History

Cobalt compounds have been used for centuries to imparta rich blue color to glass, glazes and ceramics. Cobalthas been detected in Egyptian sculpture and Persianjewelry from the third millennium BC, in the ruinsof Pompeii (destroyed in 79 AD), and in China dating fromthe Tang dynasty (618–907 AD) and the Mingdynasty (1368–1644 AD).

Cobalt has been used to color glass since the BronzeAge. The excavation of the Uluburun shipwreck yielded aningot of blue glass, which was cast during the 14thcentury BC. Blue glass items from Egypt are colored withcopper, iron, or cobalt. The oldest cobalt-colored glasswas from the time of the Eighteenthdynasty in Egypt (1550–1292 BC). The location where thecobalt compounds were obtained is unknown.

History

Swedish chemist Georg Brandt (1694–1768) is credited with discovering cobaltcirca 1735, showing it to be a newpreviously unknown element different frombismuth and other traditional metals, andcalling it a new "semi-metal.He was able toshow that compounds of cobalt metal werethe source of the blue color in glass, whichpreviously had been attributed tothe bismuth found with cobalt. Cobaltbecame the first metal to be discoveredsince the pre-historical period, during whichall the known metals (iron, copper, silver,gold, zinc, mercury, tin, lead and bismuth)had no recorded discoverers.

source

The stable form of cobalt is createdin supernovas via the r-process.Itcomprises 0.0029% of the Earth's crust and isone of the first transition metals.

Free cobalt (the native metal) is not found inon Earth due to the amount of oxygen in theatmosphere and chlorine in the ocean. Thoughthe element is of medium abundance, naturalcompounds of cobalt are numerous. Smallamounts of cobalt compounds are found inmost rocks, soil, plants, and animals.

Source

Cobalt in compound form occurs as a minorcomponent of copper and nickel minerals. It isthe major metallic component in combinationwith sulfur and arsenic in the sulfidiccobaltite(CoAsS), safflorite (CoAs2), glaucodot ((Co,Fe)AsS), and skutterudite (CoAs3) minerals. Themineral cattierite is similar to pyrite and occurstogether with vaesite in the copper deposits ofthe Katanga Province. Upon contact with theatmosphere, weathering occurs and the sulfideminerals oxidize to form pink erythrite ("cobaltglance":Co3(AsO4)2·8H2O)and spherocobaltite(CoCO3).

How to get

The main ores of cobalt are cobaltite, erythrite, glaucodot and skutterudite (see above), but most cobalt is obtained not by active mining of cobalt ores, but rather by reducing cobalt compounds that occur as by-products of nickel and copper mining activities.

Several methods exist for the separation of cobalt from copper and nickel. They depend on the concentration of cobalt and the exact composition of the used ore. One separation step involves froth flotation, in which surfactants bind to different ore components, leading to an enrichment of cobalt ores.

How to get

Subsequent roasting converts the ores to the cobalt sulfate, whereas the copper and the iron are oxidized to the oxide. The leaching with water extracts the sulfate together with the arsenates. The residues are further leached with sulfuric acid yielding a solution of copper sulfate. Cobalt can also be leached from the slag of the copper smelter.

The products of the above-mentioned processes are transformed into the cobalt oxide (Co3O4). This oxide is reduced to the metal by the aluminothermic reaction or reduction with carbon in a blast furnace.

properties

Color metallic gray

Phase solid

Melting point 1768 K

Boiling point 3200 K

Density (near r.t.) 8.90 g·cm−3

Liquid density at m.p. 8.86 g·cm−3

Heat of fusion 16.06 kJ·mol−1

Heat of vaporization 377 kJ·mol−1

Molar heat capacity 24.81 J·mol−1·K−1

compound

Green cobalt(II) oxide (CoO)

the black cobalt(II) sulfides, CoS2

cobalt(III) sulfide (Co2S3).

cobalt(II) fluoride (CoF2, pink),

cobalt(II) chloride(CoCl2, blue),

cobalt(II) bromide (CoBr2, green),

cobalt(II) iodide (CoI2, blue-black)

Compund

tris(triphenylphosphine)cobalt(I) chloride

((P(C6H5)3)3CoCl)

caesium hexafluorocobaltate (Cs2CoF6)

potassium percobaltate (K3CoO4).

