VOLUME 19, NO2, JUN 1997

Redox properties of ethylenediaminetetra-acetic acid complex of the molybdenum(V) Mo2O42+ in aqueous acidic solution

The kinetics of the equilibration of molybdenum (V,V) complexes of Mo2O42+ (A) and Mo2O4Y2- in the presence of excess of EDTA (H4Y = ethylenediaminetetraacetic acid) have been studied by spectrophotometry methods at 25 degrees C, and ionic strength, I=1.50M (LiClO4). First order rate constants at constant hydrogen-ion concentrations in the range [H+] = 0.2-1.8M may be expressed as k(aq) = a[EDTA]+b. The hydrogen dependences of a and b, corresponding to the formation and dissociation processes respectively are not simple For the dissociation process the equation b = [H+](4)/(1+b(2)[H+](3)) gives a good fit the experimental data. Contributions from terms in [H+] and [H+](2) in the denominator can not be ruled out however. An inerse hydrogen-ion dependence is apparent for a but the precise form is less certain. The substitutional and redox properties of mono- and binuclear complexes of molybdenum with different ligands N, O and S atoms are of interest as models for molybdenum enzymes [1]. It has been now established that most of these enzymes contains two molybdenum atoms which are redox active. The molybdenum are in oxidation state (VI) in the oxidized form, and can utilize other oxidation states, in some cases down to (III) in the reduced form [2].read more

---

Z MEHMOOD ,ABBAS H KHAN ,K MAHMOOD ,

Physicochemical studies of zirconia and magnesia doped zirconia ceramic powder

Spherical fine zirconia (ZrO2) and 9 mol % magnesia doped zirconia (MgO-ZrO2) ceramic powders (diameter of similar to 0.2 mm) have been synthesized from a hydrothermally treated sol of zirconium and magnesium salts by spray pyrolysis. The results revealed that synthesized powders can be sintered into uniformly sized fine grained ceramic of > 97% theoretical density at temperature as low as 1100 degrees C. The phases, purity, crystallite size, agglomeration structure, particle size, specific surface area, pore size distribution and porosity of ZrO2 and MgO-ZrO2 ceramics were measured by XRD, SEM, N-2-gas adsorption and Hg-diffusion techniques. The results of X-ray diffraction and scanning electron microscopy showed that the ZrO2 and MgO-ZrO2 remained amorphous up to 700 degrees C, but on increasing the heat treatment temperature to around 1200 degrees C for 8 hrs. monoclinic crystals were obtained. Thermogravimetric (TG) and differential scanning calorimetric (DSC) techniques were used to measure the burnout temperatures and enthalpy (Delta H) of polyvinyl alcohol (PVA) and methylcellulose (MC) polymers used as binders. Burnout of these polymers is 100% in an oxidizing atmosphere; 90% burnout was achieved in an inert atmosphere.read more

---

K A SHAHID ,JAVED AKHTAR ,N A CHUGHTAI ,SHAHID KHAN DURRANI ,

Electrophile-induced nucleophilic substitution reactions of 7-trimethylamine-7-carba-nido-undecaborane 7-Me3N-nido-7-CB10H12

The AlCl3-catalysed chlorination and deuteration reactions of 7-Me3N-nido-7-CB10H12 are presented. When 7-Me3N-nido-7-CB10H12 is treated with anhydrous HCl in the presence of AlCl3 electrophile induced nucleophilic chlorination occurs to yield 7-Me3N-9-Cl-nido-7-CB10H11 as the major product with a minor component of the disubstituted species, 7-Me3N-6,9-Cl-2-nido-7-CB10H10. When DCl in the presence of AlCl3 is used deuterium substitution occurs in addition to chlorination and with the formation of 7-Me3N-9-C-1-1,4,5,6,10-D-5-nido-7-CB10H10. A similar dichlorinated by-product 7-Me3N-6,9-Cl-2-1,4,5,10-D-4-nido-7-CB10H6 is also obtained. The structures of all isolated compounds were unambiguously determined via elemental analyses, IR mass spectroscopy, H-1, B-11 and 2-D B-11- B-11 NMR spectra.read more

---

SHAH ALAM KHAN ,

Spectrophotometric determination of nickel in nickel-aluminium alloy and palladium in palladium-barium sulphate using 6-methyl-2-pyridinecarboxaldehyde-4-phenylsemicarbazone as a complexing reagent

A new spectrophotometeric reagent 6-methyl-2-pyridinecarboxaldehyde-4-phenylsemicarbazone has been synthesised and its colour reactions with cadmium(II), cobalt(II), cobalt(III), copper(II), nickel(II), palladium(II) and zinc(II) is studied spectrophotometrically. Their molar absorptivities for metal chelates are observed in range of 1.2-6.7x10(4) L.mole(-4) cm(-1). Reaction time, solution stability and solvent extraction from aqueous to organic phase have been examined. The complexes are easily extractable in chloform. Each of the complex obeys the Beer's law. The method is applied for the determination of nickel in nickel-aluminium alloy and palladium in palladium-barium sulphate.read more

