Gold as a hydrogen sensing electrode forin situ measurement of dissolved H2 in supercritical aqueous fluid

Potentiometric studies of the Au-YSZ(Hg/HgO) (YSZ=yttrium stabilized zirconia) cell were conducted to investigate the suitability of gold as a sensing element forin situ determination of dissolved H₂ in aqueous fluids at 375–400°C and 400 bars. Experimental results indicate that the gold electrode responds rapidly and reversibly to variations in dissolved H₂, even at H₂<0.1 mmol-kg^?1. Nernstian response of the cell to dissolved H₂ was demonstrated at 400°C and 400 bars $$\Delta E = 0.9815 + 0.0668 \log m_{H_2 } $$ In fact, the performance of the gold electrode compares well to that of platinum. Considering the well known difficulties of using platinoid metals in H₂S-bearing fluids, however, the gold electrode holds great promise forin situ measurement of dissolved H₂ in chemically complex natural hydrothermal fluids. The results also suggest that the Au-YSZ(Hg/HgO) cell can be used to determine the solubility behavior of H₂ in aqueous fluid at temperatures and pressures in the vicinity of the critical point of water. At present, such data are lacking, which severely constrains knowledge of the effect of temperature and pressure on the Henry's law constant of H₂ in water.     

Electrochemical Behavior of Electrode System (H2 + H2O + Ar), Pt/BaCe0.9Nd0.1O3–α Near Its Equilibrium Potential

The polarization conductance of the (H₂ + H₂O + Ar), Pt/BaCe_0.9Nd_0.1O_3– electrode system is studied at different partial pressures of hydrogen and water, temperatures, exposure times, and electrode structures. The polarization conductance is proportional to , exponent p depending on the cell exposure time in experimental conditions. The cell exposure lowers the electrode electrochemical activity, increases electrolyte resistance, and decreases effect of on the polarization conductance and electrolyte conductance. To a first approximation the polarization conductance is proportional to the neodymium concentration in the BaCe_{1 – x} Nd _x O_{3 –} phase (0.01 x 0.1). Possible routes of the electrode reactions are discussed. Rate-determining stages in parallel reactions of hydrogen ionization and oxygen ion discharge in the system are suggested.     

Komplexverbindungen von Germaniumsäure mit ÄDTE und ÄDTE-Analogen, 1. Mitt.: Äthylendiamintetraessigsäure

Zusammenfassung Die Verbindung GeY · 2 H₂O wird nach einem Verfahren dargestellt, das die Verwendung von flüchtigem GeCl₄ vermeidet und direkt von Germaniumsäure-Lösungen ausgeht. Der Komplex, der analysenrein anfällt, wird thermogravimetrisch untersucht. In Wasser gelöst, erweist er sich als einbasige Säure, H[Ge(OH)Y]. Die Dissoziationskonstante der komplexen Säure wird potentiometrisch bestimmt:K _c =3,99 · 10^–3 (pK _c =2,40). Die Stabilitätskonstanten der komplexen Säure sowie des komplexen Anions werden ermittelt: =6,27 · 10⁴ (log =4,80); =3,34 · 10⁴ (log =4,52) (25°C; Ionenstärke 0,1m).

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The complex compound GeY · 2 H₂O is prepared directly from germanic acid solutions, avoiding volatile GeCl₄. It has been submitted to thermogravimetric analysis. Dissolved in water, it proves to be a monobasic acid, H[Ge(OH)Y]. The dissoziation constant of the complex acid is determined potentiometrically:K _c =3,99 · 10^–3 (pK _c =2,40). The stability constants of the complex acid as well as of the complex anion are evaluated: =6,27 · 10⁴ (log =4,80); =3,34 · 10⁴ (log =4,52), at 25°C; ionic strength 0,1m.

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Mit 4 Abbildungen

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Herrn Prof. Dr.J. W. Breitenbach zum 60. Geburtstag gewidmet.     

Crystal structures and vibrational spectra ofMSnF6·6H2O(M=Fe,Co, Ni)

Summary Single crystal X-ray structural data (atT=300 K) are reported for CoSnF₆·6H₂O (rhombohedral; R{ie61-1}-C _3i ² ;a=9.735(7) Å,c=10.095(7) Å, =120°;Z=3;R=0.047) and for NiSnF₆· 6H₂O (rhombohedral; R{ie61-2}-C _3i ² ;a=9.697(1)Å,c=10.021(1)Å, =120°;Z=3;R=0.038). The two compounds are isostructural to FeSnF₆·6H₂O. IR and Raman spectroscopic data (atT=300 and 75 K) are reported for hydrated and for partially deuterated samples ofMSnF₆·6H₂O (M=Fe, Co, Ni). Two rather similar (OD) stretching frequencies and one (HDO) bending frequency of isotopically dilute HDO molecules are observed for either of the three compounds, which is consistent with one crystallographically distinct water molecule forming two different, but rather similar O ... F hydrogen bonds.