[Co(NH3)6]Cl3 cobalt(III) hexammine

chloride

Cobalt carbonyl (Co2(CO)8)

Reaction

With acids :

CoO + 2 HX → CoX2 + H2O

With water :

CoCl2 + H2O → CoO + H2 + Cl2

with base :

CoX + 2 KOH → Co(OH)2 + K2X

With oxygen :

6 CoO + O 2 → 2 Co3O4

application

alloyscolouring

bateries

radioisotopcatalist

History

there are Chinese manuscripts suggestingthat "white copper" (cupronickel, knownas baitong) was used there between 1700and 1400 BC. This Paktong white copperwas exported to Britain as early as the17th century, but the nickel content of thisalloy was not discovered until 1822.

In 1751, Baron Axel Fredrik Cronstedt wastrying to extract copper from kupfernickel—and instead produced a white metal that henamed after the spirit that had given itsname to the mineral, nickel. In modernGerman, Kupfernickel or Kupfer-Nickeldesignates the alloy cupronickel.

Source

On Earth, nickel occurs most often in combination with sulfur and ironin pentlandite, with sulfur in millerite, with arsenic in themineral nickeline, and with arsenic and sulfur in nickel galena. Nickel iscommonly found in iron meteorites as the alloys kamacite and taenite.

Australia and New Caledonia have the biggest estimate reserves (45%all together).

In terms of World Resources, identified land-based resourcesaveraging 1% nickel or greater contain at least 130 million tons ofnickel (about the double of known reserves). About 60% isin laterites and 40% is in sulfide deposits.

Based on geophysical evidence, most of the nickel on Earth ispostulated to be concentrated in the Earth's outer and innercores.Kamacite and taenite are naturally occurring alloys of iron andnickel. For kamacite, the alloy is usually in the proportion of 90:10 to95:5, although impurities (such as cobalt or carbon) may be present,while for taenite the nickel content is between 20% and 65%. Kamaciteand taenite occur in nickel iron meteorites.

How to get

Purification of nickel oxides to obtain the purest metal is performed via the Mond process, which increases the nickel concentrate to greater than 99.99% purity. This process was patented by Ludwig Mond and has been in industrial use since before the beginning of the 20th century. In the process, nickel is reacted with carbon monoxide at around 40–80 °C to form nickel carbonyl in the presence of a sulfur catalyst. Iron gives iron pentacarbonyl, too, but this reaction is slow. If necessary, the nickel may be separated by distillation. Dicobalt octacarbonyl is also formed in nickel distillation as a by-product, but it decomposes to tetracobalt dodecacarbonyl at the reaction temperature to give a non-volatile solid.

How to get

Nickel is re-obtained from the nickel carbonyl by one of two processes. It may be passed through a large chamber at high temperatures in which tens of thousands of nickel spheres, called pellets, are constantly stirred. It then decomposes, depositing pure nickel onto the nickel spheres. Alternatively, the nickel carbonyl may be decomposed in a smaller chamber at 230 °C to create a fine nickel powder. The resultant carbon monoxide is re-circulated and reused through the process. The highly pure nickel produced by this process is known as "carbonyl nickel".

Properties

Phase solid

Melting point 1728 K

Boiling point 3003 K

Density (near r.t.) 8.908 g·cm−3

Liquid density at m.p. 7 81 g·cm−3

Heat of fusion 17.48 kJ·mol−1

Heat of vaporization 379 kJ·mol−1

Molar heat capacity 26.07 J·mol−1·K−1

Compound

Tetracarbonylnickel (Ni(CO)4)

Bis(triphenylphosphine)nickel(II)

chloride NiCl2[P(C6H5)3]2

K4[Ni2(CN)6] and K2[Ni2(CN)6]

Nickel aquo complex [Ni(H2O)6]2+

Compound

Color of various Ni(II) complexes in aqueous solution. From left

to right, [Ni(NH3)6]2+, [Ni(C2H4(NH2)2)]2+, [NiCl4]2−, and

[Ni(H2O)6]2+

Reaction

Reaction with oxygen

2Ni + O2 → 2NiO

react with halides

Ni + Cl2 → NiCl2

react with H2O

Ni + H2O → NiO + H2

react with acid

Ni + HNO3 → Ni(NO3)2 + NO + H2O

Application

The fraction of global nickel production

presently used for various applications is

as follows: 46% for making nickel steels;

34%innonferrous alloys and superalloys;

14% electroplating, and 6% into other

uses (catalyst, batteries, magnet, etc)