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| Names | |
|---|---|
| Other names see text | |
| Identifiers | |
| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.028.951 |
| EC Number |
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| RTECS number |
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| UNII | |
| UN number | 3288 |
| Properties | |
| PbCrO4 | |
| Molar mass | 323.192 g/mol |
| Appearance | bright yellow powder |
| Density | 6.12 g/cm3, solid |
| 0.00001720 g/100 mL (20 °C)[1] | |
| Solubility | soluble in dilutednitric acid insoluble inacetic acid,ammonia |
| −18.0·10−6 cm3/mol | |
Refractive index (nD) | 2.31 |
| Structure | |
| monoclinic | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Moderately toxic, carcinogenic, teratogenic |
| GHS labelling: | |
  | |
| Danger | |
| H350,H360,H373,H410 | |
| P201,P273,P308+P313,P501 | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | >12 g/kg (mouse, oral) |
| Safety data sheet (SDS) | ICSC 0003 Sigma-Aldrich |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Lead(II) chromate is aninorganic compound with thechemical formulaPbCrO4. It is a bright yellow salt that is very poorly soluble in water. It occurs also as the mineralcrocoite. It is used as a pigment.
Twopolymorphs of lead chromate are known, orthorhombic and the more stable monoclinic form. Monoclinic lead chromate is used in paints under the namechrome yellow, and many other names.[2] Lead chromate adopts themonazite structure, meaning that the connectivity of the atoms is very similar to other compounds of the typeMM'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] Unstablepolymorphs of lead chromate are the greenish yellow orthorhombic form and a red-orange tetragonal form.[2]
Approximately 37,000 tons were produced in 1996. The main applications are as a pigment in paints, under the namechrome yellow.[6]
Lead(II) chromate can be produced by treatingsodium chromate with lead salts such aslead(II) nitrate or by combininglead(II) oxide withchromic acid.
Related leadsulfochromate pigments are produced by the replacement of some chromate by sulfate, resulting in a mixed lead-chromate-sulfate compositionsPb(CrO4)1−x(SO4)x. This replacement is possible because sulfate and chromate are isostructural. Since sulfate is colorless, sulfochromates with high values ofx are less intensely colored than lead chromate.[6] In some cases, chromate is replaced bymolybdate.[2]
Heating inhydroxide solution produceschrome red, a red or orange powder made byPbO andCrO3. Also, inhydroxide solution lead chromate slowly dissolves formingplumbite complex.
Despite containing bothlead andhexavalent chromium, lead chromate is not acutely lethal because of its very low solubility. TheLD50 for rats is only 5,000 mg/kg.[clarification needed] 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 ofcandy.[7] It is used (illegally) to enhance the color of certain spices, particularlyturmeric,[8][9] particularly in Bangladesh.[10][11]
Unlike otherlead-based paint pigments, lead chromate is still widely used, especially in road marking paint.[12]
In 2023 and 2024, consumption of adulteratedcinnamon[13] led to at least 136 cases oflead toxicity in children in theUnited States as reported by the USCenters for Disease Control and Prevention.[14] The affected products were recalled.[13] The USFood 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]
