2-Mercapto-benzimidazole as an analytical reagent

Summary Palladium is quantitatively precipitated at aPH 5.0 to 10.1 by 2-mercapto-benzimidazole and the complex, Pd(C₇H₅N₂S)₂, which is found to be diamagnetic, is stable up to a temperature of 447 C. In presence of EDTA and tartrate or citrate and at aPH between 6 and 8, it is separated from alkalis, alkaline earths, Mg, Fe³⁺, Cr, Th, Zr, Ti, UO₂ ²⁺, Be, Ce³⁺, Ce⁴⁺, rare earths, Zn, Mn, Ni, Co, Pb, Bi, As, Sb³⁺, Sn⁴⁺, Tl⁺, Cu²⁺, Cd, Ir⁴⁺, Rh³⁺, Ru³⁺, Os⁴⁺, CrO₄ ^2–, MoO₄ ^2–, WO₄ ^2–, VO₃ ^–, PO₄ ^3– and AsO₄ ^3–. Pb, Ag and Hg²⁺ are kept in solution by potassium iodide while a small amount of Au³⁺ by thiosulphate. The palladium complex is either weighed after drying at 110 C or dissolved in a cyanide solution and determined volumetrically by back titrating the excess cyanide with a standard silver nitrate solution.     

2-Mercapto-benzothiazole as an analytical reagent

Summary The reagent 2-mercapto-benzothiazole quantitatively precipitates palladium at a PH 5.6 to 10.2. The red coloured compound, Pd(C₇H₄NS₂)₂, is diamagnetic and is stable up to a temperature of 388 C. Palladium is separated from alkalis, alkaline earths, Mg, Fe³⁺, Cr, Th, Zr, Ti, UO₂ ²⁺, Be, rare earths, Ce³⁺, Ce⁴⁺, Zn, Mn, Co, Ni, Pb, Bi, Sb³⁺, As³⁺, Sn⁴⁺, Tl+, Cu²⁺, Cd, Ir⁴⁺, Rh³⁺, Ru³⁺, Os⁴⁺, CrO₄ ^2–, MoO₄ ^2–, WO₄ ^2–, VO₃ ^–, PO₄ ^3– and AsO₄ ^3– at apH 6–8 in presence of EDTA and tartaric or citric acid. Besides Pb, Ag and Hg²⁺ are kept in solution with potassium iodide and Au in a limited quantity forms a soluble complex with thiosulphate. The palladium complex is either weighed after drying and determined gravimetrically or dissolved in an excess of cyanide and determined volumetrically by back titrating the latter with silver nitrate.     

Use of organic reagents in inorganic analysis

Summary Thorium and zirconium have been determined gravimetrically with phenylglycine-p-carboxylic acid and zirconium alone with phenylglycine-o-carboxylic acid, almost within the same pH range. Better results are obtained when zirconium is precipitated in acetic acid solution in presence of a little ammonium acetate. A number of foreign ions may be separated from thorium and zirconium with these reagents. Iron and titanium cause heavy interference. The interference caused by iron, may however, be eliminated by adding a little ascorbic acid, before precipitation of the metals. The para acid can also extract thorium from a mixture of cerite earths and from monazite sands.Part V: See Z. anal. Chem. 158, 347 (1957).The author likes to thank Dr. B. N. Bose, Principal of the College and Dr. S. K. Sinha, the Head of the Department of Chemistry for their kind advice and encouragements.     

Amphotere Ionenaustauscherharze

Zusammenfassung N-Methyl--aminopropionsäure-Harz bindet infolge Komplexbildung Cu²⁺, UO₂ ²⁺, Bi³⁺, Cr³⁺ und Fe³⁺, während Ni²⁺, Co²⁺, Zn²⁺, Mn²⁺, Cd²⁺, Pb²⁺, Be²⁺, Tl⁺, NH₄ ⁺, Alkali-, Erdalkali- und Seltenerdionen keine Kapazität zeigen. Durch Variation des pH-Wertes, der Temperatur und Neutralsalzzusatz kann die Selektivität noch erhöht werden. Die analytische Anwendbarkeit wird an Hand von Trennungen binärer Gemische belegt, die oft als Filtrationsverfahren mit geringem Arbeits- und Zeitaufwand durchgeführt werden können.

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Summary N-Methyl--aminopropionic acid (MAP) containing resin binds Cu²⁺, UO₂ ²⁺, Bi³⁺, Cr³⁺ and Fe³⁺ due to its coordinating tendencies, whereas Ni²⁺, Co²⁺, Zn²⁺, Mn²⁺, Cd²⁺, Pb²⁺, Be²⁺, Tl⁺, NH₄ ⁺, alkalines, alkaline earths and rare earths are not retained. The selectivity can be increased by variation of pH, temperature and inert-salt background. Analytical applications have been shown by separations of binary mixtures. Sometimes these separations are simple and rapid filtration operations.

