lead(II) chromate

Image:PbCrO4.jpg. 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.{{cite journal |doi=10.1007/BF02700395 |title=Lead chromates: A Review of the State of the Art in 2000 |date=2001 |last1=Erkens |first1=LJH |last2=Hamers |first2=H. |last3=Hermans |first3=RJM |last4=Claeys |first4=E. |last5=Bijnens |first5=M. |journal=Surface Coatings International Part B: Coatings Transactions |volume=84 |issue=3 |pages=169–176 |s2cid=94606296}} Lead chromate adopts the monazite structure, meaning that the connectivity of the atoms is very similar to other compounds of the type {{chem2|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.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}} Unstable polymorphs of lead chromate are the greenish yellow orthorhombic form and a red-orange tetragonal form.

File:Vincent van Gogh - Sunflowers - VGM F458.jpg, a painting by Vincent van Gogh.{{cite web|url=https://www.vangoghmuseum.nl/en/collection/s0031V1962|title=Sunflowers - Van Gogh Museum|website=vangoghmuseum.nl|access-date=21 September 2016|archive-url=https://web.archive.org/web/20161029112559/https://www.vangoghmuseum.nl/en/collection/s0031V1962|archive-date=29 October 2016|url-status=live}}{{cite journal |doi=10.1002/anie.201505840|title=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|year=2015|last1=Monico|first1=Letizia|last2=Janssens|first2=Koen|last3=Hendriks|first3=Ella|last4=Vanmeert|first4=Frederik|last5=Van Der Snickt|first5=Geert|last6=Cotte|first6=Marine|last7=Falkenberg|first7=Gerald|last8=Brunetti|first8=Brunetto Giovanni|last9=Miliani|first9=Costanza|journal=Angewandte Chemie International Edition|volume=54|issue=47|pages=13923–13927|pmid=26482035|s2cid=2268072}}]]

Approximately 37,000 tons were produced in 1996. The main applications are as a pigment in paints, under the name chrome yellow.{{Ullmann|author=Völz, Hans G.|display-authors=etal|title=Pigments, Inorganic|year=2006|doi=10.1002/14356007.a20_243.pub2}}

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 {{chem2|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. In some cases, chromate is replaced by molybdate.

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

:{{chem2|PbCrO4 + 4 OH− → [Pb(OH)4](2−) + CrO4(2−)}}

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.{{clarify|date=March 2025}} 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.

In the 1800s, the product was used to impart a bright yellow color to some types of candy.{{cite book|title=Progress Report of Public Health in Wisconsin, Volume 10|year=1887|page=92|url=https://books.google.com/books?id=aC9NAAAAMAAJ&dq=%22chromate+of+lead%22+candy&pg=PA93|author=Wisconsin. State Board of Health|accessdate=17 July 2013}} (Google Books) It is used (illegally) to enhance the color of certain spices, particularly turmeric,{{cite web |title=The American Spice Trade Association's Statement on Lead in Turmeric - ASTA: The Voice of the U.S. Spice Industry in the Global Market |url=https://www.astaspice.org/the-american-spice-trade-associations-statement-on-lead-in-turmeric/ |website=ASTA: The Voice of the U.S. Spice Industry in the Global Market |accessdate=21 November 2018 |date=28 October 2013}}{{cite journal |last1=Angelon-Gaetz |first1=Kim A. |last2=Klaus |first2=Christen |last3=Chaudhry |first3=Ezan A. |last4=Bean |first4=Deidre K. |title=Lead in Spices, Herbal Remedies, and Ceremonial Powders Sampled from Home Investigations for Children with Elevated Blood Lead Levels — North Carolina, 2011–2018 |journal=MMWR. Morbidity and Mortality Weekly Report |date=23 November 2018 |volume=67 |issue=46 |pages=1290–1294 |doi=10.15585/mmwr.mm6746a2 |pmid=30462630 |language=en-us |issn=0149-2195|pmc=6289082}} particularly in Bangladesh.{{cite news|url=https://phys.org/news/2019-09-turmeric.html|title=Researchers find lead in turmeric|work=Phys|agency=Stanford University|date=24 September 2019|access-date=1 October 2019}}{{cite journal |last1=Forsyth |first1=Jenna E. |last2=Nurunnahar |first2=Syeda |last3=Islam |first3=Sheikh Shariful |last4=Baker |first4=Musa |last5=Yeasmin |first5=Dalia |last6=Islam |first6=M. Saiful |last7=Rahman |first7=Mahbubur |last8=Fendorf |first8=Scott |last9=Ardoin |first9=Nicole M. |last10=Winch |first10=Peter J. |last11=Luby |first11=Stephen P. |title=Turmeric means "yellow" in Bengali: Lead chromate pigments added to turmeric threaten public health across Bangladesh |journal=Environmental Research |date=December 2019 |volume=179 |issue=Pt A |pages=108722 |doi=10.1016/j.envres.2019.108722 |pmid=31550596 |bibcode=2019ER....179j8722F |doi-access=free}}

Unlike other lead-based paint pigments, lead chromate is still widely used, especially in road marking paint.{{cite web |title=Lead Chromate: Why it is Banned in Most Industries Apart From Road Markings |url=https://www.roadtraffic-technology.com/contractors/road_marking/prismo2/pressreleases/presslead-chromate-why-it-is-banned-in-most-industries-apart-from-road-markings/ |website=Road Traffic Technology |publisher=Verdict Media Limited |access-date=2024-05-27}}

In 2023 and 2024, consumption of adulterated cinnamon{{Cite web|url=https://www.fda.gov/food/outbreaks-foodborne-illness/investigation-elevated-lead-chromium-levels-cinnamon-applesauce-pouches-november-2023|title=Investigation of Elevated Lead & Chromium Levels: Cinnamon Applesauce Pouches (November 2023)|website=Food and Drug Administration |date=16 April 2024|access-date=27 May 2024}} 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.{{Cite web|url=https://www.cdc.gov/lead-prevention/news/outbreak-applesauce-pouches.html|title=Lead and Chromium Poisoning Outbreak Linked to Cinnamon Applesauce Pouches|date=17 April 2024|access-date=27 May 2024}} The affected products were recalled. 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.

• Crocoite
• Iranite

• [https://web.archive.org/web/20031220124103/http://physchem.ox.ac.uk/MSDS/LE/lead_chromate.html Safety (MSDS) data for lead chromate]
• [http://www.scorecard.org/chemical-profiles/summary.tcl?edf_substance_id=7758-97-6 Chemical Profile for lead chromate]
• [http://hazard.com/msds/mf/baker/baker/files/l2869.htm J.T. Baker MSDS]

{{reflist}}

{{Lead compounds}}

{{Chromates and dichromates}}

Category:Chromates

Category:Lead(II) compounds

Category:Pyrotechnic oxidizers

Category:Environmental impact of paint

Category:Oxidizing agents