Lead (II, IV) oxide
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| General | ||||||||||||||||
| Surname | Lead (II, IV) oxide | |||||||||||||||
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| Molecular formula | Pb 3 O 4 | |||||||||||||||
| Brief description |
red powder |
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| properties | ||||||||||||||||
| Molar mass | 685.57 g mol −1 | |||||||||||||||
| Physical state |
firmly |
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| density |
9.53 g cm −3 |
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| Melting point |
500 ° C |
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| solubility |
practically insoluble in water |
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| safety instructions | ||||||||||||||||
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| Authorization procedure under REACH |
of particular concern : toxic for reproduction ( CMR ) |
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| MAK |
No MAK value is generally assigned for carcinogenic substances |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||
Lead (II, IV) oxide , and red lead , red lead or lead (II) -orthoplumbat is a bright red powder having the empirical formula Pb 3 O 4 . As a pigment , it is also known as the Paris red , red lead , gold satin upper , gold cinnabar , Kristallmennige , Mineral Orange , Sandix , Saturnmennige and Saturnrot referred.
history
Red lead was already mixed by the Romans as a coloring substance under the sand in the circus in order to make the bloody traces of the fighting there invisible. During the triumphal procession , the face of the triumphant was colored red with red lead, a practice that was also used in statues of gods in ancient times. The color is reminiscent of statues of gods that were made from terracotta in "ancient times". It has also been used as a pigment in paints since ancient times . The use in illuminating - red lead is called minium in Latin - is said to have coined the term “miniature” via Italian minia ('small painting') and probably influenced by the Latin minor ('smaller') .
Red lead can be produced by targeted oxidation (“glowing”) of white lead or lead yellow at 480 ° C. The first factory production finally took place in Venice in the 16th century. The first industrial production in Germany took place in 1687 near Hanover . The term “ red lead ” is derived from the Latin minium , “ vermilion ”; the word went over to the Old High German minio and Middle High German minig (in manuscripts also minie and menie ) in "Mennige".
Occurrence
Lead (II, IV) oxide is in the form of rare in nature Minerals Minium before.
properties
It is not a mixture of lead (II) oxide and lead (IV) oxide , but a combination of these, whereby the lead in the + IV oxidation state with the oxygen atoms forms a kind of anion , the plumbate ion ( PbO 4 4− ), is complexed. The crystal structure contains strands of edge- sharing Pb IV O 6 octahedra, while the Pb II ions are surrounded by four coordinating oxygen atoms and the lone pair of electrons (at the top of the pyramid). Chemically, the plumbate is similar to the silicate ion SiO 4 4− and the stannate ion SnO 4 4− ( silicon and tin are in the same main group as lead and therefore have periodic similarities). If red lead is dissolved in nitric acid , lead (II) nitrate and lead (IV) oxide are formed as dehydration products of the intermediate orthoble (IV) acid H 4 PbO 4 . The compound is precisely called lead (II) orthoplumbate Pb 2 [PbO 4 ], the divalent lead occurs in it as a cation .
Mennige owes its bright orange color to charge-transfer transitions from oxygen and in particular 6s-lead (II) states to 6s / 6p-lead (IV) states.
use
pigment
Red lead is used as a pigment, where it is listed under various names. The name Paris Red is somewhat misleading, since it not only for red lead, but also for iron oxide (iron (III) oxide, also Eisenmennige called) is used. Gold satin differentiates it from the natural earth pigment satin brown .
Red lead can be mixed very well with binding agents, but is incompatible with sulfur-containing substances. As a pigment, it is unstable when exposed to light . Under certain circumstances the color will darken, with either plattnerite ( lead (IV) oxide ) or galena ( lead (II) sulfide ) forming. The pigment can, however, also lighten, forming anglesite ( lead (II) sulfate ) and cerussite ( lead (II) carbonate ). Plumbonacrit occurs as an intermediate stage of lightening .
Anti-rust paint
Red lead used to be used as a rust protection paint . Because of its known toxicity , red lead is used less and less in health-conscious countries. Since January 2005 the Chemicals Act in Switzerland has banned the use of red lead. Red lead has been banned in Germany as rust protection since 2012. For example, the characteristic red hue of the Golden Gate Bridge can be traced back to the original use of a red lead paint and is now replaced by acrylic paint. Red lead is still sometimes used in heating systems to coat the steel nipples between the cast boiler sections. This prevents oxidation between the steel and the less noble cast .
