Red lead
Encyclopedia
Lead tetroxide, also called minium, red lead or triplumbic tetroxide, is a bright red or orange crystalline or amorphous pigment
. Chemically, red lead is lead tetroxide
, Pb3O4, or 2PbO·PbO2.
This compound's Latin
name minium originates from the Minius River in northwest Spain
where it was first mined. Natural minium
is uncommon, forming only in extreme oxidizing conditions of lead
ore bodies. The best specimens known come from Broken Hill, New South Wales
, Australia
, where they formed as the result of a mine fire.
Lead tetroxide is used in the manufacture of batteries, lead glass
and rust
-proof primer paints
.
oP28, Space group
= Pbam, No 55) form at temperature 170 K. This phase transition only changes the symmetry of the crystal and slightly modifies the interatomic distances and angles.
of lead(II) oxide
(also called litharge
) in air at about 450 to 480 °C:
The resulting material is contaminated with lead(II) oxide. If a pure compound is desired, PbO can be removed by a potassium hydroxide
solution:
Another method of preparation relies on annealing of lead carbonate
(cerussite
) in air:
Yet another method is oxidative annealing of white lead
:
In solution, lead tetroxide can be prepared e.g. by reaction of potassium plumbate with lead acetate
, yielding yellow insoluble lead tetroxide monohydrate, Pb3O4·H2O, which can be turned into the anhydrous form by gentle heating:
present in the stomach
, and is therefore toxic when ingested. It also dissolves in glacial acetic acid and a diluted mixture of nitric acid
and hydrogen peroxide
.
When heated to 500 °C, it decomposes to lead(II) oxide and oxygen. At 580 °C, the reaction is complete.
Nitric acid
dissolves the lead tetroxide component, leaving behind the insoluble lead(IV) oxide:
With iron oxides and with elemental iron
, lead tetroxide forms insoluble iron(II) and iron(III) plumbate
s, which is the basis of the anti-corrosive
properties of lead-based paints applied to iron objects.
for primer
paint
s for iron
objects. Due to its toxicity
, its use is being limited. In the past, it was used in combination with linseed oil
as a thick, long-lasting anti-corrosive paint. The combination of minium and linen fibres was also used for plumbing
, now replaced with PTFE tape. Currently it is mostly used for manufacture of glass
, especially lead glass
. It finds limited use in some amateur pyrotechnics
as a relatively potent oxidizer.
Red lead was also used for engineer's scraping
, before being supplanted by Engineer's blue
. In traditional Chinese medicine
, red lead is used to treat ringworms and ulceration
s, though the practice is limited due to its toxicity.
and absorbed, leading to lead poisoning. 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 tetroxide 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
, and also a grayish facial hue.
Lead tetroxide was shown to be carcinogenic for laboratory animals. Its carcinogenicity for humans was not proven.
, where it was prepared by calcination
of white lead
. In the ancient and medieval periods it was used as a pigment in the production of illuminated manuscript
s, and gave its name to the minium or miniature
, a style of picture painted with the colour. As a finely divided powder, it was also sprinkled on dielectric
surfaces to study Lichtenberg figures.
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
. Chemically, red lead is lead tetroxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
, Pb3O4, or 2PbO·PbO2.
This compound's Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
name minium originates from the Minius River in northwest Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
where it was first mined. Natural minium
Minium (mineral)
Minium is the naturally occurring form of lead tetroxide, Pb2+2Pb4+O4. It is a light to vivid red and may have brown to yellow tints. It typically occurs as scaly to earthy masses. It crystallizes in the tetragonal crystal system....
is uncommon, forming only in extreme oxidizing conditions of lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
ore bodies. The best specimens known come from Broken Hill, New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, where they formed as the result of a mine fire.
Lead tetroxide is used in the manufacture of batteries, lead glass
Lead glass
Lead glass is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40 weight% lead oxide , while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO...
and rust
Rust
Rust is a general term for a series of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture...
-proof primer paints
Primer (paint)
A primer is a preparatory coating put on materials before painting. Priming ensures better adhesion of paint to the surface, increases paint durability, and provides additional protection for the material being painted.-When primers are used:...