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Kristallstrukturen und Schwingungsspektren vonMSnF₆·6H₂O (M=Fe, Co, Ni)

Zusammenfassung Die Kristallstrukturen von CoSnF₆·6H₂O (rhomboedrisch; R{ie61-3}-C _3i ² ;a=9.735(7) Å,c=10.095(7) Å, =120°;Z=3;R=0.047) und von NiSnF₆·6H₂O (rhomboedrisch; R{ie61-4}-C _3i ² ;a=9.697(1)Å,c=10.021(1)Å, =120°;Z=3;R=0.038) wurden mittels Röntgen-Einkristalldaten (beiT=300 K) bestimmt. Die beiden Verbindungen sind isostrukturell zu FeSnF₆·6H₂O. IR- und Raman-Spektren vonMSnF₆·6H₂O (M=Fe, Co, Ni) wurden von Proben mit unterschiedlichem Deuterierungsgrad gemessen (beiT=300 und 75 K). Bei allen drei Verbindungen findet man für isotopenverdünnte HDO Moleküle zwei nur geringfügig unterschiedliche (OD)-Valenzfrequenzen und eine (HDO)-Deformationsfrequenz, was mit der Existenz von nur einer Art von Wassermolekülen mit zwei verschiedenen, aber doch sehr ähnlichen O ... F Wasserstoffbrückenbindungen übereinstimmt.

     

Kinetics and mechanism of the displacement of aqua ligands from cis-diaqua-bis(biguanide)chromium(III) by pyridine-2-aldoxime in EtOH-H2O mixtures

Kinetic and mechanistic studies of the displacement of aqua ligands from cis-[Cr(BigH)₂(H₂O)₂]³⁺ (BigH = H₂NC(NH)CHC(NH)NH₂) by pyridine-2-aldoxime (LH) in EtOH-H₂O mixtures, in the 30–45° C range, obey the following rate law over the 3.5–6.0 pH range,

ZumHunsdiecker-Abbau von 2-Acylcyclopropancarbonsäuren

2-Acylcyclopropane carboxylic acids (1) are degraded by aHunsdiecker reaction using red HgO/Br₂ to mixtures oftrans- andcis-2-bromo-cyclopropyl alkanones, the former being the major component. The starting materials may be easily prepared by reaction of stabilised S-ylides with ,-unsaturated oxo compounds or -acylvinyltriphenylphosphonium bromides.     

X-ray investigation of bis(2-dimethylaminomethylcyclopentadienylmanganesetricarbonyl)mercury: The reaction path of amine mercuration

The structure of the centrosymmetric complex {[(CO)₃MnC₅H₃(CH₂NMe₂)]₂Hg} (1), obtained in the reaction of {[C₅H₃(CH₂NMe₂)Mn(CO)₃]Li} with mercuric chloride, was determined by a diffractometric experiment (diffractometer, MoK radiation, R=0.027, in 2311 reflections). In the centrosymmetric molecule of compound (1) the Hg-C bond length [2.042(6) Å] is short compared with the mean value of 2.07 Å as a result of the contribution from conjugation in the system. The orientation of the dimethylaminomethyl substituent at position 2 of the cyclopentadienyl is favorable for the formation of a weak intramolecular secondary Hg...N bond [2.933(5) Å], which closes a five-membered chelate ring. Investigation of the geometry features of the structurally related molecules of the Q-HgX type [Q=L_nM(-C₅H₃-CH₂NMe₂), X=Cl or Q; L_nM=CpFe, (CO)₃Mn] makes it possible to propose a possible amine mercuration path for the investigated model molecules and to predict a dimeric structure of a molecular salt-type complex for the second unstable asymmetric product from the above-mentioned reaction.N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 117912 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 320–328, February, 1992.     

