Lead(II) chromate

Last updated
Lead(II) chromate
PbCrO4simple.svg
C.I.77600.jpg
Names
Other names
see text
Identifiers
ChEBI
ECHA InfoCard 100.028.951 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-846-0
PubChem CID
RTECS number
  • GB2975000
UNII
UN number 3288
Properties
PbCrO4
Molar mass 323.192 g/mol
Appearancebright yellow powder
Density 6.12 g/cm3, solid
0.00001720 g/100 mL (20 °C) [1]
Solubility soluble in diluted nitric acid
insoluble in acetic acid, ammonia
−18.0·10−6 cm3/mol
2.31
Structure
monoclinic
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Carcinogen and moderately toxic
GHS labelling:
GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H350, H360, H373, H410
P201, P273, P308+P313, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
0
0
Lethal dose or concentration (LD, LC):
>12 g/kg (mouse, oral)
Safety data sheet (SDS) ICSC 0003
Sigma-Aldrich
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Lead(II) chromate is an inorganic compound with the chemical formula Pb Cr O 4. 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.

Contents

Structure

Structure of PbCrO4 as determined by X-ray crystallography. Color code: red = O, dark gray = Pb, light gray = Cr. PbCrO4.jpg
Structure of PbCrO4 as determined by X-ray crystallography. Color code: red = O, dark gray = Pb, light gray = Cr.

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. [2] Lead chromate adopts the monazite structure, meaning that the connectivity of the atoms is very similar to other compounds of the type MM'O4. Pb(II) has a distorted coordination sphere being surrounded by eight oxides with Pb-O distances ranging from 2.53 to 2.80 Å. The chromate anion is tetrahedral, as usual. [3] Unstable polymorphs of lead chromate are the greenish yellow orthorhombic form and a red-orange tetragonal form. [2]

Applications

Lead chromate is used as the bright yellow pigment in Sunflowers, a painting by Vincent van Gogh. Vincent van Gogh - Sunflowers - VGM F458.jpg
Lead chromate is used as the bright yellow pigment in Sunflowers , a painting by Vincent van Gogh.

Approximately 37,000 tons were produced in 1996. The main applications are as a pigment in paints, under the name chrome yellow. [6]

Preparation

Lead(II) chromate can be produced by treating sodium chromate with lead salts such as lead(II) nitrate or by combining lead(II) oxide with chromic acid.

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. [6] In some cases, chromate is replaced by molybdate. [2]

Reactions

Heating in hydroxide solution produces chrome red, a red or orange powder made by PbO and CrO3. Also, in hydroxide solution lead chromate slowly dissolves forming plumbite complex.

PbCrO4 + 4 OH− → [Pb(OH)4]2− + CrO2−4

Safety hazards

Despite containing both lead and hexavalent chromium, lead chromate is not acutely lethal because of its very low solubility. The LD50 for rats is only 5,000 mg/kg. Lead chromate must be treated with great care in its manufacture, the main concerns being dust of the chromate precursor. Lead chromate is highly regulated in advanced countries. As one of the greatest threats comes from inhalation of particles, so much effort has been devoted to production of low-dust forms of the pigment. [2]

In the 1800s, the product was used to impart a bright yellow color to some types of candy. [7] It is used (illegally) to enhance the color of certain spices, particularly turmeric, [8] [9] particularly in Bangladesh. [10] [11]

Unlike other lead-based paint pigments, lead chromate is still widely used, especially in road marking paint. [12]

In 2023 and 2024, consumption of adulterated cinnamon [13] led to at least 136 cases of lead toxicity in children in the United States as reported by the US Centers for Disease Control and Prevention. [14] The affected products were recalled. [13] The US Food and Drug Administration determined that the ratio of lead to chromium in the cinammon indicated that lead chromate had been added to the cinnamon. [13]

See also

Related Research Articles

<span class="mw-page-title-main">Chromium</span> Chemical element with atomic number 24 (Cr)

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.

<span class="mw-page-title-main">Lead(II) nitrate</span> Chemical compound

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.

<span class="mw-page-title-main">Chromate and dichromate</span> Chromium(VI) anions

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.

<span class="mw-page-title-main">Potassium dichromate</span> Chemical compound

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.

<span class="mw-page-title-main">Crocoite</span> Lead chromate mineral

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.

<span class="mw-page-title-main">Potassium chromate</span> Chemical compound

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.

<span class="mw-page-title-main">Chromate conversion coating</span> Chemical treatment of metals

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.

<span class="mw-page-title-main">Silver chromate</span> Chemical compound

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.

<span class="mw-page-title-main">Caesium chromate</span> Chemical compound

Caesium chromate or cesium chromate is an inorganic compound with the formula Cs2CrO4. It is a yellow crystalline solid that is the caesium salt of chromic acid, and it crystallises in the orthorhombic system.

<span class="mw-page-title-main">Chromium compounds</span> Chemical compounds containing chromium

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.

<span class="mw-page-title-main">Barium chromate</span> Chemical compound

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.

<span class="mw-page-title-main">Chrome orange</span> Chemical compound and inorganic pigment

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.

