White lead

from Wikipedia, the free encyclopedia
Structural formula
2 Lead ion Carbonation · Lead ion 2 Hydroxide ion
General
Surname White lead
other names
  • Basic lead carbonate
  • Cerussa
  • Kremserweiß
  • Hydrocerussite
  • Plumbum hydrocarbonicum
  • Tri-bicarbonate dihydroxide
  • CI Pigment White 1
  • CI 77597
Molecular formula (PbCO 3 ) 2 • Pb (OH) 2
Brief description

white odorless powder

External identifiers / databases
CAS number 1319-46-6
EC number 215-290-6
ECHA InfoCard 100.013.901
PubChem 14834
ChemSpider 14148
Wikidata Q656004
properties
Molar mass 775.63 g mol −1
Physical state

firmly

density

6.14 g cm −3

Melting point

Decomposition from 400 ° C

solubility

almost insoluble in water

safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
08 - Dangerous to health 07 - Warning 09 - Dangerous for the environment

danger

H and P phrases H: 302 + 332-360Df-373-410
P: 201-260-280-301 + 312 + 330-308 + 313
Authorization procedure under REACH

of particular concern : toxic for reproduction ( CMR )

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

White lead , 2 PbCO 3  ·  Pb (OH) 2 , also called lead hydroxide carbonate , is a basic lead carbonate and has been an important white pigment since ancient times . The German word (from Middle High German blīwīz ) is synonymous with Latin Cerussa .

properties

White lead is lightfast, has a very high opacity and, depending on the binding agent, has a beautiful sheen . It is poisonous due to the lead ions it contains and it darkens due to the formation of deep black lead sulfide . It is particularly susceptible to this in aqueous binders, for example in watercolors . Hydrogen sulfide is omnipresent in traces in the air and ages the pigment over a long period of time. For the same reason, it is unsuitable for sulfur-containing binders and sulfur-containing colored pigments such as ultramarine , cinnabar , auripigment .

The toxicity of white lead was already known in ancient times. This originally "only" white became less important when the pigment properties of zinc white were recognized in France from the middle of the 19th century . Barite white has been used as a white pigment since the beginning of the 20th century . But it is completely unsuitable for oil painting because its optical density (scattering power) is too close to that of the oil. Titanium white has been produced in large quantities worldwide since the 1960s . In the paint and plastics industry, white lead is no longer important. Compared to white lead artist paints, titanium white has significant disadvantages with its chemical and physical properties.

Advantages and disadvantages compared to other white pigments

  • White lead dries very quickly as lead compounds catalyze the hardening of drying oils. Titanium white dries more slowly, depending on the binder.
  • It may turn gray and black over time. This process is reversible to a limited extent.

  • Discoloration on paper coated with white lead, late 19th century

  • White lead can be mixed perfectly with transparent and opaque pigments. The remission of white lead already drops in the visible (blue) range; it has a yellow tinge. Titanium white remits almost completely into the ultraviolet range, so it appears cold. Color mixtures with titanium white also result in cold tones.
  • Because of its crystal structure, white lead is a soft pigment. Titanium white, on the other hand, is a hard pigment ( Mohs hardness 6) (also depending on the crystal structure: rutile or anatase ); it can also scratch hardened steel when dry. This means that white lead can be rubbed out more easily and reworked into finer grain sizes. Titanium dioxide pigments usually have a surface functionalization tailored to the binding system. The primary particle size is 220 nm to 300 nm, so that a simple dispersion is usually sufficient to achieve good hiding power .
  • Pure TiO 2 , especially anatase pigment, shows a photocatalytic effect when exposed to UV . This leads to faster chalking . Modern titanium dioxide pigments have a surface finish that almost completely suppresses this effect.
  • Zinc white (ZnO) can be a substitute for white lead. In oil paints, zinc white covers less than lead white;
  • Barite white is unsuitable for oil paintings because, in contrast to lead white and zinc white, the refractive index of barite white differs only slightly from oil.
  • Zinc sulfide (ZnS) has a green tinge and is not suitable as an oil paint.
  • Chalk white (soft white limestone) has a refractive index very close to that of binders, which is why chalk is used as transparent white.

Manufacturing

White lead on lead roll

White lead is a man-made pigment. As a rare mineral , it is known as hydrocerussite (a lead hydroxycarbonate).

In the ancient and medieval writings the production is described as follows: Lead plates or pieces of lead are placed in a vessel together with a bowl of vinegar and then buried under a dung heap . The lead is thus exposed to vinegar fumes and carbon dioxide and is kept at a constant temperature by the putrefaction processes in the manure. After a few weeks, a white substance, white lead, forms on the lead plates (in addition to basic lead acetate with the help of oxygen from the air and neutral lead acetate).

