VOLUME 19, NO1, MAR 1997

MO calculations to interpret optical spectra of MV: and related species

The higher reduction products of dications of methyl viologen (MV2+), diquat (DQ(2+)) and n-butyl viologen (BV2+) i.e. MV; DO; and BV; respectively were prepared and their spectra recorded. MO calculation have been carried out to interpret the optical spectra of MV; and DQ:. A good agreement was obtained between experimental and predicted singlet transitions for MV: while in case of DQ: the agreement for singlet ransition at longer wave length was at variance. In case of MV:(I) the observed transition are 3.1307 and 3.3056 eV while calculated one are 3.1352 (B-2u) and 3.4006 (B-3u) eV respectively where as in case of DQ: (II) the observed transitions are 3.0228 and 3.1307 eV while the calculated one are 2.6032 (B-1) and 3.0873 (A(1)) eV respectively.read more

---

A Y KHAN ,M S SUBHANI ,M YOUSAF ,M MOHAMMAD ,

Photodegradation of PVC in air

Photodegradation of PVC films was done in simple atmosphere of air in order to get idea about changes in PVC in an atmosphere similar to outdoor exposure. The photodegradation of PVC in air shows a different UV spectrum as compared to me degradation in nitrogen. Absorption shifts towards smaller wavelength and the fine structure disappears. Carbonyl groups are formed the molecular weight changes with photodegradation due to chain scission and crosslinking.read more

---

FARINA KANWAL ,MOHAMMAD SALEEM KHAN ,

The effect of some salts and (NaPO3)(n) polymer on viscosity of Na-montmorillanite slurry

The rheological properties of the slurry that have been prepared Na-montmorillonite clay have been determined, the effects of NaCl, KCl, LiCl, CaCl2 and MgCl2.6H(2)O salts and (NaPO3)(n) polymer have also been investigated at different concentrations. The changes in rheological properties of Na-montmorillonite slurry when salts have been added to concentration have been commented. Information on the vander waals and electrostatical interaction between the colloidal clay the bentonite-water systems is given.read more

---

NURFER GUNGOR ,SUKRAN DILMAC ,

Transition metal complexes of biologically important chelating agent

The coordination chemistry of 1-(N-beta-ethyl-morpholine)-5-nitromidazole, a chemotherapeutic agent, is carried out and is reported. This ligand can be compared with that of DME and DMP in its structure. In this paper the synthesis and characterization of 1-(N-beta-ethyl-morpholine)-5-nitroimidazole(EMNI) compounds of the type M(ENMI)X-2 where M = Co(II), Ni(II), Cu(II), Cd(II) and Hg(II), while X=Cl, Br, I, and NO3 and based on the usual physical methods i.e. spectroscopic, magnetic and conductance measurements. Thermal studies (thermogravimetric analysis) are carried out to explain the mode of decomposition, results are reported and discussed.read more

---

TAL ALI KHAN ,SHAD ALI KHAN ,SAEED UR RAHMAN ,

Synthesis of heterobimetallic telluro-acyl complexes

The mu-alkylidene dimetal complexes [M Fe(mu-C6H3Me2-2,6)(CO)(5)(eta-C5H5)], (M = Cr, Mo or W) reacted with elemental tellurium yielding the heterobimetallic compounds [M Fe (mu - eta(2) - TeCC6H3 Me-2-2,6)(CO)(5) (eta - C5H5)]. Similarly, the reaction between [Mo Fe(mu - CC6 H4Me-4)(CO)(5)(eta-C5H5)] and tellurium afforded the complex [MoFe (mu - eta(2) - Te C C6H4 Me-4)(CO)(5) (eta - C5H5)].read more

---

BASHIR A NASIR ,ANTHONY F HILL ,A STONE ,F GORDON GORDON ,

Determination of free sterol content of various brands of eggs, ghee/oils, using immobilized enzyme column in a flow system

