Jul 12 2013
Topics Covered
Introduction
Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties
Applications
Introduction
Cobalt is a chemical element with Co as its symbol. It belongs to group 9, periodic number 4 of the periodic table. Its atomic number is 27.
Cobalt is silver-white in color with a bluish tinge. It is a hard, ferromagnetic, brittle element. The primary ores of cobalt are cobaltite, smaltite and erythrite. It can also be obtained as a byproduct of lead, nickel, silver, copper and iron mining and refining processes. Evidence also indicates that it is present in meteorites. Major cobalt producers are DR Congo, Zambia, China, Russia and Australia.
Cobalt is stable in air and is not affected by water. It is active chemically and dissolves in dilute sulfuric acid, nitric or hydrochloric acid. Alkalis have an effect on it as well.
Chemical Properties
The chemical properties of cobalt are provided in the table below.
Chemical Data |
CAS number |
7440-48-4 |
Thermal neutron cross section |
34.8 barns/atom |
Electrode potential |
-0.280 V |
Ionic radius |
0.630 Å |
Electronegativity |
1.88 |
X-ray absorption edge |
1.608 Å |
Electrochemical equivalent |
1.1 g/A/h |
Physical Properties
The following table discusses the physical properties of cobalt.
Properties |
Metric |
Imperial |
Density |
8.80 g/cm3 |
0.318 lb/in3 |
Melting point |
1493 °C |
2719 °F |
Boiling point |
2927 °C |
1603°F |
Mechanical Properties
The mechanical properties of cobalt are tabulated below.
Properties |
Metric |
Imperial |
Yield strength |
225 MPa |
32600 psi |
Poisson’s ratio |
0.32 |
0.32 |
Modulus of elasticity |
211 GPa |
30600 ksi |
Shear modulus |
82.6 GPa |
12000 ksi |
Hardness, Brinell |
125 |
125 |
Hardness, Vickers |
253 |
253 |
Thermal Properties
The thermal properties of cobalt are tabulated below.
Properties |
Metric |
Imperial |
Thermal expansion co-efficient (@20-100°C/68-212°F) |
12.5 µm/m°C |
6.94 µin/in°F |
Thermal conductivity |
69.21 W/mK |
480.3 BTU in/hr.ft².°F |
Applications
The following are the application areas of cobalt:
-
In producing alloys
-
In magnets and magnetic recording media
-
As catalysts for petroleum and chemical industries
-
As drying agents for paints and inks
Cobalt blue is used in stained glass, tiles, porcelain, pottery, and enamel jewelry.