سال:1382 | دوره: | شماره: |تعداد مقالات:10

The charge transfer (CT) complex formation of benzonitrile as acceptor with the aromatic donors o-, m-, p-xylene and ethylbenzene in CCl4 solutions is investigated by chemical shift measurements relative to an external reference. The equilibrium parameters, Q and ΔAD of their weak molecular complexes, as found numerically modified Cresswel- Allred (C-A) method, is compared with graphically Scatchard-Foster-Fyfe (Sc-F-F) method.

FT-SERS (Fourier Transform Surface Enhanced Raman Scattering) of adriamycin and its complex with DNA is reported. It is shown that in agreement with previous Raman studies the interaction of adriamycin with DNA takes place through an intercalation mechanism. The presence of a new band at 731 cm-1 suggests that ring D of adriamycin is not involved in the intercalation process.

The voltammetric characteristics of Mo (VI) oxinate at the mercury electrode, in the presence of tri-butylammonium perchlorate (tri-BAP) and piperidinium perchlorate (PP) + piperidine (P) as two different types supporting electrolytes, have been studied in chloroform. With the both supporting electrolytes a two electron irreversible process for the reduction of Mo (VI) oxinate was observed. Preceded by a solvent extraction of Mo (VI) oxinate in chloroform, the DP method was used for the determination of molybdenum. In the presence of 0.2 M tri-BAP as supporting electrolyte, the calibration graph was linear over the range 0.5 to 50 (M. and the detection limit was 0.16 (M about 10 times lower than the case of PP + P. The proposed method using Mo (VI) oxinate-tri-BAP system has been successfully applied for the determination of molybdenum in steel.

A kinetic-spectrophotometric procedure is reported for determination of trace amounts of Ag(I). This method is based on catalytic effect of silver ion on the oxidation of congo red by potassium peroxodisulphate at pH=3.4 and 30oC in the presence of 1,10-phenanthroline as an activator. The reaction was followed spectrophotometrically by measuring the rate of change in absorbance of congo red at 510 nm in the range of 30-330 seconds after initiation of the reaction. Silver can be determined in the range 2-100 and 100-1100 ng/ml with detection limit 1 ng/ml. Ten replicate analysis of a sample solution containing 8 ng/ml silver gave a relative standard deviation of 1.0%. This method was used for determination of silver in water and photographic plate samples.

In thermal cracking plants, it is desired to apply an optimal temperature profile along the reactor to minimize the operation cost. In this article a simulator is developed by the use of a mathematical model, which describes the static operation of a naphtha thermal cracking pilot plant. The model is used to predict the steady state profiles of the gas temperature and product yields. Using a dynamic programming technique, an optimal temperature profile along the reactor is obtained. The effects of operating variables such as steam to hydrocarbon ratio (S/HC), coil outlet temperature (COT) and feed flow rate on product yield are investigated. Pilot plant simulation results are compared with the industrial data and the results indicate that they follow the same trend.

The synthesis, spectroscopic and magnetic characterization of a series of new alkoxo bridged binuclear copper (II) compounds is described. All complexes have the general formula [Cu (µ-OR)(L)2]2(ClO4)2 • x H2O, in which µ-OR = CH3O , C2H5O or C3H7O , L = 2 amino 4 methylpyridine (abbreviated A4PIC) and 2 amino 5 methylpyridine ( abbreviated A5PIC). The title compounds all consist of dinuclear units with alkoxo bridging group. All complexes have been synthesized in one-step reaction, and characterized by elemental analysis, FTIR and electronic spectra and by magnetic properties. The compounds exhibit strong antiferromagnetic interaction at room temperature. The UV-Vis spectra shows three absorption bands, which can be attributed to d-d transition of copper (II) ion, ligand --> metal charge transiton and π --> π transition of the ligand. The IR spectra indicate Cu2O2 ring vibrations in 500-570 cm-1 range. The magnetic properties of the [Cu2(A5PIC)4)(O -CH3)2](ClO4)2 complex has been investigated in the 5-265 K range and a singlet triplet energy gap (-2J) of 126 cm-1 was observed.

A thin film of epinephrine (EP) was electrochemically deposited on the surface of glassy carbon electrode previously activated in NaHCO3 solution. The cyclic voltammograms of the modified electrode indicate that the surface confined EP is strongly dependent on the solution pH, as expected for quinone/hydroquinone functionalities. The EP-modified glassy carbon electrode exhibited catalytic activity towards the electrooxidation of hydrazine, which appeared as a reduced overpotential especially in pH = 7.5. The diffusion coefficient of hydrazine was estimated using chronoamperometry. The catalytic rate constant, Kh, of the modified electrode for the oxidation of hydrazine was determined using the cyclic voltammograms recorded at low scan rates as well as the RDE voltammetric approach. It has been shown that the EP-modified electrode can be used as an amperometric sensor in the analysis of trace amount of hydrazine with high sensitivity and good limit of detection (0.83 µM). Amperometry by EP-modified electrode was used for determination of hydrazine in boiler feed water and the accuracy of the results was verified by comparison with those obtained from standard ASTM method.

For beneficiation of converter slag, the role of surface phenomena on slag composition was studied. This work includes some experimental data, which were measured for basic oxygen steel (BOS) slag in Isfahan Steel Plant. All data were collected on site in the plant. The results support the idea that surface activity plays a major role in converter slag formation. It was also a new finding that Mg and S are strongly surface active in melt of converter slag. These findings contribute to better understanding of the slag composition. The ultimate aim of this work is to develop a novel practice, "molten flotation" for separating valuable constituents of converter slag.

A highly selective, sensitive, rapid and economical differential pulse polarographic method has been developed for the determination of trace amounts of antimony in various standard alloys and biological samples after adsorption of its 2-nitroso-1-naphthol-4-sulfonic acid - tetradecyldimethylbenzylammonium chloride on microcrystalline naphthalene in the pH range of 7.5-11.0. After filtration, the solid mass is shaken with 8-10 ml of 1 M hydrochloric acid (with preconcentration factor of 10) and antimony is determined by differential pulse polarography (DPP). Antimony can alternatively be quantitatively adsorbed on 2-nitroso-1-naphthol-4-sulfonic acid- tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column (with preconcentration factor of 30) and determined similarly. In this case, 1.5 µg of antimony can be cocentrated in a column from 300 ml of aqueous sample, where its cocentration is as low as 5 ng/ml. Characterization of the electroactive process included an examination of the degree of reversibility. The results show that the irreversibility of antimony. Various parameters such as the effect of pH, volume of aqueous phase, HCl concentration, reagent concentration, naphthalene concentration, shaking time and interference of a number of metal ions on the determination of antimony have been studied in detail to optimize the conditions for determination in standard alloys and standard biological samples.

Phosphoryl containing ligand tri-n-octylphosphine oxide (TOPO) in dichloromethane has been used as an extracting agent for tetravalent thorium and trivalent europium ions from their 1 M sodium nitrates. The equilibrium data reveal that both ions are extracted as the complexes at 1:3 metal/ligand ratio. The values of conditional extraction equilibrium constant (Kex) show the superior extractive properties of the ligand towards thorium than europium ions. The effects of solvent, type and concentration of the salting-out agent on the extraction abilities of the ligand are investigated. The influence of the temperature on the extraction of these ions from the sodium nitrate medium into 1,2-dichloroethane by TOPO is studied as a function of temperature in the range 20-40oC. The results show that the distribution ratios of thorium and europium ions decrease with the increase in temperature. Free energy (ΔGo), enthalpy ( ΔHo) and entropy (ΔSo) changes associated with the extraction process are evaluated from the distribution measurements.