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2002

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Articles 271 - 300 of 429

Full-Text Articles in Chemistry

Application Of Quantitative Structure-Retention Relationships (Qsrr) To A Set Of Organic Bromo And Nitrile Derivatives, Gustavo P. Romanelli, Juan Carlos Autino, Eduardo A. Castro Jan 2002

Application Of Quantitative Structure-Retention Relationships (Qsrr) To A Set Of Organic Bromo And Nitrile Derivatives, Gustavo P. Romanelli, Juan Carlos Autino, Eduardo A. Castro

Turkish Journal of Chemistry

The retention times are studied for two sets of 1-bromo-2-aryiloxyetanes and 3- aryloxypropiononitriles derivatives by means of Quantitative Structure-Retention Relationships (QSRR}). Five quantum mechanical molecular descriptors are used to calculate the regression equations. The fitting polynomials are computed in several-variable at first, second, and third order equations. Results are only significant when resorting to several-variable formulae which seems to point out the rather complex physical chemistry nature of the property under study.

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Flow Injection Extraction - Spectrophotometric Determination Of Bismuth With Di-(Hydrogenated Tallow Alkyl) Dimethylammonium Chloride, S. A. Barakat Jan 2002

Flow Injection Extraction - Spectrophotometric Determination Of Bismuth With Di-(Hydrogenated Tallow Alkyl) Dimethylammonium Chloride, S. A. Barakat

Turkish Journal of Chemistry

Bismuth(III) (0-25 \mu g/ml) is determined spectrophotometricaly at 513 nm after extraction into dichloromethane of the ion associate di-(hydrogenatedtallowalkyl)dimethylammonium tetraiodobismuthate. The reagent stream is distilled water, merged with 1.0 M sulfuric acid, 5% potassium iodide and 5% (w/v) ascorbic acid solution. The reagent stream is 0.2% (w/v) di-(hydrogenatedtallowalkyl)dimethylammonium chloride solution. The injection rate is 15 h^{-1}. The calibration graph is linear up to 25 \mu g/ml. The detection limit is 0.35 \mu g/ml Bi. The system is applied on water samples and copper-based alloys.

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Spectrophotometric Studies Of The Behavior Of P-Amino-N, N-Dimethyl Aniline With Ferric Nitrate In Methanol, Ali Hassoon Al-Taiar, Suhad K. Shubber, A. Megherbi Jan 2002

Spectrophotometric Studies Of The Behavior Of P-Amino-N, N-Dimethyl Aniline With Ferric Nitrate In Methanol, Ali Hassoon Al-Taiar, Suhad K. Shubber, A. Megherbi

Turkish Journal of Chemistry

The UV-visible absorption bands of the new complex were obtained using p-amino-N, N-dimethyl aniline as an electron donor with ferric nitrate as an electron acceptor in methanol at 25°C. The values of association constant K^{AD}, molar extinction coefficient \varepsilon^{AD}, and absorption band energy of charge transfer complex h \varepsilon_{CT} were calculated. The ionization potential of the donor I^{D}, was calculated from the complex band energy. The kinetics of the above association reaction were studied. This reaction was found to be a first order. The values of the rate constant of the forward reaction k_{1}, the rate constant of the reverse …

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A Study Of The Adsorption Of Phenol By Activated Carbon From Aqueous Solutions, Riaz Qadeer, Abdul Hameed Rehan Jan 2002

A Study Of The Adsorption Of Phenol By Activated Carbon From Aqueous Solutions, Riaz Qadeer, Abdul Hameed Rehan

Turkish Journal of Chemistry

A commercial active carbon was tested as an adsorbent for the removal of phenol from aqueous solutions. The optimum conditions for maximum adsorption in terms of shaking time, amount of the adsorbent, and concentration of the adsorbate were identified. The adsorption data fitted the Langmuir isotherm equation in the whole range of concentrations studied. The adsorption of picric acid, pyrogallol and salicylic acid at selected conditions for phenol was also studied. Elution studies to recover the adsorbed phenol from active carbon were performed with distilled water, NaOH and HCl solutions.