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1. Mitteilung: Kühn, G., u. E. Hoyer: J. prakt. Chem. (im Druck).

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Dem Direktor des Instituts für Anorganische Chemie, Herrn Prof. Dr. H. Holzapfel, gilt unser Dank für das entgegengebrachte Interesse und die Überlassung von Institutsmitteln.

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Herrn Doz. Dr. R. Hering, Güstrow, danken wir für wertvolle Hinweise.     

Thermodynamic metal-ligand stability constants of rare earths with N-p-chlorophenyl-m-substituted benzohydroxamic acids

The thermodynamic metal ligand stability constants of rare earths, La³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Bu³⁺, Gd³⁺ and Tb³⁺, with N-p-chlorophenyl-m-substituted benzohydroxamic acids in dioxan-water (60–70%) media at 25° C, have been determined by the potentiometric method. The effect of basicity of the ligand, central metal ion and the order of stability constants are discussed. The order of stability constants of rare earths with the hydroxamic acids is La<Pr<Nd<Sm<Eu<Gd>Tb.     

5: 6-Benzoquinaldinic acid as an analytical reagent: Determination of thorium and zirconium

Thorium and zirconium are determined in the presence of rare earths, alkaline earths and magnesium, when precipitated from weakly acid solution with 5:6-benzoquinaldinic acid. Thorium is completely precipitated at pH 3.0 as Th(C₁₄H₈O₂N)₄, but though zirconium is precipitated at the lower pH of 1.8, its composition is not stoichiometric and hence is ignited to the oxide before weighing. Co-precipitation of magnesium and alkaline earths is prevented by the addition of ammonium chloride.     

Organic azo-dyes in quantitative analysis

Summary Chrom Red Brown 5 RD has been found as a sensitive reagent for the spectrophotometric determination of thorium. Concentrations as low as 1 g thorium/1 ml can be easily determined at wave length 485 nm. Sulphate, chloride, ferric and zirconium ions badly interfere, while Li, Na, K, Ni, Co, Cu²+, Cd, Ca, Mg and Cr³⁺ do not. U⁶⁺ and Ce⁴⁺ are permissible as traces.Part II: Zaki, M. R., and K. Shakir: Z. analyt. Chem. 177, 196 (1960).     

Speciation of activators in electroluminescent thin films: an EXAFS study of cerium and terbium doped strontium sulfide

Extended X-ray absorption fine structure (EXAFS) was used to determine the local structure of the luminescent centers in Tb³⁺ and Ce³⁺ -doped strontium sulfide thin films deposited by Atomic Layer Epitaxy (ALE). The rare earths were observed to enter mainly the substitutional sites but at the same time a part of the atoms form RES clusters (RE = rare earth). The presence of both substitutional sites and RES clusters has been observed for the first time in this study for rare earths in II–VI compounds.     

Speciation of activators in electroluminescent thin films: an EXAFS study of cerium and terbium doped strontium sulfide

Extended X-ray absorption fine structure (EXAFS) was used to determine the local structure of the luminescent centers in Tb³⁺ and Ce³⁺ -doped strontium sulfide thin films deposited by Atomic Layer Epitaxy (ALE). The rare earths were observed to enter mainly the substitutional sites but at the same time a part of the atoms form RES clusters (RE = rare earth). The presence of both substitutional sites and RES clusters has been observed for the first time in this study for rare earths in II–VI compounds. Received: 9 February 1998 / Revised: 22 May 1998 / Accepted: 29 May 1998     

Determination of traces of rare earth elements in high-purity uranium by ion-exchange separation and neutron activation γ-spectrometry

Neutron activation γ-spectrometry is sufficiently sensitive for the determination of traces of rare earth elements but quantitative separation from uranium is essential. The rare earth elements in 0.2 M ammonium carbonate medium are quantitatively retained on Chelex-100, and are quantitatively separated from uranium by recycling the eluate. When 10-g samples are used, neutron activation provides detection limits of 1–20 μg kg^?1. Recoveries of rare earths, checked by spiking with radiotracers, are essentially complete.     

