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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.
A pigment is a powder used to add color or change visual appearance. Pigments are completely or nearly insoluble and chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go into solution at some stage in their use. Dyes are often organic compounds whereas pigments are often inorganic. Pigments of prehistoric and historic value include ochre, charcoal, and lapis lazuli.
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.
A period 4 element is one of the chemical elements in the fourth row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The fourth period contains 18 elements beginning with potassium and ending with krypton – one element for each of the eighteen groups. It sees the first appearance of d-block in the table.
Chromate salts contain the chromate anion, CrO2−
4. Dichromate salts contain the dichromate anion, Cr
2O2−
7. They are oxyanions of chromium in the +6 oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible.
Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. Oil paint also has practical advantages over other paints, mainly because it is waterproof.
Zinc sulfide is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite. Although this mineral is usually black because of various impurities, the pure material is white, and it is widely used as a pigment. In its dense synthetic form, zinc sulfide can be transparent, and it is used as a window for visible optics and infrared optics.
Lithopone, C.I. Pigment White 5, is a mixture of inorganic compounds, widely used as a white pigment powder. It is composed of a mixture of barium sulfate and zinc sulfide. These insoluble compounds blend well with organic compounds and confer opacity. It was made popular by the cheap production costs, greater coverage. Related white pigments include titanium dioxide, zinc oxide, zinc sulfide, and white lead.
Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find the elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, therefore materials in other forms may need to be brought to this state before using standard methods. The solution is then treated with various reagents to test for reactions characteristic of certain ions, which may cause color change, precipitation and other visible changes.
Adamite is a zinc arsenate hydroxide mineral, Zn2AsO4OH. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Pure adamite is colorless, but usually it possess yellow color due to Fe compounds admixture. Tints of green also occur and are connected with copper substitutions in the mineral structure. Olivenite is a copper arsenate that is isostructural with adamite and there is considerable substitution between zinc and copper resulting in an intermediate called cuproadamite. Zincolivenite is a recently discovered mineral being an intermediate mineral with formula CuZn(AsO4)(OH). Manganese, cobalt, and nickel also substitute in the structure. An analogous zinc phosphate, tarbuttite, is known.
Naples yellow, also called antimony yellow or lead antimonate yellow, is an inorganic pigment that largely replaced lead-tin-yellow and has been used in European paintings since the seventeenth century. While the mineral orpiment is considered to be the oldest yellow pigment, Naples yellow, like Egyptian blue, is one of the oldest known synthetic pigments. Naples yellow was used in ancient Egypt and Mesopotamia, finding widespread application during the Hellenistic and Roman periods. Prior to its earliest occurrences in European paintings, the pigment was commonly employed in pottery, glazes, enamels, and glass. The pigment ranged in hue from a muted, earthy, reddish yellow to a bright light yellow.
Cobalt green is an ambiguous term for either of two families of green inorganic pigments. Both are obtained by doping cobalt(II) oxide into colorless host oxides.
A native metal is any metal that is found pure in its metallic form in nature. Metals that can be found as native deposits singly or in alloys include antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, manganese, molybdenum, nickel, niobium, rhenium, tantalum, tellurium, tin, titanium, tungsten, vanadium, and zinc, as well as the gold group and the platinum group. Among the alloys found in native state have been brass, bronze, pewter, German silver, osmiridium, electrum, white gold, silver-mercury amalgam, and gold-mercury amalgam.
Fluxes are substances, usually oxides, used in glasses, glazes and ceramic bodies to lower the high melting point of the main glass forming constituents, usually silica and alumina. A ceramic flux functions by promoting partial or complete liquefaction. The most commonly used fluxing oxides in a ceramic glaze contain lead, sodium, potassium, lithium, calcium, magnesium, barium, zinc, strontium, and manganese. These are introduced to the raw glaze as compounds, for example lead as lead oxide. Boron is considered by many to be a glass former rather than a flux.
Glass coloring and color marking may be obtained in several ways.
- by the addition of coloring ions,
- by precipitation of nanometer-sized colloids,
Ancient Roman enamelled glass, 1st century, Treasure of Begram - by colored inclusions
- by light scattering
- by dichroic coatings, or
- by colored coatings
Red pigments are materials, usually made from minerals, used to create the red colors in painting and other arts. The color of red and other pigments is determined by the way it absorbs certain parts of the spectrum of visible light and reflects the others. The brilliant opaque red of vermillion, for example, results because vermillion reflects the major part of red light, but absorbs the blue, green and yellow parts of white light.
Green pigments are the materials used to create the green colors seen in painting and the other arts. At one time, such pigments came from minerals, particularly those containing compounds of copper. Green pigments reflect the green portions of the spectrum of visible light, and absorb the others. Important green pigments in art history include Malachite and Verdigris, found in tomb paintings in Ancient Egypt, and the Green earth pigments popular in the Middle Ages. More recent greens, such as Cobalt Green, are largely synthetic, made in laboratories and factories. Today, the main green pigment is Phthalocyanine Green G.
References
- 1 2 Völz, Hans G.; et al. "Pigments, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_243.pub2. ISBN 978-3-527-30673-2..
- ↑ Müller, Hugo; Müller, Wolfgang; Wehner, Manfred; Liewald, Heike. "Artists' Colors". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_143.pub2. ISBN 978-3-527-30673-2.
- ↑ Smith, Andrew E.; Mizoguchi, Hiroshi; Delaney, Kris; Spaldin, Nicola A.; Sleight, Arthur W.; Subramanian, M. A. (2009). "Mn3+ in Trigonal Bipyramidal Coordination: A New Blue Chromophore". J. Am. Chem. Soc. 131 (47): 17084–17086. doi:10.1021/ja9080666. PMID 19899792.