VOLUME 13, NO4, DEC 1991

KINETICS OF OXIDATION OF HEXACYANOFERRATE(II) WITH CHLORAMINE IN AQUEOUS-MEDIUM

The kinetics of the oxidation hexacyanoferrate(II) with chloramine has been investigated spectrophotometrically at 25.0-degrees-C in buffered aqueous solution at pH 8.5-9.50. Reaction docs not show significant dependence on [Fe(CN)6(3)] in the reaction of [Fe(CN)6]4- with a large excess of chloramine solution, but it does show in the reaction of [Fe(CN)6]4- with a similar concentration of chloramine. With chloramine in excess, the rate as given by -d/dt [Fe(II)] = k(obs)[Fe(II)]. The result obtained is interpreted in terms of a reaction mechanism in which the first stage, Fe(II) + NH2Cl --> Fe(III) + degrees-Cl, can occur by an irreversible or reversible process. read more

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A H KHAN ,

DECOMPOSITION KINETICS OF METAL ACETATES

Thermal decomposition of acetates of potassium, cobalt, zinc, mercury and lead have been investigated using thermogravimetric technique (TGA), under constant flow of nitrogen. The results indicate that major products are acetone, carbon dioxide, oxygen, depending on whether the final solid products is that of oxide or the metal. Kinetic parameters of the thermal decomposition of these metal acetates were investigated on the basis of their respective thermal curves. Calculation of reaction order and an activation energy were carried out by the Coats-Redfern's method and also by Horowitz-Hugh's method giving comparable results. read more

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H AHMAD ,F MAHMOOD ,M AFZAL ,

SORPTION OF BENZENE ON CHROMOSORB POROUS POLYMERS, AND EVOLUTION OF BET SURFACE-AREAS FROM THEIR ADSORPTION-ISOTHERMS

Sorption of benzene on chromosorb (101-105) has been studied from gas chromatography retention data. The effect of sample size and thus surface coverage on the heats of sorption was also assessed, BET surface area measurement has also been made using benzene sorptive. read more

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B A COLENUTT ,M KHAN ,J ARA ,

EFFECT OF ELECTROLYTES ON THE DISTRIBUTION OF TRICHLOROACETIC-ACID BETWEEN BUTANOL AND WATER

The distribution of trichloroacetic acid between the aqueous and organic phase containing varying amounts of electrolytes was studied at room temeprature 25-degrees-C +/- 1. A correlation was derived between the distribution of acid and ionic strength of the partitioning medium. It was found that in the presence of anions I-, Cl-, Br- , SO4-, and cations Na+, K+, Ba++, the distribution coefficient of acid increased gradually with increase in the concentration of both groups of ions. However in the presence of F- and Al+3 a reverse effect on the distribution of acid was observed. read more

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F BEGUM ,I KHATTAK ,

ROLE OF POLYVINYLPYRROLIDONE ON MASS-TRANSFER PROCESSES OF AGBR AND AGI

The effect of photographically active substance, like polyvinylpyrrolidone (PVP), on the rate of mass-transfer processes has been investigated in course of Ostwald-ripening of AgBr and Agl. The influence of PVP is determined at the interface processes of ionic crystals in the presence of various concentrations of PVP in the system, AgBr-Br-82- and AgI-I-131-. Since a very low supersaturation lies during Ostwald-ripening therefore under these conditions very low concentration of substance is very effective which adsorbs on the surface of AgBr and AgI crystals and reduces the rate of mass-transfer processes, which can be quantitatively measured by means of radiochemical measuring technique. read more

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N ABBASI ,A WINZER ,

ELECTRICAL CONDUCTANCE AND IONPAIR FORMATION OF COBALT(II) COMPLEXES OF ACETOPHENONETHIOSEMICARBAZONE HALIDES IN METHANOL-WATER MIXTURE AT 25-DEGREES-C

Conductance of CO(II) complexes of acetophenonethiosemicarbazone halides is measured at 25-degrees-C in methanol-water mixture (32.63 < D < 73.42). The conductance parameters derived from the Fuoss-Onsager conductance theory indicate that the solvation of halides decreases with the decrease of the dielectric constants until a certain minimum and then increases again. The plot of log K(A) vs. 1/D is found to be non-linear indicating that the equation of association cannot be applied. The association constant is analysed using the solvent separated-ion pair model. read more

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S A EL SHAZLY ,N H EL HAMMAMY ,A I KAWANA ,F M ABD EL HALIM ,

RAPID METHOD FOR DIRECT DETERMINATION OF SOME PHENOTHIAZINE DRUGS USING THERMOMETRIC TITRIMETRY

A simple, rapid and accurate milligram method for the determination of chloropromazine hydrochloride (stemetil), promethazine hydrcohloride (Phenergan), and triflupromazine hydrochloride (Stelazine) in the presence of excipients is described. The reaction is made selective to react with N-bromosuccinimide and the heat of reaction is used to determine the end point of the titration. The method has been applied to pure and pharmaceutical formulation. A comparison of the results obtained by using this method and the U.S.P. methods shows no significant difference in the accuracy of the two techniques. The main advantages of the proposed method are less time taken, the potential for automation of the process and ability to carry out assay of single dosage form. read more

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M SIDDIQUI ,U M ABBASI ,M I BHANGER ,

ELECTROPHORETIC TECHNIQUE IN DETERMINATION OF STABILITY-CONSTANTS OF MIXED COMPLEXES (M-NTA-CYSTEINE)

The stability constants of different complex species of some metal ion viz. Hg(II), Be(II) and Ni(II) with cysteine were determined electrophoretically at an ionic strength of 0.1 M percholoric acid and 35-degrees-C. Beside binary complexes ternary complexes involving NTA and amino acid (Cysteine) have also been studied. For studying mixed ligand complexes the background electrolyte is made 1 x 10(-2)M with respect to NTA and its pH brought to 8.5. This pH is purposely chosen because amino acid and NTA form very stable complexes much a head of this pH. The stability constant of complexes M-NTA- Cysteine have been found to 5.06, 4.93 and 4.88 (log K values) for Hg(II), Be(II) and Ni(II) complexes respectively. read more

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R K P SINGH ,K L YADAVA ,B B TIWARI ,R CHANDER ,

SPECTROPHOTOMETRIC FLOW-INJECTION DETERMINATION OF NITRATE AND NITRITE IN POTABLE WATER USING 8-HYDROXYQUINOLINE

A method based on the principle of flow injection analysis is described for the determination of nitrate and nitrite. A minicolumn of copperized cadmium is used which reduces nitrate to nitrite, which in turn is diazotized with 4-aminobenzoic acid and 8-hydroxyquinoline. The resulting azo compound is quantified at 485 nm. The procedure is applied to potable water samples. The sampling rate for both species was 60 hr-1. The relative standard deviation was 0.8% for nitrite and 1.0% for nitrate. read more

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M A SIDDIQUI ,M YAQOOB ,M MASOOM ,

DETERMINATION OF STRONTIUM AND CERIUM IN AQUEOUS-SOLUTION BY X-RAY-FLUORESCENCE SPECTROMETRY

An analytical method for the determination of strontium and cerium in aqueous solution using X-ray fluorescence spectrometer has been developed, where samples were introduced to the XRF spectrometer directly in simple polyethylene bottles. Statistical evaluation helped to establish an analytical application of the method. Effect of various cations and anions on strontium and cerium intensity has been studied. Matrix effect due to these cations and anions have been rectified using standards of similar composition. read more

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J HANIF ,M AFZAL ,R QADEER ,M SALEEM ,