VOLUME 10, NO1, MAR 1988

Molecular Weight Distribution of Cellulose Acetate and its Relations to Different Parameters

Cellulose acetate obtained from Ravi Rayon Ltd. was fractionated into nine different fractions by fractional prec-ipitation using acetone as a solvent and water as a precipitant. For fractional precipitation, an appara­tus is designed which gave better results. Using light scattering and visco­metry methods, the relationship between moelcular weight and refractive index increment, second virial coefficient, radius of gyration and viscosity is developed. The integral and differential molecular weight distribution curves are also plotted.read more

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N AHMAD ,K BALOCH ,

ISOLATION, PURIFICATION AND PARTIAL CHARACTERIZATION OF NEUTRAL OLIGOSACCHARIDES FROM BOVINE GALLBLADDER MUCIN GLYCOPROTEIN

A glycoprotein was isolated from the bovine gallbladder secretion. The glycoprotein was purified on Bio-Gel P-200 and by subsequent mild treat­ment with Pronase. The Pronase treated glycoprotein was further purified by gel chromarography on Sepharose 4B and by ion-exchange chromatography. The purified glycoprotein was subjected to alkaline degradation-borohydride reduction. The liberated oligosaccharide alditols were purified by gel filtration, and separated into neutral and acidic oligosaccharides. Four neutral oligosaccharides, after purification, were characterized by chemical and enzymatic studies and were assigned the following structures and partial structure.read more

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F SMITH ,J T LAMOUNT ,N UDDIN ,S A HUSSAIN ,BER NARD ,S M AJZA ,

A CRITICAL-REVIEW ON THE SOLUBILITY OF BARIUM-SULFATE

Barium sulphate scale is becoming a formidable problem in the oil and gas production from natural reservoirs. Once formed it clogs the oil pipelines, resulting in a large economic lOss. To understand the behaviour of this highly insoluble material a complete and comprehensive review is presented with a critical discussion on the solubility of barium sulphate in presence of different elect ro 1 yte sys terns. I t has been sugges ted tha t the increased solubility is mainly due to the side reactions of both barium and sulphate ions, where as the contribution from ionic strength is relatively small. read more

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M I FAROOQI ,R MAHMOOD ,N BASHIR ,

REACTION OF ALIPHATIC-AMINES WITH TIN-IV TETRACHLORIDE .2. SYNTHESIS OF TETRACHLOROBIS (METHYLAMINE) TIN-IV

2 adduct of tin tetrachloride with methylamine is reported. When pure monomethylamine gas reacts with tin (IV) tetrachloride in the molar ratio (CH3NH2 : SnC14) 4:1 and 6:1 in carbon tetrachloride, only one substance is obtained which is independent of the reaction time. The product is the simple 1:2 adduct of tin (IV) chloride and methylamine. The paper describes the synthesis and properties of this adduct including its i.r. spectrum.read more

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R H A SAMN ,

PARTIAL CHARACTERIZATION OF NEUTRAL OLIGOSACCHARIDES FROM A NORMAL HUMAN BRONCHIAL SECRETION

Normal human bronchial secretion was obtained by washing the lungs with normal saline. The lavage was midly centrifuged to remove the cellular debris, dialyzed and lyophilized. The residue was chromatographed on Bio-Gel P-200 and then on Sepharose 2B. The major oligosaccharides. The neutral oli­gosaccharides, after separation from acidic oligosaccharides, were further purified by gel filtration and ion-exchange chromatography.read more

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M RAZA ,E W NASIR ,A M KASI ,N UDDIN ,

VISCOSITY PARAMETERS AND ENERGY OF ACTIVATION OF DILUTE AQUEOUS POLYVINYL-ALCOHOL (PVOH) SOLUTIONS

The viscometric behaviour of aqueous dilute solutions of polyvinyl alcohol (PVOH) of varying polymer concentration (O.lg/dL-l.Og/dL) and tempe­rature (10 -SO·C) has been studied. Rapid increase in solution viscosity with increase in PVOH concentration are obviously related to polymer nons­phericity and the tendency of molecules to experience extensive nonhydrodyna­mic interaction. The intrinsic viscosities were obtained by using Huggins equation. By applying the Mark-Houwink expression the "viscosity average molecular weight" was determined. Curves were obtained when values of reduced viscosity vs. temperature were plotted except for 0.1 and 0.2g/dL solution where straight lines with negative slopes were attained.read more

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I KHAN ,A SAEED ,N AHAMD ,S AKBER ,

DETERMINATION OF SULFATE BY GAS-PHASE MOLECULAR ABSORPTION SPECTROMETRY

A method has been developed to determine micro quantities of sulphate both in so 1 i d and 1 i qu i d samp 1 es. The su 1 pha te samp 1 es were reduced with a mixture of sodium hypophosphite, hydroiodic acid and acetic acid. The relea­sed hydrogen sulphide is swept to an optical cell and absorption measured at 203 nm, using a selenium hollow chathode lamp.read more

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A HUSSAIN ,J ANWAR ,M I FAROOQI ,

ASSIGNMENT OF ABSOLUTE-CONFIGURATION OF ALPHA-THREO BENZYLIDENE ACETALS OF ACYLIC DERIVATIVES OF ARABINOSE USING NMR-SPECTROSCOPY

The principal 2,3:4,5-diacetyal obtained by benzylidenation of ~_­arabinose dietyl dithioacetal with benzaldehyde/hydrogen chloride has been assigned the R configuration at the 2,3-acetal centre following its conver­sion into 2,3-Q-(~)-benzyl idene-~-arabinitol. The configuration of the latter compound was established by its conversion into "trans" l,4-di-Q-benzoyl-2, 3-Q-benzylidene-erythritol by sequential periodate oxidation, epimerisation of the resulting 2,3-Q-(R)-benzylidene-~-threose to give 2,3-Q-(~)-benzyl­idene-~-erythrose, reduction, and benzoylation.read more

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J W WEBBER ,M H QADIR ,

CHEMICAL INVESTIGATION OF CEDRUS-DEODARA STEM-BARK-I ISOLATION AND STRUCTURE OF BRANCHED-CHAIN FATTY-ACID ETHYL-ESTER

Isolation and structure determination of a new branched chain fatty acid ester is reported from the stem bark of Cedrus deodara. The structure of the compound was established to be ethyl 23-methyl-pentacosanoate on the basis of i .r., n.m.r. and mass spectral data.read more

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S NAHEED ,N KHAN ,

SEPARATION OF COPPER(II), NICKEL(II) AND PALLADIUM(II) COMPLEXES OF BIS(O-HYDROXYACETOPHENONE)ETHYLENEDIIMINE BY HPLC

The separation between copper, nickel and palladium complexes of bis(O-hydroxyacetophenone)ethylenediimine has been achieved, on a stainless steel column (2.6mm x 250mm) packed with aluminium oxide (LiChrosorb Altox T 5f.lm). The complexes were eluted with 60:40 chloroform:n-hexane solvent-1 system wlth the flow rate of 1.5ml mln                       and the absorbance was measured atX 260nm us i ng a UV detector. The 1 i nea r cali bra t i on range wi th detect i on limits for copper, nickel and palladium complexes at lower ng levels have been ascertained.read more

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S A MEMON ,M I BHANGER ,M Y KHUHAWAR ,