Determination of vanadium in refractory metals, steel, cast iron, alloys and silicates by extraction of an NBPHA complex from a sulphuric-hydrofluoric acid medium

A method for determining up to 0.15% of vanadium in high-purity niobium and tantalum metals, cast iron, steel, non-ferrous alloys and silicates is described. The proposed method is based on the extraction of a red vanadium(V)-N-benzoyl-N-phenylhydroxylamine complex into chloroform from a sulphuric-hydrofluoric acid medium containing excess of ammonium persulphate as oxidant. The molar absorptivity of the complex is 428 l.mole(-1).mm(-5) at 475 nm, the wavelength of maximum absorption. Interference from chromium(VI) and cerium(IV) is eliminated by reduction with iron(II). Common ions, including large amounts of titanium, zirconium, molybdenum and tungsten, do not interfere.     

Determination of divalent trace metals in natural waters by preconcentration on N,N,N′,N′-tetra(2-aminoethyl)ethylenediamine-silica followed by on-line ion chromatography

A method for the on-line preconcentration and chromatography of trace metals, e.g., Co, Ni, Cu, Zn, Cd and Pb, on N,N,N′,N′-tetra(2-aminoethyl)ethylenediamine-bonded silica is described. The preconcentrated metals were desorbed with 0.13 M tartrate, which allows direct separation on a cation-exchange chromatographic column. The metals separated were detected by postcolumn reaction with 4-(2-pyridylazo)resorcinol and measuring the absorbances at 500 nm. Linear calibration graphs were obtained over the range 1 · 10⁻⁸−3 · 10⁻⁶ M. The synthesis and characteristics of the chelated silica are described. The method was applied to the analysis of river and interstitial sediment waters.     

Determination of titanium in high-purity molybdenum and tungsten metals with diantipyrylmethane after separation by extraction of its cupferron complex

A method for determining 0.0005–0.10% of titanium in high-purity molybdenum and tungsten metals is described. After sample dissolution, titanium is separated from the matrix materials by chloroform extraction of its cupferronate from an alkaline (pH 8) tartrate-EDTA medium, then determined spectrophotometrically with diantipyrylmethane at 390 nm. Interference from manganese during extraction is eliminated with sodium sulphite. Iron, zirconium, thorium, tin, aluminium and antimony are partially extracted under the proposed conditions, but moderate amounts of these elements may be present in the sample solution without causing error in the results. Interference from iron(III) during colour development is eliminated with ascorbic acid. Other impurities in the two high-purity metals described do not interfere in the proposed method.     

Uniform MgO nanobelts formed from in situ Mg3N2 precursor

MgO nanobelts with a pure morphology and high yield were generated by the direct evaporation of Mg metals under initial N₂ gas at 650 °C and subsequent N₂/O₂ atmosphere at 800 °C. The growth of these MgO nanobelts is explained in a VS route in which the in situ formed Mg₃N₂ slowly decomposes and reacts with oxygen. Mg₃N₂ is therefore a very effective precursor for the fabrication of high-purity one-dimensional (1D) MgO nanostructures.     

Determination of manganese in high-purity niobium, tantalum, molybdenum and tungsten metals with pan

A spectrophotometric method for the determination of 0.0005-0.10% of manganese in high-purity niobium, tantalum, molybdenum and tungsten metals is described. The matrix materials are separated from the manganese by extraction as cupferrates, after sample dissolution, then the red complex formed between manganese(II) and 1-(2-pyridylazo)-2-naphthol, PAN, is extracted into chloroform from an ammoniacal tartrate-cyanide medium. The absorbance of the extract is determined at 562 mmicro. With the exception of zinc and lead, other impurities present in the four high-purity metals described do not interfere with the proposed method.     

Spectrophotometric study and analytical application of the reaction between manganese(II) and 4-(2-pyridylazo)resorcinol

A highly sensitive method for spectrophotometric determination of manganese(II) with 4-(2-pyridylazo)resorcinol (PAR) as reagent is described. The molar absorptivity of the complex was found to be 8.65 ± 0·04 x 10⁴. The stability constant of the ML₂ complex was found to be log β₂ = 15·6. Beer's law is obeyed within the range 0·02–0·5 μg of Mn/ml. An application of this reaction for analytical purposes is described.     