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An Indirect Lectin Affinity Bioassay For Uromodulin, Zeki̇ Topcu Jan 2002

An Indirect Lectin Affinity Bioassay For Uromodulin, Zeki̇ Topcu

Turkish Journal of Chemistry

Uromodulin is a monomeric glycoprotein excreted in large amounts in urine. Most of the assay methods for quantifying uromodulin rely on the availability of antibodies to this glycoprotein. This study reports a new bioassay for uromodulin without requiring the presence of antibodies. The bioassay is based on the lectin affinity of the glycoprotein and the known interaction between uromodulin and the tumor necrosis factor. The measuring range of the bioassay described in this paper is between 0.13 and 1.25 \mu g/ml, which makes it a potential method for clinical use.

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Efficient Synthesis Of 1-Alkoxycarbonyl-Methyl-2-Alkylpyrroles From Dichloro- And Methoxychloropropylalkyl Ketones, Raik A. Gadzhili, Raya A. Nadzhafova, Özge Şeşenoğlu Jan 2002

Efficient Synthesis Of 1-Alkoxycarbonyl-Methyl-2-Alkylpyrroles From Dichloro- And Methoxychloropropylalkyl Ketones, Raik A. Gadzhili, Raya A. Nadzhafova, Özge Şeşenoğlu

Turkish Journal of Chemistry

The condensation reaction of 2,3-dichloropropyl- and 2-methoxy-3-chloropropyl alkyl ketones with alkyl 2-aminoacetate salts leads to 1-alkoxy-carbonylmethyl-2-alkylpyrroles. These compounds, with various bases, gave 1-carbamoylmethyl-, 1-dialkylaminocarbonylmethyl-, 1-carbazoyl methyl-2-alkylpyrroles and potassium salt of 2-alkyl-pyrrolyl-1-acetic acid.

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Determination Of Ternary Mixtures Of Vitamins (B_{1}, B_{6}, B_{12}) By Zero-Crossing Derivative Spectrophotometry, Mahmure Üstün Özgür, İkbal Koyuncu Jan 2002

Determination Of Ternary Mixtures Of Vitamins (B_{1}, B_{6}, B_{12}) By Zero-Crossing Derivative Spectrophotometry, Mahmure Üstün Özgür, İkbal Koyuncu

Turkish Journal of Chemistry

A new method for determining ternary mixtures of vitamin B_{1}, B_{6} and B_{12} using second derivative spectrophotometry is described. The procedure is accurate, nondestructive and does not require any separation step or the solving of equations. Calibration graphs were linear up to 20 \mu gml^{-1} of vitamin B_{1} at 228.9 nm (r=0.9999), vitamin B_{6} at 309.6 nm (r=0.9999) and vitamin B_{12} at 361.7 nm (r=0.9998). The method was successfully applied for analyzing synthetic mixtures and commercial pharmaceutical preparations.

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The Effects Of Benzoic Acid In Chloride Solutions On The Corrosion Of Iron And Aluminum, Si̇bel Zor Jan 2002

The Effects Of Benzoic Acid In Chloride Solutions On The Corrosion Of Iron And Aluminum, Si̇bel Zor

Turkish Journal of Chemistry

In this work, the corrosion behavior of iron and aluminum was investigated in 0.1 M NaCl solutions with an initial pH value of 8 and containing various concentrations (0, 30, 150, 300 ppm) of benzoic acid. For this purpose, the anodic and cathodic semilogarithmic current-potential curves, weight loss and pH of the solution were determined over time. The changes in the concentrations of benzoic acid in the solutions with time were determined by a UV spectrophotometer. According to the results obtained in this investigation, benzoic acid in 0.1 M NaCl acts on iron and aluminum as an inhibitor. This effect …

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Simultaneous Determination Of Fe(Ii) And Fe(Iii) In Pharmaceutical Samples By Post-Column Derivatization/Hplc, Hami̇de Z. Şenyuva, Deni̇z Yurtsever Sarica, Tuncel Özden Jan 2002

Simultaneous Determination Of Fe(Ii) And Fe(Iii) In Pharmaceutical Samples By Post-Column Derivatization/Hplc, Hami̇de Z. Şenyuva, Deni̇z Yurtsever Sarica, Tuncel Özden

