VOLUME 18, NO4, DEC 1996

Interfacial properties of alpha-FeOOH, prepared by two different methods

alpha-FeOOH was prepared by two different methods and were designated as sample-1 and sample-2. Point of zero charge (PZC) and surface ionization and complexation constants of both the samples were calculated from the potentiometric titration data of their suspensions in aqueous electrolyte solutions. PZC values of the sample-1 and sample-2 were found to be at pH similar or equal to 8.4 and 8.2 respectively, which demonstrated a negligible difference. However, the absolute values of their surface charge at the given pH and electrolyte concentration was significantly high for sample-1 as compared with sample-2. This was attributed to the high Ns values (total number of surface sites) of former sample. Moreover, the numerical values Delta pK(a)(int) and Delta p*K-complex(int) suggested the fad that ionization and complexation reactions were weak in sample-2 as compared with sample-1.read more

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H U REHMAN ,M SHAKIRULLAH ,I U HAQ ,

Effect of lithium halides on the characteristic vibration frequencies of 1 propanol

In the present work, emphasis is given to nu(O-H), delta(O-H) and nu(C-O) vibrations of 1-propanol and the effects of lithium chloride and bromide on frequencies of these vibrations. It has been found in general, that solutions in lower concentration ranges departed to a greater extent from respective frequencies for pure 1-propanol, because of the fad that at Lower concentration, there are large interactions between dipoles and the counter ions which result in decrease in energy of vibration. So, a fall in wavenumbers is of common occurrence with increasing salt concentration and lends to become constant at or near the saturation limit.read more

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M J IQBAL ,M IKRAM ,Z M BHATTI ,M A RAUF ,

Effect of lithium halides on the characteristic vibrational frequencies of propanoic acid

Effect of Lithium Chloride and Bromide on nu(C=O) and delta(O-H) have been investigated. ion solvent interactions are responsible for the shift of characteristic vibrational frequencies of pure propanoic acid in solution. As concentration of solution is increased the departure from respective frequencies for pure propanoic acid becomes less pronounced. A general decrease in vibrational frequencies is observed with rise in concentration, it is almost stabilized near saturation point.read more

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M J IQBAL ,S SHUJA ,M IKRAM ,M A RAUF ,

C-13-NMR relaxation study of the methyl group rotation in 2-methyl-quinoline

A C-13-NMR relaxation time T-1 study of the methyl group rotation has been carried out from 27 degrees C to 111 degrees C in the liquid state. The C-13 relaxation time T-1 of the methyl carbon varies from 4.1 a (at 27 degrees C) to 12.889 s (at 111 degrees C). The relaxation time TI has been separated into dipole-dipole relaxation time T-1(DD) with the help of nuclear Overhauser enhancement factor eta. The eta values indicate that the relaxation mechanism is mostly dipolar in nature. The graph of In T-1(DD) versus 1000/T [K-1] is linear and the activation energy associated with the methyl group rotation obtained from slope is 3.49 +/- 0.16 kcal/mol with a regression coefficient r = 0.994. This energy agrees with the value of 3.04 +/- 0.17 kcal/mol obtained previously from a proton relaxation study.read more

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S T H SHERAZI ,A W K KHANZADA ,M H PHULPHOTO ,

Excess molar volumes and viscosities of water +2-propanol at 298.15, 303.15 and 308.15 K

Excess molar volumes and viscosities were calculated for water +2-Propanol mixtures in all mole fraction ranges at three different temperatures, i.e. 298.15, 303.15 and 308.15K. Values of excess molar volume have been found negative for all the temperatures studied and passed through a minima at almost 0.3 male fraction of 2-propanol. Viscosities, eta, are presented as a polynomial in mole fraction x(1) of low molecular weight component of binary mixture: eta = A + BX1 + CX12 + DX13 + EX14.read more

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M A RAUF ,U EHSAN ,M J IQBAL ,

Spectrophotometric determination of the stability constants of Cu(II) and Fe(III) complexes with some aryl Schiff bases

Stability constants of Cu(IT) and Fe(III) with some aryl Schiff bases derived from salicylaldehyde and aniline, 3-hydroxy and 3-chloro anilines were determined spectrophotometrically using ''Chattopadhyaya and Singh'' method at 25 degrees C in methanol. Cu(II) form; 1:1 and 1:2 complexes, and Fe(III) forms 1:3 complexes with these Schiff bases. The order of stability constants of the ligands used for these complexes was as follows: salicylidene-3-hydroxyaniline > salicylidene aniline > salicylidene-3-chloroaniline. The effects of substituent groups on the stability constants were discussed.read more