Bismuthiol II as an analytical reagent

Summary Lead was estimated as Bismuthiol II complex of composition (C₈H₅N₂S₃)₂Pb by precipitating it from its chloride or nitrate solution in presence of a mineral acid, acetic acid, tartrate or cyanide. The estimation is quantitative up to a maximumph of about 6.5. The lead-Bismuthiol II complex is stable up to about 311° C and the conversion factor is 0.315. The method affords a complete separation of lead from alkalis and alkaline earths, Be²⁺, Mg²⁺, Zn²⁺, Mn²⁺, Co²⁺, Ni²⁺, Fe²⁺, Fe³⁺, Cr³⁺, Al³⁺, rare earths, Ti⁴⁺, Zr⁴⁺, Th⁴⁺, UO₂ ²⁺, Pd²⁺, As³⁺, Sb³⁺, Cl^–, SO₄ ^2–, PO₄ ^3–, AsO₄ ^3–, MoO₄ ^2– and WO₄ ^2–. Among the sulphide group members Ag⁺, Au³⁺, Hg⁺, Hg²⁺, Tl⁺, Tl³⁺, Cd²⁺ and platinum metals, except Pd²⁺, interfere while oxidising agents decompose the excess reagent. Bi³⁺, Cu²⁺ and Sn²⁺, do not interfere up to a maximum limit of 30 mg, 50 mg, and 250 mg respectively.Part I: see Z. analyt. Chem. 154, 262 (1957).     

三维介孔氨基三亚甲基膦酸锆的合成及其担载铁催化剂的甲醛催化氧化活性

以氧氯化锆和氨基三亚甲基膦酸(ATMP)为原料合成了一种新型介孔材料氨基三亚甲基膦酸锆(NTAZP)。使用XRD、FTIR、TG-DTA和SEM等手段对所合成的介孔材料进行了结构表征和形貌分析。然后以NTAZP为载体,用Fe(NO3)3水溶液处理,得到担载Fe3+的氨基三亚甲基膦酸锆。研究结果表明,Fe3+被吸附到载体孔道中后,NTAZP结构未被破坏,Fe3+离子与NTAZP孔壁骨架上的N发生了配位作用。铁担载NTAZP(NTAZP-Fe3+)对甲醛氧化具有良好的催化活性,催化反应条件温和,催化剂稳定性良好。以载体NTAZP担载铁还避免了Fe3+进入水体,催化剂得以回收利用,避免造成二次污染。NTAZP-Fe3+是一种高效绿色的新型小分子醛类化合物氧化催化剂。     

Determination of traces of rare earths in high-purity thorium dioxide by neutron activation analysis

The use of thorium dioxide as a nuclear fuel requires the determination of individual rare earth impurities at 0.08–1 mg kg^?1 levels. Neutron activation is sufficiently sensitive but separation from the matrix is essential. In the proposed method, thorium dioxide (5–20 g) is dissolved in concentrated nitric acid with a little hydrofluoric acid; after evaporation, thorium is complexed with ammonium carbonate and the solution is passed through a small column of Chelex-100 resin which retains the rare earths quantitatively without retaining thorium. The rare earth elements are eluted with dilute nitric acid, concentrated, and irradiated with standards; after irradiation the rare earth are collected on a lanthanum carrier and measured by γ-ray spectrometry. The recoveries of rare earths were checked with tracers and by standard addition to thorium dioxide matrices. The reproducibility for La, Eu and Dy was satisfactory at 0.01, 0.003 and 0.002 mg kg^?1, respectively; as was the reproducibility for all rare earths added to thorium dioxide (1–4 μg/5 g). Limits of detection are adequate for certification of nuclear-grade material.     

Energy transfer phenomena in lead sulphate

It is shown that lead sulphate, PbSO₄, shows Pb²⁺ emission with a large Stokes shift. Energy transfer has been observed from the Pb²⁺ ions to several luminescent centres, viz., tungstate, molybdate, vanadate and rare earths. No transfer occurs to the Pr³⁺ ion.     

Investigation and Analytical Application of the β-Type Chelate of Lanthanoids With Chlorophosphonazo III

Abstract

The color-reaction of chlorophosphonazo III (CPA III) with lanthanide ions has been studied. It is found that under optimum conditions a light and heavy rare earth binuclear chelate with CPA III, of which the ratio of the metals to CPA III is 1:1:3, can be formed and used for determination of trace amounts of light rare earths in the presence of heavy rare earths. The molar absorptivity maximum of the chelate is 5x10⁵ 1 mol^?1 cm^?1.     

Study on the cocolouration effect in the β-complex formation reactions of rare earths with p-chloro-chlorophosphonazo (CPApC)

Terbium- and yttrium-group rare earths form β-complexes with CPApC in acidic medium.The sensitivities for determination of these rare earths by this reaction depend on their ionic radii.Cerium- or terbium-group rare earth in the presence of yttrium-group element produces the cocolourationeffect which remarkably sensitizes the reaction. Yb-CPApC-Eu complex has a molar composition of1:4:2 and gives a molar absorptivity of 2. 02 ×10~5 L·mol~(-1)·cm~(-1) at 746 nm for Eu. It is found thatthe closer the lengths of ionic radii of the rare earths are, the greater will be the cocolouration effect.     

