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2002

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Articles 3001 - 3030 of 3435

Full-Text Articles in Physical Sciences and Mathematics

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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Alteration Of Three Turkish Bentonites By Treatment With Na_{2}Co}_{3} And H}_{2}So}_{4}, Nuray Yildiz, Ayla Çalimli Jan 2002

Alteration Of Three Turkish Bentonites By Treatment With Na_{2}Co}_{3} And H}_{2}So}_{4}, Nuray Yildiz, Ayla Çalimli

Turkish Journal of Chemistry

In this study, fine fractions of bentonites from the Çankırı and Kütahya regions were treated with Na_{2}CO_{3} and H_{2}SO_{4}. The resulting materials were analysed by X-ray diffraction (XRD), thermogravimetric and differential thermal analyses (TGA, DTA) and infrared (IR) spectroscopy. Surface areas of the samples were also measured. The results showed that structural changes were observed by treatment with Na_{2}CO_{3} and H_{2}SO_{4}. These changes showed differences depending on exchangeable cations, clay type and the ratio of additives.

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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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The Effect Of Acid Activation On Some Physicochemical Properties Of A Bentonite, Müşerref Önal, Yüksel Sarikaya, Tülay Alemdaroğlu, İhsan Bozdoğan Jan 2002

The Effect Of Acid Activation On Some Physicochemical Properties Of A Bentonite, Müşerref Önal, Yüksel Sarikaya, Tülay Alemdaroğlu, İhsan Bozdoğan

Turkish Journal of Chemistry

A white calcium bentonite (CaB) from the K\"{u}tahya region/Turkey was activated by heating it for 6 hours at 97°C in H_{2}SO_{4} solution. The mass percentage of H_{2}SO_{4} in the bentonite-acid mixture was varied from 0 to 70%. The chemical analysis (CA), cation exchange capacity (CEC), differential thermal analysis (DTA) curves and X-ray diffraction (XRD) patterns of the prepared samples were determined. The specific surface area (A) and the specific micropore-mesopore volume (V) were calculated respectively from the adsorption and desorption data of N_{2} obtained at liquid N_{2} temperature. How the calcium montmorillonite (CaM) layers in the CaB were decomposed during …

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Production Of Mesophase Pitch From Coal Tar And Petroleum Pitches Using Supercritical Fluid Extraction, Mustafa Zafer Özel, Keith D. Bartle Jan 2002

Production Of Mesophase Pitch From Coal Tar And Petroleum Pitches Using Supercritical Fluid Extraction, Mustafa Zafer Özel, Keith D. Bartle

Turkish Journal of Chemistry

Supercritical fluid extraction (SFE) is currently being investigated as a possible technique in the production of high quality mesophase pitch from coal tar and petroleum pitches. Mesophase pitch is used to make high technology products, such as carbon fibre. The conventional production of mesophase pitch initially involves the removal of low molecular weight species from coal tar and petroleum pitches. The remaining residue is then transformed into a mesophase pitch through a polymerisation process. The aim of this study involves the extraction of light molecular weight species using SFE. Both petroleum and coal tar pitch contain complex aromatic molecules with …

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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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Cadmium And Mercury Uptake By Immobilized Pleurotus Sapidus, Yağmur Yalçinkaya, M. Yakup Arica, Levent Soysal, Adi̇l Deni̇zli̇, Ömer Genç, Sema Bektaş Jan 2002

Cadmium And Mercury Uptake By Immobilized Pleurotus Sapidus, Yağmur Yalçinkaya, M. Yakup Arica, Levent Soysal, Adi̇l Deni̇zli̇, Ömer Genç, Sema Bektaş

Turkish Journal of Chemistry

Pleurotus sapidus} basidiospores immobilized onto Ca-alginate beads were used for the removal of cadmium and mercury ions from aqueous solutions. The biosorption of Cd(II) and Hg(II) ions on the alginate beads and both immobilized live and heat inactivated fungal mycelia of Pleurotus sapidus} was studied from aqueous solutions in the concentration range of 30-500 mg L^{ - 1}. The biosorption of Cd(II) and Hg(II) ions by the alginate and both live and heat inactivated immobilized preparations increased as the initial concentration of the ions increased in the medium. Maximum biosorption capacity for immobilized live and heat inactivated fungal mycelia of …

