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7440-45-1

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Identification

Name
CERIUM
CAS
7440-45-1
EINECS(EC#)
231-154-9
Molecular Formula
Ce
MDL Number
MFCD00010924
Molecular Weight
140.12
MOL File
7440-45-1.mol

Chemical Properties

Definition
A rare-earth element of the lanthanide group of the periodic table. Four stable isotopes.
Appearance
grey metal pieces or blocks
Melting point 
795 °C(lit.)

mp 
795 °C(lit.)

Boiling point 
3443 °C(lit.)

bp 
3443 °C(lit.)

density 
6.67 g/mL at 25 °C(lit.)

form 
powder

color 
Silver-gray
Water Solubility 
soluble dilute mineral acids [KIR78]
Sensitive 
Air & Moisture Sensitive
Merck 
13,2003
History
Cerium was discovered in 1803 by Klaproth and by Berzelius and Hisinger; metal prepared by Hillebrand and Norton in 1875. Cerium is the most abundant of the metals of the so-called rare earths. It is found in a number of minerals including allanite (also known as orthite), monazite, bastnasite, cerite, and samarskite. Monazite and bastnasite are presently the two most important sources of cerium. Large deposits of monazite found on the beaches of Travancore, India, in river sands in Brazil, and deposits of allanite in the western United States, and bastnasite in Southern California will supply cerium, thorium, and the other rare-earth metals for many years to come. Metallic cerium is prepared by metallothermic reduction techniques, such as by reducing cerous fluoride with calcium, or by electrolysis of molten cerous chloride or other cerous halides. The metallothermic technique is used to produce highpurity cerium. Cerium is especially interesting because of its variable electronic structure. The energy of the inner 4f level is nearly the same as that of the outer or valence electrons, and only small amounts of energy are required to change the relative occupancy of these electronic levels. This gives rise to dual valency states. For example, a volume change of about 10% occurs when cerium is subjected to high pressures or low temperatures. It appears that the valence changes from about 3 to 4 when it is cooled or compressed. The low temperature behavior of cerium is complex. Four allotropic modifications are thought to exist: cerium at room temperature and at atmospheric pressure is known as γ cerium. Upon cooling to –16°C, γ cerium changes to β cerium. The remaining γ cerium starts to change to α cerium when cooled to –172°C, and the transformation is complete at –269°C. α Cerium has a density of 8.16; δ cerium exists above 726°C. At atmospheric pressure, liquid cerium is more dense than its solid form at the melting point. Cerium is an iron-gray lustrous metal. It is malleable, and oxidizes very readily at room temperature, especially in moist air. Except for europium, cerium is the most reactive of the “rare-earth” metals. It slowly decomposes in cold water, and rapidly in hot water. Alkali solutions and dilute and concentrated acids attack the metal rapidly. The pure metal is likely to ignite if scratched with a knife. Ceric salts are orange red or yellowish; cerous salts are usually white. Cerium is a component of misch metal, which is extensively used in the manufacture of pyrophoric alloys for cigarette lighters, etc. Natural cerium is stable and contains four isotopes. Thirtytwo other radioactive isotopes and isomers are known. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. The oxide is an important constituent of incandescent gas mantles and it is emerging as a hydrocarbon catalyst in “self-cleaning” ovens. In this application it can be incorporated into oven walls to prevent the collection of cooking residues. As ceric sulfate it finds extensive use as a volumetric oxidizing agent in quantitative analysis. Cerium compounds are used in the manufacture of glass, both as a component and as a decolorizer. The oxide is finding increased use as a glass polishing agent instead of rouge, for it is much faster than rouge in polishing glass surfaces. Cerium compounds are finding use in automobile exhaust catalysts. Cerium is also finding use in making permanent magnets. Cerium, with other rare earths, is used in carbon-arc lighting, especially in the motion picture industry. It is also finding use as an important catalyst in petroleum refining and in metallurgical and nuclear applications. In small lots, cerium costs about $5/g (99.9%).
CAS DataBase Reference
7440-45-1(CAS DataBase Reference)

