Yttrium determination

Percent Yttrium determined by microprobe analysis as function of position on MOR bar surface, on a straight line intersecting the joint plane. 

The amounts of yttrium, determined by ICP-OES, deposited at different current densities for duration time fixed at 900 s, show that local rise in pH responsible for precipitation is effective even for low current densities (Fig. 15.1). The deposited yttrium content increases with current density and reaches a maximum at high current density (Ijl = 0.8 and 1 mA.cm ) when a strong H2 bubbling is observed. After drying for a few minutes in laboratory air, the deposits obtained at low current density (Ijl = 0.2 and 0.4 mA.cm ) are... 

PAM,. spectropliotoniciric dctcrniination of vanadium photometric dctenniiiation of niobium in the presence of trietlianolamine spectrophotomelric determination of bismuth in the presence of 1,3-diphenylguanidinc spectrophotometric determination of yttrium in the presence of Ttephiramine formation constants of mmplexes with Hoflll) measured... 

For elimination of intramolecular energy losses, we have synthesized ligands with high hydrophobisity - perfluoro-P-diketones R -CO-CH -CO-R, (R = CgF j or CgF R = phenyl or a-thienyl), that without second ligand eliminate completely water molecules from the inner coordination sphere. These ligands we have used in analysis at determination of Sm, Eu, Nd, Yb microamounts in high-purity lanthanide and yttrium oxides. 

In addition to meeting the foregoing requirements, a good internal standard will be easy to add uniformly and precisely, and (preferably) no appreciable amount of the element St (free or combined) will be present in the sample before the addition. Cope29 provides an excellent illustration of these points. He found that yttrium nitrate dissolved in ethyl alcohol could be added to a powdered uranium mineral in a mortar, whereupon grinding immediately to dryness dispersed the internal standard (yttrium) so uniformly that uranium could be satisfactorily determined in certain minerals. But the mineral euxenite is an exception, for it contains both yttrium and uranium, and this complicates the uranium determination with yttrium as internal standard. 

Group IY is by all odds the most diverse and the most interesting of the four categories. Because the matrix is variable and often unknown, an internal standard is almost obligatory for all but the crudest exploratory work. The determination of uranium by use of yttrium (Cope, 7.12) and the determination of molybdenum with tungsten as a built-in standard (7.14) belong in Group IV. 

A circular TLC spectrophotometric method for the determination of lanthanum and yttrium at concentration level of 0.01 to 1.0% in molybdenum-based alloys has also been developed. It involves the separation of lanthanum and yttrium on cellulose layers impregnated with 0.2-Mtrioctylamine using aqueous HCl as developer, extraction from sorbent layer, and determination by spectrophotometry [69]. 

Assigning oxidation states of —2 to oxygen, + 3 to yttrium and + 2 to barium, one would obtain an oxidation state 7/3 for copper when jc = 0. The non-integer oxidation state of copper is interpreted as if 2/3 of the ions are present as Cu2+ and 1/3 as Cu3 +. This mixed-valent composition seems to be determinant for the occurrence of superconductivity. In fact, as noted in Table 1, all the superconducting ceramic oxides contain Cu in a non-stoichiometric composition. 

EXAMPLE 1.7 The fluorescence lifetime measured from the metastable state Ej/2 ofNd + ions in the laser crystal yttrium aluminum borate (YAl3(B03)4) is 56 lus. If the quantum efficiency from this state is 0.26, determine the radiative lifetime and the radiative and nonradiative rates. 

The yttrium aluminum garnet crystal, Y3 AI5O12, doped withNd + ions, is a well-known solid state laser material (abbreviated to Nd YAG). If the fluorescence lifetime of the main laser emission is 230 /rs and the quantum efficiency of the corresponding emitting level is 0.9, determine (a) the radiative lifetime and... 

Yttrium aluminum borate, YAlj (603)4 (abbreviated to YAB), is a nonlinear crystal that is very attractive for laser applications when doped with rare earth ions (Jaque et al, 2003). Figure 7.9 shows the low-temperature emission spectrum of Sm + ions in this crystal. The use of the Dieke diagram (see Figure 6.1) allows to assign this spectrum to the " Gs/2 Hg/2 transitions. The polarization character of these emission bands, which can be clearly appreciated in Figure 7.9, is related to the D3 local symmetry of the Y + lattice ions, in which the Sm + ions are incorporated. The purpose of this example is to use group theory in order to determine the Stark energy-level structure responsible for this spectrum. 

