Lead(II) chromate

Lead(II) chromate
Other names see text
Identifiers
CAS number	7758-97-6 Y
EC number	231-846-0
UN number	3288
RTECS number	GB2975000
Properties
Molecular formula	PbCrO4
Molar mass	323.2 g/mol
Appearance	orange-yellow powder
Density	6.3 g/cm3, solid
Melting point	844 °C
Solubility in water	negligible
Hazards
MSDS	ICSC 0003
EU Index	082-004-00-2
EU classification	Carc. Cat. 2 Repr. Cat. 1/3 Toxic (T) Dangerous for the environment (N)
R-phrases	R45, R61, R33, R62, R50/53
S-phrases	S53, S45, S60, S61
NFPA 704	0 3 0
Y chromate (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Lead(II) chromate (PbCrO₄) is a chemical compound, a chromate of lead. It has a vivid yellow color and is practically insoluble in water, and as a result, is used in paints under the name "chrome yellow". It is commonly made in the laboratory by reacting a lead(II) salt (such as lead(II) nitrate) with a chromate or dichromate salt (such as potassium chromate or potassium dichromate) in solution in water, producing a very deep yellow to orange precipitate of lead(II) chromate.

Lead(II) chromate may also be known as chrome yellow, chromic acid lead(II) salt, canary chrome yellow 40-2250, 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, and various other names. The mineral crocoite, occurring as orange-yellow prismatic crystals, is a moderately rare mineral known from the oxidation zones of such Pb ore beds, that were affected by chromate-bearing solutions, coming from the oxidation of primary Cr minerals (chromite) of the nearby (ultra)mafic rocks.

Lead(II) chromate can be destroyed by strong reducing agents, combustibles, and organic materials.

Applications

Lead(II) chromate is used in some pyrotechnic compositions, especially delay compositions, as an oxidizer. Up to the late 1800s it was used to impart a bright yellow color to some types of candy.[1]

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

Reactions

Heating in hydroxide solution produces chrome red, a red or orange powder made by PbO and CrO₃.

Also, in hydroxide solution lead chromate partially dissolves forming plumbite complex.

PbCrO₄ + 4 OH^-   →   [Pb(OH)₄]^2- + CrO₄^2-

Safety hazards

Due to containing both lead and hexavalent chromium, lead(II) chromate is profoundly toxic.

Lead(II) chromate is a poison, and can be fatal if swallowed or inhaled.

Lead(II) chromate is a known carcinogen, developmental toxicant, and reproductive toxicant. It is also suspected that lead(II) chromate is a cardivascular or blood toxicant, immunotoxicant, kidney toxicant, neurotoxicant, respiratory toxicant, and a skin toxicant or sense organ toxicant.

If swallowed

If swallowed, lead(II) chromate poisoning can lead to abdominal pain and spasms, nausea, vomiting, and headaches. If the poisoning is not severe, one may experience lead line on the gums, a metallic taste, muscle weakness, and dizziness. The symptoms appear to get worse as the poisoning becomes more severe. Severe poisoning can lead to a coma and even death.

If inhaled

If inhaled, and the poisoning is not severe, one may experience symptoms such as a sore throat, coughing, shortness of breath, and labored breathing. Severe poisoning may lead to pulmonary edema, as well as several symptoms experienced from indigestion

References

• Safety (MSDS) data for lead chromate
• Chemical Profile for lead chromate
• J.T. Baker MSDS