Thermal decomposition of decavanadates of bivalent metals

The thermal decomposition of Cd₃V₁₀O₂₈ · 16H₂O and Mg₃V₁₀O₂₈ · 18H₂O has been investigated. It was found by means of IR spectroscopy and X-ray phase analysis that the final products of decomposition of the given compounds are V₂O₅, the corresponding metavanadates and the vanadium bronzes of cadmium and magnesium. Present and previous results allow conclusions on the thermal decomposition of decavanadates of bivalent metals.

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Zusammenfassung Die thermische Zersetzung von Cd₃V₁₀O₂₈ · 16 H₂O und Mg₃V₁₀O₂₈ · · 18 H₂O wurde untersucht. Durch IR-Spektroskopie und Röntgen-Phasenanalyse wurde festgestellt, daß die Endprodukte der Zersetzung der gegebenen Verbindungen V₂O₅ ist, entsprechend den Metavanadate und den Vanadiumbronze von Cadmium und Magnesium. Die gegenwärtigen und früheren Ergebnisse gestatten Folgerungen bezüglich der thermischen Zersetzung von Dekavanadaten zweiwertiger Metalle.

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Résumé On a étudié la décomposition thermique de Cd₃V₁₀O₂₈ · 16 H₂O et Mg₃V₁₀O₂₈ · · 18 H₂O. A l'aide des techniques de spectroscopie IR et de rayon X, on a établi que les produits finaux de la décomposition de ces composés sont V₂O₅, les métavanadates correspondants et les bronzes au vanadium, de cadmium et magnésium. Les résultats présents et antérieurs permettent de tirer des conclusions sur la décomposition thermique des décavanadates des métaux divalents.

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d₃V₁₀₂₈ · 16₂ Mg₃V₁₀O₂₈· 18H₂O. , , V₂O₅, . , , .

     

Fällungsanalyse im Mikrogrammbereich: Eine neue Methode

Zusammenfassung Eine neue Methode zur Durchführung gravimetrischer Bestimmungen im Mikrogrammbereich wurde beschrieben; diese beruht im wesentlichen darauf, daß der Niederschlag nicht mehr zusammen mit dem Filter, sondern nach Überführen mit einem geeigneten Lösungsmittel in einem separaten Wägegefäß gewogen wird.Die dazu nötigen Geräte und deren Herstellung wurden beschrieben. Nach dieser Methode wurden folgende Bestimmungen mit zufriedenstellender Richtigkeit durchgeführt: 2,5–25g Al, 5–50g Cu und 5–50g Zn mit Oxin, 2,5–25g Fe(III) und 2,5–25g Ti(IV) mit N-Benzoyl-phenylhydroxylamin, 5–50g Ni und 5–50g Cu mit Salicylaldoxim, 2,5–50g Co(II) und 2,5–50g Fe(III) mit -Nitroso--naphthol sowie 5–50g Chlorid als Silberchlorid.

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Precipitation analysis in the microgram-scale: A new method

Summary A new method for gravimetric determinations in the microgram-scale is described. This method is based on the fact that the precipitate is not weighed together with the filter but is transferred to a separate weighingvessel using a suitable solvent. The necessary simple devices and their use are described. The following determinations were carried out with satisfying accuracy: 2,5–25g Al, 5–50g Cu and 5–50g Zn with Oxine, 2,5–25g Fe and 2,5–25g Ti withN-benzoylphenylhydroxylamine, 5–50g Ni and 5–50g Cu with salicylaldoxime, 2,52–50g Co and 2,5–50g Fe with -nitroso--naphthol and 5–50g chloride as silver chloride.

     

Instability of potassium permanganate solubilized in organic solvents

The instability of the solutions of potassium permanganate solubilized in benzene, toluene and chloroform by the action of 15-crown-5, 18-crown-6, dibenzo-18-crown-6, tetra-butylammonium bromide and trilaurylmethyl ammonium bromide as phase-transfer catalysts, is reported. The kinetic parameters depend markedly on the catalyst used, the solvation of reactants is also important.

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, , 15- -5, 18- -6, -18- -6, , . .