<span class="mw-page-title-main">Chromium(III) sulfate</span> Chemical compound

Chromium(III) sulfate usually refers to the inorganic compounds with the formula Cr2(SO4)3.x(H2O), where x can range from 0 to 18. Additionally, ill-defined but commercially important "basic chromium sulfates" are known. These salts are usually either violet or green solids that are soluble in water. It is commonly used in tanning leather.

<span class="mw-page-title-main">Nickel(II) chromate</span> Chemical compound

Nickel(II) chromate (NiCrO4) is an acid-soluble compound, red-brown in color, with high tolerances for heat. It and the ions that compose it have been linked to tumor formation and gene mutation, particularly to wildlife.

<span class="mw-page-title-main">Sodium chromate</span> Chemical compound

Sodium chromate is the inorganic compound with the formula Na2CrO4. It exists as a yellow hygroscopic solid, which can form tetra-, hexa-, and decahydrates. It is an intermediate in the extraction of chromium from its ores.

Beryllium chromate is a hypothetical inorganic compound, with the chemical formula of BeCrO4. It is predicted to have a certain bonding ability with noble gases. Little evidence has been published supporting the existence of this material.

References

  1. ↑ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN   0-8493-0487-3.
  2. 1 2 3 4 Erkens, LJH; Hamers, H.; Hermans, RJM; Claeys, E.; Bijnens, M. (2001). "Lead chromates: A Review of the State of the Art in 2000". Surface Coatings International Part B: Coatings Transactions. 84 (3): 169–176. doi:10.1007/BF02700395. S2CID   94606296.
  3. ↑ Quareni, S.; de Pieri, R. "A Three-Dimensional Refinement of the Structure of Crocoite, PbCrO4" Acta Crystallographica 1965, volume 19, p287-p289. doi : 10.1107/S0365110X65003304
  4. ↑ "Sunflowers - Van Gogh Museum". vangoghmuseum.nl. Archived from the original on 29 October 2016. Retrieved 21 September 2016.
  5. ↑ Monico, Letizia; Janssens, Koen; Hendriks, Ella; Vanmeert, Frederik; Van Der Snickt, Geert; Cotte, Marine; Falkenberg, Gerald; Brunetti, Brunetto Giovanni; Miliani, Costanza (2015). "Evidence for Degradation of the Chrome Yellows in Van Gogh's Sunflowers: A Study Using Noninvasive In Situ Methods and Synchrotron-Radiation-Based X-ray Techniques". Angewandte Chemie International Edition. 54 (47): 13923–13927. doi:10.1002/anie.201505840. PMID   26482035. S2CID   2268072.
  6. 1 2 Völz, Hans G.; et al. (2006). "Pigments, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_243.pub2. ISBN   978-3527306732.
  7. ↑ Wisconsin. State Board of Health (1887). Progress Report of Public Health in Wisconsin, Volume 10. p. 92. Retrieved 17 July 2013. (Google Books)
  8. ↑ "The American Spice Trade Association's Statement on Lead in Turmeric - ASTA: The Voice of the U.S. Spice Industry in the Global Market". ASTA: The Voice of the U.S. Spice Industry in the Global Market. 28 October 2013. Retrieved 21 November 2018.
  9. ↑ Angelon-Gaetz, Kim A.; Klaus, Christen; Chaudhry, Ezan A.; Bean, Deidre K. (23 November 2018). "Lead in Spices, Herbal Remedies, and Ceremonial Powders Sampled from Home Investigations for Children with Elevated Blood Lead Levels — North Carolina, 2011–2018". MMWR. Morbidity and Mortality Weekly Report. 67 (46): 1290–1294. doi:10.15585/mmwr.mm6746a2. ISSN   0149-2195. PMC   6289082 . PMID   30462630.
  10. ↑ "Researchers find lead in turmeric". Phys. Stanford University. 24 September 2019. Retrieved 1 October 2019.
  11. ↑ Forsyth, Jenna E.; Nurunnahar, Syeda; Islam, Sheikh Shariful; Baker, Musa; Yeasmin, Dalia; Islam, M. Saiful; Rahman, Mahbubur; Fendorf, Scott; Ardoin, Nicole M.; Winch, Peter J.; Luby, Stephen P. (December 2019). "Turmeric means "yellow" in Bengali: Lead chromate pigments added to turmeric threaten public health across Bangladesh". Environmental Research. 179 (Pt A): 108722. Bibcode:2019ER....179j8722F. doi: 10.1016/j.envres.2019.108722 . PMID   31550596.
  12. ↑ "Lead Chromate: Why it is Banned in Most Industries Apart From Road Markings". Road Traffic Technology. Verdict Media Limited. Retrieved 2024-05-27.
  13. 1 2 3 "Investigation of Elevated Lead & Chromium Levels: Cinnamon Applesauce Pouches (November 2023)". Food and Drug Administration . 16 April 2024. Retrieved 27 May 2024.
  14. ↑ "Lead and Chromium Poisoning Outbreak Linked to Cinnamon Applesauce Pouches". 17 April 2024. Retrieved 27 May 2024.
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