Turkish Journal of Chemistry

A post-column derivatization HPLC method with visible absorbance detection at 521 nm was modified for the simultaneous determination of Fe(II) and Fe(III) in mixtures. The method was applied to pharmaceuticals marketed in Turkey. Iron species were separated on a post-column derivatization HPLC, IonPac CS5A (4x250 mm) analytical column using a pyridine-2,6-dicarboxylic acid based eluent. The determinations of Fe(II) and Fe(III) were also realized by the most common method of FAAS, total iron determination. Detection limits (3S) were found to be 0.109 \mu g/L for Fe(II) and 0.217 \mu g/L for Fe(III), respectively. The mean recovery of the HPLC and AAS …

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Chemical Exfoliation Characteristics Of Karakoç Phlogopite In Hydrogen Peroxide Solution, Erol Üçgül, İsmai̇l Gi̇rgi̇n Jan 2002

Chemical Exfoliation Characteristics Of Karakoç Phlogopite In Hydrogen Peroxide Solution, Erol Üçgül, İsmai̇l Gi̇rgi̇n

Turkish Journal of Chemistry

The chemical exfoliation characteristics of phlogopite samples taken from Sivas - Yıldızeli-Karakoç (Turkey) ore were investigated. H_{2}SO_{4}, HCl, HNO_{3}, H_{3}PO_{4} and H_{2}O_{2} solutions at varying concentrations were tested for chemical exfoliation and the best reagent for this purpose was determined to be hydrogen peroxide. In the exfoliation tests performed, hydrogen peroxide concentration, temperature and reaction time were observed to be important parameters, with solid/liquid ratio being of minor importance. The exfoliation characteristics of the material increased with increases in hydrogen peroxide concentration and depending on the reaction time (1-30 hours) a maximum value of a 49-fold increase in swelling was …

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Phytochemical Studies At The Bulbs Of Ornithogalum Umbellatum L., Temi̇ne Şabudak, Ülkü Oyman Jan 2002

Phytochemical Studies At The Bulbs Of Ornithogalum Umbellatum L., Temi̇ne Şabudak, Ülkü Oyman

Turkish Journal of Chemistry

Phytochemical examination of the bulbs of Ornithogalum umbellatum L. led to the isolation a new steroidal compound. Its structure was determined to be 3-O-(2'-methoxy-4'-(2-pentenal))-phenyl sitosterol (1) by spectroscopic data and chemical evidence.

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Terpenoids And Aromatic Compounds From Euphorbia Heteradena, Sevi̇l Öksüz, Ayhan Ulubelen, Asli Barla, Wolfgang Voelter Jan 2002

Terpenoids And Aromatic Compounds From Euphorbia Heteradena, Sevi̇l Öksüz, Ayhan Ulubelen, Asli Barla, Wolfgang Voelter

Turkish Journal of Chemistry

Euphorbia heteradena Jaub. & Spach (Euphorbiaceae), a plant endemic to Turkey, has not been investigated previously. The CH_{2}Cl_{2} extract of the aerial parts of Euphorbia heteradena yielded 24-methylenecycloartanol, cycloart-25-en-3\beta ,24-diol, cycloart-22-en-3\beta ,25-diol, vomifoliol, vomifoliol 9-O-\beta -D-glucopyranoside, 3,4,3'-tri-O-methoxy ellagic acid, syringic acid and scopoletin. The structures of the isolates were identified by high field spectroscopic methods including 1D and 2D NMR techniques.

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Comparison Of Supercritical Fluid And Solvent Extraction Of Feverfew (Tanacetum Parthenium), Muammer Kaplan, Mark R. Simmonds, George Davidson Jan 2002

Comparison Of Supercritical Fluid And Solvent Extraction Of Feverfew (Tanacetum Parthenium), Muammer Kaplan, Mark R. Simmonds, George Davidson

Turkish Journal of Chemistry

High performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) analyses are used to show that supercritical fluid extraction (SFE) using carbon dioxide is an effective means of extracting a range of components from feverfew samples. It was found that the specific compositions of solvent extracts and SFE extracts are different. The amounts of the presumed active ingredient parthenolide have been confirmed to be very variable. Feverfew seeds were particularly rich in parthenolide, while dried powdered samples contained less and, in one case, none at all. The tunability of SFE has been demonstrated, and it was shown that successive extractions …

