Lead(II) chromate is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the formula ( Pb Cr O₄). 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 __NOTOC__ Chrome yellow is a yellow pigment in paints using monoclinic lead(II) chromate (PbCrO4). It occurs naturally as the mineral crocoite but the mineral ore itself was never used as a pigment for paint. After the French chemist Louis Va ...

. It occurs also as the mineral

crocoite Crocoite is a mineral consisting of lead chromate, Pb Cr O4, and crystallizing in the monoclinic crystal system. It is identical in composition with the artificial product chrome yellow used as a paint pigment. Description Crocoite is commo ...

. 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 Monazite is a primarily reddish-brown phosphate mineral that contains rare-earth elements. Due to variability in composition, monazite is considered a group of minerals. The most common species of the group is monazite-(Ce), that is, the cerium- ...

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

Vincent van Gogh - Sunflowers - VGM F458

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

Preparation

Lead(II) chromate can be produced by treating

sodium chromate Sodium chromate is the inorganic compound with the formula Na2CrO4. It exists as a yellow hygroscopic solid, which can form tetra-, hexa-, and decahydrates. It is an intermediate in the extraction of chromium from its ores. Production and react ...

with lead salts such as

lead(II) nitrate Lead(II) nitrate is an inorganic compound with the chemical formula Pb( NO3)2. It commonly occurs as a colourless crystal or white powder and, unlike most other lead(II) salts, is soluble in water. Known since the Middle Ages by the name plumbum ...

or by combining

lead(II) oxide Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula Pb O. PbO occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern ap ...

with

chromic acid The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of chromic acid may be used as a cleaning mixtu ...

. 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 Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...

solution produces

chrome red Chrome orange is a mixed oxide with the chemical formula Pb2CrO5. It can be made by treating a lead(II) salt with an alkaline solution of a chromate or by treating chrome yellow (PbCrO4) with strongly basic solution.. Synthesis and nanopart ...

, a red or orange powder made by PbO and CrO₃. Also, in

solution lead chromate slowly dissolves forming

plumbite In chemistry, plumbite is the oxyanion or hydrated forms, or any salt containing this anion. In these salts, lead is in the oxidation state +2. It is the traditional term for the IUPAC name plumbate(II). For example, lead(II) oxide (PbO) dissolve ...

complex. ::PbCrO₄ + 4 OH⁻ → b(OH)₄sup>2− + CrO₄²⁻

Safety hazards

Despite containing both

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

and

hexavalent chromium Hexavalent chromium (chromium(VI), Cr(VI), chromium 6) is chromium in any chemical compound that contains the element in the +6 oxidation state (thus hexavalent). Virtually all chromium ore is processed via hexavalent chromium, specifically the ...

, 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. " tensive 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 Candy, also called sweets (British English) or lollies (Australian English Australian English (AusE, AusEng, AuE, AuEng, en-AU) is the set of varieties of the English language native to Australia. It is the country's common language an ...

. It is used (illegally) to enhance the color of certain spices, particularly

turmeric Turmeric () is a flowering plant, ''Curcuma longa'' (), of the ginger family, Zingiberaceae, the rhizomes of which are used in cooking. The plant is a perennial, rhizomatous, herbaceous plant native to the Indian subcontinent and Southeast Asi ...

, particularly in Bangladesh. Previously, its use was more widespread. Lead(II) chromate and "

white lead White lead is the basic lead carbonate 2PbCO3·Pb(OH)2. It is a complex salt, containing both carbonate and hydroxide ions. White lead occurs naturally as a mineral, in which context it is known as hydrocerussite, a hydrate of cerussite. It was ...

", or

lead(II) carbonate Lead(II) carbonate is the chemical compound with the chemical formula . It is a white solid with several practical uses, despite its toxicity. It occurs naturally as the mineral cerussite. Structure Like all metal carbonates, lead(II) carbonate a ...

, were the most common

lead-based paint Lead paint or lead-based paint is paint containing lead. As pigment, lead(II) chromate (, "chrome yellow"), lead(II,IV) oxide, (, "red lead"), and lead(II) carbonate (, "white lead") are the most common forms.. Lead is added to paint to acceler ...

pigments.

References