In other historical processes, metallic lead is also exposed to the effects of vinegar fumes and carbon dioxide. One example is the Dutch Loogen method . The Loogen are oxidation rooms in which up to ten tons of lead plates, packed in stoneware pots, which are surrounded by horse manure and tan, are exposed to heat, acetic acid and air for about four weeks. The white lead was slurried from the pots, dried and ground. In the Klagenfurt process, wine pomace, brewer's yeast or fermentable fruit juices take the place of vinegar. This production method is slower, but should result in a pure white and particularly fluffy product. This is how the first so-called Kremserweiß was produced. In 1839 Gustav Dietel practiced the German chamber procedure for the first time in Eisenach. A millimeter thick, long lead rags are hung on wooden frames in large brick rooms and exposed to an atmosphere of air, carbon dioxide, water and vinegar vapors in certain doses. The lead is first chemically converted into basic acetic acid lead and then later into basic lead carbonate. The white lead sludge is then washed, sieved, dried and ground.

Today white lead is produced in a precipitation process in which a Pb (II) salt solution is converted with CO 3 2− in the heat . The procedures can be read in Meyers (first web link).

use

Hortus sanitatis , Mainz 1491. Fig. For the chapter Cerusa - lead white
Sticker of a paint can from the 1980s with a warning against white lead

White lead was already used as a coloring agent in antiquity and was already used in its function by Theophrastus in the 4th century BC. Mentioned. Gaius Plinius Secundus (23–79 AD) also mentions this pigment. It also appears in the medieval recipe collections of the Lucca manuscript , the little changed Mappae Clavicula , in Theophilus 'and Heraclius ' writings, in which metallic lead and vinegar were used as the starting material for the production of white lead.

From antiquity to the 19th century, white lead was used as a white pigment in make-up . By the 12th century at the latest ( Circa instans ) it was known that the use of white lead as a make-up product over a long period of time caused health problems (toothache, mouth rot and bad breath).

Internal medical use of white lead has never been recommended. In wax ointments, plasters and as recommended white lead ointment ( unguentum de cerussa ) or substance - for example by Avicenna and also German-speaking authors of the Middle Ages - it has been prescribed since antiquity (Dioscurides, Pliny) for wound treatment, against stool and anal fissures. External use was not abandoned until the 1950s.

For paints it was used preferentially in the oil technique, until about 1835 almost exclusively for white tones. It was also used in watercolors and pastels , occasionally even in wall painting . Today, the use of white lead is banned due to its toxicity, it can only be used for restoration purposes and is therefore only sold under strict conditions.

White lead came on the market under different names, some of which differed in quality. The main reason for this is the composition; it was often stretched with (low-covering) barite white .

White lead has been sold under various names.

  • Kremser Weiß, from Krems
  • Dutch white
  • Venetian White, from Venice
  • Hamburger Weiß, to Hamburg
  • Kremnitzer White, from Kremnitz
  • Slate white
  • Pearl white, snow white, silver white
  • (commonly called) opaque white .

White lead was used in primer paints for wood and in primer and corrosion protection paints for metals until the late 20th century. However, it must be differentiated from red lead , which is also poisonous and is formed when white lead is glowed and was a typical component of corrosion protection paint for iron and could also be spread on rusted parts.

hazards

history

  • It has been known since ancient times that white lead - administered orally - is deadly (Dioscurides, Pliny).
  • In the 12th century ( Circa instans ) it was observed that people who produce white lead frequently suffer from paralysis, strokes ("apoplexia"), epilepsy and joint diseases ("arthetica").
  • It was also known in the 12th century ( Circa instans ) that the continued use of white lead as a make-up agent leads to tooth decay and bad breath.

Current state of knowledge

  • White lead is very hazardous to water, even if it has only a low solubility.
  • Paints containing white lead pose a risk of lead poisoning in all stages of use, i.e. in the manufacture, processing and recycling of parts painted with it. Aerosols and abrasion that can get into the lungs through the air are dangerous.
  • Another danger arises when objects painted with white lead are burned (for example old window frames); almost all of the lead oxide produced ends up in the smoke gases.

Proof of counterfeit paintings

The use of white lead can be proven by an examination with X-rays, as white lead absorbs it very strongly.

The origin of the lead can be determined by examining the isotopic composition : while the white lead used by painters of the Dutch paintings of the 17th century (e.g. Jan Vermeer ) was obtained from lead deposits in European low mountain ranges, the white lead came from southern Germany 17th century paintings were used, from lead deposits in the European Alps. Lead ores have been imported from America and Australia since the 19th century.

White lead produced today differs from old white lead in the content of trace elements: Old Dutch white lead is characterized by high levels of silver and antimony (see R. Strauss), while today's white lead, which was used by the Vermeer forger Han van Meegeren , neither silver nor Contains copper. These elements are separated in advance in the smelting of lead today

Counterfeits, for which lead compounds produced today were used as lead pigments, can be detected with the help of the lead-210 method. The lead isotope belongs to the uranium-238 decay series, it arises from radium-226, which decays with a half-life of 22 years. This short half-life can be used to identify recent counterfeits.

