VOLUME 13, NO2, JUN 1991

THE INFLUENCE OF DIELECTRIC-CONSTANT VARIATIONS ON THE KINETICS OF REACTION BETWEEN BROMATE AND TELLURITE IONS IN AQUEOUS ETHANOL MIXED-SOLVENTS

The rate of the reaction between potassium bromate and potassium tellurite decreases with an increase in the mole fraction of ethanol in aqueous ethanol mixtures at 308 K. A comparison of the experimental and theoretical values of the radius of the activated complex indicates that a double sphere model is the most suitable shape for the activated state formed in the reaction. Electrostatic and non-electrostatic contributions to the changes in free energy of activation and entropy values are 14.06 kJ/mole, 95.57 kJ/mole and -54.19 J/K/mole in 0.153 mole fraction of ethanol in water. The activation parameters correlates well with the dielectric constants of the media.read more

---

SYED AKHTAR HUSSIAN ZAIDI ,

BET SURFACE-AREA ANALYSIS OF NICKEL-CATALYST ON THORIA MODIFIED SILICA SUPPORT

BET surface area has been determined for 3% and 10% Ni catalyst on thoria modified silica support. The Th/Si mole ratios are 0, 0.0036, 0.0061, 0.0154, 0.031, 0.049 and 0.071. The BET area is calculated from nitrogen desorption method using a mixture of 30% nitrogen and 70% helium as a carrier gas in thermal conductivity detector of a gas chromatograph. The BET area of pure dried support is 239 m2/g and that of thoria modified dried support ranges from 226 m2/g to 167 m2/g. The calcined ThO2/SiO2 support gives BET area from 231 m2/g to 181 m2/g. In 3% Ni loaded support the area ranges from 222 m2/g to 164 m2/g while in 10% Ni loaded support the area decreases from 208 to 156 m2/g. 3% loaded Ni is a better catalyst.read more

---

A W K KHANZADA ,

POTENTIOMETRIC STRIPPING ANALYSIS OF HEAVY-METALS IN GASOLINE AND DUST PARTICULATE

Determination of heavy metals such as Cd, Pb and Cu by potentiometric stripping analysis (PSA) in gasoline and dust particulate, was made. Initially optimum pH of the analyte, plating voltage and electrolysis time of the technique was established. The test samples were taken from service station and different locations at Peshawar. High octane blend, regular and super gasoline contained range mean levels of Pb 0.275-0.614 gm L-1 and Cu 0.0042-0.008 gm L-1 while Cd was not detectable. High speed diesel had mean values of Cd 0.003, Pb 0.0038 and Cu 0.023 gm L-1. The dust particulate matter contained maximum levels of 3.92, 84.23 and 49.67 gm Kg-1 of Cd, Pb and Cu respectively depending upon the position on the road-side.read more

---

NOOR AHMAD ,A SATTAR ,LIAQAT ALI KHAN ,

ON THE FORMATION OF IRON(III) BENZOYLACETANILIDE COMPLEXES - STRUCTURAL, ELUCIDATION BY TGA, IR, ELECTRONIC-SPECTRA, CONDUCTANCE AND POTENTIOMETRIC STUDIES

Two new series of iron(III) benzoylacetanilide complexes have been prepared and characterized by elemental analysis, TGA, IR, electronic spectra and conductance measurements. The elemental analyses show that the composition of the solid complexes produced have 1:2 and 1:3 (M:L) molar ratios. TGA and IR spectra indicated that the bonding in 1:3 (M:L) complexes takes place through the enolic-OH group and anilied N- linkage only while 1:2 (M:L) complexes it takes place through interaction of carboxy OH or SH together with the enolic OH group through H+ ion displacement. Electronic spectra indicated octahedral geometry around Fe(III) ion. Conductometric and potentiometric titrations indicated the formation of 1:1, 1:2 and 1:3 (M:L) complexes in solutions. The values of the conditional stability constants calculated by potentiometric techniques depend on molecular structure. Deviation of the pK1 vs log K plots slopes from unity is attributed mainly to steric effect, pi-electron back donation from the metal ion or structural changes in the ligand.read more

