离子色谱法测定一些金属材料中镧、铈、镨,钕

本文叙述了用离子色谱法测定稀土元素,选用0.002mol/l乙二胺—0.006mol/l柠檬酸为淋洗液,用本所改装的光度检测器,在无梯度淋洗装置条件下,不需预分离共存元素,可测定多种金属材料中镧、铈、镨和钕。     

ICP-MS法测定鼠脊髓液中超痕量镧、铈、镨和钕

采用ＮＨＯ３＋ＨＣｌＯ４混合酸溶样,感耦等离子体－质谱（ＩＣＰ－ＭＳ）直接测定鼠脊髓液中Ｌａ、Ｃｅ、Ｐｒ和Ｎｄ,对等离子体质谱测定条件进行了最佳化选择。选用铼（Ｒｅ）内标可补偿基体影响和仪器漂移。方法检出限为７．６－２０．３ｎｇ／Ｌ,加标试验回收率为９４％－１０２％,相对标准偏差（ＲＳＤ）为２．１％－３．７％。     

The spectrochemical determination of La,Ce, Pr,Nd, Sm,Gd and Dy in sodium rare earth sulphates

A DC-arc spectrochemical procedure is described for the analysis of La, Ce, Pr, Nd, Sm, Gd and Dy in sodium rare earth sulphates derived from monazites.     

X-ray fluorescence determination of La,Ce, Pr,Nd, and Sm in industrial sediments of calcium sulfate using linear regression analysis

Industrial sediments of calcium sulfate semihydrate obtained from industrial extraction phosphoric acid and containing 0.3–4.5 wt % of impurity La?Sm are investigated by energy-dispersive X-ray fluorescence analysis (XRFA) and a procedure for the quantitative determination of cerium lanthanides in the sediments is developed. The use of linear regression analysis of X-ray fluorescence spectra of multielement industrial samples and models of individual compounds NaLn(SO₄)₂ · H₂O (cp grade) allowed us to resolve overlaps of spectral L-series lines for La–Sm, eliminate the background, and perform the regression assessment of line intensities of these elements. On this basis, we developed a procedure for the determination of La, Ce, Pr, Nd, and Sm in CaSO₄ · 0.5H₂O sediments with limits of detection (wt %): 0.022, 0.013, 0.011, 0.008, and 0.008, respectively. In concentration ranges (wt %) La (0.05–0.99), Ce (0.1–4.9), Pr (0.005–0.49), Nd (0.02–0.99), and Sm (0.005-0.19), the relative standard deviation RSD (n = 10, P = 0.95) was 18?27, 9?18, 20?31, 17?26, and 19?31%, respectively. A comparison of the results of XRFA with the data of inductively coupled plasma mass spectrometry confirms the accuracy of the results obtained according to OST (Branch Standard) 41-08-221-04.     

INAA of Zr,La, Ce and Nd in geological samples in the presence of different uranium concentratios

Rock samples which contain relatively high concentrations of uranium may create problems of interference produced by fission products, when instrumental neutron activation analysis is used. The isotopes⁹⁵Zr,¹⁴⁰La,¹⁴¹Ce, 143Ce and 147Nd, which are commonly used in the neutron activation analysis of the corresponding elements, are also produced as fission products of²³⁵U. For each of these radioisotopes, a contribution factor is calculated theoretically and meaured experimentally using geological samples with different uranium contents.     

