Lead(II,IV) oxide

• Minium
• Orange lead
• Minium
• Lead (II) orthoplumbat

Red powder

Fixed

9.53 g · cm -3

500 ° C

Practically insoluble in water

Risk

For carcinogenic substances no MAK value is generally assigned

Template: Infobox chemical / molecular formula search is not possible

Lead (II, IV ) oxide, and red lead or lead (II) - orthoplumbat is a bright red powder with the empirical formula Pb3O4. As a pigment it is also referred to as the Paris red, red lead, gold satin upper, gold vermilion, Kristallmennige, Mineral Orange, Sandix, Saturnmennige and saturnrot.

History

Minium was already mixed by the Romans as a coloring substance under the sand in the circus, to make the bloody traces of the people there are fighting invisible. In the face of the triumphal triumphant was colored red with red lead, a practice that took place in ancient times even with statues of gods use. Since ancient times, it is also used as a pigment in artists' paints. The use in the book painting - red lead is called in the Latin minium - should the term have shaped miniatures.

Minium can be generated by selective oxidation of lead white or yellow lead at 480 ° C. The first factory production was finally in Venice in the 16th century. The first industrial production in Germany was in 1687 near Hanover, later it was mainly produced in the Rhineland and Nuremberg - Erlenstegen. The term " red lead ", is derived from the Latin minium vermilion '; the word went through the Old High German and Middle High German Minio minig in " red lead " over.

Occurrence

Lead (II, IV ) oxide occurs in nature as the rare mineral Minium before.

Properties

It is not a mixture of lead (II ) oxide and lead ( IV) oxide, but a compound thereof, wherein the lead in the oxidation state IV with the oxygen atoms to a kind of anion, the plumbate ion ( PbO44 ) is complexed. In the process on the crystal structure strands against edge-sharing octahedra PbIVO6, while the ions are square pyramidal PbII surrounded by four coordinating oxygen atoms and the lone pair (on the top of the pyramid ). Chemically similar to the Plumbat the silicate ion SiO44 and the stannate ion SnO44 ( silicon and tin are in the same main group, such as lead and therefore have periodic similarities ). Solving red lead in nitric acid, then lead (II ) nitrate and lead ( IV) oxide form as a dehydration product of Ortho lead (IV ) acid H4PbO4 intermediacy. The connection thereto is precisely lead ( II) orthoplumbat Pb2 [ PbO4 ], the divalent lead occurs therein as cation.

Its bright orange color owes minium charge-transfer transitions of oxygen and in particular 6s lead (II) states in 6s/6p-Blei (IV ) states.

Use

Pigment

Red lead is used as a pigment, where it is listed under different names. The name Paris Red is somewhat misleading because it is not only used for red lead, but also for iron oxide (iron (III ) oxide, also called Eisenmennige ). Gold Satin Upper distinguishes it from against the natural earth pigment satin upper.

As the pigment, red lead is impermanent, because it transforms the light slowly brown to black lead (IV ) oxide ( PbO2 ). It is highly miscible with binders, but incompatible with sulfur-containing pigments.

Anti-rust paint

Red Lead is still used as antirust paint, because of its known toxicity, however, becoming increasingly rare. For this purpose, the pigment was previously rubbed with linseed oil and / or oil of turpentine and passed. Later they continued to attain a shorter drying time for volatile solvents, such as various alcohols (methanol, ethanol) or gasoline ( thinner ). Thus, the characteristic red color of the Golden Gate Bridge, for example, due to the initial use of a Mennigeanstrichs. Red lead rust protection is banned in Germany since 2012. Since January 2005, the Chemicals Act in Switzerland banning the use of red lead. In heating of red lead is still used in part to coat the steel nipples between the cast boiler sections with it. This prevents oxidation between the steel and the noble cast.

Medicated patch

Formerly red lead was also used for medicinal plasters, for so-called mother patch or Universal Defensive pavement.

Safety and Toxicology

When ingested, the lead oxide for guinea pigs was found to be moderately toxic ( LDLO ~ 1 g · kg -1), however, produced convulsions, decreased growth in size and changes in platelets. Intraperitoneal administration in mice, showed a low toxicity (LD50 17.7 g · kg -1) in rats of a much higher 630 mg · kg -1. In humans, red lead proved especially dangerous when absorbed through the respiratory tract and the digestive tract as very fine particles with sizes of 0.1-1 microns, which are almost completely absorbed in the alveoli. In the digestive tract and are sparingly soluble lead compounds such as lead (II, IV) oxide may be added to a maximum of 15 %. Poisoning symptoms and effects are vomiting, constipation, colic the intestines, damage to blood and kidneys, waste of body temperature and blood pressure to cardiovascular collapse. Chronic intoxication of small amounts often show non-specific symptoms such as slight headache and dizziness, insomnia, pain in muscles and limbs with paresthesia and loss of appetite. Lead compounds have here mainly toxic to the blood, the muscles and the central nervous system. In humans, the impairment of reproductive performance and abortion in pregnant women and damage to the nervous system of embryos have been proven safe by inorganic lead compounds.