Substitution of aqua ligands fromcis-diaqua-bis(bipyridyl) ruthenium(II) by 1, 10-phenanthroline in aqueous medium

The kinetics of aqua ligand substitution fromcis-[Ru(bipy)₂(H₂O)₂]²⁺ by 1, 10-phenanthroline (phen) have been studied spectrophotometrically in the 35 to 50°C temperature range. We propose the following rate law for the reaction within the 3.65 to 5.5 pH range:

Dissociation Constants of Protonated Cysteine Species in NaCl Media

The sulfur-containing biomolecule, cysteine has a role in physiological and natural environment because of its strong interactions with metals. To understand these interactions of metals with cysteine, one needs reliable dissociation constants for the protonated cysteine species [ CH(CH₂SH)COOH; H₃B⁺]. The values of dissociated constants, p , for protonated cysteine species (H₃B⁺ H⁺ + H₂B, K ₁; H₂B H⁺ + HB^–,K ₂; HB^– H⁺ + B^2–,K ₃) were determined from potentiometric measurements in NaCl solutions as a function of ionic strength, 0.5–6.0 mol-(kgH₂O)^–1 and between 5, and 45°C. The equations

Crystal Structure of the Mixed-Ligand Compound [HgPhen{(C2H5)2NCS2}2] and the Character of Intermolecular Interactions in [MPhen{(C2H5)2NCS2}2] (M = Zn, Cd, Hg)

Single crystals of the mixed-ligand complex compound [HgPhen(Et₂NCS₂)₂] were obtained. The crystal structure of the compound was determined by X-ray diffraction analysis (CAD-4 diffractometer, Mo radiation, 3640 F _hkl , R = 0.0280). Triclinic crystals with cell parameters a = 10.308(2), b = 11.171(3), c = 11.552(2) , = 94.16(2), = 96.66(1), = 105.17(2)°, V = 1267.8(5) ³, Z = 2, d _calc = 1.774 g/cm³, space group . The structure is composed of discrete monomer molecules. The coordination polyhedron of the Hg atom is a distorted octahedron formed by four S atoms of the two cyclic bidentate Et₂ ligands and two N atoms of the cyclic bidentate Phen ligand. The character of interactions between [MPhen(Et₂NCS₂)₂] (M = Zn, Cd, Hg) molecules and their packing in the structure are considered.     

EQCM Study of Rhodium Anodic Dissolution in Sulfuric Acid

Rh anodic dissolution is studied in 0.5 M H₂SO₄ solution in the E range from 0.2 to 1.2 V (RHE) by means of EQCM, cyclic voltammetry, photometry, and XPS. Bright pure Rh electroplate 0.5 m thick on a gold sputtered quartz crystal electrode is used for electrochemical and microgravimetrical studies. It is found that the increase in Rh electrode weight during the anodic process is lesser than its decrease during the cathodic one. The difference is 120 ± 60 ng cm^–2. The electrode weight also decreases under open-circuit conditions, i.e. at E _{I = 0}. A linear relationship between the weight change and the charge exists for the anodic process. The presence of Rh(III) compounds in the solution and on the electrode surface is confirmed by a photometrical analysis and XPS measurements. It is assumed that the formation and reduction of Rh(OH)₃ phase on Rh electrode surface within E range investigated proceed according to equation Rh + 3H₂O [Rh(OH)₃]_s + 3H⁺ + 3e, where [Rh(OH)₃]_s is a surface layer of Rh(OH)₃ phase. is evaluated to be 0.6 V. Rh(OH)₃ partly dissolves in the electrolyte.     

Osmium liquid-phase catalysts for hydrogenolysis of saturated hydrocarbons and hydrogenation of arenes

Reduction of OsO₄ by molecular hydrogen in alkane (cycloalkane) or benzene (toluene) solution produces small-ligand clusters of osmium of composition Os_1.5–2.5. CH_0–2 with a particle size 10–40 Å and a specific surface area of 34–46 m²/g. Hydrogenation of dry catalyst produces methane. The small-ligand osmium clusters obtained effectively catalyze hydrogenolysis of alkanes and cycloalkanes at 100–150°C and =5 MPa and hydrogenation of benzene at 20°C and =0.1 MPa.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2428–2433, November, 1989.     