     

The crystal structures of α, ω-diaminoalkanecadmium(II) tetracyanonickelate(II)-Aromatic molecule inclusion compounds. V. Toluidine clathrates of the hosts built of the diamines, 1,4-diaminobutane, 1.5-diaminonentane,and 1,8-diaminooctane

The crystal structures have been analyzed for the threeo-toluidine clathrates,catena-[catena--(1,4-diaminobutane)cadmium(II) tetra--cyanonickelate(II)]-o-toluidine(2/3),4-o,catena-[catena--(1,5-diaminopentane)cadmium(II) tetra--cyanonickelate(II)]-o-toluidine(3/4),5-o, andcatena-[catena--(1,8-diaminooctane)cadium(II) tetra--cyanonickelate(II)]-o-toluidine(1/1),8-o, for am-toluidine onecatena-[catena--(1,5-diaminopentane)cadmium(II) tetra--cyano-nickelate(II)]-m-toluidine(1/1),5-m, and for ap-toluidine onecatena-[catena--(1,8-diaminooctane)cadium(II) tetra--cyanonickelate(II)]-p-toluidine(1/1),8-p. 4-o crystallizes in the triclinic space groupP,a/Å = 9.806(3),b/Å = 14.388(3),c/Å = 7.725(2), /° = 89.71(2), /° = 89.96(2), /° = 98.12(2),V/ų = 1078.8(5),Z = 2, 3750 reflections,R = 0.056;5-o: tetragonalP4lmmm, (a = b)/Å = 7.485(7),c/Å = 10.06(3),V/ų = 563(2),Z = 1, 573 reflections,R = 0.19;8-o: monoclinicP2/m,a/Å = 11.513(4),b/Å = 7.626(1),c/Å = 7.101(1), /° = 109.63(3),V/ų = 587.2(2),Z = 1, 1682 reflections,R = 0.058;5-m: orthorhombicPbam,a/Å = 12.254(6),b/Å = 20.62(1),c/Å = 7.804(1),V/ų = 1972(1),Z = 4, 2240 reflections,R = 0.059; and8-p: triclinic,P,a/Å = 11.52(1),b/Å = 7.632(3),c/Å = 7.039(4), /° = 88.93(4), /° = 109.71(5), /° = 82.81(9),V/ų = 576.9(6),Z = 1, 2598 reflections,R = 0.042. Their structures are substantially similar to the already-known structure ofcatena-[catena--(1,6-diaminohexane)cadmium(II) tetra--cyanonickelate(II)]-o-toluidine(1/1): the guest toluidine molecules are accommodated in the cavities formed betweencatena-[cadmium(II) tetra--cyanonickelate(II)] layers bridged by the ambidentate ,-diaminoalkane ligands at the cadmium(II) atoms. The carbon chain length of the ,-diaminoalkane influences the number of cavities per formula unit and the deformation of the metal complex layers.     

Simultaneous determination of cobalt,nickel and iron by multi-wavelength spectrophotometry

A method for the simultaneous spectrophotometric determination of cobalt, nickel and iron based on the formation of their complexes with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide is proposed. The absorption curves of these complexes overlap severely in the scanning range 390–510 nm. The analyte concentrations are calculated by a least squares fit of the pure spectra to the mixture spectra, which therefore makes the simultaneous determination of these metallic ions possible without tedious pretreatment. The detection limits afforded by the proposed method range from 0.05 g/ml for Fe and Ni to 0.1 g/ml for Co. Root-mean-squared errors of prediction of 0.085 g/ml for Co, 0.048 g/ml for Ni and 0.1172 g/ml for Fe were obtained using the wavelength range 400–510 nm and 0.147 g/ml for Co, 0.107 g/ml for Ni and 0.127 g/ml for Fe using the wavelength range 420–434 nm. The effect of interferences is studied and the proposed method is applied to analysis for the above elements in synthetic samples and real samples, such as biological materials and alloys.     

Thermoanalytical investigations on the decomposition of double salts

The melting and decomposition behaviour of carnallite was investigated in the closed system under dynamic heating conditions and in the open system under dynamic and quasi-isothermal and quasi-isobaric conditions in the temperature range between 20 and 300°. DTA heating and cooling cycles in the closed system illustrate the incongruent melting of carnallite and the occurrence of different magnesium chloride hydrate phases. The thermal decomposition under quasi-isothermal and quasi-isobaric conditions begins at a pressure of at least 100 kPa from the melt and under reduced pressure from the solid. In any case KCl · MgCl₂ · 2 H₂O is formed which is decomposed to a basic product KMgCl_2.84–2.90(OH_0.10–0.16.

