Complexometric determination of aluminium in iron ore,sinter, concentrates and agglomerates

A method for the complexometric determination of aluminium in iron ore, sinter, concentrates and agglomerates encountered in international trade is described. The sample is fused in a zirconium crucible with a mixed flux of sodium carbonate and sodium peroxide. The fused mass is completely soluble in hydrochloric acid. The R₂O₃ oxides are then precipitated with ammonia and redissolved in hydrochloric acid. Elements such as iron, titanium and zirconium are separated from aluminium by solvent extraction with cupferron and chloroform. After removal of traces of organic matter from the aqueous phase, the solution is treated with an excess of EDTA, which is then back-titrated with zinc solution (Xylenol Orange as indicator). Addition of ammonium fluoride then releases EDTA equivalent to the aluminium and this is titrated with zinc solution. The method is rapid. The precision and accuracy are excellent, and the results comparable with those obtained by the referee method.     

Floating spherical Gaussian orbital model study of some hydrogen-bridged systems: LiBeH3, LiBH4, LiCH5, and BeBH5

The floating spherical Gaussian orbital (FSGO ) method has been used to study the equilibrium geometries and electronic structures of some hydrogen-bridged systems containing lithium, beryllium, boron, and carbon. The predicted geometries are in good agreement with other theoretical estimates. The binding energies for these hydrogen-bridged systems are estimated and discussed. The FSGO total energies (E_FSGO ), for all systems studied here, are found to be well correlated to nuclear–nuclear repulsion (V_nn) and nuclear–electron attraction (V_ne) terms by a relation of the type E_FSGO =\documentclass{article}\pagestyle{empty}\begin{document}$ {\textstyle{3 \over 7}} $\end{document} (2 V_nn + V_ne).     

Floating spherical gaussian orbital model study of some organometallic systems. I. LiCH3, HBeCH3, and CH3BeCH3

The floating spherical Gaussian orbital method has been used to study the equilibrium geometries and electronic structures of some organometallic systems like LiCH₃, HBeCH₃, and CH₃BeCH₃. The predicted geometries are in good agreement with other theoretical estimates and available experimental results. Electron transfer values from carbon to metal atom and bond energies of Li? C and Be? C bonds are estimated and discussed. The wave functions obtained here have also been used to predict the electron momentum distributions and Compton profiles for LiCH₃, HBeCH₃, and CH₃BeCH₃.     

Dynamics in a room-temperature ionic liquid: a computer simulation study of 1,3-dimethylimidazolium chloride

The transport properties and solvation dynamics of model 1,3-dialkylimidazolium chloride melt at 425 K is studied using molecular-dynamics simulations. Long trajectories of a large system have been generated and quantities such as the self-diffusion coefficient of ions, shear viscosity, and ionic conductivity have been calculated. Interestingly, the diffusion of the heavier cation is found to be faster than the anion, in agreement with experiment. The interaction model is found to predict a higher viscosity and lower electrical conductivity compared to experimental estimates. Analysis of the latter calculations points to correlated ion motions in this melt. The solvation time correlation function for dipolar and ionic probes studied using equilibrium simulations exhibits three time components, which include an ultrafast (subpicosecond) part as well as one with a time constant of around 150 ps. The ultrafast solvent relaxation is ascribed to the rattling of anions in their cage, while the slow component could be related to the reorientation of the cations as well as to ion diffusion.     

Determination of hexavalent plutonium using differential spectrophotometry

A differential spectrophotometric method has been developed for plutonium in hexavalent state using a double beam spectrophotometer. The absorbance measurements were made at 835 nm in 4M sulfuric acid using a 5 cm cell. In the method developed the absorbance of six Pu(VI) standards, taken in the sample cell, were recorded against a molybdenum blue solution of appropriate intensity in the reference cell. A least-squares fit of data on absorbance and concentration of plutonium standards gave slope F and intercept Co which were used to determine the unknown concentrations using the relationship, C=C₀+F·Ar where Ar is the absorbance of a plutonium solution of unknown concentration C mg/g. Various parameters like choice of acid and acidity, slit width, oxidant etc. were studied and the conditions optimized. Plutonium in the concentration range of 0.1–0.3 mg/g could be determined with a precision of ±0.5%. Uranium does not interfere. The method is useful for the analysis of a large number of samples on a routine basis.     

Effect of non-specificity in shape, size, and dielectric properties on electromagnetic extinction and optical field enhancement from spherical nanolayered metal-dielectric particles

Metal-dielectric composite nanospheres can amplify the scattering, emission, and absorption signature of molecules in their vicinity. Their ability to redistribute electromagnetic fields and produce pockets of greatly amplified fields is the dominant cause in achieving enhancement effects, for example, for surface-enhanced Raman spectroscopy. Extensive use of the field amplification has been made in devising ultrasensitive tag (label)?Cbased spectroscopic techniques. For example, we have recently proposed nano-layered alternating metal-dielectric particles (nano-LAMP)??a symmetric implementation of which is a nanoparticle consisting of alternating metal and dielectric shells. Exceptional spatial and spectral control on amplification can be achieved by designing the size and location of metal and dielectric layers in this geometry. Theoretical understanding exists and an engineering optimization approach can be adapted to design a palette of probes exploiting this control and tunability. However, current fabrication techniques are limited in their ability to achieve the required specificity in the spherical configurations. Hence, we investigate here the effects of variability, introduced by fabrication approaches into the structure of nano-LAMPs, on their spectroscopic signature. In particular, theoretical results are presented for the effects on enhancement due to variability in size, shape, and dielectric environment in the cases of gold?Csilica, silver?Csilica, and copper?Csilica nano-LAMPs. The results obtained show that the shape and dielectric properties of the metal shell play a crucial role in experimentally realizing the specificity of the magnitude of the enhancement and determine the key parameters to control and test in experimental validations.     

Highly dispersed Mn2O3−Co3O4 nanostructures on carbon matrix as heterogeneous Fenton-like catalyst

This work reports the synthesis of various carbon (Vulcan XC-72 R) supported metal oxide nanostructures, such as Mn₂O₃, Co₃O₄ and Mn₂O₃−Co₃O₄ as heterogeneous Fenton-like catalysts for the degradation of organic dye pollutants, namely Rhodamine B (RB) and Congo Red (CR) in wastewater. The activity results showed that the bimetallic Mn₂O₃−Co₃O₄/C catalyst exhibits much higher activity than the monometallic Mn₂O₃/C and Co₃O₄/C catalysts for the degradation of both RB and CR pollutants, due to the synergistic properties induced by the Mn−Co and/or Mn (Co)−support interactions. The degradation efficiency of RB and CR was considerably increased with an increase of reaction temperature from 25 to 45°C. Importantly, the bimetallic Mn₂O₃−Co₃O₄/C catalyst could maintain its catalytic activity up to five successive cycles, revealing its catalytic durability for wastewater purification. The structure–activity correlations demonstrated a probable mechanism for the degradation of organic dye pollutants in wastewater, involving •OH radical as well as Mn²⁺/Mn³⁺ or Co²⁺/Co³⁺ redox couple of the Mn₂O₃−Co₃O₄/C catalyst.