The enthalpy of solution of MgCl2 and MgCl2·6H2O in water at 25°C. I. The integral molar enthalpy of solution

The data for the relative apparent and integral molar enthalpy of solution, L and H _sol ⁱⁿ , respectively, were critically reviewed, for the magnesium chloride-water system at 25°C. The concentration dependence L(m) and the enthalpy of solution at infinite dilution H _sol ^o were determined calorimetrically at 25°C. Both results are in agreement with most of the small amount of data published previously. From the results of our measurements, and from the most reliable value for H _sol ^o of MgCl₂, the concentration dependence H _sol ⁱⁿ (m) at 25°C was derived, for MgCl₂·6H₂O. The enthalpy of the hydration

The effect of pressure on the ionization of water at various temperatures from molal-volume data1

The apparent molal volumes of dilute (0.002 to 1.0m) aqueous HCl and NaOH solutions have been determined at 0, 25, and 50°C and NaCl solutions at 50°C. The partial molal volumes ( ) of HCl, NaOH, and NaCl solutions have been determined from these apparent molal volumes and other reliable data from the literature. The partial-molal-volume changes ( ) for the ionization of water, H₂OH⁺+OH^–, have been determined from 0 to 50°C and 0 to 1m ionic strength from the partial molal volumes of HCl, NaOH, NaCl, and H₂O. The partial molal compressibilities ( for HCl, NaOH, NaCl, and H₂O have been estimated from data in the literature and used to determine the partial molal compressibility changes ( ) for the ionization of water from 0 to 50°C and 0 to 1m ionic strength. The effect of pressure on the ionization constant of water has been estimated from partial-molal-volume and compressibility changes using the relation from 0 to 50°C and 0 to 2000 bars. The results agree very well with the directly measured values.Contribution Number 1548 from the University of Miami.     

Crystal Structures and Properties of New Mixed-Ligand Complexes of Nickel(II) Diisobutyldithiophosphinate with Imidazole and 3,5-Dimethylpyrazole

The reaction of Ni{(i-C₄H₉)₂PS₂}₂ with imidazole and 3,5-dimethylpyrazole in ethanol gave paramagnetic (_ef = 3.02 and 3.11 BM) mixed-ligand complex compounds [Ni(Im)₂{(i-C₄H₉)₂PS₂}₂] (I) and [Ni(Pyr){(i-C₄H₉)₂PS₂}₂] (II). Single crystals were grown and the crystal structures of I and II were determined from X-ray diffraction data (CAD-4 diffractometer, Mo radiation, 1483 , R = 0.0344 for I and 2630 , R = 0.0486 for II). The crystals are monoclinic with cell dimensions a = 12.845(2), b = 10.250(1), c = 13.431(1) , = 115.89(1)°, V = 1591(1) ³, Z = 2, d _calc = 1.281 g/cm³, space group (for I); a = 11.152(3), b = 12.483(2), c = 23.389(4) , = 100.78(1)°, V = 3199(2) ³, Z = 4, d _calc = 1.191 g/cm³, space group (for II). The structures consist of discrete monomer molecules. The coordination polyhedron of the Ni atom is a compressed octahedron NiN₂S₄ (in I) and a tetragonal pyramid NiNS₄ (in II) formed by four S atoms of the two cyclic bidentate ligands i-Bu₂ and the N atoms of two monodentate ligands (Im molecules in trans-positions) or the N atom of the monodentate Pyr ligand in complexes I and II, respectively. The character of interaction between molecules I and II and molecular packing modes are considered. The electronic spectra of the complexes are consistent with the symmetry of chromophores found from X-ray data.     

Proton transfer in electrochemically active “solid hydroxide proton conductor-hydrogenated metal” heterostructures

The electrochemical activity of solid-state heterostructures containing a hydrogenated metal and a solid proton conductor is investigated in the temperature ranges of 360–458 K, 360–370 K, and 320–420 K. The eutectics KOH/NaOH or KOH/KOH · H₂O and the chemical compound KOH · H₂O were chosen as the proton conductor. The conductivity of these electrolytes is higher than 1 mS/cm and their activation energies lower than 0.4 eV. Proton conductivity of the electrolytes is established by the emf method and confirmed by the isotope effect (H?D) in the conductivities of KOH · H₂O and the high-temperature form of KOH/NaOH (the protium forms are ≈1.4 times higher). Anomalies in the temperature dependence of conductivity and heat capacity are characteristic of eutectics in the region of 360 ± 1 K, and this has an effect on the electrochemical properties of the PdH _x |KOH/NaOH|PdO _y and TiH _x |KOH · H₂O|C heterostructures. Transport of atomic particles of hydrogen—most likely protons—across (Pd/Ti)H _x |MOH heteroboundaries where MOH = KOH · H₂O, KOH/NaOH, KOH/KOH · H₂O has a reversible character, which is shown by isotope and impedance measurements. The importance of the self-organized microheterogeneous solid eutectics KOH/NaOH and KOH/KOH · H₂O for their high conductivity compared to NaOH, KOH, and KOH · H₂O taken individually is discussed.     

