Lead(II,IV) oxide, also called red lead or

minium ''Minium'' is a genus of thalloid alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. I ...

, is the inorganic compound with the formula Pb3O4. A bright red or orange solid, it is used as

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...

, in the manufacture of

batteries Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

, and

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...

proof primer paints. It is an example of a mixed valence compound, being composed of both Pb(II) and Pb(IV) in the ratio of two to one.

Structure

Lead(II,IV) oxide has a tetragonal crystal structure at

room temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...

, which then transforms to an

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with ...

(

Pearson symbol The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure, and was originated by W. B. Pearson. The symbol is made up of two letters followed by a number. For example: * Diamond structure ...

''oP''28,

Space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

Pbam, No. 55) form at temperature . This phase transition only changes the symmetry of the crystal and slightly modifies the interatomic distances and angles. File:Red-lead-unit-cell-3D-balls.png,

Unit cell In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector, for example) does not necessaril ...

of tetragonal Pb₃O₄
(Key: Pb O) File:Red-lead-3D-balls.png, Part of tetragonal red lead's crystal structure

Preparation

Lead(II,IV) oxide is prepared by

calcination Calcination refers to thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), gen ...

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 ...

(PbO; also called

litharge Litharge (from Greek lithargyros, lithos (stone) + argyros (silver) ''λιθάργυρος'') is one of the natural mineral forms of lead(II) oxide, PbO. Litharge is a secondary mineral which forms from the oxidation of galena ores. It forms as co ...

) in air at about 450–480 °C: :6 PbO + O2 -> 2 Pb3O4 The resulting material is contaminated with PbO. If a pure compound is desired, PbO can be removed by a

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

solution: :PbO + KOH + H2O -> K b(OH)3/chem> Another method of preparation relies on annealing of

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 ...

(

cerussite Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate (PbCO3), and is an important ore of lead. The name is from the Latin ''cerussa'', white lead. ''Cerussa nativa'' was mentioned by Conrad Gess ...

) in air: :6PbCO3 + O2 -> 2Pb3O4 + 6CO2 Yet another method is

oxidative Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

annealing of

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 ...

: :3Pb2CO3(OH)2 + O2 -> 2Pb3O4 + 3CO2 + 3H2O In solution, lead(II,IV) oxide can be prepared by reaction of potassium plumbate with lead(II) acetate, yielding yellow insoluble lead(II,IV) oxide monohydrate Pb3O4.H2O, which can be turned into the anhydrous form by gentle heating: :K2PbO3 + 2Pb(OCOCH3)2 + H2O -> Pb3O4 + 2KOCOCH3 + 2 CH3COOH Natural

is uncommon, forming only in extreme oxidizing conditions of

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 cut, ...

ore bodies. The best known natural specimens come from

Broken Hill Broken Hill is an inland mining city in the far west of outback New South Wales, Australia. It is near the border with South Australia on the crossing of the Barrier Highway (A32) and the Silver City Highway (B79), in the Barrier Range. It ...

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

, Australia, where they formed as the result of a

mine fire A coal-seam fire is a burning of an outcrop or underground coal seam. Most coal-seam fires exhibit smouldering combustion, particularly underground coal-seam fires, because of limited atmospheric oxygen availability. Coal-seam fire instances ...

Reactions

Red lead is virtually insoluble in water and in

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

. However, it is soluble in

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dige ...

present in the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

, and is therefore

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a sub ...

when ingested. It also dissolves in glacial acetic acid and a diluted mixture of

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...

and

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3 ...

. When heated to 500 °C, it decomposes to lead(II) oxide and oxygen. At 580 °C, the reaction is complete. :2Pb3O4 -> 6PbO + O2

Nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...

dissolves the lead(II) oxide component, leaving behind the insoluble

lead(IV) oxide Lead(IV) oxide is the inorganic compound with the formula PbO2. It is an oxide where lead is in an oxidation state of +4. It is a dark-brown solid which is insoluble in water. It exists in two crystalline forms. It has several important applicatio ...

: :Pb3O4 + 4HNO3 -> PbO2 + 2Pb(NO3)2 + 2H2O With iron oxides and with elemental

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

, lead(II,IV) oxide forms insoluble iron(II) and iron(III) plumbates, which is the basis of the anticorrosive properties of lead-based paints applied to iron objects.