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Zusammenfassung Die Schmelz- und Zersetzungseigenschaften des Carnallits wurden im geschlossenen System unter dynamischen Heizbedingungen und im offenen System under dynamischen und quasi-isothermen und quasi-isobaren Bedingungen im Temperaturbereich von 20 bis 300°C untersucht. DTA Heiz- und Kühlzyklen im geschlossenen System verdeutlichen das inkongruente Schmelzen des Carnallits und das Auftreten verschiedener Magnesiumchlorid-Hydratphasen. Die thermische Zersetzung beginnt unter quasi-isothermen und quasi-isobaren Bedingungen bei einem Druck von mindestens 100 kPa aus der Schmelze und unter verminderten Druck aus der festen Phase. Die Zersetung verläuft stets über KCl · MgCl₂ · 2 H₂O zu einem basischen Produkt KMgCl_2.84–2.90(OH)_0.10–0.16.

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— -, - V 20–300°. . - - 100 , — . KCl · l₂ · 2 ₂, Kgl_2.84–2.90()_0.10–0.16.

     

Influence of oxygen compound structural elements of stretching vibration frequency of surface hydroxy groups

Stretching vibration frequencies of OH groups ( OH) in acidic oxygen compounds are determined by the electrostatic characteristics (E_p) of the polyhedron containing this group. Empirical dependence of OH various hydroxy groups on the number and nature of their binding cations is suggested.

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, OH- ( OH) (). .

     

Influence of the properties of an oxide film on the oxidation of aluminium powders

The structure of oxide films of aluminium powders has been established to depend on the size of its particles. The temperature dependence of the oxidation of the powder in air is ascribed to changes in both the structure of the oxide laver and the pressure of saturated aluminium vapor. The porous, permeable product consists of hollow microspheres of -Al₂O₃.

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. , . , –Al₂O₃.

     

Ammoxidation of 3- and 4-picolines over V2O5?SnO2/γ?Al2O3 catalyst

The ammoxidation of 3- and 4-picolines has been studied over V₂O₅–SnO₂/–Al₂O₃ catalysts prepared by surface impregnation technique. Best results were obtained for the generation of cyanopyridines in the temperature range 400–450°C and sub-stoichiometric value with respect to O₂. Catalysts that were calcined above 700°C showed no activity.

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3- 4- V₂O₅–SnO₂/–Al₂O₃, . 400–450°C O₂. , 700 K, .

     

Untersuchungen zur Bestimmung von Spurenelementen in Blutserum mit Hilfe der Totalreflexions-R?ntgenfluoreszenzanalyse

Summary The quantitative determination of trace elements in human blood serum by Total Reflection X-Ray Fluorescence Analysis (TXRF) is influenced by absorption- and reflection-effects caused by the organic (proteins) and inorganic (P, S, Na, K, Ca, Cl) matrices. To minimize these effects we have developed a sample preparation technique based on the decomposition of the organic matrix and followed by the separation of the trace elements from the organic matrix by ion-exchange. The described method enables the simultaneous determination of K (1584 g), Ca (666 g), Fe (22 g), Cu (9.6 g), Zn (8.8 g), Se (0.97 g), Sn (1.3 g), Pb (0.12 g) and Rb (1.6 g) (obtained values in parentheses).

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Herrn Prof. Dr. G. Tölg zum 60. Geburtstag gewidmet     

The oxidative addition of diphenylphosphine and monophenylphosphine to the electron-rich rhenium-rhenium triple bond. The isolation and characterization of compounds that contain the four-center Re(μ-X)(μ-PR2)Re cluster (X=halide)

