Lead(II) chromate

Lead(II) chromate
Xray
Lead(II) chromate
Names
Other names
see text
Identifiers
ChEBI
ECHA InfoCard 100.028.951 Edit this at Wikidata
EC Number
  • 231-846-0
RTECS number
  • GB2975000
UNII
UN number 3288
Properties
PbCrO4
Molar mass 323.192 g/mol
Appearance orange-yellow powder
Density 6.12 g/cm3, solid
Melting point 844 °C (1,551 °F; 1,117 K)
negligible
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 highly toxic
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
Danger
H350, H360, H373, H410
P201, P273, P308+P313, P501
NFPA 704 (fire diamond)
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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Infobox references

Lead(II) chromate is the inorganic compound with the formula (PbCrO4). It has a vivid yellow color and is generally insoluble. 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.

Structure

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.

Applications

Lead chromate is used as the bright yellow pigment in Sunflowers, a painting by van Gogh.

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

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 easy because sulfate and chromate are isostructural. Since sulfate is colorless, sulfochromates with high values of x are less intensely colored than lead chromate.

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− + CrO42−

Safety hazards

Despite containing both lead and hexavalent chromium, lead chromate is not particularly toxic because of its 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.

Previously, its use was more widespread. Lead(II) chromate and "white lead", or lead(II) carbonate, were the most common lead-based paint pigments.

See also


This page was last updated at 2022-09-08 08:01 UTC. Update now. View original page.

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