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. [2]
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. [2]
Pb2CrO5 can be synthesized with a gas-liquid precipitation process. [3] Changing the pH controls whether PbCrO4 or Pb2CrO5 is created. [3]
Orthorhombic nanocrystals can be selectively synthesized in a facile room temperature solution for Pb2CrO5. [4]
Using a microwave-assisted ionic liquid (MAIL) method, bundle and rod-like nanocrystals of Pb2CrO5 were formed. [5] The bundles look like bundles of straw, secured in the middle. [5] In basic solution, single-crystalline Pb2CrO5 could be formed by heating lead acetate and potassium dichromate with microwave radiation for only 10 minutes at 90 celsius. [5] The MAIL process is simple, fast, and does not employ surfactants. [5] The presence of hydroxide changes the phase that is formed. Using NaOH, monoclinic Pb2CrO5 is formed. [5] The bundle and rod-shaped structures are sensitive to electron beam irradiation, which will turn them into many small particles. [5]
The Gibbs free energy of Pb2CrO5 was determined in 2010 and is given as
ΔfG°mPb2CrO5(s)±0.30/(kJ•mol−1)=-1161.3 +0.4059(T/K) (859≤T/K≤1021). [6]
Visible light activity up to 550 nanometers has been recorded for Pb2CrO5. [7]
In a catalog published c. 1835, Winsor and Newton paint company identify ten synthetic pathways for producing chrome orange, also called deep yellow. [8] Chrome orange is made of PbCrO4 mixed with basic lead chromate (Pb2CrO5). [8] It has been described as a “yellowish red or sometimes a beautiful deep red” in alkaline conditions. [8] A deep yellow can be created using PbCrO4 and lead sulfate. [8] There are ten synthetic methods for preparing deep chrome yellow (that made with Pb2CrO5), which require a chromate source, a basic lead source, additives, and a sulfate source. [8] CrO42- + H2SO4+Pb(Ac)2 • 2Pb(OH)2 → PbCrO4+Pb2CrO5 at a pH of approximately seven is the synthesis. [8]
Controlling the pH was Winsor and Newton’s method for creating pigments from the pale yellow to the deep chrome orange. [8] The resulting product has a high stability to light, which is always coveted by artists and collectors. [8]
The natural mineral crocoite was discovered in 1797 by Louis Vauquelin and chrome orange was synthesized as a pigment for the first time in 1809. [9] Pb2CrO5 is found in mineral form as phoenicochroite, which is a monoclinic, red, translucent mineral found in various places across the world, including Russia, the USA, and Chile. [10]
| Chrome Orange | |
|---|---|
 Color coordinates | |
| Hex triplet | #E73501 |
| sRGB B (r, g, b) | (231, 53, 1) |
| HSV (h, s, v) | (14°, 100%, 91%) |
| CIELChuv (L, C, h) | (51, 147, 16°) |
| Source | ColourLex [11] |
| B: Normalized to [0–255] (byte) | |
Chrome orange can range in color from light to deep orange and is no longer in production as a pigment. [9] It has also been known as Derby red, Persian red, and Victoria red. [9] It was first recorded as a pigment in 1809 and was perfect for some impressionist painters in the nineteenth century. The yellow-orange pigment of the boat in Renoir’s 1879 painting, The Seine at Asnières (The Skiff) at the National Gallery, London. [9] Chrome orange was used extensively in Frederic Leighton's Flaming June (1895; Museo de Arte de Ponce). [1]
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.
Lead(II) nitrate is an inorganic compound with the chemical formula Pb(NO3)2. It commonly occurs as a colourless crystal or white powder and, unlike most other lead(II) salts, is soluble in water.
Chromic acid is jargon for a solution formed by the addition of sulfuric acid to aqueous solutions of dichromate. It consists at least in part of chromium trioxide.
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.
Wulfenite is a lead molybdate mineral with the formula PbMoO4. It often occurs as thin tabular crystals with a bright orange-red to yellow-orange color, sometimes brown, although the color can be highly variable. In its yellow form it is sometimes called "yellow lead ore".
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.
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.
Crocoite is a mineral consisting of lead chromate, PbCrO4, and crystallizing in the monoclinic crystal system. It is identical in composition with the artificial product chrome yellow used as a paint pigment.
Potassium chromate is the inorganic compound with the formula K2CrO4. This yellow solid is the potassium salt of the chromate anion. It is a common laboratory chemical, whereas sodium chromate is important industrially.
Silver chromate is an inorganic compound with formula Ag2CrO4 which appears as distinctively coloured brown-red crystals. The compound is insoluble and its precipitation is indicative of the reaction between soluble chromate and silver precursor salts (commonly potassium/sodium chromate with silver nitrate). This reaction is important for two uses in the laboratory: in analytical chemistry it constitutes the basis for the Mohr method of argentometry, whereas in neuroscience it is used in the Golgi method of staining neurons for microscopy.
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 is a bright yellow solid that is very poorly soluble in water. It occurs also as the mineral crocoite. It is used as a pigment.
Fornacite is a rare lead, copper chromate arsenate hydroxide mineral with the formula: Pb2Cu(CrO4)(AsO4)(OH). It forms a series with the phosphate mineral vauquelinite. It forms variably green to yellow, translucent to transparent crystals in the monoclinic – prismatic crystal system. It has a Mohs hardness of 2.3 and a specific gravity of 6.27.
Chromium compounds are compounds containing the element chromium (Cr). 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.
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.
Chromium(VI) oxide peroxide is the name given to a collection of chromium coordination complexes. They have the formula CrO(O2)2L where L is a ligand. These species are dark blue and often labile. They all feature oxo ligand and two peroxo ligands, with the remaining coordination sites occupied by water, hydroxide, ether, or other Lewis bases.
The Jones oxidation is an organic reaction for the oxidation of primary and secondary alcohols to carboxylic acids and ketones, respectively. It is named after its discoverer, Sir Ewart Jones. The reaction was an early method for the oxidation of alcohols. Its use has subsided because milder, more selective reagents have been developed, e.g. Collins reagent.
In chemistry, a molybdate is a compound containing an oxyanion with molybdenum in its highest oxidation state of +6: O−−Mo(=O)2−O−. Molybdenum can form a very large range of such oxyanions, which can be discrete structures or polymeric extended structures, although the latter are only found in the solid state. The larger oxyanions are members of group of compounds termed polyoxometalates, and because they contain only one type of metal atom are often called isopolymetalates. The discrete molybdenum oxyanions range in size from the simplest MoO2−
4, found in potassium molybdate up to extremely large structures found in isopoly-molybdenum blues that contain for example 154 Mo atoms. The behaviour of molybdenum is different from the other elements in group 6. Chromium only forms the chromates, CrO2−
4, Cr
2O2−
7, Cr
3O2−
10 and Cr
4O2−
13 ions which are all based on tetrahedral chromium. Tungsten is similar to molybdenum and forms many tungstates containing 6 coordinate tungsten.
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