Thermogravimetric investigation of scandium,yttrium and the rare earth metal diliturates

Thermolysis curves for scandium, yttrium, lanthanum, cerium(III), neodymium, samarium, gadolinium, dysprosium and erbium diliturates are described, Scandium diliturate forms a 15-hydrate which dehydrates in 3 steps. The other diliturates all form 12-hydrates which dehydrate smoothly. All of the anhydrous diliturates are thermally stable to about 240°.Solubilities in water for scandium, yttrium, lanthanum, cerium(lll), neodymium, samarium. gadolinium, dysprosium and erbium diliturates are given. Scandium diliturate is the most soluble and neodymium diliturate the least soluble. Solubilities of rare earth diliturates not investigated can be predicted approximately.Methods for thermogravimetric determination of yttrium, lanthanum, neodymium, samarium, gadolinium, dyprosium, and erbium as the diliturates have been developed. The precipitates are quite dense, easily handled and filterable. Weighing as the diliturate salts gives these determinations a very favorable gravimetric factor.     

The thermolysis of the neocupferron chelates of yttrium and the rare earth elements

The thermolosis curves of the neocupferron chelates of yttnum, lanthanum, cerium(III), cerium(IV). praseodymium, neodymium, samarium and gadolinuim were determined. It was found that the ehelates were stable up to 8o°, with the oxide levels being reached at 460–750°.     

Dynamic ion-exchange chromatography with post-column reaction detection for the determination of the rare earth elements in monazites

Summary Separation and determination of lanthanum, cerium, praseodymium, neodymium and samarium in monazites have been achieved by dynamic ion-exchange chromatography. The ore samples are decomposed by sulfuric acid and the rare earths are separated in a group as oxalates. The rare earth elements are then separated from each other on a column of bonded phase silica by gradient elution with 0.05 to 0.5 M lactic acid (pH 3.5) in the presence of 0.01 M sodium 1-octanesulfonate. Post-column reaction with Arsenazo III is used for detection and quantification of the individual rare earth elements. Results are quoted for lanthanum, cerium, praseodymium, neodymium and samarium in monazites. Detection limit is 1 μg ml⁻¹ with a S/N ratio of 3. The separation is complete within 27 min valley to valley resolution. Precision of better than 1% can usually be obtained.     

Complexes of d and f Metals with 2-Methyl-3-hydroxy(amino)pyrido[1,2-a]pyrimidine-4-one. Crystal Structure of 2-Methyl-3-hydroxypyrido[1,2-a]pyrimidine-4-one

Six complexes of scandium(III), lanthanum(III), praseodymium(III), and copper(II) chlorides with 2-methyl-3-hydroxypyrido[1,2-a]pyrimidine-4-one (HL¹) and 2-methyl-3-aminopyrido[1,2-a]pyrimidine-4-one (L²), as well as hydrochloride and hydronitrate L², were isolated. The crystal and molecular structures of HL¹ were determined. HL¹ in CCl₄ solution was shown (IR data) to occur as two forms, namely, neutral and zwitterionic forms. The structures for the complexes isolated were proposed.     

Synergic liquid-liquid extraction studies of neodymium and praseodymium with mixtures of tributyl phosphate and Aliquat-336 in nitrate media

Extraction studies of neodymium and praseodymium with mixtures of tributyl phosphate and Aliquat-336 in xylene have been carried out. From 3.0M aqueous ammonium nitrate solutions, negatively charged complexes of neodymium and praseodymium were extracted with Aliquat-336 in the presence of tributyl phosphate into the organic phase. The synergic extracted species observed was M(NO₃) ₄ ^– L⁺·TBP. The synergic extraction of lanthanide elements in nitrate media increases from lanthanum to lutetium.     

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.     

Synthesis,spectroscopic studies,and crystal structure of 2,6-diacetylpyridinediphenylhydrazone perchlorate and its complexing ability toward the lanthanides

2,6-diacetylpyridinediphenylhydrazone perchlorate was prepared and characterized by spectroscopic (IR, ESI–MS, UV–Vis, ¹H NMR) and analytical data and its crystal structure was determined by single X-ray analysis. The lanthanum(III), praseodymium(III), and neodymium(III) perchlorate complexes of 2,6-diacetylpyridinediphenylhydrazone were prepared in a direct reaction of the ligand with appropriate metal perchlorates. The spectroscopic and analytical data indicate 1:2 metal to ligand stoichiometry. In all the complexes the hydrazones act as monodeprotonated terdentate NNN donor chelators. The same lanthanum(III) complex was also obtained in a one-step condensation reaction between 2,6-diacetylpyridine and phenylhydrazine in the presence of lanthanum(III) perchlorate.     