Diphenylphosphine oxidatively adds to the ReRe bonds of Re₂ X ₄(-dppm)₂ (X=Cl or Br; dppm=Ph₂PCH₂PPh₂) and Re₂Cl₄(-dpam)₂ (dpam=Ph₂AsCH₂AsPh₂) to afford the dirhenium(III) complexes Re₂(-X)(-PPh₂)HX ₃(-LL)₂. The dppm complexes have also been prepared from the reactions of Re₂(-O₂CCH₃)X ₄(-dppm)₂ with Ph₂PH, and a similar strategy has been used to prepare Re₂(-Cl)(-PPh₂)HCl₃(-dmpm)₂ (dmpm=Me₂PCH₂PMe₂) from Re₂(-O₂CCH₃)Cl₄(dmpm)₂. Phenylphosphine likewise reacts with Re₂ X ₄(-dppm)₂ to give Re₂(-X)(-PHPh)HX ₃(-dppm)₂. An X-ray crystal structure determination on Re₂(-Cl)(-PPh₂)HCl₃(-dppm)₂ confirms its edge-shared bioctahedral structure. This complex crystallizes in the space group (No. 148) witha=21.699(3) Å, =84.50(4)°,V=10084(5) ų, andZ=6. The structure was refined toR=0.049 (R _w 0.069) for 5770 data withI>3.0(I). The Re-Re distance is 2.5918(7) Å. Oxidation of the bromide complex Re₂(-Br)(-PPh₂)HBr₃(-dppm)₂ with NOPF₆ produces the unusual dirhenium(III, II) cation [Re₂(-H)(-Br)[P(O)Ph₂]Br₂(NO)(-dppm)₂]⁺ which has been structurally characterized as its perrhenate salt, [Re₂(-H)(-Br)[P(O)Ph₂]Br₂(NO)(-dppm)₂]ReO₄ · 2CH₂Cl₂. This complex crystallizes in the space group (No. 2) witha=14.187(7) Å,b=16.419(5) Å,c=16.729(5) Å, =98.76(2)°, =110.11(3)°, =104.66(3)°,V=3414(6) ų,Z=2. The structure was refined toR=0.040 (R _w =0.051) for 5736 data withI>3.0(I). The presence of a phosphorus-bound [P(O)Ph₂]^– ligand, a linear nitrosyl and a bridging hydrido ligand has been confirmed. The Re-Re distance is 2.6273(8) Å.     

Structures of some lilioglycosides from the bulbs ofLilium regale

Six steroid glycosides, which gave been called lilioglycosides B, C, E, F, H, and I have been isolated from fresh bulbs ofLilium regale Wills. The structure of each compound has been determined by methods of physicochemical analysis. This is the first time that lilioglycosides B, C, H, and I, have been described; they are, respectively: (25S)-spirost-5-ene-3,27-diol3-O--D-glucopyranoside; (25R)-spirost-5-ene-3,27-diol3-O--D-glucopyranoside27-(3-hydroxy-3-methylglutarate); (25S)-spirost-5-ene-3,27-diol3-O-{[O--L-rhamnopyranosyl-(12)],[O--D-glucopyranosyl-(13)]--D-glucopyranoside}; and (25S)-spirost-5-ene-3,27-diol 3-O-{[O--L-rhamnopyranosyl-(12)],[O--D-glucopyranosyl-(13)]-O--D-glucopyranoside} 27-[(S)-3-hydroxy-3-methylglutarate].Institute of Genetics, Academy of Sciences of the Republic of Moldava, 2002, Kishinev, ul. Padurilor, 20. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 841–847, November–December, 1997.     

Chemical composition of T-21 silica tubing and implications for neutron activation analysis

T-21 silica, a commonly used encapsulation material in neutron activation analysis of small samples, was analyzed by INAA to determine trace levels of the following impurities: Na, Sc, Cr, Fe, Co, Ni, Zn, Br, Sb, La, Ce, Sm, Tb, Hf and Au. In the unprocessed form supplied by the manufacturer, pieces of T-21 weighing 50 mg contain 6·10^–2 g Na; 9·10^–3 g Fe; 3·10^–7–7·10^–6 g light REE, Sc and Hf and 4·10^–8 g Tb and Au. In a series of glass-blowing steps, in which unfiltered gases were used for fuel, and cleaning steps, in which reagent grade aqua regia was used, irradiation vials were produced which contain higher average levels of Sc, La, Sm, Tb and Hf, by factors ranging from 1.3 for Sm to 11.5 for La, and lower average levels of Co, Na and Fe, by factors of 1.4, 2.0 and 4.0, respectively, than the unprocessed material. These contamination levels lead to blank corrections of 21% for La, 2.6% for Ce and 3.0% for Hf in 40 g samples of refractory inclusions from carbonaceous chondrites, if counted in their irradiation vials.     

Path of “dry” electrons before localization in liquid hydrocarbons

Conclusions On the basis of measurements of values of in liquid hydrocarbons, it has been shown that the path length before localization of a photoliberated electron increases with increasing mobility of the excess electron, from approximately 40 Å (methylcyclohexane) to 200 Å (isooctane). In a liquid with10^–2 cm²/V·sec (methylcyclohexane, hexane), the localization takes place before or immediately after thermalization of the electron. In a liquid with>10^–1 cm²/V·sec, the electron passes through the main part of its path before localization, being in thermal equilibrium with the medium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2198–2203, October, 1985.     

