An on-line preconcentration/separation system for the determination of bismuth in environmental samples by FAAS

An on-line preconcentration procedure for the determination of bismuth by flame atomic absorption spectrometry (FAAS) has been described. Lewatit TP-207 chelating resin, including iminodiacetate group, packed in a minicolumn was used as adsorbent material. Bi(III) was sorbed on the chelating resin, from which it could be eluted with 3 mol L⁻¹ HNO₃ and then introduced directly to the nebulizer-burner system of FAAS. Best preconcentration conditions were established by testing different resin quantities, acidity of sample, types of eluent, sample and eluent solution volumes, adsorption and elution flow rates, and effect of interfering ions. The detection limit of the method was 2.75 μg L⁻¹ while the relative standard deviation was 3.0% for 0.4 μg mL⁻¹ Bi(III) concentration. The developed method has been applied successfully to the determination of bismuth in pharmaceutical cream, standard reference materials and various natural water samples with satisfactory results.     

Kinetics and mechanism of aqueous oxidation of H2S by Fe+3

The reaction kinetics of aqueous oxidation of H₂S by Fe⁺³ is investigated at 25°C by spectrophotometric method. The study conducted at various reactant concentrations and pH revealed that the reaction proceeds according to complex‐series reactions involving polysulfides as intermediates. The reaction of each step is first order with respect to Fe⁺³ and hydrogen sulfide or polysulfide. A mechanism is proposed, involving sulfido and polysulfido radicals. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 331–335, 1999     

Infrared spectra of Hoffmann-<Emphasis Type="Italic">T</Emphasis><Subscript><Emphasis Type="Italic">d</Emphasis></Subscript>-type benzene clathrates

Six new title compounds in the form of Cd(cyclobutylamine)₂M′(CN)₄ · 2G (M′ = Cd or Hg; G = benzene, 1,2-dichlorobenzene, or 1,3-dichlorobenzene) have been prepared in powder form. Their spectral data were found to be consistent with the structure of the Hofmann-T _d -type clathrates.     

Study of the structure and refractive parameters of diethylamine and triethylamine

The refractive index (n) and thermal coefficient of the refractive index (dn/dt) are measured at four wavelengths for the diethylamine and triethylamine. The measurements are carried out using the Bellingham+Stanley model 60/ED high-accuracy Abbe refractometer. The optical permittivity (ε) and its variation with temperature are calculated. Applying the Cauchy equation, the following refractive properties are obtained: the optical dispersion dn/dλ, the dielectric dispersion dε/dλ, the variation of -dn/dT, dε/dT, as a function of wavelength (λ), and Cauchy's constants against temperature. Additionally, molar refractivity versus temperature and wavelength are determined.     

Alternative approach in thermal analysis of plate heat exchanger

This paper presents alternative approach in heat transfer analysis of plate heat exchangers. In order to obtain heat transfer rate and effectiveness values of plate heat exchanger, neural network (NN) approach was used. Experimentally, system used in plate heat exchanger for heating and cooling applications was designed and constructed. Experimental data were used for training and testing network. The training and validation were performed with good accuracy. The correlation coefficient obtained when unknown data were applied to the networks was 0.9994 for heat transfer rate and 0.9976 for effectiveness, which is very satisfactory. Using the weights obtained from the trained network, a new formulation is presented for determination of heat transfer rate and effectiveness. This formulation can provide simplicity in thermal analysis of plate heat exchanger. The presented procedure can also help to heat exchanger designer and manufacturer.     