Flame-ion chemistry of the lanthanide metals Ce,Pr and Nd

A pair of premixed, H₂O₂Ar flames of fuel-rich (FR) and fuel-lean (FL) composition, both at atmospheric pressure and 2425 K, were doped with about 10⁻⁶ mol fraction of the lanthanide metals La, Ce, Pr and Nd; from a previous study, La was used as a benchmark. The metals produce solid particles in the flames and gaseous metallic species. The latter include metallic atoms A near the flame reaction zone, but only the monoxide AO, the oxide hydroxide OAOH and, in some cases, the dioxide AO₂ further downstream at equilibrium. Metallic ions (< 1% of the total metal) were observed by sampling the flames through a nozzle into a mass spectrometer. All of the observed ions can be represented by four hydrate series: (a) major signals of AO⁺·nH₂O (n = 0–3) for La, Ce, Pr and Nd; (b) small signals of AO₂H⁺·nH₂O (n = 0–2) for Ce, Pr and Nd; (c) still smaller signals of AO₂⁺·nH₂O (n = 0, 1) for Ce, Pr and Nd in the FL flame only; and (d) tiny signals of AOH⁺·nH₂O (n = 0, 1) for Pr and Nd in the FR flame only. The actual structures of some of these ions may not correspond to simple hydrates: e.g. AO⁺·H₂O = A(OH)₂⁺ = protonated OAOH; AO₂H⁺·H₂O = A(OH)₃⁺, etc. Since hydrogen flames contain essentially no natural ionization, a major objective was to consider probable ionization mechanisms for the metals. The primary reactions include both chemi-ionization, and thermal (collisional) ionization of AO whose ionization energy is low (about 5 eV). Some of the ions are formed by secondary ion/molecule reactions including three-body hydration, proton transfer, electron (charge) transfer, H atom abstraction by radicals and oxidation. In addition, the chemical ionization of the metallic species by H₃O⁺ was investigated. The flame-ion chemistry of these metals is discussed in detail.     

Synthesis, identification and thermal decomposition of double sulfates of La, Ce, Pr or Nd with ethanolammonium

On evaporation at room temperature of an aqueous reaction mixture of Ln(III) sulfate and ethanolammonium sulfate in a molar ratio higher than 1∶16, crystal products with a waxy feel were obtained. They were identified by means of the X-ray powder diffraction patterns and it was concluded that they are isostructural. The results of elemental analysis and the mass losses by TG analysis indicated the formation of double sulfates with general formula: (HOCH₂CH₂NH₃)₄Ln₂(SO₄)5·4.5H₂O (Ln=La, Ce, Pr or Nd) Their thermal decompositions in static atmosphere in the temperature range from ambient up to 1173 K took place in a similar way, and mainly Ln₂O₂SO₄ was obtained as final product. The exception was the Ce compound, which decomposed to CeO₂. The double sulfates decomposed in many not well-differentiated steps. From the mass losses occurring during thermal decomposition, the mode of thermal decomposition was presumed. The X-ray powder diffraction patterns of Ln₂O₂SO₄ (Ln=La, Pr and Nd) show that they are also isostructural.     

The removal of Ce,Nd, Pr and La from Er,Dy, Gd,Eu and Sm by Anion exchange

An anion-exchange procedure with 35% 3.5 N nitric acid-65% methanol as eiuant has been developed for the removal of Ce, Nd, Pr and La from Er, Dy, Gd, Eu and Sm, at the trace concentration level.     

Spectrophotometric determination of zirconium, uranium, thorium and rare earths with arsenazo III after extractions with thenoyltrifluoroacetone and tri-n-octylamine

A method is described for the spectrophotometric determination of microgram amounts of zirconium, uranium(VI), thorium and rare earths with Arsenazo III after systematic separation by extraction. First zirconium is extracted into a xylene solution of thenoyltrifluoroacetone (TTA) from about 4M hydrochloric acid. Uranium(VI) is then extracted into a xylene solution of tri-n-octy lamine from about 4M hydrochloric acid. Thorium is next extracted into TTA solution at pH about 1.5, and finally rare earths are extracted into TTA solution at pH about 4.7. Each metal is back-extracted from the organic phase before determination.     

Determination of Ce,Pr, Nd and Sm in High Purity La2O3 by Inductively Coupled Plasma Atomic Emission Spectrometry

Abstract

High purity lanthanum oxide was analysed to determine traces of Ce, Pr, Nd, and Sm by employing inductively coupled plasma atomic emission spectrometry (ICP-AES). Lanthanum oxide was dissolved in nitric acid and the solution was nebulized into the plasma generated by a RF generator (56 MHz; 1.5kW). Analytical lines of Ce, Pr, Nd, and Sm, which were free of interference from the spectral lines of both La and the other rare earths, were scanned on a Jobin-Yvon, Model JY-38 THR-1000 1m-Czerny-Turner monochromator. Standards containing the four analytes (Ce, Pr, Nd, and Sm) in the concentration range 0.01–0.2 μg/ml and La at 2 mg/ml were used for calibration. Detection limits ranged between 6 and 16 ng/ml for the four analytes in aqueous solution.     