Influence of the temperature on the extraction of some lanthanides with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5

The extraction of Pr, Gd and Yb with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) diluted in CHCl₃, C₆H₆, and CCl₄ at 288 K, 298 K, 308 K, and 318 K has been investigated. A compound of the typeMe(PMBP)₃HPMBP is formed in the organic phase. The values of the thermodynamic constants as well as of the parameters H°, S° and G° have been determined.

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Der Temperatureinfluß auf die Extraktion einiger Lanthaniden mit 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolon

Zusammenfassung Es wurde die Extraktion von Pr, Gd und Yb mit 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolon (HPMBP) in CHCl₃, C₆H₆ oder CCl₄ als verdünnendes Lösungsmittel bei 288 K, 298 K, 308 K und 318 K untersucht. Es wird eine Verbindung des TypsMe(PMBP)₃HPMBP in der organischen Phase gebildet. Die thermodynamischen Konstanten und auch die Parameter H°, S° und G° wurden bestimmt.

     

Trace metal ion catalysis; kinetics and mechanism of oxidation of metol by hydrogen peroxide in the presence of iron(III) sulphate in acid perchlorate

The kinetics of oxidation of N-methyl-p-aminophenol (metol) by H₂O₂ in the presence of trace levels of Fe^III have been studied in an HClO₄ medium. The reaction mechanism is complex and the catalytic role of Fe^III in the sulphato form is indicated. The following rate law accounts for the experimental observations:

A Novel Lanthanum(III) Coordination Polymer Constructed by Bridging 3,5-Dinitrobenzoato Anions and π–π Interaction

The title compound, [La₂(H₂O)₄(C₇H₃N₂O₆)₆] _n (I), synthesized by the hydrothermal reaction of 3,5-dinitrobenzoic acid and 1,10-phenanthroline with La(ClO₄)₃ · 6H₂O crystallizes in the triclinic system, space group P with a = 9.566(2) Å, b = 12.126(3) Å, c = 14.214(3) Å, = 114.614(3)°, = 103.246(3)°, = 97.130(3)°, V = 1413.3(6) ų, Z = 2, R(F) = 0.0392 and wR(F ²) = 0.0425. In I, each La³⁺ ion is coordinated by six oxygen atoms of six carboxylate ligands and two oxygen atoms of two coordinated water molecules. The 3,5-dinitrobenzoato anions bridge the La(III) centers to form one-dimensional linear chains, and – interaction between the phenyl rings of 3,5-dinitrobenzoato anions of adjacent linear chains links the chains to engender a two-dimensional network.     

Komplexverbindungen von Germaniumsäure mit ÄDTE und ÄDTE-Analogen, 2. Mitt.: 1,2-Diaminopropan-N,N,N′,N′-tetraessigsäure; N-2-Hydroxyäthyl-1,2-diaminoäthan-N,N′,N′-triessigsäure

Zusammenfassung Feste 11-Komplexverbindungen von Germaniumsäure mit 1,2-Diaminopropan-N,N,N,N-tetraessigsäure und N-2-Hydroxyäthyl-1,2-diaminoäthan-N,N,N-triessigsäure werden dargestellt. Auf Grund von TG-, DTG-, DTA- sowie IR-spektroskopischen Untersuchungen wird ein Strukturvorschlag für die erhaltenen Verbindungen (GeY·2 H₂O, GeY, GeZ·H₂O, GeZ, GeX·H₂O, GeX ^*** abgeleitet.In wäßriger Lösung erweist sich GeZ·H₂O als einbasige Säure, H[Ge(OH)Z], mit einer DissoziationskonstanteK _c =3,15·10^–3 (pK _c =2,50±0,03) für 25° C, Ionenstärke 0,1m.Es werden die Stabilitätskonstanten der Komplexverbindungen H[Ge(OH)Z], [Ge(OH)Z]^– und GeX·H₂O in wäßriger Lösung bestimmt: (25° C, Ionenstärke 0,1 m).Mit 3 Abbildungen1. Mitt.:N. Konopik undP. Mészáros, Mh. Chem.99, 902 (1968).Auszugsweise vorgetragen auf der Jahrestagung des Vereines Österreichischer Chemiker am 5. Oktober 1967 in Wien. Vgl. Allgem. u. Prakt. Chemie18, 268 (1967).