Separation and microdetermination of rare earth metals with N-phenylbenzohydroxamic acid and Xylenol Orange

A simple, sensitive and selective method for solvent extraction and spectrophotometric determination of lanthanum(III), praseodymium(III), neodymium(III) and samarium(III) is described. The rare earth metals are extractable into chloroform solution of N-phenylbenzohydroxamic acid (PBHA) at pH9–10. Various parameters are studied to optimize the extraction conditions. Stoichiometry of the complexes and the effect of various ions is discussed. The molar absorptivity is found to increase from 65,000 to 93,000 1·mol^–1· cm^–1 with the increase in atomic number of the rare earths. The stability constants of the complexes, separation factors and pH_{5 0} are discussed.     

Oxygen isotopic exchange between carbon dioxide and some molybdates or rare-earth elements

The oxygen exchange between C¹⁸O₂ and the normal molybdates of cerium, lanthanum, praseodymium and neodymium has been studied within the temperature interval 300–500°C. The specific rates and activation energies of exchange for these molybdates were found to have similar values. The reactivity of oxygen in the molybdates studied was shown to be close to the reactivity of oxygen in MoO₃     

Molten nitrate eutectics: The reaction of four lanthanide chlorides

The reactions of lanthanum(III), cerium(III), praseodymium(III) and europium(III) chlorides have been studied in the molten lithium nitrate-potassium nitrate and sodium nitrate-potassium nitrate eutectics. The ultimate reaction products have been shown to be oxides (La₂O₃, CeO₂, Pr₆O₁₁ and Eu₂O₃, respectively) which increased the rate of decomposition of the melts, while in three cases an intermediate oxide nitrate was formed (LaONO₃, PrONO₃ and EuONO₃). The temperatures and stoichiometries of the reactions have been established.     

Synthesis and spectral characterization of lanthanide complexes with sulfamethoxazole and their antibacterial activity

A series of nonelectrolytic lanthanide(III) complexes, [ML₂Cl₃]·2H₂O, where M is lanthanum(III), praseodymium(III), neodymium(III), samarium(III), gadolinium(III), terbium(III), dysprosium(III), and yttrium(III), containing sulfamethoxazole ligand (L) are prepared. The structure and bonding of the ligand are studied by elemental analysis, magnetic susceptibility measurements, IR, ¹HNMR, TG/DTA, X-ray diffraction studies, and electronic spectra of the complexes. The stereochemistry around the metal ions is a monocapped trigonal prism in which four of the coordination sites are occupied by two each from two chelating ligands, sulfonyl oxygen, and nitrogen of the amide group and the remaining three positions are occupied by three chlorines. The ligand and the new complexes were tested in vitro to evaluate their activity against the bacteria Escherichia coli and Staphylococcus aureus. The text was submitted by the authors in English.     

A thermal study of some lanthanide trifluoromethyl sulfonates

Lanthanide trifluoromethyl sulfonates, M(SO₃CF₃)₃ · 9H₂O, have been prepared and characterized by analysis, optical properties and thermal behaviour. Dehydration proceeded in two steps for the lanthanum, cerium, praseodymium and neodymium salts and in three steps for other members of the lanthanide series. Thermal decomposition to lanthanide fluoride, carbonyl fluoride and sulfur dioxide occurred at temperatures greater than 400°C. This decomposition has been shown to be a two step process.     

可变误差多面体法同时测定镧及其它轻稀土含量

报导了以化学性质极其相似的La、Ce、Pr、Nd、Sm为分析对象, 采用五个已知组成的标样, 通过全选主元的Gauss消去法求得单组分的吸光常数。据此再用可变误差多面体法求解样品中各组分的浓度, 实践证明, 此法不仅减小了实验误差和手工计算时间,而且考虑了组分间的相互作用, 能获得比较准确的结果, 可变误差多面体法也是解决这类问题更为合适的方法。     

Catalytic activity of some organolanthanoid derivatives in styrene and propene polymerization

Organolanthanoids of several classes were examined as potential styrene and propene polymerization catalysts. They are: molecular hydrides of divalent lanthanoids (samarium, europium, ytterbium); naphthalene and stilbene complexes of neodymium(III), samarium(II), europium(II), ytterbium(II), lutetium(III); amides and alkoxides (including heterobifunctional derivatives) of praseodymium(III), neodymium(III), samarium(II), europium(II), thulium(III), ytterbium(II, III); thiolate of samarium(III); phenyl and phenylethinyl derivatives of europium(II), thulium(III), ytterbium(II); methylytterbium cluster Yb₈ (μ‐CH₃)₁₄(μ‐CH₂)(THF)₆; heterobimetallic samarium(II), ytterbium(II, III) complexes; diazabutadiene ytterbium(III) derivatives; metallic praseodymium and ytterbium, activated by iodine. The highest activity in styrene polymerization revealed hydrides, naphthalene and stilbene complexes of samarium(II), europium(II) and ytterbium(II). In the propene polymerization only [(η⁵‐C₅H₄)CH₂CH­(CH₂OBu)(η¹‐O)]YbMe(THF) displayed noticeable activity.Copyright © 2001 John Wiley & Sons, Ltd.     