Study on the selective leaching of low-grade phosphate ore for beneficiation of phosphorus and rare earths using citric acid as leaching agent

In the study the organic/inorganic chemical leaching and enrichment technology were used for selective extraction of the dolomite which co-existed in the Zhijin low-grade phosphate ore for beneficiation phosphorous and rare earths (RE) by using citric acid as leaching agent. The effects of acid concentration, reaction time, reaction temperature, liquid/solid ratio, and particle size on P₂O₅ and rare earths grade and the recovery ratio of them were investigated. The results show that under the optimized experimental conditions (acid concentration 9%, reaction time 240 min, reaction temperature 40°C, liquid/solid ratio 50: 1, and ore particle size 0.18–0.125 mm) the P₂O₅ grade can be increased from 15.47 to 34.82%, and P₂O₅ recovery rate comes up to 88.02%. The rare earths are mainly enriched in the leaching residues. Meanwhile, the recovery rate of rare earths is 72.08%. ΣREO grade can be increased from 978.06 × 10^–4 to 1998 × 10^–4%. In addition, the reaction kinetics of the chemical reaction between citric acid and dolomite are also discussed, the results show that the leaching process is controlled by chemical reaction. The activation energy for leaching was found to be 36.6337 KJ mol^–1 and k₀ was 3.67×104 s^–1, and the rate of the leaching based on the chemical reaction-controlled process could be expressed as 1–(1–a)^1/3 = 3.67 × 10⁴e^–36.63/RTt. Compare to the conventional process, the method provided in this study not only has advantages including higher phosphate concentration and rare earth grade, and higher recovery rate, but also using less amount of chemicals. Meanwhile, the citric acid can be recycled, avoiding discharge wastewater.     

Eu3+ as an MCD probe?

On the basis of the selection rules for magnetic dipole and induced electric dipole transitions in rare earths, the sign of the A₁ term corresponding to the ⁷F₀ → ⁵D₂ transition in the Eu³⁺ spectrum is shown to be related to the site symmetry of the Eu³⁺ ion. The most favourable coordination polyhedra of the rare earth ions are considered and the predicted MCD signals discussed. It is suggested that the induced electric dipole transition ⁵D₂ → ⁷F₀ in Eu³⁺ be used as an MCD probe for the determination of the coordination symmetry, while the ⁵D₁ → ⁷F₀ can be used as a sign reference transition.     

Complexometric titration of copper(II) using nitrosochromotropic acid as a new metal indicator

Summary Nitrosochromotropic acid gives a violet coloured soluble complex with Cu^II in ammonium chloride-ammonium hydroxide buffer solution, which is less stable than Cu^II-EDTA complex. When microquantities of Cu^II solution containing 1 or 2 drops of nitrosochromotropic acid in the ph range 7.25 to 8.00, are titrated with EDTA, a sharp colour change from violet to orange occurs at the end point. The method of titration can be carried out from 20° to 40° C, but the copper complex dissociates at higher temperature and gives low results. The separation of Zn²⁺, Cd²⁺, Co²⁺, Ni²⁺, Pb²⁺ and alkaline earths, is necessary as they interfere in the titrations with EDTA.

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Zusammenfassung Nitrosochromotropsäure bildet mit Kupfer(II) in Ammoniumchlorid-Ammoniak-Pufferlösung einen violett gefärbten löslichen Komplex, der weniger stabil ist als der Kupfer(II)-ÄDTA-Komplex. Mikromengen Kupfer(II) können imph-Bereich von 7,25–8,00 unter Zusatz von 1–2 Tropfen Nitrosochromotropsäurelösung als Indicator mit ÄDTA-Lösung titriert werden, wobei am Endpunkt ein scharfer Umschlag von Violett nach Orange erfolgt. Die Temperatur der Lösung soll 20–40° C betragen; bei höherer Temperatur erhält man zu niedrige Werte, da der Kupferkomplex dann dissoziiert. Zn²⁺, Cd²⁺, Co²⁺, Ni²⁺, Pb²⁺ und Erdalkalien müssen vor der Titration abgetrennt werden.

     

Stability Constants of Rare Earths with Violuric Acids

The metal ligand stability constants of violuric acid [H₂VA], N-methyl violuric acid [H₂MVA], N-phenyl violuric acid [H₂PVA] and N-(o-m-p) tolyl violuric acids [N-H₂(o-m-p)TVA] with La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Dy(III), and Ho(III) have been determined potentiometrically in 50 Vol% ethanol water media at 25°C and at an ionic strength of 0.1 M NaClO₄. The stability of the complexes follow the order of basicities of ligands and also the electron affinities of rare earths as measured by their overall ionisation potential. The order of stabilities of rare earths with violuric acids is, La³⁺ < Ce³⁺ < Pr³⁺ < Nd³⁺ < Sm³⁺ < Gd³⁺ < Eu³⁺ < Dy³⁺ < Ho³⁺.