.
Structure
Lead tetroxide has a tetragonal crystal structure at room temperature, which transforms to an orthorhombic (Pearson symbolPearson 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, cF8...
oP28, Space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
= Pbam, No 55) form at temperature 170 K. This phase transition only changes the symmetry of the crystal and slightly modifies the interatomic distances and angles.
Preparation
Lead tetroxide is prepared by calcinationCalcination
Calcination is a thermal treatment process applied to ores and other solid materials to bring about a thermal decomposition, phase transition, or removal of a volatile fraction. The calcination process normally takes place at temperatures below the melting point of the product materials...
of lead(II) oxide
Lead(II) oxide
Lead oxide is the inorganic compound with the formula PbO. Lead oxide occurs in two polymorphs, red, having a tetragonal crystal structure and yellow, having an orthorhombic crystal structure...
(also called litharge
Litharge
Litharge is one of the natural mineral forms of lead oxide, PbO. Litharge is a secondary mineral which forms from the oxidation of galena ores. It forms as coatings and encrustations with internal tetragonal crystal structure. It is dimorphous with the orthorhombic form massicot...
) in air at about 450 to 480 °C:
- 6 PbO + O2 → 2 Pb3O4
The resulting material is contaminated with lead(II) oxide. If a pure compound is desired, PbO can be removed by a potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
solution:
- PbO + KOH + H2O → K[Pb(OH)3] (aq)
Another method of preparation relies on annealing of lead carbonate
Lead carbonate
Lead carbonate is the chemical compound PbCO3. It is prepared industrially from lead acetate and carbon dioxide.It occurs naturally as the mineral cerussite.-Basic lead carbonates:...
(cerussite
Cerussite
Cerussite is a mineral consisting of lead carbonate , and an important ore of lead. The name is from the Latin cerussa, white lead. Cerussa nativa was mentioned by Conrad Gessner in 1565, and in 1832 F. S. Beudant applied the name cruse to the mineral, whilst the present form, cerussite, is due to...
) in air:
- 6 PbCO3 + O2 → 2 Pb3O4 + 6 CO2
Yet another method is oxidative annealing of white lead
White lead
White lead is the chemical compound 2·Pb2. It was formerly used as an ingredient for lead paint and a cosmetic called Venetian Ceruse, because its opaque quality made it a good pigment. However, it tended to cause lead poisoning, and its use has been banned in most countries.White lead has been...
:
- 3 Pb2CO3(OH)2 + O2 → 2 Pb3O4 + 3 CO2 + 3 H2O
In solution, lead tetroxide can be prepared e.g. by reaction of potassium plumbate with lead acetate
Lead acetate
Lead acetate can refer to:* Lead acetate , Pb4* Lead acetate , Pb2...
, yielding yellow insoluble lead tetroxide monohydrate, Pb3O4·H2O, which can be turned into the anhydrous form by gentle heating:
- K2PbO3 + 2 Pb(OCOCH3)2 + H2O → Pb3O4 + 2 KOCOCH3 + 2 CH3COOH
Reactions
Red lead is virtually insoluble in water and in alcohol. However, it is soluble in hydrochloric acidHydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
present in the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
, and is therefore toxic when ingested. It also dissolves in glacial acetic acid and a diluted mixture of nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
and hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
.
When heated to 500 °C, it decomposes to lead(II) oxide and oxygen. At 580 °C, the reaction is complete.
- 2 Pb3O4 → 6 PbO + O2
Nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
dissolves the lead tetroxide component, leaving behind the insoluble lead(IV) oxide:
- Pb3O4 + 4 HNO3 → PbO2 + 2 Pb(NO3)2 + 2 H2O
With iron oxides and with elemental iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, lead tetroxide forms insoluble iron(II) and iron(III) plumbate
Plumbate
In chemistry, a plumbate is a salt having one of the several lead-containing oxoanions. Although the term plumbate can refer either to plumbate or plumbate, it traditionally refers specifically to plumbate, whereas plumbate is referred to as plumbite.Plumbates are formed by the reaction of lead...
s, which is the basis of the anti-corrosive
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
properties of lead-based paints applied to iron objects.