---

PRITAM DAS ,M Y KHUHAWAR ,

Determination of major, minor and trace metals in drinking water samples of Lahore and Kasur

Drinking water samples of Lahore and Kasur regions were collected from 15 different sampling areas. Physico chemical parameters such as pH, conductivity, hardness and alkalinity were measured immediately. The major and minor metal constituents were determined using Atomic Absorption Spectrophotometer. Sodium concentration was found relatively high in Lahore and more so in Kasur water samples. The results have been discussed with reference to the local soil conditions: and industrial waste pollutants finding their way to the underground water streams.read more

---

DIN MOHAMMAD ,A MATEEN ,H A ZAIDI ,M HUSSAIN ,M TAHIR ,

Kinetic measurements of nitrite by bromopyrogallol red

A kinetic spectrophotometeric method for the determination of trace amounts of nitrite (0.2-1.0) mu g/ml has been proposed based on its catalytic effect on the reaction between potassium bromate and bromopyrogallol red in acidic medium. The reaction is monitored spectrophotometrically by appearance of band at 348 nm with respect to blank by fixed time method (15 min). The method has been applied for quantitative determination of nitrite in water samples with coefficient of variation (C.V) within 4.2% (n=3). Pho?oc?H????arameters such as pH, conductivity, hardness and alkalinity were measured immediately. The major and minor metal constituents were determined using Atomic Absorption Spectrophotometer. Sodium concentration was found relatively high in Lahore and more so in Kasur water samples. The results have been discussed with reference to the local soil conditions: and industrial waste pollutants finding their way to the underground water streams.read more

---

G M MASTOI ,M Y KHUHAWAR ,I A ANSARI ,A A KHASKHELI ,

Levels of some major and trace elements in commercial mango fruit juices determined by flame atomic absorption spectrometry

A simple and low cost method has been described for the determination of Na, K, Ca, Cr, Fe and Zn in mango fruit juices using atomic absorption spectrometry. The method involves digestion of samples with nitric acid at 105 degrees C on an oil bath for 45 minutes. Relative standard deviation for major elements was better than 1% and for trace elements around 7%. The concentration ranges for Na, K, Ca, Cr, Fe and Zn are 81-300, 49-570, 36-181, 0.075-0.250, 0.80 -2.03 and 0.05-0.70 mu g/g respectively.read more

---

MUHAMMAD ZAHEER ASGHER ,SHAHIDA B NIAZI ,FARZANA MAHMOOD ,

Monitoring of water pollution in the Kabul river (Pakistan) under low flow conditions

The quality of the Kabul river water fi om upstream of Warsak Dam to its confluence with the Indus has been investigated by measuring 15 physical and chemical parameters during low flow conditions between September 1992 and March 1993. These values have been compared with standard conditions required for the maintenance of fisheries and aquatic life. The Kabul river water showed high suspended solids which range between 10-800 mg L-1. Conductivity values were also high and a maximum value of 1415 was recorded below the Akbar tannery on the Naguman branch. High levels of ammonia, nitrites and nitrates existed in the Shah Alam branch and in the lower main river. Sulfide concentration were high over the whole stretch of the river.read more

---

SHAH ALAM KHAN ,MUMTAZ KHAN ,

Study of matrix effects on determination of trace elements in aluminium using inductively coupled plasma atomic emission spectrometry (ICP-AES) (II) criterion for selection of spectral lines

Selection of spectral lines for determination of twelve impurities in aluminium has been considered in light of the true detection limits as the basic criterion, The lines with lowest true detection limit values are recommended for determination of these elements in the aluminium matrix.read more

---

KHURSHID ANWAR ,DIN MUHAMMAD ,MOHAMMAD SALEEM ,

Reverse phase liquid chromatographic separation and determination of Bismuth(III), Copper(II) and Palladium(II) using dimethyl dithiophosphoric acid as complexing reagent

Bismuth(III), Copper(II) and Palladium(II) complexes of dimethyl dithiophosphoric acid (DDTP) from acidic media are extracted in chloroform and separated on YMC ODC 5 mu m column (150 x 4.6 mm id), when eluted isocratically with a mixture of acetonitrile: methanol: water (70:20:10 v/v/v) with a flow rate 0.6 ml/min acid detection at 295 nm. Linear calibration curve were obtained with 25-125 mu g aliquot of each of metal with detection limits of 0.4-0.8 ng/injection. The method is applied for the determination of copper in copper wires.read more

---

MOHAMMAD Y KHUHAWAR ,A H CHANNAR ,S N LANJWANI ,