Determination of nanogram amounts of boron in some antimony compounds

Summary A method has been developed for determining boron in antimony compounds in the range 10^–7–10^–6%. The method comprises the isolation of the boron by distillation as methyl borate and its determination fluorimetrically with dibenzoylmethane. For the three materials analysed, SbCl₃, Sb₂O₃, and SbCl₅, individual procedures of dissolution as well as distillation were developed. The results obtained are reproducible, the mean deviation being about 12% at boron concentrations of 10^–7–10^–6%.

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Zusammenfassung Ein Verfahren zur Bestimmung von 10^–7 bis 10^–6% Bor in Antimon-verbindungen wurde ausgearbeitet. Es umfaßt die Abtrennung des Bors durch Destillation als Methylborat und dessen fluorimetrische Messung mit Dibenzoylmethan. Für SbCl₃, Sb₂O₃ und SbCl₅ wurden jeweils eigene Arbeitsweisen der Auflösung und Destillation angegeben. Die Analysenergebnisse sind reproduzierbar; die mittlere Abweichung beträgt etwa 12% für Borkonzentrationen von 10^–7 bis 10^–6%.

     

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%.

     

The O–H···O, O–H···N and C–H···O hydrogen bonds in 1,4-dimethylpiperazine mono-betaine monohydrate

1,4-Dimethylpiperazine mono-betaine (1-carboxymethyl-1,4-dimethylpiperazinium inner salt, MBPZ) crystallizes as monohydrate. The crystals are orthorhombic, space group Pccn. Two MBPZ molecules and two water molecules form a cyclic oligomer, (MBPZ·H₂O)₂. The O–H···O and O–H···N hydrogen bonds are of 2.769(1) and 2.902(1) Å, respectively. The dimers interact with the neighboring molecules through the C–H···O hydrogen bonds of 3.234(1) Å. The piperazine ring assumes a chair conformation with the N(4)–CH₃ and N⁺(1)–CH₂COO⁻ groups in the equatorial position and the N⁺(1)–CH₃ group in the axial one. The FTIR spectrum is compared with that calculated by the B3LYP/6-31G(d,p) level of theory.     

An ab initio study of electronic spectra and excited-state properties of 7-azaindole in vapour phase and aqueous solution

The geometries of 7-azaindole (7AI), its tautomer (7AT), and 7AI–H₂O and 7AT–H₂O complexes were optimised in the ground state and some low-lying singlet excited states using the 3-21G basis set. Differences of total energies of the optimised ground and excited states and the vertical excitation energies of these systems were used to explain the observed electronic spectra. Effect of solvation of these systems in bulk water was studied using the polarized continuum model (PCM). The mode of binding of a water molecule in the S₂(n–π^*) excited state of 7AI was found to be quite different from those in its ground and π–π^* excited states. It is shown that crossing of the lowest two singlet excited-state potential surfaces S₁(π–π^*) and S₂(n–π^*) of 7AI occurs in the vapour phase under geometry relaxation while on interaction with water, the S₂(n–π^*) excited state is raised up appreciably going even above the S₃(π–π^*) excited state. Ground- and excited-state molecular electrostatic potential mapping was carried out, which led to valuable information regarding the nature of excited states of the above-mentioned systems.     

Complexation processes in KF-SbF<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system studied by calorimetric titration

Complexation in a KF-SbF₃-H₂O system is studied in a range of molar ratios of fluorides KF : SbF₃= (0.1–2) : 1 by calorimetric titration. The equilibrium formation constants of complexes KSb₂F₇, KSbF₄, and K₂SbF₅ (5.8×10⁵±800, 3.3×10⁴±500, and 1.9×10⁶± 950, respectively) and the changes in enthalpy (–31.75± 0.74, –28.15±0.44, and –25.5±0.64 J mol^–1, respectively) and entropy (4±7, –8±5, and –35±9 J mol^–1 K^–1, respectively) are determined. The thermodynamic stability of the antimony(III) fluoride complexes is found to increase on going from KSb₂F₇ to K₂SbF₅.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 168–171.Original Russian Text Copyright © 2005 by Kovaleva, Zemnukhova, Lebedeva, Fedorishcheva.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Kinetics and mechanism of the acid-catalyzed hydrolysis of [carbonatoethylenediamine(L)2cobalt(III)]+ ions

