Investigation of the surface of Ni-Pd catalysts by IR spectroscopy

The reaction of carbon monoxide with the surface of Ni, Pd, and Ni-Pd catalysts, deposited on -Al₂O₃, was investigated at 25°C by IR spectroscopy in conjunction with an adsorption volumetric technique. The IR spectra contained the following absorption bands (v, cm^–1): 2020–2100 (AB1) (linear and subcarbonyl forms of adsorbed CO); 1945–1985 (AB2) (bridging); 1920–1940 (AB3) with a shoulder at 1870–1885 (AB4) (bridging and many-center). In the spectrum of Ni the absorption band AB5 appears at 1770–1780 (CO-Ni⁺). It appears with surface coverage a 1.3 mole CO/mole M. The optical density (A) of AB1 for Ni₉₇Pd₃ is appreciably higher than for the other investigated samples. In the Ni-Pd catalysts the intensity of AB2 in relation to AB1 is higher than in nickel. The introduction of K⁺ ions into the support of the bimetallic sample reduces the optical density of AB1. In modified Ni-Pd-K the AB3 and AB4 bands disappear.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1276–1282, June, 1992.     

Thermal diffusion of dilute aqueous Na2MgEDTA and Na2CaEDTA solutions at 25°C

The Soret effect in dilute aqueous solutions (0.01–0.1m) of Na₂MgEDTA and Na₂CaEDTA is investigated using the flow-cell method. The Soret coefficients obtained from thermal diffusion experiments conducted at 25°C are reported. Heats of transport have been estimated based on the Debye-Hückel theory and the molar entropies of transport, calculated. Results of the present work have been compared with the Soret data for MgCl₂ and CaCl₂. It is suggested that the solvent exchange effect may account for the differences in the Soret effect observed between the pairs (Mg⁺², Ca⁺²) and (MgEDTA^–2, CaEDTA^–2).     

Mass-spectrometric study of tetrafluorohydrazine and the products resulting from its breakdown under electron impact

Conclusions Electron-impact methods have been used to study positive (NF⁺, NF₂ ⁺, N₂F₂ ⁺) and negative (F^–, F₂ ^–, N₂F^–, NF₂ ^–) ion formation in the mass spectra of tetrafluorohydrazine and its decomposition products.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1306–1311, June, 1978.The authors would like to thank V. Ya. Rosolovskii for a discussion of the results obtained in this work.     

Quantitative chemical analysis on paper: Determination of phosphate in the presence of large quantities of other ions

Summary A rapid method has been developed for the determination of phosphate by means of filter paper impregnated with lead iodide. A sample is added to the impregnated filter paper by means of a capillary, and after irrigation to cause migration of the ions a white spot is obtained as the lead iodide is converted into the phosphate. The weight of the spot is dependent on the p_H and the quantity of phosphate present.The determination is possible in the presence of SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, I^–, IO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, succinic, citric and tartaric acids. The determination is impossible in the presence of C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2–, or CO₃ ^2–.The method permits the determination of 7–100g of phosphate with an accuracy of 2%.

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Zusammenfassung Ein schnelles Verfahren zur Phosphatbestimmung wird besehrieben, bei dem man sich eines mit Bleijodid imprägnierten Filterpapiers bedient. Die Probe wird mit einer Kapillare auf das Papier aufgebracht. Man erleichtert die Ionenbewegung durch geeignete Befeuchtung und erhält einen weißen Fleck infolge Umsetzung des Bleijodids in -phosphat. Das Gewicht des Fleckens hängt vom p_H und von der Phosphatmenge ab.Die Bestimmung ist möglich in Gegenwart von SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, J^–, JO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, Bernsteinsäure, Zitronensäure und Weinsäure; sie ist nicht möglich bei Gegenwart von C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2– oder CO₃ ^2–. 7 bis 100g Phosphat können mit einer Genauigkeit von 2% bestimmt werden.

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Résumé On a développé une méthode rapide pour le dosage des phosphates sur papier-filtre imprégné d'iodure de plomb. On dépose l'échantillon sur le papier-filtre imprégné, à l'aide d'un capillaire, et, après humidification pour provoquer la migration des ions, on obtient une tache blanche quand l'iodure de plomb est converti en phosphate. Le poids de la tache dépend du p_H et de la quantité de phosphate présent.Le dosage est possible en présence de SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, I^–, IO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, et des acides succinique, citrique et tartrique. Il est impossible en présence de C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2– ou CO₃ ^2–.La méthode permet le dosage de 7 à 100g de phosphate avec une précision de 2%.