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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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Phenylethanoid Glycosides From Scutellaria Galericulata, Tayfun Ersöz, Deni̇z Taşdemi̇r, İhsan Çaliş, Chris M. Ireland Jan 2002

Phenylethanoid Glycosides From Scutellaria Galericulata, Tayfun Ersöz, Deni̇z Taşdemi̇r, İhsan Çaliş, Chris M. Ireland

Turkish Journal of Chemistry

From the aerial parts of Scutellaria galericulata L., four phenylethanoid glycosides, 2-(4-hydroxyphenyl)-ethyl-(6-O-caffeoyl)-\beta -D-glucopyranoside (1), calceolarioside B (2), osmanthuside E (3) and martynoside (4), were isolated. The structure elucidations of the isolated compounds were performed by spectroscopic (UV, IR, ESI-MS, 1D- and 2D-NMR) methods. Compounds 1-4 demonstrated scavenging properties toward the 1,1-diphenyl-1-picrylhydrazyl (DPPH) radical in TLC autographic assays.

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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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A Conformational Exploration Of Dissymmetric Macrolides Antibiotics, Salah Belaidi, A. Dibi, M. Omari Jan 2002

A Conformational Exploration Of Dissymmetric Macrolides Antibiotics, Salah Belaidi, A. Dibi, M. Omari

Turkish Journal of Chemistry

Conformational analysis of the macrolides from 12 to 22 links was carried out using molecular mechanics. Calculations indicate that each studied macrocycle presents eight families of preferential conformers. They result from the combination of the conformations of the two systems diene and \alpha ,\beta -unsaturated ester. Among these conformers three families (F5, F6 and F3) have the lowest energy. The two families F5 and F6 adopt an s-cis conformation of the ester function and s-trans of the diene system with a pseudo-parallel arrangement of the two systems for the first family and a pseudo-antiparallel for the second. The third family …

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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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Trypsin-Catalyzed Peptide Synthesis In Acetonitrile With Low Water Content, Yeşi̇m Yeşi̇loğlu, Ayten Sağiroğlu Jan 2002

Trypsin-Catalyzed Peptide Synthesis In Acetonitrile With Low Water Content, Yeşi̇m Yeşi̇loğlu, Ayten Sağiroğlu

Turkish Journal of Chemistry

Trypsin was immobilized to alumina by adsorption from its aqueous solutions. The activity of trypsin was increased by immobilization for peptide synthesis. With these immobilized enzymes Bz-Arg-Leu-NH_{2} dipeptide synthesis was carried out. Iso amylalcohol, tetrahydrofuran and acetonitrile were used as solvents giving the highest yield in the peptide formation reaction. The yield of the peptide was strongly dependent on water content in the reaction medium. The stability of alumina-immobilized trypsin is described.

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Bromination Of 2,3-Dibromobenzobarrelene At Different Conditions: Highly Brominated Benzobicyclic Systems, Ari̇f Daştan Jan 2002

Bromination Of 2,3-Dibromobenzobarrelene At Different Conditions: Highly Brominated Benzobicyclic Systems, Ari̇f Daştan

Turkish Journal of Chemistry

The electrophilic addition of bromine to 2,3-dibromobenzobarrelene at 10^oC led to the formation of completely rearranged products in high yield. Bromination of 2,3-dibromobenzobarrelene with molecular bromine in decalin at 150^oC and with DBTCE in CCl_{4} at 77^oC gave rearranged and non-rearranged products. The radical and ionic mechanism are discussed. All compounds were characterized properly, by NMR spectroscopy and chemical transformation.

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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 And Magnetic, Spectral And Thermal Studies On Metal 1,3,8,10,15,17,22,24-Octanitrophthalocyanines, Kallam R. Venugopala Reddy, Jathi Keshavayya Jan 2002

Synthesis And Magnetic, Spectral And Thermal Studies On Metal 1,3,8,10,15,17,22,24-Octanitrophthalocyanines, Kallam R. Venugopala Reddy, Jathi Keshavayya

Turkish Journal of Chemistry

A simple and novel method for the preparation of 1,3,8,10,15,17,22,24-octanitrophthalocyanine derivatives, MPcON's (M = Fe (III)Cl, Zn(II), Co(II), Cu(II) and Ni(II)), was developed. The dark green complexes were characterized by elemental analysis, electronic spectra, IR spectra, thermogravimetry, differential thermal analysis, powder X-ray diffraction and magnetic susceptibility.