Use
Lead tetraoxide is most often used as a pigmentPigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
for primer
Primer (paint)
A primer is a preparatory coating put on materials before painting. Priming ensures better adhesion of paint to the surface, increases paint durability, and provides additional protection for the material being painted.-When primers are used:...
paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
s for iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
objects. Due to its toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
, its use is being limited. In the past, it was used in combination with linseed oil
Linseed oil
Linseed oil, also known as flaxseed oil, is a clear to yellowish oil obtained from the dried ripe seeds of the flax plant . The oil is obtained by cold pressing, sometimes followed by solvent extraction...
as a thick, long-lasting anti-corrosive paint. The combination of minium and linen fibres was also used for plumbing
Plumbing
Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...
, now replaced with PTFE tape. Currently it is mostly used for manufacture of glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
, especially lead glass
Lead glass
Lead glass is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40 weight% lead oxide , while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO...
. It finds limited use in some amateur pyrotechnics
Pyrotechnics
Pyrotechnics is the science of using materials capable of undergoing self-contained and self-sustained exothermic chemical reactions for the production of heat, light, gas, smoke and/or sound...
as a relatively potent oxidizer.
Red lead was also used for engineer's scraping
Hand scraper
A hand scraper is a single-edged tool used to scrape metal from a surface. This may be required where a surface needs to be trued, corrected for fit to a mating part, needs to retain oil , or even to give a decorative finish.Surface plates were traditionally made by scraping...
, before being supplanted by Engineer's blue
Engineer's blue
Engineer's blue is a highly pigmented paste used to assist in the mating of two or more components.Joseph Whitworth popularized the first practical method of making accurate flat surfaces, during the 1830s, by using engineer's blue and scraping techniques on three trial surfaces...
. In traditional Chinese medicine
Traditional Chinese medicine
Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...
, red lead is used to treat ringworms and ulceration
Ulceration
Ulceration may refer to:-In medicine:*Ulcer , a discontinuity of the skin or a break in the skin that stops it from continuing its normal functions*Corneal ulcer, an inflammatory or infective condition of the cornea...
s, though the practice is limited due to its toxicity.
Physiological effects
When inhaled, lead tetroxide 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 acidGastric acid
Gastric acid is a digestive fluid, formed in the stomach. It has a pH of 1 to 2 and is composed of hydrochloric acid , and large quantities of potassium chloride and sodium chloride...
and absorbed, leading to lead poisoning. 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 tetroxide 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
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
, and also a grayish facial hue.
Lead tetroxide was shown to be carcinogenic for laboratory animals. Its carcinogenicity for humans was not proven.
History
Lead tetroxide was used as a red pigment in ancient RomeAncient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
, where it was prepared by calcination
Calcination
Calcination is a thermal treatment process applied to ores and other solid materials to bring about a thermal decomposition, phase transition, or removal of a volatile fraction. The calcination process normally takes place at temperatures below the melting point of the product materials...
of white lead
White lead
White lead is the chemical compound 2·Pb2. It was formerly used as an ingredient for lead paint and a cosmetic called Venetian Ceruse, because its opaque quality made it a good pigment. However, it tended to cause lead poisoning, and its use has been banned in most countries.White lead has been...
. In the ancient and medieval periods it was used as a pigment in the production of illuminated manuscript
Illuminated manuscript
An illuminated manuscript is a manuscript in which the text is supplemented by the addition of decoration, such as decorated initials, borders and miniature illustrations...
s, and gave its name to the minium or miniature
Miniature (illuminated manuscript)
The word miniature, derived from the Latin minium, red lead, is a picture in an ancient or medieval illuminated manuscript; the simple decoration of the early codices having been miniated or delineated with that pigment...
, a style of picture painted with the colour. As a finely divided powder, it was also sprinkled on dielectric
Dielectric
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...
surfaces to study Lichtenberg figures.