     

Distribution studies of metal ions on arsenophosphates of Sn(IV) and Cr(III) and on amine Sn(II) hexacyanoferrates (II) using radio tracers: Separation of Sr2+−Cs+, Hg2+−Ag+ and Hg2+−Zn2+

Summary Distribution studies of some metal ions have been made on Sn(IV) and Cr(III) arsenophosphates and on some samples of Sn(II) amine hexacyanoferrates(II), using radiotracers. The K_d values of Cs⁺ and Rb⁺ have been followed at varying HNO₃ concentrations also. As a result 3 useful binary separations have been achieved on Sn(IV) and Cr(III) arsenophosphates, such as Sr²⁺–Cs⁺, Hg²⁺–Ag⁺ and Hg²⁺–Zn²⁺.     

A kinetic study on the iron(III)-promoted aquation of [Cr(C2O4)2(picolinato)]2− and [Cr(C2O4)2(2-pyridineacetato)]2− complexes

Two [Cr(C₂O₄)₂(AB)]^2– type complexes, obtained from the reaction of cis-[Cr(C₂O₄)₂(H₂O)₂]^– with the AB ligand, [AB = picolinic (pyac) or 2-pyridine-ethanoic acid (pyeac) anions], were converted into [Cr(C₂O₄)(pyac)(H₂O)₂]⁰ and [Cr(C₂O₄)(pyeac)(H₂O)₂]⁰ compounds, respectively via Fe^III-induced substitution of the oxalato ligand. The aquation products were separated chromatographically and their spectral characteristics and acid dissociation constants determined. The kinetics of the oxalato ligand substitution were studied with a 10–40 fold excess of Fe^III over [Cr^III] at [H⁺] = 0.2 M and at constant ionic strength 1.0 M (Na⁺, H⁺, Fe³⁺, ClO^– ₄). The reaction rate law is of the form: r = k _obs[Cr^III], where k _obs = kQ[Fe^III]/(1 + Q[Fe^III]). The first-order rate constants (k), preequilibria quotients (Q) and activation parameters derived from the k values have been determined. The reaction mechanism is discussed in terms of a Lewis acid catalyzed (induced) ligand substitution.     

Field-evaporation mass spectroscopy applied to crown ether complexes with alkali and alkaline-earth metals

Field evaporation from solution has been used to detect crown-ether 15K5 and 18K6 coordination compounds formed with Na⁺, K⁺, Cs⁺, Ba²⁺ and Ca²⁺ in aqueous solution, both hydrated and unhydrated; the Ca²⁺·18K6·(H₂O)_n (n=0, 1, 2,...) compounds have been observed before. 18K6 present in the solution greatly increases the yields of 18K6 compounds with the dissociation products from Ba(NO₃)₂. The detection limits for 15K5 and 18K6 combined with Na⁺, K⁺, and Cs⁺ are approximately the same at 10^–7 g.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 239–242, March–April 1988.     

A structural study of saturated aqueous solutions of some alkali halides by X-ray diffraction

The structure of nearly saturated or supersaturated aqueous solutions of NaCI [6.18 mol (kg H₂O)^–1], KCI [4.56 mol (kg H₂O)^–1], KF [16.15 mol (kg H₂O)^–1] and CsF [31.96 mol (kg H₂O)^–1] has been investigated by means of solution X-ray diffraction at 25°C. In the NaCI and KCI solutions about 30% and 60%, respectively, of the ions form ion pairs and the Na⁺–Cl^– and K⁺–Cl^– distances have been determined to be 282 and 315 pm, respectively. The average hydration numbers of Na⁺ and Cl^– ions are 4.6 and 5.3, respectively, in the NaCI solution and those of K⁺ and Cl^– ions in the KCI solution are both 5.8. In the KF solution, clusters containing some cations and anions, besides 1:1 (K⁺–F^–) ion pairs, are formed. The K⁺–F^– interatomic distance has been determined to be 269 pm, and nonbonding K⁺...K⁺ and F^–...F^– distances in the clusters are 388 and 432 pm, respectively, and the average coordination numbers n _KF , n _KK and n _FF have been estimated to be 2.3, 1.9, and 1.6, respectively. In the highly supersaturated CsF solution an appreciable amount of clusters containing several caesium and fluoride ions are formed. The Cs⁺–F^– distance in the cluster has been determined to be 312 pm, while the nonbonding Cs⁺...Cs⁺ and F^–...F^– distances are estimated to be 442 and 548 pm, respectively, the distances being about and times the Cs⁺–F^– distance, respectively. The coordination numbers n _CsF , n _CsCs , and n _FF in the first coordination sphere of each ion are 3.3, 2.3 and 5.3, respectively, and the result shows the formation of clusters of higher order than 1:1 and 2:2 ion pairs. These ion pairs and clusters may be regarded as embryos for the formation of nuclei of crystals and the results obtained in the present diffraction study support observations for the nucleation of the alkali halide crystals studied by molecular dynamics simulations previously examined.     

