Cerium

{ syn. }

{ syn. }

0.19%

{ syn. }

0.25 %

{ syn. }

88.48 %

{ syn. }

11.08%

{ syn. }

{ syn. }

Risk

Cerium [ tse ː r] ( also called Zer or cerium ) is a chemical element with the element symbol Ce and atomic number 58 in the periodic table it is in the group of lanthanides and also making it one of the metals of the rare earths.

• 8.1 oxides
• 8.2 halides
• 8.3 Other compounds

History

Cerium was discovered in 1803 by Jöns Jakob Berzelius and Wilhelm von Hisinger and simultaneously by Martin Heinrich Klaproth. It was named after the dwarf planet Ceres. The representation of the item, Carl Gustav Mosander 1825 by reduction of the chloride with sodium.

Occurrence

In nature comes cerium associated with other lanthanides in the so-called Ceriterden before, as for example in Allanite (Ca, Ce, La, Y ) 2 ( Al, Fe ) 3 ( SiO 4 ) 3 ( OH) in monazite (Ce, La, Th, Nd, Y) PO4 as well as in Bastnäsit (Ce, La, Y) CO3F. Cerium is the most abundant element of the lanthanides and is in the element frequency at No. 28 Measured in the Earth's crust to a depth of 16 km, it is represented with 68 g / t, which is more common as tin or lead before. Important deposits are located in Scandinavia, USA, Congo, South Africa and India. The world famous cerium reserves are estimated at 40 million tons.

Extraction and production

After an extensive separation of the cerium oxide is reacted with the companion hydrogen fluoride for cerium fluoride. Then it is reduced with calcium to form calcium fluoride to cerium. The removal of residual calcium residues and contaminants carried in an additional remelting in a vacuum. The annual world production is about 24,000 tons.

Properties

Physical Properties

From cerium four modifications are known:

The silvery white lustrous metal is europium behind the zweitreaktivste element of the lanthanides. Superficial injuries of the protective oxide layer ignite the yellow metal. Above 150 ° C it burns under vigorous annealing for ceria. With water it reacts to cerium hydroxide.

Chemical Properties

Cerium is trivalent in compounds present as colorless or yellow to orange colored tetravalent cation.

Under the influence of heat, it is very strongly affected by ethanol and water. In alkaline solutions it is strongly attacked with the formation of cerium hydroxides. In acids it is dissolved to form salts.

Use

Since the chemical properties of the rare earth elements are similar to, metallic cerium is rarely used in its pure form, but in the mixture in which it is obtained in the production of the rare-earth minerals, called mischmetal.

• In metallurgy, mixed metal is used as an additive for aluminum alloys and high temperature resistant iron-based alloys. It supports the separation of sulfur and oxygen in the smelting process.
• The iron mixed metal alloy mischmetal serves as a source of flint for use in lighters and generating sparks on roller coasters and movie scenes (accident scenes).

Adding small amounts of (more or less pure ) cerium compounds impart certain properties of other materials:

• Ceria ( CeO2 ) is used to stabilize the ceramic catalyst carrier of alumina for automotive catalytic converters
• Part of some special glasses, for example, UV filter and windshields, and dehazers in glass production
• For staining of enamel
• Ceria is used as a polishing agent in glass processing
• Cerium -doped fluorescent dyes ( phosphors ) in picture tubes and white light emitting diodes
• As a dopant in mantles
• Self-cleaning ovens contain a cerium-containing coating
• Cerium ( IV ) sulfate as an oxidizing agent in the quantitative analysis ( Cerimetry )
• As contrast agents in nuclear magnetic resonance
• As a phosphor in gas discharge tubes
• Mixed solved for the regeneration of particulate filters in the fuel
• As part of non- noble metal-containing ceramic alloys in dental technology (ceramic)
• As oxidising agent for organic synthesis with CAN ( cerium ammonium nitrate ), ( NH4) 2Ce (NO3) 6

Biological Significance

First time in 2013 an enzyme discovered in bacteria, the cerium ions for its function needed. The bacteria of the species Methylacidiphilum fumariolicum were isolated from Italian lava. You need to build up the cerium methanol dehydrogenase, an enzyme in methane metabolism. The ion has the role is taken over in like enzymes in other bacteria of calcium ions thereby.

Safety

Cerium, like all lanthanides, slightly toxic. Metallic cerium is already inflamed from 65 ° C. When finely divided metal can heat up in the air without energy supply, and finally catch fire. The Zündbereitschaft depends, among very strongly on the particle size and the degree of distribution. Cerbrände must not be extinguished with water, since evolved gaseous hydrogen.

Compounds

Oxides

• Cerium (III ) oxide Ce.sub.2O.sub.3, shiny gold ceramic solid
• Cerium ( IV) oxide CeO 2
• Cerium (III, IV ) oxide Ce3O4, blue ceramic solid

Halides

• Cerium ( III ) fluoride CeF3
• Cerium ( IV ) fluoride CeF4
• Cerium (III ) chloride CeCl3 · 7 H2O, white highly hygroscopic substance
• Cerium (III) bromide, CeBr3
• Cerium ( III ) iodide CeI3

Other links

• Cerium (III ) sulfate, Ce2 (SO4) 3 · 8 H2O, colorless substance
• Cerium (IV ) sulfate Ce (SO4 ) 2, yellow substance
• Cerium (III ) nitrate Ce ( NO3) 3 · 6H 2 O
• Cerium (III) oxalate, Ce2 ( C2O4 ) 3 · 10 H2O
• Cerium (IV ) ammonium nitrate (CAN ) ( NH4) 2Ce ( NO3) 6
• Ammonium cerium (IV ) sulfate ( NH4) 4Ce (SO4) 4 · H2O
• Cerium (IV) perchlorate, Ce ( ClO4 ) 4

Cerium ( IV ) sulfate

Cerium ( IV ) ammonium nitrate (CAN)