The kinetics of acid-catalyzed hydrolysis of the [Co(en)(L)₂(O₂CO)]⁺ ion (L = imidazole, 1-methylimidazole, 2-methylimidazole) follows the rate law –d[complex]/dt = {k ₁ K[H⁺]/(1 + K[H⁺])}[complex] (15–30 or 25–40 °C, [H⁺] = 0.1–1.0 M and I = 1.0 M (NaClO₄)). The reaction course consists of a rapid pre-equilibrium protonation, followed by a rate determining chelate ring opening process and subsequent fast release of the one-end bound carbonato ligand. Kinetic parameters, k ₁ and K, at 25 °C are 5.5 × 10^–2 s^–1, 0.44 M^–1 (ImH), 5.1 × 10^–2 s^–1, 0.54 M^–1 (1-Meim) and 3.8 × 10^–3 s^–1, 0.74 M^–1 (2-MeimH) respectively, and activation parameters for k ₁ are H₁ = 43.7 ± 8.9 kJ mol^–1, S₁ = –123 ± 30 J mol^–1 deg^–1 (ImH), H₁ = 43.1 ± 0.3 kJ mol^–1, S₁ = –125 ± 1 J mol^–1 deg^–1 (1-Meim) and H₁ = 64.2 ± 4.3 kJ mol^–1, S₁ = –77 ± 14 J mol^–1 deg^–1 (2-MeimH). The results are compared with those for similar cobalt(III) complexes.     

Lactones ofFerula gigantea

The following substances have been isolated from an acetone extract ofFerula gigantea B. Fedtsch.: a coumarin — umbelliferone, C₉H₆O₂, mp 230–233°C; and sesquiterpene lactones — talassin A, C₂₅H₃₀O₇, mp 188–191°C; malaphyllinin, C₂₄H₂₄O₇, mp 231–235°C; malaphyll, C₂₉H₃₂O₉, mp 212–213°C; and malaphyllin, C₂₆H₂₈O₉, mp 216–218°C. Structures have been proposed for three new sesquiterpene lactones on the basis of an analysis of their spectral characteristics.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. M. V. Lomonosov Moscow State University, Botanical Garden, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 490–495, July–August, 1979.     

Study of the fluorite–pyrochlore–fluorite phase transitions in Ln<Subscript>2</Subscript>Ti<Subscript>2</Subscript>O<Subscript>7</Subscript> (Ln=Lu,Yb, Tm)

The ordering processes in Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) are studied by X-ray diffraction, thermal analysis, infrared absorption (IR) spectroscopy, and electrical conductivity measurements. The coprecipitation method followed by freeze-drying was used for Ln₂Ti₂O₇ synthesis. The region of low-temperature fluorite phase existence is 600 °C<T<740 °C. The low-temperature fluorite–pyrochlore phase transition in Ln₂Ti₂O₇ takes place at ~740–800 °C. Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) have the structure of disordered pyrochlore with antisite Ln–Ti defects at 800 °C<T<1,100 °C.The high-temperature pyrochlore–fluorite transformation takes place in Tm₂Ti₂O₇, Yb₂Ti₂O₇, and Lu₂Ti₂O₇ in air at T>1,600 °C. The conductivity values are 5·10^–3 S/cm for Tm₂Ti₂O₇, 6·10^–3 S/cm for Yb₂Ti₂O₇, and 10^–2 S/cm for Lu₂Ti₂O₇ at 740 °C. This order–disorder transition leads to a 2 orders of magnitude conductivity growth and a 10–30 times permittivity increase in Ln₂Ti₂O₇ samples obtained at 1,700 °C.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

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.     

