffer from hydrogen embrittlement . However, it does suffer from nitrogen embrittlement , reacting with nitrogen from air and forming brittle nitrides at the high temperatures necessary to work the metal parts. Naturally occurring chromium

12064-404: The single wavelength of light that produces a sensation most similar to the non-spectral color. Dominant wavelength is roughly akin to hue . There are many color perceptions that by definition cannot be pure spectral colors due to desaturation or because they are purples (mixtures of red and violet light, from opposite ends of the spectrum). Some examples of necessarily non-spectral colors are

12180-414: The solution. During anodization, an oxide layer is formed on the aluminium. The use of chromic acid, instead of the normally used sulfuric acid, leads to a slight difference of these oxide layers. The high toxicity of Cr(VI) compounds, used in the established chromium electroplating process, and the strengthening of safety and environmental regulations demand a search for substitutes for chromium, or at least

12296-410: The spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, there are many more possible spectral combinations than color sensations. In fact, one may formally define a color as a class of spectra that give rise to the same color sensation, although such classes would vary widely among different species, and to a lesser extent among individuals within

12412-455: The standard observer. The different color response of different devices can be problematic if not properly managed. For color information stored and transferred in digital form, color management techniques, such as those based on ICC profiles , can help to avoid distortions of the reproduced colors. Color management does not circumvent the gamut limitations of particular output devices, but can assist in finding good mapping of input colors into

12528-422: The strong increase in corrosion resistance made chromium an important alloying material for steel. High-speed tool steels contain 3–5% chromium. Stainless steel , the primary corrosion-resistant metal alloy, is formed when chromium is introduced to iron in concentrations above 11%. For stainless steel's formation, ferrochromium is added to the molten iron. Also, nickel-based alloys have increased strength due to

12644-437: The three classes of cone cells either being missing, having a shifted spectral sensitivity or having lower responsiveness to incoming light. In addition, cerebral achromatopsia is caused by neural anomalies in those parts of the brain where visual processing takes place. Some colors that appear distinct to an individual with normal color vision will appear metameric to the color blind. The most common form of color blindness

12760-491: The trihalides ( CrX 3 ) with the corresponding halogen at elevated temperatures. Such compounds are susceptible to disproportionation reactions and are not stable in water. Organic compounds containing Cr(IV) state such as chromium tetra t -butoxide are also known. Most chromium(I) compounds are obtained solely by oxidation of electron-rich, octahedral chromium(0) complexes. Other chromium(I) complexes contain cyclopentadienyl ligands. As verified by X-ray diffraction ,

12876-412: The visible light spectrum with three types of cone cells ( trichromacy ). Other animals may have a different number of cone cell types or have eyes sensitive to different wavelengths, such as bees that can distinguish ultraviolet , and thus have a different color sensitivity range. Animal perception of color originates from different light wavelength or spectral sensitivity in cone cell types, which

12992-415: The visual field, the three types of cones yield three signals based on the extent to which each is stimulated. These amounts of stimulation are sometimes called tristimulus values . The response curve as a function of wavelength varies for each type of cone. Because the curves overlap, some tristimulus values do not occur for any incoming light combination. For example, it is not possible to stimulate only

13108-417: Was identified as the source of the color sensation. In 1810, Goethe published his comprehensive Theory of Colors in which he provided a rational description of color experience, which 'tells us how it originates, not what it is'. (Schopenhauer) In 1801 Thomas Young proposed his trichromatic theory , based on the observation that any color could be matched with a combination of three lights. This theory

13224-425: Was later refined by James Clerk Maxwell and Hermann von Helmholtz . As Helmholtz puts it, "the principles of Newton's law of mixture were experimentally confirmed by Maxwell in 1856. Young's theory of color sensations, like so much else that this marvelous investigator achieved in advance of his time, remained unnoticed until Maxwell directed attention to it." At the same time as Helmholtz, Ewald Hering developed

13340-448: Was produced in 2013, and converted into 7.5 Mt of ferrochromium. According to John F. Papp, writing for the USGS, "Ferrochromium is the leading end use of chromite ore, [and] stainless steel is the leading end use of ferrochromium." The largest producers of chromium ore in 2013 have been South Africa (48%), Kazakhstan (13%), Turkey (11%), and India (10%), with several other countries producing

13456-413: Was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel . Stainless steel and chrome plating ( electroplating with chromium) together comprise 85% of the commercial use. Chromium is also greatly valued as a metal that is able to be highly polished while resisting tarnishing . Polished chromium reflects almost 70% of

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