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Vapour Liquid Equilibrium In Asymmetric Mixtures Of N-Alkanes With Ethane, Anca Duta, Dan Geana Jan 2002

Vapour Liquid Equilibrium In Asymmetric Mixtures Of N-Alkanes With Ethane, Anca Duta, Dan Geana

Turkish Journal of Chemistry

The paper presents a vapour liquid equilibria study in binary mixtures of n-alkanes with high dimensional asymmetry. Each mixture contains ethane and alkanes higher than eicosane. Calculations were done using two equations of state, Peng-Robinson (PR) and Soave (SRK), in combination with van der Waals mixing rules, corrected with two interaction parameters. A limited temperature dependence of the interaction parameters was found. The correlations between the interaction parameters and the number of carbon atoms of the higher n-alkane led to equations valid for systems ethane + C_{3} up to C_{44}. The results of the prediction calculations were good, both with …

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The Simultaneous Determination Of Quinoline Yellow (E-104) And Sunset Yellow (E-110) In Syrups And Tablets By Second Derivative Spectrophotometry, Mahmure Üstün Özgür, İkbal Koyuncu Jan 2002

The Simultaneous Determination Of Quinoline Yellow (E-104) And Sunset Yellow (E-110) In Syrups And Tablets By Second Derivative Spectrophotometry, Mahmure Üstün Özgür, İkbal Koyuncu

Turkish Journal of Chemistry

A very simple spectrophotometric method using measurements at zero-crossing wavelength is described for resolving binary mixtures of the food dyes, Sunset Yellow (E-110) and Quinoline Yellow (E-104). Calibration graphs are linear up to 15.0 \mu gml^{-1} of Sunset Yellow (r = 0.9998), and Quinoline Yellow (r = 0.9999). The assay procedure for E-110 and E-104 in pharmaceutical products involves the extraction of the dyes with AcOH/NaOAc buffer solution (pH = 4.5), filtration, and measurement of the second derivative absorbance values at 410.0 nm for E-104 and 533.1 nm for E-110. This method was used for determining synthetic mixtures of these …

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Hplc Method For The Analysis Of Paracetamol, Caffeine And Dipyrone, M. Levent Altun Jan 2002

Hplc Method For The Analysis Of Paracetamol, Caffeine And Dipyrone, M. Levent Altun

Turkish Journal of Chemistry

An accurate, simple, reproducible and sensitive method for the determination of paracetamol, caffeine and dipyrone was developed and validated. Paracetamol, caffeine and dipyrone were separated using a \mu -Bondapack C _{8} column by isocratic elution with a flow rate of 1.0 ml/min. The mobile phase composition was 0.01 M KH_2PO_{4-} -methanol-acetonitrile-isopropyl alcohol (420: 20: 30: 30) (v/v/v/v) and spectrophotometric detection was carried out at 215 nm. The linear range of determination for paracetamol, caffeine and dipyrone were 0.409-400 \mu g/ml, 0.151-200 \mu g/ml and 0.233-600 \mu g/ml, respectively. The method was shown to be linear, reproducible, specific, sensitive and rugged.

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Synthesis And Protection Of Some Amidines, Kadi̇r Dabak Jan 2002

Synthesis And Protection Of Some Amidines, Kadi̇r Dabak

Turkish Journal of Chemistry

A series of benzamidine derivatives were synthesized from substituted benzonitrile compounds and protected with the tert-butoxycarbonyl group.

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Synthesis Of New Substituted 6-(Morpholin-4-Yl)-1h-Benzimidazole Derivatives, Canan Kuş Jan 2002

Synthesis Of New Substituted 6-(Morpholin-4-Yl)-1h-Benzimidazole Derivatives, Canan Kuş

Turkish Journal of Chemistry

A series of various substituted benzimidazole derivatives containing fluoro and morpholino substituents at the 5 and 6 positions was synthesized and their structures were identified by spectroscopic techniques.

