Erbium determination

We have briefly encountered the solid-state fluoride electrode, which has a fully nemstian response down to c. 10 mol dm . The fluoride electrode is iiiunersed in a test solution of fluoride ion (usually aqueous), and the emf is then determined. At its heart is a single crystal of lanthanum fluoride doped with erbium fluoride, (see Figure 3.10). Like the pH electrode, a full fluoride electrode also contains a small reference electrode, meaning that a fluoride electrode is in reality a cell. The fluoride electrode does not suffer from interference from CP, so an AgCl Ag reference is the normal choice owing to its convenience and compact size. 

By isostructural substitution, using the Er3+—Y3+ pair, the structures of chloride and nitrate complexes of Er3+ in DMSO solution have been determined and can be compared with the structures of corresponding complexes in aqueous solution (37). The deconvoluted RDFs for 1 M erbium(III) nitrate and chloride solutions, calculated from difference curves, are shown in Fig. 27. The structures for the complexes were derived from these RDFs and the final parameter values were obtained by least-squares refinements using the intensity difference curves. The bonding of the ligands and a comparison between experimental values and values calculated for the derived models are shown in Fig. 27. 

Erbium ions in fluoride glasses possess several radiative transitions from the violet to the mid-IR (3.45 pm) as shown in Fig. 10. Their spectroscopic parameters such as radiative lifetimes and branching ratios were determined for several types of glasses based on zirconium, indium, aluminum or even zinc fluoride [31,98-100]. 

For example, the isotopic composition and the atomic weight of neodyminm," dysprosium and erbium have been determined using synthetic mixtnres prepared gravimetrically from highly enriched isotopes of neodymium in the form of oxides of weU defined pnrity by TIMS. No natnral isotopic variation was found in terrestrial neodymium, dysprosium or erbium samples. These isotopic compositions of Dy and Er measnred by TIMS are accepted as the best measurements from a single terrestrial source as noted in the table of isotopic composition of elements, 2001. °... 

The crystal standard of (7r-cp)2Ti(NCO)2 has been determined and confirms that, in the solid state, the cyanate group is here N-bonded it was only in the last stages of the analysis that the 0-bonded alternative could be finally eliminated (i). Hexa-iV-cyanato complexes of ytterbium, erbium, and neodymium have been reported as quaternary onium salts (16) and reference made to the series of tetraethylammonium salts of [Ln(NCO)0] (Ln = Eu-Yb) (22) these results extend Table XLII. The ESR spectra of series of complexes CuL2(NCO)2 (L = an, or substituted an) have been interpreted to show Cu— N(CO)—Cu bridges with no indication of any Cu-0 interactions (19). The ESCA spectra of [M(NCO)4] (M = Mn, Co, Zn) have been recorded (12). 

Lanthanide (III) Oxides. The lanthanide(III) oxides will be used to illustrate the present breadth of our most extensive knowledge of the chemical thermodynamics of lanthanide compounds. Cryogenic heat capacities of hexagonal (III) lanthanum, neodymium, and samarium oxides, together with those of cubic (III) oxides of gadolinium, dysprosium, holmium, erbium, and ytterbium, have been reported (90, 91, 195). In addition, those of thulium, lutetium, and a composition approaching that of cerium (III) oxide have also been determined, and five well-characterized compositions between PrOi.714 and PrOi.833 are currently under study (J93). 

Since no accurate vapor pressure data are available for the erbium and thulium hahdes, the molar absorptivities were determined directly from a weighed amount of the respective rare-earth halides. Good results could be obtained from this method if the respective halogen, bromine, or iodine were added to the cell such that its pressure at 1000°C. was 1 atm. This procedure greatly reduced the reaction of the rare-earth... 

Six naturally occurring stable isotopes of erbium are known. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element s name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. The naturally occurring isotopes of erbium are erbium-162, erbium-164, erbium-166, erbium-167, erbium-168, and erbium-170. 

The currently determined X-ray structure of a tetranuclear heterobimetallic isopropoxide, ErAI3(0-/-Pr),2 (Fig. 25) (251), possesses a noncrystallographi-cally imposed C3 point symmetry, with the rotation axis perpendicular to the plane through the aluminum atoms. The coordination geometry around the erbium atom is a distorted trigonal prism, in contrast to the ideal octahedral coordination for the central aluminum atom in the structure of A1A13(0-/-Pr),2 (see Fig. 2). 

Three equivalents of 1,3-diphenyltriazene react with 1 equiv. of the tris(cyclopentadienyl)lanthanides in the presence of pyridine to afford tris(l,3-diphenyltriazenido)(pyridine) lanthanide complexes. Single crystal X-ray determinations of bis(cyclopentadienyl)(l,3-diphenyltriazenido)(4-/-butylpyridine)erbium revealed a monomeric species with two cyclopentadienyl ligands, one bidentate 1,3-diphenyltriazenido ligand, and one 4-/-butylpyridine... 

Trivalent cations of REE in aqueous solutions, acidified with HCl, HNO3, or HCIO4, absorb in the UV or VIS. The absorption bands are narrow, with sharp, non-overlapping peaks, but the molar absorptivities are rather small (1-10), and individual species of REE can be determined at concentrations of the order of 1 mg/ml [120]. Higher sensitivities are obtained after the ions have been converted into EDTA complexes [121]. The determination can be made more selective and sensitive by the use of the derivative spectrophotometry techniques [122-124]. Neodymium and erbium have been determined in the mixtures of REE by the derivative spectrophotometry technique using ferron and diethylamine [ 125]. 

The lanthanide or rare earth elements (atomic numbers 57 through 71) typically add electrons to the 4f orbitals as the atomic number increases, but lanthanum (4f°) is usually considered a lanthanide. Scandium and yttrium are also chemically similar to lanthanides. Lanthanide chemistry is typically that of + 3 cations, and as the atomic number increases, there is a decrease in radius for each lanthanide, known as the lanthanide contraction. Because bonding within the lanthanide series is usually predominantly ionic, the lanthanide contraction often determines the differences in properties of lanthanide compounds and ions. Lanthanide compounds often have high coordination numbers between 6 and 12. see also Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Lutetium Praseodymium Promethium Samarium Terbium Thulium Ytterbium. 

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