| Chrome yellow | |
|---|---|
 Colour coordinates | |
| Hex triplet | #FFA700 |
| sRGB B (r, g, b) | (255, 167, 0) |
| HSV (h, s, v) | (39°, 100%, 100%) |
| CIELChuv (L, C, h) | (75, 105, 46°) |
| Source | ColorHexa [1] |
| ISCC–NBS descriptor | Strong orange yellow |
| B: Normalized to [0–255] (byte) | |
Chrome yellow is a bright, warm yellow pigment that has been used in art, fashion, and industry. It is the premier orange pigment for many applications. [2]
The raw pigment precipitates as a fine solid upon mixing lead(II) salts and a source of chromate. Approximately 90,000 tons of chrome yellow are produced annually as of 2001. [2]
Chrome yellow pigments are usually encapsulated by coating with transparent oxides that protect the pigment from environmental factors that would diminish their colorant properties. [2]
Related lead sulfochromate pigments are produced by the replacement of some chromate by sulfate, resulting in a mixed lead-chromate-sulfate compositions Pb(CrO4)1-x(SO4)x. This replacement is possible because sulfate and chromate are isostructural. Since sulfate is colorless, sulfochromates with high values of x are less intensely colored than lead chromate. [3] In some cases, chromate is replaced by molybdate.
Chrome yellow is moderately resistant to fading from exposure to light when it is chemically pure. Observations have found that over time though, it begins to darken and suffer discoloration by turning brown. This degradation is seen in some of Van Gogh's pieces.[ citation needed ] According to Gettens, especially when mixed with organic colors, it can take on a green tone. This effect is attributed to reduction of some chromate to chromium(III) oxide. [5] Owing to its high lead content, the pigment is prone to discoloration over time, particularly in the presence of sulfur compounds. Its low cost had doubtlessly contributed to its continued use as an artists' color even though some subsequently discovered yellow pigments are more permanent. [6] Artists began using cadmium yellow instead of chrome yellow when they became aware of chrome yellow's instability. [7] : 190
The pigment tends to react with hydrogen sulfide and darken on exposure to air over time, forming lead sulfide, [8] and it contains the toxic heavy metal lead plus the toxic, carcinogenic chromate. For these reasons, it was replaced by another pigment, cadmium yellow (mixed with enough cadmium orange to produce a color equivalent to chrome yellow). [5] Darkening may also occur from reduction by sulfur dioxide. Good quality pigments have been coated to inhibit contact with gases that can change their color. [9] Cadmium pigments in turn are increasingly replaced with organic pigments such as arylides (Pigment Yellow 65) and isoindoles (PY 110).
Vincent van Gogh used chrome yellow in many of his paintings, including his famous Sunflowers series. Studies focusing on the techniques used in Van Gogh's Sunflowers series have revealed how Van Gogh skillfully mixed various shades of chrome yellow to achieve different effects. [10] Chrome yellow has also been used in fashion and textiles, particularly in the 1920s and 1930s. The vibrant color was a popular choice for flapper dresses, hats, and accessories, and was often paired with other bright colors, such as pink and turquoise.[ citation needed ]
The pigment is derived from lead chromate, a chemical compound that was first synthesized in the early 1800s. The discovery of lead chromate, the primary component of chrome yellow, is credited to the French chemist Louis Nicolas Vauquelin. Vauquelin was studying the mineral crocoite, a natural form of lead chromate, when he identified the presence of a new element, chromium. The discovery led to the synthesis of a variety of new pigments, including chrome yellow. [11] Chrome yellow quickly gained popularity among artists and designers for its bright, sunny hue, which was particularly well-suited for use in fashion and textiles. The earliest known use of chrome yellow in a painting is a work by Sir Thomas Lawrence from before 1810. [11] The first recorded use of chrome yellow as a color name in English was in 1818. [12] The pigment was also widely used in industrial applications, such as in the production of paint, plastics, and ceramics. [2]
Because it contains not only lead but hexavalent chromium, chrome yellow has long been the focus on safety concerns. Its use is highly regulated. Its former use as a food colorant has long been discontinued. The continued wide use of this pigment is attributed to its very low solubility, which suppresses leaching of chromate and lead into biological fluids. The LD50 for rats is 5 g/kg. [2]
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.
