• Wahid U Malik

      Articles written in Proceedings – Section A

    • The problem of the composition and structure of potassium cyano-cobaltate (II)

      K M Abubacker Wahid U Malik

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      An approach to the problem of the composition and structure of potassium cyanocobaltate (II) has been made. The complex prepared by the interaction of Co(II) and KCN gave, on analysis, a compound with the formula K3Co(CN)4H2O (with about 0·1 M KCN adsorbed per mole). Potentiometric and amperometric titrations carried out between cobalt (II) nitrateand potassium cyanide gave support to the formation of a pentacyanocobaltate (II) but failed to give an insight into the structure of the complex. Polarographic studies, however, were found useful in deciding whether the complex is hexa- or penta-co-ordinated. The freshly prepared complex gave an anodic wave with E1/2−0·35 volt. This is due to pentacyanocobaltate (II), since the anodic wave is suppressed and finally eliminated by oxidising the compound with H2O2. The oxidised product was found to be irreversibly reduced at the dropping mercury electrode (d.m.e.) at a potential of −1·3 volts. That the product is hydroxopentacyano-cobaltate (III) could be seen by getting identical polarograms for the oxidised product and for a sample of the hydroxocompound. From these experiments it has been concluded that the original complex is a hexaco-ordinated compound with the formula K3[Co(CN)4.H2O] and it gets oxidised to K3[Co(CN)5OH] K3[Co(CN)5.OH] and finally to K3[Co(CN)4] on long standing or on boiling. It appears that either five cyanogen radicals are bound to the central atom and the co-ordination number six is maintained by co-ordinating with a water molecule, or a dimer through a water bridge as is formed.

    • Studies in the membrane permeability of cobalt (ii) and manganese (ii) ferrocyanides

      Wahid U Malik Fasih A Siddiqi

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      The permeability of a number of electrolytes through untreated and treated cobalt and manganese ferrocyanide membranes was studied employing constant flow method. The order of permeability was Cl > Br > NO3 > CNS > CH3 COO > SO4−− > FeCy6== for both type of membrane although the magnitude of the permeability values decreased with pretreated membranes on account of large electrostatic forces developing on the walls of the membranes due to the adsorption of ferrocyanide ions. The order of adsorbability of various ions by the respective gels as also of membrane potential was reverse to that for the permeability of ions. The relationship between permeability and membrane potential could be expressed in the form of the empirical relationshipy=ax1/n wherex andy represented permeability and potential respectively anda andn are constants. Permeability experiments carried out at different temperatures give the energy of activation for the process of diffusion to be 5,000 to 6,500 calories per mole, indicating that the energy barrier which the ions must exceed in passing through the membrane would be greater than for free diffusion.

    • Interaction of dyes with aluminium hydroxide sol

      Wahid U Malik Iqbal A Khan

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      The results on the variations in pH, viscosity and conductivity provide useful information about the possibility of chemical interaction between the dye and the colloidal micelle. In the case of alizarin sulphonic acid it appears that bigger aggregates, contributing to enhanced viscosity, are formed due to chemical interaction between the sol particles and the dye. The larger variations in the physical properties as compared to other dyes may be attributed to the existence of polymeric OL and OXO compounds in the alumina sol. The basic dyes appear only to stabilize the sol.

      Spectrophotometric studies on the binding of alizarin sulphonic acid and methyl orange to alumina sol can give an idea of the extent of binding of the dyes by the sol and the average values for number of moles of alumina bound per dye mole. These values are much bigger than obtained with arsenic sulphide and ferric oxide.

    • Studies on the sol-gel transformation of silicic acid sol in presence of dyes

      Wahid U Malik Iqbal A Khan

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      The influence of dyes on the gelation of silicic acid sol has been studied with the help of viscometric and pH metric methods. The results indicate that the time of gelation decreases in presence of basic dyes and increases with acid dyes. It has also been found that methylene blue is adsorbed by replacement of H+ ions by the big cation of the dye followed by a possible combination between S of the dye and OH of the silanol group of silicic acid. The results on pH variations during gelation support this viewpoint. Similar results have been obtained with malachite green. The interaction of alizarin sulphonic acid with silicid acid is explained in terms of compound formation between the silanol and the phenolic groups while methyl orange undergoes orientation to quinonoid structure in presence of silicic acid. Positive adsorption is found to take place in all cases except methyl orange which is negatively adsorbed.

    • Application of Hammett equation to arylazopyrazoles

      Wahid U Malik R N Goyal

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    • A report on polarography of nitro derivatives of arylazopyrazoles

      Wahid U Malik R N Goyal

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      In an earlier communication1 we reported our results on the effect of electron donating substituents on the polarographic reduction of 4-phenylazopyrazole. In this communication we report our results on the effect of an electron withdrawing substituent on the E1/2 of 1-thiocarbamoyl-3, 5-diphenyl-4-phenylazopyrazole. The studies were carried out in non-aqueous medium due to water insoluble nature of these compounds.

    • Interaction of potassium hexacyanoferrate (II) with histidine

      Ramesh Bembi Wahid U Malik

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      L-histidine substitutes cyano groups of K4Fe (CN)6 at pH 7·0 on irradiation with ultraviolet light. The reaction follows first order kinetics with reference to K4Fe(CN)6 and zero order with reference to histidine. The kinetic data shows the primary process to be aquation of Fe(CN)64− while the final product is formed through a rapid dark reaction of histidine with Fe(CN)4 (H2O)22− to give the product K2Fe(CN)2(histidine)2. The final product has been subjected to chemical and infrared spectral analysis.

    • Potentiometric determination of thermodynamic parameters for the complex formation of Arsenazo I and Spadns with ytterium(III), zirconium(IV) and cerium(IV)

      Wahid U Malik Ramesh Bembi R N Goyal R K Paliwal

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