Core level photoemission spectroscopy and chemical bonding in Sr2Ta2O7

Electronic parameters of constituent element core levels of strontium pyrotantalate (Sr₂Ta₂O₇) were measured with X-ray photoelectron spectroscopy (XPS). The Sr₂Ta₂O₇ powder sample was synthesized using standard solid state method. The valence electron transfer on the formation of the Sr–O and Ta–O bonds was characterized by the binding energy differences between the O 1s and cation core levels, Δ(O–Sr) = BE(O 1s) − BE(Sr 3d_5/2) and Δ(O–Ta) = BE(O 1s) − BE(Ta 4f_7/2). The chemical bonding effects were considered on the basis of our XPS results for Sr₂Ta₂O₇ and earlier published structural and XPS data for other Sr- and Ta-containing oxide compounds. The new data point for Sr₂Ta₂O₇ is consistent with the previously derived relationship for a set of Sr-bearing oxides. The binding energy difference Δ(O–Sr) was found to decrease with increasing bond distance L(Sr–O).     

Evaluation of a chloramine-T-selective electrode for catalytic titration of silver and mercury(II) based on iodide-catalyzed chloramine-T reactions

Semiautomatic methods are described for the catalytic titrimetric determination of microamounts of silver and mercury(II) using a chloramine-T-selective electrode as monitor. The methods are based on the inhibitory effect of Ag(I) and Hg(II) on the iodide-catalyzed chloramine-T-arsenite and chloramine-T-H₂O₂ reactions. Microamounts of silver in the range 0.2–200 μg (1 × 10⁻⁷−1 × 10⁻⁴ M) and of mercury(II) in the range 0.1–200 μg (2.5 × 10⁻⁸−5 × 10⁻⁵ M) were determined using the chloramine-T-As(III) indicator reaction. Mercury(II) in the range 4–2000 μg (1 × 10⁻⁶−5 × 10⁻⁴ M) was also determined using the chloramine-T-H₂O₂ indicator reaction. The accuracy and precision were in the range 0.1–1%.     

High-temperature transport and electrochemical properties of YBaCo4O7+δ

The total conductivity of oxygen-hyperstoichiometric YBaCo₄O₇₊ is predominantly p-type electronic at oxygen partial pressures from 5×10⁴ Pa down to the phase decomposition limit, 10^–11–10^–4 Pa at 973–1223 K. The ion transference numbers, determined by the oxygen permeation and faradaic efficiency measurements at 1073–1223 K, vary in the range 3×10^–5–2×10^–4 and increase with temperature. The oxygen permeability of YBaCo₄O₇₊ ceramics, with overall level similar to that of K₂NiF₄-type cuprates, is mainly limited by the bulk ionic conduction. Heating above 1050–1100 K and redox processes under oxidizing conditions lead to a first-order transition accompanied with extensive oxygen losses from the lattice, resulting in decreasing total oxygen content from 8.5 down to approximately seven atoms per unit formula. Except for the variations associated with this transition, the electron–hole conductivity and Seebeck coefficient are essentially p(O₂)-independent within the phase stability limits. The use of different synthesis methods, namely the standard ceramic technique and the glycine–nitrate process, has no significant effect on the properties of YBaCo₄O₇₊ ceramics. The thermal expansion coefficients averaged at 600–1100 K in air are (7.3–7.6)×10^–6 K^–1. Porous YBaCo₄O₇-based cathodes show a very high electrochemical activity in contact with LaGaO₃-based solid electrolyte at 873–1073 K.     

Voltammetric study of the interaction of lomefloxacin (LMF)–Mg(II) complex with DNA and its analytical application

