VOLUME 18, NO1, MAR 1996
12
 
Determination of entropy and enthalpy values of metal gallic acid complexes and their comparison with iron gallate

S A KAZMI ,F SULTANA ,Z MAQSOOD ,

The entropy and enthalpy values ed complex formation between 3,4,5 trihydroxybenzoic acid and Cu(II), Cr(II), Mn(II), Mg(II) and Ca(II) were determined and compared with the iron gallic acid complexes, they were found to be comparable. It was also found that they show very large entropy values. When those values were compared with other complexes of the same nature from literature, following points were noteworthy. 1. Monodentate ligands do not show any drastic entropy change with trivalent metals as compared to divalent metals. 2. Polydentate ligands show very high entropy values with tripositive metal as compared to dipositive metals. 3. Non transition metals show low entropy values with chelating agents as compared to transition metals.
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Preconcentration and determination of copper, cadmium, nickel and zinc in drinking water by atomic absorption and 6-methyl-2-pyridinecarboxyaldehyde-4-phenylsemicarbazone as complexing reagent

P DAS ,M Y KHUHAWAR ,

A method has been developed for the extraction and preconcentration of copper, nickel, cadmium and zinc from water samples with 6-methyl-2-pyridinecarboxaldehyde-4-phenylsemicarbazone (MPPSC) into chloroform at pH9. Chloroform was evaporated and the residue was digested in nitric acid. After adjustment of volume, metal ions were determined using air-acetylene flame atomic absorption spectrometer. The recovery of metal ions were 95-100% with coefficient of variation (C.V) within 3.2%. Preconcentration obtained was 12-30 times. The method was applied for the determination of the metal ions in drinking water of Hyderabad city and Jamshoro.
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Some aspects of spectrophotometric determination of amino acids using o-phthalaldehyde as a chromogenic reagent

M AMINUDDIN ,M A SHAH ,Z H CHOHAN ,

A rapid, sensitive and convenient spectrophotometric method has been developed for the determination of Amino acids. At lower concentration (3 x 10(-7) mol/ml) of amino acids the Beer-Lambert law is obeyed ?he absorptivities of me o-phthalaldehyde (OPA)-adducts formed with different amino acids have been examined and calculated The OPA-derivative is found to be composed of amino acid, OPA and a thiol in a molar ratio 1:2:1.
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Trace level determination of alkaline earth metals in high purity uranium using ion chromatography

S B BUTT ,M RIAZ ,

An improved ion chromatographic OC) method has been developed for the determination of magnesium and calcium in high purity uranium The extraction of alkaline earth metal ions present in samples were optimized Icing tributyl phosphate (TBP) as an extractant Excellent recoveries of 99% were achieved for investigated alkaline earth metals at trace level. The relative standard deviations (RSD'S) for Mg2+ and Ca2+ ions for the ion chromatographic method were 0.5 and 0.8 ppm respectively. The analytes were also analyzed with atomic absorption spectroscopy (AAS) as a counter technique.
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Determination of gaseous elements in metals and metal powders

S K DURRANI ,K A SHAHID ,J AKHTAR ,N A CHUGHTAI ,

Presence of gaseous impurities affect the mechanical and corrosion resistance properties of metals and alloys. selected samples of metal and metal powder have been analyzed for the determination of gaseous impurities like hydrogen, oxygen and nitrogen by inert-gas fusion extraction technique. The accuracy of the method has also been verified for hydrogen, oxygen and nitrogen. All results date. was statistically evaluated and compared with the literature values.
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Emission spectrographic analysis of aluminum base materials by DC-ARC excitation

R HUSSAIN ,S HUSSIAN ,D MOHAMMAD ,

An emission spectrographic method employing de-are excitation has been described for the determination of Bi, Cr, Cu, Fe, Mg Mn, Ni, Pb, Si and Zn in aluminum base materials. The samples were dissolved in nitric acid, dried and converted to oxide form by heating in a tube furnace at 900 degrees C under oxygen atmosphere before analysis. Treated samples were mixed with graphite in 2:1 ratio and excited in 10 Amp dc-are for 30 seconds. The lowest detection limits for different elements lie between 10 and 40 ppm.
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Thermal studies on chelates of 2-hydroxy-4-aminobenzoic acid with group IB and IIB metals

C M ASHRAF ,B KHAN ,M Z IQBAL ,

Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) have been employed in the present work to investigate thermal stability, stoichiometry and cleavage patterns of the chelates of 2-hydroxy-4-aminobenzoic acid (sodium salt) with group IB, IIB metals and Ni. The decomposition patterns revealed interesting information about bonding situations and thermodynamic values of the complexes.
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Determination of lead in aqueous system by flow injection technique coupled with spectrophotometer

S KHATOON ,M YAQOONB ,A NABI ,

A spectrophotometric flow injection procedure for the determination of lead is described. The procedure is based on measurement of absorbance from the colour produced by the reaction of lead with sodium sulfide in the presence of ammonia. Results are presented for lead at a sample throughput of 60 h(-1) and repeatability is 1.5% at 1000 mg/dl. The method is well demonstrated by analyzing lead in lead-ores which were pre-determined by using atomic absorption spectroscopy.
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A new spectrophotometric method for the determination of cyanide from waste water

U A KHAN ,M SARWAR ,F JAMSHAID ,

Cyanide reacts with N-Bromosuccinimide followed by the reaction with pyridine-barbituric acid to produce a pink colour having maximum absorbance at 580 nm Ihs method in reasonably sensitive, accurate, precise and less time consuming. This method was successfully applied for the determination of cyanide from waste water.
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Metallochromic properties of melamine-derived organic reagent N-(2'-thienylmethylene)-2,4,6-triamino-1,3,5-triazine

Z H CHOHAN ,M AMINUDDIN ,

A new organic reagent N-(2'-thienylmethylene)-2,4,6-triamino-1,3,5-triazine has been synthesised and studied spectrophotometrically for its metallochromic properties towards Fe(III), Fe(II), Cu(II), Co(II), NI(II) and Zn(Il) metal ions. The reagent forms coloured complexes between pH 5.0 and 6.0. Concentration versus absorbance relationship is linear up to a level as low as 2 ppm.
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