Determination lanthanum

Hydrogen can be in both the octahedral and tetrahedral holes for lanthanum. Determine the percentage of the holes that are filled if the formula is LaH2.76. 

The electron sources used in most sems are thermionic sources in which electrons are emitted from very hot filaments made of either tungsten (W) or lanthanum boride (LaB ). W sources are typically heated to ca 2500—3000 K in order to achieve an adequate electron brightness. LaB sources require lower temperatures to achieve the same brightness, although they need a better vacuum than W sources. Once created, these primary electrons are accelerated to some desired energy with an energy spread (which ultimately determines lateral resolution) on the order of ca 1.5 eV. 

For the bones the preferenee has been given to atomie-absorption speetrometry with flame and graphite furnaee atomization beeause of a strong effeet of ealeium and phosphorous on the analytieal signals of mieroelements under determination in DCP-ai e AFS. It has been shown that In the presenee of lanthanum ehloride no interferenee effeets were observed in flame AAS for Ca, Mg and Sr. FTA AAS has been used to determine Mn and Li in bones. RSD for FAAS determination of Ca, Mg, Sr were 3-6 %, as for Li and Mn -10-12%. 

The possibility of preconcentration of selenium (IV) by coprecipitation with iron (III) hydroxide and lanthanum (III) hydroxide with subsequent determination by flame atomic absorption spectroscopy has been investigated also. The effect of nature and concentration of collector and interfering ions on precision accuracy and reproducibility of analytical signal A has been studied. Application of FefOH) as copreconcentrant leads to small relative error (less than 5%). S, is 0.1-0.2 for 5-100 p.g Se in the sample. Concentration factor is 6. The effect of concentration of hydrochloric acid on precision and accuracy of AAS determination of Se has been studied. The best results were obtained with HCl (1 1). 

The determination of magnesium in potable water is very straightforward very few interferences are encountered when using an acetylene-air flame. The determination of calcium is however more complicated many chemical interferences are encountered in the acetylene-air flame and the use of releasing agents such as strontium chloride, lanthanum chloride, or EDTA is necessary. Using the hotter acetylene-nitrous oxide flame the only significant interference arises from the ionisation of calcium, and under these conditions an ionisation buffer such as potassium chloride is added to the test solutions. 

Glocker and Frohnmayer determined the characteristic constant c for nine elements (Reference 2, Table 4) ranging in atomic numbers from 42 (molybdenum) to 90 (thorium). They proved that identical results could be obtained with the sample in the primary (polychromatic) or in the diffracted (monochromatic) beam. The method was applied with good results to the determination of barium in glass of antimony in a silicate of hafnium in the mineral alvite and of molybdenum, antimony, barium, and lanthanum in a solution of their salts—for example, 5.45% barium was found on 90-minute exposure by the x-ray method for a glass that yielded 5.8% on being analyzed chemically. 

Lanthanum in solution, determination by absorption-edge method, 140 Lead, determination by x-ray emission spectrography, 328 see also Tetraethyllead Tetraethyllead fluid trace analysis by x-ray emission spectrography, 163, 225-227 Light elements, background in determination, 217-219... 

The addition of sodium dodecyl sulfate improves the conventional spectro-photometric method for the determination of fluoride/lanthanum/alizarine flour-ine blue tertiary complex [172]. 

Determine the particle emitted and write the balanced nuclear equation for each of the following nuclear transformations (a) sodium-24 to magnesium-24 (b) l28Sn to 128Sb (c) lanthanum-140 to barium-140 (d) 228Th to 224Ra. 

In situ densitometry has been the most preferred method for quantitative analysis of substances. The important applications of densitometry in inorganic PLC include the determination of boron in water and soil samples [38], N03 and FefCNfg in molasses [56], Se in food and biological samples [28,30], rare earths in lanthanum, glass, and monazite sand [22], Mg in aluminum alloys [57], metallic complexes in ground water and electroplating waste water [58], and the bromate ion in bread [59]. TLC in combination with in situ fluorometry has been used for the isolation and determination of zirconium in bauxite and almnimun alloys [34]. The chromatographic system was silica gel as the stationary phase and butanol + methanol + HCl -H water -n HF (30 15 30 10 7) as the mobile phase. 

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]. 

The lanthanum fluoride electrode (discussed in Section 2.6) is used to determine F ions in neutral and acid media. After the pH-glass electrode, this is the most important of this group of electrodes. 

Fuger, J. and Cunningham, B. B. (1964). Microcalorimetric determination of the enthalpy of formation of the complex ions of trivalent plutonium, americium and lanthanum with EDTA, J. Inorg. Nucl. Chem. 27,1079. 

Bermejo-Barrera et al. [64] studied the use of lanthanum chloride and magnesium nitrate as modifiers for the electrothermal atomic spectrometric determination of p,g/l levels of arsenic in seawater. 

Several recent determinations of the alkali and alkaline earth metals in serum or urine have been reported. Barrett 29) determined potassium, sodium, and calcium in semm by diluting the samples with lanthanum chloride solution. Suttle and Field 3°) used atomic absorption spectroscopy to determine potassium and magnesium in sheep plasma. 

Savory et al. 3S) measured calcium and magnesium directly in protein-free filtrates of serum or urine. Baker et al. 36) found that both trichloroacetic acid and hydrochloric acid suppress calcium absorption and that uniform acid content is therefore required for the determination of calcium. Okuda and Sasamoto37) determined calcium by adjusting solution conditions to 20 — 50 % methanol and 650 mg % lanthanum serum is diluted 21-fold and urine is diluted 10—21 fold to bring the calcium concentration into the optimum range of 1 to 0.5 mg %. 

More recent determinations of serum iron have been reported by Schmidt 57), who simply diluted with lanthanum chloride solution, and by Tavenier and Hellen-doorn58), who deproteinized samples in the latter study, iron in the protein precipitate is analyzed to correct the serum iron level. Uny etal. 59) determined serum iron, using ultrasonic nebulization of the sample to increase the sensitivity. Olson and Hamlin 6°) have determined serum iron and total iron-binding capacity. Proteins are precipitated and iron (III) is released by heating with trichloroacetic acid. 

The formula (5.14) has been applied, for example, by Hutchison and McKay144 to determine the proton coordinates in Nd(III)-doped lanthanum nicotinate dihydrate crystals, and by Balmer et al.101) to localize the charge compensator H+ in Co(II)-doped a-Al203. 

Example Fluoride-ion Electrode In this particular instance the membrane essentially comprises of a single crystal of lanthanum fluoride (LaF3), usually doped with a slight trace of europium (II), Eu2+, so as to initiate the crystal defects required for establishing its electrical conductivity. Therefore, the potential developed at each surface of the membrane is finally determined by the exact status of the equilibrium ... 

Remedy The addition of an excess of strontium (Sr), or lanthanum (La), or thorium (Th) ion remarkably minimizes the interference of P043 ion in the determination of Mg, and Ca by replacing the analyte in the analyte in the compound formed with the respective interfering species. In short, these ions do combine preferentially with P043 ions. 

EXAMPLE 6.2 Determine the nonradiative rates from the following energy levels of different ions in lanthanum chloride 5/2 (Er )fPo (Pr +) and 2 5/2 (Yif+). 

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. 

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