Electrothermal atomic absorption spectrometric determination of copper and zinc in high-purity bismuth after thiocyanate extraction

Copper and zinc (0.01–1 μg g^?1)in high-purity bismuth are extracted together as their thiocyanate complexes into methyl isobutyl ketone and determined by atomic absorption spectrometry with a tungsten-strip atomizer. The concentrations of copper found by the proposed method agree well with the values obtained by similar atomic absorption spectrometric methods involving prior extraction of copper as its bathocuproine or diethyldithiocarbamate complex.     

The use of chemisorption technologies in separation of multicomponent mixtures of metal ions

The concept of using hemisorption technologies for selective removal of individual ions from multicomponent mixtures was suggested and practically confirmed. Results obtained in experimental separation of the Ni²⁺-Fe³⁺-Pb²⁺ mixture with phosphate sorbents are reported.     

Synthesis and Luminescence of Novel EuIII Complexing Agents and Labels with 4-(Phenylethynyl)pyridine Subunits

The synthesis of novel 4-(phenylethynyl)pyridine subunits containing H₂O-soluble complexing agents and their luminescence with Eu^III ions are reported. Ligands with high luminescence intensities as well as quantum yields were obtained. Also the prepared labeling reagents as antibody conjugates gave the highest quantum and luminescence yields reported for H₂O-soluble Eu^III labels.     

AB initio study of the HN2+ molecule ion and its dissociation products in ground and excited states

Non-empirical SCF and Cl calculations for the HN₂⁺ molecule ion are reported. Potential curves for ground and excited states of this system are obtained, with particular emphasis on the manner in which these species dissociate upon NH stretch. The electronic spectrum of HN₂⁺ is also calculated and compared with that of an unperturbed N₂ molecule.     

Measurement of mutual diffusion coefficients,densities, viscosities,and osmotic coefficients for the system KSCN-H2O at 25°C

Mutual diffusion coefficients measured on the volume-fixed frame of reference are reported for KSCN-H₂O at 25°C over the concentration range 0.0 to 10.26 mol-dm^–3. The diffusion coefficient at infinite dilution was obtained from limiting ionic equivalent conductances of K⁺ and SCN^–. Low concentration conductances of KSCN-H₂O at 25°C used to obtain the limiting ionic equivalent conductance of SCN^– are reported. Values of density and viscosity for this system are reported from 0.0 to 10.30 mol-dm^–3. Osmotic coefficienss of KSCN-H₂O at 25°C were measured by the isopiestic method. These are reported over the concentration range of 0.30 to 24.94 molal (saturation). Values of thermodynamic diffusion coefficients for the concentration range 0.0 to 10.26 mol-dm^–3 are tabulated. Results are compared to other potassium salts with monovalent anions at 25°C.     

The correlation between weight loss and phase composition of the calcination products of gypsum

The thermodynamic parameters for the interaction of H⁺ and Na⁺ with citrate, tartrate and malate are determined potentiometrically and calorimetrically in aqueous solution. The investigation is carried out at various ionic strengths and temperatures. The data obtained by direct calorimetry are reported for the first time. The species NaA and NaHA are found to exist for tartrate and malate only, whereas the species NaH₂A is found to be present for citrate also. Simultaneous analysis of the potentiometric and calorimetric data enables the temperature and ionic strength dependence of the equilibrium parameters to be obtained for the complexes.     

Cycloadditionsreaktionen der aminofluorsilane

Aminofluorsilanes are obtained by the reaction of fluorosilanes with the lithium salts of the corresponding amines. The reaction of aminofluorosilanes with butyllithium in a (2 + 2)cyclo addition reaction leads to the formation of fourmembered silicon-nitrogen ring compounds. The mechanism of the reaction is discussed, the mass, ¹H and ¹⁹F NMR spectra of the compounds are reported.     

Ultraviolet spectroscopic study of ferric equilibria at high chloride concentrations

The equilibria among the species Fe³⁺, FeCl²⁺, FeCl₂ ⁺, FeOH²⁺ and Fe(OH)₂ ⁺ have been examined by ultraviolet absorption spectroscopy. Our results indicate that previous workers have generally overestimated the stability constant of FeCl²⁺ and that the association of Fe³⁺ and Cl^– is predominantly inner sphere. The formation constant of FeOH²⁺ obtained in 0.68 m NaCl is in good agreement with our earlier results obtained in 0.68 m NaClO₄. Our results indicate that formation of FeOHCl⁺ is much less significant than has been previously reported. Molar absorptivities for the species Fe³⁺, FeCl²⁺, FeCl₂ ⁺ and FeOH²⁺ are reported for wavelengths between 220 and 400 nanometers.     