Determination of cobalt and zinc in highpurity niobium, tantalum, molybdenum and tungsten metals by atomicabsorption spectrophotometry after separation by extraction

A method for determining 0.0005-0.05% of cobalt and zinc in high-purity niobium, tantalum, molybdenum and tungsten metals by atomic-absorption spectrophotometry is described. After sample dissolution, cobalt and zinc are separated simultaneously from the matrix materials by chloroform extraction of their thiocyanatediantipyrylmethane ion-association complexes, at pH 3.25, from a citric acid medium approximately 1.2M in sodium thiocyanate. Interference from copper is eliminated with thiourea. Large amounts of iron interfere under the recommended conditions, but moderate amounts may be present in the sample solution without causing appreciable error in the results. Phosphorus (as orthophosphate) interferes in the extraction of cobalt from tungsten solutions. Moderate amounts of other impurities do not interfere in the proposed method.     

Liquid-liquid interface assisted synthesis of size- and thickness-controlled Ag nanoplates

Here we proposed a synthetic method of high-purity Ag nanoplates by the reduction of aqueous Ag⁺ ions at the aqueous-organic interface with the reductant ferrocene. We demonstrated that the as-prepared Ag nanoplates can be widely tunable from 600 nm to 7 μm in size and from 10 to 35 nm in thickness, simply by adjusting the component of organic phase. To our knowledge, there are few methods to tailor the size and the thickness of metal nanoplates in such a large range although many efforts have been made aiming to realize it. Our proposed synthetic strategy is rapid, template-free, seed-less, and high-yield, and could be applied to synthesize analogous two-dimensional nanostructures of other noble metals, such as Pt, Au, and Pd.     

New spectrophotometric thiocyanate determination of iron in metals,alloys, acids and salts

A rapid, sensitive and fairly selective spectrophotometric thiocyanate method for the determination of traces of iron in metals, alloys, acids and salts is described. The iron is isolated from the bulk of the sample by solvent extraction with methyl isobutyl ketone from ₇N lithium chloride solution or ₇N hydrochloric acid. The iron (III) thiocyanate color is developed directly in the ketone extract and then measured spectrophotometrically.     

Simple radiochemical neutron-activation method for the determination of uranium in ultramafic rocks

A radiochemical neutron-activation method for the determination of trace concentrations of uranium in rocks is described. The method is based on separation of 23·5-min ²³⁹U after alkaline fusion by extraction with tri-n-butyl phosphate from moderately concentrated nitric acid, followed by measurement of the 74-keV γ-ray with a Ge(Li) detector. The limit of detection is 0·2 ng of U under the present conditions, and the precision at the 0·005 ppm level is about 10%. The method is especially useful for determination of uranium in ultramafic rocks.     

Polarographic determination of nitramide

Nitramide gives two cathodic polarographic waves with half-wave potentials varying with pH, and having minimum values − 1·22 V at pH 4·5 and − 1·58 V at pH 8·8. Nitramide is fist reduced to nitrosamine in a two-electron reduction. In the second step, hydroxy-hydrazine may be formed in a two-electron reduction, or hydrazine itself in a four-electron step. For the polarographic determination of nitramide the first wave is used, and the supporting electrolyte is a Britton—Robinson buffer 0·1 M in KCl, at pH < 5 and at 0–2°.     

Utilisation des radioisotopes de courtes périodes pour le dosage d'éléments traces dans les métaux de haute pureté par activation neutronique

A complete study of high-purity metals must include the determination of some elements giving only short-lived radioisotopes by the (n, γ) reaction. In the case of elements giving also long-lived radioisotopes, the use of a short-lived isotope may be advantageous in two cases: possibility of a quick non-destructive analysis or better sensitivity. The determination of aluminium in iron, zirkonium and molybdenum and of cobalt in iron and nickel is described in detail. When necessary quick chemical separations have been developed. The determinations permit to follow the purification of the metals studied.     

A turbidimetric method to measure isoelectric points and particles deposition onto massive substrates

A simple experimental approach was developed to determine the adhesion rate of particles onto massive substrate. Turbidimetry measurements are used to follow the evolution of particle concentration in a suspension in dynamic contact with the walls of a vessel made of different materials. This method allows to rapidly obtain qualitative results about the adhesion of metallic oxides particles on massive substrates. Adhesion of particles of charged latex onto glass was used to validate the approach and was shown to be a method to determine isoelectric points (IEP) of massive substrates. Then, the adhesion of an iron oxide (hematite) particles onto several substrates was studied to determine the reactivity of current labware (glass, polypropylene) and on a metal (aluminum) commonly found in industrial fouling problems. Adhesion of hematite was found to be pH-dependant, and occurs only below ca. 6 (glass) or 7 (polypropylene), and above 7 (aluminum). DLVO calculations were performed to model the hematite/water/glass system and are consistent with the experimental results. Experiments at temperature 7–50 °C have shown an increasing of the adhesion rate from 7 to 40 °C, then a constant value until 50 °C.     