Key Experimental Results of the PYROSMANI Project

The presented key results were obtained in the course of experiments carried out within the PYROSMANI (PYROchemical processes Study for Minor ActiNIdes recycling in molten salt chlorides and fluorides) Project supported by Rosatom. The individual and joint solubility of UF₄, PuF₃ and CeF₃ in ternary LiF–NaF–KF and LiF- ThF₄-UF₄ melts was measured by method of isothermal saturation for the temperature range 550-800°C. The solubility measurement technique based on isothermal saturation was verified in LiF–NaF–KF eutectics for praseodymium trifluoride by the reflectance spectroscopy. The process under investigation was the extraction of lanthanum, neodymium, europium and samarium trifluorides from 73LiF-27BeF₂ melt (mole %) into liquid bismuth at 600-610°C. There were defined temperature dependences of kinematic viscosity and melting temperatures for molten 46.5LiF–11.5NaF–42KF; 73LiF-27BeF₂; 85LiF-15AlF₃ and 43.5LiF–24.3NaF–32.2UF₄ salt mixtures from liquidus temperature to 840°C.     

Contributions to the basic problems of complexometry--XXIII: determination of thorium, scandium and some lanthanides in the presence of each other

A new method is described for the determination of thorium, scandium, and the sum of light lanthanides, in the presence of each other. The method is based on the titration of thorium plus scandium with DCTA (1,2-diaminocyclohexanetetra-acetic acid) at pH 2.5-3.5, with Xylenol Orange as indicator. After addition of TTHA (triethylenetetraminehexa-acetic acid) the thorium-DCTA complex is converted into the thorium-TTHA complex according to the equation Th-DCTA + TTHA = TH-TTHA + DCTA. Simultaneously, free lanthanum, cerium, praseodymium and neodymium react with TTHA. The excess of TTHA and the liberated DCTA are then determined by titrations with zinc and with lanthanum solutions according to the equations DCTA + TTHA + 3Zn = Zn-DCTA + Zn(2)-TTHA and DCTA + TTHA + 2La = La-DCTA + La-TTHA. From the results, the amounts of thorium and scandium, and the sum of the lanthanide concentrations, can easily be calculated. Further possibilities, e.g., determination of heavier lanthanides, are briefly discussed.     

On the solubility of lanthanum oxide in molten alkali fluorides

The solubilities of lanthanum oxide in LiF, NaF, KF and eutectic melt LiF-NaF-KF (46.5 mole% LiF; 11.5 mole% NaF and 42.0 mole% KF) were measured in order to find the suitable electrolyte for electrodeposition of lanthanum. Solidus-liquidus lines were obtained by the method of thermal analysis. The solubility of lanthanum oxide in alkali fluorides is rather low and decreases in the order LiF>NaF>KF. It was found that lanthanum oxide reacts with the components of the melt. LaOF and alkali metal oxide are formed during dissolution of La₂O₃ in the melt.     

The determination of rare earth alloying additives in special steels by neutron activation analysis

A procedure for neutron-activation analysis of cerium, lanthanum, praseodymium and neodymium, tested on more than thirty samples of steels, is described. After irradiation for 20 hrs with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹ the steel samples were dissolved in aqua regia and extraction separation of iron from 6N HCl by ether was employed. The REE were separated as a group by precipitation as fluorides and hydroxydes. The individual rare-earth elements were separated from each other using a KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutirate as eluant. The separated samples were counted on a NaI(T1) γ-spectrometer.     

The rare earths a polarographic study

From a study of the polarograms of chlorides of lanthanum, praseodymium, neodymium, samarium, gadolinium, dysprosium and yttrium in 0.IN lithium chloride together with 0.01% gelatin as maximum suppressor, it has been shown that the reduction proceeds in two stages. M⁺³ + e ? M⁺² and M⁺² + 2e ? MIn the case of the less basic elements, anomalies in the heights of the second steps have been observed and these anomalies have been qualitatively explained on the basis of disturbing electrode reactions. The half-wave potentials for each step have been listed.Gelatin has not been found to be very efficient as a suppressor of maxima. In some cases a maximum is in evidence though partially.     

Reindarstellung von Lanthan- und Praseodym-Ammoniumdoppelnitraten durch fraktionierte Kristallisation in großem Maßstab

Summary Lanthanum ammonium nitrate of purity 97%, containing 34.1 kgRE ₂O₃, was crystallized fractionally and yielded 32.5 kg oxide of purity better than 99.9% (the larger part was 99.99% pure). Out of mixtures with 66% Pr there resulted praseodymium ammonium nitrate containing 13.45 kg oxide of purity better than 99.5%. The effective separation factors are discussed, showing a better efficiency of the ammonium than of the magnesium double nitrates for the separation of praseodymium and lanthanum.