---

AKILA L SALEH ,A ELDEKKN ,SAMY M ABUELWAFA ,MOHAMED ABD ELMOTTALEB ,ABD EL RAHEEM ,

KINETICS OF OXIDATION OF MN(II) IN [SIMNIIW11O40H2]6- TO MN(III) BY PEROXYDISULFATE ION

The pseudo-first order kinetics of oxidation of Mn(II) to Mn(III) in heteropoly ion, [SiMnIIW11O40H2]6-, was studied at 50-degrees-C using peroxydisulphate ion as an oxidizing agent. The pH was kept at 5.0 and ionic strength was 2.0 in Na2SO4. It was found that over a wide range of concentrations of S2O82- ion the kobs varies linearly with [S2O82-]1/2 rather than [S2O82-], values suggesting that oxidation of Mn(II) is preceeded by homolytic dissociation of S2O82- ion into SO4- ion radicals.read more

---

MAJID MUMTAZ ,SHABBIR ZUBAIRI ,

KINETICS OF AG+ CATALYZED OXIDATION OF MN(II) TO MN(III) IN K6[SI MNW11O40H2] WITH PEROXYDISULFATE ION

Mn(II) in the hetropoly ion [Si Mn W11O40H2]6- was oxidised to Mn(III) by S2O8(2-) using Ag+ as catalyst and the psuedo first order kinetics of this oxidation was studied spectrophotometrically at 35-degree-C, ionic strength 0.2 maintained by Na2SO4 and pH 5.0. The reaction rates were found to be independent of hetropoly ion concentration and shows first order dependence on Ag+ and S2O8(2-) concentrations, suggesting oxidation of Ag+ as rate determining step.read more

---

SHABBIR A ZUBAIRI ,MOHAMMED FAZZAL ULLAH ,

INSTRUMENTATION FOR CHEMILUMINESCENCE AND BIOLUMINESCENCE ASSAYS (PART-I)

Bioluminescent and chemiluminescent emissions can easily be measured with any instrument sensitive to light. The conventional instrumentation available for measuring chemiluminescence and bioluminescence is described. The advantages and disadvantages, and also a possible development in the foreseeable future for these equipments which are based on batch techniques are also discussed.read more

---

A NABI ,

SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF CHROMIUM AND IRON IN CHROMITE ORE

We have developed an experimental procedure to perform analysis of chromium and iron simultaneously in chromite ore. Chromium and iron were extracted from fused ore by one molar sulphuric acid. The reduction of Cr(VI) to Cr(III) and Fe(III) to Fe(II) was carried out by sodium sulphate. Iron was estimated as [Fe (phen)3]2+ (phen = o-phenanthroline) and chromium as Cr(III) ions in solution. In several determinations of synthetic mixture the accuracy of the result for chromium and iron was found to be within 2.0%.read more

---

M FAZAL ULLAH ,Z U SIDDIQUI ,

CATION-EXCHANGE STUDIES ON HYDROUS CHROMIUM-OXIDE

The exchange behaviour and the pH dependence on adsorption of first transition series metal ions have been studied over hydrous chromium oxide (HCO). The metal ions Mn(II), Fe(II), Cu(II), Co(II) and Zn(II) were separated from one another over HCO column using buffers of pH 3, 4.5, 5 and 6.read more

---

JAVED IQBAL ,MUSARAT GUL ,M LATIF MIRZA ,KHURSHID RAHIM ,

A QUANTITATIVE ASSESSMENT OF INHALABLE PARTICULATE MATTER POLLUTION IN METROPOLITAN KARACHI

Solid pollutants at four different sites at Karachi were collected by dry deposition for a month. Water soluble portions were analysed for arsenic, cadmium, copper, manganese, nickel, lead, antimony, zinc, sodium, potassium, ammonium, chloride, nitrate, phosphate and sulphate. The probable sources of emission of these elements and their correlation with each other is discussed.read more

---

HAMIDA TABASSUM ,SAEEDAN BEGUM ,