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Chrome orange is amixed oxide with thechemical formula Pb2CrO5. It can be made by treating a lead(II) salt with an alkaline solution of achromate or by treatingchrome yellow (PbCrO4) with strongly basic solution.[2]
Pb2CrO5 can be synthesized with agas-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 amicrowave-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]
TheGibbs 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 ofPbCrO4 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 apH 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 byLouis Vauquelin and chrome orange was synthesized as a pigment for the first time in 1809.[9] Pb2CrO5 is found in mineral form asphoenicochroite, which is amonoclinic, red, translucent mineral found in various places across the world, including Russia, the US, and Chile.[10]
| Chrome Orange | |
|---|---|
 Color coordinates | |
| Hex triplet | #E73501 |
| sRGBB (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 inRenoir’s 1879 painting, The Seine at Asnières (The Skiff) at theNational Gallery, London.[9] Chrome orange was used extensively inFrederic Leighton'sFlaming June (1895;Museo de Arte de Ponce).[1]
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