Synthesis,characterization and crystal structures of heterometallic trinuclear carbonyl sulfido clusters (η5-Cp)MoFeCo- (CO)8(μ3-S) and [(η5-Cp)Mo]2Fe(CO)7(μ3-S)

HFe2Co(CO)9(3-S) reacts with (5-Cp)Mo(CO)3Cl in refluxing THF to give heterometallic trinuclear clusters (5-Cp)MoFeCo(CO)8(3-S) and [(5-Cp)Mo]2Fe(CO)7-(3-S), which have been characterized by elemental analyses, i.r., 1H- and 13C-n.m.r. and X-ray crystal structure determination. An electrophilic addition–elimination sequence is proposed for their formation.     

The oxidative addition of hydrogen sulfide to the electron-rich triple bond: The isolation and characterization of compounds that contain the Re2(μ-H)(μ-SH) cluster unit

The reactions of Re₂X₄(-dppm)₂ (X=Cl or Br; dppm=Ph₂PCH₂PPh₂) with H₂S in THF afford the dirhenium (III) complexes Re₂(-H)(-SH)X₄(-dppm)₂, the first examples of the oxidative addition of an S-H unit across an electron-rich metal-metal triple bond. The bromide complex Re₂(-H)(-SH)Br₄(-dppm)₂ (C₂H₅)₂O crystallizes in the space group P2₁/n witha=16.631(2) Å,b=15.967(3) Å,c=19.904(2) Å, =92.698(7)°,V=5279(2) ų, andZ=4. The structure which was refined toR=0.053 (R _w=0.070) for 4903 data withI>3.0(I), shows the presence of an edge-shared bioctahedral geometry with a very short Re-Re distance of 2.4566(7) Å. While the hydrogen atoms of the -H and -SH ligands were not located in the X-ray structure determination, their presence is confirmed by IR and¹H NMR spectroscopy.     

Application of l-cysteine-capped nano-ZnS as a fluorescence probe for the determination of proteins

Nanometer-sized l-cysteine-capped ZnS particles have been synthesized and used as a fluorescence probe to investigate the effect of proteins on fluorescent intensity. With =190 nm, maximum and constant synchronous fluorescence enhancement was produced at 267 nm and pH 5.12 in the presence of proteins. A highly sensitive synchronous fluorescence method for the rapid determination of proteins has been developed. Under optimum conditions, calibration graphs are linear over the range 0.03–8.0 g mL^–1 for bovine serum albumin (BSA), 0.01–6.0 g mL^–1 for human serum albumin (HSA), 0.05–8.0 g mL^–1 for -globulin (-G), and 0.04–4.0 g mL^–1 for ovalbumin, respectively. The relative standard deviations of seven replicate measurements were 1.75% for 1.0 g mL^–1 BSA, 1.90% for 1.0 g mL^–1 HSA, 1.65% for 1.0 g mL^–1 -G, and 2.32% for 1.0 g mL^–1 ovalbumin.     

n-Hexane dehydrocyclization on modified L-zeolite

Platinum dispersity and catalytic activity of L-zeolite-metal catalysts at 773 K have been studied depending on the nature of a modifying agent. The mean size of Pt particles is shown to decrease by a factor of 1.5–2 upon adding Re or W. No relation between Pt dispersity and activity in n-hexane dehydrocyclization has been revealed.

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773 L . 1, 5–2 Re W. -.

     

A new rectangular Re4 cluster compound of the metallocyclodiyne Type

The compound (n-Bu₄N)₂[Re₄Cl₈(-Cl)₂(-O)₂ · 2THF] has been prepared from (n-Bu₄N)₂ Re₂Cl₈ by refluxing it in wet trifluoroacetic acid. It forms brown, block-shaped crystals in space group P , withZ = 2 in a cell of dimensions:a = 11.748(1) Å,b = 16.847(3) Å,c = 16.953(3) Å, = 97.53(1)° = 106.49(1)° = 101.25(1)°V = 3093(1) ų. There are two independent but practically identical tetranuclear anions, each on a crystallographic inversion center. The short, unbridged Re-Re edges, to which triple bonds are assigned have lengths of 2.280(1) Å and 2.276(1) Å and the longer edges, each with a -Cl and a -O atom have lengths of 2.611(1) Å and 2.615(1) Å, for molecules 1 and 2 respectively. This anion completes a series going from [Re₄Cl₈(-O)₂(-OMe)₂]^2– through [Re₄Cl₈(-O)₂(-OMe)(-Cl)]^2– to the present [Re₄Cl₈(-O)₂(-Cl)₂]^2–. These metallocyclobutadiynes can be viewed as products of the 2,2-cycloaddition of two Re-Re quadruple bonds, but the mechanistic details of how they arise remain obscure.