A flow system containing immobilized cholesterol oxidase column is applied to the analysis of various brands of eggs, ghee, oil etc., for the free sterol content. Eggs of domestic hens have significantly low content of free cholesterol as compared to cholesterol level in farmy eggs. The total sterol content of the ghee is lower as compared to oils, probably because of the loss of sterol during bleaching, blending and refining. The sterol content varies widely among different oils/ghee.read more

---

M ANWAR ,M MASOOM YASINZAI ,

Studies on the chemical constituents of different varieties of black tea

This study reports chemical constituents of 28 varieties of tea imported from 15 different countries. Water extract, total ash and fiber ranged between 35.3 - 47.4, 4.,7 - 6.39 and 7.11 - 17.23 percent (w/w) respectively. These values correspond to the standards established by the International Standards Organization (ISO). Caffeine in all the varieties was at the lower side of the required value ranging from 1.08 - 2.38/100 g. Tannins varied between 5.9-11.9% (w/w). Tea merchants in Pakistan should import tea containing appreciably high amounts of Caffeine so that after blending, tea brands of good Caffeine contents may be produced.read more

---

R B QADRI ,ASKARI BEGUM ,KHALID JAMIL ,SADIQA SHAKIR ,ABDUL ALI ,

Studies on physico-chemical nature of ground water of Korangi/Landhi (Karachi)

65 water samples collected from wells, handpumps, and borings, have been analysed to assess the quality of ground water of Korang/Randhi (Karachi). Large variations in the levels of various physicochemical parameters and major chemical constituents, among the samples collected from different localities of the area, have been observed. Possible causes of the changes in chemical composition of the water have been identified and discussed. Seepage of domestic and industrial waste water and sea water intrusion seem to be the main sources of contamination of ground water. The quality of the water has also been compared to that of some major cities of Pakistan. The chemical composition of the ground water has been substantially deteriorated and the water as such is not suitable for human consumption as well as general industrial use.read more

---

S NAEEM MAHMOOD ,SITWAT NAEEM ,

Comparative studies of stability constants of trace metals salicylhydroxamic acid complexes

Salicylhydroxamic acid forms complexes with trace metals such as Fe3+, Cr3+, Mn2+, Ca2+, Zn2+, Cd2+, Cu2+, Mg2+, Ni2+, Co2+ and Al3+. The stability constants of these complexes formed have been determined by a potentiometric method. The data obtained were computed with the help of computer program ''BEST'. The resulted ''beta'' values were compared.read more

---

S ARIF KAZMI ,FOUZIA H REHMANi ,ZAHIDA T MAQSOOD ,

Selected trace-metal levels in local vegetables procured from Punjab, Pakistan

Heavy trace metal content of thirty three vegetable samples procured from local markets/farms of Rawalpindi/Islamabad is estimated by wet digestion atomic absorption method. The metals include Fe, As, Pb, Hg, Cd, Cr and Ni. The families of vegetables investigated include: Cucurbitaceae, Solanaceae, Cruciferae, Liliaceae, Chenopodiaceae, Leguminosae, Umbelliferae, Araceae, Malvaceae, Zingiberaceae, Asclepiadaceae, Compositae and Labiatae. The data are reported at 99% (+/- 2S) confidence level for triplicate measurements with an overall reproducibility within +/- 1% compared with standard samples. Comparison of avererages through t-test indicates that each vegetable group is distinctly different from other in terms of heavy trace metal content. Maxima Fe concentration was shown by parsley at 29.515 mu g/g, dry weight. Nickel was found to be 1.985 mu g/g (dry weight) in carrot (edible part-root) in the vegetable family Umbelliferae. Arsenic was not found above detection limit except in ghia tori (edible part-fruit) of Cucurbitaceae family which had As at 0.445 mu g/g, dry weight. With a couple of exceptions, the overall trace metal levels in the vegetables investigated were found to be within the safe limits laid down for human consumption.read more

---

M JAFFAR ,KHALID MASUD ,