VOLUME 26, NO3, SEPT 2004

Flow and Conductance Behaviour of Poly (Ethylene Oxide) in the Presence of Some Inorganic Salts

Different solution properties like viscosities, conductance, surface tension and light scattering of poly(ethylene oxide) dissolved in water, in the absence as well as presence of some salts like LiCI, NaCI and KCI have been studied over a wide range of polymer concentration. The data so obtained are analyzed and correlated/discussed in the light of conformational changes with the change in ionic strength and ionic size of the electrolytes used. From the initial data of conductance, the limiting conductance and. other related parameters have been obtained. From these results, the degree of association (a.), association constant (k.) of the polymer and effect of different parameters upon these are discussed. From the results, we can conclude that degree of association and association constant of polyelectrolytes can also be estimated through conductance measurement. read more

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M K BALOCH ,G HAMEED ,G F DURRANI ,

Some Physico-chemical Characteristics of Chalcopyrite Ore

Fresh ore samples frori-I Shinkai copper ore site were collected, crushed and grinded. Different mesh sizes were analyzed for densities and the concentrations of copper. Point of zero charge (PZC) of the ore was determined as a fUlTCtion of temperature (293 - 323 K) and was observed to decrease with temperature for all the mesh sizes. The mineral assay of the solid showed that the concentration of SiOz decreases while the concentration of copper increases with decrease in the particle size of the ore.read more

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S MUSTAFA ,A NAEEM ,A HAMID ,

Inter and Intra-molecular Forces of PMMA Polymer in Acetone

The present investigation was carried out to study the solution properties of Poly(methylemethacrylate) PMMA in acetone by viscometric technique. Viscosity of six samples of PMMA in the molecular weight range, 3.35xI0· to 2.132xIO·, was studied at 10­30°C, with 5°C interval.The reduced viscosity data were employed to determine the intrinsic viscosity[TJ], Huggin's constant (KH) and Kraemer's constant (KK) at different temperatures. From the calculated values of the intrinsic viscosity and molecular weights the Mark-Houwink equation parameters 'K' and 'a' were estimated at different temperatures. The values of 'K' and 'a' support the idea that acetone is a good solvent for PMMA. Inter (KH1 () and intra-molecular (KH( I) Huggin's coefficients were calculated for different PMMA samples. It was observed that the intra molecular attraction increases with rise in molecular weight of the polymer.read more

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A NAEEM ,S TASLEEM ,S MURTAZA ,K FARINA ,B DILHARA ,

Stoichiometry of Quinol/ Ammonium-Nitrogen Complex Using Spectrophotometry

:Quinol (1,4- dihydroxybenzene) forms instantaneous pink complex with aqueous ammonium-nitrogen(NH/ -N). Hydrogen perioxide accentuates the colour. This complex, which we now refer to as QI NH/~N complex, can be the basis for the spectrometric determination ofNH/-N in aqueous solution. Aqueous NH/oN is a very important pollution index in water pollution studies. Therefore, it is imperative that the stoichiometry of this complex be thoroughly understood. In this work, Job's method of continuous variations [1,2,3,4] and the molar-ratio method [5,6,7] were used in a corroborative manner to study and establish the QI NH/ -N complex as Q(NH4)4, where Q stands for quino.read more

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E E UKPEBOR ,P O OKOLO ,

Physio-Analytical Studies on Commerical Milk Samples

Physical properties such as density: viscosity, pH and conductance of commercial milk samples have been determined. Total solids, water, sugar and protein contents of milk samples are also estimated. A simple and low cost digestion method has been developed for quantitative analysis of Na, K, Ca, Mg and Zn in milk samples using flame atomic absorption spectrometry. The method involves partial digestion of samples using nitric acid at 105 ± 5° C in oil bath for forty-five minutes. Relative standard deviation for Na, K and Ca is better than I % and for Mg and Zn around 2%. The concentration ranges for Na, K, Ca, Mg and Zn are 240.00 -776.50, 422.50 - 710.00,831.75 - 1172.50,51.23 - 108.51 and 2.88 - 7.31 j.lg mrl respectively.read more

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S B NIAZI ,A RAZA ,M Y KHOKHAR ,F MAHMOOD ,

