Barium sulfide

Barium sulfide is the chemical compound with the formula BaS. This material was once known as "Bologna Stone", the first synthetic phosphor. Currently the chalcogenides of the alkaline earth metals are intensely studied as candidates for short wavelength emitters for electronic displays.^[1] BaS is considered to be the most important synthetic material of barium, being the precursor to BaCO₃ and the pigment lithopone.^[2]

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Discovery, production, properties

The BaS was prepared by Vincentius (or Vincentinus) Casciarolus (or Casciorolus, 1571-1624) via a crude version of what is now known as a "carbothermic reduction", employing flour in place of carbon:^[3]

BaSO₄ + 2 C → BaS + 2 CO₂

BaSO₄ is available as the common mineral barite.

BaS, m.p. 1200 °C, crystallizes with the NaCl structure and is currently manufactured by an improved version of Casciarolus's route: using coke in place of flour. It is colorless, although like many sulfides, it is commonly obtained in impure colored forms.

Safety

BaS is quite poisonous, as are related sulfides, such as CaS, which evolve toxic hydrogen sulfide upon contact with water. The particular problem with BaS is that its name resembles that of the insoluble, non-toxic material given in large doses to some medical patients. Switching BaS for BaSO₄ is lethal.

References

1. ^ Vij, D. R.; Singh, N. "Optical and electrical properties of II-VI wide gap semiconducting barium sulfide" Proceedings of SPIE-The International Society for Optical Engineering (1992), 1523(Conf. Phys. Technol. Semicond. Devices Integr. Circuits, 1992), 608-12.
2. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
3. ^ F. Licetus, Litheosphorus, sive de lapide Bononiensi lucem in se conceptam ab ambiente claro mox in tenebris mire conservante, Utini, ex typ. N. Schiratti, 1640. See http://www.chem.leeds.ac.uk/delights/texts/Demonstration_21.htm