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Phenolic Compounds From Scutellaria Pontica, Tayfun Ersöz, Ü. Şebnem Harput, İclal Saracoğlu, İhsan Çaliş, Yukio Ogihara Jan 2002

Phenolic Compounds From Scutellaria Pontica, Tayfun Ersöz, Ü. Şebnem Harput, İclal Saracoğlu, İhsan Çaliş, Yukio Ogihara

Turkish Journal of Chemistry

From the aerial parts of Scutellaria pontica, a phenolic glucoside, 3,5-dihydroxyphenyl \beta -D-glucopyranoside (1); as well as a C-glucosyl flavon, isovitexin (2); flavones and flavone glycosides, 5-hydroxy-7,3',4'-trimethoxyflavone (3); apigenin (4); apigenin-7-O-\beta-D-glucopyranoside (5); and apigenin-7-O-\beta-D-glucopyranoside-4'-O-methylether (6) were isolated in addition to two phenylethanoid glycosides, martynoside (7) and verbascoside (= acteoside) (8). The structures of the isolated compounds were established on the basis of spectroscopic evidence.

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Solid-Phase Extraction Of Copper With Lead 4-Benzylpiperidinedithiocarbamate On Microcrystalline Naphthalene And Its Spectrophotometric Determination, Hasan Cesur, Beki̇r Bati Jan 2002

Solid-Phase Extraction Of Copper With Lead 4-Benzylpiperidinedithiocarbamate On Microcrystalline Naphthalene And Its Spectrophotometric Determination, Hasan Cesur, Beki̇r Bati

Turkish Journal of Chemistry

Using lead 4-benzylpiperidinedithiocarbamate complex (Pb(4-BPDC)_{2}), a solid-phase extraction method was developed for pre-concentration and spectrophotometric determination of copper in water samples. In this method, copper in large volume liquid phase quantitatively replaces lead on colorless Pb(4-BPDC)_{2} complex and naphthalene solid phase mixture forming Cu-4-benzylpiperidinedithiocarbamate complex (Cu(4-BPDC)_{2}). The solid phase containing colored Cu(4-BPDC)_{2} is dissolved in chloroform and its absorbance is measured at 437 nm against the reagent blank. The range of linearity is 0.4 -10 \mu gml^{-1} of copper in chloroform, the molar absorptivity of the complex determined from the linear portion of Beer's law plot is 8.197x10^{3} lmol^{-1}cm^{-1} and …

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Thermal Behaviour Of Copper(Ii), Nickel(Ii), Cobalt(Ii) And Palladium(Ii) Complexes Of N,N-Dimethyl-N'-Benzoylthiourea, Göktürk Avşar, Nevzat Külcü, Hakan Arslan Jan 2002

Thermal Behaviour Of Copper(Ii), Nickel(Ii), Cobalt(Ii) And Palladium(Ii) Complexes Of N,N-Dimethyl-N'-Benzoylthiourea, Göktürk Avşar, Nevzat Külcü, Hakan Arslan

Turkish Journal of Chemistry

N,N-dimethyl-N'-benzoylthiourea (DMBT) complexes of Ni(II), Cu(II), Co(II) and Pd(II) were synthesised. The thermal decomposition of these metal complexes was investigated by TG, DTG and DTA. A GC-MS combined system was used to identify the products during pyrolytic decomposition. The pyrolytic end-products were identified by X-ray powder diffraction. The thermoanalytical data of these complexes are presented in this communication. The kinetic analysis of the thermogravimetric data was performed by using the Coats-Redfern and Horowitz-Metzger methods. All the metal complexes except Cu(II) complex undergo decomposition in three stages and NiS, CoS, Pd, and Cu remained as end-products of the complexes.

