Barium sulfide is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

with the formula Ba S. BaS is the barium compound produced on the largest scale. It is an important precursor to other barium compounds including BaCO₃ and the pigment lithopone, ZnS/BaSO₄. Like other chalcogenides of the alkaline earth metals, BaS is a short

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...

emitter for

electronic display An electronic visual display, informally a screen, is a display device for presentation of images, Plain text, text, or video transmitted electronically, without producing a permanent record. Electronic visual displays include television sets, com ...

s. It is colorless, although like many sulfides, it is commonly obtained in impure colored forms.

Discovery, production and properties

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 Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...

). It is currently manufactured by an improved version of Casciarolus's process using coke in place of flour and

charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, ...

. This kind of conversion is called a

carbothermic reaction Carbothermic reactions involve the reduction of substances, often metal oxides (O^2-), using carbon as the reducing agent. These chemical reactions are usually conducted at temperatures of several hundred degrees Celsius. Such processes are applie ...

: :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 Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions ...

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

, give a white solid of barium carbonate, a source material for many commercial barium compounds. According to Harvey (1957),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. in 1603, Vincenzo Cascariolo used

, found at the bottom of Mount Paterno near

Bologna Bologna (, , ; egl, label= Emilian, Bulåggna ; lat, Bononia) is the capital and largest city of the Emilia-Romagna region in Northern Italy. It is the seventh most populous city in Italy with about 400,000 inhabitants and 150 different na ...

, in one of his non-fruitful attempts to produce

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...

. After grinding and heating the mineral with charcoal under reducing conditions, he obtained a persistent

luminescent Luminescence is spontaneous emission of light by a substance not resulting from heat; or "cold light". It is thus a form of cold-body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions or stress on a crystal ...

material rapidly called ''Lapis Boloniensis'', or Bolognian stone. The

phosphorescence Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluo ...

of the material obtained by Casciarolo made it a curiosity. BaS crystallizes with the

NaCl structure In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties ...

, featuring octahedral Ba²⁺ and S²⁻ centres. The observed

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depen ...

of barium sulfide is highly sensitive to impurities.

Safety

BaS is quite poisonous, as are related sulfides, such as CaS, which evolve toxic

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The under ...

upon contact with water.

References

{{Sulfides Barium compounds Sulfides Cubic minerals Phosphors and scintillators Rock salt crystal structure