Cobalt (27)

Cobalt (pronounced koh-bawlt), is a brittle, hard, silver-grey transition metal with magnetic properties similar to those of iron (ferromagnetic). Cobalt is present in meteorites and at room temperature is a solid with a close packed hexagonal structure. Ore deposits are found in Zaire, Morocco and Canada. The isotope cobalt-60 (60Co) is an artificially produced isotope used as a source of γ rays (its high energy radiation is useful for sterilization in medicine and of foods). Cobalt salts color glass a beautiful deep blue color. Cobalt compounds are important catalysts in a number of industrial processes. Cobalt is required in small amounts for life and is the only metal found in vitamins (cobalt is the critical component of vitamin B12.

•Name: Cobalt
•Symbol: Co
•Atomic number: 27
•Atomic weight: 58.933195
•Standard state: solid at 298 K
•CAS Registry ID: 7440-48-4
•Group in periodic table: 9
•Period in periodic table: 4
•Block in periodic table: d-block
•Color: lustrous, metallic, greyish-pink tinge
•Classification: Metallic

Historical information

Cobalt was discovered by Georg Brandt at 1735 in Sweden. Origin of name is from the German word "kobald" meaning "goblin" or evil spirit. Minerals containing cobalt were of value to the early civilizations of Egypt and Mesopotamia for coloring glass deep blue (my favorite transition element as far as what colors they produce!).

Cobalt was announced to be an element by Georg Brandt about 1739 (or possibly 1735). He had been trying to demonstrate that the blue color of glass was because of a new element, cobalt, rather than bismuth, an element often found in the same locations as cobalt.

Physical properties

•Melting point: 1768 [or 1495 °C (2723 °F)] K
•Boiling point: 3200 [or 2927 °C (5301 °F)] K
•Density of solid: 8900 kg m-3

Orbital properties

•Ground state electron configuration: [Ar].3d7.4s2
•Shell structure: 2.8.15.2
•Term symbol: 4F9/2

Isolation

It is not normally necessary to make cobalt in the laboratory as it is available readily commercially. Many ores contain cobalt but not many are of economic importance. These include the sulfides and arsenides linnaeite, Co3S4, cobaltite, CoAsS, and smaltite, CoAs2. Industrially, however, it is normally produced as a byproduct from the production of copper, nickel, and lead. Cobalt has only one naturally occurring stable isotope and is a usually obtained as a byproduct when nickel, silver, lead, copper, and iron are mined and refined. It can be found in cobaltite, glaucodot, linnaelite, and smaltite mineral ores.

Normally the ore is "roasted" to form a mixture of metals and metal oxides. Treatment with sulphuric acid leaves metallic copper as a residue and dissolves out iron, cobalt, and nickel as the sulfates. Iron is obtained by precipitation with lime (CaO) while cobalt is produced as the hydroxide by precipitation with sodium hypochlorite (NaOCl)

2Co2+(aq) + NaOCl(aq) + 4OH-(aq) + H2O → 2Co(OH)3(s) + NaCl(aq)

The trihydroxide Co(OH)3 is heated to form the oxide and then reduced with carbon (as charcoal) to form cobalt metal.

2Co(OH)3 (heat) → Co2O3 + 3H2O

2Co2O3 + 3C → Co + 3CO2

Interesting Facts:

1. Cobalt (English) Cobalt (French) Cobalt (Deutsch) Cobalto (Italian/Spanish) Kobolt (Swedish)

2. According to the World English Dictionary, Cobalt comes from the German word “Kobalt” which is derived from the Middle High German word “kobolt” meaning “goblin” because miners believed “that malicious goblins placed it in the silver ore.”

3. Alnico alloys (containing Aluminum, Cobalt, and Nickel) are used when making powerful permanent magnets.

4. Stellite alloys (containing Chromium, Cobalt, and Tungsten) are used in the production of high-speed, high-temperature cutting tools because of Cobalt's high melting point and strength under high temperatures.

5. Other alloys containing Cobalt are used in the production of gas turbines and jet engines.

6. Cobalt's only radioactive isotope, Cobalt-60 (half-life of 5.27 years), is a source of gamma rays. It can be used in some forms of cancer treatment and as a medical tracer.

7. Compounds containing Cobalt have been used as dyes and coloring agents. The common names of some of the compounds are: Ceruleum, Cobalt blue, Cobalt green, Cobalt yellow, and new blue.

8. Cobalt is a part of the vitamin B12 (also known as cobalamin) which is of nutritional importance. According to the Office of Dietary Supplements, it is a naturally occurring water-soluble vitamin which is required for “proper red blood formation, neurological function, and DNA synthesis.” Deficiency of this mineral in daily diet can lead to “megaloblastic anemia, fatigue, weakness, constipation, loss of appetite, and weight loss.”

9. Canada, Morocco, and Zaire are important sources of Cobalt. The U.S. Geological Survey reports the possibility of Cobalt-rich zones in the north central Pacific Ocean near the Hawaiian Islands and other nearby U.S. Territories.

10. Lithium ion, Nickel-Cadmium, and Nickel metal hydride batteries are made with significant amounts of Cobalt.

11. Cobalt usage in rechargeable batteries increased from 22% in 2006 to 25% in 2007 which accounts for the fastest growing use of the metal.

12. Global Cobalt consumption in 1995 was 24,000 tons and in 2008 that number increased to 60,800 tons. That is a 7.4% increase in a span of 13 years and if demand continues it is projected that this number will grow to 72,500 tonnes in 2011.

13. Although iron is an essential mineral, too much of it is extremely toxic. Free iron in the blood reacts with peroxides to form free radicals that damage DNA, protein, lipids and other cellular components, leading to illness and sometimes death. 20 milligrams of iron per kilogram of body weight is toxic, while 60 milligrams per kilogram is lethal.

14. Iron primarily forms compounds with +2 and +3 oxidation states.