The voltammetric behavior of the LMF-Mg(II) complex with DNA at a mercury electrode is reported for the first time. In NH₃–NH₄Cl buffer (pH=9.10), the adsorption phenomena of the LMF–Mg(II) complex were observed by linear sweep voltammetry. The mechanism of the electrode reaction was found to be a reduction of LMF in the complex, and the composition of the LMF–Mg(II) complex is 2:1. In the presence of calf thymus DNA (ctDNA), the peak current of LMF–Mg(II) complex decreased considerably, and a new well-defined adsorptive reduction peak appeared at −1.63 V (vs. SCE). The electrochemical kinetic parameters and the binding number of LMF–Mg(II) with ctDNA were also obtained. Moreover, the new peak currents of LMF–Mg(II)–DNA system increased linearly correlated to the concentration of DNA in the 4.00×10⁻⁷–2.60×10⁻⁶ g ml⁻¹ range when the concentrations of LMF–Mg(II) complex was fixed at 5.00×10⁻⁶ mol l⁻¹, with the detection limits of 2.33×10⁻⁷ g ml⁻¹. An electrostatic interaction was suggested by electrochemical method.     

Mixed chloro-bromo complexes of ruthenium(IV)

Conclusions Using spectrophotometry the authors have investigated complexing in the system Ru(IV)-Cl^–-Br^–. They have identified the formation of mixed-ligand chloro-bromo complexes of Ru(IV) and determined the equilibrium constants of reactions of formation of the complexes [Ru₂OCl₇Br-(H₂O)₂]^2– and [Ru₂OBr₇Cl(H₂O)₂]^2–.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2186–2190, October, 1977.     

Solubility of Solid Pentane, 2-Methylbutane, and Cyclopentane in Liquid Argon at 87.3 K

The solubilities of solid pentane, 2-methylbutane (isopentane), and cyclopentane in liquid argon at 87.3 K have been measured by the filtration method. The C₅ hydrocarbon content in solution was determined using gas chromatography. The solubilities of the C₅ hydrocarbons in liquid argon at 87.3K vary from 0.61 × 10^–7 mole fraction for cyclopentane, to 1.37 × 10^–7 mole fraction for pentane, and 8.83 × 10^–6 mole fraction for 2-methylbutane. The Preston–Prausnitz method was used for calculation of the solubilities of solid C₅ hydrocarbons in liquid argon in the temperature range 84–110 K and in liquid nitrogen in the range 64–90K. The values of the solvent–solute interaction constant l ₁₂ were also calculated.     

Surface redox polymerized SPEEK–MO2–PANI (M = Si, Zr and Ti) composite polyelectrolyte membranes impervious to methanol

We reported sulfonated poly(ether ether ketone) (SPEEK, 61% degree of sulfonation)–metal oxides (MO₂:SiO₂, TiO₂ and ZrO₂)–polyaniline composite membranes. Metal oxides were incorporated into the swelled SPEEK membrane by sol–gel method and cured by thermal treatment. SPEEK–metal oxide membranes surfaces were modified with polyaniline (PANI) by a redox polymerization process. It was observed that water retention capacity of membrane was increased and methanol permeability was reduced due to synergetic effect of metal oxides and surface modification with polyaniline. These composite membranes showed extremely low methanol permeability (1.9–1.3 × 10⁻⁷ cm² s⁻¹), which was lower than till reported values either for SPEEK–metal oxide or SPEEK/PANI membranes. Relatively high selectivity parameter (SP) values at 343 K of these membranes, especially S–SiO₂–PANI and S–TiO₂–PANI, indicated their great advantages over Nafion117 (N117) membrane for targeting on moderate temperature applications due to the synergetic effect of MO₂ and PANI in SPEEK matrix. S–TiO₂–PANI and N117 showed comparable cell performance in direct methanol fuel cell (DMFC).     

Investigation of the spectral properties of a squarylium near-infrared dye and its complexation with Fe(III) and Co(II) ions

The spectral features of the squarylium near-infrared (NIR) dye NN525 in different solutions and its complexation with several metal ions were investigated. The absorbance maximum of the dye is λ=663 nm in methanol. This value matches the output of a commercially available laser diode (650 nm), thus making use of such a source practical for excitation. The emission wavelength of the dye in methanol is λ_em=670 nm. The addition of either Fe(III) ion or Co(II) ion resulted in fluorescence quenching of the dye. The Stern–Volmer quenching constant, K_SV, was calculated from the Stern–Volmer plot to be K_SV=2.70×10⁷ M⁻¹ for Co(II) ion. The K_SV value for Fe(III) ion could not be established due to the non-linearity of the Stern–Volmer plot and the modified Stern–Volmer plot for this ion. The detection limit is 6.24×10⁻⁸ M for Fe(III) ion and 1.55×10⁻⁵ M for Co(III) ion. The molar ratio of the metal to the dye was established to be 1:1 for both metal ions. The stability constant, K_S, of the metal–dye complex was calculated to be 3.14×10⁶ M⁻¹ for the Fe–dye complex and 2.64×10⁵ M⁻¹ for the Co–dye complex.     

