Cobalt nitrate is the
inorganic compound
An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''.
Inorgan ...
with the formula Co
(NO3)2.xH
2O. It is a
cobalt
Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...
(II)
salt
In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
. The most common form is the
hexahydrate
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...
Co(NO
3)
2·6H
2O, which is a red-brown
deliquescent
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...
salt that is soluble in water and other polar solvents.
[John Dallas Donaldson, Detmar Beyersmann, "Cobalt and Cobalt Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. ]
Composition and structures
As well as the anhydrous compound Co(NO
3)
2, several
hydrate
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...
s of cobalt(II) nitrate exist. These hydrates have the
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
Co(NO
3)
2·''n''H
2O, where ''n'' = 0, 2, 4, 6.
Anhydrous cobalt(II) nitrate adopts a three-dimensional polymeric network structure, with each cobalt(II) atom approximately octahedrally coordinated by six oxygen atoms, each from a different nitrate ion. Each nitrate ion coordinates to three cobalts. The dihydrate is a two-dimensional polymer, with nitrate bridges between Co(II) centres and hydrogen bonding holding the layers together. The tetrahydrate consists of discrete, octahedral
H2O)4Co(NO3)2molecules. The hexahydrate is better described as hexaaquacobalt(II) nitrate,
o(OH2)6NO
3]
2, as it consists of discrete
o(OH2)6sup>2+ and
O3sup>− ions. Above 55 °C, the hexahydrate converts to the trihydrate and at higher temperatures to the monohydrate.
[
Cobalt(II)-nitrate-xtal-2002-CM-3D-SF.png, Co(NO3)2
Cobalt(II)-nitrate-dihydrate-xtal-1976-CM-3D-balls.png, Co(NO3)2·2H2O
Cobalt(II)-nitrate-tetrahydrate-xtal-1975-CM-3D-balls.png, Co(NO3)2·4H2O
Hexaaquacobalt(II)-nitrate-xtal-1973-unit-cell-CM-3D-balls.png, Co(NO3)2·6H2O
]
Uses and reactions
It is commonly reduced to metallic high purity cobalt.[ It can be absorbed on to various ]catalyst support
In chemistry, a catalyst support or carrier is a material, usually a solid with a high surface area, to which a catalyst is affixed. The activity of heterogeneous catalysts is mainly promoted by atoms present at the accessible surface of the ma ...
s for use in Fischer–Tropsch catalysis. It is used in the preparation of dyes and inks.
Cobalt(II) nitrate is a common starting material for the preparation of coordination complexes such as cobaloximes, carbonatotetraamminecobalt(III), and others.
Production
The hexahydrate is prepared treating metallic cobalt or one of its oxides, hydroxides, or carbonate with nitric acid
Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
:
:Co + 4 HNO3 + 4 H2O → Co(H2O)6(NO3)2 + 2 NO2
:CoO + 2 HNO3 + 5 H2O → Co(H2O)6(NO3)2
:CoCO3 + 2 HNO3 + 5 H2O → Co(H2O)6(NO3)2 + CO2
References
{{nitrates
Cobalt(II) compounds
Nitrates
Oxidizing agents