Action of Some J'ransition Metal Salts on Methyl Orange

Methyl orange reacts with some salts of transition metals such as Ni(I1), Cu(I1) and Co(I1) in non polar solvent to give different metalated products through N=N and C-N bond cleavage. Their structures are confirmed by chemical analysis and some spectroscopic (fR, UVNis, MS and X-ray) methods.read more

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I KH EL SAYED ,E A EL SAWI ,T B MOSTAFA ,

Spectroscopic Studies of Exchange and Pyrolysis Reactions in Mixtures of Trimethylamine alane, Trimethylgallane and Triethylgallane

Rapid alkyl exchange reactions in gas phase mixture of trimethylamine alane and trialkylgallane lead to a statisticall mixture of trialkylgallane. Partial pyrolysis of these mixtures leads to selective /3-elimination of ethyl groups, resulting in a mixture of dialkyl and monoalkylgallanes, which have been characterised by FI1R, proton NMR and mass spectrometry. The mass spectrometric observations revel the presence of dimeric and trimeric species. The NMR results confirm this conclusion, and further suggest that interamolecular exchange processes are fast even at 200 K, whereas intermolecular exchange is significant only above 250 K.read more

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Z MAHMOOD ,

Spectrophotometric Analysis of Vitamin EUsingCu(I)-Bathocuproine or/and Fe(II)-2,4,6 .. tris-(2 '-pyridyl) .. s .. triazine Complexes

Vitamin E (tocopherols and toeotrienols) antioxidaAU are detennined by reducing Cu(ll) to Cu(l) or Fe(IIl) to Fe(ll) in presence of vitaminE and"subsequentcomplexation of Cu(l) with bathocuproine and lor Fe(1l) with 2,4,6-tris-(2' -p~y1) -s-triazine (TPTZ). Both the reactions are monitored separately, Cu(l)-bathClCUplOiull.at479 nm where as, Fe(llr (TPTZ) at 595 nm spectrophotometrically. Linear calibration ,curves are achieved for both complexes between I to 51!8 mI"l for vitamin E:The methods were applied for the determination of vitamin E in pharmaceutical preparations and edible oils. Vitamin E, from edible oils, ~ solvent exllaCted into n-hexane prior to saponification. .Furthermore, a single lined flow injection manifold was also'lcxamined. A large excess of Cu(ll) or Fe(llI) with different concentrations of vitamin E in buffer pH 4 was run on the line and constant amounts of reagent bathocuproine or TPTZ in each case was injected through the injector. The peak height shows a linear relationship for vitamin E between 0.5 to 2.5 I!g mI"l for both complexes.read more

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S A MEMON ,M Y KHUHAWAR ,I DEVI ,

Peptide Synthesis Catalyzed by Immobilized Trypsin in Organic Solvents

Trypsin was immobilized to poly vinyl alcohol (PVA) by adsorption from its aqueous solutions. The catalytic activity of trypsin increased markedly by irnmobiliZl!-tion for peptide synthesis from N-a-benzoyl L-arginine in hydrophilic organic solvents such as tetrahydrofuran or ethanol. The yield of Bz-Arg-Leu-NH2 is strongly dependent on the PV Ntrypsin ratio and water content in the reaction medium. The optimum pH and temperature were determined for immobilized trypsin as 7.0 and 40°C, respectivelyread more

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Y YESILOGLU ,

Invitro Screening for Biological and Pharmacological Effects of Indigenous Medicinal Plants, Mentha longifolia and Aloe vera

The crude ethanolic extracts of Mentha longifolia Linn. (leaves and stem) and Aloe vera (leaves) were screened for various invitro biological and phannacological activities including antifungal, antibacterial, insecticidal, phytotoxic activities and brine-shrimp lethality. All the extracts exhibited remarkable (~6O%) phytotoxic activity in the highest tested concentration (500 ppm) against Lemna minor L. with Aloe vera extract showing complete inhibition of the studied plant. The Mentha longifolia Linn. (stem) and Aloe vera extracts were also explored to posses good (~55%) antifungal activities against Trichophyton longifusus, (75% and 60%), and Microsporum canis (65% and 55%), respectively while Mentha longifolia Linn. (leaves) displayed only a weak (:5:50%) activity against Trichophyton longifusus and Fusarium solani (20% each). These extracts were found to be devoid of any antibacterial, insecticidal activities and Brine shrimp lethality during this study. read more

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H U SHAH ,A A SHAD ,S KHATTAK ,S U REHMAN ,M AHMAD ,T KHAN ,