Long range phenomena—XIV: 1H-{1H} indor spectra and relative signs of coupling constants of some oxirane derivatives with adjacent methylene groups

PMR parameters of some methylene substituted oxiranes are obtained from INDOR experiments on the ABXMN spin systems. Compounds investigated include safrol- and bromosafrol epoxide and β-phenoxypropylene oxide. For the latter compound all the relative signs (except for some long range couplings) were obtained and certain of these are in contradiction with those reported ² in β-chloropropylene oxide. ‘Non-classical’ long range coupling is also noted and differs in pathway from that reported previously.².     

Amperometric tetrathiafulvalene-mediated lactate electrode using lactate oxidase absorbed on carbon foil

The features of a new sensor for determining l-lactate are reported. The enzyme lactate oxidase and the mediator, tetrathiafulvalene (TTF), are absorbed on carbon foil disks previously bonded onto the ends of glass tubes. Linear calibration graphs were obtained in the range 10^?4?10^?3 M with physiological phosphate buffer (pH 7.35) and at 30°C with a response time of a few seconds. Calibration graphs in the range 10^?3?10^?2 M were also obtained and the difference in response times between these two ranges were investigated. The results are promising for assembling disposable lactate sensors for in vitro or for in or ex vivo measurements.     

Discussion of thermodynamic data obtained by adsorption gas chromatography of hydrocarbons on carbograph 4

Summary A new graphitized carbon black, Carbograph 4, with a specific surface area of 240 m² g⁻¹ was studied in terms of enthalpy, entropy and free energy of adsorption, determined by gas chromatographic method on a series of alkanes (C₂−C₆) and on benzene. The changes in the isosteric heat and entropy of adsorption when a non-polar stationary phase (squalane) was added to the adsorbent were also investigated. The data obtained are discussed and compared to those present in the literature for other graphitized carbon blacks. Some examples of separations obtained with Carbograph 4 are reported.     

Calculation of some nitrogen nuclear screening constants

Some nitrogen screening constants and their anisotropies are calculated within the CNDO/S level of approximation. Satisfactory agreement is found with available experimental data in most cases. In general the reported results are in closer agreement with experiment than are those found from ab initio calculations. The calculated data for the isoelectronic molecules N₂O and CH₂N₂ would be in better agreement with experiment if the assignments of the two nitrogen nuclei were reversed in both cases. A reasonable correlation is obtained with some observed nitrogen chemical shifts. Contributions arising from electronic transitions are reported for N₂, HCN, CH₃CN, CH₃NC, NO₂⁺ and NO₂^?.     

Nonmonotonic Transient Potential Signals with an 18‐Crown‐6 based Ion‐Selective Electrode in a Flow‐Injection System

The dynamic potential response of an 18‐crown‐6 based ion‐selective electrode towards Li⁺, Na⁺, K⁺ and Ca²⁺, in a flow‐injection system is studied. Different double nonmonotonic transient signals are obtained for the different ions. The influence of the flow‐injection variables and of ion concentration on the signals is studied. Two signal parameters, the relative return rates, are found to be characteristic for each ion and are constant for a concentration range of 1–3 decades. The nonmomotonic transient signals obtained are explained by reference to the theoretical models reported.     

SCF wavefunctions and energies for valence states and excited states of carbon and nitrogen

Wavefunctions and energies are reported for the (2s)ⁿ(2p)^m states of neutral carbon and nitrogen using the fixed double-zeta bases employed by Clementi to describe the ground state of these atoms. In addition, the wavefunctions and energies for a number of valence states are given, including the so-called sp³ valence state of carbon. Calculated energies of the valence states agree well with those obtained from experiment. The corresponding valence-state orbitals are useful in semi-empirical quatum-mechanical calculators, such as the maximum overlap method.     