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M S KARACAN ,N KARACAN ,Y BARAN ,

Copper (II) chelates of tetradentate beta-ketomaines as mixed stationary phases for gas chromatography

Copper (II) chelates of tetradentate beta-ketoamines bis(acetylacetone) ethylenediimine (H(2)AA(2)en), bis (acetylacetone)-propylenediimine (H(2)AA(2)Pn), bis(acetylacetone) dl-stilbenedimine-(dl-H(2)AA(2)S) and bis(acetylacetone) meso-stilbenediimine (meso-H(2)AA(2)S) together with OV-101 have been examined as mixed stationary phase for gas chromatography (GC). ?he copper chelates (5%) and OV-101 (3%) were coated on Chromosorb G/NAW 60-80 mesh size. Thermoanalytical studies were carried out to ascertain the operating temperatures for stationary phases. The materials packed in stainless steel column s(3m x 3 mm i.d.) was examined for relative elution and separation of different organic compounds, including aliphatic hydrocarbons, aromatic hydrocarbons, heteroaromatic compounds, aldehydes, ketones and alcohols. The elution and resolution were compared with a column packed with OV-101 3% on Chromosorb G/NAW 60-80 mesh size. An increase in retention times, and kovats indices were observed with improvement in the resolution of alcohols, ketones and heteroaromatics on mixed stationary phases as compared to OV-101 using the same operating conditions. ?he mixed stationary phases OV-101, 3% with 5% AA(2)enCu or dl-AA(2)SCu have high promise for the separation of alcohols, ketones, hetroaromatics.read more

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

High performance liquid chromatographic separation of putrescine and cadaverine using 2-hydroxynaphthaldehyde as a derivatizing reagent

Biological active diamines, cadaverine and putrescine together with 1,3-propylenediamine and 1,2-propylenediamine react with 2-hydroxynaphthaldehyde to form bis (2-hydroxynaphthaldehyde) 1,5-diiminopentane (HN(2)CA), bis(2-hydroxynaphthaldehyde) 1,4-diiminobutane (HN2Pu) bis (2-hydroxynaphthaldehyde) 1,2-diiminopropane (HN(2)Pn) and bis (2-hydroxynaphthaldehyde) 1,3-diiminopropane (HN2PR). The derivatives are observed to be fluorescent in visible region. The wavelength of excitation (Ex) and emission (Em) were determined for optimal fluorescence of derivatives. The linear calibration for each of the diamine is observed at 0.32-1.6 mu g/ml. The diamine derivatives HN2Pu, HN(2)Pn also separated on Nova Pak C-18 column when eluted with methanol. The spectrofluorimetric detection was obtained at 450 nm using Ex at 315 nm.read more

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M B RIND ,M Y KHUHAWAR ,M A QURSHI ,

Solvent effect on the Si-O stretching bands of benzilidene (ortho dimethylhydrogenosiloxy) aniline by IR spectroscopy

The effect of solvent-solute interaction on vibrational spectra of benzilidene (o-dimethylhydrogenosiloxy) aniline was studied in a number of solvents. The spectral vibrational frequency shifts observed in different solvents have been correlated with refractive indexes and dielectric constants of the solvents. The results obtained were applied to the Buckingham's modification of the Bauer-Magat formula for solute-solvent interaction. Generally, infrared spectral frequencies of Si-O bands in solution phase shifted to lower wavenumber than those observed in gas phase, except in nitrobenzene which is attributed to specific interaction. The calibration lines between Delta v/v vs epsilon-1/2 epsilon+1 were made to determine the specific and non specific solute-solvent interactions. Results obtained from these calibration lines are also discussed in terms of solute-solvent interactions.read more

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M JAVED ,M I ZIA ,M MAZHAR ,M IKRAM ,S ALI ,

Selective determination of Cr(VI) by indirect atomic absorption spectroscopy

A simple, sensitive and rapid indirect method for the determination of chromium(VI)is described. The method is based on the reduction of chromium(VI) to chromium(III) with elemental mercury in sulphuric acid medium. The oxidized mercury in return was determined by atomic absorption spectroscopy and used as a measure of chromium(VI) in the sample. Effects of a number of possible interferences on the determination have been checked and some synthetic and real samples of chromium(VI) have been analysed by the described method as well as by a reference spectrophotometeric method.read more

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M A ASLAM ,M AHMAD ,J ANWAR ,