VOLUME 24, NO3, DEC 2002
12
 
Kinetics of the Oxidation of Thiamine by Hg(II) in Basic Medium

R H HINA ,

The rate of oxidation of thiamine ( Vitamin B, ) by Hg(II) ion in basic medium (pH=12.2) has  been  studied The   concentration of [OH']and Hg(II) were kept  constant by using  0.20M phosphate buffer and 2.0×10-3M Hg(II).  The initial rate of formation of the only product   of thiochrome was  followed spectrophotometrically at h   = 350 nm for the first 2-3 minutes  The reaction has  been studied  in the temperature range of  279 K  to 314.4 K.  The reaction is pseudo-first  order with  respect to thiamine .Different kinetics and thermodynamics parameters such as rate costants, activation energy, enthalpy of activation, entropy of activation and   Gibbs   energy  of   activation of  the  reaction were   reported. Various concentrations of thiamine  were   successfully found   by  measuring  there  initial  rates  in   different synthetic mixtures containing other foreign species.
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UV Absorbance Studies of Dilute Polystyrene Solutions in Different Solvents

Y IQBAL ,S A KHAN ,W KHAN ,M S SHAH ,

This study  was caried   out to have a systematic knowledge of the polystyrene absorbance (M.Wt: 100000) with respect to temperature, concentrations and solvent. A wide  range of concentration wm selected for these studies and four  different solvents i.e.; 1,2-dichloroethane, ethylaccetate  carbontetrachoride and cyclohaxane were employed for this work. The absorption spectra of polystyrene were measured in  these four  solvents at different temperatures of 10' C, 20° C, 30° C, 40' C,  50° C and 60° C. The effect of concentration, temperature and solvent was determined.
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Characterization of Khushab Coal (Punjab Pakistan)

M ISHAQ ,I AHMAD ,N TAJ ,A BAHADER ,M SHAKIRULLAH ,

A  coal sample  obtained from Khushab   District northern Punjab was characterized for various   parameters of coal analysis. It we found from the   ultimate and proximate analysis that fmad carbon is a lightly above 40%, which shows that this coal has not reached its maturity and can be ranked between peat and lignite.  It was also found that it contain about 2.98% total sulfur, which is an indication that  it can be used for metallurgical purposes. The coal has been desulfurized with KOH, NaOH  and HNO3  and the sulfur percentage has decreased   to 0.001%, 0.01% and  0.006% respectively with these leachants. Calorific value  of virgin coal (untreated sample)  has  been  found  to  be  6195 calories/g  but  has increased  to 10448  calories/g  after particularly being leached with (KOH).The coal  was  also leached with hydrochloric acid  and nitric acid  to determine the Icachability of   these two   acids   for  mineral elements  such  a    copper (Cu),   iron  (Fe),  calcium  (Cs), magnesium  (Mg),  nickel  (Ni), mangnesium (Mn), chromium (Cr) and  cadmium  (Cd).  It  we found that a very reasonable amount of these minerals could be extracted with these leachants.
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Synthesis, Structural Characterization and Pyrolysis Studies of Poly-2-vinylpyridine Composites

S ALI ,U RAFIQUE ,M MAZHAR ,M M BHATTI ,

Poly 2-vinylpyridine and its homogeneous composites wing different alkali metal salts    were   synthesized  and   charaterized   by   molecular   weight    determination, infrared spectroscopy, scanning  electron micrography and thermogravimetry. Pyrolysis studies by  TG, DTG  and  DTA  under ambient condition of static air or  argon suggest decomposition of the polymer and composites in more than one step. Kinetic parameters i.e., order of reaction, rate of   thermal decomposition of  reaction and  energy  of  activation were  evaluated from  TG isotherm using Horowitz and Redfarn methods. It was found that the pair of composites having the same anions follows the same thermal and kinetic stability order.
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Comparative Kinetic Study Between the Electron Transfer Reactions of Iron(III) and Iron(II) Complexes

I I NAQVI ,M A FARRUKH ,

The  kinetics  of  reduction of tris(1,10erthophenantiroline)iron(III) ion by  two different  reductants  hexacyanoferrate(II) ion and    bis(s-cyclopentadienyl)iron(II) has been spectrophotometrically investigated in studies   median.   Measurements were  recorded  under pseudo-first  order  condition. The  rate  of  electron  transfer between  tris(1,10-orthophenan- throline)iron(III) and each reductants was measured. The rate laws are suggested to be,  rate = k1 [Fe(C5N5)2]       [Fe(o-phen)3]3+ /1 + K[H+] and rate =  k [Fe(C5H5)2] [Fe(o-phen)3]3+ for the reduction   of  tris(1,10-orthophenanthroline)iron(III) ion with hexacyano-ferrate(II) ion and bis(scyclopentadienyl)iron(II) respectively, showing first order  with  respect to  each of  the reactants in the  both cases. It was  found that the rate of reaction with hexacyanoferrate(II) is faster than that of bis(p-syclopentadienyl)iron(II) having the second order rate constant values of 8.33 x 107M-1s-1 and 5 x 106 M-1s-1 respectively.
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Variation in Uptake of Essential and Toxic Elements of Different Varieties of Wheat Grown in Same Agricultural Plot of Baluchistan, Pakistan

