Nickel sulfate, or just nickel sulfate, usually refers to 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

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 NiSO₄(H₂O)₆. This highly soluble blue-coloured salt

Salt

In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

 is a common source of the Ni²⁺ ion for electroplating. Nickel sulfate is paramagnetic.

At least seven sulfate salts of nickel(II) are known. These salts differ, sometimes subtly, in terms of their hydration or structural details. The common tetragonal hexahydrate crystallizes from aqueous solution between 30.7 and 53.8 °C. Below these temperatures, a heptahydrate crystallises and above these temperatures an orthorhombic hexahydrate forms. The yellow anhydrous

Anhydrous

As a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...

 form, NiSO₄, is a high melting solid. This material produced by heating the hydrates above 330 °C. It decomposes at still higher temperatures to nickel oxide.

X-ray crystallography

X-ray crystallography

X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...

 measurements show that NiSO₄·6H₂O consists of the octahedral [Ni(H₂O)₆]²⁺ ions. These ions in turn are hydrogen bond

Hydrogen bond

A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...

ed to sulfate ions. Dissolution of the salt in water gives solutions containing the aquo complex

Metal aquo complex

Metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorates. They have the general stoichiometry [Mn]z+. Their behavior...

 [Ni(H₂O)₆]²⁺.

Production, applications, and coordination chemistry

The salt is usually obtained as a by-product of copper refining. It is also produced by dissolution of nickel metal or nickel oxides in sulfuric acid. Approximately 40,000 tonnes were produced in 2005. It is mainly used for electroplating of nickel.

Aqueous solutions of nickel sulfate reacts with sodium carbonate to precipitate nickel carbonate, a precursor to nickel-based catalysts and pigments. Addition of ammonium sulfate

Ammonium sulfate

Ammonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...

 to concentrated aqueous solutions of nickel sulfate precipitates Ni(NH₄)₂SO₄·6H₂O. This blue-coloured solid is analogous to Mohr's salt

Mohr's salt

Ammonium iron sulfate, or Mohr's Salt, is the inorganic compound with the formula 2Fe2·6H2O. Containing two different cations, Fe2+ and NH4+, it is classified as a double salt of ferrous sulfate and ammonium sulfate. It is a common laboratory reagent...

, Fe(NH₄)₂SO₄·6H₂O.

Nickel sulfate is used in the laboratory. Columns used in polyhistidine-tag

Polyhistidine-tag

A polyhistidine-tag is an amino acid motif in proteins that consists of at least five histidine residues, often at the N- or C-terminus of the protein. It is also known as hexa histidine-tag, 6xHis-tag, and by the trademarked name His-tag...

ging, useful in biochemistry

Biochemistry

Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...

 and molecular biology

Molecular biology

Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...

, are regenerated with nickel sulfate. Aqueous solutions of NiSO₄·6H₂O and related hydrates react with ammonia to give [Ni(NH₃)₆]SO₄ and with ethylenediamine to give [Ni(H₂NCH₂CH₂NH₂)₃]SO₄. The latter is occasionally used as a calibrant for magnetic susceptibility

Magnetic susceptibility

In electromagnetism, the magnetic susceptibility \chi_m is a dimensionless proportionality constant that indicates the degree of magnetization of a material in response to an applied magnetic field...

 measurements because it has no tendency to hydrate.

Natural occurrence

Nickel sulfate occurs as the rare mineral retgersite, which is a hexahydrate. The second hexahydrate is known as nickelhexahydrite (Ni,Mg,Fe)SO₄·6H₂O. The heptahydrate, which is relatively unstable in air, occurs as morenosite. The monohydrate occurs as very rare mineral dwornikite (Ni,Fe)SO₄·H₂O.

External links

• International Chemical Safety Card 0063