Polarographic determination of copper(II) after salting-out extraction as thiocyanate in acetonitrile

Summary A simple and sensitive extraction-polarographic method for the determination of copper(II) by use of acetonitrile as solvent is described. The copper(II) complex formed in aqueous solution can be quantitatively extracted into acetonitrile, in which the complex is reduced to give a polarographic wave withE _1/2–0.58 Vvs. SCE. Linear calibration curves for copper(II) are obtained by the dc, ac and differential pulse polarographic methods. Foreign ions such as Hg(II), Bi, Pb(II), Zn and Ni have no effect even in 20-fold amount relative to copper(II), but a 10-fold ratio of Sn(II) does interfere.

---

Zusammenfassung Ein einfaches und empfindliches Verfahren zur Extraktion von Kupfer (II) mit Acetonitril und darauf folgende polarographische Bestimmung wurde beschrieben. Der in wäßriger Lösung entstandene Cu(II)-Komplex läßt sich mit Acetonitril quantitativ extrahieren. Er wird dann reduziert und gibt eine polarographische Welle mit dem Halbwellenpotential E_1/2=–0,58 V gegen eine gesättigte Kalomelelektrode. Lineare Eichkurven für Kupfer(II) ergaben sich mit Gleichstrom-, Wechselstrom- und Differential-Puls-Polarographie. Fremdionen wie Hg(II), Bi, Pb(II), Zn und Ni beeinflussen das Ergebnis auch in 20fachem Überschuß nicht, wohl aber stört Sn(II) in 10facher Menge.

     

Negative ion mass spectra of salicylaldehydato and 2-hydroxy-1-naphthylaldehydato complexes of Co(II), Ni(II) and Cu(II): Consecutive and competitive eliminations of CO and H2CO

The negative ion mass spectra of some divalent metal complexes, ML₂, have been measured, where M?Co, Ni and Cu, and LH = salicylaldehyde or 2-hydroxy-1-naphthylaldehyde. All compounds yield intense molecular anions. The mass spectra of these compounds suggest that consecutive and competitive eliminations of CO and H₂CO, and various types of hydrogen migrations are involved in the fragmentation of the molecular anions. The mechanism of the fragmentation process and metastable peaks observed are also discussed.     

Application of the opal-glass method for ion-exchanger spectrophotometry

A simple and precise method for the measurement of the net absorbance of colored species sorbed on ion-exchange resins is reported. Identical opal-glass plates are inserted on the transmission sides of both the sample-cell and blank-cell compartments of the spectrophotometer. Absorbances of sample-resin layers are measured against a blank-resin layer as reference. Scattering effects caused by resin particles are almost eliminated by using opal glass. For the determination of chromium(VI) with diphenylcarbazide reproducible calibration lines were obtained without tedious compensation methods.     

Nonlinearity in cooperative systems-dynamical Bethe-Ising model

The dynamics of the short-range order as well as the long-range order in the nonlinear cooperative system is investigated specifically for a kinetic Ising model in the Bethe approximation. The phenomena of critical slowing down near the transition temperatureT _c and anomalous fluctuation belowT _c are directly related to the instability of the long-range order. The dynamics of the short-range order is essentially a fast mode and is noncritical. However, through the nonlinear coupling the short-range order is also influenced by the critical behavior of the long-range order.     

Generalization of analytic energy derivatives for configuration interaction wave functions

This paper takes the form of a review including some original contributions. A fresh derivation of analytic energy derivative expressions for configuration interaction (CI) wave functions is presented. In this method the CI energy is described by _IJC_IC_J(H _IJ-_IJE) so that the orthonormality condition is explicitly included therein. In the sequence of differentiations up to fourth order it will be demonstrated that each derivative may be expressed in terms of (H _IJ-_IJE) and its derivatives in a symmetric way with respect to the interchange of differential variables. In a similar manner, the CI variational condition may be described in an equation which explicitly includes the normalization condition. It is shown that the differentiation of the modified variational condition produces the coupled perturbed configuration interaction (CPCI) equations in directly soluble and compact forms. The necessary formulae for the energy derivatives up to fourth order and the CPCI equations up to second order are explicitly given.     

