Nickel sulfide is any

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 chemistr ...

with the formula NiS_x. They range in color from bronze (Ni₃S₂) to black (NiS₂). The nickel sulfide with simplest stoichiometry is NiS, also known as the mineral

millerite Millerite is a nickel sulfide mineral, Ni S. It is brassy in colour and has an acicular habit, often forming radiating masses and furry aggregates. It can be distinguished from pentlandite by crystal habit, its duller colour, and general l ...

. From the economic perspective, Ni₉S₈, the mineral

pentlandite Pentlandite is an iron–nickel sulfide with the chemical formula . Pentlandite has a narrow variation range in Ni:Fe but it is usually described as having a Ni:Fe of 1:1. It also contains minor cobalt, usually at low levels as a fraction of wei ...

, is the chief source of mined nickel. Other minerals include

heazlewoodite Heazlewoodite, Ni3S2, is a rare sulfur-poor nickel sulfide mineral found in serpentinitized dunite. It occurs as disseminations and masses of opaque, metallic light bronze to brassy yellow grains which crystallize in the trigonal crystal system. ...

(Ni₃S₂) and

polydymite Polydymite, Ni2+Ni23+S4, is a supergene thiospinel sulfide mineral associated with the weathering of primary pentlandite nickel sulfide. Polydymite crystallises in the isometric system, with a hardness of 4.5 to 5.5 and a specific gravity of abo ...

(Ni₃S₄). The mineral

Vaesite Vaesite ( Ni S2) is a mineral found together with cattierite in the Democratic Republic of Congo. It is named after Johannes F. Vaes, a Belgian mineralologist. It is part of the pyrite group The pyrite group of minerals is a set of cubic crysta ...

is NiS₂. Some nickel sulfides are used commercially as catalysts.

Structure

Like many related materials, nickel sulfide adopts the

nickel arsenide Nickeline or niccolite is a mineral consisting primarily of nickel arsenide (NiAs). The naturally-occurring mineral contains roughly 43.9% nickel and 56.1% arsenic by mass, but composition of the mineral may vary slightly. Small quantities of s ...

motif. In this structure, nickel is octahedral and the sulfide centers are in trigonal prismatic sites. NiS has two polymorphs. The α-phase has a hexagonal unit cell, while the β-phase has a rhombohedral cell. The α-phase is stable at temperatures above , and converts into the β-phase at lower temperatures. That

phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states o ...

causes an increase in volume by 2-4%.

Synthesis and reactions

The precipitation of solid black nickel sulfide is a mainstay of traditional

qualitative inorganic analysis Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find the elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, therefore materials in other forms m ...

schemes, which begins with the separation of metals on the basis of the solubility of their sulfides. Such reactions are written: :Ni²⁺ + H₂S → NiS + 2 H⁺ Many other more controlled methods have been developed, including solid state metathesis reactions (from NiCl₂ and Na₂S) and high temperature reactions of the elements. The most commonly practiced reaction of nickel sulfides involves conversion to nickel oxides. This conversion involves heating the sulfide ores in air: :

Occurrence

Natural

The mineral

is also a nickel sulfide with the molecular formula NiS, although its structure differs from synthetic stoichiometric NiS due to the conditions under which it forms. It occurs naturally in low temperature hydrothermal systems, in cavities of carbonate rocks, and as a byproduct of other nickel minerals.Gamsjager H. C., Bugajski J., Gajda T., Lemire R. J., Preis W. (2005) Chemical Thermodynamics of Nickel, Amsterdam, Elsevier B.V. Millerite-Chalcopyrite-Calcite-284770

In glass manufacturing

Float glass Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin, although lead and other various low- melting-point alloys were used in the past. This method gives the sheet uniform thickness and very flat sur ...

contains a small amount of nickel sulfide, formed from the sulfur in the fining agent and the nickel contained in metallic alloy contaminants. Nickel sulfide inclusions are a problem for

tempered glass Tempered or toughened glass is a type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into compression and the interior into tensio ...

applications. After the tempering process, nickel sulfide inclusions are in the metastable alpha phase. The inclusions eventually convert to the beta phase (stable at low temperature), increasing in volume and causing cracks in the glass. In the middle of tempered glass, the material is under tension, which causes the cracks to propagate and leads to spontaneous glass fracture. That spontaneous fracture occurs years or decades after glass manufacturing.

References

{{Sulfides Nickel compounds Sulfides Nickel arsenide structure type