M A JAKHRANI ,T G KAZI ,G Q SHAR ,S R SAHITO ,

The comparative study was done of different wheat varieties in their capacity to accumulate different thirteen cassentials and trace elements grown en same agricultural plot Six samples for each (Zardana, Azri-96 and Daman-98) as representative samples, grown on same plot of agricultural research institute sariab, Quetta. The soil samples of same agricultural plot was also analysed for same elements.Standard  reference samples of same  varieties was  collected from FSCARD   (Federal  Seed Certification and Registration Department) . Atomic absorption spectrophotometer was used for the  determination of all 13 elements. The characteristics mean of each element for three varieties of representative samples were found to be in the ranges of 586.87-974.69, 3606.81- 3697.44, 189.71-269.69, 1511.22-1606.5, 19.19-35.13, 31.7246.59, 32.74-44.28, 4.28-5.32, 1.235-1.551, 0.6094.907, N.D, 0.470-0.528 and 0.271-0.296 mg/kg for Na, K, Ca, Mg, Fe, Zn, Mn, Cu, Ni, Pb,   Co,  Cd and  Cr respectively which were compared with certified samples at 95% confidence limit.
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Comparative Study of PolyAminoCarboxylicAcid Complexes of Essential and Biotoxic Metals

S GULZAR ,Z T MAQSOOD ,N FATIMA ,

Potentiometeric studies have been carried out on 1:1 ML mononuclear complexes, where Ca (II), Fe (III)  and Zn (II) represent the essential metals whereas Pb (II), Cr (III, VI) and  Ni  (II)  are  the biotoxic metal  ions. The ligands selected are  the polyamino carboxylic acida(PAC)such  as  EDTA,  DTPA and   CDTA.  pH  titrations were  performed in  aqueous solutions at an  ionic strength of 0.l M  and  temperature 30°C. Formation of above mentioned metal-PAC complexes were  studied and compared. DTPA  was found comparatively a strong acid among the three PAC acids and suitable for complexation especially at the pH below 2.5 contrarily to CDT A and EDTA.
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Determination of Seven Heavy Metals, Cadmium, Cobalt, Chromium, Nickel, Lead, Copper and Manganese in Wheat flour Samples by Flame Atomic Absorption Spectrometry

S R SAHITO ,M A JAKHRANI ,G Q SHAR ,T G KAZI ,M A MEMON ,

The determination of the total elemental contents using wet acid digestion method by nitric acid and hydrogen peroxide for dissolution of seven heavy metals (Cd, Co, Cr, Ni, Pb,Cu and Mn)  in the wheat flour of certi6cd and representative samples of eight wheat varieties of  the  Sindh,  Pakistan, by  atomic absorption spectrometry. The experimental study was conducted using six samples for each of eight wheat varieties of FSC&RD standard reference materials and  representative samples which was  collected  from four  agricultural research Institutes. The characteristics mean of each element for each variety of representative samples found  to be  in  the range of 0.383-0.73,  0.50-1.82, 0.2014.289, 0.777-1.067, 0.525-0.879, 2.42-4.12, and 23.14 -37.14 in mg/kg for Cd, Co, Cr, Ni, Pb, Cu and Mn respectively, and was compared with certified sample which is at the 95% confidence limit.
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Synthesis and Characterization of Some New Derivatives of 2,4-Dihydro-4-benzyl-5- (pyridyl)-3H-1,2,4-triazole-3-thione

A MOBINIKHALEDI ,T TOFIGHI ,K H ZAMANI ,R IQBAL ,

A series of  new   disulphides, methylthia, triazolium salt, benzylthio, ylthio acetamide and ylthio acetic acid derivatives of 2,4-dihydro-4-benzyl-5-(pyridyl)-3H-1,2,4-triazole-3-thione have been synthesized. Their IR, 'H-NMR, MS spectral data and elemental analysis have established structures of new compounds.
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Pharmacochemical Studies of the Oil, Aerial Parts, Pulp and Peel of Citrullus colocynthis

M SALEEM ,A MALIK ,N AFZA ,M A KALHORO ,

The fixed oil  of Citrullus  colocynthis Schrad seeds (Cucurbitaceae) has been investigated for its physics-chemical characterization and the fatty acid composition. The toxicological and hypoglycemic properties of the oil and various crude  extracts of C.colocynthus have also been investigated.
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