BaSO4 + 4C=BaS + 4CO

This article discusses the discovery of phosphorescent lithopone on watercolor drawings by American artist John La Farge dated between 1890 and 1905 and the history of lithopone in the pigment industry in the late 19th and early 20th centuries. Despite having many desirable qualities for use in white watercolor or oil paints, the development of lithopone as an artists’ pigment was hampered by its tendency to darken in sunlight. Its availability to, and adoption by, artists remain unclear, as colormen's trade catalogs were generally not explicit in describing white pigments as containing lithopone. Further, lithopone may be mistaken for lead white during visual examination and its short-lived phosphorescence can be easily missed by the uninformed observer. Phosphorescent lithopone has been documented on only one other work-to-date: a watercolor by Van Gogh. In addition to the history of lithopone's manufacture, the article details the mechanism for its phosphorescence and its identification aided by Raman spectroscopy and spectrofluorimetry.

Price Dynamics. The Titanium Dioxide price in United States decreased during December 2018 to 2,770 USD per metric ton, which represents a decline of 7% compared to the previous month’s value. On a year-over-year basis, Titanium Dioxide prices in United States remained constant . Meanwhile, in Germany, the average price of Titanium Dioxide amounted to 3,720 USD per metric ton, from 3,460 USD per metric ton one year earlier. On a month-over-month basis, the Titanium Dioxide price in Germany is 11% higher than the price one month before.