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Synthesis, Characterization And Thermal Analysis Of Organotin(Iv) Derivatives Of 4-(N-Maleoyl)Butanoate, Khadija Shahid, Saqib Ali, Moazzam H. Bhatti, Muhammad Mazhar, Sohail Mahmood, Sadiqur Rehman Jan 2002

Synthesis, Characterization And Thermal Analysis Of Organotin(Iv) Derivatives Of 4-(N-Maleoyl)Butanoate, Khadija Shahid, Saqib Ali, Moazzam H. Bhatti, Muhammad Mazhar, Sohail Mahmood, Sadiqur Rehman

Turkish Journal of Chemistry

Organotin(IV) derivatives of the type R_{4 - n}SnL_{n} where R = Me, n-Bu, Ph, L = 4 - (N-maleoyl)butanoate and n = 1 or 2 were synthesized by refluxing R_{3}SnCl and R_{2}SnCl_{2} with (4-(N-maleoyl)butanoate in the presence of triethylamine using dry toluene as solvent. These compounds were characterized by IR, multinuclear NMR and mass spectrometry. We also studied their thermal behavior and calculated the degradation pattern, energy of activation (E_{a}) and order of reaction (n).

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Molecular Dynamics Simulation Of Phase Transitions In Binary Lj Clusters, Adem Teki̇n, Mi̇ne Yurtsever Jan 2002

Molecular Dynamics Simulation Of Phase Transitions In Binary Lj Clusters, Adem Teki̇n, Mi̇ne Yurtsever

Turkish Journal of Chemistry

The structures of small clusters are studied extensively by classical simulation methods because of their interesting thermodynamic behavior. In this work, we study the thermodynamic properties of binary mixtures of noble gas atoms. Interatomic interactions are defined by 6-12 Lennard-Jones (LJ) potential. Starting from the global minimum of the potential energy surfaces, the systems are heated by increasing the total energy until melting occurs. The melting is observed by monitoring the Lindemann factor. The effects of the relative sizes of A and B atoms and the interaction strength of A-A, A-B, and B-B on the melting temperature of clusters containing …

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The Second And Third Density Virial Coefficients Of Six Ar-Ne Mixtures At 25.0°C, Önder Korfali Jan 2002

The Second And Third Density Virial Coefficients Of Six Ar-Ne Mixtures At 25.0°C, Önder Korfali

Turkish Journal of Chemistry

In this paper we present a detailed experimental study of fractions, x_{Ar} = 0.0821, 0.2727, 0.3618, 0.5838, 0.7722 and 0.9049 at 25.0°C. The pressures are measured with a dead -- weight tester. The densities are determined from knowledge of the precise volume and weight measurement of the mixtures. Statistical analysis of the experimental data yielded very precise values for the second and third density virial coefficients. The second virial coefficients calculated with the least squares fitting method and corresponding to above argon mole fractions are 10^6B = 11.03, 9.16, 7.65, 1.83, -4.98 and --11.00 m^3mole^{-1}. Similarly the third virial coefficients …

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Determination Of Oxygen And Nitrogen Impurities In Magnesium Metal By Vacuum Distillation And Icp-Oes Techniques, Javed Akhtar, S. K. Durrani, N. A. Chughtai, M. Munir, Bashir Mohammad Jan 2002

Determination Of Oxygen And Nitrogen Impurities In Magnesium Metal By Vacuum Distillation And Icp-Oes Techniques, Javed Akhtar, S. K. Durrani, N. A. Chughtai, M. Munir, Bashir Mohammad

Turkish Journal of Chemistry

Due to the various promising properties of magnesium as a structural material and certain other applications such as a reducing agent for refractory metals, magnesium metal has great commercial importance in many technical industries but the presence of oxygen and nitrogen impurities adversely affects its physico-chemical and mechanical properties. Therefore, the exact measurement of oxygen and nitrogen impurities is essential. The accuracy of analytical values of micro amounts of nitrogen and oxygen (\mu g.g^{-1} level) in magnesium metal has been measured indirectly. The conditions for the vacuum distillation (VD) method were optimized. Analysis of residue for magnesium content was studied …

