CompTox Dashboard (EPA)
|Molar mass||323.192 g/mol|
|Density||6.12 g/cm3, solid|
|Melting point||844 °C (1,551 °F; 1,117 K)|
|Solubility||soluble in diluted nitric acid |
insoluble in acetic acid, ammonia
Refractive index (nD)
|Main hazards||Carcinogen and highly toxic|
|Safety data sheet||ICSC 0003|
|GHS Signal word||Danger|
|H350, H360, H373, H410|
|P201, P273, P308+313, P501|
|NFPA 704 (fire diamond)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|>12 g/kg (mouse, oral)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Lead(II) chromate is the inorganic compound with the formula (PbCrO4). It has a vivid yellow color and is insoluble in all solvents. 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. It occurs also as the mineral crocoite.
Lead(II) chromate may also be known as chrome yellow, chromic acid lead(II) salt, canary chrome yellow 40-2250, Holtint Middle Chrome, chrome green, chrome green UC61, chrome green UC74, chrome green UC76, chrome lemon, crocoite, dianichi chrome yellow G, lemon yellow, king's yellow, Leipzig yellow, lemon yellow, Paris yellow, pigment green 15, plumbous chromate, pure lemon chrome L3GS.
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.
Approximately 37,000 tons were produced in 1996. The main applications are as a pigment in paints, under the name chrome yellow. It has also been used in the paint applied to North American school buses.
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 easy because sulfate and chromate are isostructural. Since sulfate is colorless, sulfochromates with high values of x are less intensely colored than lead chromate.
- PbCrO4 + 4 OH− → [Pb(OH)4]2− + CrO42−
Despite containing both lead and hexavalent chromium, lead chromate is not particularly toxic because of it very low solubility. Lead chromate is treated with great care in its manufacture, the main concerns being dust of the chromate precursor. "[E]xtensive epidemiological investigations have given no indication that the practically insoluble lead chromate pigments have any carcinogenic properties".
In the 1800s, the product was used to impart a bright yellow color to some types of candy. It is used (illegally) to enhance the color of certain spices, particularly turmeric, particularly in Bangladesh.
- 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
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- "Researchers find lead in turmeric". Phys. Stanford University. 24 September 2019. Retrieved 1 October 2019.
- 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. doi:10.1016/j.envres.2019.108722. PMID 31550596.