Über peroxo-mischkomplexe von titan, niob und tantal—III Die chelometrische titration von fünfwertigem niob

A chelatometric method for the titration of Nb^v, using nitrilotriacetic acid is described. This forms a 1:1 complex with the peroxy-Nb^v ion. NTA is added in excess, and the excess is backtitrated with Cu solution at pH 5·0–5·5 using the metallofluorescent indicator, Methylcalcein, under UV illumination. The reproducibility, for amounts of 4·56–23·68 mg of Nb is 0·07 mg of Nb. N-Hydroxyethylethylenediamine-N,N',N'-triacetic acid forms a similar 1:1 complex, and can be used instead of NTA, but with little advantage.

Résumé

On décrit une méthode de dosage du Nb (V) par formation de chélates. L'acide nitrilotriacétique, qui forme un complexe 1/1 avec les ions peroxoniobium (V) est utilisé comme agent chélatant. On ajoute du NTA en excès er l'on dose en retour par une solution de cuivre en utilisant comme indicateur de fluorescence la méthylcalcéine sous irradiation ultra-violette. Les analyses d'essais portant sur des échantillons variant de 4,56 mg à 23,68 mg de niobium fournissent une reproductibilité de ± 0,07 mg. L'acide N-hydroxyéthyléthylénediamine-N,N'.N'-triacétique forme également un complexe 1/1 avec les ions peroxoniobium (V) et peut être utilisé à la place du NTA mais ne présente pas d'avantages particuliers.     

Calorimetric study of the relationship between molecular structure and liquid-crystallinity of rod-like mesogens I. Heat capacities and phase transitions of 4'-propylbiphenyl-4-carbonitrile and trans, trans-4'-propylbicyclohexyl-4-carbonitrile

The heat capacities of the rod-like compounds 4'-propylbiphenyl-4-carbonitrile (3-BBCN) and trans, trans-4'-propylbicyclohexyl-4-carbonitrile (3-CCCN) have been measured with an adiabatic calorimeter between 12 and 383 K. 3-BBCN is not mesogenic and melts into an isotropic liquid at 338·77 K, whereas 3-CCCN is mesogenic and its melting and clearing points are 330·73 K and 353·80 K, respectively. The enthalpy and entropy of fusion of 3-BBCN are 22·7 kJ mol^-1 and 67·0 J K^-1 mol^-1, respectively, while those of 3-CCCN are 27·0 kJ mol^-1 and 81·7 J K^-1 mol^-1, respectively. The enthalpy and entropy gain due to the nematicisotropic transition of 3-CCCN are 1·8 kJ mol^-1 and 5·0 J K^-1 mol^-1. 3-CCCN shows a mesomorphic transition from a smectic to the nematic state at 329·62 K, which occurs as a metastable state, its transition enthalpy and entropy are 5·4 kJ mol^-1 and 16·4 J K^-1 mol^-1, respectively. The temperature dependence of the molar entropies of both compounds shows that molecular arrangement in the crystal is more ordered in 3-CCCN than in 3-BBCN. This fact may be related to the stability of mesophases. Finally, Eidenschink's theoretical model for the nematicisotropic transition has been applied to 3-CCCN. As far as the present mesogen is concerned, the transition enthalpy estimated according to this model agrees well with the observed value.     

Determination of trace amounts of lead, arsenic, nickel and cobalt in high-purity iron oxide pigment by inductively coupled plasma atomic emission spectrometry after iron matrix removal with extractant-contained resin

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was applied to the determination of lead, arsenic, nickel and cobalt in high-purity iron oxide pigment. Samples were dissolved with hydrochloric acid and hydrogen peroxide. The digest was passed through a column, which was packed with a polymer resin containing a neutral organophosphorus extractant, tri-n-butylphosphate. Iron was sorbed selectively on the resin and the analytes of interest passed through the column, allowing the effective separation of them from the iron matrix. Conditions of separation were optimized. The detection limits (3σ) in solution were 10, 40, 7 and 5 μg L⁻¹, and in pigment were 0.2, 0.8, 0.14 and 0.1 mg kg⁻¹ for lead, arsenic, cobalt and nickel, respectively. The recoveries ranged from 95% to 107% when sample digests were spiked with 5 μg of the analytes of interest, and relative standard deviations (n = 6) were 1.5-17.6% for the determination of the spiked samples. The method was successfully applied to the determination of trace amounts of these elements in high-purity iron oxide pigment samples.     