Spectrophotometric determination of rare earth elements and thorium with arsenazo

The simultaneous spectrophotometric determination of rare earth elements (lanthanum and gadolinium) and thorium with arsenuzo is described. In 0.05 N nitric acid, thorium alone forms a colored complex with the reagent; at PH 7.2 both thorium and the rare carths form colored complexes. Satisfactory results were obtained with weight ratios of Th/rare earths ranging from 0.2 to 10.     

Spectrophotometric determination of iron with 1,10-phenanthroline in the presence of copper

Summary Cupric ion forms a very stable complex with triethylenetetramine (trien). It has a very weak absorption at 400–460 nm, however, the ferroin shows a very strong absorption at 480–520 nm. The use of trien-tartrate as duel masking agents for copper has been proved to be successful, and is superior to EDTA or citrate-EDTA in the determination of iron with 1,10-phenanthroline. The colour reaction may be accelerated at 60° for 10 min. The new method has been applied to the analysis of U. S. NBS standard solder alloy samples for iron.

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Die spektrophotometrische Bestimmung von Eisen mit 1,10-Phenanthrolin in Gegenwart von Kupfer

Zusammenfassung Kupfer(II)ionen bilden mit Triethylentetramin (Trien) einen sehr beständigen Komplex. Dieser absorbiert sehr schwach bei 400–460 nm, Ferroin hingegen zeigt eine sehr starke Absorption bei 480–520 nm. Die Verwendung von Trien-Tartrat als Maskierungsmittel für Kupfer erwies sich als zielführend und ist für die Eisenbestimmung mit 1,10-Phenanthrolin besser geeignet als EDTA oder Zitrat-EDTA. Die Farbreaktion läßt sich durch Erwärmen auf 60°C für 10 min beschleunigen. Die vorgeschlagene Methode hat sich bei der Analyse von NBS-Standardproben von Lot-Legierungen bewährt.

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On leave from Nanking Institute of Chemical Technology, Nanking, China.     

Spectrophotometric study of the reactions of arsenazo III with alkaline-earth metals

Arsenazo III is used as a spectrophotometric reagent for alkaline-earth metals. The molar absorptivities of the calcium, strontium and barium complexes at 650 nm are 4.40 x 10(4), 4.00 x 10(4) and 3.65 x 10(4) l.mole(-1).cm(-1) respectively. The interference of magnesium is eliminated at pH 5-6. The use of sodium sulphate as masking agent permits the determination of small amounts of calcium, strontium and magnesium in the presence of barium. The alkaline-earth ions can be determined in the presence of each other at pH 4.2 at the 2-10 mug level. Some organic solvents such as dioxan, acetone and ethanol increase the sensitivity and selectivity in acidic medium. The stability constants have been measured and the structure of the complexes is discussed.     

X-Ray fluorescence analysis using the filter paper method for the determination of La,Pr and Nd in solution

The use of radioisotope-induced energy dispersive X-ray fluorescence technique for elemental analysis in solutions by the filter paper method has been investigated. The calibration has been found to be linear over the range studied. Non-uniformity of specimen, the precision and accuracy of the method have been examined. The minimum detectable amounts have also been determined.     

Ternary metal borides [La,Ce,Pr,Nd,Sm] Os4B4 and [Y,La,Ce,Pr,Nd,Sm,Gd,Tb] Ir4B4 with NdCo4B4-type structure

New ternary metal borides with compositionR. E. T ₄B₄ (R. E.=rare earth metal,T=transition metal) have been synthesized within the systems [La,Ce,Pr,Nd,Sm]–Os–B and [Y, La, Ce, Pr, Nd, Sm, Gd, Tb]–Ir–B. All compounds were found to be crystallizing with NdCo₄B₄-type structure. Magnetic measurements (80–300 K,Curie-Weiss behaviour, _p ~ 16K and µ_eff=9.94µ_B for TbIr₄B₄) indicate Y andR. E. elements (except Ce) to be trivalent in these compounds. The crystal chemistry of the isotypic series [Y,R. E.] [Os,Ir]₄B₄ is discussed.

