Nickel(II) sulfate

Nickel(II) sulfate
Anhydrous	Hexahydrate
IUPAC name Nickel(II) sulfate
Other names Nickelous sulfate
Identifiers
CAS number	7786-81-4 Y, (anhydrous) 10101-97-0 (hexahydrate) 10101-98-1 (heptahydrate)
PubChem	24586
ChemSpider	22989 Y
UNII	4FLT4T3WUN Y
EC number	232-104-9
ChEBI	CHEBI:53001 Y
RTECS number	QR9600000
Jmol-3D images	Image 1
SMILES [Ni+2].[O-]S([O-])(=O)=O
InChI InChI=1S/Ni.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 Y Key: LGQLOGILCSXPEA-UHFFFAOYSA-L Y InChI=1/Ni.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 Key: LGQLOGILCSXPEA-NUQVWONBAG
Properties
Molecular formula	NiSO4
Molar mass	154.75 g/mol (anhydrous) 262.85 g/mol (hexahydrate) 280.86 g/mol (heptahydrate)
Appearance	yellow solid (anhydrous) green crystals (hexahydrate)
Density	3.68 g/cm3 (anhydrous) 2.07 g/cm3 (hexahydrate) 1.948 g/cm3 (heptahydrate)
Melting point	> 100 °C (anhydrous) 53 °C (hexahydrate)
Boiling point	840 °C (anhydrous, decomp)
Solubility in water	650 g/L (20°C) 775 g/L (30°C) (heptahydrate)
Solubility	anhydrous insoluble in ethanol, ether, acetone hexahydrate very soluble in ethanol, ammonia heptahydrate soluble in alcohol
Refractive index (nD)	1.511 (hexahydrate) 1.467 (heptahydrate)
Structure
Crystal structure	cubic (anhydrous) tetragonal (hexahydrate) rhombohedral (hexahydrate)
Hazards
MSDS	External MSDS
EU Index	028-009-00-5
EU classification	Carc. Cat. 1 Muta. Cat. 3 Repr. Cat. 2 Toxic (T) Harmful (Xn) Irritant (Xi) Dangerous for the environment (N)
R-phrases	R49, R61, R20/22, R38, R42/43, R48/23, R68, R50/53
S-phrases	S53, S45, S60, S61
Flash point	Non-flammable
LD50	264 mg/kg
Related compounds
Other cations	Cobalt(II) sulfate Copper(II) sulfate
Y sulfate (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Nickel(II) sulfate, or just nickel sulfate, usually refers to the inorganic compound with the formula NiSO₄(H₂O)₆. This highly soluble blue-coloured salt 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 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.^[1]

X-ray crystallography measurements show that NiSO₄·6H₂O consists of the octahedral [Ni(H₂O)₆]²⁺ ions. These ions in turn are hydrogen bonded to sulfate ions.^[2] Dissolution of the salt in water gives solutions containing the aquo complex [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.^[1]

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 to concentrated aqueous solutions of nickel sulfate precipitates Ni(NH₄)₂SO₄·6H₂O. This blue-coloured solid is analogous to Mohr's salt, Fe(NH₄)₂SO₄·6H₂O.^[1]

Nickel sulfate is used in the laboratory. Columns used in polyhistidine-tagging, useful in biochemistry and molecular biology, 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 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.

Safety

Nickel salts are carcinogenic and irritate the skin.

References

1. ^ ^{a b c} K. Lascelles, L. G. Morgan, D. Nicholls, D. Beyersmann “Nickel Compounds” in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a17_235.pub2.
2. ^ Wells, A. F. (1984). Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.

External links

• International Chemical Safety Card 0063