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A Spectrophotometric Method For The Determination Of Prazosin Hydrochloride In Tablets, Mahmure Üstün Özgür, Sidika Sungur Jan 2002

A Spectrophotometric Method For The Determination Of Prazosin Hydrochloride In Tablets, Mahmure Üstün Özgür, Sidika Sungur

Turkish Journal of Chemistry

A rapid and sensitive analytical method was developed for the spectrophotometric assay of prazosin hydrochloride. The method is based on the formation of a coloured derivative between the drug and 1,2-naphthoquinone-4- sulphonic acid sodium salt (NQS). The reaction proceeds quantitatively at pH 4.5 and 70°C for 40 min. After the extraction of the derivative with chloroform: n-butanol (3:1), the absorbance was measured at 400 nm. The method was applied to commercially available tablets and the results were statistically compared with those obtained by ultraviolet spectrophotometric and differential pulse polarographic methods using t- and F-tests.

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Determination Of Ascorbic Acid In Vegetables By Derivative Spectrophotometry, Zeynep Aydoğmuş, S. Müge Çeti̇n, Mahmure Üstün Özgür Jan 2002

Determination Of Ascorbic Acid In Vegetables By Derivative Spectrophotometry, Zeynep Aydoğmuş, S. Müge Çeti̇n, Mahmure Üstün Özgür

Turkish Journal of Chemistry

Determination of ascorbic acid (AA) in garlic, green pepper and chestnut was performed by derivative spectrophotometry without using any pre-separation or background correction techniques. The method is based on the measurement of the distances between two extremum values (peak-to-peak amplitudes) in second and third order derivative spectra of the extracts. Ten percent trichloroacetic acid was found to be the most suitable extraction solution. In the second order derivative spectrum the extrema of 253.2 and 259 nm for garlic, and in the third order derivative spectrum, the extrama of 256.4 and 261.6 nm for green pepper and chestrut samples were used …

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Determination Of Calcium, Magnesium And Aluminium In Magmatic Rocks After Ultrasonic Leaching By Flame Aas, M. Hi̇kmet Özkan, Mehmet Akçay Jan 2002

Determination Of Calcium, Magnesium And Aluminium In Magmatic Rocks After Ultrasonic Leaching By Flame Aas, M. Hi̇kmet Özkan, Mehmet Akçay

Turkish Journal of Chemistry

A method of ultrasonic leaching has been developed for the destructive analysis of magmatic rock samples^1. This method was applied to determine three new elements, Ca, Mg and Al, in magmatic rock samples. The accuracy of the ultrasonic leaching method (C_{ULM}) was tested using standard reference materials (SRMs) and the recovery ratio as K_1 = C_{ULM}/C_{SRM} was defined. Another recovery ratio, K_2, was also defined from the results of the conventional dissolution method (CDM), that is K_2 = C_{ULM}/C_{CDM}. The accuracy and precision of the method are comparable with those of conventional methods. The following recovery ratios were obtained for …

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Electrodeposition Of Zinc From Chloride Solution, Yanjerappa Arthoba Naik, Thimmappa V. Venkatesha, Perdur Vasudeva Nayak Jan 2002

Electrodeposition Of Zinc From Chloride Solution, Yanjerappa Arthoba Naik, Thimmappa V. Venkatesha, Perdur Vasudeva Nayak

Turkish Journal of Chemistry

The electroplating of zinc is carried out in the presence of 3,4,5-Trimethoxy benzaldehyde from a chloride bath. The bath constituents are optimized through Hull cell experiments. Operating parameters such as pH, temperature, and current density are also optimized. The current efficiency and throwing power are measured at different current densities. Polarization study is carried out under galvanostatic conditions. Corrosion resistance test indicated good protection of steel by the coating. The consumption of brightener is determined in the laboratory scale. SEM photomicrographs revealed fine-grained structure of the deposit from the optimum bath. IR spectrum of the scratched deposit showed inclusion of …

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The Effect Of Nicotinamide On Iron Corrosion In Chloride Solutions, Tunç Tüken, Bi̇rgül Yazici, Mehmet Erbi̇l Jan 2002

