Lithopone
An artificial, non-toxic white pigment made from barium sulfate and zinc sulfide is called Lithopone . The mixture is produced in a special manufacturing process from barite (BaSO 4 ) and sphalerite (ZnS) or wurtzite (β-ZnS). Lithopone is listed in the Color Index as CI Pigment White 5.
Manufacturing
The barium sulfate barite is first converted into barium sulfide in a carbothermal process . The zinc sulfides sphalerite and wurtzite are converted into zinc oxide by roasting and converted into zinc sulfate with sulfuric acid . The chemical reaction of zinc sulfate and barium sulfide in an aqueous medium then creates the required lithopone mixture as a precipitate of barium sulfate and zinc sulfide:
Alternatively, metallic zinc or another zinc compound soluble in sulfuric acid can also be used as the zinc supplier .
Product types
Different types of lithopone are distinguished depending on the zinc sulfide content. As the zinc sulfide content rises (10% for yellow seals to 60% for silver seals), its brightness also increases. Whereby 30% occurs with red seals and 40% with green seals. It can also contain up to 2% zinc oxide (ZnO). Lithopone was discovered in the first half of the 18th century. It was first made by De Douhet in 1853 . The process was patented in 1850 . In 1871/1874 the first isolated evidence of the use of lithopone was found. It is still used today in primers and paints as well as in fillers . It can also be found in pastels , oil paints and plastic dispersions . It is lightfast and can be combined with other pigments and binders .
Lithopone is also called Charltonweiß, Chinese permanent white , opaque white referred Email White Sulfur Zinc sulfide or white.
literature
- Michael A. Götzinger: Colors of the earth in cultural epochs and ecological trends . In: Writings Association for the Spread of Scientific Knowledge . tape 151–152 , 2013, pp. 69–78 ( online on ZOBODAT [PDF; 3.6 MB ; accessed on November 8, 2018] Baryte and sphalerite as a component of Lithopone see p. 72).
- Helmut Schrätze , Karl-Ludwig Weiner : Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 153, 579 .
Web links
- Lithopone. In: kremerpigmente.de. Kremer Pigmente, November 9, 2012, accessed November 8, 2018 .
- Walter F. Meister: Lithopone and method of manufacture (Patent 1,455,963). In: patentimages.storage.googleapis.com. United States Patent Office, May 22, 1923, Retrieved July 24, 2019 .