Hazard Information

Chemical Properties
grey metal ingots (in mineral oil)
Uses
In metallurgy as stabilizers in alloys and as an alternative to thorium oxide in welding electrodes. In glass as polishing agent, decolorizer to stabilize impurities, to render glass opaque to near uv radiation, to resist discoloration from strong light or high energy electron bombardment (as in television screens). In ceramics as an opacifying and strengthening agent. Catalysts to impart high cracking activity for crude oil processing, in automotive exhaust control devices, as combustion additive, polymerization initiator, paint drier, polymer stabilizer. As phosphor in fluorescent lamps, cathode ray tubes and thorium dioxide gas mantles.
General Description
Cerium is a gray colored, ductile solid. This form of cerium is slabs, ingots or rods. When heated to high temperatures CERIUM, SLABS, INGOTS OR RODS(7440-45-1) will burn readily and may be difficult to extinguish. CERIUM, SLABS, INGOTS OR RODS(7440-45-1) is used to make signaling devices.
Reactivity Profile
CERIUM is a strong reducing agent. Resembles aluminum in its chemical properties. [Lewis]. Reactivity is enhanced by a state of high physical subdivision, as in TURNINGS OR GRITTY POWDER. Attacked by dilute and concentrated mineral acids and alkalis with the generation of flammable gases. Readily oxidized by moist air at room temperature. Reacts with zinc with explosively violence. Gives very exothermic reactions with antimony or bismuth. Reacts violently with phosphorus at 400-500°C [Mellor 8, Supp. 3:347 1971].
Air & Water Reactions
Finely divided metal powder is pyrophoric [Bretherick 1979 p. 170-171]. This material will react vigorously if exposed to water or moist air and will generate flammable and/or toxic fumes.
Hazard
May ignite on heating to 300F (148.9C). Strong reducing agent.
Health Hazard
Oxides from metallic fires are a severe health hazard. Inhalation or contact with substance or decomposition products may cause severe injury or death. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may cause pollution.
Fire Hazard
May react violently or explosively on contact with water. Some are transported in flammable liquids. May be ignited by friction, heat, sparks or flames. Some of these materials will burn with intense heat. Dusts or fumes may form explosive mixtures in air. Containers may explode when heated. May re-ignite after fire is extinguished.

Safety Data

Hazard Codes 
C,Xn,F
Risk Statements 
R22:Harmful if swallowed.
R23:Toxic by inhalation.
R36/38:Irritating to eyes and skin .
R36/37/38:Irritating to eyes, respiratory system and skin .
R20/21/22:Harmful by inhalation, in contact with skin and if swallowed .
R11:Highly Flammable.
Safety Statements 
S26:In case of contact with eyes, rinse immediately with plenty of water and seek medical advice .
S36:Wear suitable protective clothing .
S36/37/39:Wear suitable protective clothing, gloves and eye/face protection .
S16:Keep away from sources of ignition-No smoking .
RIDADR 
UN 2031 8/PG 2

WGK Germany 
3


10
TSCA 
Yes
HazardClass 
4.1
PackingGroup 
II
HS Code 
28053090
Safety Profile
Cerium resembles aluminum in its pharmacological action as well as in its chemical properties. The insoluble salts such as the oxalates are stated to be nontoxic even in large doses. It is used to prevent vomiting in pregnancy. The average dose is from 0.05 to 0.5 g. The effect on the central nervous system of the rare-earth metals following inhalation may preclude welding operations with these materials to any large extent. Cerium is stated to produce polycythemia but is useless in the treatment of anemia owing to its toxic effects. The salts of cerium increase the blood coagulation rate. See also RARE EARTHS. A strong reducing agent. Moderate fire hazard; ignites spontaneously in air at 150-180'. Moderate explosion hazard in the form of dust when exposed to flame. The metal or its alloys spark with friction. Many alloys are pyrophoric in air. See also IRON DUST. Explosive reaction with zinc. Very exothermic reaction with antimony or bismuth. Ignites when heated in atmospheres of CO2 + N2, Cl2, or Br2. Violent reaction when heated with phosphorus (4OO℃), silicon (1400℃).

Raw materials And Preparation Products

Raw materials
Rare earth chlorides

Material Safety Data Sheet(MSDS)

msds information
cerium(7440-45-1).msds

Questions And Answer

Overview
Cerium is the most abundant of the rare earths. It is characterized chemically by having two valence states, the +3 cerous and +4 ceric states. The ceric state is the only non-trivalent rare earth ion stable in aqueous solutions. It is, therefore, strongly acidic and a strong oxidizer. The cerous state closely resembles the other trivalent rare earths.
The numerous commercial applications for Cerium include glass and glass polishing, phosphors, ceramics, catalysts and metallurgy:
In glass industry, it is considered to be the most efficient glass polishing agent for precision optical polishing. It is also used to decolorize glass by keeping iron in its Ferrous state. The ability of Cerium-doped glass to block out ultra violet light is utilized in the manufacturing of medical glassware and aerospace windows. It is also used to prevent polymers from darkening in sunlight and to suppress discoloration of television glass. It is applied to optical components to improve performance.
In phosphors, the role of Cerium is not as the emitting atom, but as a "sensitizer."
Cerium is also used in a variety of ceramics, including dental compositions and as a phase stabilizer in zirconia-based products.
Ceria plays several catalytic roles. In catalytic converters it acts as a stabilizer for the high surface area Alumina, as a promoter of the water-gas shift reaction, as an Oxygen storage component and as an enhancer of the NOX reduction capability of Rhodium. Cerium is added to the dominant catalyst for the production of styrene from methylbenzene to improve styrene formation. It is used in FCC catalysts containing zeolites to provide both catalytic reactivity in the reactor and thermal stability in the regenerator.
In steel manufacturing, it is used to remove free Oxygen and Sulfur by forming stable Oxysulfides and by tying up undesirable trace elements, such as Lead and Antimony.

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