Lithopone B-301 CAS 1345-05-7

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Model: MOS1345-05-7
Brand Name: MOSINTER
CAS No.: 1345-05-7
Molecular formula: BaO5S2Zn2
Molecular weight: 412.23
Appearance: White powder
Soluble: Insoluble
Odorless: odorless
Density: Approx. 4.3 g/mL
Molar mass: 330.80 g/mol

Lithopone  B-301 (CAS: 1345-05-7)

 

Item Index
Total Zinc Calculated use Zinc Sulfate and Barium Sulfate, % 99 min
Zinc Sulphide, % 28 -30
Zinc Oxide, % 0.6 max
Volatile at 105℃, % 0.3 max
Water soluble matter, % 0.4 max
Sieve Residue,63um 0.1 max
Oil absorption, g/100g 14 max
Color, compared with the standard sample Close  to standard
PH value of aqueous suspension 6.0-8.0
Tint reducing power Not less than
Hiding power Not less than of 5% the standard sample

Lithopone, C.I. Pigment White 5, is an mixture of inorganic compounds, is a widely used as a white pigment powder. It is composed of a mixture ofbarium sulfate and zinc sulfide. These insoluble compounds blend well with organic compounds and confer opacity. It was made popular by the cheap production costs, greater coverage. Related white pigments include titanium dioxide, zinc oxide (“zinc white”), and zinc sulfide.

History

Lithipone was discovered in 1870s by DuPont. It was manufactured by Krebs Pigments and Chemical Company and other companies. The material came in different “seals”, which varied in the content of zinc sulfide. Gold seal and Bronze seals contain 40-50% zinc sulfide, offering more hiding power and strength. Although its popularity peaked around 1920, approximately 220,000 tons were produced in 1990. It is mainly used in paints, putty, and in plastics.

Stability and darkening

Although barium sulfate is almost completely inert, zinc sulfide degrades upon exposure to UV light, leading to darkening of the pigment. The severity of this UV reaction is dependent on a combination of two factors; how much zinc sulfide makes up the pigments formulation, and its total accumulated UV exposure. Depending on these factors the pigment itself can vary in shade over time, ranging from pure white all the way to grey or even black. To suppress this effect, a dopant may be used, such as a small amount of cobalt salts, which would be added to the formulation. This process creates cobalt-doped zinc sulfide. The cobalt salts help to stabilize zinc sulfide so it will not have as severe a reaction to UV exposure.

Production

Lithopone is produced by coprecipitation of barium sulfate and zinc sulfide. Most commonly coprecipitation is effected by combining equimolar amounts of zinc sulfate and barium sulfide:

BaS + ZnSO4→ ZnS • BaSO4

This route affords a product that is 29.4 wt % ZnS and 70.6 wt % BaSO4. Variations exist, for example, more ZnS-rich materials are produced when zinc chloride is added to the mixture of zinc sulfate and barium sulfide.

Barium sulfide is produced by carbothermic reduction of barium sulfate. Zinc sulfate is obtained from a variety of zinc products, often waste, by treatment with sulfuric acid.

Safety

Lithopone is not highly poisonous, reflecting the insolubility of the components. Barium sulfate is used widely in medicine as a radiocontrast agent. Lithopne is allowed to be in contact with foodstuffs in theUSand Europe.

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