The pigment was rubbed with linseed oil and / or turpentine oil and spread. Later, to achieve a shorter drying time, volatile solvents were added, for example alcohols ( methanol , ethanol ) or benzines (paint thinner).
Medication plaster
In the past, red lead was also used for medicinal plasters , for so-called mother plasters or universal defensive plasters .
Crystal glass
Red lead is still used today to make crystal glasses, where it is mixed with quartz sand and potash and then melted.
Safety instructions and toxicology
When ingested orally, lead oxide was found to be moderately toxic to guinea pigs (LD Lo ~ 1 g · kg −1 ), but it produced twitching, reduced growth and changes in platelets . The intraperitoneal administration showed low toxicity (in mice LD 50 17.7 g · kg -1 ) in rats, a much higher 630 mg · kg -1 . In humans, red lead proved to be particularly dangerous when absorbed via the respiratory and digestive tracts as the finest particles with sizes of 0.1–1 μm , which are almost completely absorbed in the alveoli . In the digestive tract, poorly soluble lead compounds such as lead (II, IV) oxide can be absorbed up to a maximum of 15%. Symptoms and effects of poisoning are vomiting, constipation, colic of the intestines, damage to the blood and kidneys, a drop in body temperature and blood pressure and even circulatory collapse. Chronic intoxication of small amounts often shows unspecific symptoms such as mild headache and dizziness, sleep disorders, pain in muscles and limbs with paresthesia and loss of appetite. Lead compounds have a predominantly toxic effect on the blood , muscles and the central nervous system . In humans, the impairment of reproductive capacity as well as abortions in pregnant women and damage to the nervous system of embryos through inorganic lead compounds have been reliably proven.
Red lead is rarely used today as a rust protection agent, but many older building structures (e.g. bridges or roof trusses) or steel or iron objects outdoors (e.g. fences, grids, lanterns, etc.) still have layers of protective paint containing lead available. If such coatings are removed mechanically (e.g. by sandblasting ), appropriate protective measures are necessary.
Web links
Individual evidence
- ↑ a b c d data sheet lead (II, IV) oxide from AlfaAesar, accessed on December 15, 2010 ( PDF )(JavaScript required) .
- ↑ a b c d Entry on lead (II, IV) oxide in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
- ↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the specified labeling it falls under the group entry lead compounds with the exception of those named in this annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on December 14, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
- ↑ Entry in the SVHC list of the European Chemicals Agency , accessed on July 17, 2014.
- ↑ a b Archives for Hygiene and Bacteriology . Vol. 125, p. 273, 1941.
- ↑ a b c Entry on lead (II, IV) oxide in the ChemIDplus database of the United States National Library of Medicine (NLM) .
- ↑ a b Gigiena Truda i Professional'nye Zabolevaniya. ( Labor Hygiene and Occupational Diseases. Vol. ) 26 (8), p. 51, 1982.
- ↑ a b Gigiena Truda i Professional'nye Zabolevaniya. ( Labor Hygiene and Occupational Diseases. ) Vol. 19 (3), p. 30, 1975.
- ↑ Jochen Bleicken: Augustus, A Biography . Berlin 1998, ISBN 3-8286-0027-1 , p. 30 .
- ^ Friedrich Kluge , Alfred Götze : Etymological dictionary of the German language . 20th ed., Ed. by Walther Mitzka , De Gruyter, Berlin / New York 1967; Reprint (“21st unchanged edition”) ibid 1975, ISBN 3-11-005709-3 , p. 480.
- ↑ Boris Paraškevov: Words and names of the same origin and structure: Lexicon of etymological duplicates in German . Walter de Gruyter, 2004, ISBN 3-11-017469-3 , p. 217 ( limited preview in Google Book search).
- ↑ JR Gavarri, D. Weigel, Oxydes de plomb. I. structure crystalline du minium Pb 3 O 4 , a temperature ambiante (293 K), Journal of Solid State Chemistry 13 (1975) 252-257.
- ^ HJ Terpstra, RA de Groot, C. Haas, J. Phys. Chem. Solids 58 (1997) 561-566.
- ↑ F. Vanmeert, G. van der Snickt, K. Janssens : Plumbonacrite Identified by X-ray Powder Diffraction Tomography as a missing link during degradation of Red Lead in a Van Gogh painting . In: Angewandte Chemie . tape 127 , no. 12 , 2015, p. 3678-3681 , doi : 10.1002 / anie.201411691 .
- ↑ Lead plaster in Meyer's Large Conversation Lexicon (1905).