VOLUME 17, NO3, SEPT 1995

X-ray diffraction studies of Ru:Ag/alumina supported bimetallic system

Ru:Ag alumina supported bimetallic system was prepared by co-impregnation method and characterized ruing X-ray diffraction technique. On the basis of experimental data the intensity lines corresponding in Ag, Al, Ru, RuO with Ag occurring at the surface of Ru as island were found The shift in the angle of diffraction and de change in the intensity of the Ru peaks samples indicates the presence of particles greater than 5 mo dispersed randomly on the catalyst surface. At 0.02% Ru:Ag atomic ratios no XRD intensity Line of Ag was found indicating that Ag is present on the surface in the form of very small particles. The metal dispersion calculated from the XRD data reveals geometric effect of Ag rather than any Ru-Ag electronic interaction.read more

---

S TAJAMMUL HUSSAIN ,

Measurement of carbon-14 in air released from a research reactor

Measurement of C-14 in air, generated from a low power (300 kW) training reactor, has been carried out A simple method has been applied using barium hydroxide for the absorption of CO2, followed by conversion of barium carbonate to benzene for analysis using liquid scintillation counting. Air from the reactor stack and from various sites in the immediate vicinity has been analysed for the determination of C-14. In order to assess the environmental hazards to the population, the collected data has been used to calculate radiation dose due to C-14.read more

---

IHSAN ULLAH ,

The effect of alloying on selectivity and activity for carbon monoxide hydrogenation over Ru-Mn/SiO2 supported system

The Ru:Mn/SiO2 supported system with various level of Mn war prepared by co-impregnation method dispersed on high surface area SiO2 support. The system war investigated for CO hydrogenation reaction. The catalytic activity and product selectivities data reveals electronic and ensemble street produced by the addition of Mn to Ru/SiO2 system It is suggested that addition cf Mn produces new surface sites Ru:Mn bimetallics which modify the catalytic behaviour electronically and geometrically.read more

---

S TAJAMMUL HUSSAIN ,

Static secondary ion mass spectrometry (SSSIM) and X-ray photoelectron spectroscopy (XPS) studies of polycrystalline Ag/Ru supported bimetallic alloy system

Polycrystalline bimetallic Ag/Ru system was prepared by co-impregnation method supported on high surface area alumina support The system which forms a complicated bimetallic supported alloy was studied ruing UHV techniques SSIMS and XPS. On the basis of experimental evidence, the presence of Ru, Ag and Ru Ag bimetallics were found with Ag occurring on the surface of Ru masking the emission of Ru. The electronic interaction between Ag and Ru shifts the Ru electron binding energy towards lower side. The nature of support have an affect on the Ru electron binding energy and the presence of impurities on the system distort the peak shape of the main metal, Addition of As increases the surface area of the system The data has been discussed in terms of modification of the surface geometry by the addition of Ag which forms bimetallic alloy of different shape and structure.read more

---

S TAJAMMUL HUSSAIN ,

A computational method for calculation of dissociation constants of benzoic acid and sodium benzoate

The experimental potentiometric data have been used for the determination or thermodynamic dissociation constants of benzoic acid and sodium benzoate. A computer program in GW-BASIC has been used to calculate the dissociation constants pK(a) valves of these substances from experimental data The effect of temperature, solvents and solvent composition on dissociation constant pK(a) values has also been carried out. The pK(a) values are as follows: [GRAPHICS]read more

---

A W K KHANZADA ,SAEED UDDIN ,A T MUFTI ,K M BHATTI ,

A comparison of the stabilities of some rare earth metal soap stabilizers

Rare earth (Dy, Nd, Pr and Tb) metal soaps that can be used as stabilizers for PVC, were synthesized from lauric acid. The thermal stability studies of these samples were conducted by employing differential thermal analysis in dynamic nitrogen atmosphere. The results reveal that these metal laurates start to degrade at temperatures higher than those required for lauric acid. Dysprosium laurate is the most stable having a melting point of 145 degrees C.read more

---

FAZAL MAHMOOD ,RIZWAN HUSSAIN ,

Circular dichroism studies of Co(II), Ni(II) and Cu(II) complexes of antibiotic (+)-ampicillin formed in solution

Circular dichrosim studies show that (+)-Ampicillin, a broad spectrum beta-lactam antibiotic, forms soluble complexes with Co(II), Ni(II) and Cu(II) ions in aqueous solution. Complexation of these metal ions with (+)-ampicillin ((+)-amp) is indicated by appearance of Co bands in crystal field region. In solution, complexes of composition [M((+)-amp)(2)](2+) are formed at pH 6.5-8.0 which have 2-3 Cotton bands in 14,706-23,697 cm(-1) region. The CD band ellipticity is linearly increased with concentration of the components under optimum conditions between 0.002-1.0 mol L(-1). The Cotton bands in these systems are interpretted in terms: of electronic excitations to unidimensional levels arising due to lower symmetry of these complex ions.read more

---

M JAMIL ,NASIR AHMAD ,CHRISTY MUNIR ,

Estimation of enthalpies of formation of highly reactive organic compounds

A simplified scheme of atom equivalents to relate ab initio total electronic energies at the 6-31G* basis set level to enthalpies of formation is applied to free radicals and classical carbocations. The estimations are quite satisfactory and the average errors are similar to experimental uncertainties as well as to other thoretically determined values. Some possible further extensions of the method are pointed out.read more

---

EDUARDO A CASTRO ,

Synthesis and some reactions of 3,5-diaryl cyclohex-2-ene-6-(1',2',4'-triazol-5'-yl-3'-thioxo)-1-one

6-carbethoxy-3,5-diaryl cyclohex-2-enone (1) was condensed with thiosemicarbazide ia boiling pyridine to give 2 which reacted with some electrophiles and nucleophiles to give substituted cyclohexenones.read more

---

FEKRIA MOHAMED AHMED SOLIMAN ,

Some new 4-oxo-4H-1-benzopyran derivatives

Some 4-oxo-4H-1-benzopyrans bearing the 1,3,4-thiadiazole moiety were prepared. These include 2(2'-amino or acylamino-1,3,4-thiazol-5'-y1)-4-oxo-4H-1-benzopyrans (flavone analog) and some N-(1,3-thladiazolyl-4-oxo-4H-1-benzpyran-2-curboxamides.read more

---

H M EL SHAAER ,S S IBRAHIM ,M A ABDEL HALIM ,