1,3-dimethyl-6-chlorouracil

THE OBSCURE HISTORY OF A UBIQUITOUS PIGMENT: PHOSPHORESCENT LITHOPONE AND ITS APPEARANCE ON DRAWINGS BY JOHN LA FARGE

As early as sixty years ago, zinc sulphide was first thought of as a pigment for coloring India rubber and a patent for the process of its manufacture was issued in England. But it was not until twenty years later that zinc sulphide and its manufacture was seriously considered as a pigment for paint, and in 1874 a patent was issued for a process of manufacturing a white pigment, composed of zinc sulphide and barium sulphate, known as Charlton white, also as Orr's white enamel. This was followed in 1876 by a patent issued to a manufacturer named Griffith and the product, which was similar in character to Charlton white, was known as Griffith's patent zinc white. In 1879 another patent for a more novel process was obtained by Griffith & Cawley, the product made under this process proving the best of the series placed upon the market up to that date. After that time many new processes were patented, all, however, tending to the same object, that of producing a white pigment, composed of zinc sulphide and barium carbonate, the results, however, in many cases ending with failure.

Resumo–Este artigo discute a descoberta de litopônio fosforescente em desenhos de aquarela do artista americano John La Farge datados de entre 1890 e 1905 e a história do litopônio na indústria de pigmento no final do século XIX e início do século XX. Apesar de ter muitas qualidades desejáveis para o uso em aquarela branca ou tintas a óleo, o desenvolvimento do litopônio como um pigmento de artistas foi prejudicado por sua tendência a se escurecer na luz solar. Sua disponibilidade para e uso por parte de artistas ainda não está clara, uma vez que os catálogos comerciais dos vendedores de tintas geralmente não eram explícitos na descrição de pigmentos brancos como algo que contém litopônio. Além disso, o litopônio pode ser confundido com o branco de chumbo durante o exame visual e sua fosforescência de curta duração pode ser facilmente perdida pelo observador desinformado. O litopônio fosforescente foi documentado em apenas um outro trabalho até hoje: uma aquarela de Van Gogh. Além da história da manufatura do litopônio, o artigo detalha o mecanismo para a sua fosforescência e sua identificação auxiliada pela espectroscopia de Raman e espectrofluorimetria.

For research published in Archives of Toxicology in 2020, scientists fed one group of mice a solution containing titanium dioxide for one month, and compared it to those that did not receive the additive. They found “the richness and evenness of gut microbiota were remarkably decreased and the gut microbial community compositions were significantly changed” in the titanium dioxide group when compared with the control group. The tests also revealed that the titanium dioxide exposure could cause locomotor dysfunction, or mobility issues “by elevating the excitement of enteric neurons, which might spread to the brain via gut-brain communication by vagal pathway.” The researchers concluded: “These findings provide valuable insights into the novel mechanism of TiO2NP-induced neurotoxicity. Understanding the microbiota-gut-brain axis will provide the foundation for potential therapeutic or prevention approaches against TiO2NP-induced gut and brain-related disorders.”

Faber argued there hasn't been enough change in these federal regulations in the decades following the FDA's approval of titanium dioxide – especially as others increasingly point to potential health consequences.

Fig. 3. Cell survival measured on samples of MSSA with bare and functionalized P25TiO₂NPs after 6 h of irradiation. A: P25TiO₂NPs, B:vitaminB2@P25TiO₂NPs, C: vitaminC@P25TiO₂NPs in concentrations of 0.2 μg/mL (red) and 0.2 mg/mL (blue). p <0.05.

Production of TiO₂ Pigment

Titanium dioxide comes in the form of a white powder and is sometimes used in cosmetics to adjust a color to a lighter shade. This is also why it can produce a white cast.