VOLUME 17, NO4, DEC 1995

Hydrothermal reactions between lime and aggregate fines .2. Experimental conditions for strength improvement using saturated steam at elevated pressure

Investigation into the compressive strengths of various mixtures of indigenous materials consisting lime and aggregate fines such as silica sand, slate and rice husk ash, autoclaved at a temperature of 180 degrees C under a steam pressure of 1.17 MPa for 4.5 hours was undertaken. It was found that me maximum compressive strength of 59.8 MPa could be achieved after 4.5 hours reaction between a mixture of 80.0% silica sand, 15.0% lime and 5.0% slate under the above conditions of temperature and pressure. However, under the same conditions of temperature and steam pressure, lower strengths were obtained for other mixtures of these materials. Thus, for example, when, a mixture of 80.0% silica sand, 15.0% lime and 5.0% rice husk ash and a mixture of 85.0% slate and 15.0% lime were tried, then the respective strengths of 47.6 and 34.7 MPa were achieved.read more

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SHAH ALAM KHAN ,

Adsorption of zinc from zinc acetate solution on clay (Kaolinite)

Adsorption studies of Zinc from Zinc acetate solutions on Clay (Kaolinite) were made under varying conditions of time and pH. Adsorption equilibrium was found to be established within two hours in case of Zinc acetate solution of 50 ppm concentration. Increase in pH was found to have a significant positive effect on the extent of adsorption. Freundlich's and Langmuir's equations, when applied to the isotherm data, obeyed very well.read more

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YOUSAF IQBAL KHATTAK ,SALEH UD DIN ,SYED KAMAL UDDIN ,

Adsorption of copper from copper acetate and copper chloride solutions on carbon black ''Spheron 9'' .3.

Adsorption studies of copper from copper acetate and copper chloride solutions on carbon black ''Spheron 9'' were made at three different pH ranges. Adsorption of copper increased with increase in pH, which was attributed mainly to excessive precipitation and formation of unionized or partially ionized copper species at high pH, which might have adsorbed to a greater extent on the nonpolar graphitic surface of carbon compared to ionic species. Effect of anion of the copper salt was also observed to have an effect on adsorption. Fruendlich's and Langmuir's equations were applied to the adsorption isotherms and it was found that both equations were obeyed.read more

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YOUSAF IQBAL KHATTAK ,M ARSALA KHAN ,

Circular dichroism studies of Pfeiffer active vanadium(III) and chromium(III) complexes of ethylenediaminetetracetate (EDTA(4-)) and diethylenetriaminepentacetate (DTPA(5-)) ions

The Pfeiffer effect has been investigated in aqueous solution of [Cr(EDTA)H2O](-), [Cr(DTPA)](2-). [V(EDTA)](-) and [V(DTPA](2-) ions in presence of various chiral environment substances, such as (+)-cinchonine HCl, (-)-cinchonidine HCl, (+)-tartaric acid and (-)-tartaric acid, (+)-alpha-methylbenzylamine HCl, (+)-ascorbic acid, (-)-brucine HCl and (-)-ephedrine HCl. The CD spectra of these complex ions in presence of different chiral environment substances have been reported and Cotton bands assigned to electronic transitions. From the Pfeiffer effect and CD studies, (+)(D)-[Cr(EDTA). H2O](-), (+)(D)-[Cr(DTPA)](2-), (+)(D)-[V(EDTA)](-) and (+)(D)-[V(DTPA)](2-) are assigned Delta absolute configuration around the metal ions.read more

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CHRISTY MUNIR ,SYED RAUF ,NASIR AHMAD ,

Assessment of current trace metal pollution status of the south-east Arabian Sea coast of Pakistan through fish analysis

Eleven trace metals (Ag, As, Cd, Cu, Fe, Mn, Ni, ph, Zn tend Hg) and four macronutrients (Na K, Ca and Mg) were estimated in 143 fish samples pertaining to 6 commercial marine fish species (Pampus argenteus, Dussumieria acuta, Gazza minuta, Lepturocanthus savala, Parastromateus niger, Pseudorhombus arsius) harvested during September-March 1993, from locations along the south-west coast of the Arabian Sea, Pakistan using the atomic absorption method. To assess the enhancement of pollution over the past six years the present trace metal data is compared with the counterpart for a common fish (Pampus argenteus) harvested from the same location during September-March, 1987. Arsenic, iron, nickel, zinc and mercury showed dominant concentrations, with the values of 7.317, 5.908, 1.891, 10.201 and 0.746 mu g/g. The data reflected species specificity towards metal uptake and showed no direct relationship for macronutrient levels. The average metal concentrations found in various fish species were higher for industrial metals, such as As, Cd, Cr, Cu, Fe, Ni, Zn and Hg. The overall pattern of increasing metal concentrations are: Hg < Pb < Cd < Zn < Ni < Cu < Fe < As < Mn < Cr. The study based on Pampus argenteus, selected as a common species, revealed that Cr and Mn concentrations have increased to about 4-fold, and As by about 2.5 fold during the past 6 years, indicated a gross metal pollution of the coastal waters of the sea.read more