Surface flattening by annealing after molecular beam epitaxy growth revealed by in-situ secondary electron microscopy

The consecutive evolution of the configurations of islands, steps and terraces on a GaAs(001) surface during annealing after growth was studied by in-situ observation using a secondary electron microscope. Three unexpected processes were revealed: some large two-dimensional islands grow, although most small ones shrink, step distances becomes more uniform rather than step bunching occurring, and multilayer high islands shrink and disappear. The latter two processes play an important role in surface flattening. The growth of islands is explained by thermodynamic equilibrium.     

A structural investigation of calcium fluorosilicate glasses

The structure of x CaF₂(1?x)CaOSiO₂ glasses was investigated by X-ray photoelectron, F K_α emission X-ray and infrared absorption spectroscopies and ionic refraction of fluorine. A maximum in F_1s binding energy and a minimum in chemical shift of F K_α X-ray were found in the region of 7–10 mol% CaF₂, indicating that the state of fluorine changes. The ionic refraction of fluorine increased with increasing CaF₂ content up to 7 mol% CaF₂ and was nearly constant for compositions with more than 7 mol% CaF₂. There was practically no change in $\text{Ca}{}_{\mathrm{<mtext>2</mtext><mtext>p</mtext><mtext>(</mtext><mtext>3</mtext><mtext>2</mtext><mtext>)</mtext>}}$ binding energy for compositions with less than 7 mol% CaF₂. These data suggest that the fluorine ion bonds with a silicon predominantly for a CaF₂ content of less than 7 mol% and bonds with a calcium ion for increased CaF₂ content. Further, partial charges of fluorine, calcium and silicon, calculated by the modified Sanderson method could explain the chance of F_1s and $\text{Ca}{}_{\mathrm{<mtext>2</mtext><mtext>p</mtext><mtext>3</mtext><mtext>2</mtext>}}$ binding energies with composition. It is suggested that when the CaF₂ content is more than 7 mol%, the coordination number of fluorine increases and that of calcium decreases with increasing CaF₂ content.     

Substitutional doping of chemically vapor-deposited amorphous silicon

Dc conductivity, absorption coefficient, photoconductivity, and magnetoresistance of phosphorus-doped amorphous Si films prepared by chemical vapor deposition (CVD) have been measured as a function of doping ratio. These results indicate that phosphorus doping reduces localized states in the mobility gap, narrows the tailing width below the extended states, and that phosphorus donors form the impurity band at 0.15 eV below E_c at a doping ratio of about 1×10^-2. It is also found that electronic properties of CVD amorphous Si can be controlled in a wide range by substitutional doping of phosphorus atoms.     

Growth kinetics of amorphous hydrogenated silicon studied by pulsed rf discharge

The growth rate and hydrogen bonding configuration of a-Si:H prepared by a pulsed rf discharge technique were measured as a function of repetition frequency. The result was compared with the case of the gas-phase polymerization of monomers C₂H₂, C₂H₄, and C₂H₆ in a pulsed rf discharge. From distinct difference between the pulsed-plasma depositions of a-Si:H and C:H films, it is concluded that the growth of a-Si:H proceeds through the heterogeneous reactions among chemical species on the substrate surface.     

Protonation states of buried histidine residues in human deoxyhemoglobin revealed by neutron crystallography

The protonation states of buried histidine residues in human deoxyhemoglobin were unambiguously identified by using a neutron crystallographic technique. Unexpectedly, the neutron structure reveals that both the alpha- and beta-distal histidines (Hisalpha58 and Hisbeta63) adopt a positively charged, fully (doubly) protonated form, suggesting their contribution to the Bohr effect. In addition, the neutron data provide an accurate picture of the alpha1beta1 hydrogen-bonding network and allow us to observe unambiguously the nature of the intradimeric interactions at an atomic level.