Sulphate and chloride methods

There are numerous manufacturers of titanium dioxide; the largest include Delaware-based Chemours (a spin-off of DuPont Chemical), Texas-based Kronos, and China-based Lomon Billions Group, all of which manufacture pigments for use in products like paints, coatings, and plastics. UK-based Venator is a major supplier of titanium dioxide used in food and cosmetics, along with paints, paper, plastic, and more. As a pigment, it is called Pigment White 6 (PW6), titanium white, or CI 77891. As a food additive, it is known as E171.

Calcium carbonate is a naturally occurring mineral that is found in rocks and minerals such as calcite, aragonite, and limestone. It is commonly used in industries such as paint, paper, plastics, and rubber as a filler and pigment. The manufacturing process of calcium carbonate involves extracting the mineral from quarries or mines, crushing and grinding it into a fine powder, and then purifying it through various chemical processes.

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In a study published in the journal Toxicology, researchers examined the effects of exposing human colon cancer cell line (HTC116) titanium dioxide food additives in vitro. “In the absence of cytotoxicity, E171 was accumulated in the cells after 24 hours of exposure, increasing granularity and reactive oxygen species, inducing alterations in the molecular pattern of nucleic acids and lipids, and causing nuclei enlargement, DNA damage and tubulin depolymerization,” the scientists wrote. Researchers removed the additive from the culture, then examined the results 48 hours later. They found, “The removal of E171 was unable to revert the alterations found after 24 h of exposure in colon cells. In conclusion, exposure to E171 causes alterations that cannot be reverted after 48 h if E171 is removed from colon cells.”

Having thus described the origin and uses of the pigment, we now come to the question, what is lithopone? It is, in short, a chemical compound usually consisting of 30.5 per cent zinc sulphide, 1.5 per cent zinc oxide and 68 per cent barium sulphate, but these proportions vary slightly in the different makes. Lithopone of this composition is sold as the highest grade, either as red seal or green seal, as it best suits the idea of the manufacturer. Many manufacturers, especially in Europe, sell and also export other brands under other seals, containing 24, 20, 18 and as little as 12 per cent of zinc sulphide with very small percentages of zinc oxide, the balance being usually barium sulphate, but sometimes certain portions of China clay or gypsum (calcium sulphate) or whiting (calcium carbonate). Such brands are not a chemical compound, but mechanical mixtures of the chemically compounded lithopone and the admixtures referred to.