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JALEEL TARIQ ,M ASHRAF ,M JAFFAR ,

Reaction of triarylantimony dihalides with interhalogens and antimonypentachloride

The formation of chlorotriaryl, and bromotriaryl antimony cations by the reactions of various triarylantimony dichlorides and triarylantimony dibromides with the halide ion accepters, iodine chloride, iodine bromide and antimonypentachloride, have been studied by conductometric titrations in acetonitrile. Formation of cations of type R(3)SbX(+) are not very common. R(3)SbCl(+) can only be formed amen me halide acceptor is SbCl5 and the complexes have the composition R(3)SbCl(2). 2SbCl(5) (= R(3)SbCl(+).Sb2Cl11. Evidence for the R(3)Sb Br+ cation is obtained from the conductometric titration of [(CH3)(2)C6H3](3) SbBr2 - IBr and from the formation of the solid adduct [(CH3)(2)C6H3](3) SbBr3I (=[(CH3)(2)C6H3](3) SbBr+IBr2-.read more

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ABDULLAH KHAN ,

Production of aluminum sulphate from indigenous bauxite without precalcination of the ore

Reaction parameters for the production of aluminum sulphate (aluminoferric grade) from Khushab bauxite without precalcination of the ore, were studied using a lead-lined reaction vessel. Commercial sulphuric acid was used for the dissolution of alumina (Al2O3) present in the ore. Acid concentrations ranged from 30-65 wt.% H2SO4 and the acid quantity was of me stoichiometric requirement of bauxite. The reaction temperature was adjusted at 120 degrees C for a time period of 0.5-6.5 hrs. whereas the particle size of the ore was -120 mesh. It has been found that 70% conversion of Al2O3 with 97% purity can be achieved after 5 hrs. reaction time at acid concentration of 60 wt.% H2SO4. This conversion is associated with icon and free acid as impurities, while the free acid can be neutralized by adding bauxite in excess.read more

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SHAH ALAM KHAN ,MUMTAZ HUSSIAN ,

Chemical evaluation, infrared spectral, thermal and upgradation studies of Bataknala, Hazara (NWFP) phosphate

The present investigations were carried out on Bataknala (BKN) phosphate deposits in Hazara (NWFP). Chemical, infrared spectral and thermogravimetric analyses showed these deposits to be of high-grade containing P2O5 mineral content greater than 30%. However, because of the presence ch high content of undesirable impurities, especially magnesia (%MgO. = 2.03 +/- 0.15), the phosphate ore is not acceptable to NFC for phosphate fertilizer production in the country. In the present study, efforts have been made to upgrade BKN ore employing particle size reduction and flotation techniques. Details of these investigations alongwith the results of chemical analyses, infrared spectral and thermogravimetric studies carried wt on the phosphate ore are described and discussed.read more

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MOHAMMAD RIAZ ,MAHMOOD A KHWAJA ,ISMAT KHATTAK ,

Spectroscopic and x-ray diffraction studies of chelates of 2-hydroxy-4-aminobenzoic acid with group IB and IIB metals

The present study is based on the formation of chelates of 2-hydroxy-4-aminobenzoic acid (sod salt) with group IB and IIB metals. The synthesised compounds were characterised using techniques such as atomic absorption, infrared spectroscopy, elemental analysis and X-ray diffraction.read more

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BUSHRA KHAN ,M ZAFAR IQBAL ,C M ASHRAF ,

Kinetic and equilibrium studies of cyclodextrin and amino acid-thiol-o-phthalaldehyde (OPA) reaction using flow injection analysis and fluorescence detection

The effect of cyclodextrin on the fluorescence intensity of amino acid-thiol-OPA reaction has been studied. The host-guest inclusion phenomenon was successfully observed for DL-lysine and L-serine with cyclodextrins. Fluorescence enhancement was in agreement with expectations. Kinetic and equilibrium studies were made by flow injection fluorescence analysis. Effect of thiol and time on fluorescence intensity were recorded.read more

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J N MILLER ,MUHAMMAD YOUNAS KHOKHAR ,