Mechanisms of the reactions of propane with CBr3+ cation and superelectrophilic complex CBr4+·AlBr3- containing a bromine-centered cationic center: a theoretical study

Fragments of the potential energy surfaces (PES) of the systems [C₃H₈ + CBr₃ ⁺] and [C₃H₈ + Br₂CBr⁺·Br₂AlBr₂ ^–] were simulated by the MNDO/PM3 method. Energy minima corresponding to weakly bound adducts of propane molecule with the CBr₃ ⁺ cation or neutral complex CBr₃ ⁺·AlBr₄ ^– were found on the PES's of both systems. These are adducts with the coordination of a H atom of the methylene group of the propane molecule to the electrophile at the Br atom carrying the largest positive charge. As the fragments of the adducts are brought close together, the coordinated H atom migrates to the C atom of the CBr₃ ⁺ fragment. The potential barriers of these migrations were found to be low for both systems. The reactions proceed without formation of cyclic intermediates or transition states typical of the Olah mechanism.     

Determination of copper(I)-ethylene complexes, [Cu(C2H4)]+ and [Cu(C2H4)2]+, with aid of EDTA titration of copper(I) and copper(II) ions

Summary Volumetric measurements of ethylene and simple EDTA titration of copper(I) and copper(II) ions confirm that [CuL]⁺ and [CuL₂]⁺ are formed when an aqueous solution of copper(II) is reduced by copper metal in the presence of ethylene, (L). The formation constants,K ₁=[CuL⁺]²[Cu²⁺]^–1[L]^–2 andK ₂=[CuL ₂ ⁺ ]^–1[L]^–1, have been estimated. The formation of [CuL]⁺ is accompanied by an enthalpy change, H, of –25 kJ mol^–1, and a positive entropy change, S, of 13 J mol^–1 K^–1.     

Carbohydrates, amino acids, phytin, and macroelements of the herbage ofTrifolium pratense

Two monosaccharides have been found by paper chromatography in an aqueous extract of the herbage of red clover (Trifolium pratense). One of them has been identified as glucose. After hydrolysis of a dry water-soluble extract by paper chromatography in the presence of markers, galactose, arabinose, xylose, and mannose were detected. By paper chromatography in the presence of markers the amino acids phenylalanine, leucine (isoleucine), methionine, aspartic acid, proline, alanine, and histidine have been identified. Phytin with decomp. p 276°C has been isolated and identified, giving, after hydrolysis, inositol with mp 225–226°C, and Ca²⁺, Mg²⁺, and PO ₄ ^3– have been detected. The amount of ash in the herbage of clover is 8.4% and the amount insoluble in HC1 1.5%. The amounts of macroelements were determined by the flame photometry of a solution of the ash (mg–%): K⁺ 1620; Na⁺ 310; Ca²⁺ 1240; Mg²⁺ 1090.Pyatigorsk Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 483–485, July–August, 1980.     

Nonempirical investigation of the influence of the outer-sphere environment on the geometric structure of [AF5] n−

Nonempirical calculations of the electronic structure of the [PF₅]^2– ion and of the clusters [M₅PF₅]³⁺ and [M₄PF₅]²⁺ (M=H⁺, Li⁺, Na⁺) have been carried out. The character of the dependence of the geometric parameters of the [PF₅]^2– ion on the properties and structure of the second coordination sphere has been discussed.Institute of Chemistry, Academy of Sciences of the USSR, Far-Eastern Branch. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 2, pp. 17–22, March–April, 1991.     

