Barium sulfide is the inorganic compound with the formula BaS. BaS is the barium compound produced on the largest scale.[3] It is an important precursor to other barium compounds including BaCO3 and the pigment lithopone, ZnS/BaSO4.[4] Like other chalcogenides of the alkaline earth metals, BaS is a short wavelength emitter for electronic displays.[5] It is colorless, although like many sulfides, it is commonly obtained in impure colored forms.
Discovery
BaS was prepared by the Italian alchemist Vincentius (or Vincentinus) Casciarolus (or Casciorolus, 1571–1624) via the thermo-chemical reduction of BaSO4 (available as the mineral barite).[6] It is currently manufactured by an improved version of Casciarolus's process using coke in place of flour and charcoal. This kind of conversion is called a carbothermic reaction:
BaSO4 + 2 C → BaS + 2 CO2
and also:
BaSO4 + 4 C → BaS + 4 CO
The basic method remains in use today. BaS dissolves in water. These aqueous solutions, when treated with sodium carbonate or carbon dioxide, give a white solid of barium carbonate, a source material for many commercial barium compounds.[7]
According to Harvey (1957),[8] in 1603, Vincenzo Cascariolo used barite, found at the bottom of Mount Paterno near Bologna, in one of his non-fruitful attempts to produce gold. After grinding and heating the mineral with charcoal under reducing conditions, he obtained a persistent luminescent material rapidly called Lapis Boloniensis, or Bolognian stone.[9][10] The phosphorescence of the material obtained by Casciarolo made it a curiosity.[11][12][13]
Preparation
A modern procedure proceeds from barium carbonate:[14]
BaCO3 + H2S → BaS + H2O + CO2
BaS crystallizes with the NaCl structure, featuring octahedral Ba2+ and S2− centres.
The observed melting point of barium sulfide is highly sensitive to impurities.[2]
Safety
BaS is quite poisonous, as are related sulfides, such as CaS, which evolve toxic hydrogen sulfide upon contact with water.
^Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN0-12-352651-5.
^Vij, D. R.; Singh, N. (1992). Optical and electrical properties of II-VI wide gap semiconducting barium sulfide. Conf. Phys. Technol. Semicond. Devices Integr. Circuits, 1992. Proceedings of SPIE. Vol. 1523. p. 608-612. Bibcode:1992SPIE.1523..608V. doi:10.1117/12.634082.
^Harvey E. Newton (1957). A History of Luminescence: From the Earliest Times until 1900. Memoirs of the American Physical Society, Philadelphia, J. H. FURST Company, Baltimore, Maryland (USA), Vol. 44, Chapter 1, pp. 11-43.