The Effect Of Nicotinamide On Iron Corrosion In Chloride Solutions, Tunç Tüken, Bi̇rgül Yazici, Mehmet Erbi̇l

Turkish Journal of Chemistry

The use of nicotinamide ``3-pyridineamide'' as an iron corrosion inhibitor was tested in aerated aqueous solutions of NaCl and Na_2SO_4 for different pH values. Polarization resistance (R_p) measurements, polarization curves and AC impedance spectroscopy techniques were used to obtain experimental data. Nicotinamide (ND) was found to exhibit a cationic-type inhibitor behaviour in acidic solution of NaCl (pH 3) and also a weak inhibitory effect in acidic sulphate solution (pH 3). The impedance spectra at open circuit potential showed that the corrosion process of the metal was characterized by two distinguishable capacitive loops. The charge transfer resistance (R_t) and the polarization …

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Novel Method For The Spectrophotometric Determination Of Isoniazid And Ritodrine Hydrochloride, Padmarajaiah Nagaraja, Kallanchira Sunitha, Ramanathapura Vasantha, Hemmige Yathirajan Jan 2002

Novel Method For The Spectrophotometric Determination Of Isoniazid And Ritodrine Hydrochloride, Padmarajaiah Nagaraja, Kallanchira Sunitha, Ramanathapura Vasantha, Hemmige Yathirajan

Turkish Journal of Chemistry

A simple, rapid and sensitive spectrophotometric method for the determination of isoniazid (INH) and ritodrine hydrochloride (RTH) in pure form as well as dosage forms is described. The method is based on the diazotisation of 4,4'-sulphonyldianiline (dapsone, DAP) followed by a coupling reaction with either INH or RTH in sodium hydroxide medium. Beer's law is obeyed in the concentration range of 0.5-20 \mu g ml^{-1} for INH at 440 nm and 0.5-18 \mu g ml^{-1} for RTH at 460 nm. The method is successfully employed for the determination of INH/RTH in pharmaceutical preparations and the results agree favourably with the …

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Non-Covalent Immobilization Of Quince (Cydonia Oblonga) Polyphenol Oxidase, Hülya Yağar, Ayten Sağiroğlu Jan 2002

Non-Covalent Immobilization Of Quince (Cydonia Oblonga) Polyphenol Oxidase, Hülya Yağar, Ayten Sağiroğlu

Turkish Journal of Chemistry

A partially purified polyphenol oxidase from quince (Cydonia oblonga) was immobilized on bentonite by simple adsorption at pH 6.8. The properties of the immobilized enzyme were compared to those of the free enzyme. Optimum pH and temperature were determined to be 9.0 and 45°C, respectively, showing the alteration of pH and temperature profiles by immobilization. No drastic change was observed in the K_m value after immobilization. Catechol, L-DOPA, p-cresole and pyrogallol were tested as substrates. Thermal and storage stability and reusability experiments were carried out. It was observed that the immobilized enzyme had storage stability for a period of one …

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Corrosion Of Reinforcing Steel In Concrete Immersed In Chloride Solution And The Effects Of Detergent Additions On Diffusion And Concrete Porosity, Hülya Kahyaoğlu, Mehmet Erbi̇l, Bi̇rgül Yazici, Ayşe Bahar Yilmaz Jan 2002

Corrosion Of Reinforcing Steel In Concrete Immersed In Chloride Solution And The Effects Of Detergent Additions On Diffusion And Concrete Porosity, Hülya Kahyaoğlu, Mehmet Erbi̇l, Bi̇rgül Yazici, Ayşe Bahar Yilmaz

Turkish Journal of Chemistry

In order to investigate the corrosion of reinforcing steel in concrete and the effects of chloride ions, oxygen diffusion and detergent additives of linear alkylbenzene (LAB) and linear alkylbenzene sulfonate (LAS), potentiokinetic experiments were carried out. Thus, by embedding steel electrodes into concrete specimens with a water/cement (W/C) ratio of 0.45, current-potential curves were obtained and the compressive strength of the specimens was measured. The electrochemical approach can be used to identify the effect of chloride on steel corrosion in concrete. It was found that the diffusion of chloride and oxygen through concrete and the reduction of oxygen on the …

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