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Electrochemical Behavior Of Benzo[C]Cinnoline And Its Bromo Derivatives, Ni̇lgün Seçken, M. Levent Aksu, Ali̇ Osman Solak, Emi̇ne Kiliç Jan 2002

Electrochemical Behavior Of Benzo[C]Cinnoline And Its Bromo Derivatives, Ni̇lgün Seçken, M. Levent Aksu, Ali̇ Osman Solak, Emi̇ne Kiliç

Turkish Journal of Chemistry

The electrochemical behavior of benzo[c]cinnoline and some of its bromo derivatives was studied. Two discrete 2-electron reduction waves in acidic and only one wave in basic media in ethyl alcohol-BR buffer system (l:5 v/v) were observed. A mechanism for the electrode reaction is proposed. Diffusion coefficients, formal potentials for and the derivatives, the number of electrons transferred were determined by using sampled current polarography, cyclic voltammetry, chronoamperometry, chronocoulometry and constant potential coulometry. Adsorption of the molecules on the surface of the mercury drop was analyzed and this phenomena was exploited to calculate the formal potentials and the diffusion coefficients of …

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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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The Use Of Chloranilic Acid For The Spectrophotometric Determination Of Three Antihistamines, Kanakapura Basavaiah, V. S. Charan Jan 2002

The Use Of Chloranilic Acid For The Spectrophotometric Determination Of Three Antihistamines, Kanakapura Basavaiah, V. S. Charan

Turkish Journal of Chemistry

Cyproheptadine hydrochloride (CPH), methdilazine hydrochloride (MDH) and promethazine theoclate (PMT) were determined in their pure state and in pharmaceutical formulations by a simple spectrophotometric method. The determination was based on the formation of a charge-transfer complex between chloranilic acid as a \pi-acceptor and the studied drugs as n-donors in an acetonitrile-chloroform mixture. The spectra, various experimental parameters, the stoichiometry and the stability of the complexes formed were investigated. The complexes formed were found to absorb at 520 nm. Beer's law is obeyed in the concentration ranges 25-125, 20-100 and 25-150 \mu g ml^{-1}, for CPH, MDH and PMT respectively. The …

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Application Of Proton Conducting Polymer Electrolytes To Electrochromic Devices, Ayhan Bozkurt Jan 2002

Application Of Proton Conducting Polymer Electrolytes To Electrochromic Devices, Ayhan Bozkurt

Turkish Journal of Chemistry

Electrochromic display devices have been fabricated using Polydiallyldimethylammonium dihydrogenphosphate (PAMA^+ H_2PO_4^-) blended with H_3PO_4 as the electrolyte and WO_3 as the electrochromic film. The WO_3 deposited glass electrodes were doped with protons to form H_xWO_3 in which color depends on the charge density (CD) ranging from 0.01 to 0.04 C/cm^2. Proton conducting films of PAMA^+ H_2PO_4^- 2 H_3PO_4 (2 moles of acid per polymer repeat unit) were sandwiched between two electrodes to obtain the following symmetric configuration: Glass/ITO/WO_3/H^+ -electrolyte film/H_xWO_3 /ITO/Glass. Prior to construction of the electrochromic windows, the electrochemical stability of polymer/acid blends was determined via cyclic voltammetry (CV).

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Determination Of Linear Alkylbenzene Sulphonates And Their Biodegradation Intermediates By Isocratic Rp-Hplc, Mehmet Akyüz, David J. Roberts Jan 2002

Determination Of Linear Alkylbenzene Sulphonates And Their Biodegradation Intermediates By Isocratic Rp-Hplc, Mehmet Akyüz, David J. Roberts

Turkish Journal of Chemistry

An HPLC method was developed to determine linear alkylbenzene sulphonates (LASs) and their biotransformation products sulphophenyl carboxylates by isocratic chromatography using two C_{18} columns in series. Solid-phase extraction with a (C_{18}) cartridge was employed to isolate LAS from sediment and sewage effluent samples. Sodium perchlorate and ammonium perchlorate were used as ion pair agents. The recovery of the compounds was 94% \pm 2 and 98% \pm 2 respectively for sediment and sewage effluent. It was demonstrated that it is possible to separate LAS compounds and their isomers and homologues using this system.

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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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