Barium sulfide is the inorganic compound

Inorganic compound

Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula Ba

Barium

Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...

S

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

. BaS is an important precursor to other barium compounds including BaCO₃ and the pigment lithopone

Lithopone

Lithophone is a white pigment consisting of a mixture of barium sulfate and zinc sulfide. It is used in interior paints and in some enamels. It is widely used for white paint.-History:...

, ZnS/BaSO₄. Like other chalcogenide

Chalcogenide

A chalcogenide is a chemical compound consisting of at least one chalcogen ion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term is more commonly reserved for sulfides, selenides, and tellurides, rather than...

s of the alkaline earth metals, BaS is a short wavelength

Wavelength

In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

 emitters for electronic displays. It is colorless, although like many sulfides, it is commonly obtained in impure colored forms.

Discovery, production, properties

The BaS was prepared by Vincentius (or Vincentinus) Casciarolus (or Casciorolus, 1571-1624) via reduction of BaSO₄

Barium sulfate

Barium sulfate is the inorganic compound with the chemical formula BaSO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs as the mineral barite, which is the main commercial source of barium and materials prepared from it...

 (available as the mineral barite

Barite

Baryte, or barite, is a mineral consisting of barium sulfate. The baryte group consists of baryte, celestine, anglesite and anhydrite. Baryte itself is generally white or colorless, and is the main source of barium...

).
It is currently manufactured by an improved version of Casciarolus's route using coke in place of flour. This kind of conversion is called a carbothermic reaction

Carbothermic reaction

Carbothermic reactions use carbon as reducing agent, usually for metal oxides. These chemical reactions are usually conducted at several hundreds of degree Celsius. Such processes are applied for production of the elemental forms of many elements. Carbothermic reactions are not however useful for...

:

BaSO₄ + 2 C → BaS + 2 CO₂

The phosphorescence of the substance made the material a curiosity and various alchemists and chemists made experiments with the material which was known as Lapis Boloniensis, Chrysolapis or bologna stone.

Andreas Sigismund Marggraf

Andreas Sigismund Marggraf

Andreas Sigismund Marggraf was a German chemist and pioneer of analytical chemistry from Berlin, which was then the capital of Brandenburg, a major principality of the Holy Roman Empire. He isolated zinc in 1746 by heating calamine and carbon...

 showed that calcite

Calcite

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

 and gypsum

Gypsum

Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...

 were not very suitable for the production of the bologna stone, but a special heavy fluorspar, in the end he concluded that calcium sulfate

Calcium sulfate

Calcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite , it is used as a desiccant. It is also used as a coagulant in products like tofu. In the natural state, unrefined calcium sulfate is a translucent, crystalline white rock...

 is the material from which the bologna stone is made.

BaS crystallizes with the NaCl structure, featuring octahedral Ba²⁺ and S^2- centres.

Safety

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

Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

upon contact with water. The particular problem with BaS is that its name resembles that of barium sulfate, an insoluble, non-toxic material given in large doses to some medical patients. Switching BaS for BaSO₄ is lethal.