Thorium cerium

Gadolinium is produced from both its ores, monazite and bastnasite. After the initial steps of crushing and beneficiation, rare earths in the form of oxides are attacked by sulfuric or hydrochloric acid. Insoluble rare earth oxides are converted into soluble sulfates or chlorides. When produced from monazite sand, the mixture of sand and sulfuric acid is initially heated at 150°C in cast iron vessels. Exothermic reaction sustains the temperature at about 200 to 250°C. The reaction mixture is cooled and treated with cold water to dissolve rare earth sulfates. The solution is then treated with sodium pyrophosphate to precipitate thorium. Cerium is removed next. Treatment with caustic soda solution fohowed by air drying converts the metal to cerium(lV) hydroxide. Treatment with hydrochloric or nitric acid sol-... 

Berzelius determined the atomic weights of nearly all the elements then known, and was the first chemist to determine them accurately. (19). He referred his atomic weights to oxygen, which, however, he allowed to equal 100, instead of 16 as in our present system. In his little laboratory that looked like a kitchen and in which the sandbath on the stove was never allowed to cool, Berzelius discovered the important elements selenium, silicon, thorium, cerium, and zirconium (18). 

Mixed Hydroxides Thorium Cerium Group Lanthanides... 

Some of the materials that have been examined as catalysts include Pure Platinum, Platinum-Iridium Alloys, Various Compositions of Platinum-Rhodium Alloys, Platinum-Palladium Alloys, Platinum-Ruthenium Alloys, Platinum-Rhenium Alloys, Platinum-Tungsten Alloys, FejOj-M CVI Oj (Braun Oxide), CoO-Bi20j, CoO with AI2O3, Thorium, Cerium, Zinc and Cadmium. 

Use Source of thorium, cerium, and other rare-earth metals and compounds. 

Base metal catalysts have been investigated in fixed-bed and fluidized-bed systems but have not proved to be effective. The following materials have been tried Fe203-Mn203-Bi203 (Braun oxide) CoO-Bi203 and CoO with AI2O3, thorium, cerium, zinc, and cadmium. 

Large deposits of monazite (found on the beaches of Travancore, India and in river sands in Brazil), ahanite (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. 

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. 

Determination of cerium as cerium(IV) iodate and subsequent ignition to cerium(IV) oxide Discussion. Cerium may be determined as cerium(IV) iodate, Ce(I03)4, which is ignited to and weighed as the oxide, Ce02. Thorium (also titanium and zirconium) must, however, be first removed (see Section 11.44) the method is then applicable in the presence of relatively large quantities of lanthanides. Titrimetric methods (see Section 10.104 to Section 10.109) are generally preferred. 

Determination of thorium as sebacate and subsequent ignition to the oxide, ThOa Discussion. This procedure permits of the separation by a single precipitation of thorium from relatively large amounts of the lanthanides (Ce, La, Pr, Nd, Sm, Gd) and also from cerium(IV). 

The main sources of infrared radiation used in spectrophotometers are (1) a nichrome wire wound on a ceramic support, (2) the Nernst glower, which is a filament containing zirconium, thorium and cerium oxides held together by a binder, (3) the Globar, a bonded silicon carbide rod. These are heated electrically to temperatures within the range 1200- 2000 °C when they will glow and produce the infrared radiation approximating to that of a black body. 

In some versions of the periodic table, the lanthanoids begin with cerium (element 58) and the actinoids begin with thorium (element 90). 

The +4 oxidation state is most stable at thorium, which lies beneath cerium. 

Rare Earths are produced primarily from three ores, monazite, xenotime, and bastnasite. Monazite is a phosphate mineral of essentially the cerium subgroup metals and thorium -(light rare Earths, Th) P04. The composition of monazite is reasonably constant throughout the world, with almost 50% of its rare Earth content as cerium and most of the remaining 50% as the other members of the cerium subgroup. Xenotime, like monazite, is a rare Earth orthophosphate but contains up to 63% yttrium oxide and also a markedly higher propor-... 

Iseler, G. W. et al., Int. Conf. Indium Phosphide Relat. Mater., 1992, 266 Reaction of beryllium, copper, manganese, thorium or zirconium is incandescent when heated with phosphorus [1] and that of cerium, lanthanum, neodymium and praseodymium is violent above 400°C [2], Osmium incandesces in phosphorus vapour, and platinum bums vividly below red-heat [3], Red phosphorus shows very variable vapour pressure between batches (not surprising, it is an indeterminate material). This leads to explosions when preparing indium phosphide by reactions involving fusion with phosphorus in a sealed tube [4],... 

Gas-liquid volumetric mass transfer coefficient correlations, for airlift reactors, 15 704-705t Gas lubrication, 15 252 Gas mantles cerium in, 5 689 thorium in, 24 757 Gas masks, 5 832-835 Gas meter provers, liquid displacement, 11 652... 

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 ... 

Calcium, 3922 Cerium, 3961 Chromium, 4222 Cobalt, 4199 Europium, 4292 Hafnium, 4599 Iridium, 4643 Iron, 4388 Lead, 4882 Manganese, 4700 Nickel, 4820 Palladium, 4885 Platinum, 4887 Plutonium, 4888 Rhodium, 4892 Rubidium, 4889 Strontium, 4913 Tantalum, 4914 Technetium, 4915 Thorium, 4917 Titanium, 4919 Tungsten, 4925 Uranium, 4923 Vanadium, 4924 Zinc, 4927 Zirconium, 4928... 

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