The values ​​in the picture "Christ and the Disciples in Emmaus" by Vermeer forger Han van Meegeren (Polonium-210: 8.5 ± 1.4, Radium-226: 0.8 ± 0.3) did not correspond to the values ​​in the paintings of the Dutch of the comparable years 1600 ... 1660 (Polonium-210: 0.23 ± 0.27, Radium-226: 0.40 ± 0.47).

Literature - sources

White lead as a white pigment

  • Kirsten Meyer: Coated luxury paper of the 19th century and its preservation. In: Konrad Vanja et al. (Ed.): Working group image, print, paper. Conference proceedings Berlin 2012. (= Working Group Image, Print, Paper. Volume 17). Waxmann, Münster a. a. 2013, ISBN 978-3-8309-2905-5 . (also master thesis HAWK Hildesheim and others )
  • Forgery and research. Museum Folkwang et al., Essen et al. 1976, pp. 191 and 195 f., (2nd edition. Ibid. 1979, ISBN 3-7759-0201-5 ; exhibition catalog Essen and Berlin).
  • Bernard Keisch, Robert L. Feller, Allen S. Levine, Raymond R. Edwards: Dating and Authenticating Works of Art by Measurement of Natural Alpha Emitters. In: Science . Volume 155, No. 3767, 1967, pp. 1238-1242, doi: 10.1126 / science.155.3767.1238 .
  • H. Kühn: Lead white and its use in painting I. and II. In: Color and lacquer. Volume 73, 1967, pp. 99-105 and 209-213.
  • M. Rohner: lead white. A white pigment with light and dark sides. In: C. Cattaneo, S. Muntwyler, M. Rigert, HP Schneider (eds.): Color pigments, dyes, color stories. 2nd, revised edition. Alata Verlag, Winterthur 2011, ISBN 978-3-033-02968-2 , pp. 186–191.

White lead (Cerussa) in cosmetics and medicine

Web links

Individual evidence

  1. ^ The Color of Art Pigment Database: Pigment White artiscreation.com , David Myers. Retrieved July 23, 2016.
  2. ↑ a b c d e f Entry on white lead in the GESTIS substance database of the IFA , accessed on January 8, 2020(JavaScript required) .
  3. ↑ 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 specified elsewhere in this Annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA) , accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
  4. ↑ Entry in the SVHC list of the European Chemicals Agency , accessed on October 19, 2015.
  5. ^ Vitruvius: De architectura VI. 10
  6. ↑ Temple C. Patton (Ed.): Pigment Handbook. Wiley, New York NY 1973.
  7. ↑ Kirsten Meyer: Coated luxury paper of the 19th century and its preservation. 2013.
  8. ↑ In the picture the toad represents the poisonous white lead used for cosmetics. In the text (in the German translation) it is noted: “... a lot of women ... make pillules and make them face. ... but Merck who breaks the blyweiß for a long time / dem thunt die zeen wee vnd fulen im / darumb so stincket in the mouth. ” The Hortus sanitatis had taken this text - slightly varied - from the circa instans of the 12th century.
  9. ^ Herrmann Klenke: Cosmetics; or, Human beautification based on rational health theory: a folk script. Kummer, Leipzig 1869, p. 274.
  10. ↑ Wolfgang Wegner: Krummessen, Hinrik. In: Werner E. Gerabek , Bernhard D. Haage, Gundolf Keil , Wolfgang Wegner (eds.): Enzyklopädie Medizingeschichte. de Gruyter, Berlin / New York 2005, ISBN 3-11-015714-4 , p. 811 f.
  11. ↑ Knud. O. Møller: Pharmacology. 2nd Edition. Schwabe, Basel 1953, p. 705: "... Because of their toxicity, lead compounds should not be used for therapeutic purposes, not even for external use."
  12. ↑ See page of a pigment shop with corresponding information: kremer-pigmente.com
  13. ↑ Counterfeiting and Research. 1976, pp. 195-196.
  14. ↑ Description of the 210 Pb method ( Memento from September 20, 2011 in the Internet Archive )
  15. ^ Bernard Keisch: Discriminating Radioactivity Measurements of Lead: New Tool for Authentication. In: Curator. The Museum Journal. Volume 11, No. 1, 1968, pp. 41-52, doi: 10.1111 / j.2151-6952.1968.tb00884.x .
  16. ↑ Counterfeiting and Research. 1976, p. 191.
  17. ↑ Christ and the disciples at Emmaus.
  18. ^ B. Keisch et al .: Dating and Authenticating Works of Art by Measurement of Natural Alpha Emitters. In: Science. Volume 155, No. 3767, 1967, pp. 1238-1242.