Use

Red lead has been used as a

for

primer Primer may refer to: Arts, entertainment, and media Films * ''Primer'' (film), a 2004 feature film written and directed by Shane Carruth * ''Primer'' (video), a documentary about the funk band Living Colour Literature * Primer (textbook), a te ...

paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

s for

objects. Due to its

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

, its use is being limited. It finds limited use in some amateur

pyrotechnics Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition ...

as a delay charge and was used in the past in the manufacture of

dragon's egg ''Dragon's Egg'' is a 1980 hard science fiction novel by American writer Robert L. Forward. In the story, Dragon's Egg is a neutron star with a surface gravity 67 billion times that of Earth, and inhabited by cheela, intelligent creatures ...

pyrotechnic stars. Red lead is used as a curing agent in some

polychloroprene Neoprene (also polychloroprene) is a family of synthetic rubbers that are produced by polymerization of chloroprene.Werner Obrecht, Jean-Pierre Lambert, Michael Happ, Christiane Oppenheimer-Stix, John Dunn and Ralf Krüger "Rubber, 4. Emulsion ...

rubber compounds. It is used in place of

magnesium oxide Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2� ...

to provide better water resistance properties. Red lead was used for engineer's scraping, before being supplanted by

engineer's blue Engineer's blue (also known as scraping blue, Prussian blue, or simply bluing) is a highly pigmented paste used to assist in the mating of two or more components. History Joseph Whitworth popularized the first practical method of making accurat ...

. It is also used as an adultering agent in turmeric powder.

Physiological effects

When inhaled, lead(II,IV) oxide irritates lungs. In case of high dose, the victim experiences a metallic taste, chest pain, and abdominal pain. When ingested, it is dissolved in the

gastric acid Gastric acid, gastric juice, or stomach acid is a digestive fluid formed within the stomach lining. With a pH between 1 and 3, gastric acid plays a key role in digestion of proteins by activating digestive enzymes, which together break down the ...

and absorbed, leading to

lead poisoning Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body. The brain is the most sensitive. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, infertil ...

. High concentrations can be absorbed through skin as well, and it is important to follow safety precautions when working with lead-based paint. Long-term contact with lead(II,IV) oxide may lead to accumulation of lead compounds in organisms, with development of symptoms of acute lead poisoning. Chronic poisoning displays as agitation, irritability, vision disorders,

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...

, and a grayish facial hue. Lead(II,IV) oxide was shown to be

carcinogenic A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive sub ...

for laboratory animals. Its carcinogenicity for humans was not proven.

History

This compound's

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

name ''minium'' originates from the Minius, a river in northwest

Iberia The Iberian Peninsula (), ** * Aragonese language, Aragonese and Occitan language, Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a pe ...

where it was first mined. Lead(II,IV) oxide was used as a red pigment in

ancient Rome In modern historiography, ancient Rome refers to Roman people, Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom ...

, where it was prepared by

. In the ancient and medieval periods it was used as a pigment in the production of

illuminated manuscript An illuminated manuscript is a formally prepared document where the text is often supplemented with flourishes such as borders and miniature illustrations. Often used in the Roman Catholic Church for prayers, liturgical services and psalms, th ...

s, and gave its name to the ''minium'' or

miniature A miniature is a small-scale reproduction, or a small version. It may refer to: * Portrait miniature, a miniature portrait painting * Miniature art, miniature painting, engraving and sculpture * Miniature (chess), a masterful chess game or proble ...

, a style of picture painted with the colour. Made into a paint with

linseed oil Linseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colourless to yellowish oil obtained from the dried, ripened seeds of the flax plant (''Linum usitatissimum''). The oil is obtained by pressing, sometimes followed by ...

, red lead was used as a durable paint to protect exterior ironwork. In 1504 the

portcullis A portcullis (from Old French ''porte coleice'', "sliding gate") is a heavy vertically-closing gate typically found in medieval fortifications, consisting of a latticed grille made of wood, metal, or a combination of the two, which slides down ...

Stirling Castle Stirling Castle, located in Stirling, is one of the largest and most important castles in Scotland, both historically and architecturally. The castle sits atop Castle Hill, an intrusive crag, which forms part of the Stirling Sill geological ...

in Scotland was painted with red lead, as were cannons including Mons Meg. As a finely divided powder, it was also sprinkled on

dielectric In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the ma ...

surfaces to study Lichtenberg figures. In

traditional Chinese medicine Traditional Chinese medicine (TCM) is an alternative medical practice drawn from traditional medicine in China. It has been described as "fraught with pseudoscience", with the majority of its treatments having no logical mechanism of acti ...

, red lead is used to treat ringworms and ulcerations, though the practice is limited due to its toxicity. Also, ''azarcón'', a Mexican folk remedy for gastrointestinal disorders, contains up to 95% lead(II,IV) oxide. It was also used before the 18th century as medicine.

References

External links

National Pollutant Inventory - Lead and Lead Compounds Fact SheetMinium mineral data
{{Oxides Corrosion inhibitors Inorganic pigments Mixed valence compounds Oxides Pyrotechnic oxidizers