Three-to-one internal resonance in multiple stepped beam systems

In this study, the vibrations of multiple stepped beams with cubic nonlinearities are considered. A three-to-one internal resonance case is investigated for the system. A general approximate solution to the problem is found using the method of multiple scales （a perturbation technique）. The modulation equations of the amplitudes and the phases are derived for two modes. These equations are utilized to determine steady state solutions and their stabilities. It is assumed that the external forcing frequency is close to the lower frequency. For the numeric part of the study, the three-to-one ratio in natural frequencies is investigated. These values are observed to be between the first and second natural frequencies in the cases of the clamped-clamped and clamped-pinned supports, and between the second and third natural frequencies in the case of the pinned-pinned support. Finally, a numeric algorithm is used to solve the three-to-one internal resonance. The first mode is externally excited for the clamped-clamped and clamped-pinned supports, and the second mode is externally excited for the pinned-pinned support. Then, the amplitudes of the first and second modes are investigated when the first mode is externally excited. The amplitudes of the second and third modes are investigated when the second mode is externally excited. The force-response, damping-response, and .frequency- response curves are plotted for the internal resonance modes of vibrations. The stability analysis is carried out for these plots.     

Inkjet Printing of Functional Polymers and Materials: 2nd International Workshop in Eindhoven

This section contains reports on topical conferences. Reports are usually written at the request of the editorial office, but unsolicited contributions are also welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de.     

Improvement of cycling stability of LiMn2O4 cathode by Fe2O3 surface modification for Li-ion battery

The surface of spinel LiMn₂O₄ was modified with Fe₂O₃ (1.0, 2.0, 3.0, 4.0, and 5.0 wt%) by a simple sol-gel method to improve its electrochemical performance at room temperature. Compared with bare LiMn₂O₄, surface modification improved cycling stability of the material. Among the surface-modified cathode materials, the 3.0- and 4.0-wt% surface-modified cathodes have lesser capacity loss than the others. While the bare LiMn₂O₄ showed 25.4 % capacity loss in 70 cycles at room temperature, 3.0 and 4.0 wt% of Fe₂O₃-modified LiMn₂O₄ only exhibited the capacity loss of 2.6 and 2.3 % in 70 cycles at room temperature, respectively. The structure and phase were identified with X-ray diffractometer along with the lattice constant calculated by a Win-Metric program.     

Amalgamation performances of gold-coated quartz wool,alumina, silica,sand and carbon fiber for the determination of inorganic mercury in waters by cold vapor atomic absorption spectrometry

Different gold-coated sorbents for amalgamation were applied for the determination of inorganic mercury in waters using a home-made cold vapor generation unit coupled to atomic absorption spectrometry. Among the gold-coated materials investigated (quartz wool, alumina, silica, sand and carbon fiber) quartz wool was found to give the most efficient results in terms of sorption and release. Analytical performance of the system without and with amalgamation was investigated and it was found that when amalgamation was applied, the linearity and slope of the calibration plots were independent on the sample volume for 1.0, 5.0 and 10.0 mL. Method validation was realized through the analysis of a sample of spring water spiked with 1.0 μg/L inorganic mercury and the spike recoveries were found to be 95 ± 1, 91 ± 3, and 99 ± 5% for 1.0, 5.0, and 10.0 mL, respectively. The results demonstrated that the methodology can be applied to these types of samples directly or after amalgamation, depending on the mercury concentration.     

Synergistic effect of sonolysis and photocatalysis in the degradation kinetics of effluent solution

In this study, degradation of the effluent solution using sonolysis, sonocatalysis, photocatalysis and sonophotocatalysis was investigated. For this purpose, an artificial effluent solution (AES) containing Acid Black 1 and Acid Blue 62 dyestuffs was prepared. The initial AES concentration, catalyst amount, light intensity and the power of ultrasound energy were chosen as the reaction parameters.The degradation rate of AES followed the pseudo-first order kinetics inconcentration of artificial effluent solution. The results showed that the sonophotocatalysis (US + UV + TiO₂) was more effective in the degradation than sonolysis (US), sonocatalysis (US + TiO2) and photocatalysis (UV + TiO₂) performed individually. The highest and lowest degradation rates were obtained in sonophotocatalytic process and sonolytic process (US), respectively. It was found also that the synergistic effect between sonolysis and photocatalysis processes is the main reason why the maximum degradation is achievable in the sonophotocatalytic process.