Cerium impurity

The first attempts to record the Bk(IV) solution absorption spectrum were hindered by the presence of cerium impurities (92). The positions of the Bk(IV) absorption bands, superimposed on the strong Ce(IV) bands, suggested the assignment of Sf7 for the electronic configuration of Bk(IV), in agreement with the actinide hypothesis. 

Dederichs PH, Blugel S, Zeller R, Akai H (1984) Ground slates of constrained systems— application to cerium impurities. Phys Rev Lett 53 2512... 

The liquidus and fee to bee transformation data of Vogel and Klose (1954) is the basis for the phase diagram of the lanthanum-eerium system. Their lanthanum was reported to have a purity of 97% (the major impurities were 1.4% Fe, 0.3% eaeh Si and Mg, and 1% miseellaneous) and their eerium a purity of 99.5%. Savitskii and Terekhova (1958) reported data on the liquidus and solidus for this system but did hot include information on the solid state transformations. They claimed a purity of 98.6% for their lanthanum and 97 to 99% for their cerium. Impurity elements were listed but no concentrations were given (Fe and Pr in lanthanum Fe, La, Pr and Nd in cerium). Terekhova (1963) later published a similar phase diagram for this system that seems to be a repetition of that earlier reported by Savitskii and Terekhova. 

Figure 16.8 Schematic representation of a Kondo-type wavefunction for a metal with a cerium impurity. The part given after the sum in parentheses stands for a corresponding (antisymmetric) determinant. In case of a molecular analogue the conduction band of the metal has to be replaced by ligand orbitals...

Greek lanthanein, to lie hidden) Mosander in 1839 extracted a new earth lanthana, from impure cerium nitrate and recognized the new element. 

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. 

An alternative process for opening bastnasite is used ia Chiaa high temperature roastiag with sulfuric acid followed by an aqueous leach produces a solution containing the Ln elements. Ln is then precipitated by addition of sodium chloride as a mixed sulfate. Controlled precipitation of hydroxide can remove impurities and the Ln content is eventually taken up ia HCl. The initial cerium-containing product, oace the heavy metals Sm and beyond have been removed, is a light lanthanide (La, Ce, Pr, and Nd) rare-earth chloride. 

Four years before isolating yttria, Mosander extracted lanthanum oxide as an impurity from cerium nitrate (hence the name from Greek XavOaveiv, to hide), but it was not until 1923 that metallic lanthanum in a relatively pure form was obtained, by electrolysis of fused halides. 

Benzyl bromide, Molecular sieve, 2735 Benzyl chloride, Catalytic impurities, 2738 1,2-Bis(chloromethyl)benzene, 2946 Bis(2-cyanoethyl)amine, 2397 Bis(trimethylsilyl) peroxomonosulfate, 2602 Borane -tetrahydrofuran, 0138 Butylmagnesium chloride, 1641 Calcium acetylide, Methanol, 0585 Calcium chloride, 3923 Cerium, Water, 3961... 

Cerium was the first rare-earth element discovered, and its discovery came in 1803 by Jons Jakob Berzelius in Vienna. Johann Gadohn (1760—1852) also studied some minerals that were different from others known at that time. Because they were different from the common earth elements but were all very similar to each other, he named them rare-earth elements. However, he was unable to separate or identify them. In the 1800s only two rare-earths were known. At that time, they were known as yttria and ceria. Carl Gustav Mosander (1797—1858) and several other scientists attempted to separate the impurities in these two elements. In 1839 Mosander treated cerium nitrate with dilute nitric acid, which yielded a new rare-earth oxide he called lanthanum. Mosander is credited with its discovery. This caused a change in the periodic table because the separation produced two new elements. Mosander s method for separating rare-earths from a common mineral or from each other led other chemists to use... 

It was originally stated that CaCOa activated with manganese cannot be excited by UV radiation, but CaCOa activated with lead, thallium or cerium and manganese shows an orange-red manganese luminescence under UV irradiation at room temperature (Bolden 1952). Nevertheless, in many minerals luminescence of Mn " " has been found with excitation spectra typical for this center without additional bands of Pb or Ce impurities. 

In addition to the foregoing, more or less impure niobates of beryllium, cerium, lanthanum and nickel have been prepared.12... 

L. H. Delmau, P. V. Bonnesen, G. J. Van Berkel and B. A. Moyer, Improved performance of the alkaline-side CSEX process for cerium extraction from alkaline high-level waste obtained by characterization of the effect of surfactant impurities, ORNL/TM-1999/209, ORNL, USA, 1999. 

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