Chrome plating is a technique of electroplating a thin layer of chromium onto a metal object. A chrome plated part is called chrome, or is said to have been chromed. The chromium layer can be decorative, provide corrosion resistance, facilitate cleaning, and increase surface hardness. Sometimes, a less expensive substitute for chrome such as nickel may be used for aesthetic purposes.
Cadmium pigments are a class of pigments that contain cadmium. Most of the cadmium produced worldwide has been for use in rechargeable nickel–cadmium batteries, which have been replaced by other rechargeable nickel-chemistry cell varieties such as NiMH cells, but about half of the remaining consumption of cadmium, which is approximately 2,000 tonnes annually, is used to produce colored cadmium pigments. The principal pigments are a family of yellow, orange and red cadmium sulfides and sulfoselenides, as well as compounds with other metals.
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. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnish may be added to increase the glossiness of the dried oil paint film. The addition of oil or alkyd medium can also be used to modify the viscosity and drying time of oil paint. Oil paints were first used in Asia as early as the 7th century AD and can be seen in examples of Buddhist paintings in Afghanistan. Oil-based paints made their way to Europe by the 12th century and were used for simple decoration, but oil painting did not begin to be adopted as an artistic medium there until the early 15th century. Common modern applications of oil paint are in finishing and protection of wood in buildings and exposed metal structures such as ships and bridges. Its hard-wearing properties and luminous colors make it desirable for both interior and exterior use on wood and metal. Due to its slow-drying properties, it has recently been used in paint-on-glass animation. The thickness of the coat has considerable bearing on the time required for drying: thin coats of oil paint dry relatively quickly.
Potassium dichromate, K2Cr2O7, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health. It is a crystalline ionic solid with a very bright, red-orange color. The salt is popular in laboratories because it is not deliquescent, in contrast to the more industrially relevant salt sodium dichromate.
Plating is a finishing process in which a metal is deposited on a surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve solderability, to harden, to improve wearability, to reduce friction, to improve paint adhesion, to alter conductivity, to improve IR reflectivity, for radiation shielding, and for other purposes. Jewelry typically uses plating to give a silver or gold finish.
School bus yellow is a color that was specifically formulated for use on school buses in North America in 1939. Originally officially named National School Bus Chrome, the color is now officially known in Canada and the U.S. as National School Bus Glossy Yellow.
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.
Chromate conversion coating or alodine coating is a type of conversion coating used to passivate steel, aluminium, zinc, cadmium, copper, silver, titanium, magnesium, and tin alloys. The coating serves as a corrosion inhibitor, as a primer to improve the adherence of paints and adhesives, as a decorative finish, or to preserve electrical conductivity. It also provides some resistance to abrasion and light chemical attack on soft metals.
Zinc chromate, ZnCrO4, is a chemical compound, a salt containing the chromate anion, appearing as odorless yellow powder or yellow-green crystals, but, when used for coatings, pigments are often added. It is used industrially in chromate conversion coatings, having been developed by the Ford Motor Company in the 1920s.
Lead(II) chromate is an inorganic compound with the chemical formula PbCrO4. It has a vivid yellow color and is generally insoluble. Two polymorphs of lead chromate are known, orthorhombic and the more stable monoclinic form. Monoclinic lead chromate is used in paints under the name chrome yellow, and many other names. It occurs also as the mineral crocoite.
Barium chromate, is a yellow sand like powder with the formula BaCrO4. It is a known oxidizing agent and produces a green flame when heated, a result of the barium ions.
Chrome orange is a mixed oxide with the chemical formula Pb2CrO5. It can be made by treating a lead(II) salt with an alkaline solution of a chromate or by treating chrome yellow (PbCrO4) with strongly basic solution.
Chromium toxicity refers to any poisonous toxic effect in an organism or cell that results from exposure to specific forms of chromium—especially hexavalent chromium. Hexavalent chromium and its compounds are toxic when inhaled or ingested. Trivalent chromium is a trace mineral that is essential to human nutrition. There is a hypothetical risk of genotoxicity in humans if large amounts of trivalent chromium were somehow able to enter living cells, but normal metabolism and cell function prevent this.
Strontium chromate is an inorganic compound with the formula SrCrO4.
Green pigments are the materials used to create the green colors seen in painting and the other arts. Most come 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.
Bismuth forms mainly trivalent and a few pentavalent compounds. Many of its chemical properties are similar to those of arsenic and antimony, although much less toxic.
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