The yttrium monocarbide molecule was only recently observed under high resolution by Simard et al. (37) using Jet-cooled optical spectroscopy. The ground electronic state was determined to be an 0=5/2 state, which was consistent with the ab initio calculations of Shim et al. (38) who predicted a 11 ground state for YC in CASSCF calculations. The experimental work of Simard et al. yielded estimates for both the bond length and harmonic frequency of YC. In addition to their CASSCF calculations. Shim et al. (38) also reported results from mass spectrometric equilibrium experiments, which resulted in a bond dissociation energy of Do = 99.0 3.3 kcal/mol. The results from the present work are shown in Table I. An open-shell coupled cluster singles and doubles... 

The stability constants of yttrium tartrates have been determined and a mixed copper-yttrium tartaric (T) acid species, Y2CuT3H q unknown), was detected. ... 

The measurement of stability constants of complexes of yttrium, lanthanide, and actinide ions with oxalate, citrate, edta, and 1,2-diaminocyclohexanetetra-acetate ligands has revealed that there is a slight increase in the stability of complexes of the /-electron elements, relative to the others. A series of citric acid (H cit) complexes of the lanthanides have been investigated by ion-exchange methods and the species [Ln(H2cit)]", [Ln(H2cit)2] , [Ln-(Hcit)], and [Ln(Hcit))2] were detected. Simple and mixed complexes of dl- and jeso-tartaric acid have been obtained with La " and Nd ions, and the stability constants of lactate, pyruvate, and x-alaninate complexes of Eu and Am " in water have been determined. 

ICP-AES was validated for the simultaneous determination of Al, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Li, Mn, Ni, Pb, Se, Sr and Zn in human serum in a clinical laboratory. The samples underwent digestion and yttrium was used as an internal standard. The LOD were as follows 0.002-0.003 (xM for Ba, Cd, Mn and Sr 0.014-0.07 (xM for Be, Co, Cr, Cu, Fe, Li, Ni, Pb and Zn and 0.2-0.9 (xM for Al, B and Se. The concentrations of Al, Be and Co in human serum were found to be above the LOD, while those of Cd, Cr, Ni and Pb were below the LOQ however, in case of acute intoxication with the latter elements the method is valid . Matrix effects were evaluated for ICP-AES analysis using solution nebulization and laser ablation (LA) techniques. The main matrix-related interferences stem from elements with a low second ionization potential however, these are drastically reduced when pure He is used as carrier gas. This points to Ar (the usual carrier) participation in the interference mechanism, probably by interacting with doubly charged species. ... 

Neutral lanthanide complexes are convenient models for the cationic zirconocene systems and avoid complications due to the presence of counteranions and the limited solubility of ionic compounds. Dynamic NMR studies on yttrium complexes 44-46 has allowed the determination of the alkene binding enthalpy, the activation enthalpy of alkene dissociation, and the relative rates of dissociation and alkyl site exchange (site epimerisation) (Scheme 8.20). Compared to the Zr... 

Korte N, Kollenbach M, Donivan S. 1983. The determination of uranium, thorium, yttrium, zirconium and hafnium in zircon. Analyt Chim Acta 146 267-270. 

The element was discovered in 1794 by the Swedish chemist Gadolin. He named it after the small town Ytterby in Sweden where the mineral containing yttria was found. Mosander in 1843 determined that the yttria consisted of three oxides yttria, erbia, and terbia. Yttrium occurs in all rare earths. It is recovered commercially from monazite sand, which contains about 3% yttrium. It also is found in bastnasite in smaller amounts of about 0.2%. Abundance of yttrium in earth s crust is estimated to be 33 mg/kg. The metal has been detected in moon rocks. 

In subsequent studies, methyl vinyl ketone (2.0 mmole) was chosen as the dienophile so as to determine the combined effect of the ionic liquid (2 mL) and the Lewis acids (0.2 and 0.5 wt%) upon the yield and selectivity. Without the Lewis acid catalyst, this system demonstrated a 52% conversion of the cyclopentadiene (2.2 mmol) in 1 h with the endojexo selectivity being 85/15. The cerium triflate-catalyzed reaction was quantitative in 5 min and the endo. exo selectivity was very good for this experiment as well (94 6, endo. exo). Also with the scandium or yttrium salts tested, reactions came to completion in a short time with high stereo-selection. Cerium, scandium and yttrium triflates are strong Lewis acids known to be quite effective catalysts in the cycloadditions of cyclopentadiene with acyclic aldehydes, ketones, quinones and cycloalkenones. These compounds are expected to act as strong Lewis acids because of their hard character and the electron-withdrawing triflate group. On the other hand, reaction times of 1 hour were required for... 

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