VOLUME 19, NO3, SEPT 1997

Hydrogen bonding in salts of poly-carboxylic acids, crystal structures of ethylenediammonium hydrogen tetrahydrofuran-tetracarboxylatehydrate (1 : 2 : 1 : 1) and ammonium hydrogen tetrahydrofurantetracarboxylate hydrate (3 : 1 : 1 : 2).

Hydrogen bonding in ethylenedidammonium hydrogen tetrahydrofurantetracarboxylate hydrate (1:2:1:1) and ammonium hydrogen tetrahydrofurantetracarboxylate hydrate (3:1:1:2) leads to extended ring structures. The conformations of the anions in the two salts are different because of the formation of a strong internal hydrogen bond in the ethylenediammonium salt whereas the ammonium compound has an anion pair with very short hydrogen bonds.read more

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JOHN C BARNES ,

Effect of 1-alkanoles on the critical micelle concentration of cetyltrimethyl ammonium bromide

The interaction of 1-alkanols (C-3-C-4, C-6 and C-8) with cetyltrimethyl ammonium bromide (CTAB), a cationic surfactant, was studied by a conductivity method at 25.0 degrees C. The critical micelle concentration (CMC) of CTAB decreased linearly with an increase in the concentration of added I-alkanols within their low concentration regions. The water-micelle partition coefficient, K-x, and the standard free energy change of solubilization, Delta G degrees, of each alcohol from water to micelle were calculated from the limiting slopes, Delta CMC/Delta C,. The free energy of transfer per methylene group; Delta G degrees (CH2) has also been estimated, For 1-alkanols, K-x values increased linearly with the increase in the number of carbon atom, m(n), in the alkyl chain of respective alcohols.read more

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M ALI AWAN ,S A IDRIS ,M ASHRAF ,S S SHAH ,

A study on the effect of caustic potash treatment upon weight loss and tenacity of various pak-made and imported polyester staple fibres

The effect of different concentrations of caustic potash ((KOH) upon Pak-Made (Polylene and Terylene) and imported (Teijen, Eslan, Three Guns and Kuraray) brands of polyester staple fibres revealed that the weight loss increased and tenacity decreased by increasing the concentration of KOH. Furthermore imported brands showed superiority over indigenous polyesters because they showed high resistance against alkali treatment.read more

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AZHAR RASHID ,BABER SHAHBAZ ,S H MUHAMMAD NAWAZ ,

In vitro studies on bioavailability of iron by changing techniques in home cooked foods

Measurement of 1,10 phenanthroline colour complexes with free (Fe++) iron released after "in vitro digestion" of the food stuff was carried out. Intensity of colour produced was directly proportional to the amount of iron released from food which was measured spectrophotometrically. Results have shown a diverse amount of free iron in different foods. In general, it was observed that food processed by simple method and without spices contain comparatively high contents of iron.read more

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SADIA SAIF ,ANEELA ANWAR ,FOUZIA S REHMANI ,

Synthesis and spectroscopic studies of biologically active Co(II), Cu(II) and Ni(II) complexes of hydrazine derived Schiff-base ligands

Some new biologically active mixed ligand hydrazine derived Schiff-base ligands and their Co(II), Cu(II) and Ni(II) complexes have been synthesised and characterized on the basis of conductance and magnetic measurements, elemental analysis and H-1-NMR IR and electronic spectral data, The synthesised ligands and their complexes have been screened for their antibacterial activity. The activity data have shown the metal complexes to be more potential than the uncomplexed ligands against one or more bacterial species.read more

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SYED KHALID AFTAB SHERAZI ,ZAHID HUSSAIN CHOHAN ,

Kinetics and mechanism of conversion of carcinogen hexavalent Cr(VI) to Cr(III) by reduction with ascorbate

To asses the therapeutic efficacy of ascorbic acid in preventing toxic and mutagenic effects of Cr(VI) to Cr(III) the Kinetics and mechanism of reduction of hexavalent chromium by ascorbate has been studied. The reduction was done under pseudo first order condition by taking an excess of ascorbate over hexavalent chromium species. The rise of absorbance of Cr(III) was monitored at 578 nm. The observed rate constants then determined showed a dependence on both ascorbate concentration and pH as well. The bearing of these observations on the mechanism of reduction of hexavalent chromium is discussed in order to explain this.read more

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MUTI UR RAHMAN ,S ARIF KAZMI ,

Water quality characteristics of the Kabul river in Pakistan under high flow conditions

The Kabul river water has been investigated with respect to temperature, pH, conductivity, chloride, sulfate, total alkalinity, total hardness, nitrate, nitrite, ammonia, phosphate, DO, BOD, GOD, and sulfide during high flow conditions between June-August 1993. These values have been compared against standards for the maintenance of fisheries and aquatic life. Two major water quality issues have emerged from this river water survey. These are; organic water pollution, particularly in the Shah Alam branch and lower main river, and sulfide concentration especially in the naguman and Shah Alam branches and lower main river.read more

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SHAH ALAM KHAN ,MUMTAZ KHAN ,

Enzymatic transesterification between sugar alcohol and oils

Pancreatic lipases from bovine and porcine in crude form were immobilized on phenolic resin and utilized for transesterification reactions between sugar alcohol and various oils in nearly dry pyridine. The enzymatically generated esters of sugar alcohol were purified by column chromatography and identified as primary monoesters by TLC.read more

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A NABI ,M YAQOOB ,M MASOOM YASINZAI ,

Synthesis and spectroscopic studies of the complexes of tumor cell differentiating agent hexamethylene bisacetamide with nickel halides

Complexes of the tumor cell differentiating agent hexamethylene bisacetamide (HMBA) with nickel(II) halides e.g. Ni-2(HMBA)(3)Cl-4 . 2H(2)O, Ni-2(HMBA)(3)Br-4 . H2O, Ni(HMBA)Cl-2 . H2O and Ni-3(HMBA)Cl-6 . 3H(2)O have been synthesized and characterized by elemental analysis. On the basis of their reflectance spectra and magnetic susceptibility data, the complexes with 2:3 stoichiometry are assigned as mixed octahedral-tetrahedral structures and can correctly be formulated as [Ni(HMBA)(3)][NiX4]. nH(2)O (X = Cl; n = 2 and X = Br, n = 1). On the other hand, the complex Ni(HMBA)Cl-2 . H2O has essentially a tetrahedral structure and the complex Ni-3(HMBA)Cl-6 . 3H(2)O a chloride-bridged polymeric octahedral structure.read more

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MARGARET GOODGAME ,IZHAR HUSSAIN ,

Spectrophotometric determination of micro concentration of strontium with xylenol orange

A rapid and sensitive spectrophotometric method is developed for the determination of strontium. The method is based on the colour reaction between strontium and xylanol orange. The complex formed is measured for its adsorption at 570 nm Intereference for 20 cations is also investigated.read more

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ABDUL MAJEED ,R N ASMA ,F H NASIM ,NAHEED FIRDOS ,M ATHAR ,