Cerium pyrophoricity

Cerium is a component of misch metal, which is extensively used in the manufacture of pyrophoric alloys for cigarette lighters. 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 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. 

At the beginning of the twentieth century, the incandescent mantle, utilising the candoluminescence of a mixture of thorium (95% weight) and cerium oxides was developed. The pyrophoricity of rare-earth metals led to the invention of the lighter flint made through the alloying of iron and mischmetal. Since that time, numerous other appHcations have developed to coincide with the availabiUty of the rare-earth compounds on an industrial scale and having a controlled purity. 

On a fresh surface the metal has a steely lustre but rapidly tarnishes in air as a result of surface formation of oxide and carbonate species. For protection against oxidation the metal is usually stored in a light mineral oil. When made finely divided, eg, on being cut, it can be strongly pyrophoric, and, for this reason is used, as the ferro-alloy mischmetal, in lighter flints and ordnance. Cerium reacts steadily with water, readily dissolves in mineral acids, and is also attacked by alkafl it reacts with most nonmetals on heating. 

Lighter Flints and Getters. Traditionally the item most widely associated with cerium has been the pyrophoric iron-mischmetal (- 0%) alloy for lighter flints, in limited use in the 1990s. Similar low vapor pressure reactive alloys based on cerium, such as Th2Al-MM, can also be used as getters for electronic equipment and vacuum tubes (see Electronic materials Vacuumtechnology). 

Auer-brenner) m. Welsbach burner, -licht) n. Welsbach light, -metall) n. Welsbach metal (pyrophoric cerium alloy), auf) prep, on, upon, in, at about into, to. 

Zirconium. While almost any metal in the finely divided state exhibits pyrophoric properties, a few metals when abraded emit a shower of sparks of sufficient temp to ignite hydrocarbon vapors. Cerium is the best known metal of this kind for commercial purposes, such as gas lighter flints. For military purposes Zr is the most used. It has found applications in HE and armor-piercing incendiary ammo, the lining of shaped-charge rounds, and in incendiary cluster bombs (Ref 7, pp 100-01)... 

Alloys of reactive metals are often more pyrophoric than the parent metals. Examples are alloys of titanium with zirconium thorium with copper, silver or gold uranium with tin, lead or gold magnesium with aluminium hafnium with iron [1], Cerium amalgams and thorium-silver alloys are spontaneously flammable when dry [2], Individually indexed alloys are ... 

Misch metal, an alloy of cerium with other lanthanides is a pyrophoric substance and is used to make gas lighters and ignition devices. Some other applications of the metal or its alloys are in solid state devices rocket propellant compositions as getter in vacuum tubes and as a diluent for plutonium in nuclear fuel. 

Cerium forms with iron a peculiar pyrophoric alloy which, when struck, emits showers of sparks, and which is used somewhat m the manufacture of automatic gas-hghters (28). 

Auer von Welsbach also invented tire automatic gas lighter based on a pyrophoric alloy of iron and cerium, and the osmium-filament electric... 

Cerium Arsenide.—Hirsch2 obtained an alloy of cerium and arsenic by adding the latter in small amounts to cerium melted under a layer of sodium chloride. The reaction appeared to be exothermic and a soft, somewhat pyrophoric alloy remained, which did not decompose on being kept. 

Cerium, Ce at wt 140.13,at No 58 one of the "rare earth elements gray, ductile, maleable metal which tarnishes in moist air d 6.78 mp 645°, bp 1400° sol in dil acids insol in cold w slowly oxidizes in hot w forms numerous alloys salts. It occurs in monazite sand which is an orthophosphate of thorium and rare earths. Ce-Fe pyrophoric alloys are used as sparking flints for lighters, tracer bullets for military signalling. Ce metal is used as component of some rocket proplnts and in alloys for jet engines. Toxicity, fire expln hazards of Ce are discussed in Ref 5- Ce alloy, called Misch Metal Ce 52, Nd 18, Pr 5, Sm 1 other substances(such as La, Ca, Al, C, Si Fe) 24%, has many applications. Mixt of Ce ... 

Cerium metal in the form of small rectangular billets approximately 5 X X 2 in. is used in this preparation. The surfaces of the billets are filed down under a bath of mineral oil to ensure removal of any oxide layer. Caution is advised as the metal may be pyrophoric. The billets are rinsed in carbon tetrachloride to remove the mineral oil and are then transferred to the vacuum glove box. All subsequent handling of the metal is done in the vacuum glove box in a high-purity argon or helium gas environment. 

An interesting stage in the development of primer mixes was the use of pyrophoric metal alloys, first patented in 1936 and improved in 1964. These rare earth alloys, as used in cigarette lighter flints, give a shower of sparks when lightly scraped. A typical pyrophoric alloy is misch metal, which has the following approximate composition cerium 50%, lanthanum 40%, other rare earth elements 3%, and iron 7%. 

A pyrophoric alloy containing cerium, alloyed with iron, substantially as and for the purposes described. ... 

Misch metal is an alloy of about 50% cerium, 25% lanthanum, 15% neodymium and 10% other rare earth metals. Uses include manufacture of a pyrophoric alloy with iron and deoxidizer in metallurgical applications, getter for removal of oxygen from vacuum tubes, high strength magnesium alloys. 

The metals themselves are very electropositive, and are accordingly difficult to prepare. Electrolytic reduction of a fused oxide-fluoride mixture may be used. An alloy containing about 70% cerium and smaller amounts of other rare-earth metals and iron is highly pyrophoric that is, it gives sparks when scratched. This alloy, called Mischmetal, is widely used for cigarette lighters and gas lighters. The use of a mixture of cerium dioxide and thorium dioxide in gas mantles has been mentioned under thorium. 

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