VOLUME 23, NO2, JUN 2001

Determination of Dissociation and Thermodynamic Constants of 8-Methylquinoline by Potentiometry in Aqueous and Mixed Organic-Water Solvent Systems

The dissociation constant (pKa) and thermodynamic parameters (60) of 8-methylquinoline are determined in aqueous and in mixed organic-water (Dioxane, EtOH and MeOH) solvent systems. It is observed that dissociation constant of 8-methylquinoline in aqueous system decreases with the increase of temperature. The curve shows some what linear decrease from 10% to 50% composition of solvent. It is to be. noted that pKa values of this compound are lower than quinoline and some of its methyl derivatives. For mixed organic-water solvent systems concentration ionization constant pI<. M and thermodynamic ionization constant pKa values versus percent composition decrease slowly with increase in percent of EtOH, MeOH and Dioxine. The curve of the pKa. verses percent composition shows some what linear decrease in this range.The data have been obtained potentiometrically by titrating aqueous 8-methylquinoline solutions with hydrochloric acid. The values of dissociation constant were obtained from these data by a computer program written in GW-BASIC. From pKa. values Gibb's free energies 60 for the respective pKa values have also been calculated.read more

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A W K KHANZADA ,HAFIZ A BARI ,

Flory Fox Factor, Expansion Factor And Interpenetration Function for Poly (Vinyl) Pyrrolidone

The two parameter theories, being based on Gaussian chain statistics require that when a=l, the quantity  Y and A2 should approach zero. However, the experimental behaviour is different and unexplainable in PVP-Methanol system. For low molecular weight i.e. M<105 in case of PVP, mutually consistent relationships for 'l' and a based on two parameter theories cannot reproduce experimental results. It also fails to describe completely the experimental behaviour of short chains in good solvents.read more

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SHUMAILA BASHIR ,SHAKIR ULLAH ,A SAEED ,BASHIR AHMAD ,

Kinetics of Oxidation of L-Ascorbic Acid by Cobalt(III) Complexe

Kinetics of L-ascorbic acid oxidation by cobalt(III) complexes were studied using stopped-flow spectrophotometry in aqueous solution at 25°C. Kinetics measurements were run under pseudo-first order conditions in which the concentration of ascorbic acid is between one and two orders of magnitude greater than that of the oxidant Cobalt(III) complexes of urea, C2O42-, H20, acac, EDTA, NH3, en, phen, and NO2-, were used to study the ligand effect on ascorbic acid oxidation rate; it is found that the rate of oxidation is first order with respect to both ascorbic acid and oxidizing agents. Results show that the rate of oxidation depends inversely on both the ligand's size and its strength in the specrtrochemical series.read more

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HAMZEH M.ABDEL HALEM ,

Spectroscopic Determination of Zinc with Dithizone in Anionic Micellar Media of Dodecyl Sulphate Salt

A spectrophotometer study of zinc-dithizonate complex in aqueous phase in the presence of sodium dodecyl sulphate (SDS) anionic surfactant is reported here. The presence of micellar system avoids the previous steps of solvent extraction and reduces the cost, toxicity and enhance the molar absorptivity. The method obeys Beer's law in the concentration range of ­­­­­­­­­­­­­­­­­­­­­­­–l.5 x 10-5 -1.5 x 10-4 M. The detection limit of Zn(II) is 3 X 10-6M. The molar absorption, sensitivity, artical micelle concentration, dithizone and metal ion concentration are studied and discussed. The method has been applied to the determination of Zn(II) in pharmaceutical preparation and vegetables. The present method was also compared with FAAS method and the results are comparable. There is no significant difference between the two methods at 95% confidence interval.read more

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M I BHANGER ,G A SHAR ,

Synthesis, Characterization and Antibacterial Activity of Mononuclear Complexes of Chiral Schiff Base 2,6-Bis (lS,2R-2- Hydroxy-l-Methyl-2¬Phenyl-Ethylimino )4- Heptanone