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Ternäre Metallboride. [La,Ce,Pr,Nd,Sm] Os₄B₄ und [Y,La,Ce,Pr,Nd,Sm,Gd,Tb] Ir₄B₄ mit NdCo₄B₄-Struktur

Zusammenfassung Es wurden neue Metallboride der ZusammensetzungR. E. T ₄B₄ (R. E.=Seltenerdmetall,T=Übergangsmetall) innerhalb der Systeme [La,Ce, Pr,Nd,Sm]–Os–B und [Y,La,Ce,Pr,Nd,Sm,Gd,Tb]–Ir–B hergestellt. Alle Verbindungen kristallisieren entsprechend dem NdCo₄B₄-Typ. Magnetische Messungen (80–300K,Curie-Weiss-Verhalten, _p ~ 16K und µ_eff=9.94µ_B für TbIr₄B₄) zeigen an daß Y und dieR. E.-Elemente (ausgenommen Ce) in diesen Verbindungen trivalent sind. Die Kristallchemie der isotypen [Y,R. E.][Os,Ir]₄B₄-Verbindungen wird diskutiert.

     

REAu2In4 (RE = La, Ce, Pr, Nd): polyindides from liquid indium

The series of compounds REAu2In4 (RE = La, Ce, Pr, Nd) crystallize from excess In as rod-shaped single crystals. All members adopt the orthorhombic space group Pnma with a = 18.506(2) A, b = 4.6865(6) A, and c = 7.3414(9) A for LaAu2In4, a = 18.514(3) A, b = 4.6624(8) A, and c = 7.389(1) A for CeAu2In4, a = 18.420(4) A, b = 4.6202(9) A, and c = 7.376(2) A for the Pr analogue, and a = 18.406(2) A, b = 4.6114(5) A, and c = 7.4073(7) A for NdAu2In4. The REAu2In4 series can be regarded as polar intermetallic phases composed of a complex [Au2In4]3- polyanion network in which the rare-earth ions are embedded. The [Au2In4]3- network features In tetramer units, which defines the compounds as polyindides. Magnetic measurements found no magnetic ordering down to 2 K for any of the compounds. In addition, LaAu2In4 was found to be Pauli paramagnetic with a small susceptibility. Ab initio density functional methods were used to carry out electronic structure calculations to explore the bonding, the role of gold, and the contributions of different atoms to the density of states near the Fermi energy. We find that the density of states decreases slowly near Ef and reaches a minimum at about 0.5 eV above Ef.     

Preparation and structure of the light rare-earth copper selenides LnCuSe2 (Ln=La, Ce, Pr, Nd, Sm)

The ternary selenides LnCuSe₂ (Ln=La, Ce, Pr, Nd, Sm) have been synthesized by the reaction at 1173 K of Ln, Cu, and Se in a KBr or KI flux. The compounds, which are isostructural with LaCuS₂, crystallize with four formula units in the space group P2₁/c of the monoclinic system. The structure may be thought of as consisting of layers of CuSe₄ tetrahedra separated by double layers of LnSe₇ monocapped trigonal prisms along the a-axis. Cell constants (Å or deg) at 153 K are: LaCuSe₂, 6.8142(5), 7.5817(6), 7.2052(6), 97.573(1)°; CeCuSe₂, 6.7630(5), 7.5311(6), 7.1650(6), 97.392(1)°; PrCuSe₂, 6.740(1), 7.481(1), 7.141(1), 97.374(2)°; NdCuSe₂, 6.7149(6), 7.4452(7), 7.1192(6), 97.310(1)°; SmCuSe₂, 6.6655(6), 7.3825(7), 7.0724(6), 97.115(1)°. There are no Se-Se bonds in the structure of LnCuSe₂; the formal oxidation states of Ln/Cu/Se are 3+/1+/2−.     

The magnetic and electrical properties of LnCrSe3 (Ln=La,Ce, Pr,Nd)

Magnetic and electrical measurements have been made on single crystals and polycrystalline samples of LnCrSe₃, where Ln is lanthanum, cerium, praseodymium and neodymium. These materials are all antiferromagnetic, but show weak ferromagnetism at lower temperatures. The resistivity and Hall effect show these compounds to be extrinsic semiconductors.