Synthesis and conformational studies of palladium(II) complexes containing [PhP(O)NP(E)Ph]− (E=S or Se)

The ligands [Ph₂P(O)NP(E)Ph₂]⁻ (E=S I; E=Se II) can readily be complexed to a range of palladium(II) starting materials affording new six-membered Pd–O–P–N–P–E palladacycles. Hence ligand substitution reaction of the chloride complexes [PdCl₂(bipy)] (bipy=2,2′-bipyridine), [{Pd(μ-Cl)(L–L)}₂] (HL–L=C₉H₁₃N or C₁₂H₁₃N), [{Pd(μ-Cl)Cl(PMe₂Ph)}₂] or [PdCl₂(PR₃)₂] [PR₃=PPh₃; 2PR₃=Ph₂PCH₂CH₂PPh₂or cis-Ph₂PCH=CHPPh₂] with either I (or II) in thf or CH₃OH gave [Pd{Ph₂P(O)NP(E)Ph₂-O,E}(bipy)]PF₆, [Pd{Ph₂P(O)NP(E)Ph₂-O,E}(L–L)], [Pd{Ph₂P(O)NP(E)Ph₂-O,E}Cl(PMe₂Ph)] or [Pd{Ph₂P(O)NP(E)Ph₂-O,E} (PR₃)₂]PF₆ in good yields. All compounds described have been characterised by a combination of multinuclear NMR [31 P{1 H} and 1 H] and IR spectroscopy and microanalysis. The molecular structures of five complexes containing the selenium ligand II have been determined by single-crystal X-ray crystallography. Three different ring conformations were observed, a pseudo-butterfly, hinge and in the case of all three PR₃ complexes, pseudo-boat conformations. Within the Pd–O–P–N–P–Se rings there is evidence for π-electron delocalisation.     

Disubstituted Rubidium Orthoperiodate Rb2H3IO6: Crystal and Molecular Structures and Properties

The crystal and molecular structures of acid salt Rb₂H₃IO₆ were determined. The anion part of the structure is united via a hydrogen bonding system to form a layer parallel to the xy plane. The proton conductivity in the temperature range of 40–60°C was found to be 10^–7–5 × 10^–6 Ohm^–1cm^–1, E _a = 2 eV.     

Mixed Complex Salt [Cu4(SCN2H4)7(NO3)](NO3)(SO4) · 3.3H2O: Synthesis and X-Ray Diffraction Analysis

The complex salt [Cu₄(SCN₂H₄)₇(NO₃)](NO₃)(SO₄) · 3.3H₂O was synthesized via reaction of aqueous solutions of thiourea with copper nitrate at 80°C and studied using X-ray diffraction analysis. The conditions and reasons for the partial oxidation of thiourea to sulfate ions were established. The crystals are monoclinic: a = 12.6072(7) Å, b = 15.4265(8) Å, c = 22.108(1) Å, = 120.133(6)°, space group P2₁/c, Z = 4. The crystal structure consists of [Cu₄(SCN₂H₄)₇(NO₃)]³⁺ complex cations, SO₄ ^2–, and NO₃ ^– anions, and molecules of the water of crystallization. Three types of coordination of the Cu atom were distinguished in the structure: trigonal (Cu–S 2.213–2.279 Å), tetrahedral (Cu–S 2.315–2.459 Å), and trigonal–pyramidal (3+1) (Cu–S 2.26–2.288, Cu–O 2.68 Å). The NO₃ ligand was found to be orientationally disordered.