Effects of alkali-metal cations on nitrate-ion N-O bond force constants in ionic melts

Measured frequencies from pure nitrate liquids have been used to calculate the force constants for the nitrate ion and the M⁺-NO₃ ^– systems (M⁺ = Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺) by a matrix successive-approximation method based on perturbation theory in dependent coordinates. The valency force constants K_q for the N-O bonds are increased by comparison with free NO ₃ ^– . The N-O bond strengthening is not adequately explained by cation-anion interaction because there is electron-density transfer mainly by the mechanism within the NO ₃ ^– . Correction for the vibrational parameters of the interacting particles confirms the previously demonstrated acid-base mechanism for the cation-anion interaction in liquids containing nitrate.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 230–234, March–April, 1989.     

1H NMR studies on intermolecular association of amphiphilic cationic polyelectrolyte micelles induced by hydrophobic counteranions in water

Interactions of a series of amphiphilic cationic polyelectrolytes with various kinds of organic counteranions have been investigated in water by one- and two-dimensional ¹H NMR spectroscopy at 20 °C. The cationic polyelectrolytes were prepared by micellar homopolymerization of tail-type cationic surface-active monomers with a cationic charge with -end, (ST–C_m–AB, m=5, 7, and 9, where ST is a styrenic group, C_m, an alkylene chain at the 4-position of styrene, and AB, alkyltrimethylammonium bromide). Aliphatic monosodium salt of maleic acid (MAS) and its stereoisomer, fumaric acid (FAS), sodium benzoate (NaB), potassium hydrogen phthalate (PHK), and sodium salicylate (NaSal) were added to a salt-free aqueous solution of the polyelectrolytes and ¹H NMR measurements were carried out. Amphiphilic P(ST–C_m–AB) polyelectrolytes act as efficient hosts to strongly capture the hydrophobic counteranions B^–, PH^–, and Sal^–, but not MA^– and FA^–. The ¹H NMR signals of these hydrophobic counteranions remarkably shift upfield and broaden in water in the presence of the amphiphilic polyelectrolytes. The nuclear Overhauser effect (NOE) signals between the cationic group of the polymer and aromatic benzoate counteranion protons are clearly observed to imply cation– interaction. The capturing of hydrophobic counterions by the polyelectrolytes is likely due to electrostatic, hydrophobic, and cation– interactions between them. The reduced viscosity, _sp/C_p, for the solution at [PHK]/[P(ST–C₇–AB)]=1.0 steeply increases with increasing polymer concentration (C_p) above ca. 0.9 g/dL to show pronounced viscoelasticity.     

Studies on ion exchange equilibria and kinetics VI. Prediction of ion exchange equilibria of UO 2 2+ −Na+−H+ ternary system

Experimental data are reported for the ion exchange equilibria of the binary systems UO ₂ ²⁺ –H⁺, UO ₂ ²⁺ –Na⁺ and Na⁺–H⁺, and of the ternary system UO ₂ ²⁺ –Na⁺–H⁺ on a strong acid cation exchange resin 001X7 at 25 °C. It is found that the equilibria for any pairs of ions are essentially the same in binary and ternary mixtures and that the prediction method proposed by our laboratory for SO ₂ ^2– –Cl^––NO ₃ ^– -201X7 strong base anion exchange resin system is also applicable to the ternary system studied in this paper. The predictions of the ternary system UO ₂ ²⁺ –Na⁺–H⁺ based solely on the binary data without using resin phase activity coefficients are consistent with the experimental data.     

Azido-, Rhodano-, Cyano- und Fluorokomplexe des Fe(III)-Ions in Dimethylsulfoxid

Zusammenfassung Auf Grund spektrophotometrischer und konduktometrischer Messungen wurden folgende Koordinationsformen des Eisen(III)-ions mit Azid-, Rhodanid-, Cyanid- und Fluoridionen in Dimethylsulfoxid festgestellt: [Fe(N₃)₄]^–, [Fe(SCN)₆]^3–, [Fe(CN)₂]⁺, Fe(CN)₃, [Fe(CN)₄]^–, [FeF₂]⁺, [FeF₄]^–.

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By means of spectrophotometric and conductometric measurements the following coordination forms of iron(III) with azide-, thiocyanate-, cyanide- and fluoride ions were found in dimethyl sulfoxide: [Fe(N₃)₄]^–, [Fe(SCN)₆]^3–, [Fe(CN)₂]⁺, Fe(CN)₃, [Fe(CN)₄]^–, [FeF₂]⁺, [FeF₄]^–.