The preparation of bimetallic complexes with the ligand 1-oxy-2,6-di[N,N-biscarboxymethyl)aminomethyl]-4-chlorobenzol, and their physico-chemical characterization

With the binucleating ligand 1-oxy-2,6-di [(N,N-biscarboxymethyl)aminomethyl]- 4-chlorobenzol (H₅L) complexes of formulae FeH₂L · 2H₂O; FeH₃L(C1O₄) · H₂O; Fe₂L(OH) · 2H₂O; M₂HL · nH₂O (M = Co, Cu, n = 2; M = Ni, n = 4); FeCuL · 3H₂O; FeCrL(OH) · 3H₂O were prepared and characterized by elemental analysis, IR and electronic spectra and magnetic moment determinations. In addition, thermal analysis data of the complexes and Mössbauer effect spectra of the iron containing complexes are also given and discussed.     

Spectrophotometric determination of ruthenium with 8-quinolinol

A spectrophotometric method is described for the determination of 2–80 μg of ruthenium. The method involves oxidation of ruthenium to ruthenate, addition of 8-quinolinol, adjustment of the pH to 4–6.5, digestion of the complex formed at 85° for 30 min, extraction with chloroform, and measurement of absorbance at 430 nm. Almost all other metals and excess of reagent are removed by washing the extract. About 98 % of ¹⁰⁶Ru tracer was recovered.     

Determination of trace impurities in high-purity iron using salting-out of polyoxyethylene-type surfactants

To an iron sample solution was added polyoxyethylene-4-isononylphenoxy ether (PONPE, nonionic surfactant, average number of ethylene oxides 7.5) and the surfactant was aggregated by the addition of lithium chloride. The iron(III) matrix was collected into the condensed surfactant phase in >99.9% yields, leaving trace metals [e.g., Ti(IV), Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II), and Bi(III)] in the aqueous phase. After removing the surfactant phase by centrifugation, the remaining trace metals were concentrated onto an iminodiacetic acid-type chelating resin. The trace metals were desorbed with dilute nitric acid for the determination by inductively coupled plasma-mass spectrometry or graphite-furnace atomic absorption spectrometry. The proposed separation method allowed the analysis of high-purity iron metals for trace impurities at low μg g⁻¹ to ng g⁻¹ levels.     

Collisional quenching of electronically excited germanium atoms, Ge[4p(S0)], by small molecules investigated by time-resolved atomic resonance absorption spectroscopy

The collisional quenching of electronically excited germanium atoms, Ge[4p²(¹S₀)], 2.029 eV above the 4p²(³P₀) ground state, has been investigated by time-resolved atomic resonance absorption spectroscopy in the ultraviolet at λ = 274.04 nm [4d(¹P₁⁰) ← 4p²(¹S₀)]. In contrast to previous investigations using the ‘single-shot mode’ at high energy, Ge(¹S₀) has been generated by the repetitive pulsed irradiation of Ge(CH₃)₄ in the presence of excess helium gas and added gases in a slow flow system, kinetically equivalent to a static system. This technique was originally developed for the study of Ge[4p²(¹D₂)] which had eluded direct quantitative kinetic study until recently. Absolute second-order rate constants obtained using signal averaging techniques from data capture of total digitised atomic decay profiles are reported for the removal of Ge(¹S₀) with the following gases (k_R in cm³ molecule⁻¹ s⁻¹, 300 K): Xe, 7.1 ± 0.4 × 10⁻¹³; N₂, 4.7 ± 0.6 × 10⁻¹²; O₂, 3.6 ± 0.9 × 10⁻¹¹; NO, 1.5 ± 0.3 × 10⁻¹¹; CO, 3.4 ± 0.5 × 10⁻¹²; N₂O, 4.5 ± 0.5 × 10⁻¹²; CO₂, 1.1 ± 0.3 × 10⁻¹¹; CH₄, 1.7 ± 0.2 × 10⁻¹¹; CF₄, 4.8 ± 0.3 × 10⁻¹²; SF₆, 9.5 ± 1.0 × 10⁻¹³; C₂H₄, 3.3 ± 0.1 × 10⁻¹⁰; C₂H₂, 2.9 ± 0.2 × 10⁻¹⁰; Ge(CH₃)₄, 5.4 ± 0.2 × 10⁻¹¹. The results are compared with previous data for Ge(¹S₀) derived in the single-shot mode where there is general agreement though with some exceptions which are discussed. The present data are also compared with analogous quenching rate data for the collisional removal of the lower lying Ge[4p²(¹D₂)] state (0.883 eV), also characterized by signal averaging methods similar to that described here.