Mobilities and ion-pairing in LiB(OH)4 and NaB(OH)4 aqueous solutions. A conductivity study

The conductivities of aqueous solutions of sodium borate at 25°C and lithium borate at various temperatures are reported. The conductivity of the B(OH) ₄ ⁻ ion is 35.3 ±0.2 S-cm²-mole⁻¹ at 25°C. The electrolytes are both associated, the lithium salt being more associated than the sodium salt. The mobilities and association constants obtained from the conductivity data agree with a model recently proposed for the H₂O−B(OH) ₄ ⁻ interactions. A discrepancy in the reported thermodynamic behavior of NaB(OH)₄ aqueous solutions has been resolved by means of the association constants obtained in the present study. Thus the usefulness of the conductivity measurements to determine excess chemical potentials of binary electrolytes in dilute solution is again shown.     

Absolute dipole oscillator strengths for photoabsorption,photoionization and ionic photofragmentation processes in HBr

Absolute dipole oscillator strengths (cross section) have been obtained for valence shell photoabsorption (7–100eV) and a variety of partial photoionization (11–40 eV) processes in gaseous HBr. Partial dipole oscillator strengths are reported for the formation of the X²Π, A²Σ⁺ and B²Σ electronic state of HBr⁺ as well as the respective photoelectron branching ratios. The photoelectron binding energy spectra show clear evidence of many-body effects in photoionization to the B²Σ state of HBr⁺ with the ionization oscillator strength divided over many bands as predicted by many-body Green's function calculations. Partial dipole oscillator strengths are also reported for molecular ion formation as well as for all dissociative ionization processes. The measurements have been made by the dipole (e,e) (e,2e) and (e,e + ion) methods, which respectively provide quantitative measurements of photoabsorption, photoelectron spectroscopy and photoionization mass spectrometry at continuously tuneable energies. The measurements of dipole oscillator strengths for production of electronic states of HBr⁺ are combined with those for molecular and dissociative photoionization. These, considered together with the ionization and appearance potentials, provide a quantitative dipole breakdown picture for the ionic photofragmentation pathways of HBr in the energy region up to 40 eV.     

Darstellung und reaktionen von 1,2-diaza-3-sila-5-Cyclopentenen

(Fluorosilyl)hydrazones are obtained from the reaction of lithiated hydrazones with fluorosilanes. On subsequent reaction with tert-butyllithium, cyclization takes place, to give 1,2-diaza-3-sila-5-cyclopentenes; this cyclization is favoured by the nitrogen-substituent of the hydrazone. The CH₂ group of the heterocyclic compounds is a nucleophilic centre, at which further substitutions are possible. The mass spec- trum and ¹H-, ¹⁹ F- and 2⁹Si-NMR spectra are reported.     

ERP-Untersuchungen an Oxovanadium(IV)-Bis-Komplexen mit 1,2-Dithioliganden

EPR Studies on Oxovanadium(IV) Bis-Complexes of 1,2-Dithio Ligands EPR investigations on oxovanadium(IV) bis-complexes containing the ligands 1,3-dithiol-2-thione-4,5-dithiolate, dmit^2?, 1,2-dithiol-3-thione-4,5-dithiolate, dmt^2?, and 1,2-dithiooxalate are reported. The parameters of the spin-Hamiltonian are used to characterize the bonding properties, and are compared with those obtained for the corresponding VOS₄ chelates containing four-membered chelate rings. According to this a successful characterization of VOS₄ type mixed-ligand complexes should be possible.     

Thermodynamic properties of peptide solutions. Part 15. Partial molar isentropic compressibilities of some glycyl dipeptides in aqueous solution at 15 and 35°C

The partial molar isentropic compressibilities at infinite dilution,K _s,2 ^o , have been obtained for eight glycyl dipeptides of sequence gly-X (X is an amino acid) in aqueous solution at the temperatures 15 and 35°C. The results have been combined with those obtained at 25°C, that were reported earlier, to evaluate the temperature dependences ofK _s,2 ^o for the dipeptides in the temperature range 15 to 35°C. TheK _s,2 ^o values for all the dipeptides are negative and increase (become more positive) with an increase in temperature. The slopes of the temperature dependences ofK _s,2 ^o for the dipeptides with typically hydrophobic side-chains are significantly larger than those for dipeptides with hydrophilic side-chains.