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Mit 4 Abbildungen     

Characterization of europium(III) carbonate complexes in simulated groundwater by solvent extraction

The complex formation of Eu(III) by bicarbonate/carbonate ions has been studied at 0.1 M ionic strength and 25°C using synergistic solvent extraction system of 1-nitroso-2-naphthol and 1,10-phenanthroline in chloroform. Concentrations of bicarbonate (5·10^–3 to 1·10^–1 M) and carbonate (5·10^–4 to 1·10^–2 M) ions in the aqueous phase have been varied in the pH range of 8.0 to 9.1 to simulate ground and natural water compositions. Under these conditions, the following species have been identified: Eu(HCO₃)²⁺, Eu(HCO₃)₂ ⁺, Eu(CO₃)⁺ and Eu(CO₃)₂ ^–. Their conditional formation constants (log ) have been calculated as 4.77, 6.74, 6.92 and 10.42, respectively. These values suggest that the carbonate complexes of Eu(III) are highly stable.     

Speciation of silicon and phosphorous using liquid chromatography coupled with sector field high resolution ICP-MS

Sector-field high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) has been used, at R=3000, to resolve spectral interferences caused by N₂⁺ and CO⁺ on ²⁸Si⁺, and NOH⁺ and NO⁺ on ³¹P⁺, thereby facilitating the speciation of these elements. Polydimethylsiloxanes (PDMS), ranging from 162 g mol⁻¹ to 16 500 g mol⁻¹, and their silanol breakdown products, have been separated by size exclusion and reverse phase chromatography, respectively, and detected using HR-ICP-MS. Detection limits (as Si) of between 12–30 ng ml⁻¹ and 0.1–4 ng ml⁻¹ were obtained for the PDMS and silanol compounds, respectively. Quantitative and reproducible methods have been developed for the analysis of four common organophosphorous pesticides in blood plasma, and inorganic phosphates in food, with detection limits of between 0.9–2 ng ml⁻¹ and 1–39 ng ml^−1, respectively.     

Bismuthiol I as an analytical reagent

Summary Bismuth and palladium have been determined volumetrically after precipitation as bismuthiol I complexes. From 0.1 N hydrochloric acid solutions they are separated from Fe²⁺, Al, Cr, Ce³⁺, Zr, Ti, Zn, Th, UO₂ ²⁺, Be, Mg, Mn, Co, Ni, alkalis, alkaline and rare earths.A mixture of tartrate or citrate and EDTA has been found to be useful for the separation of palladium at a p_H 3.5–8.5 from As, Zn, Bi, Sn⁴⁺, Sb, Fe³⁺, Tl⁺, Cu²⁺, Cd, Pb, Ru³⁺, Os⁴⁺, PO₄ ^3–, Ce⁴⁺, Ir⁴⁺, Rh³⁺, VO₃ ^–, CrO₄ ^2–, AsO₄ ^3–, WO₄ ^2–, MoO₄ ^2– and from all the other ions referred to above. Potassium iodide at p_H 6.0–8.0 and thiosulphate at 6–7 keep Ag, Pb, Hg²⁺ and Au³⁺, Ir⁴⁺, Os⁴⁺ respectively in solution and thus allow a selective precipitation of palladium.Hg²⁺, Pb, Cu²⁺, Ag, Tl⁺, Cd and Pd when present along with bismuth are first removed by the reagent and from the filtrate bismuth is estimated. Sn²⁺, Sb³⁺, Fe³⁺, F^–, VO₃ ^–, PO₄ ^3–, AsO₄ ^3– and CrO₄ ^2– interfere in bismuth determination while only Sn²⁺, Pt⁴⁺ and CN^– interfere in palladium estimation.     

Investigation of the complex formation of technetium with thiourea by spectrophotometry and electromigration

TcO ₄ ^– is reduced by thiourea /tu/ to Tc/III/ in 6N HCl. By capillar electrophoresis three different cations have been identified with electrophoretic mobilities of u=/4.3–4.8/x10^–4 u=/3.2–3.8/x10^–4, and u=/2.2–2.8/x10^–4 cm² v^–1s^–1. These species were assigned to complex cations [Tc/tu/₆]³⁺, [Tc/tu/₅Cl]²⁺, and [Tc/tu/₄Cl₂]⁺, respectively. [Tc/tu/₆]³⁺ was identified by spectrophotometry according to recently published data. [Tc/tu/₅Cl]²⁺ was isolated and chemically characterized. The formation of the monovalent cation [Tc/tu/₅Cl₂]⁺ was concluded from spectrophotometrical measurements.