Mononuclear complexes of a new chiral ligand 2,6 bis(1S, 2R, 2-hydroxy-l-methyl­2-pheoy1ethylimino) 4-heptanooe with VO(lV), Co(II), Ni(ll) and UO2(VI) are reported. The lip and its complexes are characterized by elemental analysis and infra-red spectra. The lip has very weak inhibitory effect upon a number of gram positive and gram negative bacteria. However, some of these complexes show grater inhibitory effects upon various bacteria.read more

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NASIR IQBAL ,CHRISTY MUNIR ,JAVED SAFDER ,NASIR AHMAD ,

Simultaneous Removal of Nitrogen and Organic Matter Using Moving Media Complete Mixing Activated Sludge System

This study was carried out to obtain basic parameters for simultaneous removal of nitrogen and organic matter using Moving Media Complete Mixing Activated Sludge (MMCMAS) system with intermittent aeration method. Lab-scale MMCMAS reactor was operated under the variations of organic loading rate and oxic/anoxic time ratio. The organic loading rates were varied at 1, 3, 5 and 7g BODlm3.d respectively. Soluble Chemical Oxygen Demand (SCOD) and Soluble Biological Oxygen Demand (SBOD) removal efficiencies were found to be 87%, 4, and 95% respectively, and no  relationship between organic removal and oxic/anoxic time ratio was observed. Nitrogen remova1 efficiencies ranging from 76% to 89%, varied widely by oxic/anoxic time ratio. The nitrogen removal was increased by increasing anoxic and oxic time for the organic loading rate below 5 g BOD/m3. d and 7g BOD/m'. d, respectively. Sludge production of MMCMAS system with intermittent aeration was 0.16 to 0.36 (g VSS/g BOD removal) averaging 0.27 (g VSSlg BOD removal). This value is relatively lower than the value obtained previously in MMCMAS system with continuous aeration which was 0.38 (g VSS/g BOD removal).read more

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YOUNG JU KIM ,HONG TAE KIM ,T I QURESHI ,SANG HWA OH ,

Flotation Studies for the Up-Gradation of Rock Phosphate of Kakul Hazara

Flotation Studies for the Up-Gradation of Rock Phosphate of Kakul Hazara read more

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M RIAZ ,A RAHMAN KHAN ,KAMIN KHAN ,MUMTAZ KHAN ,

Pesticide Residues in food Available for Human Consumption

Organochlorine pesticides (DOT, DOE, Heptachlor,A1drin,Dieldrin and HHC were detected in different food commodities like milk, fish, and vegetables supplied by water and sewerage board Karachi. Besides, few sample of shell fishes (shrimp, oyster and mussels) along with vegetables were purchased from market The most interesting finding were the presence of DDT in milk. In vegetable, milk and fish concentration of DDT was higher than other pesticides reflecting its accelerated use. General concentration of each chlorinated pesticide in above mentioned food except fish, was DDT 1.02 - 3.38 , DDE 0.01-0.80, Heptachlor 0.53-2.35, Dieldrin 1.20 - 3.56 and alpha BHC traces - 1.52 ng/g .The present study indicates that most of the food commodities sold in Karachi are not free from onganochlorinated pesticide residues. read more

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KHALID JAMIL ,A B MUNSHI ,RABIA ZUBERI ,

Electron Ionization Mass Spectrometric Studies of Some 3-Substituted Isocoumarins and Related Compounds

Fragmentation pattern in mass spectra of some isocoumarins (la-e), dihydro­isocoumarins (1a-e) and related compounds (3-4a-e) are described with the help of ElMS. The molecular formulae are further confirmed by HREIMS peak matching of molecular ion peaks exhibited in EIMS.read more

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M HUSSAIN ,MUHAMMAD T HUSSIAN ,NASIM H RAMA ,

Organotin Carboxylates

Organotin Carboxylates. read more

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SAQIB ALI ,M AZIZ CHOUDHARY ,SONG XUEQING ,XIE QING LAN ,M MAZHAR ,